tag:theconversation.com,2011:/nz/topics/rain-1378/articlesRain – The Conversation2024-03-20T21:24:09Ztag:theconversation.com,2011:article/2229412024-03-20T21:24:09Z2024-03-20T21:24:09ZWater woes in southern Alberta could spell disaster for aquatic ecosystems, and the people who rely on them<p>Freshwater will be an increasingly scarce resource as we head into spring and summer in Western Canada with implications for the livelihoods and economic prosperity of humans, and non-humans alike, in southern Alberta and the downstream Prairie provinces. </p>
<p>The Bow River — in addition to the Oldman and South-Saskatchewan sub-basins — play a vital role in Western Canada. These rivers also have <a href="https://albertawater.com/water-licences-transfers-and-allocation/">a large number of competing uses</a> including agricultural and irrigation needs, municipal uses, hydroelectric developments, industrial consumption and <a href="https://open.alberta.ca/publications/after-the-flood">recreational and cultural uses</a> — including a <a href="https://www.cbc.ca/news/canada/calgary/rainbow-trout-bow-river-1.4921565">world-class sports fishery</a>. </p>
<p>The Rocky Mountains serve as Western Canada’s water towers and are the critical source of the snowpack which plays a major role in <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/groundwater-recharge">groundwater recharge</a>. The <a href="https://doi.org/10.5194/hess-24-2731-2020">diminishing winter snowpack</a>, combined with increasing frequencies of <a href="https://agriculture.canada.ca/en/agricultural-production/weather/canadian-drought-monitor">multi-year droughts in the Prairies</a> from below-average regional precipitation, is setting up the summer of 2024 as another year of <a href="https://www.aer.ca/regulating-development/rules-and-directives/bulletins/bulletin-2023-43">abnormally low volumes</a> of water flowing through the basin.</p>
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<a href="https://theconversation.com/new-report-shows-alarming-changes-in-the-entire-global-water-cycle-197535">New report shows alarming changes in the entire global water cycle</a>
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<p>Make no mistake, dwindling flows will have wide reaching social, environmental and economic impacts. Governments and policymakers must act quickly to avert a larger crisis.</p>
<h2>Compounding impacts</h2>
<p>In addition to impacting the water available for human use, low flows and water levels have direct and indirect impacts on the <a href="https://trivent-publishing.eu/books/engineeringandindustry/watershedandriverbasinmanagement/11.%20C.%20W.%20Koning%20et%20al..pdf">organisms that live in and rely on the aquatic ecosystem</a>. Limited water supplies raise serious concerns about the <a href="https://www.canlii.org/en/commentary/doc/2006CanLIIDocs562#!fragment/zoupio-_Toc2Page1-Page10/BQCwhgziBcwMYgK4DsDWszIQewE4BUBTADwBdoAvbRABwEtsBaAfX2zgCYAFMAc0ICMjHvwEAGAJQAaZNlKEIARUSFcAT2gByTVIiEwuBMtUbtu-YZABlPKQBCGgEoBRADLOAagEEAcgGFnKVIwACNoUnYJCSA">long-term impacts on our aquatic ecosystems</a>.</p>
<p>Complicating matters is the <a href="https://open.alberta.ca/publications/albertas-water-priority-system-tools-for-water-licence-holders">“first in time, first in right” (FITFIR) water governance</a> principle which emerged out of the Western United States and is essentially a first come, first served system of water allocation. To make matters worse, <a href="https://doi.org/10.4296/cwrj3501079">new applications for water access have been closed since 2006</a>, a decision which will have a “significant effect on water supply strategies available to municipal water users, as many communities currently hold water licences that are not adequate for their projected growth.” </p>
<p>In <a href="https://open.alberta.ca/publications/0778546209">2006 the government of Alberta</a> acknowledged that “the limits for water allocations have been reached or exceeded in the Bow, Oldman and South Saskatchewan River sub basins.” In the South Saskatchewan Basin, most of the water is allocated to a handful of license holders who have had licenses for high volumes of water for years. This is a substantial hurdle to overcome when trying to retain river water for aquatic ecosystems — a goal <a href="https://cdnsciencepub.com/doi/10.1139/er-2022-0126">often referred to as environmental flows or “e-flows”</a>.</p>
<p>Without substantial changes to the licensing program, aquatic ecosystem health will continue to be secondary to existing license holder uses. </p>
<p>Further complicating the matter is that allocations are looked at <a href="https://static1.squarespace.com/static/62f582febb0b3104adabb617/t/6358b7a0bf6485031a91dc36/1666758567761/Final+Report+-+Review+of+the+Implementation+of+the+Approved+WMP+for+the+SSRB.pdf">annually and not seasonally</a>. This means that the system can’t adapt “on the fly” when low flows hit, unless there are specific government directives implemented to that effect. This is also true of current monitoring and reporting efforts across the country, with reporting and interpretation of data being done only after an <a href="https://edmontonjournal.com/business/energy/survey-finds-oilsands-environmental-monitoring-ineffective-after-10-years">issue has occurred, if at all</a>. </p>
<p>Perhaps most egregiously, the FITFIR approach has also long been criticized by Indigenous groups as disproportionately impacting their water rights and <a href="https://www.watercanada.net/feature/three-out-of-ten-odds-of-a-solution-to-first-nation-water-rights-in-alberta/">limiting water supplies in favour of competing industry and large agricultural needs</a>.</p>
<h2>Low-level impacts</h2>
<p>Alberta’s water regulations are generally not helping matters. Currently, regulations around pollution release are predominantly applied at the end-of-pipe, not throughout the river, meaning the impacts on the river will vary based on how much water is present. This often results <a href="https://doi.org/10.2166/wqrj.2019.033">in poor water quality events occurring in the summer,</a> when flow is lowest and the pollutants are less diluted. This has direct consequences on aquatic food webs and those that rely upon the river, especially in areas downstream of major sources of pollution.</p>
<p>Lower river flows and levels can result in <a href="https://doi.org/10.1016/j.earscirev.2014.11.010">increased water temperatures and</a> decreased oxygen availability for aquatic organisms. This can have harmful consequences on sensitive species like fish and their invertebrate food sources. The projected low flows in 2024 will likely lead to increased fish mortality.</p>
<p>There are numerous habitats around rivers that rely on certain levels of flow to be present for survival. Riparian areas (river banks) along the river run the risk of drying up and dying off if flow isn’t <a href="https://doi.org/10.1007/s13157-020-01392-4">adequate</a>. While seasonal fluctuations in water levels are normal, the <a href="https://www.cbc.ca/news/canada/edmonton/what-low-water-levels-in-edmonton-could-mean-for-fish-this-winter-1.7028203">uncharacteristically low flows this past fall and winter</a>, combined with expected lower water levels in the coming year may mean that these sensitive habitats are isolated for extended periods of time — not receiving the water and nutrients required for their survival.</p>
<p>The impacts aren’t restricted to organisms living directly in and around rivers in the region either. Low water flows affect the entire food web <a href="https://doi.org/10.1080/02705060.2023.2203728">from aquatic insects to apex predators</a> and with fewer prey available, larger fish populations may decline. These impacts also will only grow downstream as cumulative pressures on the river increase.</p>
<p>While rivers have seasonal flow patterns, low water flow isn’t just a seasonal issue. Climate change projections have been predicting more <a href="https://albertawater.com/climate-change-in-the-bow-basin/">frequent and severe droughts</a>, which will only exacerbate this issue.</p>
<h2>Preventing drought?</h2>
<p>2024 is likely the first of a series of years where we will see reduced snowpack, altered precipitation timing (and amounts) and increased water use pressures all combining to reduce river flows. </p>
<p>We have seen an initial reaction by <a href="https://www.alberta.ca/release.cfm?xID=8971229900128-9793-C959-193E503D6C61CAD4">the provincial government</a> in Alberta; however, there has been a noticeable lack of acknowledgement from many governments and regulatory bodies across the country. This is a national issue and will be an ongoing issue as a result of climate change. </p>
<p>The <a href="https://thetyee.ca/Analysis/2024/02/19/Alberta-Brutal-Water-Reckoning/">tension between different water users has been predicted for over a decade</a>. Policy options to date have been limited and have lacked the inclusion of ecosystem-related considerations. There <a href="https://www.theglobeandmail.com/business/article-parched-alberta-negotiating-with-water-holders-to-strike-share/">also has been discussion</a> around <a href="https://prism.ucalgary.ca/server/api/core/bitstreams/596932e4-12f8-46d6-90f6-7512479be965/content">increasing the allowance</a> of water which can be moved between basins. However, such systems could have major implications on <a href="https://doi.org/10.1002/eet.1891">aquatic ecosystem health if utilized widely and must be done with great care.</a></p>
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Read more:
<a href="https://theconversation.com/johannesburgs-water-crisis-is-getting-worse-expert-explains-why-the-taps-keep-running-dry-in-south-africas-biggest-city-223926">Johannesburg's water crisis is getting worse – expert explains why the taps keep running dry in South Africa's biggest city</a>
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<p>As we move through what will be an unprecedented low water year, it will be critical that policymakers, regulators and all Canadians understand the far-reaching impacts. </p>
<p>Our existing approaches aren’t working. We must look beyond our current systems. This includes utilizing the knowledge of water quality experts as well as Indigenous Peoples who have relied on the river for centuries. </p>
<p>The management issue presenting itself is extremely complex and <a href="http://dx.doi.org/10.1080/07900627.2016.1238345">will require equally complex responses with input from all concerned parties</a>. But the costs of failure will be far greater than the costs of action.</p><img src="https://counter.theconversation.com/content/222941/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Barrett receives funding from the Natural Sciences and Engineering Research Council (NSERC) of Canada and is involved in research projects in southern Alberta funded by the City of Calgary, Alberta Innovates, and the NSERC Alliance Program.</span></em></p><p class="fine-print"><em><span>Kerry Black receives funding from the Natural Sciences and Engineering Research Council, the Social Sciences and Humanities Research Council, and the Canadian Institutes of Health Research and is involved in research projects in southern Alberta funded by the City of Calgary, Alberta Innovates, and the NSERC Alliance Program.</span></em></p>Declining precipitation, climate change and governance failures will drive water flow scarcity in 2024 with serious implications across Western Canada.David Barrett, Research Associate, Faculty of Science, University of CalgaryKerry Black, Assistant Professor and Canada Research Chair, Integrated Knowledge, Engineering and Sustainable Communities, University of CalgaryLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2249022024-03-07T22:03:41Z2024-03-07T22:03:41ZFlood risk mapping is a public good, so why the public resistance in Canada? Lessons from Nova Scotia<p>Flood risk maps are an essential public good. Indeed, many countries like the <a href="https://flood-map-for-planning.service.gov.uk/">United Kingdom already offer flood risk mapping</a>.</p>
<p>Canada committed to a public flood risk mapping portal in the <a href="https://www.budget.canada.ca/2023/report-rapport/chap4-en.html#Raising%20Awareness%20of%20Flood%20Risks">2023 budget</a>. However, despite the <a href="https://www.theweathernetwork.com/en/news/climate/impacts/climate-water-is-the-new-fire">increasing frequency and impact of large, catastrophic floods</a>, we still have a sparse patchwork of flood risk maps at municipal and provincial scale. </p>
<p>What <a href="https://floodsmartcanada.ca/floodplain-maps/">flood mapping that does exist</a> is hard to find, of uncertain quality and currency, and often <a href="https://globalnews.ca/news/5206284/bad-flood-map-canada/">difficult for non-experts to understand and apply</a>. </p>
<p>The unacknowledged reason why there is a lack of flood risk mapping in Canada is because such maps generally face public resistance. Indeed, it is not uncommon in Canada to see flood or wetland mapping <a href="https://montreal.ctvnews.ca/quebec-withdraws-30-municipalities-from-contested-flood-zone-maps-1.4509236">withdrawn or modified</a> because of public pressure. </p>
<p>I led two survey-based studies recently with former graduate student Samantha Howard and post-doctoral fellow Brooke McWherter to understand how people in flood-prone areas of Nova Scotia perceive publicly available flood maps. We found wide agreement about the benefits of such maps — until we asked about the <a href="https://www.intactcentreclimateadaptation.ca/treading-water-impact-of-catastrophic-flooding-on-canadas-housing-market/">impact on real estate value</a>. </p>
<h2>The case of Nova Scotia</h2>
<p>Nova Scotia faces some of the <a href="https://changingclimate.ca/CCCR2019/chapter/8-0/">highest sea level rise in Canada</a> under current climate change projections. Yet last week, the Nova Scotia government <a href="https://www.cbc.ca/news/canada/nova-scotia/coastal-protection-act-environment-tim-halman-climate-change-1.7125745">decided not to proceed with the long-awaited Coastal Protection Act (CPA)</a>, which had been passed with all-party assent in 2019. </p>
<p>Among other things, the act would have regulated how close people could build to the ocean based on assessments of sea level, storm projections and information about the elevation and erosion risk of each section of coast. This would have protected people and infrastructure, as well as sensitive coastal ecosystems, and left space for ocean dynamics. </p>
<p>In lieu of the act, the Nova Scotia government released a <a href="https://novascotia.ca/coastal-climate-change/">new website</a> featuring resources to help individual coastal property owners make decisions about their bit of coastline, <a href="https://www.cbc.ca/news/canada/nova-scotia/municipalities-nova-scotia-coastal-protection-act-1.7021006">leaving dozens of rural coastal municipalities</a> in the lurch. One of those resources was a new <a href="https://nsgi.novascotia.ca/chm">coastal hazard map</a>. </p>
<p>The lengthy disclaimer you need to agree to before you can access the map immediately erodes its trustworthiness. Moreover, while people may trust any good news they see in its data, they may still be at risk due to the tool’s many data and design flaws. To supplement this tool, Nova Scotia has <a href="https://globalnews.ca/news/10317417/new-coastal-protection-plan-nova-scotia/">committed to finishing detailed flood line mapping by 2027</a>. </p>
<p>It is too soon to know how people are responding to this tool, but we know it does not take a lot of unhappy constituents to make a government nervous, especially if those constituents hold financial or political power. <a href="https://www.cbc.ca/news/canada/nova-scotia/coastal-protection-act-tim-halman-environment-climate-change-1.6959599">The public engagement associated with the CPA was, after all, overwhelmingly in support of proclaiming and regulating under the act</a>. Yet here we are. </p>
<h2>Drivers of resistance</h2>
<p>The first survey we ran in 2021 — through an online link sent via Canada Post to all residents in two towns in Southwestern Nova Scotia — showed <a href="https://doi.org/10.1111/cag.12836">one in six people felt flood risk mapping presented too big a risk for real estate value</a>. Our second survey of about 1100 house residents around the Minas Basin, Nova Scotia, in 2022 found that <a href="http://hdl.handle.net/10222/83004">one in three residents expressed concern about real estate value</a>. Both studies had a margin of error of plus or minus 6 per cent at a 95 per cent confidence level.</p>
<p>The first survey had a smaller response rate but represented the population demographics better. The second was biased toward older respondents and those with higher incomes. </p>
<p>Moving back to our original question — why doesn’t everyone see flood risk mapping as a public good?</p>
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<a href="https://theconversation.com/2023s-billion-dollar-disasters-list-shattered-the-us-record-with-28-big-weather-and-climate-disasters-amid-earths-hottest-year-on-record-220634">2023's billion-dollar disasters list shattered the US record with 28 big weather and climate disasters amid Earth's hottest year on record</a>
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<p>We used slightly different questions in the two studies to understand the drivers of resistance to flood risk mapping based on perceived impact on real estate value. What emerged speaks to the challenge of inspiring long-term and collective thinking about climate change. </p>
<p>Firstly, being focused on oneself rather than others was a reliable predictor of resistance in both studies. </p>
<p>Resistance in the first study was associated with agreeing to the following statements: “I am not able to cope with the land changes required to deal with significant increases in flood risk at this point in my life,” and “flood management decisions I make do not have implications for others.” The latter is demonstrably untrue: shoreline armouring, for instance, can have negative effects for neighbours. In the second study, being focused on others and having descendants led to less resistance. </p>
<p>Self-orientation was a strong underlying driver of resistance. It reduced a person’s likelihood of focusing on others, the future or the biosphere. People already make decisions to suit their own situation, just as the Nova Scotia government is now <a href="https://www.halifaxexaminer.ca/morning-file/the-houston-government-thinks-we-can-use-an-app-to-ward-off-storm-damage-and-sea-level-rise-individually-we-cant/#N1">encouraging coastal landowners to do</a>. Yet in these kinds of scenarios, collective and ecological interests are forgotten.</p>
<p>Secondly, the more vulnerable a person felt to flood risk, the more likely they were to oppose maps that would allow others to see their flood risk. This variable was only a strong signal of resistance in the second study when we used a combination of flood likelihood and vulnerability to measure it. This might also explain why resistance was twice as high in the 2022 survey than the one in 2021. It could be a regional difference based on actual differences in risk, or differences in survey method and thus respondent population, but it could also reflect increasing flood frequency and severity.</p>
<p>The second survey was still in the field when <a href="https://www.cbc.ca/news/canada/nova-scotia/weather-snoddon-fiona-recap-1.6976249">Hurricane Fiona</a> hit Atlantic Canada. This timing suggests that instead of becoming more open to climate adaptation information like flood maps as flooding events occur, we might become less open as we seek to protect the value of our biggest investments: our homes. </p>
<h2>Moving forward</h2>
<p>A clue to the path ahead may be found in our first study, where <a href="https://doi.org/10.1111/cag.12836">those who had previously seen a flood map for their region</a> were slightly less likely to be resistant to public flood risk maps. This might indicate that such resistance is mostly borne of fear of the unknown. </p>
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Read more:
<a href="https://theconversation.com/wetlands-are-superheroes-expert-sets-out-how-they-protect-people-and-places-221995">Wetlands are superheroes: expert sets out how they protect people and places</a>
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<p>We urgently need high quality, public flood risk maps that the government stands by (including with planning regulations). Then we can focus on rethinking what it means to live a good coastal life in the face of climate change, and how we collectively support those who may face decreases in home or land value.</p><img src="https://counter.theconversation.com/content/224902/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kate Sherren or her trainees received funding for this work from the Social Sciences and Humanities Research Council, the Natural Sciences and Engineering Research Council, and the Nova Scotia Government. </span></em></p>Public concerns for real estate value, and a focus on the self, make flood risk maps unpopular. However, these concerns should not dissuade governments from providing resources we can all trust.Kate Sherren, Professor, School for Resource and Environmental Studies, Dalhousie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2219562024-01-25T13:17:10Z2024-01-25T13:17:10ZDiagnosing ‘warming winter syndrome’ as summerlike heat sweeps into central and eastern US<figure><img src="https://images.theconversation.com/files/578072/original/file-20240226-22-sj8mc9.jpg?ixlib=rb-1.1.0&rect=0%2C43%2C7333%2C4830&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Chicago topped 70 degrees on Feb. 26, 2024. That's not normal.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/WarmWeatherChicago/e74246d1976f4048a494c6cb1ce2c0dd/photo">AP Photo/Charles Rex Arbogast</a></span></figcaption></figure><p>One of the most robust measures of Earth’s changing climate is that winter is warming more quickly than other seasons. The cascade of changes it brings, including ice storms and rain in regions that were once reliably below freezing, are symptoms of what I call “warming winter syndrome.”</p>
<p>Wintertime warming represents the global accumulation of heat. During winter, direct heat from the Sun is weak, but storms and <a href="https://theconversation.com/extreme-cold-still-happens-in-a-warming-world-in-fact-climate-instability-may-be-disrupting-the-polar-vortex-221276">shifts in the jet stream bring warm air</a> up from more southern latitudes into the northern U.S. and Canada. As <a href="https://climate.copernicus.eu/copernicus-2023-hottest-year-record">global temperatures</a> and <a href="https://climatereanalyzer.org/clim/sst_daily/">the oceans warm</a>, that stored heat has an influence on both temperature and precipitation. </p>
<p>The U.S. has been feeling this warming in the winter of 2023-24, the <a href="https://www.ncei.noaa.gov/news/national-climate-202402">warmest on record</a> for the Lower 48 states. </p>
<p>Snowfall has been <a href="https://twitter.com/NWSEastern/status/1757548891602358455">below average</a> in much of the country. On the Great Lakes, the ice cover has been at <a href="https://www.climate.gov/news-features/event-tracker/ice-coverage-nearly-nonexistent-across-great-lakes-historical-peak">record lows</a>. Late February saw a wave of <a href="https://twitter.com/NWS/status/1762158623793233989">summerlike temperatures</a> spread up into the central and eastern U.S., along with <a href="https://www.accuweather.com/en/severe-weather/severe-storms-with-nocturnal-tornado-risk-to-blitz-over-a-dozen-states/1625378">dangerous thunderstorms</a> and wildfires, including <a href="https://theconversation.com/texas-fires-with-over-1-million-acres-of-grassland-burned-cattle-ranchers-face-struggles-ahead-to-find-and-feed-their-herds-224840">Texas’ largest on record</a>. And forecasters expected <a href="https://graphical.weather.gov/sectors/conusLoop.php#tabs">another above-average warm spell in early March</a>.</p>
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<img alt="" src="https://images.theconversation.com/files/571278/original/file-20240124-21-v3590w.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/571278/original/file-20240124-21-v3590w.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/571278/original/file-20240124-21-v3590w.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/571278/original/file-20240124-21-v3590w.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/571278/original/file-20240124-21-v3590w.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/571278/original/file-20240124-21-v3590w.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/571278/original/file-20240124-21-v3590w.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The average lowest annual temperature, which affects where certain plants can grow, has shifted over the past half-century, reflecting the changing freezing line across the U.S.</span>
<span class="attribution"><a class="source" href="https://www.climatecentral.org/climate-matters/shifting-planting-zones-2023">Climate Central</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>The longer warming trend is evident in changes to growing seasons, reflected in recent updates to plant hardiness zones printed on the <a href="https://planthardiness.ars.usda.gov/">back of seed packages</a>. These maps show the northward and, sometimes, westward movement of freezing temperatures in eastern North America. </p>
<h2>Ice storms and wet snow</h2>
<p>I <a href="https://scholar.google.com/citations?user=viGxwOwAAAAJ&hl=en">study the impact of global warming</a> and have documented changes to the climate and weather over the decades.</p>
<p>On average, <a href="https://nca2023.globalchange.gov/chapter/2/">freezing temperatures are moving</a> northward and, along the Atlantic coast, toward the interior of the continent. For individual storms, the transition to freezing temperatures even in the dead of winter can now be as far north as Lake Superior and southern Canada in places where, 50 years ago, it was reliably below freezing from early December through February.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/571354/original/file-20240125-23-x46q84.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two bar charts and a bell curve show the shifting average temperatures to more Januaries above freezing in recent decades." src="https://images.theconversation.com/files/571354/original/file-20240125-23-x46q84.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/571354/original/file-20240125-23-x46q84.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=290&fit=crop&dpr=1 600w, https://images.theconversation.com/files/571354/original/file-20240125-23-x46q84.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=290&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/571354/original/file-20240125-23-x46q84.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=290&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/571354/original/file-20240125-23-x46q84.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=365&fit=crop&dpr=1 754w, https://images.theconversation.com/files/571354/original/file-20240125-23-x46q84.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=365&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/571354/original/file-20240125-23-x46q84.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=365&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In northwest Wisconsin, along Lake Superior, there were no Januarys in the 1951-1980 time frame in which the average high temperature was even close to exceeded freezing. That has changed in recent years.</span>
<span class="attribution"><a class="source" href="https://www.ncei.noaa.gov/access/monitoring/dyk/us-climate-divisions#grdd_">Omar Gates/GLISA</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>When temperatures are close to the freezing point, water can be rain, snow or ice. Regions on the colder side, which historically would have been below freezing and snowy, are seeing an <a href="https://glisa.umich.edu/freezing-rain/">increase in ice storms</a>. </p>
<p>The character of snow also changes near the freezing line. When the temperature is well below freezing, the snow is dry and fluffy. Near freezing, snow has big, wet, heavy flakes that turn roads into slush and stick on tree branches and bring down power lines.</p>
<p>Because the climate in which snowstorms are forming is warmer due to global accumulation of heat, and wetter because of more evaporation and warmer air that can hold more moisture, individual snowstorms can also result in <a href="https://www.washingtonpost.com/weather/2019/11/26/with-climate-change-washington-may-have-entered-era-more-blockbuster-snowstorms-less-snow-overall/">more intense snowfalls</a>. However, as temperatures get warmer in the future, the scales will tilt toward rain, and the <a href="https://glisa.umich.edu/resources-tools/climate-impacts/lake-effect-snow-in-the-great-lakes-region/">total amount of snow</a> will decrease.</p>
<p><iframe id="mRX0t" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/mRX0t/1/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Indeed, on the warmer side of the freezing line, winter rain is already <a href="https://glisa.umich.edu/resources-tools/climate-impacts/lake-effect-snow-in-the-great-lakes-region/">becoming the dominate type of precipitation</a>, a trend that is expected to continue. With the warmer oceans as a major source of moisture, the already wet eastern U.S. can expect <a href="https://nca2023.globalchange.gov/chapter/2/">more winter precipitation over the next 30 years</a>. Looking to the future, soggy wet winters are more likely.</p>
<h2>Disaster and water planning gets harder</h2>
<p>For communities, planning for water supplies and extreme weather gets more complicated in a rapidly changing climate. Planners can’t count on the weather 30 years in the future being the same as weather today. It’s changing too quickly.</p>
<p>In many places, snow will not persist as late into spring. In regions like California and the Rockies that rely on the snowpack for water through the year, those supplies will <a href="https://nca2023.globalchange.gov/chapter/front-matter/">become less reliable</a>.</p>
<p>Rain falling on snowpack can also speed up melting, trigger flooding and change the flows of creeks and rivers. This shows up in changing <a href="https://theconversation.com/climate-change-is-driving-rapid-shifts-between-high-and-low-water-levels-on-the-great-lakes-118095">runoff patterns in the Great Lakes</a>, and it led to <a href="https://weather.com/news/weather/video/rain-melting-snow-tidal-water-bring-flooding-to-east-coast">flooding on the East Coast</a> in January 2024.</p>
<p>For road planners, the rate of freeze-thaw cycles that can damage roads will increase during winters in many regions unaccustomed to such quick shifts.</p>
<figure class="align-center ">
<img alt="A satellite image shows open water on the western shores the Great Lakes and storms forming to dump snow on the eastern shores." src="https://images.theconversation.com/files/571288/original/file-20240124-29-okndmd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/571288/original/file-20240124-29-okndmd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=577&fit=crop&dpr=1 600w, https://images.theconversation.com/files/571288/original/file-20240124-29-okndmd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=577&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/571288/original/file-20240124-29-okndmd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=577&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/571288/original/file-20240124-29-okndmd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=725&fit=crop&dpr=1 754w, https://images.theconversation.com/files/571288/original/file-20240124-29-okndmd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=725&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/571288/original/file-20240124-29-okndmd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=725&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A lake-effect snowstorm in 2020 shows how cold, dry air passing over the Great Lakes picks up moisture and heat, becoming snow on the other side.</span>
<span class="attribution"><a class="source" href="https://en.m.wikipedia.org/wiki/File:Lake_Effect_Snow_on_Earth.jpg">NASA</a></span>
</figcaption>
</figure>
<p>An especially interesting effect happens in the Great Lakes. Already, the <a href="https://research.noaa.gov/2024/01/18/why-low-ice-coverage-on-the-great-lakes-matters/">Great Lakes do not freeze as early</a> or as completely as in the past. This has large effects on the famous lake-effect precipitation zones.</p>
<p>With the lakes not frozen, more water evaporates into the atmosphere. In places where the wintertime air temperature is still below freezing, <a href="https://glisa.umich.edu/resources-tools/climate-impacts/lake-effect-snow-in-the-great-lakes-region/">lake-effect snow is increasing</a>. The Buffalo, New York, region saw <a href="https://theconversation.com/what-causes-lake-effect-snow-like-buffalos-extreme-storms-194953">6 feet of snow</a> from one lake-effect storm in 2022. As the air temperature flirts with the freezing line, these events are more likely to be rain and ice than snow.</p>
<p>These changes <a href="https://theconversation.com/extreme-cold-still-happens-in-a-warming-world-in-fact-climate-instability-may-be-disrupting-the-polar-vortex-221276">don’t mean cold is gone for good</a>. There will be occasions when Arctic air dips down into the U.S. This <a href="https://www.wilx.com/2024/01/24/fog-rain-wednesday-todays-headlines/">can cause flash freezing</a> and fog when warm wet air surges back over the frozen surface.</p>
<h2>Enormous consequences for economies</h2>
<p>What we are experiencing in warming winter syndrome is a consistent and robust set of symptoms on a fevered planet. </p>
<p>Novembers and Decembers will be milder; Februarys and Marches will be more like spring. Wintry weather will become more concentrated around January. There will be unfamiliar variability with snow, ice and rain. Some people may say these changes are great; there is less snow to shovel and heating bills are down.</p>
<figure class="align-center ">
<img alt="People walk with umbrellas in freezing rain in New York in January 2024." src="https://images.theconversation.com/files/571457/original/file-20240125-21-uuw03m.jpeg?ixlib=rb-1.1.0&rect=0%2C2%2C1917%2C1270&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/571457/original/file-20240125-21-uuw03m.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/571457/original/file-20240125-21-uuw03m.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/571457/original/file-20240125-21-uuw03m.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/571457/original/file-20240125-21-uuw03m.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/571457/original/file-20240125-21-uuw03m.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/571457/original/file-20240125-21-uuw03m.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rain or snow? As global temperatures rise, cities accustomed to snowy winters will see more rain and ice storms during the winter months.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/people-walk-through-light-snow-in-manhattan-as-new-york-news-photo/1945522082">Spencer Platt/Getty Images</a></span>
</figcaption>
</figure>
<p>But on the other side, <a href="https://www.freep.com/in-depth/news/local/michigan/2021/01/03/michigan-winter-festivals-climate-change/3954384001/">whole economies are set up for wintertime</a>, many <a href="https://www.climatehubs.usda.gov/sites/default/files/Chill%20Hours%20Ag%20FS%20_%20120620.pdf">crops rely on cool winter temperatures</a>, and many farmers rely on freezing weather to control pests. Anytime there are changes to temperature and water, the <a href="https://www.wbez.org/stories/less-ice-on-the-great-lakes-due-to-warmer-winters/af180e73-78ac-4c64-acd5-d7118c46f89c">conditions in which plants and animals thrive are altered</a>. </p>
<p>These changes, which affect <a href="https://theconversation.com/how-climate-change-threatens-the-winter-olympics-future-even-snowmaking-has-limits-for-saving-the-games-177040">outdoor sports and recreation</a>, <a href="https://glisa.umich.edu/resources-tools/climate-impacts/fish-wildlife/">commercial fisheries</a> and agriculture, <a href="https://nca2023.globalchange.gov/chapter/11">have enormous consequences</a> not only to the ecosystems but also to our relationship to them. In some instances, traditions will be lost, such as ice fishing. Overall, people just about everywhere will have to adapt.</p>
<p><em>This article, originally published Jan. 25, 2024, has been updated with above-average heat across much of the central and eastern U.S. in late February and forecast in early March.</em></p><img src="https://counter.theconversation.com/content/221956/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard B. (Ricky) Rood receives funding from the National Oceanographic and Atmospheric Administration (NOAA).</span></em></p>As the climate changes and weather warms, the freezing line is shifting, bringing rain to many regions more accustomed to snow.Richard B. (Ricky) Rood, Professor Emeritus of Climate and Space Sciences and Engineering, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2202842024-01-18T01:00:18Z2024-01-18T01:00:18ZStickers and wristbands aren’t a reliable way to prevent mosquito bites. Here’s why<figure><img src="https://images.theconversation.com/files/569681/original/file-20240116-25-fkx3sy.jpg?ixlib=rb-1.1.0&rect=220%2C137%2C3918%2C3235&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/2-boys-standing-on-green-grass-near-lake-during-daytime-pwCJWny66aI">Meritt Thomas/Unsplash</a></span></figcaption></figure><p>Protecting yourself and family from mosquito bites can be challenging, especially in this hot and humid weather. Protests from young children and fears about topical insect repellents drive some to try alternatives such as wristbands, patches and stickers. </p>
<p>These products are sold online as well as in supermarkets, pharmacies and camping stores. They’re often marketed as providing “natural” protection from mosquitoes.</p>
<p>But unfortunately, they aren’t a reliable way to prevent mosquito bites. Here’s why – and what you can try instead. </p>
<h2>Why is preventing mosquito bites important?</h2>
<p>Mosquitoes can <a href="https://theconversation.com/how-can-the-bite-of-a-backyard-mozzie-in-australia-make-you-sick-171601">spread pathogens that make us sick</a>. <a href="https://theconversation.com/japanese-encephalitis-virus-has-been-detected-in-australian-pigs-can-mozzies-now-spread-it-to-humans-178017">Japanese encephalitis</a> and <a href="https://theconversation.com/murray-valley-encephalitis-has-been-detected-in-mozzies-in-nsw-and-victoria-heres-what-you-need-to-know-197894">Murray Valley encephalitis</a> viruses can have potentially fatal outcomes. While <a href="https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1005070">Ross River</a> virus won’t kill you, it can cause potentially debilitating illnesses. </p>
<p>Health authorities <a href="https://www.health.nsw.gov.au/Infectious/mosquito-borne/Pages/default.aspx">recommend</a> preventing mosquito bites by: avoiding areas and times of the day when mosquitoes are most active; covering up with long sleeved shirts, long pants, and covered shoes; and applying a topical insect repellent (a cream, lotion, or spray).</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/will-japanese-encephalitis-return-this-summer-what-about-other-diseases-mosquitoes-spread-218441">Will Japanese encephalitis return this summer? What about other diseases mosquitoes spread?</a>
</strong>
</em>
</p>
<hr>
<h2>I don’t want to put sticky and smelly repellents on my skin!</h2>
<p>While for many people, the “sting” of a <a href="https://www.sciencedirect.com/science/article/pii/S1326020023023567?via%3Dihub">biting mosquitoes is enough to prompt a dose of repellent</a>, others are <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10739303/">reluctant</a>. Some <a href="https://www.liebertpub.com/doi/10.1089/153036603322662156">are deterred</a> by the unpleasant feel or smell of insect repellents. Others believe topical repellents contain chemicals that are dangerous to our health.</p>
<p>However, many studies have shown that, when used as recommended, these products <a href="https://www.sciencedirect.com/science/article/abs/pii/S1080603215004342">are safe to use</a>. All products marketed as mosquito repellents in Australia must be registered by the <a href="https://www.apvma.gov.au/">Australian Pesticides and Veterinary Medicines Authority</a>; a process that provides recommendations for safe use. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/feel-like-youre-a-mozzie-magnet-its-true-mosquitoes-prefer-to-bite-some-people-over-others-128788">Feel like you're a mozzie magnet? It's true – mosquitoes prefer to bite some people over others</a>
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</em>
</p>
<hr>
<h2>How do topical repellents work?</h2>
<p>While there remains some uncertainty about how the <a href="https://www.jaad.org/article/S0190-9622(18)32824-X/fulltext">chemicals in topical insect repellents actually work</a>, they appear to either block the sensory organs of mosquitoes that drive them to bite, or overpower the smells of our skin that helps mosquitoes find us. </p>
<p>Diethytolumide (DEET) is a <a href="https://www.phrp.com.au/issues/december-2016-volume-26-issue-5/a-review-of-recommendations-on-the-safe-and-effective-use-of-topical-mosquito-repellents/">widely recommended ingredient</a> in topical repellents. Picaridin and oil of lemon eucalyptus <a href="https://www.phrp.com.au/issues/december-2016-volume-26-issue-5/a-review-of-recommendations-on-the-safe-and-effective-use-of-topical-mosquito-repellents/">are also used</a> and have been shown to be effective and safe.</p>
<h2>How do other products work?</h2>
<p>“Physical” insect-repelling products, such as wristbands, coils and candles, often contain a botanically derived chemical and are often marketed as being an alternative to DEET.</p>
<p>However, studies have shown that devices such as candles <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-3156.2011.02781.x">containing citronella oil</a> provide lower mosquito-bite prevention than topical repellents.</p>
<p>A <a href="https://search.informit.org/doi/abs/10.3316/INFORMIT.227605874334644?casa_token=DEdfTcUX-F0AAAAA%3AwKeVbAzCxFZX2BZj2VvHBqI3Vjv1oKngFHgMteebxGtZVfN5bezrWRbNnBHyoyKViaEG_908OOwCAC4">laboratory study in 2011</a> found wristbands infused with peppermint oil failed to provide full protection from mosquito bites.</p>
<p>Even as topical repellent formulations applied to the skin, these botanically derived products have <a href="https://bioone.org/journals/Journal-of-the-American-Mosquito-Control-Association/volume-25/issue-3/09-0016.1/Are-Commercially-Available-Essential-Oils-from-Australian-Native-Plants-Repellent/10.2987/09-0016.1.short">lower mosquito bite protection</a> than recommended products such as those containing <a href="https://www.phrp.com.au/issues/december-2016-volume-26-issue-5/a-review-of-recommendations-on-the-safe-and-effective-use-of-topical-mosquito-repellents/">DEET, picaridin and oil of lemon eucalyptus</a>.</p>
<p>Wristbands infused with DEET have shown mixed results but may provide some <a href="https://link.springer.com/article/10.1007/s00436-009-1433-x">bite protection</a> or <a href="https://resjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-2915.1987.tb00331.x">bite reduction</a>. DEET-based wristbands or patches are not currently available in Australia.</p>
<p>There is also a range of mosquito repellent <a href="https://theconversation.com/are-mosquito-coils-good-or-bad-for-our-health-88548">coils, sticks, and other devices</a> that release insecticides (for example, pyrethroids). These chemicals are primarily designed to kill or “knock down” mosquitoes rather than to simply keep them from biting us.</p>
<h2>What about stickers and patches?</h2>
<p>Although insect repellent patches and stickers have been available for many years, there has been a sudden surge in their marketing through social media. But there are very few scientific studies testing their efficacy.</p>
<p>Our current understanding of the way insect repellents work would suggest these small stickers and patches offer little protection from mosquito bites.</p>
<p>At best, they may <a href="https://bioone.org/journals/Journal-of-the-American-Mosquito-Control-Association/volume-22/issue-1/8756-971X(2006)22%5B158:FEONMS%5D2.0.CO;2/FIELD-EVALUATION-OF-NEW-MOUNTAIN-SANDALWOOD-MOSQUITO-STICKSsup-supAND-NEW/10.2987/8756-971X(2006)22%5B158:FEONMS%5D2.0.CO;2.short">reduce some bites</a> in the way mosquito coils containing botanical products work. However, the passive release of chemicals from the patches and stickers is likely to be substantially lower than those from mosquito coils and <a href="https://academic.oup.com/jme/article-abstract/53/2/480/2459702?login=false">other devices actively releasing chemicals</a>.</p>
<p>One <a href="https://doi.org/10.1016/j.actatropica.2012.10.009">study in 2013</a> found a sticker infused with oil of lemon eucalyptus “did not provide significant protection to volunteers”.</p>
<p><a href="https://theconversation.com/mozzie-repellent-clothing-might-stop-some-bites-but-youll-still-need-a-cream-or-spray-107266">Clothing impregnated with insecticides</a>, such as permethrin, will assist in reducing mosquito bites but topical insect repellents are still recommended for exposed areas of skin.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/bzzz-slap-how-to-treat-insect-bites-home-remedies-included-148722">Bzzz, slap! How to treat insect bites (home remedies included)</a>
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<h2>Take care when using these products</h2>
<p>The idea you can apply a sticker or patch to your clothing to protect you from mosquito bites may sound appealing, but these devices provide a false sense of security. There is no evidence they are an equally effective alternative to the topical repellents recommended by health authorities around the world. It <a href="https://theconversation.com/curious-kids-when-we-get-bitten-by-a-mosquito-why-does-it-itch-so-much-93347">only takes one bite</a> from a mosquito to transmit the pathogens that result in serious disease.</p>
<p>It is also worth noting that there are some health warnings and recommendations for their use <a href="https://www.apvma.gov.au/">required by Australian Pesticides and Veterinary Medicines Authority</a>. Some of these products warn against application to the skin (recommending application to clothing only) and to keep products “out of reach of children”. This is a challenge if attached to young children’s clothing.</p>
<p>Similar warnings are associated with most other topical and non-topical mosquito repellents. Always check the labels of these products for safe use recommendations.</p>
<h2>Are there any other practical alternatives?</h2>
<p>Topical insect repellents are safe and effective. Most can be used on children from 12 months of age and pose no health risks. Make sure you apply the repellent as a thin even coat on all exposed areas of skin. </p>
<p>But you don’t need “tropical strength” repellents for short periods of time outdoors; a range of formulations with lower concentrations of repellent will work well for shorter trips outdoors. There are some repellents that don’t smell as strong (for example, children’s formulations, odourless formulations) or formulations that may be more pleasant to use (for example, pump pack sprays).</p>
<p>Finally, you can always cover up. Loose-fitting long-sleeved shirts, long pants, and covered shoes will provide a physical barrier between you and mosquitoes on the hunt for your or your family’s blood this summer.</p><img src="https://counter.theconversation.com/content/220284/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Webb and the Department of Medical Entomology, NSW Health Pathology, have been engaged by a wide range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on mosquito biology. Cameron has also received funding from local, state and federal agencies to undertake research into mosquito-borne disease surveillance and management.</span></em></p>It’s hot and humid. With mosquitoes about, applying insect repellent creams, sprays and lotions may not feel good. But how do the alternatives stack up?Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2210042024-01-17T02:38:02Z2024-01-17T02:38:02ZUp to 5 billion people to be hit by rainfall changes this century if CO₂ emissions are not curbed, research shows<p>Three to five billion people – or up to two-thirds of the world’s population – are set to be affected by projected rainfall changes by the end of the century unless the world rapidly ramps up emissions reduction efforts, according to <a href="https://www.nature.com/articles/s41467-023-44513-3">new research</a> by myself and colleagues.</p>
<p>To date, the effects of climate change on global rainfall has been <a href="https://www.carbonbrief.org/explainer-what-climate-models-tell-us-about-future-rainfall/">uncertain</a>. This has hampered our capacity to adapt to climate change and prepare for natural disasters.</p>
<p>Our method overcomes this uncertainty. We identified the regions where multiple climate models make similar projections about future rainfall impacts, and so reveal the global hot spots for drier and wetter conditions in future. </p>
<p>Our findings have deep implications for a large proportion of the world’s population – including millions of Australians.</p>
<figure class="align-center ">
<img alt="girl in pink dress plays in muddy puddle" src="https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Up to five billion people, including millions of Australians, are set to be affected by rainfall changes by 2100 under climate change.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Navigating the uncertainty of rain projections</h2>
<p>Climate models are one of the main ways scientists understand how the climate behaved in the past and might change in future. They <a href="https://theconversation.com/yes-a-few-climate-models-give-unexpected-predictions-but-the-technology-remains-a-powerful-tool-165611">comprise</a> millions of lines of computer code and use mathematical equations to <a href="https://www.climate.gov/maps-data/climate-data-primer/predicting-climate/climate-models">represent</a> how energy and materials move through the ocean, atmosphere and land. For future projections, climate models are driven by <a href="https://www.carbonbrief.org/explainer-how-shared-socioeconomic-pathways-explore-future-climate-change/">emissions scenarios</a> representing various possible emissions trajectories.</p>
<p>Using climate models to simulate future rainfall patterns is a difficult task. Rain is influenced by complex factors, such as radiative balance (how much of the Sun’s energy is coming in versus how much is leaving), as well as climate drivers linked to specific sea surface temperature patterns, such as El Niño and La Niña. This means different climate models often produce different rainfall projections, especially at a regional level.</p>
<p>We wanted to investigate the extent to which climate models “agree”, or produce similar projections, about how CO₂ emissions may affect future rainfall around the globe.</p>
<p>There are several ways to do this. The usual method is to average out data collected over time – say, two decades. But this approach can eliminate important information and obscure vital insights into how rainfall will behave in future.</p>
<p>We used an innovative and more comprehensive approach based on “time-series” data, or data collected at regular intervals over time – comprising historical and future projections from 1980 to 2100. This approach accounts for continual changes over time, both in the recent past and out to the end of this century.</p>
<p>We analysed both the <a href="https://wcrp-cmip.org/cmip-phase-6-cmip6/">current</a> and <a href="https://wcrp-cmip.org/cmip-phase-5-cmip5/">previous</a> generations of climate models – 146 in all.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/yes-a-few-climate-models-give-unexpected-predictions-but-the-technology-remains-a-powerful-tool-165611">Yes, a few climate models give unexpected predictions – but the technology remains a powerful tool</a>
</strong>
</em>
</p>
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<h2>The global hotspots</h2>
<p>Our analysis showed several countries facing drier conditions in future. The top five most affected were Greece, Spain, Palestine, Portugal and Morocco, where at least 85% of models projected significantly reduced annual rainfall by the end of this century, under a worst-case scenario of very high emissions.</p>
<p>In contrast, for Finland, North Korea, Russia, Canada and Norway, more than 90% of models agreed on a trend towards increasing annual rainfall.</p>
<p>The picture was similar for most parts of the highly populated nations of China and India, which are together home to more than 2.7 billion people. In those nations, 70% of models agreed on projections for increasing rainfall.</p>
<p>Our analysis showed some European countries, including the United Kingdom, Germany and France, were generally projected to experience less rainfall in summer and more in winter. These increases and decreases offset each other, which means no change in total rainfall, but substantial changes in seasonal distributions over the year.</p>
<p>Using our approach, rainfall projections remained unclear for some parts of the world. These include most of Australia, as well as central Europe, southwest Asia and parts of the African west coast and South America. </p>
<p>All up, the regions getting wetter or drier under global warming cover a vast proportion of the globe. Under scenarios where emissions remain intermediate (where emissions decline to about half of 2050 levels by the end of the century), 38% of the current world’s population, or three billion people, would be affected by changes in rainfall.</p>
<p>If we experience very high emissions instead, 66% of the world’s population – or five billion people – would be affected. Many of these regions are already experiencing the <a href="https://theconversation.com/how-climate-change-intensifies-the-water-cycle-fueling-extreme-rainfall-and-flooding-the-northeast-deluge-was-just-the-latest-209476">wetting</a> and <a href="https://theconversation.com/drought-in-the-amazon-understanding-the-causes-and-the-need-for-an-immediate-action-plan-to-save-the-biome-215650">drying</a> effects of climate change. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=559&fit=crop&dpr=1 600w, https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=559&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=559&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=702&fit=crop&dpr=1 754w, https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=702&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=702&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Regions where global models agree most on projected future wetter and drier conditions under intermediate and very high emissions. Bar charts show countries ranked by model agreement with lines displaying internal variability.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>A spotlight on Australia</h2>
<p>Our analysis for Australia found climate models agree on a significant drying hotspot over the Indian Ocean, engulfing Australia’s southwestern and south coasts. Spring was the season with the greatest rainfall reduction over this region. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=320&fit=crop&dpr=1 600w, https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=320&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=320&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=402&fit=crop&dpr=1 754w, https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=402&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=402&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Red and blue regions show locations where drying and wetting was detected by multiple climate models</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>What about at a state level? Under a very high emissions scenario, half of models indicate future drier conditions for Victoria. This is driven by changes in winter and spring rainfall. Other states and territories with agreement for a drier future winter, also under a high emissions scenario, include the Australian Capital Territory and Western Australia. The models also project a reduction in spring rainfall in Tasmania.</p>
<p>Some 1.9 million Australians would be affected by these drying patterns, under an intermediate emissions scenario. They comprise those in southwest WA including Perth and the Wheatbelt region. Under very high emissions, as the impacted region expands fourfold towards western Victoria, around 8 million Australians could be affected.</p>
<figure class="align-center ">
<img alt="Australasian regions where most global models agree on future drier and wetter patterns under elevated emissions" src="https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Australasian regions where most global models agree on future drier and wetter patterns under elevated emissions. Southwestern Australia and parts of the south and east coasts may experience a drier future under very high emissions (shaded red). When moderate emissions are considered, the affected region is reduced (red contours).</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>Looking ahead</h2>
<p>As climate change accelerates, it’s essential to understand the potential changes in global rainfall and the consequences on human populations.</p>
<p>My colleagues and I hope our findings reduce uncertainty about how rainfall patterns will shift around the world, and help governments and communities to design effective ways to adapt.</p><img src="https://counter.theconversation.com/content/221004/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ralph Trancoso leads the Queensland Future Climate Science Program - a collaborative program between the University of Queensland and Queensland's Department of Environment and Science undertaking applied climate science to support climate adaptation and natural disaster preparedness.</span></em></p>To date, the effects of climate change on global rainfall has been uncertain. New research overcomes this uncertainty – with alarming results.Ralph Trancoso, Adjunct Associate Professor in Climate Change, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2146192023-10-04T16:40:14Z2023-10-04T16:40:14ZUnderstanding the dynamics of snow cover in forests can help us predict flood risks<figure><img src="https://images.theconversation.com/files/551050/original/file-20230926-17-3adew2.jpg?ixlib=rb-1.1.0&rect=23%2C5%2C3914%2C2964&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A better understanding of the interactions between snow cover and forest will help improve hydrological models and thus ensure public protection against flooding.</span> <span class="attribution"><span class="source">(Benjamin Bouchard)</span>, <span class="license">Fourni par l'auteur</span></span></figcaption></figure><p>For more than six months a year, Quebec’s boreal forest is covered in a thick blanket of snow. While this is essential for the balance of our ecosystems, for the people living downstream from forested watersheds the snow can be like a sword of Damocles hanging over their heads. </p>
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<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong>This article is part of <em>La Conversation Canada’s</em> series <a href="https://theconversation.com/ca-fr/topics/foret-boreale-138017">The boreal forest: A thousand secrets, a thousand dangers</a></strong></p>
<p><br><em>La Conversation Canada invites you to take a virtual walk in the heart of the boreal forest. In this series, our experts focus on management and sustainable development issues, natural disturbances, the ecology of terrestrial wildlife and aquatic ecosystems, northern agriculture and the cultural and economic importance of the boreal forest for Indigenous peoples. We hope you have a pleasant — and informative — walk through the forest!</em></p>
<hr>
<p>The major floods of spring 2023 in the Charlevoix region show why the snow cover poses a risk. </p>
<p>Last winter, the Rivière du Gouffre watershed, of which <a href="https://charlevoixmontmorency.ca/l-obv-cm/territoire/">nearly 75 per cent is covered by forests</a>, accumulated a large amount of snow. The melting of this snow cover combined with an extremely intense rainfall event helped push the river out of its bed, causing <a href="https://www.cbc.ca/news/canada/montreal/flood-baie-saint-paul-residents-cleaning-1.6829490">unprecedented flooding in Baie-Saint-Paul</a>.</p>
<p>As part of my PhD at Université Laval, in collaboration with <a href="https://sentinellenord.ulaval.ca/en/home">Sentinel North</a>, I am looking at the impact of snow cover properties on watershed hydrology in the boreal forest.</p>
<h2>Rain as an energy carrier</h2>
<p>As we saw in the spring of 2023, rain events combined with snow cover can lead to a sudden rise in river water levels. One reason for this is that rainwater transfers heat to the snow. </p>
<p>A heat exchange occurs between rain and snow when their temperatures differ. The snow warms up, and the rain cools down. Once the snow has reached a temperature of 0°C, any additional heat from the rain causes melting.</p>
<p>So, a snow cover of near 0 C, common in spring, and heavy rainfall at high temperatures, together create conditions where both meltwater and rainwater contribute to a higher flow of water. This increases the likelihood of flooding. However, this will only happen if the water produced can flow easily through the snow cover. </p>
<p>On the other hand, a cold snow cover combined with low-temperature rainfall can lead to rainwater freezing in the snow. This water will then remain trapped in the snow and won’t present a flooding risk. </p>
<p>After all, heat exchange goes both ways!</p>
<h2>The snow cover, a complexly structured environment</h2>
<p>The snow cover is a porous medium that does not have uniform physical properties. Rather, it is a stack of snow layers that represent the history of the winter’s meteorological events. Rainwater must percolate through all the snow layers to reach the ground, and eventually, the watercourse.</p>
<p>Some layers, such as fine-grained layers and layers of ice, limit the flow of water through the snow. In contrast, coarse-grained layers, which have larger pores, facilitate the flow of water. As a result, they enable rainwater and meltwater to reach the ground quickly.</p>
<h2>The role of the forest</h2>
<p>The structure of the snow cover influences the risk of flooding. But what effect do forests have on snow structure? </p>
<p>By intercepting part of the precipitation in its solid form (snow), trees limit the accumulation of snow on the ground. That, in turn, contributes to the <a href="https://doi.org/10.1029/JC088iC09p05475">growth of snow grains and pores on the ground</a> through upward water vapour flux. In addition, the discharge of snow intercepted by trees in solid or liquid form <a href="https://doi.org/10.1016/j.foreco.2019.01.052">increases the heterogeneity of the snow cover</a>. These processes promote rapid water flow in the snow cover that forms beneath the trees.</p>
<h2>The same everywhere?</h2>
<p>Forest cover is far from uniform in the boreal forest. It’s more akin to sparse vegetation with treeless zones known as gaps. In these gaps, the structure of the snow cover is very different from that under the trees.</p>
<p>The greater accumulation of snow in the gaps favours the compaction of snow layers and the formation of fine grains. In addition, daily cycles of surface refreezing lead to the formation of low-permeability ice layers. </p>
<p>The snow cover in the gaps is, therefore, less favourable to the percolation of water to the ground <a href="https://doi.org/10.1002/hyp.14681">than that found under the trees</a>.</p>
<p>But does this mean that the presence of gaps reduces the risk of flooding? Not quite.</p>
<h2>Snow melts faster in gaps</h2>
<p>The structure of the snow cover is just one of the factors that influences flooding. Ground that is frozen, which limits infiltration, as well as rapid snowmelt also increase the risk of flooding. </p>
<p>In Québec’s boreal forests, although the ground does not freeze in the gaps between trees due to the insulating nature of the snow cover, the <a href="https://doi.org/10.5194/hess-2023-191">melt rate is much higher</a> because solar radiation is stronger than it is under the trees, particularly in spring. </p>
<p>Although more snow would accumulate in the gaps, it takes less time to melt and reaches the watercourse more quickly than the snow under the trees. That increases waterflow and, as a consequence, the risk of flooding.</p>
<p>The combination of thicker snow cover in the gaps and more permeable snow layers under the trees contributed to the Rivière du Gouffre flooding Baie-Saint-Paul during the extreme rainfall of spring 2023.</p>
<p>Rainfall events like this <a href="https://www.ouranos.ca/en/precipitations-projected-changes">will continue to increase in frequency as global temperatures warm</a>. However, increased knowledge of the interactions between snow cover and forest will help improve hydrological models and ensure better public protection against flooding.</p><img src="https://counter.theconversation.com/content/214619/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Benjamin Bouchard has received funding from the Fonds de recherche Nature et technologie du Québec (FRQNT), the Natural Sciences and Engineering Research Council of Canada (NSERC) and Sentinel North. </span></em></p><p class="fine-print"><em><span>Daniel Nadeau has received funding from Environment and Climate Change Canada, as well as from the Natural Sciences and Engineering Research Council of Canada.</span></em></p><p class="fine-print"><em><span>Florent Domine has received funding from the Natural Sciences and Engineering Research Council of Canada.</span></em></p>A better understanding of the interactions between the boreal forest and snow will make it possible to improve hydrological models and ensure optimal management of the resource.Benjamin Bouchard, Étudiant-chercheur au doctorat en génie des eaux, Université LavalDaniel Nadeau, Professeur titulaire en hydrologie des régions froides, Université LavalFlorent Domine, Professeur, chimie, Université LavalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2115652023-08-21T09:29:41Z2023-08-21T09:29:41ZWhy beaver-like dams can protect communities from flooding – new research<figure><img src="https://images.theconversation.com/files/543416/original/file-20230818-25-h4mqsp.png?ixlib=rb-1.1.0&rect=0%2C0%2C1379%2C1032&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A beaver-like dam at Wilde Brook on the Corve catchment in Shropshire.</span> <span class="attribution"><span class="source">Daniel Jones</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Low cost, human-made river barriers, similar to those built by beavers, can protect communities at risk of flooding. </p>
<p>Our <a href="https://www.sciencedirect.com/science/article/pii/S0022169423006868?via%3Dihub">new research</a> has found that such natural barriers intentionally increase water levels upstream to slow down river flow. These flood barriers are made of materials like logs, branches, mud and leaves. They reduce downstream water levels by deliberately blocking the river and storing the water. They then slow down the river flow during a storm. </p>
<p>Using natural processes to temporarily store water above and below ground is called natural flood management. It essentially involves using nature as a sponge to soak up rainwater. </p>
<p>Not only does this protect communities further down the river from flooding, but it has other benefits too. It helps to <a href="https://www.science.org/doi/10.1126/sciadv.abj0988">enhance</a> habitat diversity for river insects and animals, <a href="https://onlinelibrary.wiley.com/doi/10.1002/esp.5483">trap</a> pollutants, and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0169555X11006088?via%3Dihub">enhance</a> the supply of sediment to the floodplain. </p>
<p>It also adds resilience to the river during spells of dry and hot weather by preventing it from drying up entirely. That was a big issue during the summer of 2022, which was the UK’s <a href="https://www.theguardian.com/uk-news/2023/jul/27/2022-warmest-year-record-uk-met-office-extreme-heat#:%7E:text=2022%20was%20the%20warmest%20year,19%20July%20at%20Coningsby%2C%20Lincolnshire.">warmest on record</a>.</p>
<p>Until our recent research, very little data existed on how effective such river barriers are, or how such approaches might best be used. We also did not understand how these beaver-like dams operate during big storms.</p>
<h2>Slowing the flow</h2>
<p>The presence of a tree trunk or similar obstacle in a river will disrupt its flow. But the exact extent to which the water flow was slowed down by one natural barrier, let alone 50 to 100 barriers, was unknown. We also did not understand how the flow changed for different types of storms and different river settings. </p>
<p>The theoretical idea of a natural barrier is that they have a big hole at the bottom for everyday river flows, as well as holes in between the logs and branches in the upper part of the barrier where the water slowly flows through after a small storm. </p>
<p>During heavy rainfall, the water level gets higher and flows over the top of the barrier. </p>
<figure class="align-center ">
<img alt="A brown beaver sits in brown water with a leafy branch in its mouth" src="https://images.theconversation.com/files/543418/original/file-20230818-29-vmwq35.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/543418/original/file-20230818-29-vmwq35.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/543418/original/file-20230818-29-vmwq35.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/543418/original/file-20230818-29-vmwq35.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/543418/original/file-20230818-29-vmwq35.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=525&fit=crop&dpr=1 754w, https://images.theconversation.com/files/543418/original/file-20230818-29-vmwq35.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=525&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/543418/original/file-20230818-29-vmwq35.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=525&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Beavers are natural engineers and make dams by using their teeth to cut trees and branches.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/european-beaver-scotland-uk-113509768">Mark A. Rice/Shutterstock</a></span>
</figcaption>
</figure>
<p>We found that the barrier’s holes can become bigger due to the changing flow of the river. In addition, during a storm, the twigs, leaves and sediment transported by the river flow can accumulate behind the barrier, causing it to grow in size. So, we needed to understand how these natural barriers evolve over time to understand the range of their effectiveness.</p>
<p>Engineers use computer models called “<a href="https://wires.onlinelibrary.wiley.com/doi/epdf/10.1002/wat2.1568">flood models</a>” which use mathematical equations to predict how different storm sizes impact on river water levels. These help us predict when a river will burst its banks, and then the location and extent of a flooded area. </p>
<p>This is important as it helps governments decide on what type of flood defence is needed to protect people from existing and future flooding. It also helps to determine where new buildings can be constructed that will be safe from flooding, and that such new builds will not make existing houses more vulnerable to floods. </p>
<h2>The Corve catchment in Shropshire</h2>
<p>We gathered data from 105 natural flood barriers on a small Shropshire river to measure their effectiveness in holding back flood waters and to understand how natural flood barriers operate during a storm. We collected water levels, velocity and flow data every 15 minutes for a two year period. </p>
<p>We also used a technique called “<a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/photogrammetry">photogrammetry</a>”. This is where data from drone photographs are used to obtain accurate measurements of the topography in areas of river covered by trees and other vegetation. </p>
<p>Our results showed that the natural flood barriers at the site could store enough water to fill at least four Olympic-sized swimming pools during significant storms such as <a href="https://www.metoffice.gov.uk/weather/warnings-and-advice/uk-storm-centre/storm-dennis">Storm Dennis</a>, which hit the UK in February 2020. </p>
<p>This shows that natural barriers are effective in slowing down the flow of the river during periods of rainfall, storing up vast quantities of water which would otherwise rush through, causing damage to areas downstream. Instead, this force is slowly released over a period of one to two weeks. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/beavers-offer-lessons-about-managing-water-in-a-changing-climate-whether-the-challenge-is-drought-or-floods-168545">Beavers offer lessons about managing water in a changing climate, whether the challenge is drought or floods</a>
</strong>
</em>
</p>
<hr>
<p>Our research shows that natural flood management works. It is also cheaper than traditional engineering works and complements rather than replaces existing flood defences.</p>
<p>The information from our study will help natural barriers be more accurately represented in flood models, using our new observations on barrier changes over time and effectiveness during storms. </p>
<p>Society can get better value from our flood defence spending by supporting landowners to install natural solutions. This is increasingly an issue as more and more houses are <a href="https://www.independent.co.uk/news/uk/home-news/homes-flooding-building-council-lvgi-b1962122.html">being built</a> on land at risk of flooding. </p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
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<hr><img src="https://counter.theconversation.com/content/211565/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Catherine Wilson receives funding from the EPSRC, the Environment Agency, Shropshire Council, and Merthyr Tydfil County Borough Council. She received funding from Shropshire Council and Environment Agency to conduct this work. She is a member of the Welsh Government's Flood Coastal Erosion Committee. </span></em></p><p class="fine-print"><em><span>Elizabeth Follett receives funding from the Royal Academy of Engineering. She received funding from the European Regional Development Fund through the Welsh Government Sêr Cymru program 80762-CU-241 with a contribution from Jacobs, and the European Union's Horizon 2020 research and innovation program under the Marie Skłowdowska‐Curie grant agreement WoodJam No. 745348 to conduct this work. </span></em></p><p class="fine-print"><em><span>Valentine Muhawenimana does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A new study shows that river barriers, similar to those built by beavers, can protect areas at risk of flooding by storing water upstream.Catherine Wilson, Reader in Environmental Hydraulics, Cardiff UniversityElizabeth Follett, Royal Academy of Engineering Research Fellow, University of LiverpoolValentine Muhawenimana, Postdoctoral Research Associate in Environmental Engineering, Cardiff UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2049752023-05-04T14:25:46Z2023-05-04T14:25:46ZCloud seeding can increase rain and snow, and new techniques may make it a lot more effective – podcast<figure><img src="https://images.theconversation.com/files/524204/original/file-20230503-19-bx8o26.jpg?ixlib=rb-1.1.0&rect=418%2C594%2C6930%2C4308&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cloud seeding can increase rainfall and reduce hail damage to crops, but its use is limited.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/colorado-supercell-royalty-free-image/1303884216?phrase=Rain+storm&adppopup=true">John Finney Photography/Moment via Getty Images</a></span></figcaption></figure><p>When an unexpected rainstorm leaves you soaking wet, it is an annoyance. When a drought leads to fires, crop failures and water shortages, the significance of weather becomes vitally important.</p>
<p>If you could control the weather, would you?</p>
<p>Small amounts of rain can mean the difference between struggle and success. For <a href="https://climateviewer.com/2014/03/25/history-cloud-seeding-pluviculture-hurricane-hacking/">nearly 80 years</a>, an approach called cloud seeding has, in theory, given people the ability to get more rain and snow from storms and make hailstorms less severe. But only recently have scientists been able to peer into clouds and begin to understand how effective cloud seeding really is.</p>
<p>In this episode of “The Conversation Weekly,” we speak with three researchers about the simple yet murky science of cloud seeding, the economic effects it can have on agriculture, and research that may allow governments to use cloud seeding in more places.</p>
<iframe src="https://embed.acast.com/60087127b9687759d637bade/64536722a66d2600116de8f4" frameborder="0" width="100%" height="190px"></iframe>
<p><iframe id="tc-infographic-561" class="tc-infographic" height="100" src="https://cdn.theconversation.com/infographics/561/4fbbd099d631750693d02bac632430b71b37cd5f/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p><a href="https://scholar.google.com/citations?user=BSQl42wAAAAJ&hl=en&oi=ao">Katja Friedrich</a>, a professor of atmospheric and oceanic sciences at the University of Colorado, Boulder in the U.S., is a leading researcher on cloud seeding. “When we do cloud seeding, we are looking for clouds that have tiny super-cooled liquid droplets,” she explains. Silver iodide is very similar in structure to an ice crystal. When the droplets touch a particle of silver iodide, “they freeze, then they can start merging with other ice crystals, become snowflakes and fall out of the cloud.”</p>
<p>While the process is fairly straightforward, measuring how effective it is in the real world is not, according to Friedrich. “The problem is that once we modify a cloud, it’s really difficult to say what would’ve happened if you hadn’t cloud-seeded.” It’s hard enough to predict weather without messing with it artificially. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/524222/original/file-20230503-1294-7b7p2j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A plane wing with a cylindrical device attached." src="https://images.theconversation.com/files/524222/original/file-20230503-1294-7b7p2j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/524222/original/file-20230503-1294-7b7p2j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=370&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524222/original/file-20230503-1294-7b7p2j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=370&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524222/original/file-20230503-1294-7b7p2j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=370&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524222/original/file-20230503-1294-7b7p2j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=465&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524222/original/file-20230503-1294-7b7p2j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=465&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524222/original/file-20230503-1294-7b7p2j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=465&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cloud seeding is usually done by planes equipped with devices – like the one attached to the wing of this plane – that spray silver iodide into the atmosphere.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Cloud_seeding#/media/File:Hagelflieger-EDTD.jpg">Zuckerle/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In 2017, Friedrich’s research group had a breakthrough in measuring the effect of cloud seeding. “We flew some aircraft, released silver iodide and generated these clouds that were like these six exact lines that were downstream of where the aircraft were seeding,” she says. They then had a second aircraft fly through the clouds. “We could actually <a href="https://doi.org/10.1073/pnas.1716995115">quantify how much snow we could produce</a> by two hours of cloud seeding.” That effect, according to research on cloud seeding, is an increase in precipitation of somewhere around 5% to 20% or 30%, depending on conditions.</p>
<p>Measuring the effect on precipitation – whether rain or snow – directly may have taken complex science and a bit of luck, but in places that have been using cloud seeding for long periods of time, the economic benefits are shockingly clear. </p>
<p><a href="https://www.ndsu.edu/agriculture/ag-home/directory/dean-bangsund">Dean Bangsund</a> is a researcher at North Dakota State University who studies the economics of agriculture. “We have a high amount of hail damage in North Dakota,” said Bangsund. For decades, the state government has been using cloud seeding to reduce hail damage, as cloud seeding leads to the formation of more pieces of smaller hail compared to fewer pieces of larger hail. “It doesn’t 100% eliminate hail; it’s designed to soften the impact.”</p>
<p>Every 10 years, the state of North Dakota does an <a href="https://www.cabdirect.org/cabdirect/abstract/20193399635">analysis on the economic impacts of the cloud seeding</a> program, measuring both reduction in hail damage and benefits from increased rain. Bangsund led the last report and says that for every dollar spent on the cloud seeding program, “we are looking at something that is anywhere from $8 or $9 in benefit on the really lowest scale, up to probably $20 of impact per acre.” With millions of acres of agricultural fields in the cloud seeding area, that is a massive economic benefit.</p>
<p>Both Freidrich and Bangsund emphasized that cloud seeding, while effective in some cases, cannot be used everywhere. There is also a lot of uncertainty in how much of an effect it has. One way to improve the effectiveness and applicability of cloud seeding is by improving the seed. <a href="https://scholar.google.com/citations?view_op=list_works&hl=en&hl=en&user=OxrNpiEAAAAJ&sortby=pubdate">Linda Zou</a> is a professor of civil infrastructure and environmental engineering at Khalifa University in the United Arab Emirates. </p>
<p>Her work has focused on developing a replacement for silver iodide, and her lab has <a href="https://www.technologyreview.com/2022/03/28/1048275/scientists-advance-cloud-seeding-capabilities-with-nanotechnology/">developed what she calls a nanopowder</a>. “I start with table salt, which is sodium chloride,” says Zou. “This desirable-sized crystal is then coated with a thin nanomaterial layer of titanium dioxide.” When salt gets wet, it melts and forms a droplet that can efficiently merge with other droplets and fall from a cloud. Titanium dioxide attracts water. Put the two together and you get a very effective cloud-seeding material. </p>
<p>From indoor experiments, Zou found that “with the nanopowders, there are 2.9 times the formation of larger-size water droplets.” These nanopowders can also form ice crystals at warmer temperatures and less humidity than silver iodide. </p>
<p>As Zou says, “if the material you are releasing is more reactive and can work in a much wider range of conditions, that means no matter when you decide to use it, the chance of success will be greater.”</p>
<hr>
<p>This episode was written and produced by Katie Flood. Mend Mariwany is the executive producer of The Conversation Weekly. Eloise Stevens does our sound design, and our theme music is by Neeta Sarl.</p>
<p>You can find us on Twitter <a href="https://twitter.com/TC_Audio">@TC_Audio</a>, on Instagram at <a href="https://www.instagram.com/theconversationdotcom/">theconversationdotcom</a> or <a href="mailto:podcast@theconversation.com">via email</a>. You can also subscribe to The Conversation’s <a href="https://theconversation.com/newsletter">free daily email here</a>. </p>
<p>Listen to “The Conversation Weekly” via any of the apps listed above, download it directly via our <a href="https://feeds.acast.com/public/shows/60087127b9687759d637bade">RSS feed</a> or find out <a href="https://theconversation.com/how-to-listen-to-the-conversations-podcasts-154131">how else to listen here</a>.</p>
<hr><img src="https://counter.theconversation.com/content/204975/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>None of the interviewees work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p><p class="fine-print"><em><span> </span></em></p>Cloud seeding – spraying materials into clouds to increase precipitation – has been around for nearly 80 years. But only recently have scientists been able to measure how effective it really is.Daniel Merino, Associate Science Editor & Co-Host of The Conversation Weekly Podcast, The ConversationNehal El-Hadi, Science + Technology Editor & Co-Host of The Conversation Weekly Podcast, The ConversationLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2029522023-04-24T12:24:51Z2023-04-24T12:24:51ZCan rainbows form in a circle? Fun facts on the physics of rainbows<figure><img src="https://images.theconversation.com/files/521644/original/file-20230418-20-88ojk7.jpg?ixlib=rb-1.1.0&rect=0%2C13%2C8959%2C5547&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The higher your vantage point, the more likely you’ll see more of the rainbow’s circle. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/double-rainbow-hangs-in-the-sky-above-buildings-and-the-news-photo/1405823752">Chen Hui/VCG via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>Can rainbows form in a circle? – Henry D., age 7, Cambridge, Massachusetts</strong></p>
</blockquote>
<hr>
<p>The legend goes that there is a pot of gold hidden at the end of every rainbow. But is there really an “end” to a rainbow, and can we ever get to it?</p>
<p>Most us go through life seeing rainbows only as arches of color in the sky, but that’s only half of what is really a circle of color.</p>
<p>Normally, when you look at a rainbow, the Earth’s horizon in front of you hides the bottom half of the circle. But if you are standing on a mountain where you can see both above and below you, and the sun is behind you and it is misty or has just rained, chances are good that you will see more of the rainbow’s circle.</p>
<figure class="align-center ">
<img alt="A rainbow in the mist below a waterfall in Iceland." src="https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&rect=0%2C52%2C5000%2C3270&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">How full this rainbow looks depends in part on how high up you’re standing while watching sunlight hit the waterfall’s mist.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/iceland-south-coast-skogarfoss-waterfall-rainbow-news-photo/452271798">Wolfgang Kaehler/LightRocket via Getty Images</a></span>
</figcaption>
</figure>
<p>To see the full circle, however, you will have to be in an airplane, literally above the clouds. Or you could create your own rainbow. I am <a href="https://www.uml.edu/Honors/People/chowdhury-partha.aspx">a physicist</a>, and I’ll explain how to do that in a minute.</p>
<h2>How a rainbow forms</h2>
<p><a href="https://scijinks.gov/rainbow/">Rainbows form</a> when sunlight from behind you hits millions of tiny round water droplets in front of you and bounces back to your eyes.</p>
<p>As a sunbeam hits a droplet at an angle, it bends into the water and separates out into a spectrum of colors. Scientists <a href="https://global.canon/en/technology/s_labo/light/001/02.html">call the bending of light “refracting</a>.” The colors separate because each “color” of light <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/optical-effects/rainbows/colours-of-the-rainbow">travels with a different speed</a> in water, or, for that matter, any transparent material that light can travel through, like glass in a prism.</p>
<p>When the colors hit the back wall of the water droplet, the angle is now too shallow for them to bend out into the air, so they reflect back into the water droplet and return to its entrance wall. From there, the colors can bend out again into air and reach your eye.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/q73VNpFA-0Q?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The United Kingdom’s Meteorology Office explains how light refracts, or bends, in a water droplet or a prism.</span></figcaption>
</figure>
<p>As you look at these droplets, the different colors happen to bunch up at a slightly different angle, and each color forms the <a href="https://atoptics.co.uk/rainbows/primcone.htm">circular rim of a cone</a> with your eye at the tip of the cone. And, voila, you have your own personal rainbow.</p>
<p>The droplets that send the colors to your eye cannot send them to anyone else, so even though everyone near you sees the same rainbow at a distance, each person really sees their own slightly different rainbow. It’s all in the eye of the beholder.</p>
<p>For rainbows to form, the shape of the water droplets has to be very close to a sphere for all of them to bend and reflect the colors in harmony. This happens for very small droplets, such as a fine mist, or just after a rain shower when the air is just moist. As the droplets get larger, gravity distorts their shape and the rainbow vanishes.</p>
<figure class="align-center ">
<img alt="An elephant in water closes its eyes while the photographer captures a rainbow across its trunk and forehead." src="https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Even though it looks like this elephant is bathing in a rainbow, the elephant wouldn’t see it in the same way.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/an-elephant-is-pictured-under-a-rainbow-of-water-sprayed-to-news-photo/1242012110">Mads Claus Rasmussen / Ritzau Scanpix / AFP</a></span>
</figcaption>
</figure>
<p>A rainbow is not physically present where it appears to be, similar to your image in a mirror. So, I’m sorry to say that you can never actually reach your rainbow. And, alas, nobody can ever find that pot of gold.</p>
<p>But you can <a href="https://www.youtube.com/watch?v=dIdE-pqYqbs">create your own rainbow</a>. </p>
<h2>How to create and see a circular rainbow</h2>
<p>One experiment you can try in summer is to turn on a sprinkler hose using the “mist” setting. Remember to have the sun behind you. If you create a fine mist screen in front of you and look at your shadow, you might see a rainbow. </p>
<figure class="align-center ">
<img alt="A young boy plays in a fountain, with a rainbow overhead." src="https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=497&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=497&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=497&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">It might take some work, but you can see your own full-circle rainbows in the mist.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/young-boy-cools-off-under-a-rainbow-in-a-fountain-on-a-warm-news-photo/1266045824">Gary Hershorn/Getty Images</a></span>
</figcaption>
</figure>
<p>It is not difficult to see colors, but to see a full circle, you will need some patience and practice, just like scientists.</p>
<p>So next time you are on an airplane, grab the window seat. If you are flying a little above the cloud cover, keep a lookout for the small shadow of your plane on the clouds. That means the sun is behind you. </p>
<p>The clouds are tiny water droplets, so chances are you may see a small circle of color around the shadow of the airplane. This phenomenon is <a href="https://science.howstuffworks.com/nature/climate-weather/atmospheric/pilots-glory-rainbow-airplane-shadow.htm">nicknamed “pilot’s glory</a>,” because pilots who fly all the time and have a good view from the cockpit have a better chance of seeing it.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An airplane's shadow has a circular rainbow around it as it flies over mountains." src="https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The circular rainbow you see around an airplane’s shadow is called ‘pilot’s glory.’</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/imatty35/6708114761/">Matthew Straubmuller/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>And if you really can’t wait to see what it looks like, there’s <a href="https://education.nationalgeographic.org/resource/rainbow/">always the internet</a>.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/202952/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Partha Chowdhury does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Each rainbow is personal – the rainbow you see isn’t exactly the same rainbow the next person sees. It’s all in the eye of the beholder.Partha Chowdhury, Professor of Physics, UMass LowellLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2038742023-04-17T12:43:14Z2023-04-17T12:43:14ZEpic snow from all those atmospheric rivers in the West is starting to melt, and the flood danger is rising<figure><img src="https://images.theconversation.com/files/521225/original/file-20230417-20-d354fm.jpeg?ixlib=rb-1.1.0&rect=0%2C2%2C1917%2C1336&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Tulare Lake is reemerging as flood water spreads across miles of California farmland.
</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/agribusiness-consultant-mark-grewel-stands-on-a-farm-road-news-photo/1249529651">Luis Sinco / Los Angeles Times via Getty Images</a></span></figcaption></figure><p><em>To get a sense of the enormous amount of water atmospheric rivers dumped on the Western U.S. this year and the magnitude of the flood risk ahead, take a look at California’s Central Valley, where about <a href="https://ca.water.usgs.gov/projects/central-valley/about-central-valley.html">a quarter of the nation’s food</a> is grown.</em></p>
<p><em>This region was once home to the largest freshwater lake west of the Rockies. But the rivers that fed Tulare Lake were <a href="https://sarahamooneymuseum.org/a-look-back/tulare-lake-was-once-considered-largest-body-of-water-west-of-mississippi/">dammed and diverted</a> long ago, leaving it nearly dry by 1920. Farmers have been growing food on the fertile lake bed for decades.</em></p>
<p><em>This year, however, <a href="https://earthobservatory.nasa.gov/images/151174/return-of-tulare-lake">Tulare Lake is remerging</a>. Runoff and snowmelt from the Sierra Nevada have overwhelmed waterways and flooded farms and orchards. After similar storms in 1983, the lake covered <a href="https://www.upi.com/Archives/1983/05/30/The-massive-wall-of-debris-laden-water-that-roared-down/9734423115200/">more than 100 square miles</a>, and scientists say this year’s precipitation is looking a lot like 1983. Communities there and across the West are preparing for flooding and mudslide disasters as <a href="https://www.drought.gov/drought-status-updates/snow-drought-current-conditions-and-impacts-west-2023-04-06">record snow</a> begins to melt.</em></p>
<figure class="align-center ">
<img alt="Satellite images show farmland with only a few small lakes in early March, then a larger lake covering that farmland by early April." src="https://images.theconversation.com/files/521150/original/file-20230416-28-gpz5lm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521150/original/file-20230416-28-gpz5lm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=437&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521150/original/file-20230416-28-gpz5lm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=437&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521150/original/file-20230416-28-gpz5lm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=437&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521150/original/file-20230416-28-gpz5lm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=549&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521150/original/file-20230416-28-gpz5lm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=549&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521150/original/file-20230416-28-gpz5lm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=549&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tulare Lake, long dry, begins to reemerge in March 2023 as flood water spreads across farm fields.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/151174/return-of-tulare-lake">NASA Earth Observatory</a></span>
</figcaption>
</figure>
<p><em>We asked Chad Hecht, a meteorologist with the Center for Western Weather and Water Extremes at the University of California San Diego’s Scripps Institution of Oceanography, how 2023’s storms compare to past extremes and what to expect in the future.</em></p>
<h2>How extreme were this year’s atmospheric rivers?</h2>
<p>California averages about 44 atmospheric rivers a year, but typically, only about six of them are strong storms that contribute most of the annual precipitation total and cause the kind of flooding we’ve seen this year.</p>
<p>This year, in a three-week window from about Dec. 27, 2022, to Jan. 17, 2023, we saw nine atmospheric rivers make landfall, five of them <a href="https://doi.org/10.1029/2022JD037180">categorized as strong</a> or greater magnitude. That’s how active it’s been, and that was only the beginning.</p>
<figure class="align-center ">
<img alt="Map of where atmospheric rivers arrived through the end of March 2023" src="https://images.theconversation.com/files/521092/original/file-20230414-26-gufn23.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521092/original/file-20230414-26-gufn23.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521092/original/file-20230414-26-gufn23.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521092/original/file-20230414-26-gufn23.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521092/original/file-20230414-26-gufn23.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=540&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521092/original/file-20230414-26-gufn23.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=540&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521092/original/file-20230414-26-gufn23.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=540&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Where atmospheric rivers hit during the first half of the 2023 water year, which started Oct. 1. The arrows show where the storms were strongest, but their impact reached far wider.</span>
<span class="attribution"><a class="source" href="https://cw3e.ucsd.edu/">Center For Western Weather and Water Extremes, Scripps Institution of Oceanography</a></span>
</figcaption>
</figure>
<p>In all, the state experienced 31 atmospheric rivers through the end of March: one extreme, six strong, 13 moderate and 11 weak. And other storms in between gave the Southern Sierra one of its wettest Marches on record. </p>
<p>These storms don’t just affect California. Their <a href="https://www.nrcs.usda.gov/wps/portal/wcc/home/quicklinks/imap">precipitation</a> has pushed the snow-water equivalent levels <a href="https://www.nrcs.usda.gov/wps/portal/wcc/home/quicklinks/imap">well above average across much of the West</a>, including in Oregon, Nevada, Utah, Idaho and the mountains of western Colorado, Arizona and New Mexico.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/521152/original/file-20230416-28-zyyvgq.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/521152/original/file-20230416-28-zyyvgq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521152/original/file-20230416-28-zyyvgq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=726&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521152/original/file-20230416-28-zyyvgq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=726&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521152/original/file-20230416-28-zyyvgq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=726&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521152/original/file-20230416-28-zyyvgq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=912&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521152/original/file-20230416-28-zyyvgq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=912&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521152/original/file-20230416-28-zyyvgq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=912&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Snow water equivalent is a measure of the water in snowpack. Many basins across the West were well over 200% of average in 2023.</span>
<span class="attribution"><a class="source" href="https://www.nrcs.usda.gov/wps/portal/wcc/home/quicklinks/imap">NRCS/USDA</a></span>
</figcaption>
</figure>
<p>In terms of records, the big numbers this year were in California’s Southern Sierra Nevada. The region has had 11 moderate atmospheric rivers – double the average of 5.5 – and an additional four strong ones. </p>
<p>Overall, California has about <a href="https://cdec.water.ca.gov/reportapp/javareports?name=PLOT_SWC.pdf">double its normal snowpack</a>, and some locations have experienced more than double the number of strong atmospheric rivers it typically sees. The result is that Northern Sierra snow water content is 197% of normal. The central region is 238% of normal, and the Southern Sierra is 296% of normal.</p>
<h2>What risks does all that snow in the mountains create?</h2>
<p>There is <a href="https://www.kcra.com/article/tahoe-ski-resorts-extend-season-snow-palisades/43403916">a lot of snow</a> in the Sierra Nevada, and it is going to come off the mountains at some point. It’s possible we are going to be looking at snowmelt into late June or July in California, and that’s far into summer for here.</p>
<p>Flooding is certainly a possibility. The closest year for comparison in terms of the amount of snow would be 1983, when the average statewide snow water content was 60.3 inches in May. That was a <a href="https://www.pressdemocrat.com/article/news/photos-a-look-back-at-the-1983-floods">rough year</a>, with <a href="https://www.washingtonpost.com/archive/politics/1983/06/01/rain-melting-snow-continue-to-menace-states-in-the-west/4aa62a9a-ce91-46f7-a579-607c4843a318/">flooding and mudslides</a> in <a href="https://www.sltrib.com/news/environment/2023/02/20/1983-downtown-salt-lake-turned/">several parts of the West</a> and extensive crop damage.</p>
<p><iframe id="V7dT9" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/V7dT9/8/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>This year, portions of the Southern Sierra Nevada have passed 1983’s levels, and <a href="https://www.latimes.com/california/story/2023-04-06/california-tulare-lake-storms-flooding-satellite-photos">Tulare Lake</a> is filling up again for the <a href="https://www.cnbc.com/2023/04/04/a-long-dormant-lake-has-reappeared-in-california-bringing-havoc-along-with-it.html">first time in decades</a>. Tulare Lake is an indication of just how extreme this year has been, and the risk is rising as the snow melts.</p>
<h2>The transition from extreme drought in 2022 to record snow was fast. Is that normal?</h2>
<p>California and some other parts of the West are known for weather whiplash. We frequently go from too dry to too wet. </p>
<p>2019 was another above-average year in terms of precipitation in California, but after that we saw <a href="https://droughtmonitor.unl.edu/DmData/TimeSeries.aspx">three straight years of drought</a>. We went from 13 strong or greater magnitude atmospheric rivers in 2017 to just three in 2020 and 2021, combined.</p>
<figure class="align-center ">
<img alt="Map showing well-above average precipitation across California, Nevada and Utah in particular." src="https://images.theconversation.com/files/521088/original/file-20230414-28-qttrjl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521088/original/file-20230414-28-qttrjl.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=724&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521088/original/file-20230414-28-qttrjl.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=724&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521088/original/file-20230414-28-qttrjl.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=724&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521088/original/file-20230414-28-qttrjl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=910&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521088/original/file-20230414-28-qttrjl.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=910&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521088/original/file-20230414-28-qttrjl.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=910&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The onslaught of powerful atmospheric rivers pushed precipitation to well above average across large parts of the West in 2023, following three years of severe drought.</span>
<span class="attribution"><a class="source" href="https://cw3e.ucsd.edu/">Center for Western Weather and Water Extremes, Scripps Institution of Oceanography</a></span>
</figcaption>
</figure>
<p>California relies on these storms for <a href="https://water.ca.gov/News/Blog/2020/October/Atmospheric-Rivers-and-Their-Impact-on-California-Reservoirs">about half its water supply</a>, but if the West gets too many atmospheric rivers back to back, that starts to have harmful impacts, like the heavy snowpack that <a href="https://kslnewsradio.com/1994522/snow-causing-roofs-to-collapse-across-the-state-expert-offers-helpful-tips/">collapsed roofs</a> in the mountains this year, and <a href="https://youtu.be/sKx-wSICxQQ">flash flooding</a> and <a href="https://www.cbsnews.com/video/california-dangerous-mudslides-after-storms/#x">landslides</a>. These successive storms are typically referred to as <a href="https://cw3e.ucsd.edu/cw3e-publication-notice-atmospheric-river-families-definition-and-associated-synoptic-conditions/">atmospheric river families</a> and can result in exacerbated hydrologic impacts by quickly saturating soils and not allowing rivers and streams to recede back to base flow between storms.</p>
<h2>Are atmospheric rivers becoming more intense with a warming climate?</h2>
<p>There’s been <a href="https://theconversation.com/atmospheric-river-storms-can-drive-costly-flooding-and-climate-change-is-making-them-stronger-128902">a lot of research</a> on the impact of temperature because of how reliant California is on these storms for its water supply.</p>
<p>Atmospheric rivers are long, narrow corridors of water vapor in the sky that <a href="https://www.usgs.gov/news/featured-story/rivers-sky-6-facts-you-should-know-about-atmospheric-rivers">typically start in the tropics</a> as water evaporates and is pulled poleward by atmospheric circulations. They carry a lot of moisture – on average, their water vapor transport is more than <a href="https://doi.org/10.1175/JHM-D-17-0036.1">twice the flow of the Amazon River</a>. When they reach land, mountains <a href="https://www.noaa.gov/stories/what-are-atmospheric-rivers">force the air to rise</a>, which wrings out some of that moisture.</p>
<p>In a warming climate, the warmer air can hold more moisture. That can increase the capacity of atmospheric rivers, with more water vapor resulting in stronger storms.</p>
<figure class="align-center ">
<img alt="An animation shows two atmospheric rivers moving across the Pacific Ocean from the tropics." src="https://images.theconversation.com/files/521070/original/file-20230414-18-eukcdy.gif?ixlib=rb-1.1.0&rect=107%2C43%2C767%2C499&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521070/original/file-20230414-18-eukcdy.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=332&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521070/original/file-20230414-18-eukcdy.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=332&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521070/original/file-20230414-18-eukcdy.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=332&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521070/original/file-20230414-18-eukcdy.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=418&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521070/original/file-20230414-18-eukcdy.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=418&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521070/original/file-20230414-18-eukcdy.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=418&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An example of an atmospheric river approaching the West Coast.</span>
<span class="attribution"><a class="source" href="http://tropic.ssec.wisc.edu/real-time/mtpw2/product.php?color_type=tpw_nrl_colors&prod=global2&timespan=24hrs&anim=anigf">Space Science and Engineering Center, University of Wisconsin-Madison</a></span>
</figcaption>
</figure>
<p>Research by some of my colleagues at Scripps Institution of Oceanography also suggests that California will <a href="https://doi.org/10.1038/s41598-022-15474-2">see fewer storms that aren’t atmospheric rivers</a>. But the state will likely see <a href="https://doi.org/10.1038/s41598-017-11285-y">more intense atmospheric rivers</a> as temperatures rise. California will be even more reliant on these atmospheric rivers for its snow, which will result in drier dries and wetter wets.</p>
<p>So, we’re likely to see this whiplash continue, but to a more extreme level, with longer periods of dry weather when we’re not getting these storms. But when we do get these storms, they have the potential to be more extreme and then result in more flooding.</p>
<p>In the more immediate future, we’re likely <a href="https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml">headed into an El Niño</a> this year, with warm tropical Pacific waters that shift weather patterns around the world. Typically, El Niño conditions are associated with more atmospheric river activity, especially in Central and Southern California.</p>
<p>So, we may see another wet year like this again in 2024.</p><img src="https://counter.theconversation.com/content/203874/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chad Hecht receives funding from California Department of Water Resources, U.S. Army Corps of Engineers, Sonoma Water, Yuba Water Agency, & Orange County Water District. </span></em></p>This year’s Sierra snowpack is looking a lot like 1983’s, and that was a year of flooding and mudslide disasters. A meteorologist explains what’s ahead.Chad Hecht, Research and Operations Meteorologist, Center for Western Weather and Water Extremes, University of California, San DiegoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2017782023-03-27T19:01:49Z2023-03-27T19:01:49Z2022 was a good year for nature in Australia – but three nasty problems remain<figure><img src="https://images.theconversation.com/files/517575/original/file-20230327-16-flxve.jpg?ixlib=rb-1.1.0&rect=6%2C0%2C4594%2C3456&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock </span></span></figcaption></figure><p>A new <a href="https://www.ausenv.online">report card</a> on Australia’s environment reveals 2022 was a bumper year for our rivers and vegetation – but it wasn’t enough to reverse the long-term decline in plant and animal species.</p>
<p>The analysis was drawn from many millions of measurements of weather, biodiversity, water availability, river flows and the condition of soil and vegetation. The data is gathered from satellites and field stations and processed by a supercomputer. </p>
<p>From the data, we calculate a score between 0 and 10 to determine the overall condition of Australia’s environment. </p>
<p>In 2022, a third and very wet La Niña year brought a strong improvement in several key indicators, leading to a national score of 8.7 out of 10. This is the best score since 2011. But unfortunately, three wicked problems remain.</p>
<figure class="align-center ">
<img alt="scientist kneels in water and takes observation" src="https://images.theconversation.com/files/517574/original/file-20230327-14-t3yn8b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517574/original/file-20230327-14-t3yn8b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517574/original/file-20230327-14-t3yn8b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517574/original/file-20230327-14-t3yn8b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517574/original/file-20230327-14-t3yn8b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517574/original/file-20230327-14-t3yn8b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517574/original/file-20230327-14-t3yn8b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A vast number of datasets are combined to generate the environmental scorecard.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>First, the good news</h2>
<p>By some measures, 2022 was the best year for water availability and plant growth since our national score system began 23 years ago. </p>
<p>New South Wales, Victoria and the ACT enjoyed the highest environmental scores since before 2000. South Australia and Queensland also improved.</p>
<p>Scores for rainfall, river flows and the extent of floodplain inundation were the highest since before 2000 in many parts of eastern Australia. The water supplies of all eastern capital cities all rose and several reached capacity. </p>
<p>Wetland area and waterbird breeding were well above the long-term average. Vegetation density, growth rates and tree cover in NSW and Queensland were the best since before 2000.</p>
<p>It was a bumper year for dryland farmers. Average national growth rates in dryland cropping were a massive 49% better than average conditions. The many full or filling reservoirs are also good news for irrigators.</p>
<h2>What about the losers?</h2>
<p>Some regions missed out on the rainfall bonanza, and many environmental indicators declined. They include the Top End in the Northern Territory, southern inland Western Australia and western Tasmania. </p>
<p>Across the NT, low rainfall and high temperatures meant environmental scores once more declined to the low values seen before 2021. </p>
<p>And in areas where rainfall was high, not everyone benefited. Many homes and businesses flooded, and some farmers lost crops or stock.</p>
<p>At the end of 2022, <a href="https://www.theguardian.com/australia-news/2023/jan/01/river-murray-fish-kill-concerns-grow-as-flood-waters-peak-in-south-australia">reports emerged</a> that floodwaters were causing so-called “blackwater events” and fish kills in the Murray River. Murky floodwaters also ran into the ocean and smothered seagrass meadows, leading <a href="https://theconversation.com/dugongs-and-turtles-are-starving-to-death-in-queensland-seas-and-la-ninas-floods-are-to-blame-190663">dugongs and sea turtles</a> to starve.</p>
<p>The ocean around Australia was the warmest on record in 2022. The Great Barrier Reef suffered the <a href="https://www.aims.gov.au/research-topics/environmental-issues/coral-bleaching/coral-bleaching-events">fourth mass bleaching</a> event in seven years – and alarmingly, the first to occur during a La Niña year, which is usually cooler. </p>
<p>Fortunately, conditions for the remainder of the year favoured coral recovery. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-report-shows-alarming-changes-in-the-entire-global-water-cycle-197535">New report shows alarming changes in the entire global water cycle</a>
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</em>
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<hr>
<figure class="align-center ">
<img alt="flood-damaged doll and other items with house in background" src="https://images.theconversation.com/files/517588/original/file-20230327-14-49f0b0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517588/original/file-20230327-14-49f0b0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517588/original/file-20230327-14-49f0b0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517588/original/file-20230327-14-49f0b0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517588/original/file-20230327-14-49f0b0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517588/original/file-20230327-14-49f0b0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517588/original/file-20230327-14-49f0b0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Floodwaters severely damaged homes and businesses last year.</span>
<span class="attribution"><span class="source">Darren England/AAP</span></span>
</figcaption>
</figure>
<h2>Chronic ailments</h2>
<p>Despite many positive indicators, three severe, chronic and untreated problems continue to weaken our environment: habitat destruction, invasive species and climate change.</p>
<p>The rate of habitat destruction shows little sign of improvement. Much vegetation continues to be removed for new housing, mining and agriculture. Fire activity in 2022 was low, but climate change means bushfires will be back soon, and become more frequent and severe over time. </p>
<p>La Niña is already on the way out, although it will probably take more than one hot and dry year before we experience <a href="https://theconversation.com/a-major-scorecard-gives-the-health-of-australias-environment-less-than-1-out-of-10-133444">megafires</a> such as those in the Black Summer of 2019-20.</p>
<p>The scorecard also shows Australia is still struggling to combat pest species. They include fungi, invasive weeds, carp, cane toads, rats, rabbits, goats, pigs, foxes and cats. Every year, about eight million feral cats and foxes <a href="https://theconversation.com/1-7-million-foxes-300-million-native-animals-killed-every-year-now-we-know-the-damage-foxes-wreak-177832">kill</a> 1.5 billion native reptiles, birds and mammals. </p>
<p>Climate change remains a huge problem. La Niña normally brings cool conditions and the average temperature last year in Australia was the coolest since 2012. But it was still relatively warm, at 0.5°C above the long-term average. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/fear-and-wonder-podcast-how-scientists-know-the-climate-is-changing-202237">Fear and Wonder podcast: how scientists know the climate is changing</a>
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</em>
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<hr>
<p>The combination of habitat destruction, invasive species and climate change has already decimated many Australian species. In 2022, 30 plants and animals were added to the official list of threatened species. </p>
<p>That’s a 43% increase since 2000, bringing the total number to 1,973. Most species added last year were affected by the Black Summer fires.</p>
<p>Our analysis drew on the <a href="https://tsx.org.au">Threatened Species Index</a>, which reports with a three-year time lag. In 2019 the index showed a steady decline of about 3% in the abundance of threatened species each year. This is an overall decline of 62% since 2000. </p>
<p>Threatened plants showed the worst decline (72%), followed by birds (62%) and mammals (33%).</p>
<h2>We can avoid the worst</h2>
<p>Amid the gloom, there are glimmers of hope. Many species feared impacted by the fires proved resilient. Some large new national park areas have been added. Active management is recovering – or at least slowing – the decline of some threatened species, albeit sometimes within the narrow confines of reserves.</p>
<p>Also in 2022, humpback whales were one of the few species in Australian history to be taken off the threatened species list due to a population increase. The species has staged a remarkable recovery since the global moratorium on whaling. </p>
<p>Sadly, there is no fast solution to climate change. Greenhouse gases will linger in the atmosphere for decades to come and further warming is unavoidable. But we can still prevent worse outcomes, by dramatically curbing global emissions.</p>
<p>Australia’s emissions are not falling anywhere near fast enough. They were almost the same in 2022 as in the previous year. And our national emissions remain among the <a href="https://www.sbs.com.au/news/article/interactive-how-australia-compares-to-the-rest-of-the-world-on-co2-emissions/7oooxwnnm">highest</a> in the world per person.</p>
<p>Decisive action is needed. Slowing down habitat destruction, invasive species and climate change is key to preserving our natural resources and species for future generations. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-found-29-threatened-species-are-back-from-the-brink-in-australia-heres-how-200057">We found 29 threatened species are back from the brink in Australia. Here's how</a>
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</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/201778/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Australia’s Environment is produced by the ANU Fenner School for Environment & Society and the Terrestrial Ecosystem Research Network (TERN), an NCRIS-enabled National Research Infrastructure. Albert Van Dijk receives or has previously received funding from several government-funded agencies, grant schemes and programmes.</span></em></p><p class="fine-print"><em><span>Geoff Heard is a current employee of the Terrestrial Ecosystem Research Network (TERN), funded by the National Collaborative Research Infrastructure Strategy. Geoff has previously received funding from several government agencies in Australia for the study and monitoring of threatened species.</span></em></p><p class="fine-print"><em><span>Mark Grant is a current employee of the Terrestrial Ecosystem Research Network (TERN).</span></em></p><p class="fine-print"><em><span>Shoshana Rapley does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Last year was great for plant growth and river flows. But Australia is still on the brink of losing a slew of plant and animal species.Albert Van Dijk, Professor, Water and Landscape Dynamics, Fenner School of Environment & Society, Australian National UniversityGeoffrey Heard, The University of QueenslandMark Grant, Ecosystem Science Programs Lead, Terrestrial Ecosystem Research Network, The University of QueenslandShoshana Rapley, Research assistant, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2003852023-03-07T16:58:23Z2023-03-07T16:58:23ZIntense downpours in the UK will increase due to climate change – new study<figure><img src="https://images.theconversation.com/files/513603/original/file-20230306-24-wp6zsd.jpg?ixlib=rb-1.1.0&rect=502%2C35%2C3718%2C2425&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A flash flood in London in October 2019.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/london-englanduk-october-1-2019-street-1520623391">D MacDonald/Shutterstock</a></span></figcaption></figure><p>In July 2021, Kew in London experienced a month’s rain in <a href="https://www.independent.co.uk/news/uk/home-news/london-flooding-live-today-news-b1883004.html">just three hours</a>. Across the city, tube lines were suspended and stations closed as London experienced its wettest day in decades and flash floods broke out. Just under two weeks later, it happened again: intense downpours led to widespread disruption, including the <a href="https://www.theguardian.com/uk-news/2021/jul/25/thunderstorms-leave-cars-and-buses-stranded-in-london">flooding of two London hospitals</a>. </p>
<p>Colleagues and I have created a new set of 100-year climate projections to more accurately assess the likelihood of heavy rain downpours like these over the coming years and decades. The short answer is climate change means these extreme downpours <a href="https://www.nature.com/articles/s41467-023-36499-9">will happen more often in the UK</a> – and be even more intense.</p>
<p>To generate these projections, we used the Met Office operational weather forecast model, but run on long climate timescales. This provided very detailed climate projections – for every 2.2km grid box over the UK, for every hour, for 100 years from 1981 to 2080. These are much more detailed than traditional climate projections and needed to be run as a series of 20-year simulations that were then stitched together. Even on the Met Office supercomputer, these still took about six months to run.</p>
<p>We ran 12 such 100-year projections. We are not interested in the weather on a given day but rather how the occurrence of local weather extremes varies year by year. By starting the model runs in the past, it is also possible to verify the output against observations to assess the model’s performance.</p>
<p>At this level of detail – the “k-scale” – it is possible to more accurately assess how the most extreme downpours will change. This is because k-scale simulations better represent the small-scale atmospheric processes, such as convection, that can lead to destructive flash flooding.</p>
<figure class="align-center ">
<img alt="The fire service attending to a vehicle stuck in floodwater." src="https://images.theconversation.com/files/513652/original/file-20230306-22-p5sdft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513652/original/file-20230306-22-p5sdft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513652/original/file-20230306-22-p5sdft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513652/original/file-20230306-22-p5sdft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513652/original/file-20230306-22-p5sdft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513652/original/file-20230306-22-p5sdft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513652/original/file-20230306-22-p5sdft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Flash flooding can be destructive.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/treforest-wales-february-2020-fire-tender-1648009474">Ceri Breeze/Shutterstock</a></span>
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<h2>More emissions, more rain</h2>
<p>Our results are now published in <a href="https://www.nature.com/articles/s41467-023-36499-9">Nature Communications</a>. We found that under a high emissions scenario downpours in the UK exceeding 20mm per hour could be four times as frequent by the year 2080 compared with the 1980s. This level of rainfall can potentially produce serious damage through flash flooding, with thresholds like 20mm/hr used by planners to estimate the risk of flooding when water overwhelms the usual drainage channels. Previous less detailed climate models project a much lower increase of around two and a half times over the same period.</p>
<p>We note that these changes are assuming that greenhouse gas emissions continue to rise at current rates. This is therefore a plausible but upper estimate. If global carbon emissions follow a lower emissions scenario, extreme rain will still increase in the UK – though at a slower rate. However, the changes are not inevitable, and if we emit less carbon in the coming decades, extreme downpours will be less frequent.</p>
<p>The increases are significantly greater in certain regions. For example, extreme rainfall in north-west Scotland could be almost ten times more common, while it’s closer to three times more frequent in the south of the UK. The greater future increases in the number of extreme rainfall events in the higher resolution model compared with more traditional lower resolution climate models shows the importance of having k-scale projections to enable society to adapt to climate change.</p>
<p>As the atmosphere warms, it can hold more moisture, at a <a href="https://www.nature.com/articles/nature01092">rate of 7% more moisture</a> for every degree of warming. On a simple level, this explains why in many regions of the world projections show an increase in precipitation as a consequence of human-induced climate change. This new study has shown that, in the UK, the intensity of downpours could increase by about 5% in the south and up to about 15% in the north for every degree of regional warming.</p>
<figure class="align-center ">
<img alt="Group of girls with an umbrella walking through a city." src="https://images.theconversation.com/files/513650/original/file-20230306-1140-kco62o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513650/original/file-20230306-1140-kco62o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513650/original/file-20230306-1140-kco62o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513650/original/file-20230306-1140-kco62o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513650/original/file-20230306-1140-kco62o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513650/original/file-20230306-1140-kco62o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513650/original/file-20230306-1140-kco62o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The projected increase in the intensity of rainfall is significantly greater in certain regions.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/group-girls-hurry-rain-umbrella-city-507316972">NotarYES/Shutterstock</a></span>
</figcaption>
</figure>
<p>However, it is far from a simple picture of more extreme events, decade by decade, as a steadily increasing trend. Instead, we expect periods of rapid change – with records being broken, some by a considerable margin – and periods when there is a pause, with no new records set. </p>
<p>This is simply a reflection of the complex interplay between natural variability and the underlying climate change signal. An analogy for this is waves coming up a beach on an incoming tide. The tide is the long-term rising trend, but there are periods when there are larger waves, followed by lulls.</p>
<p>Despite the underlying trend, the time between record-breaking events at the local scale can be surprisingly long – even several decades.</p>
<p>Our research marks the first time that such a high-resolution data set has spanned over a century. As well as being a valuable asset for planners and policymakers to prepare for the future, it can also be used by climate attribution scientists to examine current extreme rainfall events to see how much more likely they will have been because of human greenhouse gas emissions. The research highlights the importance of meeting carbon emissions targets and also planning for increasingly prevalent extreme rainfall events, which to varying degrees of intensity, look highly likely in all greenhouse gas emissions scenarios.</p>
<p>The tendency for extreme years to cluster poses challenges for communities trying to adapt to intense downpours and risks infrastructure being unprepared, since climate information based on several decades of past observations may not be representative of the following decades.</p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
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<p class="fine-print"><em><span>Elizabeth Kendon receives funding from the joint BEIS/Defra Met Office Hadley Centre climate programme (grant GA01101).</span></em></p>A supercomputer spent six months projecting localised rainfall extremes decades into the future.Elizabeth Kendon, Professor of Climate Science, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2003642023-02-23T17:47:02Z2023-02-23T17:47:02ZWhy the UK has only had one named storm so far this winter – an expert explains<p><a href="https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2023/storm-otto-named-by-danish-met-service#:%7E:text=A%20low%2Dpressure%20system%20which,75mph%20to%20some%20northern%20areas.">Storm Otto</a>, which was named by the Danish Meteorological Institute, hit Scotland and north-east England last Friday (February 17 2023) with wind gusts of over 80mph, disrupting power to 61,000 homes. </p>
<p>Otto was the first named storm of the UK’s current winter storm season and the first to hit the country’s shores since <a href="https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/weather/learn-about/uk-past-events/interesting/2022/2022_01_storms_dudley_eunice_franklin_r1.pdf">storms Dudley, Eunice and Franklin</a> last February. Over the course of a week, these three storms barrelled in from the North Atlantic causing wind and flood damage worth over <a href="https://www.perils.org/losses">€3.7 billion (£3.2 billion) in insured losses</a> across Europe. </p>
<p>The UK has seen only a few notable instances of stormy weather so far this winter. For example, heavy rainfall in the first few weeks of January led to <a href="https://www.itv.com/news/westcountry/2023-01-19/pictures-show-scale-of-flooding-on-somerset-levels">flooding on the Somerset Levels</a>. But this storm was not intense enough to be named. This happens only when a <a href="https://www.metoffice.gov.uk/weather/warnings-and-advice/uk-storm-centre/index">storm has the potential</a> to be severe enough to cause an amber or red warning. </p>
<p>But storms are a common feature of winters in the UK. Since the current naming scheme started in 2016, between five and ten named storms have hit the UK each winter. So what’s been going on with the weather this year and why did the UK wait such a long time between named storms? </p>
<h2>Variable UK weather</h2>
<p>Chance can always play a role, particularly in the case of UK weather. </p>
<p>A narrow band of strong winds in the upper atmosphere, known as the jet stream, steers storms that originate over the North Atlantic towards Europe and the UK. But the jet stream itself is naturally very variable and can shift in position and strength. This can cause the UK’s weather to vary a lot from year to year. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Lg91eowtfbw?wmode=transparent&start=4" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">What is the jet stream and how does it affect our weather?</span></figcaption>
</figure>
<p>The UK has therefore gone long periods without large storms before. For example, the <a href="https://digital.nmla.metoffice.gov.uk/">winter of 1985-86</a> was relatively quiet and was marked by storms at either end of the season with only one strong storm in January.</p>
<h2>La Niña conditions</h2>
<p>A global weather phenomenon called La Niña is also likely to have contributed to this year’s weather. La Niña is one phase of the <a href="https://www.climate.gov/news-features/blogs/enso/what-el-ni%C3%B1o%E2%80%93southern-oscillation-enso-nutshell">El Niño Southern Oscillation</a> and is characterised by relatively cool sea surface temperatures in tropical areas of the Pacific. This winter, sea surface temperatures in the tropical Pacific Ocean have been <a href="https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/">nearly 1°C cooler</a> than average. </p>
<p>La Niña can influence the weather experienced in the northern hemisphere. Cooler sea surface temperatures in the Pacific shift the position of rainfall in the tropics. These changes then propagate into the mid-latitudes, almost like ripples on a pond, and influence the position of the jet stream over the North Atlantic.</p>
<p>The impact of La Niña on weather in the North Atlantic is different in early and late winter. </p>
<p>Early in the season, La Niña tends to <a href="https://journals.ametsoc.org/view/journals/clim/31/11/jcli-d-17-0716.1.xml">shift the jet stream to the south</a>, steering storms that would normally hit the UK towards southern Europe. This may partly explain the bouts of stormy weather that brought flooding to Portugal, Spain and Italy in November and December of 2022. On December 7, <a href="https://www.efas.eu/en/news/floods-portugal-and-spain-december-2022">flash flooding</a> swept through the streets of Lisbon, the capital of Portugal, after 82.3mm of rain fell in 24 hours.</p>
<h2>Sudden stratospheric warming</h2>
<p>Later in the winter season, La Niña tends to shift the jet stream back towards the north and should bring stormier weather to the UK. During a typical winter, cooling air causes a vortex of westerly winds to form in the stratosphere, 10-50km above the Arctic. </p>
<p>The <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/polar-vortex#:%7E:text=What%20is%20the%20Polar%20Vortex,about%20it%20for%20many%20years.">stratospheric polar vortex</a>, as it is called, remains remarkably stable most winters. But some years, the polar vortex slows and breaks up suddenly, causing the stratospheric air over the Arctic to warm rapidly. Called a sudden stratospheric warming, such an event has been occurring since <a href="https://blog.metoffice.gov.uk/2023/02/07/are-we-expecting-a-sudden-stratospheric-warming/">mid-February</a>.</p>
<p>These <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/wind/sudden-stratospheric-warming">sudden stratospheric warmings</a>, and the rapid slow down of the polar vortex, causes the North Atlantic jet stream below to slow down and meander. In some cases, sudden stratospheric warming can create a large area of high pressure over the North Atlantic and Scandinavia, bringing a spell of dry weather to northern Europe. This happened following the last <a href="https://www.rmets.org/metmatters/polar-vortex-sudden-stratospheric-warmings-and-beast-east">sudden stratospheric warming</a> event in January 2021. </p>
<p>But the effect of a sudden stratospheric warming on the UK’s weather can vary. The European blocking associated with sudden stratospheric warming can sometimes bring in freezing air from Europe, increasing the risk of snow. This was the case in late February 2018, where a sudden stratospheric warming drew winds from the Eurasian continent, causing storms and severe snowfall to affect much of the UK – known as the <a href="https://www.rmets.org/metmatters/beast-east-bites-uk">“beast from the east”</a>.</p>
<p>Although the UK might expect some colder weather in the next few weeks, there is no indication in current weather forecasts that this year’s sudden stratospheric warming will lead to the extreme cold weather seen in 2018.</p>
<p>This winter has been less stormy than usual. Yet, the UK relies on rain from North Atlantic storms to refill its rivers, reservoirs and aquifers. This is particularly important this year given last year’s exceptionally hot and dry summer that lead to drought conditions in much of the UK. </p>
<p>Despite only having one named storm, <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1136621/Monthly_water_situation_report_for_England_January_2023.pdf">rainfall across most of the UK</a> has fortunately been around or above average since October. This has helped to replenish water resources. But even then, <a href="https://www.gov.uk/government/news/one-hot-dry-spell-away-from-drought-returning-this-summer-national-drought-group-warns">East Anglia and Cornwall</a> remain in drought. So to top up the UK’s water resources and banish the spectre of a 2023 drought, a few more moderate storms over the next few months would be very welcome.</p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
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<p class="fine-print"><em><span>Len Shaffrey receives funding from the Natural Environment Research Council and the European Commission's Horizon Europe funding scheme.</span></em></p>An expert explains why the UK’s winter has been relatively calm.Len Shaffrey, Professor of Climate Science, National Centre for Atmospheric Science, University of ReadingLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1988122023-02-22T15:32:01Z2023-02-22T15:32:01ZRock art as African history: what religious images say about identity, survival and change<figure><img src="https://images.theconversation.com/files/510268/original/file-20230215-15-yt0qm3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">After colonial contact, indigenous Africans acquired horses and guns, and raided settlers as a means of resistance.</span> <span class="attribution"><span class="source">Courtesy Sam Challis</span></span></figcaption></figure><p>To “read” the history of times before writing, scholars have traditionally used excavated evidence. Remains like dwellings, burials and pots can reveal a lot about how people lived long ago. In southern Africa, there is another archive to “read” too: rock art. Rock art is primarily a record of spiritual beliefs – but also reflects the events that these beliefs made sense of.</p>
<p>Hunter-gatherers in the region, ancestors of today’s San or BaTwa, made rock art for thousands of years before African herders and farmers arrived from the north 2,000 years ago and European colonists followed by sea 350 years ago.</p>
<p>As a result of these contacts between groups of people, ethnic and economic boundaries became increasingly blurred. Rock art changed too, in technique and subject matter.</p>
<p>Rock art tells a tale of people meeting, negotiating, fighting, trading with and marrying one another. The tale is told not in simple narrative, but in spiritual beliefs. Our recent <a href="https://www.journals.uchicago.edu/doi/10.1086/722260">paper in Current Anthropology</a> outlines the nature, scale and effects of contact between people in southern Africa, and the ways in which indigenous people produced images that engaged with change. It shows that contact and colonisation, in time, created a “disconnect” with the past that can be understood by looking at changes in rock art. </p>
<p>The disconnect apparent in the rock art reflects the disconnect in indigenous society more generally. It reveals the mixing and changing – and survival – of different people’s beliefs about the universe. It charts southern African history and, although it is “written” in terms of spiritual beliefs, it is the only record that shows what happened from the San perspective.</p>
<p>It often shows the struggle to resist subjugation, and it depicts beliefs about the forces that could be summoned to resist.</p>
<h2>Shifts in rock art</h2>
<p>What the San painted or engraved on rock was their vision of what happened in a trance state. The artists entered this trance state in order to establish <a href="https://www.mdpi.com/2077-1444/12/12/1099">connections with animals and spirits in the landscape</a>, to influence their movements, and to derive the power to make rain and heal the sick. </p>
<p>Rock art was never unchanging, but new traditions and styles appeared when African farmers arrived in southern Africa from about 2,000 years ago, and when pastoralism was later introduced. Further changes came with the <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0134215">arrival of Khoe-speakers about 1,000 years ago</a>. These Khoe-speaking herders were themselves descended from earlier mixing between hunter-gatherers and east African pastoralists.</p>
<p>Changes appeared in the rock art’s content – for example the animals and materials portrayed – and in the artistic techniques used.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507048/original/file-20230130-24-3evymd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two images of antelope painted on rock surface" src="https://images.theconversation.com/files/507048/original/file-20230130-24-3evymd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507048/original/file-20230130-24-3evymd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=180&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507048/original/file-20230130-24-3evymd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=180&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507048/original/file-20230130-24-3evymd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=180&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507048/original/file-20230130-24-3evymd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=226&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507048/original/file-20230130-24-3evymd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=226&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507048/original/file-20230130-24-3evymd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=226&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Eland antelope, painted (probably) before and after contact between San and other groups.</span>
<span class="attribution"><span class="source">Courtesy of Sam Challis</span></span>
</figcaption>
</figure>
<p>Eland antelope (the one with the most spiritual power for the San) were once lovingly drafted and shaded. Later they appeared in bright, chalky and vivid colours, rendered in a posterlike and blocky fashion. The drop in pigment quality was likely due to the breakdown of trade networks brought about by marginalisation, then <a href="https://www.researchgate.net/publication/262547793_The_forgotten_killing_fields_San_genocide_and_Louis_Anthing's_mission_to_Bushmanland_1862-1863">slaughter</a>, of indigenous people, but still they called on the power of the eland to help them. </p>
<p>We see pictures of cattle and sheep appearing in rock art, and finger-painted and engraved patterns associated with girls’ initiation, common to pastoralist and hunter-gatherer societies. The images show that people’s identity (ethnicity) and the way they survived (economy) weren’t divided into clear groups. Hunters were not necessarily all San, and all San were not necessarily hunters. The blurring of boundaries between groups increased with time. </p>
<p>As time went on, all these people became subject to extermination policy, slavery and marginalisation. But rather than being passive receptors of change, they used their religion, comprising multicultural beliefs, to survive. This can be seen in the rock art they created.</p>
<h2>Spiritual concepts of water</h2>
<p>Conceptions of the rain, in the form of images of water bulls and water snakes, are particularly useful for examining cross-cultural influences. </p>
<p>For African farmers, snakes were associated with water. Hunter-gatherers and herders with whom they came into contact acknowledged this because they, too, already had beliefs about water and the animal entities embodied by it. </p>
<p>People from different language groups may have gathered together for girls’ initiation ceremonies at sites where the great water snake emerged. At these locations, this spiritual creature’s body, the <a href="http://www.driekopseiland.itgo.com/">undulating rock</a>, is covered with markings to appeal to it – the markings that also appear on the initiates’ tattoos, face paint, clothing and bags. </p>
<p>The control of water, to make rain for pasture and crops, was traded (bartered for cattle) between groups, very likely for centuries. Rock art images of water snakes, water bulls and domestic cattle intertwine and superimpose one another; sometimes water snakes have cattle horns. Often, water bulls or water snakes were depicted being killed to make their blood – the rain – fall. </p>
<p>Water was also extremely important to those wishing to combat the encroaching colonists. By this time the people of southern Africa, regardless of background, held many <a href="https://www.researchgate.net/publication/280623580_Binding_beliefs_the_creolisation_process_in_a_%27Bushman%27_raider_group_in_nineteenth-century_southern_Africa">beliefs in common</a>. The people or entities that lived underwater could be called upon to influence situations: torrential rain to wash away the tracks of stolen animals, for example. </p>
<h2>Raiding and escape</h2>
<p>By the time colonists arrived, hunter-gatherers had sheep, and <a href="https://dsae.co.za/entry/sintu/e06478">isiNtu-speakers</a> (African farmers) had adopted aspects of hunter-gatherer beliefs, and vice versa. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/510269/original/file-20230215-4182-kb2qti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Painted image of human with some animal features" src="https://images.theconversation.com/files/510269/original/file-20230215-4182-kb2qti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/510269/original/file-20230215-4182-kb2qti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=580&fit=crop&dpr=1 600w, https://images.theconversation.com/files/510269/original/file-20230215-4182-kb2qti.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=580&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/510269/original/file-20230215-4182-kb2qti.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=580&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/510269/original/file-20230215-4182-kb2qti.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=729&fit=crop&dpr=1 754w, https://images.theconversation.com/files/510269/original/file-20230215-4182-kb2qti.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=729&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/510269/original/file-20230215-4182-kb2qti.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=729&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Xhosa warrior painted in the Windvogelberg mountains of the Eastern Cape, possibly as a ‘commission’ including war medicine obtained from the San.</span>
<span class="attribution"><span class="source">Courtesy of Brent Sinclair-Thomson</span></span>
</figcaption>
</figure>
<p>San were increasingly marginalised from well-watered pasture suitable for domestic herds of African herders and farmers. Some became herders themselves, some mixed with farmers and some became raiders. Then, with the expansion of settler farms in the 18th century (which they also raided) they were <a href="https://theconversation.com/south-africas-bandit-slaves-and-the-rock-art-of-resistance-165107">decimated, hunted and enslaved</a>.</p>
<p>In the rock art, baboons became a symbol of protective power to enable raiders to escape unharmed. The root of a powerful medicine, <em>so-|oa</em> or <em>mabophe</em> – closely associated with baboons – enabled stock thieves to pass unnoticed, and “<a href="https://www.tandfonline.com/doi/abs/10.1080/15740773.2017.1487122">turned bullets to water</a>”. We see this in the paintings of people taking on the power and features of baboons, appearing alongside horses and cattle.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/south-africas-bandit-slaves-and-the-rock-art-of-resistance-165107">South Africa's bandit slaves and the rock art of resistance</a>
</strong>
</em>
</p>
<hr>
<p>Horses, the magical vehicles of violence, passage and escape, were kept and cared for by their new owners – the raider groups. They painted themselves in scenes before, during and after raids, not as a diary entry but as part of the [<a href="https://www.researchgate.net/profile/Sam-Challis/publication/280623828_Re-tribe_and_resist_the_ethnogenesis_of_a_creolised_raiding_band_in_response_to_colonisation/links/5efb0cf6299bf18816f37af0/Re-tribe-and-resist-the-ethnogenesis-of-a-creolised-raiding-band-in-response-to-colonisation.pdf">ritual</a>] of ensuring the outcome was favourable and the memory made positive. </p>
<p>We can now see changes in rock art, from “traditional” animals like rhebok and eland, to those showing rain bulls being killed, rain snakes captured, people with shields and spears, or riding horses alongside baboons, <a href="https://www.journals.uchicago.edu/doi/10.1086/722260">in a new light</a>.</p><img src="https://counter.theconversation.com/content/198812/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sam Challis receives funding from the South African NRF African Origins Platform and is a member of the Bradshaw Foundation Rock Art Network</span></em></p><p class="fine-print"><em><span>Brent Sinclair-Thomson received funding for this research from the South African National Research Foundation African Origins Platform. </span></em></p>Changes in southern African rock art reflect the mixing of groups of people after they came into contact with each other.Sam Challis, Senior Researcher, University of the WitwatersrandBrent Sinclair-Thomson, Support staff, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1971682023-01-06T13:32:37Z2023-01-06T13:32:37ZHow California could save up its rain to ease future droughts — instead of watching epic atmospheric river rainfall drain into the Pacific<figure><img src="https://images.theconversation.com/files/503361/original/file-20230105-24-8a0umi.jpg?ixlib=rb-1.1.0&rect=0%2C16%2C5472%2C3620&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Heavy rain from a series of atmospheric rivers flooded large parts of California from late December 2022 into early January 2023.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/view-of-highway-101-flooding-in-south-san-francisco-as-news-photo/1245913492">Tayfun Coskun/Anadolu Agency via Getty Images</a></span></figcaption></figure><p>California has seen <a href="https://www.washingtonpost.com/weather/2023/01/01/san-francisco-flooding-rainfall-record/">so much rain</a> over the past few weeks that farm fields are inundated and normally dry creeks and drainage ditches have become torrents of water racing toward the ocean. Yet, most of the state <a href="https://droughtmonitor.unl.edu/data/png/20230103/20230103_west_text.png">remains in drought</a>.</p>
<p>All that runoff in the middle of a drought begs the question — why can’t more rainwater be collected and stored for the long, dry spring and summer when it’s needed?</p>
<p>As a <a href="https://eps.ucsc.edu/faculty/Profiles/fac-only.php?uid=afisher">hydrogeologist</a> at the University of California at Santa Cruz, I’m interested in what can be done to collect runoff from storms like this on a large scale. There are two primary sources of large-scale water storage that could help make a dent in the drought: holding that water behind dams and putting it in the ground.</p>
<h2>Why isn’t California capturing more runoff now?</h2>
<p>When California gets storms like the <a href="https://earthobservatory.nasa.gov/images/150804/atmospheric-river-lashes-california">atmospheric rivers</a> that hit in December 2022 and January 2023, water managers around the state probably shake their heads and ask why they can’t hold on to more of that water. The reality is, it’s a complicated issue.</p>
<p>California has <a href="https://cdec.water.ca.gov/resapp/RescondMain">big dams and reservoirs</a> that can store large volumes of water, but they tend to be in the mountains. And once they’re near capacity, water has to be released to be ready for the next storm. Unless there’s another reservoir downstream, a lot of that water is going out to the ocean.</p>
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<figcaption><span class="caption">A video captures flooding from record rainfall on the last weekend of 2022.</span></figcaption>
</figure>
<p>In more populated areas, one of the reasons storm water runoff isn’t automatically collected for use on a large scale is because the first runoff from roads is <a href="https://doi.org/10.1007/s00244-021-00906-3">often contaminated</a>. Flooding can also cause <a href="https://www.bio-sol.ca/blog/en/septic-system-during-heavy-rain/">septic system overflows</a>. So, that water would have to be treated.</p>
<p>You might say, well, the captured water doesn’t have to be drinking water, we could just use it on golf courses. But then you would need a place to store the water, and you would need a way to distribute it, with separate pipes and pumps, because you can’t put it in the same pipes as drinking water.</p>
<h2>Putting water in the ground</h2>
<p>There’s another option, and that’s to put it in the ground, where it could help to replenish groundwater supplies.</p>
<p>Managed recharge has been used for decades in <a href="http://www.fresnofloodcontrol.org/groundwater-recharge/">many areas</a> to actively replenish groundwater supplies. But the techniques have been gaining more attention lately as wells run dry amid the long-running drought. Local agencies have proposed more than <a href="https://resources.ca.gov/-/media/CNRA-Website/Files/Initiatives/Water-Resilience/CA-Water-Supply-Strategy.pdf">340 recharge projects</a> in California, and the state estimates those could recharge an additional 500,000 <a href="https://www.watereducation.org/general-information/whats-acre-foot">acre-feet</a> of water a year on average if all were built.</p>
<p>One method being discussed by the state Department of Water Resources and others is <a href="https://water.ca.gov/programs/all-programs/flood-mar">Flood-MAR, or flood-managed aquifer recharge</a>. During big flows in rivers, water managers could potentially divert some of that flow onto large parts of the landscape and inundate thousands of acres to recharge the aquifers below. The concept is to flood the land in winter and then farm in summer.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/502983/original/file-20230103-64877-pfntf2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Illustration showing different techniques with fields flooded in different ways" src="https://images.theconversation.com/files/502983/original/file-20230103-64877-pfntf2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502983/original/file-20230103-64877-pfntf2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=737&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502983/original/file-20230103-64877-pfntf2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=737&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502983/original/file-20230103-64877-pfntf2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=737&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502983/original/file-20230103-64877-pfntf2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=926&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502983/original/file-20230103-64877-pfntf2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=926&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502983/original/file-20230103-64877-pfntf2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=926&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Flood-managed aquifer recharge methods.</span>
<span class="attribution"><a class="source" href="https://water.ca.gov/programs/all-programs/flood-mar">California Department of Water Resources</a></span>
</figcaption>
</figure>
<p>Flood-MAR is promising, provided we can find people who are willing to inundate their land and can secure water rights. In addition, not every part of the landscape is prepared to take that water.</p>
<p>You could inundate 1,000 acres on a ranch, and a lot of it might stay flooded for days or weeks. Depending on how quickly that water soaks in, some crops will be OK, but other crops could be harmed. There are also concerns about creating habitat that encourages pests or risks food safety.</p>
<p>Another challenge is that most of the big river flows are in the northern part of the state, and many of the areas experiencing the <a href="https://www.ppic.org/publication/groundwater-recharge/">worst groundwater deficits</a> are in central and southern California. To get that excess water to the places that need it requires transport and distribution, which can be complex and expensive.</p>
<h2>Encouraging landowners to get involved</h2>
<p>In the Pajaro Valley, an important agricultural region at the edge of Monterey Bay, regional colleagues and I are trying <a href="https://www.youtube.com/watch?v=U_BtWaM3SC4">a different type of groundwater recharge project</a> where there is a lot of runoff from hill slopes during big storms.</p>
<p>The idea is to siphon off some of that runoff and divert it to infiltration basins, occupying a few acres, where the water can pool and percolate into the ground. That might be on agricultural land or open space with the right soil conditions. We look for coarse soils that make it easier for water to percolate through gaps between grains. But much of the landscape is covered or underlain by finer soils that don’t allow rapid infiltration, so careful site selection is important.</p>
<p>One program in the Pajaro Valley encourages landowners to participate in recharge projects by giving them a rebate on the fee they pay for water use through a “<a href="https://www.uctv.tv/shows/Recharge-Net-Metering-ReNeM-36130">recharge net metering</a>” mechanism.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/7ZPKqqa6cas?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How recharge net metering works.</span></figcaption>
</figure>
<p>We did a cost-benefit analysis of this approach and found that even when you add in all the capital costs for construction and hauling away some soil, the costs are competitive with finding alternative supplies of water, and it is cheaper than desalination or water recycling.</p>
<h2>Is the rain enough to end the drought?</h2>
<p>It’s going to take many methods and several wet years to make up for the region’s long period of low rainfall. One storm certainly doesn’t do it, and even one wet year doesn’t do it.</p>
<p>For basins that are dependent on groundwater, the recharge process takes years. If this is the last rainstorm of this season, a month from now we could be in trouble again.</p><img src="https://counter.theconversation.com/content/197168/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Funding: U.S. National Science Foundation, U.S. Department of Agriculture, National Aeronautics and Space Administration, Gordon and Betty Moore Foundation, Santa Clara Valley Water District, U.S. Geologic Survey
Affiliation: Research Network with the Public Policy Institute of California</span></em></p>Urban infrastructure was designed to take stormwater out to the ocean quickly. Now, California needs that precious water.Andrew Fisher, Professor of Earth and Planetary Sciences, University of California, Santa CruzLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1962962022-12-14T13:22:12Z2022-12-14T13:22:12ZSacred rivers: Christianity in southern Africa has a deep history of water and ritual<figure><img src="https://images.theconversation.com/files/499972/original/file-20221209-25133-n77srn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A baptism ceremony in the Mbashe river in South Africa's Eastern Cape province.</span> <span class="attribution"><span class="source">CARL DE SOUZA/AFP via Getty Images</span></span></figcaption></figure><p>Water is a scarce commodity in much of Africa, particularly in southern Africa. This is well symbolised in the name of the Botswana national currency, pula (rain). When tragedies like <a href="https://ewn.co.za/2022/12/08/alex-community-members-demand-answers-over-jukskei-river-drownings">flooding and drowning</a> take place, it may seem inappropriate to speak of the scarcity and commodity of water. For example, members of the <a href="https://dacb.org/stories/zimbabwe/johane-masowe/">Johane Masowe</a> church drowned in a flash flood during a baptismal ceremony at a river in South Africa recently. </p>
<p>But part of the attraction of moving bodies of water to religious groups may be rooted in this very scarcity. Whatever is scarce is also precious and whatever is precious might be termed sacred. Religions by whatever name venerate the sacred. Think, for example, of places like the city of Jerusalem, which has sacred status in Judaism, Islam and Christianity. Or think of Mecca for Islam, or the River Ganges in Hinduism. </p>
<p>Religious adherents are drawn to sacredness, and they often go to great lengths to be close to it. Pilgrimages in all the religions of the world are based on this principle, including <a href="https://www.routledge.com/African-Pilgrimage-Ritual-Travel-in-South-Africas-Christianity-of-Zion/Muller/p/book/9781032099224">African pilgrimage</a>. Holy sites like Zion City Moria is a principal pilgrimage destination for members of the Zion Christian Church in South Africa, for example. </p>
<p>Another characteristic of the sacred is that it can be dangerous. It is not for idle reasons that the “fear of God” is a well-trodden theme in biblical literature. Readers are encouraged to be cautious of the sacred. </p>
<p>Most <a href="https://zuidafrika.nl/arts-culture/religions/">religious groups in southern Africa</a> are broadly Christian, drawing on a common pool of biblical knowledge in constructing their rituals and spirituality. Throughout the Bible, the miraculous nature of rain and water is emphasised. In one passage Moses secures life-giving water by striking a rock with his staff. In another the prophet Elijah illustrates his divinely sanctioned role by praying successfully for rain at Mount Carmel. In the Christian New Testament, Jesus walks on the water of the sea of Galilee, illustrating his sacred power. When his disciple Peter attempts to copy the act, his fear proves greater and he must be saved. In another instance Jesus shows his submission to the sacred by being baptised in the River Jordan.</p>
<p>Water baptism has been a central rite in the Christian church since antiquity. Over the centuries it became institutionalised as a once off ritual administered to church members either at infancy or at a later stage upon their confession of faith. </p>
<p>Different church groups have battled over which form of baptism is the theologically more correct option – infant baptism or the baptism of confessing adults. But in more recent times, especially in many African Christian communities, a completely new version of the ritual has arisen. This is where a church group conducts not only once off baptisms of new members but also subsequent baptism-like rituals at natural bodies of water at specific occasions for a variety of reasons. </p>
<h2>Ancient spiritual rituals</h2>
<p>In conducting rituals connected to water, African Christian churches often also tap into ancient remnants of spirituality that have existed in these regions for thousands of years. I have written about this as instances of <a href="http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2074-77052008000300012">religious hybridity</a>. </p>
<p>The <a href="http://www.san.org.za/history.php">San</a> people of southern Africa were known to conduct “rainmaking” rituals at <a href="https://www.nbcnews.com/news/all/shaman-rainmaking-center-discovered-south-africa-flna6c10144950">special sites for many centuries</a>. Rain rituals are still at the forefront of especially rural spiritualities. <a href="https://www.sahistory.org.za/dated-event/rain-queen-makobo-modjadji-vi-dies-after-sudden-illness">Modjadji, the rain queen</a>, is perhaps the best-known ritual specialist in the northern part of South Africa. There have been many other lesser-known ritual specialists with similar rain and water-related roles throughout southern and central Africa. For example, the anthropologist Penelope Bernard has written about “living water” in <a href="http://www.jstor.org/stable/43809484">South African Nguni healing traditions</a>. In these divine-healing traditions mythical underwater snakes or mermaids are mentioned in connection with sacred water.</p>
<p>When Christian missionaries first attempted to establish themselves among such communities, they often encountered questions about their ability or inability to bring rain. Often their own position as bearers of good news was accepted only after they had prayed, and <a href="https://brill.com/view/journals/exch/46/1/article-p29_3.xml?language=en">rains had fallen</a>. Successes for Christian missionaries occurred when <a href="http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2074-77052021000200008">powerful rain ritualists occasionally converted to Christianity</a>. Such rain specialists often went to special sites to perform their rituals, often at or near pools of water. </p>
<p>In pre-Christian tradition certain mythical animals were often associated with such places, typically snakes, as mentioned above, which were believed to have mythical and spiritual connotations. Nyami Nyami, the Zambezi river god, is perhaps the best known of such entities in the region. </p>
<p>When ordinary people go to visit apparently ordinary water sites they may well be on a sacred journey. Tragedies, when they occur, should be mourned, but the practice of water rituals should not be condemned. Water is life, after all, and therefore sacred.</p><img src="https://counter.theconversation.com/content/196296/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Retief Müller does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Water is sacred in many religious traditions, holding power that can also be dangerous.Retief Müller, Associate Professor in Theology, VID Specialized UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1943802022-11-16T16:00:18Z2022-11-16T16:00:18ZFive things you probably have wrong about rain<figure><img src="https://images.theconversation.com/files/494741/original/file-20221110-14-bfiwuz.jpg?ixlib=rb-1.1.0&rect=10%2C40%2C6698%2C4425&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">UK weather can often be on the damp side</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/trip-bad-weather-portrait-young-man-1470502973">Jaromir Chalabala/Shutterstock</a></span></figcaption></figure><p>There’s been so much rain over the last few weeks it’s hard to believe much of the UK is in drought. Even as people trudge home drenched to the skin there are still hosepipe bans in place. After another record-breaking hot summer, UK reservoirs are still well below normal levels. In 2022 so far, the south of England has had 20% less rain than average. </p>
<p>Talking about the weather may be a national pastime. But there are things even British people may not know about rain. </p>
<h2>1. Rain drops aren’t tear shaped</h2>
<p>The small ones (about 1mm, the thickness of a credit card) are spherical. The larger rain drops are <a href="https://www.sciencedirect.com/science/article/pii/S0169809510000736?via%3Dihub">the more they flatten</a> until they are the shape of a burger bun (flat side down). When they become larger than 5mm, about the size of a pencil top rubber, they break into smaller drops. </p>
<p>The shape is created by the interaction between two forces: the surface tension of water and the pressure caused by the drop falling through air. Surface tension forces the drop into a form with the smallest possible surface area, a sphere. This is the dominant force on small rain drops because less air needs to be pushed aside than with larger drops. </p>
<p>Bigger drops expose a larger area to the air and fall faster, making the pressure effect greater. This squashes the bottom of the drop, causing that side to flatten. This pressure creates a dip, a carrier bag shape and eventually breaks up the drop.</p>
<p>Shape is important because it affects <a href="https://core.ac.uk/download/pdf/42771659.pdf">electro-magnetic signals</a> passing through rain. It also gives forecasting technology extra information about what weather to expect. The latest technologies are improving the measurement of rainfall using the shape information and could improve flash flood forecasts. </p>
<h2>2. The UK isn’t as wet as people think</h2>
<p>Globally, average rainfall is around 1,000mm per year. Britain, is just a bit above this, with 1,150mm – but the south east has far less. </p>
<p>There’s <a href="https://www.metoffice.gov.uk/pub/data/weather/uk/climate/averages/maps/uk/9120_1km/Rainfall_Average_1991-2020_17.gif">huge variation across the UK</a> with less than 550mm around <a href="https://www.metoffice.gov.uk/research/climate/maps-and-data/uk-climate-%20averages/u10t6ch7u">the Thames estuary</a>, but over 3,000mm in the hills of western Scotland and well over 2,000mm in the Welsh mountains and <a href="https://www.metoffice.gov.uk/research/climate/maps-and-data/uk-climate-averages/gctvssktt">Lake District</a>. The west is much wetter than the east. But the effects of hills makes a massive difference. Air rising over hills and mountains <a href="https://www.theguardian.com/news/2021/oct/20/weatherwatch-orographic-rain-and-the-seeder-feeder-process">generates extra water</a> so flat areas are often less rainy. </p>
<p>Worldwide there are deserts with almost no rainfall and tropical areas that get enormous amounts of rain. The Indian state of Mawsynram has almost 12,000mm of rain per year.</p>
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<p><a href="https://www.metoffice.gov.uk/research/climate/maps-and-data/uk-climate-averages/u10hb54gm">Greenwich Observatory</a>, London gets 562mm per year on average. That’s less than <a href="https://www.metoffice.gov.uk/weather/travel/holiday-weather/europe/malta">Malta</a> (592mm) and <a href="https://www.metoffice.gov.uk/weather/travel/holiday-weather/europe/italy/rome">Rome</a> (586mm) and very similar to <a href="https://www.metoffice.gov.uk/weather/travel/holiday-weather/europe/spain/barcelona">Barcelona</a> (520mm). London’s rain is about half of the annual average of <a href="https://www.metoffice.gov.uk/weather/travel/holiday-weather/australasia/australia/sydney">Sydney</a> (1,222mm) or <a href="https://www.metoffice.gov.uk/weather/travel/holiday-weather/americas">Orlando or New York</a> (1,175mm and 1,059mm respectively). </p>
<p>Britain tends to get more light rain and drizzle. More rainy days, but less water overall. </p>
<p>Slight rain is <a href="https://water.usgs.gov/edu/activity-howmuchrain-metric.html">less than 0.5 mm per hour</a> while a heavy shower is more than 10mm an hour.</p>
<h2>3. We’ve measured rain for thousands of years</h2>
<p>Rain gauges were one of the <a href="https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/wea.548">first scientific instruments</a>. People from modern India were using them around 2,500 years ago. They were standardised in 1441, when King Sejong in Korea sent a rain gauge to every village to measure farmers’ potential harvests and set tax rates. The <a href="https://www.youtube.com/watch?v=JVOxLrMaWA8">tipping bucket gauge</a>, a tube shaped container with a funnel was invented in 1662 by two titans of science, Christopher Wren and Robert Hooke. While a standard gauge has to be read by a human operator the tipping bucket is partially automated. The originals were powered with clockwork cogs and a pen moved slowly over paper to make a record of rainfall rate. </p>
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<p>The standard rain gauge used all over the world today is virtually identical <a href="https://research.reading.ac.uk/meteorology/atmosphericobservatory/atmospheric-observatory-%20data/">to the one created in 1441</a>. </p>
<p>The rain gauge can measure only at the exact place it is installed. Rainfall can be different just metres away. </p>
<p>Rain is also measured by radar across much of the world. The radars in the UK measure up to 250km from the site in all directions. The network (comprised of a total of 18 radar across the UK and Ireland) provides rainfall rate estimates in 1km squares every five minutes telling us about rain anywhere, rather than just at the specific location of a rain gauge. However the rain gauge is critical for the climate record and as it has been the standard measurement across the world for so long. </p>
<h2>4. Most rain in the UK is actually melted snow</h2>
<p>When we see rain, it has fallen from several kilometres above us. Much precipitation forms at heights where it is below freezing. The <a href="https://glossary.ametsoc.org/wiki/Bergeron-findeisen_process">ice that clouds are made of</a> create rain. </p>
<p>Warm rain, where the process happens in temperatures above freezing, is unusual in the UK but not in the tropics. When ice reaches air warmer than 0⁰C it starts to melt. The level at which it melts on its journey down to us can vary from the ground to about 4km.</p>
<p>This is why predicting snow in the UK is complicated. In much of the world, snow falls at much colder temperatures. If it’s -5°C outside a 2°C temperature error makes no difference. In the UK most snow falls when air temperatures are close to 0⁰C. A small difference in temperature, 2°C degrees, will change whether there is is rain, sleet (melting snow) or snow.</p>
<h2>5. Drop size matters</h2>
<p>Look carefully a car windscreen during rain and you can see that the spots landing are of different sizes.</p>
<p>Rain is made of drops of various sizes, from less than 1mm to drops over 5mm in size, the heavier the rain, the more large drops (but little change on the number of the smallest ones). Drizzle tends to have a different character, with lots of tiny drops (less than 1mm across). You may also notice the first sign of rain in heavy showers is a sparse pattering of huge rain drops. That’s because the large drops fall faster than small drops, so reach the ground first.</p>
<p>Drop size affects the strength of mobile phone and TV signals and similar <a href="https://science.nasa.gov/ems/01_intro">electromagnetic waves</a>. More energy is lost to large drops. This leads to weaker signals, potentially even drop outs if the rain is heavy enough. But meteorologists can use drop size to detect the intensity of rainfall.</p>
<p>Next time it rains look out of the window. Go outside and feel it fall on your skin, marvel at the physics as it happens around you. It might even take your mind off the damp weather.</p><img src="https://counter.theconversation.com/content/194380/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rob Thompson receives and has received funding from NERC and ESA for research into rainfall. </span></em></p>On average, Sydney and Rome get more rain than London each year.Rob Thompson, Postdoctoral Research Scientist in Meteorology, University of ReadingLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1920182022-11-16T04:21:47Z2022-11-16T04:21:47ZRain makes coal heavy, slippery and harder to dig up. So what does La Niña mean for this already disrupted industry?<figure><img src="https://images.theconversation.com/files/495541/original/file-20221116-20-7ad2yy.jpg?ixlib=rb-1.1.0&rect=8%2C16%2C5455%2C3620&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Kelly Barnes/AAP</span></span></figcaption></figure><p>As the La Niña weather event wreaks havoc across New South Wales, coal operators are suffering. The Australian coal company Whitehaven is among them – last week <a href="https://www.smh.com.au/business/companies/australian-coal-miner-hit-by-climate-change-chaos-20221109-p5bwps.html">slashing</a> its production forecasts after disruption by floods and heavy rain.</p>
<p>The irony of a coal company being hit by extreme weather events was <a href="https://www.smh.com.au/business/companies/australian-coal-miner-hit-by-climate-change-chaos-20221109-p5bwps.html">not lost</a> on some. While it’s hard to know how climate change is influencing this La Niña, evidence <a href="https://theconversation.com/climate-change-will-clearly-disrupt-el-nino-and-la-nina-this-decade-40-years-earlier-than-we-thought-194529">suggests</a> flood events will become more frequent and intense as the planet warms.</p>
<p><a href="https://science.nasa.gov/earth-science/oceanography/ocean-earth-system/climate-variability">Climate variations</a> cause problems for many industries, and coal is not immune. Wet coal is heavier to transport. And rain can disrupt both mine operations and the transport networks crucial to moving coal and mine workers.</p>
<p>All this comes as coal demand surges, and as pressure mounts for the industry to wind back production to help tackle climate change. So let’s look at what the industry faces in these turbulent times.</p>
<figure class="align-center ">
<img alt="truck in piles of coal" src="https://images.theconversation.com/files/495566/original/file-20221116-24-yjn9z8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495566/original/file-20221116-24-yjn9z8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495566/original/file-20221116-24-yjn9z8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495566/original/file-20221116-24-yjn9z8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495566/original/file-20221116-24-yjn9z8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495566/original/file-20221116-24-yjn9z8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495566/original/file-20221116-24-yjn9z8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">As the La Niña weather event wreaks havoc across New South Wales, coal operators are suffering.</span>
<span class="attribution"><span class="source">Dave Hunt/AAP</span></span>
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<h2>Rain on the coal parade</h2>
<p>Australia is the world’s second-biggest thermal coal exporter, behind Indonesia. Our shipments mostly <a href="https://www.worldstopexports.com/coal-exports-country/">end up</a> in Japan, India, Vietnam and South Korea.</p>
<p>Thermal coal is burnt to make electricity. Australia also produces metallurgical or “coking” coal used to make steel. </p>
<p>In recent years, extreme weather in Australia has exposed the coal industry’s vulnerability to climate risk. </p>
<p>Research <a href="https://www.researchgate.net/publication/323357165_Adapting_to_climate_risks_and_extreme_weather_A_guide_for_mining_and_minerals_industry_professionals">shows</a> the 2010/2011 Queensland floods affected about 40 of the state’s 50 coal mines, costing more than A$2 billion in lost production. </p>
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Read more:
<a href="https://theconversation.com/climate-change-will-clearly-disrupt-el-nino-and-la-nina-this-decade-40-years-earlier-than-we-thought-194529">Climate change will clearly disrupt El Niño and La Niña this decade – 40 years earlier than we thought</a>
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<p>Australia is now experiencing more heavy rain thanks to a third consecutive La Niña. It led to <a href="https://www.abc.net.au/news/2021-12-08/workers-stood-down-no-pay-central-qld-mine/100682812">floods in Queensland</a> last year that forced the Baralaba North Coal Mine to suspend operations after water affected the mine and access roads. Workers were stood down without pay, prompting anger from the union. </p>
<p>In the NSW Hunter Valley, heavy rain in July this year <a href="https://www.afr.com/companies/transport/newcastle-coal-prices-soar-after-rail-tracks-flooded-20220708-p5b03v">forced closures</a> to a rail network that connects about 40 coal mines to the Port of Newcastle. Coal export services were suspended and the disruption pushed up coal prices.</p>
<p>Heavy rain is likely to interrupt supply for the remainder of spring and into summer. Last week, Whitehaven said rain and local flooding <a href="https://www.smh.com.au/business/companies/australian-coal-miner-hit-by-climate-change-chaos-20221109-p5bwps.html">were affecting production</a> at two open-cut mines near Gunnedah in NSW. Roads were cut off as dams and rivers near the mine spilled over, forcing the company to transport staff to the mine by helicopter.</p>
<p>Rain can bring other problems. Wet coal can <a href="https://usea.org/sites/default/files/122012_Losses%20in%20the%20coal%20supply%20chain_ccc212.pdf">slip</a> and spill from conveyor belts while being loaded onto ships. And wet coal is heavy, making it more expensive to transport. </p>
<figure class="align-center ">
<img alt="coal train rounds a bend" src="https://images.theconversation.com/files/495567/original/file-20221116-16-8me7a6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495567/original/file-20221116-16-8me7a6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495567/original/file-20221116-16-8me7a6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495567/original/file-20221116-16-8me7a6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495567/original/file-20221116-16-8me7a6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495567/original/file-20221116-16-8me7a6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495567/original/file-20221116-16-8me7a6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Australia’s coal industry relies on rail links that can be disrupted in heavy rain.</span>
<span class="attribution"><span class="source">Dan Himbrechts/AAP</span></span>
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<h2>Volatile times for coal</h2>
<p>Australian coal exports <a href="https://tradingeconomics.com/australia/exports-of-coal-coke-briquettes#:%7E:text=Exports%20of%20%2D%20Coal%2C%20Coke%20%26%20Briquettes%20in%20Australia%20averaged%201652.19,Million%20in%20August%20of%201971">remain strong</a>. But the rain disruptions add to already unsettled times for coal, both here and abroad.</p>
<p>Demand for coal has increased in the past two years, for a number of reasons. First is the global economic <a href="https://www.iea.org/reports/coal-market-update-july-2022/demand">rebound</a> from the COVID pandemic. Second is soaring gas prices <a href="https://www.cnbc.com/2022/10/21/asias-energy-supply-is-secure-even-as-europe-scrambles-analysts-say.html">following</a> Russia’s war on Ukraine. </p>
<p><a href="https://oilprice.com/Energy/Energy-General/How-The-Diesel-Crisis-Became-An-Inflationary-Time-Bomb.html">Diesel supply issues</a> and upcoming cuts to <a href="https://www.reuters.com/business/energy/opec-heads-deep-supply-cuts-clash-with-us-2022-10-04/">crude oil production</a> are also driving coal demand.</p>
<p>As the Northern Hemisphere heads into winter, demand is likely to increase further. The United Kingdom, for example, plans to keep <a href="https://www.reuters.com/business/energy/britain-keep-coal-fired-power-plants-open-this-winter-2022-07-29/">coal plants operating</a> this winter, despite a longer-term plan to permanently close them by October 2024. And Asia may have to lean more towards coal for the next six months as liquified natural gas flows into Europe.</p>
<p>All this has pushed <a href="https://tradingeconomics.com/commodity/coal">coal prices up</a>. So rain-related disruptions to Australian coal exports may result in missed opportunities for our coal operators. </p>
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<strong>
Read more:
<a href="https://theconversation.com/global-carbon-emissions-at-record-levels-with-no-signs-of-shrinking-new-data-shows-humanity-has-a-monumental-task-ahead-193108">Global carbon emissions at record levels with no signs of shrinking, new data shows. Humanity has a monumental task ahead</a>
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<p>At the same time, the coal industry faces headwinds. </p>
<p>Shipping costs have reached new <a href="https://www.freightwaves.com/news/dry-bulk-shipping-rates-hit-80000-per-day-as-buyers-scramble-for-coal">highs</a>. For Australian exporters, China’s <a href="https://www.smh.com.au/business/companies/china-s-ban-on-australian-coal-to-last-at-least-another-two-years-20220224-p59zcu.html">ban</a> on Australian coal is an added complication – however this week’s <a href="https://www.smh.com.au/politics/federal/xi-jinping-meets-with-albanese-ending-diplomatic-deep-freeze-20221115-p5byhb.html">meeting</a> between the two nation’s leaders may have thawed diplomatic relations.</p>
<p>Then, of course, there’s climate change. Coal is the world’s <a href="https://www.iea.org/news/global-coal-demand-is-set-to-return-to-its-all-time-high-in-2022">largest source</a> of energy-related carbon dioxide emissions. There’s widespread acknowledgement we must move away from burning coal and transition to renewable energy to avoid the worst climate harms.</p>
<p>Many countries still rely on coal for energy security and for use in industrial processes. Coal also supports jobs and provides export income.</p>
<p>In India, for example, the minister in charge of coal production <a href="https://www.canberratimes.com.au/story/7976087/coal-still-king-in-india-until-2040/">says</a> the fossil fuel will play an important role in the country until at least 2040. And a study released last month <a href="https://www.theguardian.com/environment/2022/oct/06/reckless-coal-firms-plan-climate-busting-expansion-study-finds">found</a> hundreds of coal companies around the world were developing new mines and power stations. </p>
<p>So moving away from coal – particularly thermal coal – is likely to take time. </p>
<figure class="align-center ">
<img alt="wind turbines against blue sky" src="https://images.theconversation.com/files/495568/original/file-20221116-14-rnqjwn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495568/original/file-20221116-14-rnqjwn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=355&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495568/original/file-20221116-14-rnqjwn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=355&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495568/original/file-20221116-14-rnqjwn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=355&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495568/original/file-20221116-14-rnqjwn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=446&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495568/original/file-20221116-14-rnqjwn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=446&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495568/original/file-20221116-14-rnqjwn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=446&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">There is widespread acknowledgement that the world must transition to renewable energy.</span>
<span class="attribution"><span class="source">Russell Freeman/AAP</span></span>
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<h2>What does all this mean?</h2>
<p>In the short term, as <a href="https://www.argusmedia.com/en/news/2361775-australia-issues-202223-la-nina-weather-alert">La Niña hangs around</a>, Australia may struggle to fulfil its coal supply commitments over the Southern Hemisphere spring and summer. </p>
<p>This is likely to add further headaches to the already crunched energy market. </p>
<p>Wet conditions are not the only <a href="https://reneweconomy.com.au/australian-mining-industry-extreme-weather-climate-change-74498/">climate threat</a> to the mining industry. Drought and heat, for example, reduce the availability of water needed to operate mines. And extreme heat can affect equipment, electricity supply and worker productivity.</p>
<p>In the longer term, the prospects for Australia’s coal exports are very uncertain. The Reserve Bank, for example, <a href="https://www.smh.com.au/politics/federal/grim-future-for-coal-and-gas-if-china-and-japan-meet-climate-plans-20211019-p5916y.html">says</a> coal and gas exports from Australia would at least halve if big buyers including China, Japan and South Korea meet their climate commitments. </p>
<p>There are many types of coal – and challenges abound in replacing them with cleaner alternatives. Until the transition is complete, coal is among many industries that must adapt to future weather extremes. </p>
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Read more:
<a href="https://theconversation.com/a-technologically-advanced-society-is-choosing-to-destroy-itself-its-both-fascinating-and-horrifying-to-watch-192939">A technologically advanced society is choosing to destroy itself. It's both fascinating and horrifying to watch</a>
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<img src="https://counter.theconversation.com/content/192018/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lurion De Mello does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The rain comes as coal demand surges and pressure mounts for the industry to wind back production to help tackle climate change.Lurion De Mello, Senior Lecturer in Finance, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1945292022-11-15T19:08:28Z2022-11-15T19:08:28ZClimate change will clearly disrupt El Niño and La Niña this decade – 40 years earlier than we thought<figure><img src="https://images.theconversation.com/files/495221/original/file-20221115-18-vliqyk.jpeg?ixlib=rb-1.1.0&rect=17%2C0%2C2977%2C1926&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>You’ve probably heard a lot about La Niña lately. This cool weather pattern is the main driver of heavy rain and flooding that has devastated much of Australia’s southeast in recent months.</p>
<p>You may also have heard of El Niño, which alternates with La Niña every few years. El Niño typically brings drier conditions to much of Australia. </p>
<p>Together, the two phases are known as the El Niño-Southern Oscillation – the strongest and most consequential factor driving Earth’s weather. And in recent years there has been much scientific interest in how climate change <a href="https://research.noaa.gov/article/ArtMID/587/ArticleID/2685/New-research-volume-explores-future-of-ENSO-under-influence-of-climate-change">will influence</a> this global weather-maker.</p>
<p>Our <a href="https://www.nature.com/articles/s41467-022-33930-5">new research</a>, released today, sheds light on the question. It found climate change will clearly influence the El Niño-Southern Oscillation by 2030 – in just eight years’ time. This has big implications for how Australians prepare for extreme weather events.</p>
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<img alt="a man and two women look at map" src="https://images.theconversation.com/files/495222/original/file-20221115-19-44kkrd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495222/original/file-20221115-19-44kkrd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495222/original/file-20221115-19-44kkrd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495222/original/file-20221115-19-44kkrd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495222/original/file-20221115-19-44kkrd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495222/original/file-20221115-19-44kkrd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495222/original/file-20221115-19-44kkrd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The study suggests Australians should prepare for more extreme weather to arrive earlier than previously thought. Pictured: NSW Premier Dom Perrottet with officials during a flood crisis.</span>
<span class="attribution"><span class="source">Bianca De Marchi/AAP</span></span>
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<h2>A complex weather puzzle</h2>
<p>The El Niño-Southern Oscillation occurs across the tropical Pacific, and involves complex interplays between the atmosphere and the ocean. It can be in one of <a href="http://www.bom.gov.au/climate/enso/history/ln-2010-12/three-phases-of-ENSO.shtml">three phases</a>: El Niño, La Niña or neutral. </p>
<p>During an El Niño phase, the central and eastern tropical Pacific Ocean warms significantly. This causes a major shift in cloud formation and weather patterns across the Pacific, typically leading to dry conditions in eastern Australia. </p>
<p>During a La Niña phase, which is occurring now, waters in the central and eastern tropical Pacific Ocean are cooler than average. The associated changes in weather patterns include higher than average rainfall over much of Australia.</p>
<p>When the oscillation is in the neutral phase, weather conditions hover around the long-term average.</p>
<p><a href="https://www.nature.com/articles/nclimate2743">Previous research</a> has suggested El Niño and La Niña events may vary depending on where in the tropical Pacific the warm or cold ocean temperatures are located.</p>
<p>But climate change is also affecting ocean temperatures. So how might this play into El Niño and La Niña events? And where might the resulting change in weather patterns be detected? These are the questions our research sought to answer.</p>
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<strong>
Read more:
<a href="https://theconversation.com/3-things-a-climate-scientist-wants-world-leaders-to-know-ahead-of-cop27-193534">3 things a climate scientist wants world leaders to know ahead of COP27</a>
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<h2>What we found</h2>
<p>We examined 70 years of data on the El Niño–Southern Oscillation since 1950, and combined it with 58 of the most advanced climate models available.</p>
<p><a href="https://www.nature.com/articles/s41467-022-33930-5">We found</a> the influence of climate change on El Niño and La Niña events, in the form of ocean surface temperature changes in the eastern Pacific, will be detectable by 2030. This is four decades earlier than <a href="https://www.nature.com/articles/s41558-022-01301-z">previously thought</a>.</p>
<p>Scientists already <a href="https://www.nature.com/articles/s43017-021-00199-z">knew</a> climate change was affecting the El Niño–Southern Oscillation. But because the oscillation is itself so complex and variable, it’s been hard to identify where the change is occurring most strongly.</p>
<p>However, our study shows the effect of climate change, manifesting as changes in ocean surface temperature in the tropical eastern Pacific, will be obvious and unambiguous within about eight years.</p>
<p>So what does all this mean for Australia? Warming of the eastern Pacific Ocean, fuelled by climate change, will cause stronger El Niño events. When this happens, rain bands are drawn away from the western Pacific where Australia is located. That’s likely to mean more droughts and dry conditions in Australia.</p>
<p>It’s also likely to bring more rain to the eastern Pacific, which spans the Pacific coast of Central America from southern Mexico to northern Peru. </p>
<p>Strong El Niño events are often followed by strong and prolonged La Niñas. So that will mean cooling of the eastern Pacific Ocean, bringing the rain band back towards Australia – potentially leading to more heavy rain and flooding of the kind we’ve seen in recent months.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/loss-and-damage-who-is-responsible-when-climate-change-harms-the-worlds-poorest-countries-192070">Loss and damage: Who is responsible when climate change harms the world's poorest countries?</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="residents clean up after floods" src="https://images.theconversation.com/files/495224/original/file-20221115-12-i3zxxc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495224/original/file-20221115-12-i3zxxc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495224/original/file-20221115-12-i3zxxc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495224/original/file-20221115-12-i3zxxc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495224/original/file-20221115-12-i3zxxc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495224/original/file-20221115-12-i3zxxc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495224/original/file-20221115-12-i3zxxc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Australia should prepare for more heavy rain and flooding.</span>
<span class="attribution"><span class="source">AAP/Getty pool</span></span>
</figcaption>
</figure>
<h2>What now?</h2>
<p>Weather associated with El Niño and La Niña has huge implications. It can affect human health, food production, energy and water supply, and economies around the world.</p>
<p>Our research suggests Australians, in particular, must prepare for more floods and droughts as climate change disrupts the natural weather patterns of the El Niño-Southern Oscillation. </p>
<p>Our findings should be incorporated into policies and strategies to adapt to climate change. And crucially, they add to the weight of evidence pointing to the urgent need to reduce greenhouse gas emissions to stabilise Earth’s climate.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/effects-of-climate-change-such-as-flooding-makes-existing-disadvantages-for-indigenous-communities-so-much-worse-192090">Effects of climate change such as flooding makes existing disadvantages for Indigenous communities so much worse</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/194529/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wenju Cai does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The findings have big implications for how Australians prepare for extreme weather events.Wenju Cai, Chief Research Scientist, Oceans and Atmosphere, CSIRO, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1930262022-11-14T00:35:22Z2022-11-14T00:35:22ZThey’re doing their best: how these 3 neighbourhood ‘pests’ deal with rainy days<figure><img src="https://images.theconversation.com/files/493996/original/file-20221108-18-x9ma6s.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C2700%2C1786&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Have you had a recent encounter with an animal you’d much rather avoid? As La Niña continues to give us rainy days, brush turkeys, bats, and cockroaches are emerging from their hide-outs. </p>
<p>We often think of them as pests, but these animals are just trying their best to cope in the heavy rain. They’re also crucial members of our urban ecosystems, and help keep the environment healthy. </p>
<p>Here’s what makes them so fascinating and important to your neighbourhood. </p>
<h2>Bats: heavy rain hinders echolocation</h2>
<p>Australia is home to multiple threatened species of <a href="https://theconversation.com/australias-threatened-bats-need-protection-from-a-silent-killer-white-nose-syndrome-129186">fruit bats and microbats</a>, such as grey-headed flying foxes, large bent-wing bats, and spectacled flying foxes. </p>
<p>They’re typically considered nuisances for their noise, mess and potential spread of diseases. But bats are often forgotten for their ability to control insect pests, disperse seeds, and pollinate plants.</p>
<p>Bats face some serious threats in La Niña conditions. They can respond to periods of heavy rain by using a special physiological adaptation called torpor. In torpor, bats will sleep more and lower their body temperature so they can use less energy.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492061/original/file-20221027-20344-y8o5dv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Microbat sp. giving a smile (this bat was handled by a gloved, trained professional. Never pick up a bat yourself)</span>
<span class="attribution"><span class="source"> Image Credit Dieter Hochuli</span></span>
</figcaption>
</figure>
<p><a href="https://www.ausbats.org.au/uploads/4/4/9/0/44908845/meet_sydneys_microbats.pdf">Microbats</a> are abundant throughout Australian cities. They use <a href="https://theconversation.com/fruit-bats-are-the-only-bats-that-cant-and-never-could-use-echolocation-now-were-closer-to-knowing-why-153721">echolocation to see</a>, but heavy rain likely <a href="https://www.sciencedaily.com/releases/2019/02/190206115623.htm">reduces</a> this ability. </p>
<p>In 2019, Smithsonian researchers played recordings of downpours near bat roosts, and found the bats delayed emerging from their roosts. Delayed emergence can lead to disorientated bats with a reduced capacity to find food. </p>
<p>In Australia, rain may affect microbats more than fruit bats because of where they live. Many species of microbats, such as the <a href="https://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=10534">large bent-winged bat</a>, live in culverts and under bridges, where higher water levels can rush through during heavy rain periods.</p>
<p>Fruit bats, such as flying foxes, <a href="https://theconversation.com/fruit-bats-are-the-only-bats-that-cant-and-never-could-use-echolocation-now-were-closer-to-knowing-why-153721">don’t use echolocation</a>, but rain can wet their fur and lower their body temperature. So they’ll often stay put in their roosts to keep warm during heavy rain.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/fruit-bats-are-the-only-bats-that-cant-and-never-could-use-echolocation-now-were-closer-to-knowing-why-153721">Fruit bats are the only bats that can't (and never could) use echolocation. Now we're closer to knowing why</a>
</strong>
</em>
</p>
<hr>
<p>It also <a href="https://royalsocietypublishing.org/doi/10.1098/rsbl.2011.0313">costs a lot more energy</a> for a bat to fly in the rain, making it harder to maintain a steady intake of food. If there is consecutive days of rain, bats may fall from their home due to starvation. </p>
<p>If you find a fallen bat, do not touch it. Instead, contact <a href="https://www.wires.org.au/wildlife-information/flying-foxes-and-microbats">WIRES</a>. Or, wait to see if they leave once the rain clears up.</p>
<h2>Brush turkeys: reshape their mounds</h2>
<p>Brush turkeys are a type of ground nesting bird found along Australia’s east coast, from Cape York in Queensland down to Wollongong in NSW. They’re particularly vulnerable to the effects of heavy rain, which can damage or wash out their nests. </p>
<p>To incubate their eggs, brush-turkeys build enormous mounds of leaf litter and mulch. These mounds can weigh several tonnes, and can be as wide as <a href="https://www.qld.gov.au/environment/plants-animals/animals/living-with/brush-turkeys">4 metres across and up to 1 metre high</a>. These mounds often cause <a href="https://www.abc.net.au/news/2016-03-31/brush-turkeys-haunting-sydney-backyards/7287518">consternation among avid gardeners</a> and frustrated suburbanites.</p>
<p>But brush-turkeys can benefit the environment. As they <a href="https://birdlife.org.au/bird-profile/australian-brush-turkey">scratch for food and build mounds</a>, the birds help break down leaf litter and aerate the soil. This helps water and nutrients move throughout your soil, which ultimately helps your garden.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492062/original/file-20221027-12-3pyzmd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Brush-turkey on a mound.</span>
<span class="attribution"><span class="source">Image Credit Matthew Hall</span></span>
</figcaption>
</figure>
<p>Winter rainfall is the trigger for males to start building their mounds, as the increased soil moisture provides the heat that incubates their eggs. However, research shows males <a href="https://www.tandfonline.com/doi/abs/10.1071/MU9880210">avoid constructing their nests</a> during long periods of heavy rain.</p>
<p>Flood waters can sweep away existing mounds and, after multiple weeks of rain, mounds can become waterlogged. Floods can drown eggs or reduce mound temperatures below the levels necessary for incubation, preventing the chicks from developing properly. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=484&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=484&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=484&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=608&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=608&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492065/original/file-20221027-25221-sv6gb2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=608&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A brush-turkey chick.</span>
<span class="attribution"><span class="source">Image Credit John Martin</span></span>
</figcaption>
</figure>
<p>Brush-turkeys are known to protect their mounds from heavy rain. Much anecdotal evidence suggests brush-turkeys can predict the weather in advance, and <a href="http://www.climatekelpie.com.au/index.php/1999/08/01/the-brush-turkeys-are-never-wrong/">reshape their mound accordingly</a>. </p>
<p>During light rain, male brush-turkeys <a href="https://www.abc.net.au/local/stories/2011/11/23/3374445.htm">open up their mound</a>, letting much-needed moisture soak in to speed up decomposition of the leaf litter. But as strong rainfall approaches, they instead <a href="https://catalogue.nla.gov.au/Record/4385974">pile extra material on top of their mound</a>, providing an extra layer of protection and creating a more conical shape so water can run off the sides. </p>
<p>Next time, consider tuning into your local brush turkeys for a weather forecast. If you see them doing a bit of extra raking in your garden on dismal grey days, it might be a scramble to protect their nests from approaching heavy rain. </p>
<p>When you spot one, use the opportunity to snap a photo and upload it to the <a href="https://taronga.org.au/conservation-and-science/current-research/big-city-birds">Big City Birds app</a>. This app tracks where birds such as brush-turkeys occur, and how they’re adapting to city life.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/sad-and-distressing-massive-numbers-of-bird-deaths-in-australian-heatwaves-reveal-a-profound-loss-is-looming-190685">‘Sad and distressing’: massive numbers of bird deaths in Australian heatwaves reveal a profound loss is looming</a>
</strong>
</em>
</p>
<hr>
<h2>Native cockroaches: evacuate to drier areas</h2>
<p>As we settle into another wet spring, our homes are becoming perfect breeding grounds for cockroaches. The humidity of a moist house combined with warmer weather, allows for cockroaches to grow quicker and thrive. </p>
<p>Only a small handful of cockroach species will survive in the average house, and they are all introduced species. After rain, it’s vital to make your house a little less cockroach friendly. Reduce humidity by keeping the house well ventilated, and make sure to remove any food scraps.</p>
<p>On the other hand, the waterlogged soil in your local green spaces are likely home to some of <a href="https://australian.museum/learn/animals/insects/cockroaches-order-blattodea/">Australia’s 450 native species of cockroaches</a>, so you might see some around your backyard after rain. Cockroaches play important roles in the ecosystem, breaking down nutrients in the soil.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=643&fit=crop&dpr=1 600w, https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=643&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=643&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=808&fit=crop&dpr=1 754w, https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=808&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/494376/original/file-20221109-22-y2eyjf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=808&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Native Australian <em>Ellipsidion sp.</em> cockroach.</span>
<span class="attribution"><span class="source">Image Credit Elise Oakman</span></span>
</figcaption>
</figure>
<p>Burrowing cockroaches can be spotted because they don’t have wings. Many of our other native cockroaches are obvious due to their <a href="https://www.australiangeographic.com.au/topics/wildlife/2018/04/our-native-cockroaches-arent-as-gross-as-you-think/">beautiful colours and patterns</a>.</p>
<p>One amazing example is the <a href="https://www.sydney.edu.au/news-opinion/news/2022/10/01/extinct-wood-eating-cockroach-rediscovered-after-80-years.html">Lord Howe Island wood-feeding cockroach</a>. Thought to be extinct for some 80 years due to rats, they have only recently been rediscovered. This species is important, because it recycles nutrients and is food for other animals.</p>
<p>While native cockroaches may enter your home in an attempt to find warm dry ground, they won’t thrive indoors. If you find a native cockroach inside your house, instead of reaching for the bug spray, it’s best to catch them and put them back outside. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-large-cockroach-thought-extinct-since-the-1930s-was-just-rediscovered-on-a-small-island-in-australia-191847">A large cockroach thought extinct since the 1930s was just rediscovered on a small island in Australia</a>
</strong>
</em>
</p>
<hr>
<p>So during wet weather, take the time to remember that these animals are trying their best. All have amazing ways of adapting to heavy rain, and we should cut them some slack – the environment, including our backyards, need them.</p><img src="https://counter.theconversation.com/content/193026/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elise Oakman receives funding from the Ecological Society of Australia, the Department of Planning and Environment, and the Australian Wildlife Society.</span></em></p><p class="fine-print"><em><span>Caitlyn Forster receives funding from the Australian Research Council. She is affiliated with the Australasian Society for the Study of Animal Behaviour and Invertebrates Australia. </span></em></p><p class="fine-print"><em><span>Matthew Hall has previously received research funding from The Australian Citizen Science Association and Birding NSW. </span></em></p><p class="fine-print"><em><span>Mei-Ting Kao does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Brush turkeys, bats, and cockroaches are crucial for the environment – including our gardens. Each have fascinating ways of coping in wet weather.Elise Oakman, PhD Candidate, University of SydneyCaitlyn Forster, PhD Candidate, School of Life and Environmental Sciences, University of SydneyMatthew Hall, Casual Academic, University of SydneyMei-Ting Kao, PhD student, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1941592022-11-10T19:00:36Z2022-11-10T19:00:36ZThink storms are getting worse? Rapid rain bursts in Sydney have become at least 40% more intense in 2 decades<figure><img src="https://images.theconversation.com/files/494295/original/file-20221108-20-z1j0w5.jpg?ixlib=rb-1.1.0&rect=0%2C143%2C3778%2C2520&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>A series of major floods in Australia has made global headlines in recent years. People around the world <a href="https://www.bbc.com/news/world-australia-62027248">were shocked to see</a> Sydney, the city known for the 2000 Olympics, the Harbour Bridge, the Opera House, sunshine and Bondi beach culture inundated with flash floods this year. But were these floods a freak occurrence or a sign of things to come?</p>
<p>Our <a href="https://www.science.org/doi/10.1126/science.abn8657">research</a> has found an alarming increase of at least 40% in the rate at which rain falls in the most intense rapid rain bursts in Sydney over the past two decades. This rapid increase in peak rainfall intensity has never been reported elsewhere, but may be happening in other parts of the world.</p>
<p>Our findings, <a href="https://www.science.org/doi/10.1126/science.abn8657">published today</a> in Science, have major implications for the city’s preparedness for flash flooding. More intense downpours are likely to overwhelm stormwater systems that were designed for past conditions. </p>
<p>The chart below shows the increases in the rate of rainfall of rapid rain bursts for each of three weather radars (at Newcastle, Terrey Hills and Wollongong). All radars showed a rate of change of at least 20% per decade. </p>
<iframe title="% change per decade in rapid rain bursts for each radar site" aria-label="Bar Chart" id="datawrapper-chart-uAYU5" src="https://datawrapper.dwcdn.net/uAYU5/5/" scrolling="no" frameborder="0" style="border: none;" width="100%" height="243" data-external="1"></iframe>
<p>To increase our confidence, we also calculated the change for rapid rain bursts observed by two radars (Wollongong and Terrey Hills) at the same time. The rates of change in these storms are much higher (80-90% per decade) than for storms detected only by a single radar station. </p>
<p>One possible explanation could be these are more extreme storms that are well developed and can be seen by two radars simultaneously. So, it is possible that the change in rainfall rates for well-developed rapid rain bursts is even greater.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/beyond-a-state-of-sandbagging-what-can-we-learn-from-all-the-floods-here-and-overseas-193011">Beyond a state of sandbagging: what can we learn from all the floods, here and overseas?</a>
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</em>
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<h2>What are rapid rain bursts?</h2>
<p><a href="https://climateextremes.org.au/what-is-a-rapid-rain-burst/">Rapid rain bursts</a> are very heavy rainfalls lasting less than an hour – often as little as ten minutes.</p>
<p>These events are typically highly localised. They can be a part of a larger storm or form independently. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/494351/original/file-20221109-25-jbbx4c.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/494351/original/file-20221109-25-jbbx4c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/494351/original/file-20221109-25-jbbx4c.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=623&fit=crop&dpr=1 600w, https://images.theconversation.com/files/494351/original/file-20221109-25-jbbx4c.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=623&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/494351/original/file-20221109-25-jbbx4c.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=623&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/494351/original/file-20221109-25-jbbx4c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=782&fit=crop&dpr=1 754w, https://images.theconversation.com/files/494351/original/file-20221109-25-jbbx4c.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=782&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/494351/original/file-20221109-25-jbbx4c.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=782&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A rapid rain burst (highlighted rain pattern) close to Sydney detected in Wollongong radar.</span>
</figcaption>
</figure>
<p>Rapid rain bursts can cause a huge amount of water to build up rapidly over a small region. This leaves almost no time for water to sink into the ground or be carried away by rivers and urban channels such as gutters and stormwater drains.</p>
<p><a href="https://theconversation.com/what-is-a-flash-flood-a-civil-engineer-explains-187961">Flash flooding</a>, especially in urban and steep mountainous regions, is one of the main destructive outcomes of these storms. The consequences include loss of human life, damage to property and infrastructure such as bridges and roads, crop and livestock losses, and disruptions to power and water supplies.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-is-a-flash-flood-a-civil-engineer-explains-187961">What is a flash flood? A civil engineer explains</a>
</strong>
</em>
</p>
<hr>
<h2>New techniques offer fresh insights</h2>
<p>It has been difficult for meteorologists and climate scientists to investigate the structure of rapid rain bursts and their changes over time. The most recent <a href="https://www.ipcc.ch/report/ar6/wg2/">report</a> of the Intergovernmental Panel on Climate Change (<a href="https://en.wikipedia.org/wiki/Intergovernmental_Panel_on_Climate_Change">IPCC</a>) raised this as an issue to be overcome.</p>
<p>The main barrier is the small-scale nature of these events, which is hard for typical observational instruments such as rain gauges and satellites to capture. Climate models also cannot directly simulate rapid rain bursts. These difficulties limit our ability to understand and foresee changes in these events.</p>
<p>Weather radars are able to see these storms. However, they have not previously been used to study changes over time. This has been due to uncertainties about whether they measure consistently over time and difficulty in accessing the data.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/S0eSxDRgbrg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The authors discuss their study and its findings.</span></figcaption>
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<p>Our collaboration with the Bureau of Meteorology developed a new method to overcome these limitations. We used Sydney’s <a href="http://www.bom.gov.au/products/IDR713.loop.shtml">weather radar maps</a> produced by three overlapping radar stations (at Newcastle, Terrey Hills and Wollongong) over two decades. Benefiting from image-processing techniques, we identified and tracked storms observed by more than one radar at once.</p>
<p>All three radars confirmed a surprisingly high rate of change in the intensity of the strongest rapid rain bursts. The rainfall rate increased at least 20% per decade over the region. We found similar upward trends in short-duration peak rainfall in nine high-precision gauge stations in the region. </p>
<p>The graph below shows the rainfall rate of the top 5% of all rapid rain bursts detected separately in each radar each year, relative to the average for the whole period. (The figures shown for each radar are a ratio. It’s calculated by dividing the rainfall rate of the top 5% of rapid rain bursts each year by the average rate for such rain bursts over the whole period covered by that radar. This allows us to compare rates of change for radars with different calibrations and configurations.)</p>
<p>For the Wollongong radar, the average rate of these rapid rain bursts for the past 20 years is around 35mm per hour. The average values for Terrey Hills and Newcastle radars are around 60mm/hr and 25mm/hr, respectively.</p>
<iframe title="Annual changes in rainfall rate of top 5% of rapid rain bursts" aria-label="Interactive line chart" id="datawrapper-chart-HjQnY" src="https://datawrapper.dwcdn.net/HjQnY/10/" scrolling="no" frameborder="0" style="border: none;" width="100%" height="400" data-external="1"></iframe>
<h2>What does this mean for infrastructure?</h2>
<p>This high rate of change is concerning, but also scientifically fascinating.</p>
<p>It’s concerning because flood control infrastructure has been designed according to rainfall observed years ago. This change in rain bursts hasn’t been considered properly in design standards for structures such as drains, channels, detention basins and coastal flood defences.</p>
<p>An intensification of 40% in only two decades means we must re-evaluate existing <a href="https://theconversation.com/not-if-but-when-city-planners-need-to-design-for-flooding-these-examples-show-the-way-157578">flood-control systems</a> and standards. We also need to explore whether it is happening elsewhere or unique to Sydney.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1500985779262160897"}"></div></p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/not-if-but-when-city-planners-need-to-design-for-flooding-these-examples-show-the-way-157578">Not 'if', but 'when': city planners need to design for flooding. These examples show the way</a>
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</em>
</p>
<hr>
<h2>What’s driving this change?</h2>
<p>Despite the dramatic increase in the intensity of rapid rain bursts, we found little if any change in daily or even hourly rainfall over the same region.</p>
<p>It’s not clear why such large changes in precipitation bursts could happen without changes in the average rainfall over whole storms. This finding indicates that we have more to learn.</p>
<p>Although the reasons for this unexpected change in rapid rain bursts are still unknown, we showed it can’t be explained by regular climate variabilities such as <a href="https://www.youtube.com/watch?v=dzat16LMtQk">El Niño–Southern Oscillation</a>, <a href="https://www.youtube.com/watch?v=J6hOVatamYs">Indian Ocean Dipole</a> and <a href="https://www.youtube.com/watch?v=KrhWsXCB3u8">Southern Annular Mode</a>. Ruling out these explanations leaves climate change as a plausible factor in these changes. Further research into storms is needed to understand the underlying contribution of climate processes.</p>
<p>The next step is applying this new technique of weather radar analysis more broadly, including other cities around the world, to explore the possible causes of this alarming change in our storms.</p><img src="https://counter.theconversation.com/content/194159/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hooman Ayat receives funding from Australian Research Council.</span></em></p><p class="fine-print"><em><span>Jason Evans receives funding from the Australian Research Council and the National Environmental Science Program. </span></em></p><p class="fine-print"><em><span>Steven Sherwood receives funding from the Australian Research Council and US DARPA / STR.</span></em></p>The growing threat of flash flooding as a result of more intense rapid rain bursts means the city needs to update its flood defences.Hooman Ayat, Research Fellow, Geography, Earth and Atmospheric Sciences and ARC Centre of Excellence for Climate Extremes, The University of MelbourneJason Evans, Professor, Climate Change Research Centre, UNSW SydneySteven Sherwood, Professor of Atmospheric Sciences, Climate Change Research Centre, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1914692022-11-02T17:06:03Z2022-11-02T17:06:03ZIf more houses had water butts, it could help with drought, flooding and water pollution<figure><img src="https://images.theconversation.com/files/492090/original/file-20221027-20344-4bkeu3.jpg?ixlib=rb-1.1.0&rect=8%2C0%2C5590%2C3715&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A small rain tank could supply 15% of a household's total annual water consumption on average across the UK.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-collecting-rainwater-barrel-2197232009">Alexander Knyazhinsky/Shutterstock</a></span></figcaption></figure><p>Earlier this year, southern England experienced its <a href="https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2022/driest-july-in-england-since-1935">driest July on record</a>. The drought affected many parts of the UK and grew so acute that Thames Water’s hosepipe ban will <a href="https://www.bbc.co.uk/news/uk-england-london-63048351">remain in force</a> into 2023. </p>
<p>But rainfall in August was <a href="https://en.wikipedia.org/wiki/2022_United_Kingdom_floods">heavy</a>. The volume of rain <a href="https://theriverstrust.org/about-us/news/new-interactive-map-reveals-the-truth-about-sewage-pollution">caused</a> outdated drainage and sewerage systems to overflow, <a href="https://publications.parliament.uk/pa/cm5802/cmselect/cmenvaud/74/report.html">degrading the quality</a> of many of the UK’s rivers. </p>
<p><a href="https://nic.org.uk/app/uploads/NIC-Preparing-for-a-Drier-Future-26-April-2018.pdf">Extreme weather patterns</a> such as these are set to dominate our future. The Environment Agency <a href="https://www.gov.uk/government/news/lack-of-water-presents-existential-threat-says-environment-agency-chief">predicts</a> that demand for water in southern England may outstrip supply in the next 20 years. Yet, at the same time, as many as <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/920944/023_15482_Environment_agency_digitalAW_Strategy.pdf">5.2 million</a> UK properties are threatened by flooding.</p>
<p><a href="https://www.communityactionforwater.org/stories/waterbuttsandflooding">Our research</a> suggests that collecting rainwater in water butts may offer a solution to these problems. This cheap, small-scale intervention could help protect households against water risks while engaging those involved with water issues. Unfortunately, the government tends to ignore this scale of intervention. </p>
<h2>Engineered solutions to water issues</h2>
<p>Water management in England is largely isolated to large infrastructure projects. Reservoirs are built to withstand drought and larger sewers are seen as the solution to flooding and water pollution. </p>
<p>But these approaches are costly; Central London’s new sewer, the <a href="https://www.thameswater.co.uk/about-us/investing-in-our-region/thames-tideway-tunnel#:%7E:text=The%20tunnel%20will%20cost%20%C2%A3,wastewater%20customers%20through%20their%20bills">Thames Tideway Tunnel</a>, will cost £4.3 billion. </p>
<p>They can also harm the environment. The Thames Tideway tunnel will prolong the energy-intensive pumping of dirty sewage, while building reservoirs often involves the flooding of agricultural land and wildlife habitats.</p>
<p>These government and water industry solutions also fail to engage the public. <a href="https://www.cambridge-water.co.uk/news/the-great-british-rain-paradox">Public awareness</a> of the dual drought and flood crises, therefore, remains low. According to a <a href="https://www.hwmglobal.com/uploads/Great%20British%20Rain%20Paradox.pdf">report</a> published in 2020 and partly funded by the Environment Agency, 72% of people surveyed believe that the UK has enough water to meet the country’s needs.</p>
<figure class="align-center ">
<img alt="A tunnel boring machine standing on the bank of the Thames, next to a large warehouse." src="https://images.theconversation.com/files/492092/original/file-20221027-1498-93mxo5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/492092/original/file-20221027-1498-93mxo5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492092/original/file-20221027-1498-93mxo5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492092/original/file-20221027-1498-93mxo5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492092/original/file-20221027-1498-93mxo5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492092/original/file-20221027-1498-93mxo5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492092/original/file-20221027-1498-93mxo5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">One of the Thames Tideway Tunnel boring machines ready to begin tunnelling.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/london-england-uk-june-8-2018-1729245604">Joe Dunckley/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Re-thinking water management</h2>
<p>There are other ways to manage the UK’s water better.</p>
<p>The roof area of an average terraced house in the UK (30m²) receives <a href="https://www.metoffice.gov.uk/research/climate/maps-and-data/uk-climate-averages">19,000–55,000 litres of rain</a> each year. Our modelling suggests that a significant proportion of household water consumption could be met by collecting this water. </p>
<p>Averaged across the UK, we found that a 210-litre rain tank – equivalent to a small bath – could supply 15% of a household’s total annual water consumption. But this will be subject to clear geographic and seasonal variation. </p>
<p>The calculation accounts for the <a href="https://www.sciencedirect.com/science/article/pii/S0169204605000496">loss of rainwater</a> through processes such as evaporation. <a href="https://knowledge.bsigroup.com/products/on-site-non-potable-water-systems-systems-for-the-use-of-rainwater/standard">Current regulations</a> also restrict the use of rain tank water to non-potable demands, such as flushing toilets.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/491620/original/file-20221025-232-m8nxx9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/491620/original/file-20221025-232-m8nxx9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=301&fit=crop&dpr=1 600w, https://images.theconversation.com/files/491620/original/file-20221025-232-m8nxx9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=301&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/491620/original/file-20221025-232-m8nxx9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=301&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/491620/original/file-20221025-232-m8nxx9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=378&fit=crop&dpr=1 754w, https://images.theconversation.com/files/491620/original/file-20221025-232-m8nxx9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=378&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/491620/original/file-20221025-232-m8nxx9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=378&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rainfall rates vary across the UK.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>In the wetter northwest of Scotland, we found that 26% of a household’s annual water consumption could be met by collecting rainwater. In contrast, only 9% could be supplied in the southeast of England, dropping to 4% in the driest months. Although this seems a low value, it still equates to 14 litres of water per household each day.</p>
<h2>Reducing the risk of flooding and pollution</h2>
<p>In the future, wetter winters will also become more common. This will amplify the risk of flooding and water pollution. Our research suggests that a network of small water butts fitted across towns or cities could substantially reduce these risks. </p>
<p>In the event of a storm, a 210-litre water butt can capture <a href="https://www.communityactionforwater.org/stories/waterbuttsandflooding">7mm of rainfall</a> from the roof of an average terraced house. To put this in context, in the English city of Hull, a storm that deposits <a href="https://www.ceh.ac.uk/sites/default/files/2022-10/Flood%20Studies%20Report%20-%20Volume%201%20-%20Hydrological%20Studies.pdf">22.3 mm of rainfall</a> is sufficient to cause flooding. This amount of rain typically falls once every ten years. </p>
<p>So if we can store 7mm of that rain in a water butt, then the amount that is required to cause a flood rises to 28.6mm. A storm that results in this amount of rainfall only occurs once every 30 years.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/492093/original/file-20221027-25221-fk9f19.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A red road closed sign emerging from a heavily flooded town road." src="https://images.theconversation.com/files/492093/original/file-20221027-25221-fk9f19.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/492093/original/file-20221027-25221-fk9f19.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492093/original/file-20221027-25221-fk9f19.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492093/original/file-20221027-25221-fk9f19.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492093/original/file-20221027-25221-fk9f19.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=496&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492093/original/file-20221027-25221-fk9f19.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=496&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492093/original/file-20221027-25221-fk9f19.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=496&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The installation of rain tanks could reduce the frequency of flooding.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/road-flood-closed-sign-under-deep-1652959534">richardjohnson/Shutterstock</a></span>
</figcaption>
</figure>
<p>This approach is not without its limitations. The area that is occupied by roofs is far smaller than the total area over which rain falls. The hydrology of a flood is also complex, including the movement of water through a catchment from uplands to lower-lying areas. </p>
<p>But if used in combination with <a href="https://www.bgs.ac.uk/geology-projects/suds/">sustainable drainage systems</a> and other <a href="https://www.gov.uk/flood-and-coastal-erosion-risk-management-research-reports/working-with-natural-processes-to-reduce-flood-risk">natural flood management measures</a>, water butts could make a small but meaningful contribution to reducing the threat of flooding and water pollution. Through various processes, sustainable drainage systems provide an alternative to the direct channelling of rainwater through pipes and sewers to nearby watercourses. By providing additional storage in ponds, for example, the flow of surface water can be reduced.</p>
<p>Even then, large numbers of households would still need to install water butts for this approach to have any effect. We have worked with local voluntary organisations to establish a non-profit cooperative called Susdrainable that specialises in the design and installation of rain tanks (water butts). Together, we have installed rain tanks on public buildings in Hull and are working on signage and leaflets to provide households with the information they need to participate in water management.</p>
<p>Water butts are not a replacement for large-scale water management infrastructure, but they do offer a cheaper mitigation option – one that also engages the public with water issues. There is a role for everyone as we prepare for a future dominated by drought and flood.</p>
<p><em>This article has been amended to clarify the cost of the Thames Tideway Tunnel is £4.3 billion not £4.9 billion as originally stated.</em></p><img src="https://counter.theconversation.com/content/191469/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The research contributing to this paper was funded by UKRI grant no NE/T01394X/1. </span></em></p><p class="fine-print"><em><span>The research behind this article was funded by the UKRI, grant no NE/T01394X/1
</span></em></p><p class="fine-print"><em><span>The research contributing to this paper was funded by UKRI grant no NE/T01394X/1.</span></em></p>Extreme weather is set to dominate our future – can collecting rainwater reduce the threat posed by both drought and flooding?Liz Sharp, Senior Lecturer in Urban Studies and Planning, University of SheffieldKiera Chapman, Research Associate, University of SheffieldRuth Quinn, Assistant Lecturer of Civil, Environmental and Water Engineering, Atlantic Technological UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1918642022-10-14T01:41:34Z2022-10-14T01:41:34ZCotton on: one of Australia’s most lucrative farming industries is in the firing line as climate change worsens<p>The northern Murray-Darling Basin produces 93% of Australia’s cotton. Cotton is one of Australia’s biggest agricultural industries – worth <a href="https://www.csiro.au/en/research/production/materials/cotton">about A$2 billion</a> each year – and a steady supply of water is crucial for production. </p>
<p>Our <a href="https://doi.org/10.3390/w14193073">recently published research</a> reveals that since the 1990s, average April-May rainfall in the northern basin has decreased significantly. The decrease coincides with accelerated climate change.</p>
<p>Our research also found average or below-average rainfall in the remaining cool season months June to September. Without substantial spring or summer rain, this leads to less rainfall runoff in dams – and less water to irrigate cotton and other crops.</p>
<p>Climate change will bring more frequent droughts, as well as more frequent flooding. These two future extremes in rainfall both have the potential to damage Australia’s lucrative cotton industry.</p>
<figure class="align-center ">
<img alt="drought-stricken cotton crop" src="https://images.theconversation.com/files/488880/original/file-20221009-58212-h17m5t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488880/original/file-20221009-58212-h17m5t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488880/original/file-20221009-58212-h17m5t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488880/original/file-20221009-58212-h17m5t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488880/original/file-20221009-58212-h17m5t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488880/original/file-20221009-58212-h17m5t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488880/original/file-20221009-58212-h17m5t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">New research suggests more frequent drought will wreak further havoc on Australia’s cotton industry.</span>
<span class="attribution"><span class="source">Danny Casey/AAP</span></span>
</figcaption>
</figure>
<h2>A vital river system</h2>
<p>The northern Murray-Darling Basin spans northeast New South Wales and southeast Queensland. It comprises floodplains of streams or small rivers that feed into the Darling River.</p>
<p>Cotton in the basin is mostly grown on clay soils on floodplains next to rivers. When rivers flood after heavy rain, the soil stores water for later plant growth.</p>
<p>Water stored in the cooler months ensures an adequate supply of water in summer, when cotton crops require the most water. Insufficient rain in the cooler months means dam water will be needed in summer. But highly variable summer rain means this water is not always available.</p>
<p>Maintaining water flow through the northern Murray-Darling Basin is crucial. Many farms and communities rely on river water for human consumption and to irrigate cotton and other crops. And a sustainable water supply is vital for the ecological health of wetlands, waterholes and floodplains.</p>
<figure class="align-center ">
<img alt="dry river bed with tree trunk bearing words 'save the Darling'" src="https://images.theconversation.com/files/488883/original/file-20221009-78090-9iaitu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488883/original/file-20221009-78090-9iaitu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488883/original/file-20221009-78090-9iaitu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488883/original/file-20221009-78090-9iaitu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488883/original/file-20221009-78090-9iaitu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488883/original/file-20221009-78090-9iaitu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488883/original/file-20221009-78090-9iaitu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Darling River is the heart of the northern Murray-Darling Basin.</span>
<span class="attribution"><span class="source">Dean Lewins/AAP</span></span>
</figcaption>
</figure>
<h2>What we found</h2>
<p>Our research examined annual April-May rainfall in the northern Murray-Darling Basin from 1911 to 2019. Other research has concentrated on autumn rainfall for southeast Australia but not specifically on this part of the basin.</p>
<p>We already knew 94% of water gauges in the northern Murray-Darling Basin <a href="https://publications.csiro.au/rpr/download?pid=csiro:EP206574&dsid=DS1">showed declining trends</a> in water flow since records began in 1970. Our <a href="https://www.nature.com/articles/s41598-021-95531-4">previous research</a> had also found a declining rainfall trend in April-May in the southern Murray-Darling Basin. So we wanted to see if the trend was similar in the north.</p>
<p>For the drought from 2017 to 2019, almost all the northern parts of the basin experienced their driest ever period or close to it.</p>
<p>But the consecutive La Niñas of 2020-21 and 2021-22 brought heavy rain to the northern Murray-Darling Basin – filling dams and leading to flooding.</p>
<p>Rain is generated by short-term events such as thunderstorms, as well as large-scale systems. In eastern Australia, these include <a href="http://www.bom.gov.au/climate/about/australian-climate-influences.shtml">climate drivers</a> such as the El Niño-Southern Oscillation, Southern Annular Mode and Indian Ocean Dipole. </p>
<p>These climate drivers influence weather over months and seasons. In the northern Murray-Darling Basin, they’re responsible for highly variable seasonal and annual rainfall. Specifically, we found:</p>
<ul>
<li>the El Niño-Southern Oscillation influences spring/summer rainfall</li>
<li>the Southern Annular Mode affects summer rainfall</li>
<li>the Indian Ocean Dipole is important for late winter/spring rainfall.</li>
</ul>
<p>Significantly, global warming was a prominent contributor to extremes of rainfall in all seasons, both individually and in combination with other climate drivers.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-murrumbidgee-rivers-wet-season-height-has-dropped-by-30-since-the-1990s-and-the-outlook-is-bleak-165764">The Murrumbidgee River's wet season height has dropped by 30% since the 1990s — and the outlook is bleak</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="a dry river bed with green water" src="https://images.theconversation.com/files/488887/original/file-20221009-59215-h59kcf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488887/original/file-20221009-59215-h59kcf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488887/original/file-20221009-59215-h59kcf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488887/original/file-20221009-59215-h59kcf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488887/original/file-20221009-59215-h59kcf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488887/original/file-20221009-59215-h59kcf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488887/original/file-20221009-59215-h59kcf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Global warming was a prominent contributor to extremes of rainfall in all seasons.</span>
<span class="attribution"><span class="source">Dean Lewins/AAP</span></span>
</figcaption>
</figure>
<h2>North vs south</h2>
<p>Typically, it rains more in the northern Murray-Darling Basin during the warmer season, and more in the south in the late cool season. Both receive significantly decreased rainfall in April and May. </p>
<p>So in the north, reduced April-May rainfall, coupled with the usual lower rainfall late in the cool season, can mean dams are not full heading into the warmer season where irrigation water is crucial for cotton crops.</p>
<p>A compounding factor is that the northern dams have <a href="https://www.mdba.gov.au/water-management/murray-darling-reports-data/water-in-storages">about one-third</a> the capacity of the south. What’s more, rising temperatures since the 1990s have <a href="https://doi.org/10.1029/2018GL079332">increased evaporation</a> lost from vegetation across the basin – and during 2018-2019, the evaporation was higher in the north.</p>
<p>So what does all this mean? The results suggest global warming will both increase temperatures and rainfall extremes in the northern Murray-Darling Basin, bringing more frequent droughts and floods. The associated impact on yields will likely threaten the future of cotton farming – by far the basin’s most important crop.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/cotton-breeders-are-using-genetic-insights-to-make-this-global-crop-more-sustainable-185284">Cotton breeders are using genetic insights to make this global crop more sustainable</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="tractor drives through cotton field at night" src="https://images.theconversation.com/files/488889/original/file-20221009-57880-obqrlo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488889/original/file-20221009-57880-obqrlo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488889/original/file-20221009-57880-obqrlo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488889/original/file-20221009-57880-obqrlo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488889/original/file-20221009-57880-obqrlo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=483&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488889/original/file-20221009-57880-obqrlo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=483&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488889/original/file-20221009-57880-obqrlo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=483&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Climate change likely threatens the future of cotton farming.</span>
<span class="attribution"><span class="source">Dave Hunt/AAP</span></span>
</figcaption>
</figure>
<h2>Looking ahead</h2>
<p>About 90% of Australia’s cotton crop is <a href="https://apps.fas.usda.gov/newgainapi/api/Report/DownloadReportByFileName?fileName=Cotton%20and%20Products%20Annual_Canberra_Australia_AS2022-0006.pdf">irrigated</a>. This changes each year depending on how much natural rainfall is received across the cotton-growing catchments.</p>
<p>Our research confirms rainfall extremes in the northern Murray-Darling Basin are increasing. The subsequent longer and more frequent droughts and floods are likely to lead to lower cotton yields, which may affect the livelihood of the communities dependent on cotton farming. </p>
<p>River flows are affected by both rainfall and human management of rivers, such as the allocation of water for irrigation and other uses. More accurate rainfall models are needed to help state and local water authorities make crucial management decisions. These models should predict the climate drivers identified in our study.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/while-towns-run-dry-cotton-extracts-5-sydney-harbours-worth-of-murray-darling-water-a-year-its-time-to-reset-the-balance-133342">While towns run dry, cotton extracts 5 Sydney Harbours' worth of Murray Darling water a year. It's time to reset the balance</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/191864/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joshua Hartigan receives funding from the Australian Government Research Training Program Scholarship. </span></em></p><p class="fine-print"><em><span>Lance M Leslie and Milton Speer do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Worsening droughts and flooding likely threaten the future of cotton farming – by far the most important crop in the basin.Milton Speer, Visiting Fellow, School of Mathematical and Physical Sciences, University of Technology SydneyJoshua Hartigan, PhD Candidate, University of Technology SydneyLance M Leslie, Professor, School of Mathematical And Physical Sciences, University of Technology SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1905462022-09-15T09:35:48Z2022-09-15T09:35:48Z2022’s supercharged summer of climate extremes: How global warming and La Niña fueled disasters on top of disasters<figure><img src="https://images.theconversation.com/files/484419/original/file-20220913-5271-ofelvw.jpg?ixlib=rb-1.1.0&rect=63%2C5%2C3520%2C2314&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">About a third of Pakistan flooded during the extreme monsoon in 2022, affecting an estimated 33 million people.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/PakistanMonsoonRains/8663137b7c4949ceba879d02bd203eb0/photo">AP Photo/Fareed Khan</a></span></figcaption></figure><p>There’s an old joke about the fellow who has his left foot in a bucket of ice water and the right in a bucket of hot water, so that his overall temperature is average. That seemed to apply to the climate during 2022’s northern <a href="https://www.noaa.gov/news/earth-had-its-6th-warmest-august-on-record">summer of extremes</a>.</p>
<p>Global warming is undoubtedly a factor, but just how the increasing extremes – heat waves, droughts and floods, sometimes one on top of the other – are related can be bewildering to the public and policymakers.</p>
<p>As a <a href="https://scholar.google.com/citations?user=ovnjqjMAAAAJ&hl=en">climate scientist</a>, I’ve been working on these issues for more than four decades, and my new book, “<a href="https://www.cambridge.org/us/academic/subjects/earth-and-environmental-science/climatology-and-climate-change/changing-flow-energy-through-climate-system">The changing flow of energy through the climate system</a>,” details the causes, feedbacks and impacts. Let’s take a closer look at how climate change and natural weather patterns like La Niña influence what we’re seeing around the world today.</p>
<figure class="align-center ">
<img alt="Map showing temperature anomalies, with extremes in Europe, Asia and North America." src="https://images.theconversation.com/files/484785/original/file-20220915-26-i678hd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/484785/original/file-20220915-26-i678hd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/484785/original/file-20220915-26-i678hd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/484785/original/file-20220915-26-i678hd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/484785/original/file-20220915-26-i678hd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/484785/original/file-20220915-26-i678hd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/484785/original/file-20220915-26-i678hd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The June-August 2022 global land and ocean surface temperature was 1.6 degrees Fahrenheit (0.89 Celsius) above the 20th-century average of 60.1 F (15.6 C). It tied with 2015 and 2017 as the fifth-warmest in the 143-year temperature record.</span>
<span class="attribution"><a class="source" href="https://www.noaa.gov/news/earth-had-its-6th-warmest-august-on-record">NOAA</a></span>
</figcaption>
</figure>
<h2>The Northern Hemisphere’s extreme summer</h2>
<p>Summer 2022 has indeed seemed to feature one climate-related disaster after another.</p>
<p>Record-breaking heat waves baked India and Pakistan, then monsoon flooding left <a href="https://www.cnn.com/videos/world/2022/09/07/flooding-in-pakistan-monsoon-on-steroids-coren-dnt-ebof-vpx.cnn/video/playlists/around-the-world/">about a third</a> of <a href="https://www.ft.com/content/116f34fc-b44d-487d-822b-d3f1926eaca2">Pakistan under water</a>, affecting an estimated <a href="https://www.usaid.gov/sites/default/files/documents/2022-09-09_Active_USAID-BHA_Programs_for_the_Pakistan_Floods_Response.pdf">33 million people</a>. Temperatures exceeded 104 degrees Fahrenheit (40 Celsius) for prolonged periods in many places, and even <a href="https://www.theguardian.com/environment/2022/may/25/it-seems-this-heat-will-take-our-lives-pakistan-city-fearful-jacobabad-after-hitting-51c">broke 122 F (50 C)</a> in Jacobabad, Pakistan, in May.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/484431/original/file-20220913-3897-29qp4j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Satellite images show broad areas of water" src="https://images.theconversation.com/files/484431/original/file-20220913-3897-29qp4j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/484431/original/file-20220913-3897-29qp4j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/484431/original/file-20220913-3897-29qp4j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/484431/original/file-20220913-3897-29qp4j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/484431/original/file-20220913-3897-29qp4j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/484431/original/file-20220913-3897-29qp4j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/484431/original/file-20220913-3897-29qp4j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A satellite image of one part of Pakistan shows how flooding turned rivers into lakes several miles wide.</span>
<span class="attribution"><a class="source" href="https://www.esa.int/ESA_Multimedia/Images/2022/09/Pakistan_inundated">European Space Agency</a></span>
</figcaption>
</figure>
<p>The Asian heat helped to melt some glaciers in the Himalayas, elevating rivers. At the same time, <a href="https://doi.org/10.1038/d41586-022-02813-6">three times the normal annual rain</a> fell in Pakistan during the weekslong monsoon. More than <a href="http://cms.ndma.gov.pk/storage/app/public/situation-reports/September2022/Pe9B2usbMkYOGHC3GRMC.pdf">1,500 people died</a> in the flooding, an estimated <a href="https://reliefweb.int/report/pakistan/pakistan-floods-fact-sheet-5-fiscal-year-fy-2022">1.8 million homes</a> were damaged or destroyed, and <a href="https://www.usaid.gov/sites/default/files/documents/2022-09-09_USAID-BHA_Pakistan_Floods_Fact_Sheet_4.pdf">hundreds of thousands of livestock</a> were lost. Food for the coming seasons will be in short supply.</p>
<p>Extreme heat in Europe led to wildfires, especially in Spain and Portugal. The drought in Spain dried up a reservoir, revealing the long-submerged “<a href="https://www.nytimes.com/2022/09/09/science/stonehenge-spain-guadalperal-archaeology.html">Spanish Stonehenge</a>,” an ancient circle of megalithic stones believed to date back to around 5000 B.C. Electricity generation in France plummeted, with low rivers reducing the ability to cool nuclear power towers, and German barges had difficulty finding enough water to <a href="https://www.bbc.com/future/article/20220912-are-drying-rivers-a-warning-of-europes-tomorrow">navigate the Rhine River</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/484418/original/file-20220913-4889-396tup.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A man beats at flaming grasses with a shovel. Fire-blackened landscape is in the background." src="https://images.theconversation.com/files/484418/original/file-20220913-4889-396tup.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/484418/original/file-20220913-4889-396tup.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/484418/original/file-20220913-4889-396tup.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/484418/original/file-20220913-4889-396tup.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/484418/original/file-20220913-4889-396tup.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/484418/original/file-20220913-4889-396tup.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/484418/original/file-20220913-4889-396tup.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Residents fought wildfires in Spain in July 2022 that spread through dry fields and forests.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/APWeekinPicturesEuropeandAfrica/c233074659734a508cbf90c3423ea4d7/photo">AP Photo/Bernat Armangue</a></span>
</figcaption>
</figure>
<p>In the United States, the West and the Midwest suffered through intense heat waves, and the crucial Colorado River reservoirs <a href="https://apnews.com/article/lake-powell-drought-hydropower-colorado-river-619790b577eabc81cfa2d9b9b6ca2fe1">Lake Powell</a> and <a href="https://earthobservatory.nasa.gov/images/150111/lake-mead-keeps-dropping">Lake Mead hit record lows</a>, triggering water restrictions. Yet, the country also saw <a href="https://www.washingtonpost.com/climate-environment/2022/08/23/flood-united-states-climate-explainer">major disruptive flooding in several cities and regions</a>, from Death Valley to the mountains of eastern Kentucky.</p>
<p>In China, heat waves and drought stretched over eight weeks and <a href="https://multimedia.scmp.com/infographics/news/china/article/3190803/china-drought/index.html">dried up parts of the Yangtze River</a> to the lowest level since at least 1865 – until parts of the same area were inundated with flooding rains in August.</p>
<h2>Climate change exacerbates the extremes</h2>
<p>Yes, these are all manifestations of climate change brought about by human activities.</p>
<p>Climate change for the most part does not directly cause the rainfall or drought, but it makes these naturally occurring events more intense or severe. Carbon dioxide and other greenhouse gases, largely from power plants, vehicles, buildings, industry and agriculture, trap heat in the atmosphere, heating the planet.</p>
<p>In addition to raising temperature, global warming increases <a href="https://doi.org/10.1088/2752-5295/ac6f74">evaporation of surface waters</a> into the atmosphere, drying areas that have had little rain. Warmer air increases the amount of water vapor the atmosphere can hold, and the thirstier atmosphere sucks moisture from the surface.</p>
<figure class="align-center ">
<img alt="Illustration showing a loop of precipitation, evaporation, runoff and storage" src="https://images.theconversation.com/files/484448/original/file-20220913-5073-qgyo2h.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/484448/original/file-20220913-5073-qgyo2h.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=602&fit=crop&dpr=1 600w, https://images.theconversation.com/files/484448/original/file-20220913-5073-qgyo2h.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=602&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/484448/original/file-20220913-5073-qgyo2h.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=602&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/484448/original/file-20220913-5073-qgyo2h.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=757&fit=crop&dpr=1 754w, https://images.theconversation.com/files/484448/original/file-20220913-5073-qgyo2h.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=757&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/484448/original/file-20220913-5073-qgyo2h.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=757&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Key elements of the water cycle.</span>
<span class="attribution"><span class="source">Global Energy and Water Exchanges</span></span>
</figcaption>
</figure>
<p>That extra moisture is carried away by winds and eventually flows into storms, often a thousand miles distant, that rain harder. Atmospheric moisture has <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">increased by 5% to 20%</a> in general compared with the pre-1970s. The increase in water vapor, a greenhouse gas, <a href="https://climate.nasa.gov/ask-nasa-climate/3143/steamy-relationships-how-atmospheric-water-vapor-amplifies-earths-greenhouse-effect">further amplifies warming</a>. When water evaporates, it absorbs heat, and when it later falls as rain, that heat is released back into the atmosphere. This extra energy fuels storms, leading to more intense systems that may also be bigger and last longer, with <a href="https://doi.org/10.1007/s10712-012-9214-y">up to 30% more rain</a> as a consequence of warming.</p>
<figure class="align-center ">
<img alt="Two children cling to a woman as they walk through nearly waist-deep water on a city street in pouring rain." src="https://images.theconversation.com/files/484434/original/file-20220913-20-sonkk7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/484434/original/file-20220913-20-sonkk7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/484434/original/file-20220913-20-sonkk7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/484434/original/file-20220913-20-sonkk7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/484434/original/file-20220913-20-sonkk7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/484434/original/file-20220913-20-sonkk7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/484434/original/file-20220913-20-sonkk7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A warming climate can lead to more extreme downpours, as Bangladesh and India experienced in 2022.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/woman-with-children-wades-along-flooded-street-during-a-news-photo/1241384534">AFP via Getty Images</a></span>
</figcaption>
</figure>
<p>On average, precipitation falls on only <a href="https://doi.org/10.1175/BAMS-D-17-0107.1">about 8% of the land</a> globally at any time. It is the intermittency of precipitation that leads to the exaggerated extremes, resulting in localized heavy rains and widespread dry spells.</p>
<p>So, with the accelerated water cycle, wet areas get wetter, and dry areas get drier, while over the oceans, this results in <a href="https://doi.org/10.1175/JCLI-D-20-0366.1">salty waters becoming saltier and fresh waters becoming fresher</a>. </p>
<h2>Infrastructure isn’t ready for the consequences</h2>
<p>The impact of these events and whether they turn into disasters depend in part on how prepared communities are for the changes. Most infrastructure, forests and farms are adapted to a previous climate.</p>
<p>Whether heavy rains result in flooding <a href="https://theconversation.com/intense-heat-and-flooding-are-wreaking-havoc-on-power-and-water-systems-as-climate-change-batters-americas-aging-infrastructure-189761">depends critically on drainage systems</a> and surface water management.</p>
<p>When populations grow, as Pakistan’s has, more people become vulnerable when they <a href="https://theconversation.com/dallas-is-only-the-latest-fl%20ood-disaster-what-cities-can-learn-from-todays-climate-crises-to-prepare-for-tomorrows-189293">settle in flood plains</a>. It takes time for surface waters to evaporate, and flood water runoff is affected by <a href="https://theconversation.com/ocean-heat-is-at-record-levels-with-major-consequences-174760">rising sea levels</a> that slow and may even reverse stream and river flows to the ocean.</p>
<figure class="align-center ">
<img alt="A girl in rain boots walks through a mud-filled yard. Damaged mattresses and other belongings from a flooded house are piled nearby." src="https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=452&fit=crop&dpr=1 600w, https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=452&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=452&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=568&fit=crop&dpr=1 754w, https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=568&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=568&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Flash flooding swept through mountain valleys in eastern Kentucky in July 2022, killing more than three dozen people. It was one of several destructive flash floods in the U.S.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/local-fire-chief-and-his-daughter-drop-off-goods-for-a-news-photo/1242236541">Seth Herald/AFP via Getty Images</a></span>
</figcaption>
</figure>
<h2>Natural variability also plays a major role</h2>
<p>While the observed increases in extremes are a consequence of climate change, the weather events themselves are still largely naturally occurring.</p>
<p>Two naturally reoccurring weather patterns are important to understand: La Niña and El Niño – the two opposite phases of the <a href="https://www.weather.gov/mhx/ensowhat">El Niño-Southern Oscillation</a>.</p>
<p>In 2022, we are <a href="https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml">likely headed</a> into a third year of a <a href="https://www.climate.gov/news-features/understanding-climate/el-ni%C3%B1o-and-la-ni%C3%B1a-frequently-asked-questions">La Niña event</a>, in which cool waters dominate the central and eastern tropical Pacific. The pattern affects atmospheric circulation, keeping the main rains over southern Asia and the Indonesian region, and with associated record-breaking marine heat waves in the North and South Pacific. In North America, it typically means the southern half of the U.S. is drier than normal.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/484232/original/file-20220913-14-93xfhv.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A global map with contours shows higher than normal temperatures in much of the planet, particularly the Arctic." src="https://images.theconversation.com/files/484232/original/file-20220913-14-93xfhv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/484232/original/file-20220913-14-93xfhv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=387&fit=crop&dpr=1 600w, https://images.theconversation.com/files/484232/original/file-20220913-14-93xfhv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=387&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/484232/original/file-20220913-14-93xfhv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=387&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/484232/original/file-20220913-14-93xfhv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=486&fit=crop&dpr=1 754w, https://images.theconversation.com/files/484232/original/file-20220913-14-93xfhv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=486&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/484232/original/file-20220913-14-93xfhv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=486&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Surface temperatures increased over most of the planet from 1979 to 2021, with parts of the Arctic rising as much as 5 F (3 C).</span>
<span class="attribution"><span class="source">Courtesy of Dennis Hartmann</span></span>
</figcaption>
</figure>
<p>In the Southern Hemisphere, that marine heat wave over the South Pacific led to the warmest and wettest meteorological winter (June-August) on record in New Zealand, with <a href="https://niwa.co.nz/climate/summaries/seasonal/winter-2022">several major floods</a>. Rain was 141% of “normal,” and nationwide temperatures averaged 2.5 F (1.4 C) above the 1981-2010 average. The exceptionally high sea surface temperatures not only contributed to warmer temperatures on land, but also fed atmospheric rivers and provided extra moisture to onshore winds and storms. </p>
<p>The La Niña cooling in the tropical Pacific can readily reverse, with an El Niño pattern effectively pumping heat out of the ocean and into the atmosphere. A preliminary analysis colleagues and I conducted suggests that the <a href="https://doi.org/10.1007/s00376-022-1461-3">global ocean heat content is at record-high levels</a>. Exceptionally warm deep waters in the tropical western Pacific right now suggest prospects for the next El Niño event in 2023, potentially resulting in more global temperature records in 2024 as some ocean heat returns to the atmosphere.</p>
<figure class="align-center ">
<img alt="A map of sea surface temperature anomalies show high temperatures near New Zealand and off Russia, Alaska and Japan." src="https://images.theconversation.com/files/484230/original/file-20220913-20-alu7fo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/484230/original/file-20220913-20-alu7fo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=272&fit=crop&dpr=1 600w, https://images.theconversation.com/files/484230/original/file-20220913-20-alu7fo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=272&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/484230/original/file-20220913-20-alu7fo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=272&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/484230/original/file-20220913-20-alu7fo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=342&fit=crop&dpr=1 754w, https://images.theconversation.com/files/484230/original/file-20220913-20-alu7fo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=342&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/484230/original/file-20220913-20-alu7fo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=342&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">August 2022 had a distinct La Niña weather pattern, with cold waters in the tropical Pacific and intense marine heat waves in the North and South Pacific. The temperatures are compared to the 1991-2020 average.</span>
<span class="attribution"><a class="source" href="https://www.weather.gov/ict/enso">NOAA</a></span>
</figcaption>
</figure>
<p>All La Niñas are not the same, however. Because of how sea temperatures responded to the heat in the extratropics, the environment today is very different than it was two years ago. Warmth in the North Pacific could have consequences for the “pineapple express” and other West Coast U.S. storms this coming winter.</p>
<p>The natural variability component means that we should not simply expect more of the same every year. As we likely go into an El Niño next year and global temperatures get a boost, extremes will shift to new locations.</p>
<p><em>This article was updated Sept. 15, 2022, with the Pakistan death toll rising to more than 1,500.</em></p><img src="https://counter.theconversation.com/content/190546/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kevin Trenberth does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A climate scientist explains the forces behind the summer’s extreme downpours and dangerous heat waves, and why new locations will be at risk in the coming year.Kevin Trenberth, Distinguished Scholar, NCAR; Affiliated Faculty, University of Auckland, Waipapa Taumata RauLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1593832022-08-29T13:07:42Z2022-08-29T13:07:42ZHow safe is it to drink rainwater?<figure><img src="https://images.theconversation.com/files/481568/original/file-20220829-26-3te7ch.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There are concerns about how safe rainwater is to drink.</span> </figcaption></figure><p><em>In many parts of the world, including Africa, people rely on <a href="https://iwaponline.com/washdev/article/10/3/502/74755/Rainwater-harvesting-and-primary-uses-among-rural">rainwater as a source of drinking water</a>, as well as for other <a href="https://blogs.worldbank.org/water/roofs-rain-and-life-rainwater-harvesting-safe-water-supply-and-sustainable-co-benefits">household and livelihood uses</a>. One of the reasons is water scarcity – sub-Saharan Africa has the <a href="https://www.intechopen.com/chapters/63707">largest number of water-scarce countries</a> in the world. But there are concerns about how safe rainwater is to drink. It can be <a href="https://orca.cardiff.ac.uk/id/eprint/150054/1/washdev0100502.pdf">contaminated</a> by dust and ash in the surroundings or by heavy metal from roofing material. Another concern is the presence of manufactured chemicals called perfluoroalkyl and polyfluoroalkyl substances (PFAS), or “forever chemicals”. As environmental scientist Ian Cousins and his team explain, they are a threat to the use of rainwater for domestic purposes.</em></p>
<iframe id="noa-web-audio-player" style="border: none" src="https://embed-player.newsoveraudio.com/v4?key=x84olp&id=https://theconversation.com/how-safe-is-it-to-drink-rainwater-159383&bgColor=F5F5F5&color=D8352A&playColor=D8352A" width="100%" height="110px"></iframe>
<h2>What are PFAS and why should we be worried about them?</h2>
<p>PFAS are a group of man-made substances often described as “forever chemicals” because they never <a href="https://pubs.rsc.org/en/content/articlelanding/2020/em/d0em00355g">break down in the environment</a>. </p>
<p>They are found everywhere – in air, soil, and water as well as in wildlife, plants and humans. They can be found on the highest mountains, in the deep oceans and on both poles. A <a href="https://pubs.acs.org/doi/10.1021/acs.est.2c02765">recent study</a> highlighted the widespread presence of PFAS in rainwater, from the Tibetan Plateau to Antarctica, and noted that according to recently published health advisories, rainwater everywhere could be considered unsafe to drink. </p>
<p>According to the US Environmental Protection Agency, there are <a href="https://comptox.epa.gov/dashboard/chemical-lists/PFASMASTER">more than 12,000 of these chemicals </a> in use. They have been produced and used on a large scale in a wide range of <a href="https://pubs.rsc.org/en/content/articlelanding/2020/em/d0em00291g">industrial and commercial applications</a> since the second world war. Well-known uses include fire-fighting foams, non-stick cookware, and paper and board used to wrap and contain food. There are hundreds of uses, too numerous to list.</p>
<p>The human exposure pathways and health effects of <a href="https://pubs.acs.org/doi/10.1021/acs.est.6b04806">most of the chemicals are poorly understood</a> or unknown, except for four about which there is good information. They are: PFOS (perfluorooctanesulfonic acid), PFOA (perfluorooctanoic acid), PFHxS (perfluorohexanesulfonic acid) and PFNA (perfluorononanoic acid). </p>
<p>At elevated levels of exposure, these four have been associated with serious <a href="https://www.atsdr.cdc.gov/pfas/index.html">human health harms</a>, including different forms of cancer, development toxicity, infertility and pregnancy complications, high cholesterol, ulcerative colitis, liver hypertrophy (“enlargement”), and thyroid disease. </p>
<p>The recent extremely low advisories for drinking water were prompted by the observation that exposure to these chemicals can lead to <a href="https://www.mdpi.com/1660-4601/14/7/691/htm">decreased vaccine effectiveness</a> in children.</p>
<p>PFAS have been used for a long time. But intensive research on them began only about 20 years ago. Since then, the knowledge of toxicity has increased enormously. Based on this knowledge, the exposure level that is considered safe for humans has <a href="https://setac.onlinelibrary.wiley.com/doi/full/10.1002/etc.4863">been set lower and lower</a>.</p>
<p>The PFAS levels in health advisories for <a href="https://www.efsa.europa.eu/en/news/pfas-food-efsa-assesses-risks-and-sets-tolerable-intake">food</a> and <a href="https://www.epa.gov/sdwa/drinking-water-health-advisories-pfoa-and-pfos">drinking water</a> have been reduced to a point that is hard to achieve. This is because the advisory values are close to or even higher than the PFAS level in the environment. </p>
<p>In our <a href="https://www.epa.gov/sdwa/drinking-water-health-advisories-pfoa-and-pfos">recent study</a> we showed that levels of certain PFAS in rainwater now exceed the guidelines set by the US Environmental Protection Agency even in the remotest regions of the Earth. </p>
<p>It is important to note that the levels of the four PFAS in rainwater and other environmental media have not increased recently. The use and emission of these <a href="https://pubs.acs.org/doi/10.1021/acs.est.6b04806">so-called “legacy” PFAS</a> was discontinued in many countries in recent years. But their stability means that they will remain in the environment indefinitely.</p>
<p>The <a href="https://environmentalevidencejournal.biomedcentral.com/articles/10.1186/s13750-017-0114-y">levels of the four PFAS</a> in the atmosphere have been stable since they were first measured in the early 2000s, which means their levels have been above the most recent drinking water advisories since then.</p>
<p>The situation will also not improve soon. PFAS do not not break down in the environment. Their only route for removal from environments where we produce food is <a href="https://pubs.acs.org/doi/10.1021/es0512475">slow dilution into the deep oceans</a>. Rainwater levels may take decades to fall below the levels set in health advisories. The exact recovery time is uncertain.</p>
<h2>How are people most exposed?</h2>
<p>For the four well-studied PFAS, <a href="https://www.nature.com/articles/s41370-018-0094-1">humans are exposed</a> primarily through food, drinking water and household dust. Food and drinking water are contaminated primarily by the environment. </p>
<p>For the larger class of PFAS, human exposure pathways vary enormously, and there are many thousands of other PFAS that are not monitored or studied at all, so we know nothing about their exposure levels or toxicities, which is concerning.</p>
<p>There are <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/rem.21553">ways to remove</a> PFAS from water, but it is not clear if the levels can be brought below the latest health advisories. </p>
<p>Regular vacuuming can reduce dust exposure, but there is no way to remove PFAS from food. Therefore, it is not possible to completely avoid exposure to low-level PFAS. Humans will have to live with it. </p>
<h2>Is it safe to drink rainwater?</h2>
<p>We are uncertain. It is unlikely that many of the effects listed above would be observed at very low exposure levels, of pg/L or ng/L (picogram/litre and nanogram/litre are units of concentration). An effect that might be observed at these low levels is the decreased effectiveness of vaccines. </p>
<p>The health advisories are set so low because the authorities want to be close to certain that no effects will occur at those levels. The precautionary assumptions are used to ensure that the public is protected. Therefore, we have to hope that some effects on the large scale will not occur, but we cannot be certain.</p>
<h2>What lessons can be learned?</h2>
<p>There are more than 12,000 PFAS currently in use, with hundreds of individual uses. All PFAS are man-made and, therefore, they have no place in the natural environment. Due to concerns about their eternal presence and potential toxicities, scientists have suggested that PFAS should only be used where they are <a href="https://pubs.rsc.org/en/content/articlelanding/2019/em/c9em00163h">essential</a> and that the essentiality of every PFAS used should be evaluated.</p><img src="https://counter.theconversation.com/content/159383/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Rainwater may be contaminated with chemicals and scientists are still uncertain about their effects.Ian Cousins, Professor of Contaminant Chemistry, Stockholm UniversityBo Sha, PhD Candidate, Stockholm UniversityJana H. Johansson, Researcher, Department of Environmental Science, Stockholm UniversityMartin Scheringer, Senior scientist, Swiss Federal Institute of Technology ZurichMatthew Salter, Researcher, Department of Environmental Science, Stockholm UniversityLicensed as Creative Commons – attribution, no derivatives.