tag:theconversation.com,2011:/us/topics/heavy-rainfall-36229/articlesHeavy rainfall – The Conversation2024-01-17T02:38:02Ztag: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>
<hr>
<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>
<hr>
<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/2137242023-09-19T12:18:13Z2023-09-19T12:18:13ZAs extreme downpours trigger flooding around the world, scientists take a closer look a global warming’s role<p>Torrential downpours sent muddy water racing through streets in <a href="https://www.washingtonpost.com/world/2023/09/14/libya-flood-death-toll-derna-news/">Libya</a>, <a href="https://twitter.com/WxNB_/status/1699014872015479212">Greece</a> and <a href="https://www.theguardian.com/world/2023/sep/05/boy-rescued-from-flood-waters-after-record-heavy-rain-in-spain">Spain</a> and flooded parts of <a href="https://www.straitstimes.com/asia/east-asia/hong-kong-hit-with-heavy-rain-flooding-days-after-typhoon">Hong Kong</a> and <a href="https://www.nytimes.com/2023/09/29/nyregion/nyc-flooding-video-photo.html">New York City</a> in September 2023. Thousands of people died in the city of Derna, Libya. Zagora, Greece, saw a record 30 inches of rain, the equivalent of <a href="https://public.wmo.int/en/media/news/storm-daniel-leads-extreme-rain-and-floods-mediterranean-heavy-loss-of-life-libya">a year and a half of rain falling in 24 hours</a>.</p>
<p>A few weeks earlier, monsoon rains triggered deadly landslides and flooding in <a href="https://www.youtube.com/watch?v=8VMBIlKjuKg">the Himalayas</a> that <a href="https://www.pbs.org/newshour/world/heavy-rain-landslides-have-killed-at-least-72-people-this-week-in-indias-himalayas">killed dozens of people</a> in India.</p>
<p>After severe flooding on almost every continent this year, including <a href="https://theconversation.com/epic-snow-from-all-those-atmospheric-rivers-in-the-west-is-starting-to-melt-and-the-flood-danger-is-rising-203874">mudslides and flooding in California</a> in early 2023 and devastating <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">floods in Vermont and New York</a> in July, it can seem like extreme rainfall is becoming more common.</p>
<p>So, what role does global warming play in this? And importantly, what can we do to adapt to this new reality?</p>
<figure class="align-center ">
<img alt="A man and woman sit on a park bench with water up to the man's knees. The woman is sitting on the chair back. A car in the street is flooded up to the roof." src="https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.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 powerful storm system in 2023 flooded communities across Vermont and left large parts of the capital, Montpelier, underwater.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/michelle-whitehouse-and-her-husband-will-whitehouse-from-news-photo/1526471468">John Tully for The Washington Post via Getty Images</a></span>
</figcaption>
</figure>
<p>As a <a href="https://clasp.engin.umich.edu/people/mohammed-ombadi/">climate scientist</a> with a background in civil engineering, I am interested in exploring the links between the science of climate change and extreme weather events on one hand and the impacts those events have on our daily lives on the other. Understanding the connections is crucial in order to develop sound strategies to adapt to climate change.</p>
<h2>Thirstier atmosphere, more extreme precipitation</h2>
<p>As temperatures rise, the warmer atmosphere can <a href="https://sealevel.jpl.nasa.gov/ocean-observation/understanding-climate/air-and-water/">hold more water vapor</a>. Evaporation of water from land and oceans also increases. That water has to eventually come back to land and oceans. </p>
<p>Simply, as the atmosphere absorbs more moisture, it dumps more precipitation during storms. Scientists expect about a <a href="https://science2017.globalchange.gov/chapter/7/">7% increase</a> in precipitation intensity during extreme storms for every 1 degree Celsius (1.8 degrees Fahrenheit) of warming. </p>
<p>This increase in the amount of moisture that air can hold is what scientists call the <a href="https://doi.org/10.1073/pnas.2304077120">Clausius Clapeyron relationship</a>. But other factors, such as changes in wind patterns, <a href="https://doi.org/10.1073/pnas.2304077120">storm tracks and how saturated the air is</a>, also play a role in how intense the precipitation is.</p>
<h2>Liquid vs. frozen: Rain matters most</h2>
<p>One factor that determines the severity of floods is whether water falls as rain or snow. The almost instantaneous runoff from rain, as opposed to the slower release of water from melting snow, leads to more severe flooding, landslides and other hazards – particularly in mountain regions and areas downstream, where about a quarter of the global population lives. </p>
<p>A higher proportion of extreme rainfall rather than snow is believed to have been a key contributor to the <a href="https://www.bbc.com/news/world-asia-india-66519698">devastating floods and landslides in the Himalayas</a> in August 2023, though research is still underway to confirm that. Additionally, a <a href="https://doi.org/10.1029/2019WR025571">2019 examination of flood patterns</a> across 410 watersheds in the Western U.S. found that the largest runoff peaks driven by rainfall were more than 2.5 times greater than those driven by snowmelt.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Maps show the US and other regions of the Northern Hemisphere with rising rainfall intensity. Western North America and the Himalayas stand out" src="https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?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"></a>
<figcaption>
<span class="caption">Rainfall intensity is projected to increase more in certain regions by the end of the 21st century, based on climate model data. Light colors show a twofold increase and dark colors indicate an eightfold increase in future rainfall extremes compared to the recent past.</span>
<span class="attribution"><span class="source">Mohammed Ombadi.</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>In a <a href="https://doi.org/10.1038/s41586-023-06092-7">2023 study in the journal Nature</a>, my colleagues and I demonstrated that the intensity of extreme precipitation is increasing at a faster rate than the Clausius Clapeyron relationship would suggest – up to 15% per 1 C (1.8 F) of warming – in high-latitude and mountain regions such as the Himalayas, Alps and Rockies.</p>
<p>The reason for this amplified increase is that rising temperatures are shifting precipitation toward more rain and less snow in these regions. A larger proportion of this extreme precipitation is falling as rain.</p>
<p>In our study, we looked at the heaviest rains in the Northern Hemisphere since the 1950s and found that the increase in the intensity of extreme rainfall varied with altitude. Mountains in the American West, parts of the Appalachian Mountains, the Alps in Europe and the Himalayas and Hindu Kush mountains in Asia also showed strong effects. Furthermore, climate models suggest that most of these regions are likely to see a sevenfold-to-eightfold increase in the occurrence of extreme rainfall events by the end of the 21st century.</p>
<h2>Flooding isn’t just a short-term problem</h2>
<p>Deaths and damage to homes and cities capture the lion’s share of attention in the aftermath of floods, but increased flooding also has long-term effects on water supplies in reservoirs that are crucial for communities and agriculture in many regions. </p>
<p>For example, in the Western U.S., reservoirs are often kept as close to full capacity as possible during the spring snowmelt to provide water for the dry summer months. The mountains act as natural reservoirs, storing winter snowfall and then releasing the melted snow at a slow pace.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=527&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=527&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=527&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A series of atmospheric rivers in California dumped so much water on the region that Tulare Lake, which had dried up years earlier, reemerged as water spread 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>However, <a href="https://doi.org/10.1038/s41586-023-06092-7">our recent findings</a> suggest that with the world rapidly shifting toward a climate dominated by heavy downpours of rain – not snow – water resource managers will increasingly have to leave more room in their reservoirs to store large amounts of water in anticipation of disasters to minimize the risk of flooding downstream.</p>
<h2>Preparing for a fiercer future</h2>
<p>Global efforts to reduce greenhouse gas emissions have been increasing, but people still need to prepare for a fiercer climate. The destructive <a href="https://public.wmo.int/en/media/news/storm-daniel-leads-extreme-rain-and-floods-mediterranean-heavy-loss-of-life-libya">storms that hit the Mediterranean region</a> in 2023 provide a cogent case for the importance of adaptation. They shattered records for extreme precipitation across many countries and caused extensive damage.</p>
<p>A main factor that contributed to the catastrophe in Libya was the <a href="https://theconversation.com/libya-dam-collapse-happened-because-of-bad-management-not-bad-weather-213546">bursting of aging dams</a> that had managed water pouring down from <a href="https://www.washingtonpost.com/world/2023/09/12/deadly-libya-flooding-cause/">mountainous terrain</a>.</p>
<p>This underscores the importance of updating design codes so infrastructure and buildings are built to survive future downpours and flooding, and investing in new engineering solutions to improve resiliency and protect communities from extreme weather. It may also mean <a href="https://theconversation.com/managed-retreat-done-right-can-reinvent-cities-so-theyre-better-for-everyone-and-avoid-harm-from-flooding-heat-and-fires-163052">not building in regions</a> with high future risks of flooding and landslides.</p>
<p><em>This article, originally published Sept. 19, 2023, has been updated with flooding in New York City.</em></p><img src="https://counter.theconversation.com/content/213724/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mohammed Ombadi has received funding from Lawrence Berkeley National Laboratory to conduct the Nature study discussed in this article. </span></em></p>There’s a rule of thumb that rainfall intensity increases by about 7% per degree Celsius as temperatures rise. But the increase is much higher in the mountains, scientists found.Mohammed Ombadi, Assistant Professor of Climate and Space Sciences Engineering, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2094762023-07-11T12:30:09Z2023-07-11T12:30:09ZHow climate change intensifies the water cycle, fueling extreme rainfall and flooding – the Northeast deluge was just the latest<figure><img src="https://images.theconversation.com/files/536673/original/file-20230710-23-sbqqq8.jpg?ixlib=rb-1.1.0&rect=60%2C84%2C7981%2C5268&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">People were trapped in stores as floodwater swept through Highland Falls, N.Y., on July 9, 2023.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/NortheastFlooding/dca30eef58f149d493b8770a86c59d4c/photo">AP Photo/John Minchillo</a></span></figcaption></figure><p>Powerful storm systems that hit the U.S. Northeast starting July 9, 2023, dumped <a href="https://twitter.com/cory_kowitz/status/1678276566135246849">close to 10 inches of rain</a> on New York’s Lower Hudson Valley in less than a day and sent mountain rivers spilling over their banks and <a href="https://weather.com/news/news/2023-07-11-vermont-montpelier-ludlow-new-york-flooding">into towns across Vermont</a>. Vermont <a href="https://www.mynbc5.com/article/gov-scott-issues-state-of-emergency-in-anticipation-of-flash-flooding-sunday-and-monday/44485743">Gov. Phil Scott said</a> he hadn’t seen rainfall like it since <a href="https://www.burlingtonfreepress.com/story/life/2021/08/27/hurricane-irene-vt-tropical-storm-phish-concert-10-years-later-storm-preparedness-winooski-river/5599530001/">Hurricane Irene devastated the region</a> in 2011. </p>
<p>Extreme water disasters like this have disrupted lives in countries around the world in the past few years, from the Alps and <a href="https://www.science.org/content/article/europe-s-deadly-floods-leave-scientists-stunned">Western Europe</a> to <a href="https://disasterphilanthropy.org/disasters/2022-pakistan-floods/">Pakistan</a>, <a href="https://www.cnn.com/2022/06/22/india/bangladesh-india-floods-death-toll-intl-hnk/index.html">India</a> and <a href="https://www.bbc.com/news/world-australia-61991112">Australia</a>, along with <a href="https://theconversation.com/looking-back-on-americas-summer-of-heat-floods-and-climate-change-welcome-to-the-new-abnormal-190636">several U.S. states in 2022</a> and <a href="https://theconversation.com/historic-flooding-in-fort-lauderdale-was-a-sign-of-things-to-come-a-look-at-who-is-most-at-risk-and-how-to-prepare-204101">2023</a>.</p>
<p>The role of climate change is becoming increasingly evident in these types of deluges.</p>
<figure class="align-center ">
<img alt="Extreme rainfall flooded streets along the Hudson River, which is in the background. Water still pours down a hillside." src="https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.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">Cars were stranded in floodwater on the campus of the United States Military Academy at West Point, N.Y., on July 10, 2023.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/NortheastFlooding/e39624eb3cca4e1d849e0b74679ca4c6/photo">U.S. Military Academy via AP</a></span>
</figcaption>
</figure>
<p>Studies by scientists around the world show that the water cycle has been intensifying and will continue to intensify as the planet warms. An <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">international climate assessment</a> I co-authored in 2021 for the Intergovernmental Panel on Climate Change reviewed the research and laid out the details.</p>
<p>It documented an increase in both wet extremes, including more intense rainfall over most regions, and dry extremes, including drying in the Mediterranean, southwestern Australia, southwestern South America, South Africa and western North America. It also shows that both wet and dry extremes will continue to increase with future warming.</p>
<h2>Why is the water cycle intensifying?</h2>
<p>Water cycles through the environment, moving between the atmosphere, ocean, land and reservoirs of frozen water. It might fall as rain or snow, seep into the ground, run into a waterway, join the ocean, freeze or evaporate back into the atmosphere. In recent decades, there has been an <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">overall increase in the rates</a> of precipitation and evaporation.</p>
<p>A number of factors are intensifying the water cycle, but one of the most important is that warming temperatures raise the upper limit on the amount of moisture in the air. That increases the potential for more rain.</p>
<p><iframe id="zBAAz" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/zBAAz/5/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>This aspect of climate change is confirmed across <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">all of our lines of evidence</a>. It is expected from basic physics, projected by computer models, and it already shows up in the observational data as a general increase of rainfall intensity with warming temperatures.</p>
<p>Understanding this and other changes in the water cycle is important for more than preparing for disasters. Water is an essential resource for all ecosystems and human societies, and particularly agriculture.</p>
<h2>What does this mean for the future?</h2>
<p>An intensifying water cycle means that both wet and dry extremes and the general variability of the water cycle will increase, although not uniformly around the globe.</p>
<p>Rainfall intensity is <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">expected to increase for most land areas</a>, but the largest increases in dryness are expected in the Mediterranean, southwestern South America and western North America.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Maps showing precipitation projections and warming projections at 1.5 and 3 degrees Celsius." src="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.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">Annual average precipitation is projected to increase in many areas as the planet warms, particularly in the higher latitudes.</span>
<span class="attribution"><a class="source" href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">IPCC Sixth Assessment Report</a></span>
</figcaption>
</figure>
<p>Globally, daily extreme precipitation events will likely intensify by about <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">7% for every 1 degree Celsius</a> (1.8 degrees Fahrenheit) that global temperatures rise.</p>
<p>Many other important aspects of the water cycle <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">will also change</a> in addition to extremes as global temperatures increase, the report shows, including reductions in mountain glaciers, decreasing duration of seasonal snow cover, earlier snowmelt and contrasting changes in monsoon rains across different regions, which will impact the water resources of billions of people.</p>
<h2>What can be done?</h2>
<p>One common theme across these aspects of the water cycle is that <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">higher greenhouse gas emissions lead to bigger impacts</a>.</p>
<p>The IPCC does not make policy recommendations, but the results show what the implications of different choices are likely to be.</p>
<p>One thing the <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">scientific evidence in the report</a> clearly tells world leaders is that limiting global warming to the international target of 1.5 C (2.7 F) will require immediate, rapid and large-scale reductions in greenhouse gas emissions.</p>
<p>As the evidence shows, every fraction of a degree matters.</p>
<p><em>This updates an <a href="https://theconversation.com/climate-change-is-intensifying-the-water-cycle-bringing-more-powerful-storms-and-flooding-heres-what-the-science-shows-187951">article originally published</a> July 29, 2022, with flash flooding in the Northeast.</em></p><img src="https://counter.theconversation.com/content/209476/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mathew Barlow received travel funding from the US government to attend three IPCC lead author meetings.</span></em></p>Parts of New York’s Hudson Valley were hit with 10 inches of rain, and the mountains of Vermont – where runoff can quickly turn deadly – saw some its worst flooding since Hurricane Irene.Mathew Barlow, Professor of Climate Science, UMass LowellLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2069582023-07-06T04:06:23Z2023-07-06T04:06:23ZHere’s why climate change isn’t always to blame for extreme rainfall<p>Extreme rain and floods can trigger <a href="https://www.climatecouncil.org.au/climate-council-floods-statement/">claims</a> climate change is to blame. But these claims are not always well founded.</p>
<p>In our <a href="https://www.nature.com/articles/s41561-023-01223-1">new paper</a> in Nature Geoscience, we discuss what can and can’t be attributed to climate change straight after extreme rain events. We use the floods of early 2022 in eastern Australia as a case study.</p>
<p>We know a warmer atmosphere can hold more moisture, so it would seem reasonable to say climate change makes extreme rain events worse. But this really only applies to short, heavy downpours. For longer duration events, the climate change signal tends to be weaker and more variable. </p>
<p>We hope our suggestions will improve the quality of scientific statements in the media and, ultimately, increase public understanding of climate change effects on extreme weather.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1500638399811645441"}"></div></p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/on-our-wettest-days-stormclouds-can-dump-30-trillion-litres-of-water-across-australia-191949">On our wettest days, stormclouds can dump 30 trillion litres of water across Australia</a>
</strong>
</em>
</p>
<hr>
<h2>The early 2022 Australian floods</h2>
<p>In late February and early March 2022, persistent extreme rainfall caused severe floods across much of the east coast of Australia. Many <a href="http://www.bom.gov.au/climate/current/statements/scs76.pdf?20220525">new rainfall records</a> were set. </p>
<p>Brisbane recorded three consecutive days of over 200mm for the first time and Sydney experienced 16 wet days in a row, tying with a previous record. Much of southeast Queensland and northeast New South Wales had the wettest week since at least 1900.</p>
<p>The floods came towards the end of a <a href="https://theconversation.com/la-nina-3-years-in-a-row-a-climate-scientist-on-what-flood-weary-australians-can-expect-this-summer-190542">third consecutive La Niña</a> summer. Persistent heavy rainfall, associated with large-scale moisture transport in the atmosphere interacting with a trough, caused the flooding. </p>
<p>A blocking high pressure pattern in the Tasman Sea prevented the weather system from moving to the east. This caused the rain to continue and supported the formation of an east coast low, which brought rainfall to the greater Sydney region in early March.</p>
<p>The rain fell on already soaked surfaces, which worsened these floods and also set up the conditions for subsequent floods in Lismore and other parts of the east coast. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/531592/original/file-20230613-29-u9zbno.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/531592/original/file-20230613-29-u9zbno.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531592/original/file-20230613-29-u9zbno.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531592/original/file-20230613-29-u9zbno.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531592/original/file-20230613-29-u9zbno.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531592/original/file-20230613-29-u9zbno.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531592/original/file-20230613-29-u9zbno.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531592/original/file-20230613-29-u9zbno.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&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 heavy rainfall that led to floods in February and March 2022 was caused by different weather and climate influences coming together.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>These floods occurred not long before the Australian election and led to a renewed focus on climate change action. </p>
<p>While we need to rapidly reduce greenhouse gas emissions to <a href="https://www.ipcc.ch/2022/04/04/ipcc-ar6-wgiii-pressrelease/">limit the damages caused by climate change</a>, the role of climate change in this extreme rain event is unclear. </p>
<h2>Rainfall in a warming world</h2>
<p>There are two necessary ingredients for extreme rainfall to occur – an abundant supply of moisture and ascending air. Heavy rain can occur when moist air rises, cools and condenses. Air can be forced upwards by obstacles such as mountains and by low pressure systems.</p>
<p>As the atmosphere warms it can hold more moisture – about 7% more for every 1°C of warming. This means climate change has increased the moisture-holding capacity of the atmosphere.</p>
<p>But the climate change effect on low pressure systems that cause air to rise varies across the planet. In some places these are becoming more common and intense. In other places they’re occurring less often.</p>
<p>In the prolonged heavy rainfall of February-March 2022, the duration of the weather patterns was a major factor in the flood impacts. It’s unclear how big a role climate change played.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/nd5GSA7OCCk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Flooding at Murwillumbah, NSW, February-March 2022. A short film by Josh Northeast.</span></figcaption>
</figure>
<h2>Short downpours or longer drenching rains?</h2>
<p>Heavy rain events that cause flash flooding and pass in minutes or hours are often limited by how much moisture is available to fall as rain. A warmer atmosphere can hold more moisture, so these short duration rain events are intensified in a warming world. <a href="https://www.science.org/doi/abs/10.1126/science.abn8657">Recent research</a> shows that in Sydney there has been an increase in sub-hourly heavy rain intensity of about 40% over the last 20 years. </p>
<p>For persistent heavy rain that tends to cause river flooding, the limiting factor is more the positioning of weather systems and whether they stall. As a result, the climate change signal in these events tends to be weaker and more variable across the world.</p>
<h2>What can we say after extreme events?</h2>
<p>In the emotionally charged time following extreme events, it is important that commentators – whether they are scientists or journalists, politicians or advocates – make scientifically accurate statements on the role of climate change. </p>
<p>In our paper, we recommend scientists consider different lines of evidence before making statements on the role of climate change in extreme rainfall. These include examining observational trends and relevant peer-reviewed research on the climate of the area where the extreme event occurred.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/530488/original/file-20230607-22-4rftu4.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/530488/original/file-20230607-22-4rftu4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/530488/original/file-20230607-22-4rftu4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/530488/original/file-20230607-22-4rftu4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/530488/original/file-20230607-22-4rftu4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/530488/original/file-20230607-22-4rftu4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/530488/original/file-20230607-22-4rftu4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/530488/original/file-20230607-22-4rftu4.png?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"></a>
<figcaption>
<span class="caption">Different lines of evidence should be considered when thinking about the climate change role in extreme rain events. For the multi-day east Australian heavy rainfall in early 2022, these lines of evidence point in different directions.</span>
<span class="attribution"><span class="source">Author provided. Modified from King et al. (2023)</span></span>
</figcaption>
</figure>
<p>Robust statements on the effects of climate change on extreme events improve the public discourse and are crucial to planning for weather and climate extremes in a warming world.</p>
<p>The impacts of climate change are drastic enough. We don’t need to sensationalise them.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/global-warming-to-bring-record-hot-year-by-2028-probably-our-first-above-1-5-c-limit-205758">Global warming to bring record hot year by 2028 – probably our first above 1.5°C limit</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/206958/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew King receives funding from the National Environmental Science Program. </span></em></p><p class="fine-print"><em><span>Kate R Saunders receives funding from the Australian Research Council Centre of Excellence for Climate Extremes.</span></em></p><p class="fine-print"><em><span>Kimberley Reid receives funding from the Australian Research Council Centre of Excellence for Climate Extremes</span></em></p>Some were quick to point the finger at climate change when floods hit eastern Australia in February and March 2022, in the lead up to the federal election. But it’s not that simple, scientists say.Andrew King, Senior Lecturer in Climate Science, The University of MelbourneKate R Saunders, Lecturer, Monash UniversityKimberley Reid, Postdoctoral Research Fellow in Atmospheric Sciences, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1975352023-01-11T19:09:10Z2023-01-11T19:09:10ZNew report shows alarming changes in the entire global water cycle<figure><img src="https://images.theconversation.com/files/503945/original/file-20230111-14-mokvgf.jpg?ixlib=rb-1.1.0&rect=4%2C0%2C2939%2C1844&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Anjum Naveed/AP</span></span></figcaption></figure><p>In 2022, a third La Niña year brought much rain to Australia and Southeast Asia and dry conditions to the other side of the Pacific. These patterns were expected, but behind these variations there are troubling signs the entire global water cycle is changing.</p>
<p>Our research team watches the global water cycle closely. We analyse observations from more than 40 satellites that continuously monitor the atmosphere and Earth’s surface. We merge those with data from thousands of weather and water monitoring stations on the ground. </p>
<p>For the first time, we’ve drawn on those many terabytes of data to paint a full picture of the water cycle over a year for the entire globe, as well as for individual countries. The findings are contained in a <a href="https://wenfo.org/globalwater/">report</a> released today.</p>
<p>The key conclusion? Earth’s water cycle is clearly changing. Globally, the air is getting hotter and drier, which means droughts and risky fire conditions are developing faster and more frequently.</p>
<figure class="align-center ">
<img alt="A tyre sits on a dry lake bed" src="https://images.theconversation.com/files/503947/original/file-20230111-4958-g2wsq8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503947/original/file-20230111-4958-g2wsq8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503947/original/file-20230111-4958-g2wsq8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503947/original/file-20230111-4958-g2wsq8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503947/original/file-20230111-4958-g2wsq8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503947/original/file-20230111-4958-g2wsq8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503947/original/file-20230111-4958-g2wsq8.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">Earth’s air is getting hotter and drier, which means more flash droughts.</span>
<span class="attribution"><span class="source">CAROLINE BREHMAN/AP</span></span>
</figcaption>
</figure>
<h2>The year in a nutshell</h2>
<p>In 2022, a third consecutive La Niña influenced weather around the world.
Three La Niña years in a row is unusual but <a href="https://theconversation.com/la-nina-3-years-in-a-row-a-climate-scientist-on-what-flood-weary-australians-can-expect-this-summer-190542">not unprecedented</a>.</p>
<p>A La Niña is an oceanic event in which sea surface temperatures are cooler than normal in the central and eastern tropical Pacific and warmer than normal in the western Pacific. The phenomenon strengthens easterly trade winds that bring rain to southeast Asia and Australia. </p>
<p>In 2022, La Niña combined with warm waters in the northern Indian Ocean to bring widespread flooding in a band stretching from Iran to New Zealand, and almost everywhere in between. </p>
<p>The most devastating floods occurred in Pakistan, where about 8 million people were driven out of their homes by massive flooding along the Indus River. Australia also experienced several severe flood events throughout the year – mostly in the east, but <a href="https://earthobservatory.nasa.gov/images/150814/flooding-along-australias-fitzroy-river">also in Western Australia’s Kimberly region</a> at the very end of the year and into 2023.</p>
<p>As is typical for La Niña, the rain was much less plentiful on the other side of the Pacific Ocean. A multi-year drought in the western United States and central South America saw lakes fall to <a href="https://www.nbcnews.com/science/environment/lake-mead-nears-dead-pool-status-water-levels-hit-another-historic-low-rcna34733">historic lows</a>.</p>
<p>Another year of drought also decimated crops and led to a rapidly worsening <a href="https://www.climatecentre.org/9710/ifrc-amid-worst-drought-in-40-years-chance-of-famine-rises-25-per-cent-in-somalia-if-displaced-people-dont-get-help/">humanitarian situation in the Horn of Africa</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/503788/original/file-20230110-20-gmqh9b.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/503788/original/file-20230110-20-gmqh9b.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503788/original/file-20230110-20-gmqh9b.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=346&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503788/original/file-20230110-20-gmqh9b.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=346&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503788/original/file-20230110-20-gmqh9b.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=346&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503788/original/file-20230110-20-gmqh9b.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=435&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503788/original/file-20230110-20-gmqh9b.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=435&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503788/original/file-20230110-20-gmqh9b.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=435&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Major water-related events in 2022.</span>
<span class="attribution"><span class="source">Global Water Monitor 2022 Summary Report</span></span>
</figcaption>
</figure>
<h2>A change in the rains</h2>
<p>Although our data do not suggest a change in average global rainfall, there are troubling trends in several regions. </p>
<p>The monsoon regions from India to Northern Australia are getting wetter. Parts of the Americas and Africa are getting drier, including the western United States, which experienced its <a href="https://www.nature.com/articles/s41558-022-01290-z">23rd year of drought</a> in 2022.</p>
<p>Monthly rainfall total records appear intact. But rainfall over shorter periods is becoming <a href="https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-8/">increasingly intense</a> in many regions.</p>
<p>As our report highlights, intense rainfall events struck communities across the globe in 2022 – from Brazil, Nigeria and South Africa to Afghanistan, India and Pakistan.</p>
<p>The downpours caused flash floods and landslides, killing thousands and leaving many thousands more without a home. Growing population pressures are pushing ever more people into floodplains and onto unstable slopes, making heavy rain and flood events even more damaging than in the past.</p>
<figure class="align-center ">
<img alt="people holding belongings wade through water" src="https://images.theconversation.com/files/503950/original/file-20230111-12-zg3q2d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503950/original/file-20230111-12-zg3q2d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=328&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503950/original/file-20230111-12-zg3q2d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=328&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503950/original/file-20230111-12-zg3q2d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=328&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503950/original/file-20230111-12-zg3q2d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=412&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503950/original/file-20230111-12-zg3q2d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=412&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503950/original/file-20230111-12-zg3q2d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=412&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The downpours caused flash floods and left thousands homeless.</span>
<span class="attribution"><span class="source">Anjum Naveed/AP</span></span>
</figcaption>
</figure>
<h2>A hotter, drier world</h2>
<p>Average global air temperatures are rising. While La Niña years are historically relatively cool, that effect is largely lost in the upward march of global temperatures.</p>
<p>Heatwaves are increasing in severity and duration and this was noticeable in 2022. Apart from being natural disasters in their own right, heatwaves and unseasonally high temperatures also affect the water cycle. </p>
<p>In 2022, intense heatwaves in Europe and China led to so-called “<a href="https://theconversation.com/what-is-a-flash-drought-an-earth-scientist-explains-194141">flash droughts</a>”. These occur when warm, dry air causes the rapid evaporation of water from soils and inland water systems. </p>
<p>In 2022, many rivers in Europe ran dry, <a href="https://www.theguardian.com/world/2022/aug/19/hunger-stones-wrecks-and-bones-europe-drought-brings-past-to-surface">exposing</a> artefacts hidden for centuries.</p>
<p>Air is not only getting warmer but also drier, nearly everywhere. That means people, crops and ecosystems need more water to stay healthy, further increasing pressure on water resources. </p>
<p>Dry air also means forests dry out faster, increasing the severity of bushfires. In 2022, the western US experienced <a href="https://www.bbc.com/news/world-us-canada-60092300">major fires in January</a>, in the middle of Northern Hemisphere winter. </p>
<p>Warmer temperatures also melt snow and ice faster. The Pakistan floods were made worse by a preceding intense heatwave that <a href="https://www.japantimes.co.jp/news/2022/09/05/world/himalayan-glaciers-pakistan-floods/">increased glacier melt</a> in the Himalayas. This raised river flows even before the rains hit.</p>
<p>Climate change is not the only way humanity is changing the water cycle. There has been a steady increase in the volume of lakes worldwide. This is mostly due to individuals and governments constructing and enlarging dams to secure their access water, which changes river flows downstream.</p>
<figure class="align-center ">
<img alt="People look on as water pours down the front of a dam" src="https://images.theconversation.com/files/503954/original/file-20230111-13-y2y0vi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503954/original/file-20230111-13-y2y0vi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=403&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503954/original/file-20230111-13-y2y0vi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=403&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503954/original/file-20230111-13-y2y0vi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=403&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503954/original/file-20230111-13-y2y0vi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=507&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503954/original/file-20230111-13-y2y0vi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=507&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503954/original/file-20230111-13-y2y0vi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=507&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Humans are building more dams as the global water cycle changes.</span>
<span class="attribution"><span class="source">Danny Lawson//AP</span></span>
</figcaption>
</figure>
<h2>Welcome to the future</h2>
<p>La Niña’s influence appears to be waning, and <a href="https://www.abc.net.au/news/2023-01-06/is-el-nino-next-after-la-nina-bom-climate-driver-forecast/101828686">a switch</a> to an El Niño halfway through this year is possible.</p>
<p>Hopefully, that will mean fewer flood disasters in Asia and Oceania and more rain for drought-affected regions in the Americas and East Africa. </p>
<p>Australia, however, may see a return to heatwaves and bushfires. In the longer term, 2023 may mark the start of another multi-year drought.</p>
<p>The seesawing between El Niño and La Niña is a natural phenomenon. But it remains to be seen whether the triple La Niña was a statistical fluke or a sign of <a href="https://theconversation.com/climate-change-will-clearly-disrupt-el-nino-and-la-nina-this-decade-40-years-earlier-than-we-thought-194529">disruption from climate change</a>. </p>
<p>If La Niña or El Niño stays around longer in future, we’re likely to experience deeper droughts and worse floods than seen to date.</p>
<p>Humanity’s success in reducing greenhouse gas emissions will determine the planet’s future several decades from now. Until then, global temperatures will continue to increase. New records will continue to be broken: for heatwaves, cloudbursts, flash droughts, bushfires and ice melt.</p>
<p>There is no way to avoid that. What we can do is heed the warning signs and prepare for a challenging future. </p>
<hr>
<p><em>The 2022 report and the underlying data are publicly available via <a href="https://wenfo.org/globalwater/">www.globalwater.online</a>.</em> </p>
<p><em>The following people collaborated on the 2022 report: Jiawei Hou (Australian National University), Hylke Beck (King Abdullah University of Science and Technology, Saudi-Arabia), Richard de Jeu and Robin van der Schalie (Planet, Netherlands), Wouter Dorigo and Wolfgang Preimesberger (TU Wien, Austria), Pablo Rozas Larraondo (Haizea Analytics, Australia) and Joel Rahman (Flowmatters, Australia).</em></p><img src="https://counter.theconversation.com/content/197535/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Albert Van Dijk receives or has previously received funding from several government-funded agencies, grant schemes and programmes.</span></em></p>Globally, the air is getting hotter and drier, which means flash droughts and risky fire conditions are developing faster and more frequently.Albert Van Dijk, Professor, Water and Landscape Dynamics, Fenner School of Environment & Society, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1968972023-01-10T04:19:04Z2023-01-10T04:19:04ZEngland may be set to flood at the end of winter – here’s why<figure><img src="https://images.theconversation.com/files/503393/original/file-20230106-12-u03vc8.jpg?ixlib=rb-1.1.0&rect=11%2C0%2C3947%2C2635&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">England may flood in February.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/malton-england1127-young-family-being-rescued-1162753714">Steve Allen/Shutterstock</a></span></figcaption></figure><p>Within the space of a week in February 2022, England and Wales were affected by <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">three severe storms</a> (Dudley, Eunice and Franklin). Persistent heavy rain led to the flooding of around 400 properties and severe flood warnings were issued for several major rivers, including the River Severn. Now, the UK Met Office is <a href="https://www.theguardian.com/environment/2022/nov/07/met-office-predicts-severe-flooding-across-england-in-february">predicting</a> that England is again set to experience severe flooding in February 2023 – a prediction the forecasters attribute to a global weather phenomenon called La Niña.</p>
<p>El Niño and La Niña are the two separate phases 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> (ENSO). This is the name given to the phenomenon of irregular <a href="https://earthobservatory.nasa.gov/global-maps/MYD28M#:%7E:text=Sea%20surface%20temperatures%20have%20a,2%20to%203%20degrees%20Celsius.">annual variations</a> in sea surface temperatures (by as much as 3°C), air pressure and rainfall across the Pacific Ocean. A La Niña event is characterised by significantly lower sea surface temperatures in areas of the Pacific.</p>
<p>Further research is needed into the effects of global weather systems on winter weather in the northern hemisphere. But wide variations in Pacific sea surface temperatures can set off a chain reaction of extreme weather across the world. La Niña can destabilise atmospheric pressures in the Atlantic Ocean and lead to heavy rainfall in western Europe and the southern US. </p>
<p>But other factors may also contribute to the Met Office’s flood prediction. These include the long-term impacts of climate change and urban development in areas prone to flooding.</p>
<h2>Global weather patterns</h2>
<p>During a La Niña event, cooler water decreases the temperature of the air immediately above the sea and <a href="https://sciencing.com/temperature-affect-barometric-pressure-5013070.html">causes it to sink</a>. This creates large areas of low pressure in the Pacific Ocean which generally lead to increased rainfall in the surrounding region. </p>
<p>However, these extensive low pressure areas force pools of high pressure northwards towards Europe. This manifests initially as drier and colder weather conditions in the UK as the seasonal rains brought by low pressure rain-bearing depressions from the Atlantic are blocked by persistent high pressure conditions. </p>
<p>The first half of December 2022, for instance, marked the coldest start to a UK winter since 2010. The <a href="https://blog.metoffice.gov.uk/2022/12/30/cold-december-concludes-warmest-year-on-record-for-uk/">monthly temperature average</a> was 1.3°C lower than the December average between 1991 and 2020.</p>
<p>Powerful storms are instead likely later in the season. As the high pressure recedes and La Niña shifts jet stream patterns northwards, the usual pattern of westerly depressions is allowed to resume. Cooler-than-usual Pacific ocean temperatures in recent months have prompted scientists to predict that there is a <a href="https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml">76% chance</a> that La Niña will persist until the end of February 2023. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/tIJBtdagj2E?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">La Niña explained.</span></figcaption>
</figure>
<h2>Favourable conditions</h2>
<p>La Niña conditions may result in heavy late winter rainfall. But the UK is experiencing increasingly extreme weather conditions all year round. The long-term impacts of this could create conditions favourable for flooding. </p>
<p>Southern England faces long periods of drought each summer. Last year, the Anglian, Thames and Wessex water supply regions all recorded their <a href="https://www.ceh.ac.uk/news-and-media/blogs/why-we-are-still-drought-despite-recent-rain#:%7E:text=Summer%202022%20(June%2DAugust),shown%20in%20the%20plot%20below">fifth-driest summer</a> since 1836. </p>
<p>This has increased the risk of flooding as ground surfaces become less permeable to rainfall infiltration. Despite recent low intensity rainfall, the risk of flooding in the areas affected by drought may still be high. Cold temperatures, like those experienced in December, may also return later this winter and further reduce the ground’s capacity to absorb water. </p>
<p>Underground, chalk aquifers dominate central and southern parts of England. These aquifers, like sponges, have a finite capacity to accept and transmit fast flowing water. Heavy rainfall may therefore be forced over land where it can flow rapidly. <a href="https://nora.nerc.ac.uk/id/eprint/14085/1/1_Mansour_HydrologicalProcesses_Submitted.pdf">Research</a> indicates that above ground, water can flow at up to 100 times the speed of its flow through aquifer rock. </p>
<p>This water flows into sewers and rivers and can overwhelm their natural or operational capacities. Rivers then break their banks and cause flooding. </p>
<figure class="align-center ">
<img alt="A fence submerged in a flooded river." src="https://images.theconversation.com/files/503394/original/file-20230106-18-qjqw2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503394/original/file-20230106-18-qjqw2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503394/original/file-20230106-18-qjqw2y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503394/original/file-20230106-18-qjqw2y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503394/original/file-20230106-18-qjqw2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503394/original/file-20230106-18-qjqw2y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503394/original/file-20230106-18-qjqw2y.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">England’s environmental conditions are favourable for flooding.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/submerged-wooden-fence-on-river-heavy-1656383137">Ceri Breeze/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Humans offer little help</h2>
<p>Several other factors also increase the likelihood that heavy rainfall this winter will cause parts of England to flood. </p>
<p>Over half of England’s major urban flooding events in early 2022 were driven by <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/292928/geho0609bqds-e-e.pdf">underground blockages</a> of dated sewerage systems. Their insufficient capacity caused them to fast become overwhelmed by debris floating in floodwater. </p>
<p>Some UK cities, such as Hull, Bristol and parts of London have also been developed on river floodplains. Land on floodplains is often cheap, flat and, as such, easy to build on. But this makes these cities prone to flooding. Flood risk mapping has revealed that <a href="https://www.gov.uk/check-flooding">19% of Gloucester</a>, a city in the southwest of England, is at risk of regular flooding.</p>
<p>Climate models are now predicting climatic changes and global weather patterns with <a href="https://climate.nasa.gov/news/2943/study-confirms-climate-models-are-getting-future-warming-projections-right/">increased accuracy</a>. But mitigating their environmental impacts often proves challenging.</p>
<p>England requires extensive infrastructure changes to reduce the threat of flooding. One option is to prohibit the construction of housing on floodplains. However, urban planning approaches such as this involve overcoming legal and regulatory barriers. </p>
<p>Another approach would be to improve sewerage capacity to account for population growth and its associated pressure on water use. Yet the completion of large infrastructural measures takes time. Various different stakeholders, including the public, must be consulted, while competing designs have to be assessed by experts and their impact modelled. It took <a href="https://www.gov.uk/guidance/the-thames-barrier">15 years</a>, for example, for London’s Thames Barrier to be completed following its initial conception. </p>
<figure class="align-center ">
<img alt="The Thames Barrier, stretching across the River Thames in London." src="https://images.theconversation.com/files/503395/original/file-20230106-10513-wqbkru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503395/original/file-20230106-10513-wqbkru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503395/original/file-20230106-10513-wqbkru.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503395/original/file-20230106-10513-wqbkru.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503395/original/file-20230106-10513-wqbkru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503395/original/file-20230106-10513-wqbkru.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503395/original/file-20230106-10513-wqbkru.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">London’s Thames Barrier has been in operation since 1984.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/london-aug-4-thames-barrier-tidal-149443685">BBA Photography/Shutterstock</a></span>
</figcaption>
</figure>
<p>Flood management measures also require the political will for implementation. This <a href="https://www.sciencedirect.com/science/article/pii/S0016718515000834">has not always been forthcoming</a>, particularly when flood management is considered unduly expensive or environmentally damaging. </p>
<p>For example, river dredging was long considered an <a href="https://www.tandfonline.com/doi/full/10.1080/09640568.2016.1157458?scroll=top&needAccess=true&role=tab">unsuitable flood mitigation technique</a> for the Somerset Levels in southwest England. But winter flooding in 2013-14 led to its immediate and <a href="https://www.bbc.co.uk/news/uk-england-somerset-29851345">ultimately successful implementation</a>.</p>
<p>In the absence of these changes, the UK should brace for a fresh wave of flooding at the end of winter. Driven by a La Niña event, but exacerbated by urban development in areas prone to flooding and the impacts of climate change, the effects could be severe. </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>
<br><em><a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeTop">Get a weekly roundup in your inbox instead.</a> Every Wednesday, The Conversation’s environment editor writes Imagine, a short email that goes a little deeper into just one climate issue. <a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeBottom">Join the 10,000+ readers who’ve subscribed so far.</a></em></p>
<hr><img src="https://counter.theconversation.com/content/196897/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Paul 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 Met Office has predicted that England is to be affected by flooding this February.Jonathan Paul, Lecturer (Assistant Professor) in Earth Science, Royal Holloway University of LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1951362022-11-23T00:27:51Z2022-11-23T00:27:51ZState of the climate: what Australians need to know about major new report<figure><img src="https://images.theconversation.com/files/496769/original/file-20221122-19-y5r6vm.jpg?ixlib=rb-1.1.0&rect=6%2C0%2C4162%2C2906&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">David Crosling/AAP</span></span></figcaption></figure><p>The latest State of the Climate report is <a href="https://www.csiro.au/en/research/environmental-impacts/climate-change/state-of-the-climate">out</a>, and there’s not much good news for Australians.</p>
<p>Our climate has warmed by an average 1.47°C since national records began, bringing the continent close to the 1.5°C limit the Paris Agreement hoped would never be breached. When global average warming reaches this milestone, some of Earth’s natural systems are predicted to suffer <a href="https://www.ipcc.ch/2021/08/09/ar6-wg1-20210809-pr/">catastrophic damage</a>.</p>
<p>The report, released today, paints a concerning picture of ongoing and worsening climate change. In Australia, associated impacts such as extreme heat, bushfires, drought, heavy rainfall, and coastal inundation threaten our people and our environment. </p>
<p>The report is a comprehensive biennial snapshot of the latest trends in climate, with a focus on Australia. It’s compiled by the Bureau of Meteorology and CSIRO, drawing on the latest national and international climate research.</p>
<p>It synthesises the latest science about Australia’s climate and builds on the previous 2020 report by including, for example, information from the most recent assessment report by the Intergovernmental Panel on Climate Change.</p>
<p>And the take home message? Climate change continues unabated. The world is warming, sea levels are rising, ice is melting, fire weather is worsening, flooding rains are becoming more frequent – and the list goes on. </p>
<p>What follows is a summary of major findings in three key categories – and an explanation of what it all means.</p>
<figure class="align-center ">
<img alt="building with red sun" src="https://images.theconversation.com/files/496773/original/file-20221122-18-hnedl7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/496773/original/file-20221122-18-hnedl7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/496773/original/file-20221122-18-hnedl7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/496773/original/file-20221122-18-hnedl7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/496773/original/file-20221122-18-hnedl7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/496773/original/file-20221122-18-hnedl7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/496773/original/file-20221122-18-hnedl7.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 report synthesises the latest science about Australia’s climate.</span>
<span class="attribution"><span class="source">Steven Saphore/AAP</span></span>
</figcaption>
</figure>
<h2>1. Warming, heat extremes and bushfire</h2>
<p>The 2020 report said Australia’s climate has warmed on average by 1.44°C since national records began in 1910. That warming has now increased to 1.47°C. This mirrors trends across the world’s land areas, and brings with it more frequent extreme heat events.</p>
<p>The year 2019 was Australia’s warmest on record. The eight years from 2013 to 2020 are all among the ten warmest ever measured. Warming is happening both by day and by night, and across all months.</p>
<p>Since the 1950s, extreme fire weather has increased and the fire season has lengthened across much of the country. It’s resulted in bigger and more frequent fires, especially in southern Australia. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-planting-tomatoes-shows-us-about-climate-change-193830">What planting tomatoes shows us about climate change</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="woman floats in water at beach" src="https://images.theconversation.com/files/496770/original/file-20221122-26-fi2dk3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/496770/original/file-20221122-26-fi2dk3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=367&fit=crop&dpr=1 600w, https://images.theconversation.com/files/496770/original/file-20221122-26-fi2dk3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=367&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/496770/original/file-20221122-26-fi2dk3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=367&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/496770/original/file-20221122-26-fi2dk3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=462&fit=crop&dpr=1 754w, https://images.theconversation.com/files/496770/original/file-20221122-26-fi2dk3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=462&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/496770/original/file-20221122-26-fi2dk3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=462&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The warming climate brings more frequent extreme heat.</span>
<span class="attribution"><span class="source">Kelly Barnes/AAP</span></span>
</figcaption>
</figure>
<h2>2. Rain, floods and snow</h2>
<p>In Australia’s southwest, May to July rainfall has fallen by 19% since 1970. In the southeast of Australia, April to October rainfall has fallen by 10% since the late 1990s. </p>
<p>This will come as somewhat of a surprise given the relatively wet conditions across eastern Australia over the past few years. But don’t confuse longer term trends with year-to-year variability.</p>
<p>Lower rainfall has led to reduced streamflow; some 60% of water gauges around Australia show a declining trend.</p>
<p>At the same time, heavy rainfall events are becoming more intense – a fact not lost on flood-stricken residents in Australia’s eastern states in recent months. The intensity of extreme rainfall events lasting an hour has increased by about 10% or more in some regions in recent decades. This often brings flash flooding, especially in urban environments. The costs to society are enormous.</p>
<p>Warm air can hold more water vapour than cooler air. That’s why global warming makes heavy rainfall events more likely, even in places where average rainfall is expected to decline.</p>
<p>Also since the 1950s, snow depth and cover, and the number of snow days, have decreased in alpine regions. The largest declines are happening in spring and at lower altitudes.</p>
<p>Extremely cold days and nights are generally becoming less frequent across the continent. And while parts of southeast and southwest Australia have recently experienced very cold nights, that’s because cool seasons have become drier and winter nights clearer there, leading to more overnight heat loss. </p>
<p>Any camper will tell you how chilly it can get on a clear starry night, without the warm blanket of cloud cover.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/as-new-south-wales-reels-many-are-asking-why-its-flooding-in-places-where-its-never-flooded-before-190912">As New South Wales reels, many are asking why it's flooding in places where it's never flooded before</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="man photographs flooded road" src="https://images.theconversation.com/files/496771/original/file-20221122-17-rmldox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/496771/original/file-20221122-17-rmldox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/496771/original/file-20221122-17-rmldox.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/496771/original/file-20221122-17-rmldox.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/496771/original/file-20221122-17-rmldox.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/496771/original/file-20221122-17-rmldox.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/496771/original/file-20221122-17-rmldox.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">Heavy rainfall events are becoming more intense.</span>
<span class="attribution"><span class="source">Jason O'Brien/AAP</span></span>
</figcaption>
</figure>
<h2>3. Oceans and sea levels</h2>
<p>Sea surface temperatures around the continent have increased by an average 1.05°C since 1900. The greatest ocean warming since 1970 has occurred off southeast Australia and Tasmania. In the Tasman Sea, the warming rate is now twice the global average. </p>
<p>Ongoing ocean warming has also contributed to longer and more frequent marine heatwaves. Marine heatwaves are particularly damaging to ecosystems, including the Great Barrier Reef, which is at perilous risk of ruin if nothing is done to address surging greenhouse gas emissions.</p>
<p>Oceans around Australia have also become more acidic, and this damage is accelerating. The greatest change is occurring in temperate and cooler waters to the south.</p>
<p>Sea levels are rising globally and around Australia. This is driven by both ocean warming and melting ice. Ice loss from Greenland, Antarctica and glaciers is increasing, and only set to get worse. </p>
<p>Around Australia, the largest sea level rise has been observed to the north and southeast of the continent. This is increasing the risk of inundation and damage to coastal infrastructure and communities.</p>
<figure class="align-center ">
<img alt="damaged coastline including pool fallen onto beach" src="https://images.theconversation.com/files/496772/original/file-20221122-22-u13cm4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/496772/original/file-20221122-22-u13cm4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=389&fit=crop&dpr=1 600w, https://images.theconversation.com/files/496772/original/file-20221122-22-u13cm4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=389&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/496772/original/file-20221122-22-u13cm4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=389&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/496772/original/file-20221122-22-u13cm4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=489&fit=crop&dpr=1 754w, https://images.theconversation.com/files/496772/original/file-20221122-22-u13cm4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=489&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/496772/original/file-20221122-22-u13cm4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=489&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rising sea levels increase the risk of damage to coastal infrastructure.</span>
<span class="attribution"><span class="source">David Moir/AAP</span></span>
</figcaption>
</figure>
<h2>What’s causing this?</h2>
<p>All this is happening because concentrations of greenhouse gases in Earth’s atmosphere continue to rise. The principal driver of these gases is human burning of fossil fuels. These long-lived gases form a “blanket” in the atmosphere that makes it harder for Earth to radiate the Sun’s heat back into space. And so, the planet warms, with very costly impacts to society. </p>
<p>The report confirmed carbon dioxide (CO₂) has been accumulating in the atmosphere at an increasing rate in recent decades. Worryingly, over the past two years, levels of methane and nitrous oxide have also grown very rapidly.</p>
<h2>What comes next?</h2>
<p>None of these problems are going away. Australia’s weather and climate will continue to change in coming decades. </p>
<p>As the report states, these climate changes are increasingly affecting the lives and livelihoods of all Australians. It goes on:</p>
<blockquote>
<p>Australia needs to plan for, and adapt to, the changing nature of climate risk now and in the decades ahead. The severity of impacts on Australians and our environment will depend on the speed at which global greenhouse gas emissions can be reduced.</p>
</blockquote>
<p>This point is particularly confronting, given the <a href="https://theconversation.com/cop27-flinched-on-phasing-out-all-fossil-fuels-whats-next-for-the-fight-to-keep-them-in-the-ground-194941">abject failure</a> of the recent COP27 climate talks in Egypt to build on commitments from Glasgow only a year earlier to phase out fossil fuels. </p>
<p>It’s no surprise, then, that the insurance sector is <a href="https://www.dailymail.co.uk/news/article-11454605/NSW-floods-Insurers-wont-renew-flood-cover-towns-Forbes-Molong-Cabonne-Council.html">getting nervous </a> about issuing new policies to people living at the front-line of climate extremes.</p>
<p>While the urgency for action has never been more pressing, we still hold the future in our hands - the choices we make today will decide our future for generations to come. Every 0.1°C of warming we can avoid will make a big difference.</p>
<p>But it’s not all bad news. Re-engineering our energy and transport systems to be carbon neutral will create a whole new economy and jobs growth - with the added bonus of a safer climate future. </p>
<p>Do nothing, and these State of the Climate reports will continue to make for grim reading. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/cop27-flinched-on-phasing-out-all-fossil-fuels-whats-next-for-the-fight-to-keep-them-in-the-ground-194941">COP27 flinched on phasing out 'all fossil fuels'. What's next for the fight to keep them in the ground?</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/195136/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew England receives funding from the Australian Research Council.</span></em></p>The report synthesises the latest science about Australia’s climate – and paints a worrying picture.Matthew England, Scientia Professor and Deputy Director of the ARC Australian Centre for Excellence in Antarctic Science (ACEAS), UNSW 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>
<hr>
<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>
</strong>
</em>
</p>
<hr>
<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>
<figure>
<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>
</figure>
<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>
<hr>
<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>
</strong>
</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/1925002022-10-17T19:04:31Z2022-10-17T19:04:31Z‘A cunning plan’: how La Niña unleashes squadrons of storm clouds to wreak havoc in your local area<p>Heavy rain and floods have once again hit towns and suburbs across eastern Australia. Some areas have been devastated, while others have been spared the worst. While climate drivers like La Niña make extreme wet weather more likely, what explains when and where the storm clouds deliver a deluge? </p>
<p>Extreme weather, such as the heavy rainfall battering eastern Australia, is like military conflict. In war, the enemy’s behaviour depends on the decisions of many actors: from generals and lieutenants down to individual soldiers. Similarly, heavy rainfall is the culmination of diverse physical processes, from the planetary scale down to the microscopic.</p>
<p>A strategic defence requires anticipating how the enemy will behave across this hierarchy. To continue with the military analogy, this is how we can explain the weather offensive of the past week.</p>
<h2>The generals command the offensive</h2>
<p>Processes on a yearly or planetary scale, such as <a href="http://www.bom.gov.au/climate/about/?bookmark=enso">La Niña</a> and the <a href="http://www.bom.gov.au/climate/sam/">Southern Annular Mode</a>, are like generals. Over the <a href="http://www.bom.gov.au/climate/enso/wrap-up/archive/20220816.archive.shtml">preceding years and months</a>, these two generals hatched a plot of <a href="http://www.bom.gov.au/climate/enso/">warmer-than-usual waters and more-easterly-than-normal winds</a> around northern and eastern Australia. </p>
<p>La Niña promotes easterly winds by strengthening the Pacific equatorial oceanic and atmospheric circulations. The Southern Annular Mode moves the belt of high- and low-pressure systems you see on the evening news further south, reducing their obstruction of the easterly winds. </p>
<p>Stronger easterlies help humid air over the Pacific advance into the eastern states and feed storm clouds: a cunning plan.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1579738458477600768"}"></div></p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/la-nina-3-years-in-a-row-a-climate-scientist-on-what-flood-weary-australians-can-expect-this-summer-190542">La Niña, 3 years in a row: a climate scientist on what flood-weary Australians can expect this summer</a>
</strong>
</em>
</p>
<hr>
<h2>3 lieutenants in action during floods</h2>
<p>Daily and state-scale processes, such as the pressure patterns mentioned above, are like lieutenants. These lieutenants decide the particular day, and states, to attack. At least three lieutenants have been in action during the current flooding. </p>
<p>The first was a <a href="http://www.bom.gov.au/cgi-bin/charts/charts.view.pl?idcode=IDX0102&file=IDX0102.202210130000.gif">high south-west of New Zealand</a>. Air wants to move from high to low pressure but is confounded by Earth’s rotation. Southern hemispheric winds thus travel anticlockwise around highs and clockwise around lows. </p>
<p>The New Zealand high reinforced the general’s stronger easterly winds, directing humid air toward Victoria and New South Wales. </p>
<p>The second lieutenant was an <a href="https://apps.ecmwf.int/webapps/opencharts/products/medium-mslp-wind200?base_time=202210120000&player_dimension=base_time&projection=opencharts_australasia&valid_time=202210130300">undulation in the upper-level winds over Victoria</a>. Through <a href="https://doi.org/10.1175/1520-0434(1990)005%3C0346:AEMFEO%3E2.0.CO;2">complex physics</a>, this undulation promoted upward motion over the south-eastern states, supporting the development of storm clouds.</p>
<p>The third lieutenant was a <a href="https://www.youtube.com/watch?v=QveDO4AO9WQ&list=PLbKuJrA7Vp7m3AC5a0crKS0bH0a5MzOD6&index=5&ab_channel=BureauofMeteorology&t=01m44s">low in the Great Australian Bight</a>. This low dragged cold Antarctic air clockwise around itself, forming a <a href="https://www.youtube.com/watch?v=OFeN5nMqT7M&ab_channel=BureauofMeteorology">cold front</a>. This cold front triggered the storm clouds as it advanced through Victoria.</p>
<p>These three lieutenants, supported by the strategy of their generals, together conspired to inflict the heavy rainfall on October 13 in the south-eastern states. Tactically devious. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1578381259532914689"}"></div></p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/floods-in-victoria-are-uncommon-heres-why-theyre-happening-now-and-how-they-compare-to-the-past-192391">Floods in Victoria are uncommon. Here's why they're happening now – and how they compare to the past</a>
</strong>
</em>
</p>
<hr>
<h2>Soldiers attack each suburb and town</h2>
<p>Hourly and suburb-scale processes, such as storm clouds, are like the individual soldiers: they decide the particular suburb to attack. A storm cloud features an intense updraft <a href="https://doi.org/10.1029/2019JD031774">usually about 2km wide</a>. </p>
<p>These updrafts are largely powered by the condensation of water vapour onto dust particles – a microscopic process. Witnessing a growing storm cloud is like watching an explosion, except the energy source is condensation, not combustion.</p>
<p>A soldier’s behaviour typically reflects the designs of their lieutenants, but they are <a href="https://deep-convection.org/2021/03/02/episode-3-brian-mapes/">not robots</a>. In a firefight, they make their own decisions and can <a href="https://www.nssl.noaa.gov/education/svrwx101/thunderstorms/types/">organise of their own volition</a>. </p>
<p>Soldiers may march single file through a city, successively attacking the same building as they pass. Or they may march many abreast, attacking more buildings but with reduced firepower. Squadrons of <a href="https://journals.ametsoc.org/view/journals/mwre/149/10/MWR-D-21-0007.1.xml">storm clouds make analogous choices</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/on-our-wettest-days-stormclouds-can-dump-30-trillion-litres-of-water-across-australia-191949">On our wettest days, stormclouds can dump 30 trillion litres of water across Australia</a>
</strong>
</em>
</p>
<hr>
<h2>So how can we predict these events?</h2>
<p>Because the enemy organises across large, medium and small scales, so must we.
To help with this, the Australia Bureau of Meteorology uses a computer simulation called the <a href="https://www.metoffice.gov.uk/research/approach/modelling-systems/unified-model">Unified Model</a>. It’s akin to the <a href="https://www.theverge.com/2015/10/2/9443747/microsoft-intel-havok-acquisition">physics engines</a> in computer games such as Halo. </p>
<p>The simulation is “unified” because it uses the same basic infrastructure to predict the atmosphere’s behaviour at all scales, from generals down to soldiers. </p>
<p>Using the Unified Model we can predict lietenants’ behaviour – the high- and low-pressure patterns – <a href="http://www.bom.gov.au/australia/charts/bulletins/opsbull_G3GE3_external_v3.pdf">extremely well five to seven days out</a>. It took nearly a century of global scientific effort to build this capability.</p>
<p>Anticipating the schemes of generals – processes such as La Niña – is <a href="http://www.bom.gov.au/climate/outlooks/#/rainfall/skill/low/seasonal/1">much harder</a>. The bureau generates La Niña predictions by <a href="http://www.bom.gov.au/australia/charts/bulletins/apob120_external.pdf">running the Unified Model many times</a> and counting how often La Niña persists and how often it decays to estimate its most likely behaviour. Current simulations <a href="http://www.bom.gov.au/climate/enso/">suggest</a> La Niña will likely decline over spring and conclude early in 2023.</p>
<p>It is similarly difficult to predict the behaviour of individual soldiers – the individual storm clouds. Eventually, we hope to be able at least to predict how these clouds organise – whether they will march single file or abreast. </p>
<p>The bureau pursues this goal by running complex Unified Model simulations, which explicitly simulate the movement of individual storm clouds over each capital city. These <a href="https://journals.ametsoc.org/view/journals/wefo/37/7/WAF-D-21-0183.1.xml">complex simulations are run inside a simpler, global Unified Model simulation</a> – a bit like the film Inception (a dream within a dream).</p>
<p>It will take decades, if not centuries, before we can seamlessly anticipate the behaviour of the generals and soldiers of the weather as well as we do for the lieutenants. Developing this capability requires sustained support for diverse scientists across many specialities. </p>
<p>While the threats are significant, we now have a deep grasp of the behaviour of lieutenants and are making promising progress with generals and soldiers. Coupled with the success of the unified approach, there are grounds for optimism.</p><img src="https://counter.theconversation.com/content/192500/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ewan Short 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>Processes like La Niña set the scene for the sort of extreme weather that has hit eastern Australia. But what decides which towns and suburbs are hit hardest, and which ones are spared?Ewan Short, PhD Candidate, School of Geography, Earth and Atmospheric Sciences, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1889702022-08-18T20:06:05Z2022-08-18T20:06:05ZNo, not again! A third straight La Niña is likely – here’s how you and your family can prepare<p>Hearts sank along the Australian east coast this week when the Bureau of Meteorology <a href="http://www.bom.gov.au/climate/enso/">announced</a> a third consecutive La Niña was likely this year. La Niña weather events typically deliver above-average rainfall in spring and summer. </p>
<p>But the last two La Niñas mean our catchments are already full. Dams are at capacity, soils are saturated and rivers are high. In some cases, there’s nowhere for the rains to go except over land. </p>
<p>Over the past 18 months, many communities have been hit by floods – some <a href="https://9now.nine.com.au/a-current-affair/warragamba-dam-sydney-floods-raise-walls/c2c7f26c-8fce-43fc-a830-e7dd7a378c0b">more than once</a>. For these residents, the prospect of a third La Niña will be extremely concerning. And some people who’ve never experienced floods may now be at risk.</p>
<p>Our current research project is examining the experiences of flood-hit communities in New South Wales and Queensland – and our interviews have already yielded useful insights. So let’s take a look at what we should be thinking about now as another wet summer looms.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1559407665104621568"}"></div></p>
<h2>Water isn’t always fun</h2>
<p><a href="https://www.canstar.com.au/home-insurance/natural-disasters-australia/">Floods</a> are among the deadliest natural hazards in Australia. Yet in Australian culture, water often equates to fun. From a young age we’re taught to swim, enjoy and “master” the dangers that water poses. </p>
<p>So during floods we often see risky behaviours such as driving and playing in dangerous water.</p>
<p>Recent floods, however, brought home the reality of the threat. Few could forget images of frightened families being <a href="https://www.9news.com.au/national/nsw-flood-update-chopper-rescue-woodburn/14ecbdf2-e8d2-461b-aece-95202e234fbf">winched</a> off roofs by helicopter, water rushing from spilling dams and everyday people <a href="https://www.abc.net.au/news/2022-03-01/lismore-floods-how-two-blokes-in-a-tinnie-saved-25-lives/100869798">rescuing</a> their neighbours.</p>
<p>The NSW government on Wednesday released an <a href="https://www.nsw.gov.au/nsw-government/projects-and-initiatives/floodinquiry">independent report</a> into this year’s floods. It examined flooding from February to April and again in July – mostly around the Northern Rivers, Sydney’s Hawkesbury-Nepean and the central to north coasts.</p>
<p>The report contained troubling statistics, including:</p>
<ul>
<li>nine people tragically died</li>
<li>7,700 people sought emergency accommodation </li>
<li>14,600 homes were damaged</li>
<li>5,300 homes were left uninhabitable.</li>
</ul>
<p>Releasing the report, NSW Premier Dominic Perrottet said <a href="https://www.smh.com.au/environment/climate-change/up-to-40-000-residents-risk-flood-evacuation-in-sydney-s-west-by-2040-perrottet-20220817-p5baj8.html">up to 40,000</a> Western Sydney residents risked flood evacuation by 2040, if flood conditions similar to those in July were repeated and no mitigation action was taken.</p>
<p>The inquiry revealed a central theme: the need for a renewed and stronger emphasis on sustained disaster preparedness. Otherwise, as the report noted, the emergency response becomes harder:</p>
<blockquote>
<p>Preparedness is discussed in relation to emergency management and our natural and built environment. But an important component of preparedness is at a personal or family level. Failure to prepare at this level makes preparations at other levels more difficult and expensive. </p>
</blockquote>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/whats-causing-sydneys-monster-flood-crisis-and-3-ways-to-stop-it-from-happening-again-186285">What's causing Sydney's monster flood crisis – and 3 ways to stop it from happening again</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="police van stuck in flood waters" src="https://images.theconversation.com/files/479802/original/file-20220818-230-a5008y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479802/original/file-20220818-230-a5008y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479802/original/file-20220818-230-a5008y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479802/original/file-20220818-230-a5008y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479802/original/file-20220818-230-a5008y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479802/original/file-20220818-230-a5008y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479802/original/file-20220818-230-a5008y.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">Failing to prepare for floods can make the emergency response harder.</span>
<span class="attribution"><span class="source">Jason O'Brien/AAP</span></span>
</figcaption>
</figure>
<h2>‘Don’t worry. Your house won’t get wet’</h2>
<p>Our <a href="https://lighthouse.mq.edu.au/media-releases/flooded-in-2022-share-your-experience-to-improve-flood-safety">current research</a> is examining the experiences of those affected by this year’s floods to gather insights on preparedness and response. Participants can take part in an interview, a survey or both. </p>
<p>Our interviews are already providing useful insights. They include the possibility that prior experience of flood, and the well-meaning reassurances of others, can hinder preparations. As one respondent said:</p>
<blockquote>
<p>the house, having been built on a mound, has never been flooded and that’s why my neighbour said, ‘Don’t worry. Your house won’t get wet. It’s never got wet in 70 years’. But this was unprecedented.</p>
</blockquote>
<p>With another wet summer likely, interviewees are starting to see major flooding as a “new normal” rather than a once-in-a-lifetime experience. This is causing them to question the future of their communities. As another respondent told us:</p>
<blockquote>
<p>that’s the part that I’m struggling with now is that it feels like it’s unviable to live here because there’s no security, and when you take away people’s security, your life tends to unravel.</p>
</blockquote>
<p>We hope our research will influence policy and practice on flood preparation, community engagement and risk messaging, and shed light on more permanent changes required.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/i-simply-havent-got-it-in-me-to-do-it-again-imagining-a-new-heart-for-flood-stricken-lismore-178982">'I simply haven’t got it in me to do it again': imagining a new heart for flood-stricken Lismore</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="family walks through floodwaters, including girl holding pet carrier" src="https://images.theconversation.com/files/479803/original/file-20220818-25-grfwqf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479803/original/file-20220818-25-grfwqf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479803/original/file-20220818-25-grfwqf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479803/original/file-20220818-25-grfwqf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479803/original/file-20220818-25-grfwqf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479803/original/file-20220818-25-grfwqf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479803/original/file-20220818-25-grfwqf.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 authors hope their work will influence policy and practice on flood preparation.</span>
<span class="attribution"><span class="source">Tracey Nearmy/AAP</span></span>
</figcaption>
</figure>
<h2>Be prepared</h2>
<p>So what should you do if flooding is forecast and you need to evacuate? Here’s what experts recommend:</p>
<ul>
<li><p>identify the safest route to your nearest safe location and leave well before roads flood</p></li>
<li><p>move vehicles, valuables, outdoor equipment, garbage and poisons to higher locations</p></li>
<li><p>enact safety plans for pets and other animals</p></li>
<li><p>take medications and identification with you</p></li>
<li><p>tell friends, family and neighbours of your plans</p></li>
<li><p>know where to go for information. Monitor alerts and stay aware of changing situations</p></li>
<li><p>keep your mobile phone charged and have at least half a tank of fuel in your vehicle</p></li>
<li><p>turn off electricity, gas, and water at the mains before you leave. </p></li>
</ul>
<p>Of course, flood preparation should not be left until the last minute. Now is a good time to think about what might happen in the months ahead. Things you can do now include:</p>
<ul>
<li><p>clean up outside and inside, move or secure items that could float or create a hazard</p></li>
<li><p>move valued possession to higher places in your home</p></li>
<li><p>pack an emergency bag and keep it at the ready</p></li>
<li><p>consider which friends or family you might stay with if needed.</p></li>
</ul>
<p>For further advice, head to the website of your state’s emergency service agencies.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/4aIy0TU-Mco?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Thinking long-term</h2>
<p>Climate change <a href="https://www.climatechange.environment.nsw.gov.au/climate-change-will-exacerbate-natural-disasters-including-flooding">will exacerbate</a> floods and other natural hazards. Communities must be supported to prepare as best they can. </p>
<p>More permanent measures are also needed, such as land buybacks to move people out of flood-prone areas. And importantly, planning systems must ensure we don’t keep building on floodplains. </p>
<p>Our approach to disaster readiness will continue to change. Already, experts are providing advice on matters such as <a href="https://theconversation.com/its-hard-to-breathe-and-you-cant-think-clearly-if-you-defend-your-home-against-a-bushfire-be-mentally-prepared-127019">emotional preparedness</a> and <a href="https://www.naturalhazards.com.au/research/research-projects/community-led-recovery-evidence-dimensions-and-supports-community">recovery</a> in the aftermath. </p>
<p>One thing is clear: in the face of the increasing disaster threat, temporary and seasonal preparations are no longer enough. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/one-of-the-most-extreme-disasters-in-colonial-australian-history-climate-scientists-on-the-floods-and-our-future-risk-178153">'One of the most extreme disasters in colonial Australian history': climate scientists on the floods and our future risk</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/188970/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mel Taylor receives funding from Natural Hazards Research Australia </span></em></p><p class="fine-print"><em><span>Katharine Haynes is the NSW, ACT and SA node research manager for Natural Hazards Research Australia</span></em></p>Catchments are full. Dams are at capacity, soils are saturated and rivers are high. In some cases, there’s nowhere for the rains to go except over land.Mel Taylor, Associate Professor, Macquarie UniversityKatharine Haynes, Honorary Senior Research Fellow, University of WollongongLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1887652022-08-16T15:37:25Z2022-08-16T15:37:25ZDrought: five ways to stop heavy rains washing away parched soil<figure><img src="https://images.theconversation.com/files/479391/original/file-20220816-18-kmctp8.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3264%2C1836&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/mud-flowing-water-reach-pond-swamp-749912869">Sup10mah/Shutterstock</a></span></figcaption></figure><p>When William Blake described England’s “green and pleasant land” in his poem Jerusalem, he was actually writing during a prolonged drought. Two centuries later, much of Europe is withering under successive heatwaves amid one of the most extreme droughts ever recorded. </p>
<p>The <a href="https://news.sky.com/story/uk-heatwave-britains-green-landscapes-turn-brown-as-river-flows-drop-12669994">latest satellite image</a> of England captured by Nasa shows not a green and pleasant land but one which is brown and parched. Under all that dry vegetation is sun-baked, dusty and desiccated soil.</p>
<p>Heavy rain and thundery showers are now <a href="https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2022/days-of-thunder-ahead-for-some">forecast</a> for much of the UK. No doubt the promise of a good downpour will please farmers, for whom the drought has been particularly punishing. Bizarrely though, heavy rain may not be what their thirsty soil <a href="https://theconversation.com/drought-heavy-rain-now-might-be-a-serious-problem-for-the-uks-parched-landscape-188666">needs right now</a>. </p>
<p>A soil normally acts like a sponge which soaks up moisture when it rains. Having been baked for weeks by intense heat with little respite, soil surfaces have hardened. </p>
<p>As a result, the soil’s infiltration capacity (the maximum rate at which soils can absorb moisture) has diminished. If rain falls at such an intensity that this rate is exceeded, the water will run off the soil surface, potentially triggering flash floods and other hazards downslope. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/drought-heavy-rain-now-might-be-a-serious-problem-for-the-uks-parched-landscape-188666">Drought: heavy rain now might be a serious problem for the UK's parched landscape</a>
</strong>
</em>
</p>
<hr>
<p>When heavy rain falls, tonnes of soil can be eroded into the flow and rushed out of farm gates. There, it is washed into rivers, and spat out to sea in a brown plume that can occasionally be seen from space. </p>
<p>Likewise, flash floods can leave thousands of households with thick carpets of sand, silt and clay. Cleaning up after extreme rainfall can drain wallets very quickly, but there is a larger and longer-term cost. </p>
<p><a href="https://theconversation.com/soil-is-our-best-ally-in-the-fight-against-climate-change-but-were-fast-running-out-of-it-128166">Soil erosion is a major threat</a> to the resilience of the environment. Proactive measures to curb erosion are essential to ensure soils continue supporting food production, sustaining habitats and biodiversity, cycling nutrients and safely storing the carbon fuelling climate change. </p>
<p>Here are five options for preventing soil running off the land. </p>
<figure class="align-center ">
<img alt="Green pea pods on a bush." src="https://images.theconversation.com/files/479387/original/file-20220816-22-4evxl0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479387/original/file-20220816-22-4evxl0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479387/original/file-20220816-22-4evxl0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479387/original/file-20220816-22-4evxl0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479387/original/file-20220816-22-4evxl0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479387/original/file-20220816-22-4evxl0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479387/original/file-20220816-22-4evxl0.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">Planting legumes between crops can restore nitrogen to the soil.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-green-peas-pod-on-bush-2007986741">Igor Bastrakov/Shutterstock</a></span>
</figcaption>
</figure>
<h2>1. Don’t leave soils bare</h2>
<p>A bare soil is particularly vulnerable to erosion. Extreme heat can make some harvests come early, leaving soils bare for longer. Farmers can grow cover crops such as brassicas, legumes and grasses to protect soils from being exposed between periods of crop production.</p>
<p>As well as shielding the soil from rain splash, <a href="https://bsssjournals.onlinelibrary.wiley.com/doi/full/10.1111/ejss.13147">some cover crops</a> can suppress weeds and fungal diseases, replenish carbon and offer food and habitat to wildlife.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-the-humble-legume-could-be-the-answer-to-europes-fertiliser-addiction-159067">Why the humble legume could be the answer to Europe's fertiliser addiction</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="Rows of green, leafy plants separated by wood-strewn soil." src="https://images.theconversation.com/files/479388/original/file-20220816-8415-oq2vva.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479388/original/file-20220816-8415-oq2vva.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479388/original/file-20220816-8415-oq2vva.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479388/original/file-20220816-8415-oq2vva.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479388/original/file-20220816-8415-oq2vva.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479388/original/file-20220816-8415-oq2vva.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479388/original/file-20220816-8415-oq2vva.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">Soybeans grown without tilling the soil.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/soybeans-were-notill-argentina-795513256">Helga_foto/Shutterstock</a></span>
</figcaption>
</figure>
<h2>2. Adapt tillage practices</h2>
<p>Soil tillage (digging, stirring and overturning it) is one of the most practised methods of preparing the land for growing crops. But tilling the soil too vigorously can damage its internal structure. </p>
<p>A healthy soil has a continuous network of pores and channels capable of storing and transporting air and water. Lining this network are mineral and organic aggregates. Maintaining the soil’s structure is vital, not only for bolstering its resistance to erosion, but for enhancing how much water can infiltrate it.</p>
<p>Shifting towards less intensive tillage practices – reduced or zero tillage farming – has been shown to be <a href="https://iopscience.iop.org/article/10.1088/1748-9326/aba2fd/meta">effective</a> at curbing soil erosion. Ploughing across slopes rather than down them can reduce it even further.</p>
<h2>3. Watch out for overgrazing</h2>
<p>Grazing livestock like cattle can maintain grassland habitats and support native wildlife, but overgrazing can be a <a href="https://www.worldwildlife.org/threats/soil-erosion-and-degradation">problem</a>. If vegetation is stripped from the land faster than it can naturally recover, soils are left bare and prone to erosion. </p>
<p>Overgrazing can also compact the soil, making it less effective at soaking up moisture and increasing the likelihood that water will run off the surface. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/farm-vehicles-now-weigh-almost-as-much-as-heaviest-dinosaurs-heres-why-thats-a-problem-182992">Farm vehicles now weigh almost as much as heaviest dinosaurs – here’s why that’s a problem</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="A hillside with flat terraces." src="https://images.theconversation.com/files/479386/original/file-20220816-1633-wpw8xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479386/original/file-20220816-1633-wpw8xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479386/original/file-20220816-1633-wpw8xu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479386/original/file-20220816-1633-wpw8xu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479386/original/file-20220816-1633-wpw8xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479386/original/file-20220816-1633-wpw8xu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479386/original/file-20220816-1633-wpw8xu.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 terraced rice paddy field in northern Vietnam.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/terraced-rice-paddy-field-landscape-mu-1914393187">Southtownboy Studio/Shutterstock</a></span>
</figcaption>
</figure>
<h2>4. Consider terracing steep slopes</h2>
<p>Steep slopes funnel water downhill fast. Building a series of level steps into the slope where food can be grown, a practice known as terracing, is an effective engineering solution.</p>
<p>Hillslope terracing has been adopted by farmers for millennia, and can be particularly good at reducing water runoff and sediment erosion, especially if regularly maintained. Levelling the slope can also help water infiltrate the soil and increase how much water it can hold. </p>
<figure class="align-center ">
<img alt="A strip of wildflowers between rows of vines." src="https://images.theconversation.com/files/479383/original/file-20220816-21-xhzq0n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479383/original/file-20220816-21-xhzq0n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479383/original/file-20220816-21-xhzq0n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479383/original/file-20220816-21-xhzq0n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479383/original/file-20220816-21-xhzq0n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479383/original/file-20220816-21-xhzq0n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479383/original/file-20220816-21-xhzq0n.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">Buffer strips can be a nectar buffet for pollinating bugs.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/green-seeded-cover-crop-vineyard-row-1924241822">Digikluk/Shutterstock</a></span>
</figcaption>
</figure>
<h2>5. Grow a buffer strip</h2>
<p>For fields bordering rivers and streams, planting buffer strips of vegetation on the boundary with the watercourse can <a href="https://bsssjournals.onlinelibrary.wiley.com/doi/full/10.1111/sum.12057?casa_token=IU50b-84leYAAAAA%3AJf_kryjB1VK2ZHMWHROgHB7cILqSV3axI1bng381QK6UJhddgbGUYexNQC2Jz_IweLhFc8uZFkIWDw">offer multiple benefits</a> beyond reducing soil erosion. </p>
<p>Comprised of grass and shrubs, buffer strips increase the roughness of the land which slows the water running off it. Planting trees in buffer strips can help stabilise riverbanks, shade livestock and reduce the runoff of agricultural chemicals into rivers. As well as combating soil erosion, buffer strips feed and shelter pollinating insects, enriching a farm’s biodiversity.</p>
<h2>Be proactive not reactive</h2>
<p>It only takes a second to open an umbrella and protect yourself from a downpour. Protecting soil from erosion demands more proactive measures. </p>
<p>These five recommendations can build a soil’s resistance to erosion, particularly during the spells of heavy rain which often follow heatwaves. If implemented and maintained, these strategies can have lasting additional benefits for soil fertility, biodiversity and slowing climate change.</p><img src="https://counter.theconversation.com/content/188765/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dan Evans has received funding from UK Research and Innovation (UKRI). </span></em></p>Storms and flash floods often follow a heatwave.Dan Evans, 75th Anniversary Research Fellow, Soil and Agrifood Institute, Cranfield UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1879512022-07-29T15:23:32Z2022-07-29T15:23:32ZClimate change is intensifying the water cycle, bringing more powerful storms and flooding – here’s what the science shows<figure><img src="https://images.theconversation.com/files/476720/original/file-20220729-5473-5b7s35.jpg?ixlib=rb-1.1.0&rect=0%2C106%2C3284%2C2137&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">At least 9 inches of rain across eastern Kentucky became floodwater that swept through neighborhoods in July 2022.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/aerial-view-of-homes-submerged-under-flood-waters-from-the-news-photo/1242170051">Leandro Lozada/AFP via Getty Images</a></span></figcaption></figure><p>Powerful storm systems triggered flash flooding across the U.S. in late July, killing <a href="https://twitter.com/GovAndyBeshear/status/1554221064506544131">more than three dozen people</a> in eastern Kentucky as floodwater engulfed homes and set off mudslides. Record rainfall also inundated <a href="https://www.stltoday.com/news/local/metro/cleanup-begins-in-waterlogged-st-louis-region-as-rain-persists/article_32985632-7ec4-5fd4-9dcb-bc87e32c9fb3.html">St. Louis neighborhoods</a>, and another <a href="https://twitter.com/mickakers/status/1552881732348628992">deluge in Nevada flooded the</a> <a href="https://www.reviewjournal.com/local/weather/downtown-las-vegas-sees-flooding-in-late-night-july-storm-2614211/">Las Vegas strip</a>.</p>
<p>The impact of climate change on extreme water-related events like this is becoming increasingly evident. The storms in the U.S. followed extreme flooding this summer in <a href="https://www.cnn.com/2022/06/22/india/bangladesh-india-floods-death-toll-intl-hnk/index.html">India</a> and <a href="https://www.bbc.com/news/world-australia-61991112">Australia</a> and last year in <a href="https://www.science.org/content/article/europe-s-deadly-floods-leave-scientists-stunned">Western Europe</a>.</p>
<p>Studies by scientists around the world show that the water cycle has been intensifying and will continue to intensify as the planet warms. An <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">international climate assessment</a> I coauthored in 2021 for the Intergovernmental Panel on Climate Change lays out the details.</p>
<p>It documented an increase in both wet extremes, including more intense rainfall over most regions, and dry extremes, including drying in the Mediterranean, southwestern Australia, southwestern South America, South Africa and western North America. It also shows that both wet and dry extremes will continue to increase with future warming.</p>
<h2>Why is the water cycle intensifying?</h2>
<p>Water cycles through the environment, moving between the atmosphere, ocean, land and reservoirs of frozen water. It might fall as rain or snow, seep into the ground, run into a waterway, join the ocean, freeze or evaporate back into the atmosphere. Plants also take up water from the ground and <a href="https://www.usgs.gov/special-topics/water-science-school/science/evapotranspiration-and-water-cycle">release it through transpiration</a> from their leaves. In recent decades, there has been an overall increase in the rates of precipitation and evaporation.</p>
<p>A number of factors are intensifying the water cycle, but one of the most important is that warming temperatures raise the upper limit on the amount of moisture in the air. That increases the potential for more rain.</p>
<p><iframe id="GynkN" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/GynkN/8/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>This aspect of climate change is confirmed across <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">all of our lines of evidence</a> discussed in the IPCC report. It is expected from basic physics, projected by computer models, and it already shows up in the observational data as a general increase of rainfall intensity with warming temperatures.</p>
<p>Understanding this and other changes in the water cycle is important for more than preparing for disasters. Water is an essential resource for all ecosystems and human societies, and particularly agriculture.</p>
<h2>What does this mean for the future?</h2>
<p>An intensifying water cycle means that both wet and dry extremes and the general variability of the water cycle will increase, although not uniformly around the globe.</p>
<p>Rainfall intensity is <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">expected to increase for most land areas</a>, but the largest increases in dryness are expected in the Mediterranean, southwestern South America and western North America.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Maps showing precipitation projections and warming projections at 1.5 and 3 degrees Celsius." src="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.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">Annual average precipitation is projected to increase in many areas as the planet warms, particularly in the higher latitudes.</span>
<span class="attribution"><a class="source" href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">IPCC Sixth Assessment Report</a></span>
</figcaption>
</figure>
<p>Globally, daily extreme precipitation events will likely intensify by about <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">7% for every 1 degree Celsius</a> (1.8 degrees Fahrenheit) that global temperatures rise.</p>
<p>Many other important aspects of the water cycle will also change in addition to extremes as global temperatures increase, the report shows, including reductions in mountain glaciers, decreasing duration of seasonal snow cover, earlier snowmelt and contrasting changes in monsoon rains across different regions, which will impact the water resources of billions of people.</p>
<h2>What can be done?</h2>
<p>One common theme across these aspects of the water cycle is that <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">higher greenhouse gas emissions lead to bigger impacts</a>.</p>
<p>The IPCC does not make policy recommendations. Instead, it provides the scientific information needed to carefully evaluate policy choices. The results show what the implications of different choices are likely to be.</p>
<p>One thing the <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">scientific evidence in the report</a> clearly tells world leaders is that limiting global warming to the Paris Agreement target of 1.5 C (2.7 F) will require immediate, rapid and large-scale reductions in greenhouse gas emissions.</p>
<p>Regardless of any specific target, it is clear that the severity of climate change impacts are closely linked to greenhouse gas emissions: Reducing emissions will reduce impacts. Every fraction of a degree matters.</p>
<p><em>This article was updated Aug. 1, 2022, with the Kentucky death toll rising.</em></p><img src="https://counter.theconversation.com/content/187951/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mathew Barlow received travel funding from the US government to attend three IPCC lead author meetings.</span></em></p>Extreme downpours caught people off guard from Las Vegas to Kentucky in July 2022.Mathew Barlow, Professor of Climate Science, UMass LowellLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1853642022-07-05T12:14:47Z2022-07-05T12:14:47ZClimate change is making flooding worse: 3 reasons the world is seeing more record-breaking deluges and flash floods<figure><img src="https://images.theconversation.com/files/471429/original/file-20220628-14613-2mjpl2.jpg?ixlib=rb-1.1.0&rect=0%2C37%2C3134%2C2056&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fast-moving floodwater obliterated sections of major roads through Yellowstone National Park in 2022.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/yellowstonenps/52167350392">Jacob W. Frank/National Park Service</a></span></figcaption></figure><p>Heavy rain combined with melting snow can be a destructive combination. </p>
<p>In June 2022, storms dumped up to 5 inches of rain over three days in the mountains in and around Yellowstone National Park, rapidly melting snowpack. As the rain and meltwater poured into creeks and then rivers, it became a flood that damaged roads, cabins and utilities and <a href="https://apnews.com/article/floods-travel-montana-obituaries-evacuations-3753caa39435d9f3f45d8b582381a0c6">forced more than 10,000 people to evacuate</a>.</p>
<p>The Yellowstone River shattered its previous record and reached its highest water levels recorded since monitoring began almost 100 years ago.</p>
<p>Although floods are a natural occurrence, human-caused climate change is <a href="https://www.gyclimate.org/">making severe flooding events like these more common</a>. I study how climate change affects hydrology and flooding. In mountainous regions, three effects of climate change in particular are creating higher flood risks: more intense precipitation, shifting snow and rain patterns and the effects of wildfires on the landscape.</p>
<h2>Warmer air leads to more intense precipitation</h2>
<p>One effect of climate change is that a <a href="https://www.epa.gov/climate-indicators/climate-change-indicators-heavy-precipitation">warmer atmosphere creates more intense precipitation events</a>. </p>
<p>This occurs because warmer air can hold more moisture. The amount of water vapor that the atmosphere can contain increases by <a href="https://doi.org/10.1038/nclimate1452">about 7% for every 1.8 degrees Fahrenheit</a> (1 degree Celsius) of increase in atmospheric temperature.</p>
<p>Research has documented that this <a href="https://doi.org/10.1029/2018WR024067">increase in extreme precipitation is already occurring</a>, not only in regions like Yellowstone, but <a href="https://theconversation.com/global-evidence-links-rise-in-extreme-precipitation-to-human-driven-climate-change-163715">around the globe</a>. The fact that the world has experienced multiple record flooding events in recent years – including catastrophic <a href="https://www.bbc.com/news/world-australia-61991112">flooding in</a> <a href="http://www.bom.gov.au/climate/enso/wrap-up/archive/20220705.archive.shtml">Australia</a>, <a href="https://www.science.org/content/article/europe-s-deadly-floods-leave-scientists-stunned">Western Europe</a> <a href="https://weather.com/en-IN/india/monsoon/news/2022-07-12-around-1k-rescued-from-gujarat-floods-heavy-rains-to-continue">India</a> and <a href="https://www.washingtonpost.com/weather/2021/07/21/zhengzhou-china-record-rain-flooding/">China</a> – is not a coincidence. Climate change is making record-breaking extreme precipitation more likely.</p>
<figure class="align-center ">
<img alt="A woman with work gloves and clothing covered in mud walks through a muddy residential street filled with mud-covered furniture and other damaged belongings people are throwing out after a flood." src="https://images.theconversation.com/files/471466/original/file-20220628-16342-auzmdw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471466/original/file-20220628-16342-auzmdw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471466/original/file-20220628-16342-auzmdw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471466/original/file-20220628-16342-auzmdw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471466/original/file-20220628-16342-auzmdw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471466/original/file-20220628-16342-auzmdw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471466/original/file-20220628-16342-auzmdw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Extreme rain storms triggered flooding and mudslides in Western Europe in July 2021, killing more than 200 people.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/volunteers-and-residents-start-the-clean-up-process-at-news-photo/1329350141?adppopup=true">Thomas Lohnes/Getty Images</a></span>
</figcaption>
</figure>
<p><iframe id="zBAAz" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/zBAAz/5/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>The latest <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">assessment report</a> published by the Intergovernmental Panel on Climate Change shows how this pattern will continue in the future as global temperatures continue to rise.</p>
<h2>More precipitation falling as rain</h2>
<p>In colder areas, especially mountainous or high-latitude regions, climate change affects flooding in additional ways. </p>
<p>In these regions, many of the largest historical <a href="https://doi.org/10.1002/2016GL068070">floods have been caused by snowmelt</a>. However, with warmer winters due to climate change, <a href="https://www.climatecentral.org/news/winters-becoming-more-rainy-across-us-20017">less winter precipitation is falling as snow</a>, and more is falling as rain instead.</p>
<p>This shift from snow to rain can have dramatic implications for flooding. While snow typically melts slowly in the late spring or summer, rain creates runoff that flows to rivers more quickly. As a result, research has shown that <a href="https://doi.org/10.1029/2022GL098855">rain-caused floods can be much larger than snowmelt-only floods</a>, and that the shift from snow to rain <a href="https://doi.org/10.1029/2019WR025571">increases overall flood risk</a>.</p>
<p>The transition from snow to rain is already occurring, <a href="https://theconversation.com/yellowstone-is-losing-its-snow-as-the-climate-warms-and-that-means-widespread-problems-for-water-and-wildlife-163223">including in places like Yellowstone National Park</a>. Scientists have also found that <a href="https://doi.org/10.1002/2015WR017784">rain-caused floods are becoming more common</a>. In some locations, the changes in flood risk due to the shift from snow to rain could even be larger than the effect from increased precipitation intensity.</p>
<p><iframe id="O1p7r" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/O1p7r/5/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>Changing patterns of rain on snow</h2>
<p>When <a href="https://doi.org/10.1175/BAMS-88-3-319">rain falls on snow</a>, as happened in the recent flooding in Yellowstone, the combination of rain and snowmelt can lead to especially high runoff and flooding.</p>
<p>In some cases, rain-on-snow events occur while the ground is still partially frozen. Soil that is frozen or already saturated can’t absorb additional water, so even more of the rain and snowmelt run off, contributing directly to flooding. This combination of rain, snowmelt and frozen soils was a primary driver of the <a href="https://www.nytimes.com/2019/03/18/us/nebraska-flooding-facts.html">Midwest flooding in March 2019</a> that caused over US$12 billion in damage.</p>
<p>While rain-on-snow events are not a new phenomenon, climate change can shift when and where they occur. Under warmer conditions, <a href="https://doi.org/10.1038/s41558-018-0236-4">rain-on-snow events become more common at high elevations</a>, where they were previously rare. Because of the increases in rainfall intensity and warmer conditions that lead to rapid snowmelt, there is also the possibility of larger rain-on-snow events than these areas have experienced in the past.</p>
<figure class="align-center ">
<img alt="A large two-story building is collapsing after fast-moving water eroded the land under nearly half of it." src="https://images.theconversation.com/files/471431/original/file-20220628-14648-yhqe7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471431/original/file-20220628-14648-yhqe7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471431/original/file-20220628-14648-yhqe7t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471431/original/file-20220628-14648-yhqe7t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471431/original/file-20220628-14648-yhqe7t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471431/original/file-20220628-14648-yhqe7t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471431/original/file-20220628-14648-yhqe7t.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 2022 Yellowstone flood inundated communities and swiftly eroded the land beneath this cabin that housed park employees.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/yellowstonenps/52146801150">Gina Riquier via National Park Service</a></span>
</figcaption>
</figure>
<p>In lower-elevation regions, rain-on-snow events may actually become less likely than they have been in the past because of the decrease in snow cover. These areas could still see worsening flood risk, though, because of the increase in heavy downpours.</p>
<h2>Compounding effects of wildfire and flooding</h2>
<p>Changes in flooding are not happening in isolation. Climate change is also exacerbating <a href="https://www.nationalgeographic.com/science/article/climate-change-increases-risk-fires-western-us">wildfires</a>, creating another risk during rainstorms: mudslides. </p>
<p>Burned areas are more <a href="https://doi.org/10.1029/2020EF001735">susceptible to mudslides and debris flows during extreme rain</a>, both because of the lack of vegetation and changes to the soil caused by the fire. In 2018 in Southern California, heavy rain within the boundary of the <a href="https://www.cnn.com/2018/06/02/us/thomas-fire-officially-out/index.html">2017 Thomas Fire</a> caused <a href="https://www.cnn.com/2018/01/11/us/mudslide-slider-california/index.html">major mudslides</a> that destroyed over 100 homes and led to more than 20 deaths. Fire can change the soil in ways that allow <a href="https://doi.org/10.2113/EEG-D-20-00029">less rain to infiltrate into the soil</a>, so more rain ends up in streams and rivers, leading to worse flood conditions.</p>
<figure class="align-center ">
<img alt="Two men point stand on a deck overlooking a neighboring house where mud has flowed through the yard and is mounded half way up the side of the home." src="https://images.theconversation.com/files/471467/original/file-20220628-14559-d6mcuz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471467/original/file-20220628-14559-d6mcuz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471467/original/file-20220628-14559-d6mcuz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471467/original/file-20220628-14559-d6mcuz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471467/original/file-20220628-14559-d6mcuz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471467/original/file-20220628-14559-d6mcuz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471467/original/file-20220628-14559-d6mcuz.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 2021 rainstorm that hit the denuded landscape of a burn scar sent mud flowing into streets and yards in Silverado, California.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/two-men-survey-the-damage-from-mud-and-debris-that-ran-news-photo/1299356465">Paul Bersebach/MediaNews Group/Orange County Register via Getty Images</a></span>
</figcaption>
</figure>
<p>With the uptick in wildfires due to climate change, more and more areas are exposed to these risks. This combination of wildfires followed by extreme rain will also become <a href="https://doi.org/10.1126/sciadv.abm0320">more frequent in a future with more warming</a>.</p>
<p>Global warming is creating complex changes in our environment, and there is a clear picture that it increases flood risk. As the Yellowstone area and other flood-damaged mountain communities rebuild, they will have to find ways to adapt for a riskier future.</p><img src="https://counter.theconversation.com/content/185364/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Frances Davenport 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>Extreme downpours brought deadly flooding to the Appalachian region, just a few weeks after the destructive Yellowstone River flood.Frances Davenport, Assistant Professor of Civil and Environmental Engineering, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1830362022-05-17T04:20:36Z2022-05-17T04:20:36ZWhen roads become rivers: forming a Plan B can stop people driving into floodwaters<p>Queensland residents are facing yet another arduous clean-up after <a href="https://www.9news.com.au/national/weather-update-lockyer-valley-residents-urged-to-self-evacuate-as-queenslands-record-breaking-deluge-continues/adf1d472-ea5d-4935-be55-bbc31302ec39">floods inundated</a> roads and towns last week.</p>
<p>In the current La Niña period, from November 2021 to present, <a href="https://riskfrontiers.com/insights/flood-rain-events-decade-2011-2022/">at least 41 people have died</a> (including three missing presumed dead) from floods across south-east Queensland, northern New South Wales, Greater Sydney, and Victoria. Many involved decisions to enter floodwater, often in vehicles. </p>
<p>Indeed, driving into floodwater is the <a href="https://www.sciencedirect.com/science/article/abs/pii/S2212420918308604?via%3Dihub">leading cause</a> of flood-related death. Despite media campaigns – such as Queensland’s “<a href="https://www.qld.gov.au/about/newsroom/if-its-flooded-forget-it">If It’s Flooded, Forget It</a>” advertisements – people continue to enter the unpredictable water, risking their lives and the lives of their <a href="https://onlinelibrary.wiley.com/doi/10.1002/hpja.181">rescuers</a>. </p>
<p>Our research exploring reasons <a href="https://www.sciencedirect.com/science/article/abs/pii/S2212420918301869">why people drive into</a> and <a href="https://www.sciencedirect.com/science/article/abs/pii/S2212420917303898">avoid driving into</a> floodwater has provided comprehensive insights into this behaviour. Having a Plan B could be the difference between life and death in these situations. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/LesXFcaFFQk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Queensland’s campaign to stop drivers entering floodwaters.</span></figcaption>
</figure>
<h2>Why people drive on flooded roads</h2>
<p>We surveyed people who had previously driven into floodwaters for our research. We found many drivers acknowledge the dangers associated with entering floodwaters, though many identify circumstances where they think it’s safe to do so. </p>
<p>But only a small error in judgement can result in <a href="https://www.dfes.wa.gov.au/safetyinformation/flood/FloodResearch/DFES-Post-flood-Research-Report-2017.pdf">tragedy</a>. Water can flow faster than anticipated, rise rapidly, and roads can be washed away, but not visible under murky floodwater. In fact, water can move fast enough to strip bitumen from roads and damage bridges.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-people-try-to-drive-through-floodwater-or-leave-it-too-late-to-flee-psychology-offers-some-answers-157577">Why do people try to drive through floodwater or leave it too late to flee? Psychology offers some answers</a>
</strong>
</em>
</p>
<hr>
<p>A small car can float in just <a href="https://www.ses.vic.gov.au/news-and-media/campaigns/15-to-float">15 centimetres of floodwater</a>. The record-breaking floods in Lismore earlier this year saw flood waters peak at 14.4 metres, higher than the town’s levees. Dangerous floodwaters can be experienced even during minor flooding and have been widespread in recent months.</p>
<p>We learned many of the reasons people <a href="https://www.sciencedirect.com/science/article/pii/S2212420918301869">chose to drive into floodwaters</a> were based on feeling pressure. Pressure to get to work, school, or home to family or pets. Pressure from passengers in the vehicle. Or pressure from other motorists on the road. </p>
<p>As one respondent said: </p>
<blockquote>
<p>I saw, this is going to sound dreadful, I saw signs up saying the road was closed. But there were cars, four-wheel-drives coming towards me </p>
<p>I thought ‘oh I should turn around, I should turn around’. But I was panicking about being late for work […] And when I saw four-wheel-drives coming towards me I thought, ‘okay I can do this’.</p>
</blockquote>
<p>Another said: </p>
<blockquote>
<p>It was mainly the pressure […] to get there and lecture. The silly thing is once I got through [the floodwater], people were saying [my workplace] was out of power and totally flooded in there and they were cancelling the lecture anyway.</p>
</blockquote>
<h2>What we found</h2>
<p><a href="https://doi.org/10.25904/1912/4395">Our research</a> from 2021 was conducted with the State Emergency Service in Newcastle, New South Wales – an area prone to regular flooding. It showed promising results for making plans with “if/then” scenarios in place. In other words <em>if</em> you were to be in a particular scenario or a danger were to arise, <em>then</em> what would you do? </p>
<p>Making alternative plans may stop drivers from being faced with a situation where they feel they need to drive into floodwaters. We experimentally tested if/then plans in Newcastle using two scenarios:</p>
<ol>
<li><p>you have a trip planned but receive an alert to potential moderate or major flooding in Newcastle before you have started driving</p></li>
<li><p>you approach a flooded section of road, and you are being pressured by other cars to drive into the floodwater.</p></li>
</ol>
<p>For scenario 1, an example if/then plan was: “If its time to leave work and I receive an alert for moderate or major flooding then I will stay at work until it is safe for me to proceed.”</p>
<p>For scenario 2, an example if/then plan was: “If cars behind me are pressuring me to drive through floodwater, then I will turn my hazards on and let them pass, then turn around.”</p>
<p>After an exercise exploring these scenarios with survey respondents, people reported being more willing to stay put until the threat had passed for scenario 1, and less willing to drive into floodwater after feeling pressured from other drivers for scenario 2. </p>
<h2>Forming your own Plan B</h2>
<p>Our findings show the importance of having a detailed if/then plan – a Plan B – for specific scenarios, as it can lower your chances of engaging in risky, potentially life-threatening driving during floods. </p>
<p>Your Plan B examples may include: </p>
<ul>
<li><p>picking up children early from school or day care </p></li>
<li><p>allowing workers to leave early if flooding is predicted or work from home</p></li>
<li><p>knowing alternate routes should your intended route be flooded </p></li>
<li><p>preparing to have safe alternative behaviours, despite pressures to drive through. </p></li>
</ul>
<p>Reinforcing your Plan B is vital to its success when faced with needing to make a quick decision in the moment. </p>
<p>We encourage people to formulate their plans for several scenarios, put these plans in writing, and revisit them regularly by posting them on the fridge and in the car. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/in-a-year-of-endless-floods-why-isnt-disaster-governance-front-and-centre-in-the-election-campaign-183026">In a year of endless floods, why isn't disaster governance front and centre in the election campaign?</a>
</strong>
</em>
</p>
<hr>
<p>It’s also a good idea to verbally communicate your plan to significant others, such as friends, family and work colleagues and employers, as an additional layer of intent to solidify your plan should flooding hit. </p>
<p>With Queensland in the grips of yet another flood crisis and <a href="https://www.theguardian.com/australia-news/2022/mar/18/when-will-eastern-australias-wet-weather-end-and-will-we-get-a-la-nina-three-peat">La Niña predicted</a> to last through May, and potentially into Winter, more extreme rainfall and flooded roads should be expected. </p>
<p>Forming your Plan B now just might help you make safer decisions, should the worst happen.</p><img src="https://counter.theconversation.com/content/183036/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amy Peden is a research fellow in the School of Population Health, UNSW Sydney, an honorary Senior Research Fellow with Royal Life Saving Society - Australia and a co-founder of the UNSW Beach Safety Research Group. Dr Peden currently receives funding from the National Health and Medical Research Council (NH&MRC) and has received funding from the New South Wales Natural Disaster Resilience Program and the City of Newcastle.</span></em></p><p class="fine-print"><em><span>Andrew Gissing has received funding from the Bushfire and Natural Hazards Cooperative Research Centre</span></em></p><p class="fine-print"><em><span>Kyra Hamilton has received research funding from Royal Life Saving Society - Australia and New South Wales Natural Disaster Resilience Program and the City of Newcastle.</span></em></p>Driving into floodwater is the leading cause of flood-related death. So why do people do it?Amy Peden, Research fellow, UNSW SydneyAndrew Gissing, General Manager, Risk Frontiers, Adjunct Fellow, Macquarie UniversityKyra Hamilton, Associate Professor, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1783162022-03-07T03:40:58Z2022-03-07T03:40:58ZThe east coast rain seems endless. Where on Earth is all the water coming from?<figure><img src="https://images.theconversation.com/files/450282/original/file-20220307-83257-izxlcb.jpg?ixlib=rb-1.1.0&rect=48%2C8%2C5319%2C3404&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Jason O'Brien/AAP</span></span></figcaption></figure><p>At any one time, Earth’s atmosphere holds only about <a href="https://www.nature.com/articles/s43017-021-00181-9">a week’s worth</a> of rain. But rainfall and floods have devastated Australia’s eastern regions for weeks and more heavy rain is <a href="https://www.smh.com.au/environment/weather/sydney-in-the-firing-line-fresh-flooding-concerns-as-more-rain-on-the-way-for-state-20220307-p5a2b4.html">forecast</a>. So where’s all this water coming from?</p>
<p>We recently <a href="https://journals.ametsoc.org/view/journals/clim/aop/JCLI-D-21-0750.1/JCLI-D-21-0750.1.xml">investigated</a> the physical processes driving rainfall in eastern Australia. By following moisture from the oceans to the land, we worked out exactly how three oceans feed water to the atmosphere, conspiring to deliver deluges of rain similar to what we’re seeing now.</p>
<p>Such research is important. A better understanding of how water moves through the atmosphere is vital to more accurately forecast severe weather and help communities prepare.</p>
<p>The task takes on greater urgency under climate change, when heavy rainfall and other weather extremes are expected to become more frequent and violent. </p>
<figure class="align-center ">
<img alt="aerial view of flooded streets and roofs" src="https://images.theconversation.com/files/450279/original/file-20220307-84943-1crrnj1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/450279/original/file-20220307-84943-1crrnj1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/450279/original/file-20220307-84943-1crrnj1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/450279/original/file-20220307-84943-1crrnj1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/450279/original/file-20220307-84943-1crrnj1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/450279/original/file-20220307-84943-1crrnj1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/450279/original/file-20220307-84943-1crrnj1.jpg?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">
<figcaption>
<span class="caption">Rain has hammered Australia’s east coast for weeks.</span>
<span class="attribution"><span class="source">Nearmap</span></span>
</figcaption>
</figure>
<h2>Big actors delivering rain</h2>
<p>The past few months in eastern Australia have been very wet, including the <a href="http://www.bom.gov.au/climate/current/statements/scs75.pdf?20220214">rainiest November</a> on record. </p>
<p>Then in February, heavy rain fell on already saturated catchments. In fact, parts of Australia received <a href="http://www.bom.gov.au/climate/maps/rainfall/?variable=rainfall&map=percent&period=month&region=nat&year=2022&month=02&day=28">more than triple</a> the rain expected at this time of year.</p>
<p>So what’s going on?</p>
<p>In the theatre that is Australia’s rainfall, there are some big actors – the so-called climate oscillations. They’re officially known as:</p>
<ul>
<li><p>El Niño-Southern Oscillation (<a href="http://www.bom.gov.au/watl/about-weather-and-climate/australian-climate-influences.shtml?bookmark=enso">ENSO</a>): this cycle comprises El Niño and its opposite, La Niña. ENSO involves temperature changes across the tropical Pacific Ocean, affecting weather patterns around the world</p></li>
<li><p>Southern Annular Mode (<a href="http://www.bom.gov.au/watl/about-weather-and-climate/australian-climate-influences.shtml?bookmark=sam">SAM</a>): the north-south movement of strong westerly winds over the Southern Ocean</p></li>
<li><p>Indian Ocean Dipole (<a href="http://www.bom.gov.au/watl/about-weather-and-climate/australian-climate-influences.shtml?bookmark=iod">IOD</a>): changes in ocean temperatures and winds across the tropical Indian Ocean.</p></li>
</ul>
<p>Like swings in a character’s mood, each climate mode has positive, negative and neutral phases. Each affect Australia’s weather in different ways.</p>
<p>La Niña brings wetter conditions to eastern Australia. The IOD’s negative phase, and SAM’s positive phase, can also bring more rain.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-water-inundates-a-home-during-one-flood-but-spares-it-the-next-178163">Why water inundates a home during one flood but spares it the next</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="woman sits in rain with raincoat and umbrella" src="https://images.theconversation.com/files/450278/original/file-20220307-110738-r43mgd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/450278/original/file-20220307-110738-r43mgd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/450278/original/file-20220307-110738-r43mgd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/450278/original/file-20220307-110738-r43mgd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/450278/original/file-20220307-110738-r43mgd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/450278/original/file-20220307-110738-r43mgd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/450278/original/file-20220307-110738-r43mgd.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">Climate oscillations affect Australia’s weather in different ways.</span>
<span class="attribution"><span class="source">Lucas Coch/AAP</span></span>
</figcaption>
</figure>
<h2>Going back in time</h2>
<p>We <a href="https://journals.ametsoc.org/view/journals/clim/aop/JCLI-D-21-0750.1/JCLI-D-21-0750.1.xml">studied</a> what happens to the moisture supplying eastern Australian rainfall when these climate drivers are in their wet and dry phases.</p>
<p>We used a sophisticated <a href="https://journals.ametsoc.org/view/journals/clim/33/20/jcliD190926.xml?tab_body=fulltext-display">model</a> to trace moisture backwards in time: from where it fell as rain, back through the atmosphere to where it evaporated from. </p>
<p>We did this for every wet winter and spring day between 1979 and 2013.</p>
<p>This research was part of a broader study into where Australia’s rain comes from, and what changes moisture supply during both drought and heavy rain.</p>
<p>We found most rain that falls on eastern Australia comes from moisture evaporated from <a href="https://journals.ametsoc.org/view/journals/clim/33/20/jcliD190926.xml?tab_body=fulltext-display">a nearby ocean</a>. Typically, rain in eastern Australia comes from the Coral and Tasman seas. This is depicted in the strong blue colours in the figure below.</p>
<figure class="align-center ">
<img alt="Eastern Australian rainfall moisture supply." src="https://images.theconversation.com/files/449742/original/file-20220303-19-1rdqqnj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/449742/original/file-20220303-19-1rdqqnj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=445&fit=crop&dpr=1 600w, https://images.theconversation.com/files/449742/original/file-20220303-19-1rdqqnj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=445&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/449742/original/file-20220303-19-1rdqqnj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=445&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/449742/original/file-20220303-19-1rdqqnj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=559&fit=crop&dpr=1 754w, https://images.theconversation.com/files/449742/original/file-20220303-19-1rdqqnj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=559&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/449742/original/file-20220303-19-1rdqqnj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=559&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sources of moisture for rain falling in eastern Australia.</span>
<span class="attribution"><span class="source">Holgate et al, 2020</span></span>
</figcaption>
</figure>
<p>But interestingly, some water comes from as far as the Southern and Indian oceans, and some originates from nearby land areas, such as forests, bare soils, lakes and rivers.</p>
<p>Natural processes can alter the typical supply of moisture to the atmosphere, causing either <a href="https://theconversation.com/we-looked-at-35-years-of-rainfall-and-learnt-how-droughts-start-in-the-murray-darling-basin-145766">droughts</a> or <a href="https://theconversation.com/like-rivers-in-the-sky-the-weather-system-bringing-floods-to-queensland-will-become-more-likely-under-climate-change-176711">floods</a>.</p>
<p>Our research <a href="https://journals.ametsoc.org/view/journals/clim/aop/JCLI-D-21-0750.1/JCLI-D-21-0750.1.xml">shows</a> of all possible combinations of climate oscillations, a La Niña and a positive SAM phase occurring together has the biggest effect on eastern Australian rainfall. That combination is happening right now.</p>
<p>During La Niña, more moisture is transported from the ocean to the atmosphere over land and is more easily converted to rainfall when it arrives. </p>
<p>During the positive SAM, the usual westerly winds shift southward, allowing moisture-laden winds from the east to flow into eastern Australia.</p>
<p>Our research focused on winter and spring. However, we expect the current rainfall is the result of the same combined effect of the two climate oscillations.</p>
<p>The Indian Ocean Dipole is not active at this time of the year. But it was in a weak negative phase last spring, which tends to bring wetter-than-normal conditions.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/back-so-soon-la-nina-heres-why-were-copping-two-soggy-summers-in-a-row-173684">Back so soon, La Niña? Here's why we're copping two soggy summers in a row</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="three boys in wetsuits and boogie boards play in water" src="https://images.theconversation.com/files/450283/original/file-20220307-84357-qlk3ds.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/450283/original/file-20220307-84357-qlk3ds.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=367&fit=crop&dpr=1 600w, https://images.theconversation.com/files/450283/original/file-20220307-84357-qlk3ds.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=367&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/450283/original/file-20220307-84357-qlk3ds.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=367&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/450283/original/file-20220307-84357-qlk3ds.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=461&fit=crop&dpr=1 754w, https://images.theconversation.com/files/450283/original/file-20220307-84357-qlk3ds.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=461&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/450283/original/file-20220307-84357-qlk3ds.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=461&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Most rain falling on eastern Australia comes from moisture evaporated from a nearby ocean.</span>
<span class="attribution"><span class="source">Jason O'Brien</span></span>
</figcaption>
</figure>
<h2>Looking to future floods</h2>
<p>Under climate change, <a href="http://dx.doi.org/10.1038/s43017-021-00199-z">extreme</a> La Niña and El Niño events, and weather systems like those <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021GL095335">causing the current floods</a>, are expected to worsen. So reducing greenhouse gas emissions is crucial.</p>
<p>The current La Niña event is past its peak and is <a href="http://www.bom.gov.au/climate/enso/wrap-up/archive/20220301.archive.shtml">predicted</a> to dissipate in autumn. But because our catchments are so full of water, we still need to be on alert for extreme weather.</p>
<p>The current devastating floods are a sobering lesson for the future. They show the urgent need to understand and predict extreme events, so communities can get ready for them.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/people-couldve-prepared-for-the-floods-better-if-the-impacts-of-weather-forecasts-were-clearly-communicated-178309">People could've prepared for the floods better if the impacts of weather forecasts were clearly communicated</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/178316/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chiara Holgate receives funding from the Australian Research Council Centre of Excellence for Climate Extremes. </span></em></p><p class="fine-print"><em><span>Agus Santoso receives funding from CSIRO. Agus Santoso is a CSIRO adjunct science leader, co-project leader at the Centre for Southern Hemisphere Oceans Research, associate investigator at the ARC Centre of Excellence for Climate Extremes, and is affiliated with the Australian Government's National Environmental Science Program.</span></em></p><p class="fine-print"><em><span>Alex Sen Gupta receives funding from the Australian Research Council as part of the Centre of Excellence for Climate Extremes and the Centre of Excellence in Antarctic Science </span></em></p>By following moisture from the oceans to the land, researchers worked out exactly how three oceans conspire to deliver deluges of rain to eastern Australia.Chiara Holgate, Hydroclimatologist, Australian National UniversityAgus Santoso, Senior Research Associate, UNSW SydneyAlex Sen Gupta, Senior Lecturer, School of Biological, Earth and Environmental Sciences, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1781632022-03-03T02:33:47Z2022-03-03T02:33:47ZWhy water inundates a home during one flood but spares it the next<p>As the floodwaters rose in Southeast Queensland last week, my phone buzzed with texts from friends. We compared this event with the last catastrophic flood of 2011 and tried to calculate whether our homes would be affected this time. I live in Ipswich, not far from the now-flooded Bremer River.</p>
<p>I’m also an expert in the history of natural disasters, including <a href="https://www.uqp.com.au/books/a-river-with-a-city-problem-a-history-of-brisbane-floods">flooding in Brisbane</a>. I watched with interest as social media struggled to keep up with continuous updates on flood levels and photos of rapidly rising water. News reports also made constant references to the 2011 Brisbane floods.</p>
<p>This time, the <a href="https://7news.com.au/news/qld/relentless-rain-to-continue-in-queensland-pushing-brisbane-river-to-its-peak-c-5879987">floodwaters stopped</a> at 3.85 metres at the Brisbane gauge in the central business district – less than the 4.46m peak in 2011. Many homes flooded this year that didn’t flood in 2011 – notably in the northern suburbs of Ashgrove, Windsor and The Gap. Meanwhile, homes in the western suburb of Bellbowrie flooded in 2011 but escaped this time. But why?</p>
<p>As hydrologists will tell you, no two floods are the same. The water may follow familiar paths, but natural and human factors alter flood behaviour each time.</p>
<figure class="align-center ">
<img alt="aerial view of brown flood water and built structures" src="https://images.theconversation.com/files/449693/original/file-20220303-15-1ddlfov.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/449693/original/file-20220303-15-1ddlfov.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/449693/original/file-20220303-15-1ddlfov.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/449693/original/file-20220303-15-1ddlfov.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/449693/original/file-20220303-15-1ddlfov.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/449693/original/file-20220303-15-1ddlfov.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/449693/original/file-20220303-15-1ddlfov.jpg?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">
<figcaption>
<span class="caption">Every flood differs according to natural and human factors.</span>
<span class="attribution"><span class="source">Brett's Drone Photography</span></span>
</figcaption>
</figure>
<h2>How the rain falls</h2>
<p>Rainfall intensity is a key factor in determining the extent of “runoff” – water that flows over the ground rather than soaking in. Heavy rain falling in one hour has a much greater runoff ratio than if the same amount falls over a week. </p>
<p>For example, in January 1974, <a href="https://www.mdpi.com/2073-4441/3/4/1149/htm">872mm of rain</a> fell in Brisbane – including <a href="https://www.jstor.org/stable/26393302?seq=1#metadata_info_tab_contents">314mm on one day</a>, January 26. A flood reached 5.45m at the Brisbane gauge.</p>
<p>Last month’s rain was similarly unrelenting, when <a href="https://www.thenationalnews.com/world/2022/02/28/nine-dead-after-flooding-on-australias-east-coast-as-thousands-leave-brisbane/">611.6mm fell</a> between February 25 and 27. For perspective, Brisbane’s <a href="http://www.bom.gov.au/cgi-bin/wrap_fwo.pl?IDQ60360.html">annual rainfall</a> is 1,149mm. That intensity and volume of rain in one weekend meant flooding was inevitable but very hard to predict.</p>
<p>Where the rain falls also matters. In 2011, heavy rain fell upstream of Wivenhoe Dam. But in 2022 vast quantities fell downstream of the dam, including on the Bremer River and Lockyer Creek, where there are few flood-mitigation structures to manage the extra water. </p>
<p>The adequacy of stormwater infrastructure, such as gutters, drains and pipes that carry water away, also influences the extent of flooding.</p>
<p>Across Southeast Queensland, many local stormwater systems could not cope with the heavy rain, causing overland flow that flooded houses. The problem was particularly acute in <a href="http://www.bom.gov.au/cgi-bin/wrap_fwo.pl?IDQ60360.html">some suburbs</a> that received about a metre of rain over three days. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/one-of-the-most-extreme-disasters-in-colonial-australian-history-climate-scientists-on-the-floods-and-our-future-risk-178153">'One of the most extreme disasters in colonial Australian history': climate scientists on the floods and our future risk</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="men ride bikes over flooded road" src="https://images.theconversation.com/files/449695/original/file-20220303-13-tpgxz0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/449695/original/file-20220303-13-tpgxz0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/449695/original/file-20220303-13-tpgxz0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/449695/original/file-20220303-13-tpgxz0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/449695/original/file-20220303-13-tpgxz0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/449695/original/file-20220303-13-tpgxz0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/449695/original/file-20220303-13-tpgxz0.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">Stormwater systems couldn’t cope with the influx of water.</span>
<span class="attribution"><span class="source">Jono Searle/AAP</span></span>
</figcaption>
</figure>
<h2>What’s happening in the river catchment?</h2>
<p>People have compared this year’s Brisbane floods with 2011, but they are in fact more similar to the 1974 floods.</p>
<p>The Brisbane River catchment is a complex network. It comprises three rivers – the Stanley, Brisbane and Bremer – and many creeks, the largest of which is Lockyer Creek. Heavy rain can cause any, or all, of these rivers and creeks to flood. </p>
<p>In 2011, rivers were the biggest cause of the floods. But this year, while Ipswich and Brisbane experienced river flooding, suburban creeks caused the most extreme flooding, just as they did in 1974. This was because rain fell heavily throughout the entire catchment, filling even the smallest watercourses.</p>
<p>For example, Ithaca Creek last month flooded the suburb of Ashgrove for the first time since 1974. Kedron Brook flooded Windsor and The Grange, which were left dry in 2011. </p>
<p>And rain filled the Enoggera Reservoir to more than double its capacity, overfilling the Fish and Ithaca creeks and flooding the suburb of The Gap.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/after-the-floods-comes-underinsurance-we-need-a-better-plan-178143">After the floods comes underinsurance: we need a better plan</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="bridge over creek submerged by water" src="https://images.theconversation.com/files/449696/original/file-20220303-23-o0dj39.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/449696/original/file-20220303-23-o0dj39.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=271&fit=crop&dpr=1 600w, https://images.theconversation.com/files/449696/original/file-20220303-23-o0dj39.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=271&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/449696/original/file-20220303-23-o0dj39.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=271&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/449696/original/file-20220303-23-o0dj39.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=341&fit=crop&dpr=1 754w, https://images.theconversation.com/files/449696/original/file-20220303-23-o0dj39.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=341&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/449696/original/file-20220303-23-o0dj39.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=341&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Enoggera Reservoir overflowed, flooding creeks and suburbs.</span>
<span class="attribution"><a class="source" href="https://sown.com.au/enoggera-creeks-in-flood/">Mark Crocker</a></span>
</figcaption>
</figure>
<h2>Humans affect floods, too</h2>
<p>Humans can significantly influence the extent of floods. Every time a tree is felled, wetland drained or land developed, the local flood risk is potentially heightened. </p>
<p>Housing estates are built densely – small subdivisions occupied by large houses. And homes are constructed on slabs, rather than elevated to allow water to pass underneath. </p>
<p>Soil and vegetation can absorb water and slow the rate of flooding. But impermeable surfaces such as roads, footpaths and carparks increase surface runoff.</p>
<p>Bridges, ferry terminals and pontoons intrude on waterways, made worse by debris that becomes entangled. Buildings, railway embankments and roads can block waterways, effectively creating dams. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ipcc-report-coastal-cities-are-sentinels-for-climate-change-its-where-our-focus-should-be-as-we-prepare-for-inevitable-impacts-177726">IPCC report: Coastal cities are sentinels for climate change. It's where our focus should be as we prepare for inevitable impacts</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="new home beside cleared lot" src="https://images.theconversation.com/files/449698/original/file-20220303-15-1px6gzg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/449698/original/file-20220303-15-1px6gzg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=388&fit=crop&dpr=1 600w, https://images.theconversation.com/files/449698/original/file-20220303-15-1px6gzg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=388&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/449698/original/file-20220303-15-1px6gzg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=388&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/449698/original/file-20220303-15-1px6gzg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=487&fit=crop&dpr=1 754w, https://images.theconversation.com/files/449698/original/file-20220303-15-1px6gzg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=487&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/449698/original/file-20220303-15-1px6gzg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=487&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Reclaiming natural spaces for housing can increase water runoff.</span>
<span class="attribution"><span class="source">Dan Peled/ AAP</span></span>
</figcaption>
</figure>
<h2>Learning from history</h2>
<p>History can help us measure the likelihood of flooding and prompt us to prepare, but it’s not that simple. Past experience can also confuse and reduce the perception of risk. </p>
<p>Increasing public awareness is important in mitigating flood risks, as is individual responsibility. But planning authorities must also make hard decisions.</p>
<p>Developers have been allowed to increase the urban footprint and density throughout southeast Queensland. This has created more hard, impermeable surfaces and replaced absorbent green spaces, increasing the likelihood of flooding. </p>
<p>This comes as climate change is predicted to increase the frequency and intensity of floods, and make flood predictions more difficult. </p>
<p>We can’t directly control the rain, but we can change how we respond to future flood hazards.</p>
<hr>
<p><em>Margaret Cook is the author of <a href="https://www.uqp.com.au/books/a-river-with-a-city-problem-a-history-of-brisbane-floods">A River with a City Problem: A History of Brisbane Floods</a>.</em></p><img src="https://counter.theconversation.com/content/178163/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Margaret Cook 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>As history shows, many natural and human factors determine how water will behave during a flood.Margaret Cook, Lecturer in History, University of the Sunshine CoastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1725112021-12-01T17:10:30Z2021-12-01T17:10:30ZDo La Niña’s rains mean boom or bust for Australian farmers?<figure><img src="https://images.theconversation.com/files/434907/original/file-20211201-13-128xtfb.jpg?ixlib=rb-1.1.0&rect=14%2C28%2C9475%2C6288&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>After years of punishing drought in some areas, many farmers in Australia’s east were hoping the <a href="http://www.bom.gov.au/climate/enso/">newly declared La Niña event</a> would bring them good rains. </p>
<p>Many are now rejoicing, with the wettest November experienced in Australia for more than two decades. But for some farmers, heavy and prolonged rain is causing a new set of problems.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1465885247115972612"}"></div></p>
<p>Last year’s La Niña delivered good rainfall in some areas – while leaving others drier than they would have been under an El Niño, with many areas in southern Queensland missing out. In La Niña years, the cattle farming town of Roma receives an average of 247mm from November to the end of January. Last year they only got half that. </p>
<p>This year’s La Niña has already delivered rain to many areas left dry last year. Roma, for example, has received more than 200mm in November 2021 alone. These large rainfall events and seasons are required after ongoing drought to recharge the moisture in the soil. </p>
<p>But continued rain will be less welcome in newly waterlogged areas along the Queensland and NSW border and the Northern Rivers region, given it may lead to further flooding.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-is-likely-driving-a-drier-southern-australia-so-why-are-we-having-such-a-wet-year-172409">Climate change is likely driving a drier southern Australia – so why are we having such a wet year?</a>
</strong>
</em>
</p>
<hr>
<h2>What does La Nina mean for farmers?</h2>
<p><a href="http://www.bom.gov.au/climate/outlooks/#/overview/summary">Seasonal forecasts</a> give a greater than 60% chance of rainfall above the median for much of eastern Australia from now to the end of March. </p>
<p>If this summer of rain eventuates, it will be welcome news for many farmers in eastern Australia who have had below-median rainfall for three or more years. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/434928/original/file-20211201-21-11pulz4.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of Australia showing eastern coast higher rainfall prediction" src="https://images.theconversation.com/files/434928/original/file-20211201-21-11pulz4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434928/original/file-20211201-21-11pulz4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434928/original/file-20211201-21-11pulz4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434928/original/file-20211201-21-11pulz4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434928/original/file-20211201-21-11pulz4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434928/original/file-20211201-21-11pulz4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434928/original/file-20211201-21-11pulz4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="source" href="http://www.bom.gov.au/jsp/sco/archive/">Bureau of Meteorology</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Farmers usually welcome La Niña with open arms, given plentiful rainfall can boost production and profits. </p>
<p>Still, a boon for one industry can be a burden for another, with heavy or prolonged rainfall able to damage fruit and delicate crops as well as delaying harvests or making them more challenging. Flooding can wash away entire fields and damage roads and other infrastructure. </p>
<p>For the sugar industry, increased rainfall associated with La Niña can mean sugarcane has to be harvested at lower sugar content levels, or be delayed in harvesting. The cane can be knocked over by heavy rain, which makes harvesting difficult and reduces yield, all of which reduce profitability. </p>
<p>For the grains industry, the bumper grain crop predicted for 2021 has <a href="https://www.theguardian.com/australia-news/2021/nov/24/bad-weather-set-to-wipe-billions-off-value-of-australian-crops">already been downgraded</a> in areas like New South Wales due to flooding, with losses expected to be in the billions. </p>
<p>By contrast, the beef industry in Queensland relies on grass, so a La Niña summer with above average rain can increase pasture growth and regeneration as well as cattle weight gain and market prices.</p>
<p>This double-edged sword – too much rain or not enough – is nothing new to Australian farmers. </p>
<p>Understanding how La Niña and other ENSO (El Niño-Southern Oscillation) events impact different regions and industries is critical to take advantage of good years, minimise losses in poor years, and make sound decisions based on the best possible information.</p>
<p>What does that look like? In La Niña years, cattle farmers may decide to move their cattle out of flood prone regions or rest a paddock to allow it to regenerate with the extra rain, which will provide more grass in the following season. </p>
<p>For grain farmers, La Niña means keeping a close eye on both three-month seasonal climate forecasts and the daily weather forecasts to decide if it’s worth the risk to plant a big crop and if they are likely to be able to harvest it before any big rainfall events occur. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/yes-australia-is-a-land-of-flooding-rains-but-climate-change-could-be-making-it-worse-157586">Yes, Australia is a land of flooding rains. But climate change could be making it worse</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/434926/original/file-20211201-28-8vvu5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Storm moving across field of wheat" src="https://images.theconversation.com/files/434926/original/file-20211201-28-8vvu5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434926/original/file-20211201-28-8vvu5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434926/original/file-20211201-28-8vvu5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434926/original/file-20211201-28-8vvu5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434926/original/file-20211201-28-8vvu5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434926/original/file-20211201-28-8vvu5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434926/original/file-20211201-28-8vvu5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">La Niña’s rain can mean promise or threat to farmers.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Can we predict La Niña rainfall?</h2>
<p>La Niña events usually bring average to above average rain to much of Australia’s east. Unfortunately, no two La Niñas occur in the same way. </p>
<p>Because of this variability, it is important for farmers to understand how La Niña events impact their area so that they can plan for likely conditions.</p>
<p>Australia’s east coast climate is heavily influenced by the El Niño-Southern Oscillation (ENSO), a naturally occurring phenomenon centred in the tropical Pacific that consists of three separate phases: La Niña, El Niño, and a neutral or inactive phase. </p>
<p>La Niña years occur around 25% of the time, with El Niño years also at 25%, and neutral years making up 50%. ENSO is not fully predictable, and moves irregularly between these phases. While it is unusual to have back-to-back La Niñas it is not unprecedented.</p>
<p>During these La Niña events, surface water in the central and eastern equatorial Pacific cools and the ocean to the north of Australia tends to warm. </p>
<p>Changes in the ocean drive changes in the atmosphere over the Pacific. Like a rock thrown in a pond, however, this Pacific phenomenon ripples outwards, causing atmospheric changes in places like Australia and Chile. </p>
<p>In Australia, La Niña tends to bring more rain and lower temperatures across much of the country, while we see increases in heavy rain, <a href="https://journals.ametsoc.org/view/journals/apme/55/5/jamc-d-15-0146.1.xml">flooding</a>, and severe tropical cyclones <a href="https://link.springer.com/article/10.1007%2Fs00382-010-0883-2">making landfall</a>. </p>
<p>What does the future hold? While most La Niña events are <a href="https://link.springer.com/article/10.1007/s00382-020-05235-0">projected to produce less rainfall</a> in many regions, projections suggest the wettest La Niña years will tend to be just as wet or wetter that they were in the past. </p>
<p>Australia’s farmers will continue to face the challenges of floods and droughts brought by La Niña and El Niño, but as farmers learn more about these events and how they impact their area and industry, they can become more resilient.</p><img src="https://counter.theconversation.com/content/172511/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chelsea Jarvis receives funding from the Northern Australia Climate Program, which is funded by Meat & Livestock Australia, the Queensland Government, and the University of Southern Queensland. She is affiliated with (a member of) the Australian Meteorological and Oceanographic Society (AMOS). </span></em></p><p class="fine-print"><em><span>Scott Power 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>Many farmers are welcoming an expected summer of La Niña rain, while others have been hit by heavy rain and floodsChelsea Jarvis, Research fellow, University of Southern QueenslandScott Power, Director, Centre for Applied Climate Sciences, University of Southern QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1669202021-09-07T14:35:00Z2021-09-07T14:35:00ZWhat climate change means for southern Ontario and Québec<figure><img src="https://images.theconversation.com/files/418487/original/file-20210830-23-1nq5k21.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C2986%2C2115&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Six-year-old Makai'ryn Terrio, centre, cools off with his brothers as they play in water fountains in Montréal. The city had its hottest August on record. </span> <span class="attribution"><span class="source">The Canadian Press/Graham Hughes</span></span></figcaption></figure><p><a href="https://www.ipcc.ch/languages-2/english/">The Intergovernmental Panel on Climate Change (IPCC)</a> recently released the first report <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">of the sixth assessment cycle</a>. Three others will follow in 2022.</p>
<p>This volume of nearly 4,000 pages has observations on climate change from the past 150 years and projections for climate change up to the end of this century. It is being published 31 years after the <a href="https://www.ipcc.ch/report/ar1/syr/">first assessment cycle</a> and eight years after the <a href="https://www.ipcc.ch/report/ar5/syr/">fifth assessment cycle</a>.</p>
<p>Overall, this latest report does not provide major new insights into climate change or the impact of human activity on it. It does, however, improve our understanding of the human role in climate change and reduce uncertainty about anticipated future impacts. By refining observation methods and improving the accuracy of climate models, the report makes it possible to better define the future impacts on the densely populated areas of southern Ontario and Québec. </p>
<p>We are professors of construction engineering and members of the <a href="http://en.etsmtl.ca/unites-de-recherche/hc3/accueil?lang=en-CA">HC3 — Hydrology Climate Climate Change Laboratory</a> at the École de technologie supérieure de Montréal. The laboratory specializes in the study of hydrology, climate and the impact of climate change on water resources.</p>
<h2>Warming twice as fast</h2>
<p>The average global temperature on Earth has increased 1.1 C since the pre-industrial era. Climate projections predict a temperature increase between 2 C and 3.5 C by the end of this century. This does not take into account the most pessimistic greenhouse gas emissions scenario, which is now considered improbable by most experts. </p>
<hr>
<p>
<em>
<strong>
À lire aussi :
<a href="https://theconversation.com/5-things-to-watch-for-in-the-latest-ipcc-report-on-climate-science-165430">5 things to watch for in the latest IPCC report on climate science</a>
</strong>
</em>
</p>
<hr>
<p>This warming, however, is not geographically uniform. On the whole, southern Ontario and Québec are warming twice as rapidly as the rest of the world. Northern regions are warming three times as fast. </p>
<p>The faster warming is mainly because of the <a href="https://journals.ametsoc.org/view/journals/clim/17/7/1520-0442_2004_017_1550_trosaf_2.0.co_2.xml">ice–albedo feedback loop that is linked to the progressive loss of snow cover</a>. This process means, among other things, that solar radiation, which is normally reflected by the snow, will be absorbed instead. We should therefore anticipate an <a href="https://interactive-atlas.ipcc.ch/regional-information#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">average annual warming of 3 C to 6 C over southern Québec by the end of the century</a>.</p>
<figure class="align-center ">
<img alt="People wading in a pool" src="https://images.theconversation.com/files/417693/original/file-20210824-19241-10fzfdr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/417693/original/file-20210824-19241-10fzfdr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=410&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417693/original/file-20210824-19241-10fzfdr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=410&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417693/original/file-20210824-19241-10fzfdr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=410&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417693/original/file-20210824-19241-10fzfdr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=516&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417693/original/file-20210824-19241-10fzfdr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=516&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417693/original/file-20210824-19241-10fzfdr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=516&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Swimmers bob in the wave pool for the Super Aqua Club in Pointe-Calumet. The Montréal region had its warmest August on record.</span>
<span class="attribution"><span class="source">The Canadian Press/Ryan Remiorz</span></span>
</figcaption>
</figure>
<p>However, the warming will not be evenly distributed across the seasons. Winters will warm significantly more than summer. This means future winters will be 4.5-8 C warmer, with less snow cover and a decrease in spring flooding from melting. </p>
<h2>Changes in extreme events</h2>
<p>Rising temperatures have several other adverse effects, including changes in extreme events. The evidence that these are due to human activity has strengthened since the IPCC’s Fifth Report. It is now well established that human-induced greenhouse gas emissions have led to an overall increase in the frequency and/or intensity of some extreme weather and climate events since the pre-industrial era.</p>
<p>Future projections on a global scale are consistent with this trend. At the regional scale, the magnitude of change varies according to local factors related to changes in land use, such as urbanization or an increase in the area used for agriculture, aerosol emissions into the atmosphere (via industrial activity) and feedback mechanisms, such as ice-albedo feedback.</p>
<hr>
<p>
<em>
<strong>
À lire aussi :
<a href="https://theconversation.com/scientists-moor-ship-in-arctic-ice-for-a-year-to-better-understand-climate-change-123327">Scientists moor ship in Arctic ice for a year to better understand climate change</a>
</strong>
</em>
</p>
<hr>
<p>The report provides little detail about heat waves on a regional scale. That said, for North America, an increase in frequency and intensity is expected by the end of the century. All North American regions will also experience an increase in the intensity and frequency of warm extremes and a decrease in the frequency and intensity of cold extremes.</p>
<h2>Rainfall and flooding</h2>
<p><a href="http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0002122">The projected increases in rainfall extremes</a> will depend on a number of factors, including the duration of rainfall events and their rarity.</p>
<p>Short-duration rainfall extremes that occur infrequently (once every 10 years or more) will become more intense. But a good portion of the existing water management infrastructure, which has a long life span, will adapt poorly to these increases. </p>
<p><a href="https://doi.org/10.5194/egusphere-egu21-10249">Floods from spring snow melt</a> will likely decrease, due to the decrease in snow cover. But there may be a large increase in “flash floods,” caused by extreme summer and autumn rainfall. These are particularly likely to affect small rural catchments and urbanized areas.</p>
<figure class="align-center ">
<img alt="Two men in a dinghy make their way down a flooded street" src="https://images.theconversation.com/files/417688/original/file-20210824-18785-1ucxkb3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/417688/original/file-20210824-18785-1ucxkb3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417688/original/file-20210824-18785-1ucxkb3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417688/original/file-20210824-18785-1ucxkb3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417688/original/file-20210824-18785-1ucxkb3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=497&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417688/original/file-20210824-18785-1ucxkb3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=497&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417688/original/file-20210824-18785-1ucxkb3.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">Firefighters make their way down a flooded street in Ste-Marthe-sur-la-Lac, in May 2019. With climate change, there will be a potentially large increase in flooding from extreme summer and fall rains.</span>
<span class="attribution"><span class="source">The Canadian Press/Ryan Remiorz</span></span>
</figcaption>
</figure>
<p>The IPCC analyzed other indicators, including extreme heat, drought and winter conditions. Using these indicators, a number of conclusions can be drawn for southern Ontario and Québec. By the end of the century, the maximum daily temperature could regularly exceed 35 C during the summer months. </p>
<hr>
<p>
<em>
<strong>
À lire aussi :
<a href="https://theconversation.com/extreme-heat-waves-are-putting-lakes-and-rivers-in-hot-water-this-summer-164227">Extreme heat waves are putting lakes and rivers in hot water this summer</a>
</strong>
</em>
</p>
<hr>
<p>Only the most pessimistic emissions scenario points to an increase in the severity of droughts. For the other scenarios, no clear signals emerge, which means further studies are clearly needed.</p>
<p>The snow season is expected to shorten by the end of the century compared to 1995-2014. A shorter frost season is also expected.</p>
<h2>Adapting to climate change</h2>
<p>Ontario and Québec are warming and are not immune to the effects of anthropogenic climate change.</p>
<p>While efforts to reduce greenhouse gas emissions must be pursued, it is essential to implement adequate adaptation measures to face an uncertain future climate. This first volume of the IPCC’s sixth report mentions the need to strengthen climate services, which is encouraging.</p>
<p>These services are provided by a variety of organizations around the world. They are aimed at providing climate information to support decision-making, by linking science and data production with communication and application by citizens and decision makers. More details will be provided in the second volume of the report.</p><img src="https://counter.theconversation.com/content/166920/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>François Brissette has received funding from the Natural Sciences and Engineering Research Council of Canada, the Ouranos Consortium, the Ministère de l'Économie et de l'Innovation du Québec, and the Ministère de l'Environnement et de la lutte contre les changements climatiques du Québec.</span></em></p><p class="fine-print"><em><span>Annie Poulin holds the Marcelle-Gauvreau Research Chair in the Study of the Impact of Environmental Change on Watershed Hydrology. She has received funding from the Natural Sciences and Engineering Research Council of Canada, the Ouranos Consortium, the Ministère de l'Économie et de l'Innovation du Québec, the Ministère de l'Environnement et de la Lutte contre les changements climatiques du Québec.</span></em></p>Southern Québec is warming twice as rapidly as the rest of the world due to the progressive loss of snow cover. An average annual warming of 3 C to 6 C is expected by the end of the century.François Brissette, Professeur titulaire, groupe de recherche HC3 - Hydrologie Climat & Changements Climatiques, École de technologie supérieure (ÉTS)Annie Poulin, Professeure titulaire, Groupe de recherche HC3 - Hydrologie Climat & Changement Climatique, École de technologie supérieure (ÉTS)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1655902021-08-09T08:04:34Z2021-08-09T08:04:34ZThe water cycle is intensifying as the climate warms, IPCC report warns – that means more intense storms and flooding<figure><img src="https://images.theconversation.com/files/415122/original/file-20210808-124063-1y6zjtl.jpg?ixlib=rb-1.1.0&rect=0%2C87%2C4896%2C3158&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Extreme downpours and flooding like northern England experienced in 2015 can put lives at risk.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/members-of-cleveland-mountain-rescue-and-soldiers-from-2-news-photo/502572800">Ian Forsyth/Getty Images</a></span></figcaption></figure><p><em>Leer <a href="https://theconversation.com/informe-ipcc-por-que-el-cambio-climatico-causa-tormentas-e-inundaciones-mas-intensas-165836">en espanol</a></em></p>
<p>The world watched in July 2021 as extreme rainfall became floods that washed away centuries-old homes in Europe, triggered landslides in Asia and inundated subways in China. More than <a href="https://floodlist.com/asia/world-floods-july-2021">900 people died</a> in the destruction. In North America, the West was battling fires amid an intense drought that is affecting <a href="https://www.npr.org/2021/07/13/1013446314/amid-a-mega-drought-a-water-shortage-will-be-declared-along-the-colorado-river">water</a> and <a href="https://www.sacbee.com/news/california/water-and-drought/article253298613.html">power supplies</a>.</p>
<p><a href="https://news.un.org/en/story/2021/07/1096302">Water-related hazards can be exceptionally destructive</a>, and the impact of climate change on extreme water-related events like these is increasingly evident.</p>
<p>In a <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">new international climate assessment</a> published Aug. 9, 2021, the Intergovernmental Panel on Climate Change warns that the water cycle has been intensifying and will continue to intensify as the planet warms. </p>
<p>The report, which I worked on as a <a href="https://scholar.google.com/citations?user=qWV-WIQAAAAJ&hl=en">lead author</a>, documents an increase in both wet extremes, including more intense rainfall over most regions, and dry extremes, including drying in the Mediterranean, southwestern Australia, southwestern South America, South Africa and western North America. It also shows that both wet and dry extremes will continue to increase with future warming.</p>
<p><iframe id="GynkN" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/GynkN/8/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>Why is the water cycle intensifying?</h2>
<p>Water cycles through the environment, moving between the atmosphere, ocean, land and reservoirs of frozen water. It might fall as rain or snow, seep into the ground, run into a waterway, join the ocean, freeze or evaporate back into the atmosphere. Plants also take up water from the ground and release it through transpiration from their leaves. In recent decades, there has been an overall increase in the rates of precipitation and evaporation.</p>
<figure class="align-center ">
<img alt="An illustration showing how water cycles through precipitation, runoff, groundwater, plants, evaporation and condensation to fall again." src="https://images.theconversation.com/files/415121/original/file-20210808-13508-qxu7md.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415121/original/file-20210808-13508-qxu7md.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=307&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415121/original/file-20210808-13508-qxu7md.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=307&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415121/original/file-20210808-13508-qxu7md.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=307&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415121/original/file-20210808-13508-qxu7md.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=386&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415121/original/file-20210808-13508-qxu7md.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=386&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415121/original/file-20210808-13508-qxu7md.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=386&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Some key points in the water cycle.</span>
<span class="attribution"><a class="source" href="https://gpm.nasa.gov/education/sites/default/files/article_images/Water-Cycle-Art2A.png">NASA</a></span>
</figcaption>
</figure>
<p>A number of factors are intensifying the water cycle, but one of the most important is that warming temperatures raise the upper limit on the amount of moisture in the air. That increases the potential for more rain.</p>
<p>This aspect of climate change is confirmed across <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">all of our lines of evidence</a>: It is expected from basic physics, projected by computer models, and it already shows up in the observational data as a general increase of rainfall intensity with warming temperatures.</p>
<p>Understanding this and other changes in the water cycle is important for more than preparing for disasters. Water is an essential resource for all ecosystems and human societies, and particularly agriculture.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ipcc-climate-report-profound-changes-are-underway-in-earths-oceans-and-ice-a-lead-author-explains-what-the-warnings-mean-165588">IPCC climate report: Profound changes are underway in Earth's oceans and ice – a lead author explains what the warnings mean</a>
</strong>
</em>
</p>
<hr>
<h2>What does this mean for the future?</h2>
<p>An intensifying water cycle means that both wet and dry extremes and the general variability of the water cycle will increase, although not uniformly around the globe. </p>
<p>Rainfall intensity is <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">expected to increase for most land areas</a>, but the largest increases in dryness are expected in the Mediterranean, southwestern South America and western North America.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Maps showing precipitation projections and warming projections at 1.5 and 3 degrees Celsius." src="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.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">Annual average precipitation is projected to increase in many areas as the planet warms, particularly in the higher latitudes.</span>
<span class="attribution"><a class="source" href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">IPCC Sixth Assessment Report</a></span>
</figcaption>
</figure>
<p>Globally, daily extreme precipitation events will likely intensify by about <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">7% for every 1 degree Celsius</a> (1.8 degrees Fahrenheit) that global temperatures rise.</p>
<p>Many other important aspects of the water cycle will also change in addition to extremes as global temperatures increase, the report shows, including reductions in mountain glaciers, decreasing duration of seasonal snow cover, earlier snowmelt and contrasting changes in monsoon rains across different regions, which will impact the water resources of billions of people.</p>
<h2>What can be done?</h2>
<p>One common theme across these aspects of the water cycle is that <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">higher greenhouse gas emissions lead to bigger impacts</a>. </p>
<p>The IPCC does not make policy recommendations. Instead, it provides the scientific information needed to carefully evaluate policy choices. The results show what the implications of different choices are likely to be.</p>
<p>One thing the <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">scientific evidence in the report</a> clearly tells world leaders is that limiting global warming to the Paris Agreement target of 1.5 C (2.7 F) will require immediate, rapid and large-scale reductions in greenhouse gas emissions.</p>
<p>Regardless of any specific target, it is clear that the severity of climate change impacts are closely linked to greenhouse gas emissions: Reducing emissions will reduce impacts. Every fraction of a degree matters.</p>
<p>[<em>Understand new developments in science, health and technology, each week.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-understand">Subscribe to The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/165590/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mathew Barlow received travel funding from the US government to attend three IPCC lead author meetings.</span></em></p>Water-related hazards are exceptionally destructive, and the impact of climate change on extreme water-related events is increasingly evident, a lead author of the new report warns.Mathew Barlow, Professor of Climate Science, UMass LowellLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1575862021-03-23T18:52:57Z2021-03-23T18:52:57ZYes, Australia is a land of flooding rains. But climate change could be making it worse<figure><img src="https://images.theconversation.com/files/391062/original/file-20210323-23-1rjbwxk.jpg?ixlib=rb-1.1.0&rect=0%2C75%2C906%2C492&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Etching of the 1867 flood in the Hawkesbury-Nepean Valley, depicting the Eather family.</span> <span class="attribution"><span class="source"> illustrated Sydney News/author provided</span></span></figcaption></figure><p>Over the past three years, I’ve been working on the <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">forthcoming report</a> by the United Nations’ <a href="https://www.ipcc.ch/">Intergovernmental Panel on Climate Change</a>. I’m a climate scientist who contributed to the chapter on global <a href="https://www.ipcc.ch/site/assets/uploads/2018/09/AR6_WGI_outlines_P46.pdf">water cycle changes</a>. It’s concerning to think some theoretical impacts described in this report may be coming to life – yet again – in Australia.</p>
<p>The recent flooding in New South Wales is consistent with what we might expect as climate change continues.</p>
<p>Australia’s natural rainfall patterns are highly variable. This means the influence climate change has on any single weather event is difficult to determine; the signal is buried in the background of a lot of climatic “noise”.</p>
<p>But as our planet warms, the water-holding capacity of the lower atmosphere increases <a href="https://nyaspubs.onlinelibrary.wiley.com/doi/10.1111/nyas.14337">by around 7% for every 1°C of warming</a>. This can cause heavier rainfall, which in turn increases flood risk.</p>
<p>The oceans are also warming, especially at the surface. This drives up both evaporation rates and the transport of moisture into weather systems. This makes wet seasons and wet events wetter than usual.</p>
<p>So while Australia has always experienced floods, disasters like the one unfolding in NSW are likely to become more frequent and intense as climate change continues. </p>
<figure class="align-center ">
<img alt="People watch swollen river" src="https://images.theconversation.com/files/391064/original/file-20210323-17-govg24.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/391064/original/file-20210323-17-govg24.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/391064/original/file-20210323-17-govg24.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/391064/original/file-20210323-17-govg24.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/391064/original/file-20210323-17-govg24.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/391064/original/file-20210323-17-govg24.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/391064/original/file-20210323-17-govg24.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">Flooding is likely to become more severe as the planet warms.</span>
<span class="attribution"><span class="source">AAP</span></span>
</figcaption>
</figure>
<h2>Understanding the basics</h2>
<p>To understand how a warming world is influencing the water cycle, it’s helpful to return to the theory.</p>
<p>From year to year, Australia’s climate is subject to natural variability generated by the surrounding <a href="http://www.bom.gov.au/climate/about/?bookmark=enso">Pacific</a>, <a href="http://www.bom.gov.au/climate/iod/#tabs=Indian-Ocean-climate-drivers">Indian</a> and <a href="http://www.bom.gov.au/climate/about/?bookmark=sam">Southern</a> oceans. The dominant drivers for a given year set up the background climate conditions that influence rainfall and temperature.</p>
<p>It is a combination of these natural climate drivers that makes Australia the land of <a href="https://www.mup.com.au/books/sunburnt-country-paperback-softback">drought and flooding rains</a>.</p>
<p>However, Australia’s climate variability is no longer influenced by natural factors alone. Australia’s climate has warmed by <a href="http://www.bom.gov.au/state-of-the-climate/australias-changing-climate.shtml">1.4°C since national records began in 1910</a>, with most of the warming occurring since 1970. Human-caused greenhouse emissions have influenced Australian temperatures in our region <a href="https://journals.ametsoc.org/view/journals/clim/18/3/jcli-3265.1.xml">since 1950</a>.</p>
<p>This warming trend influences the background conditions under which both extremes of the rainfall cycle will operate as the planet continues to warm. A warmer atmosphere can hold more moisture (higher water vapour content), which can lead to more extreme rainfall events.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/390812/original/file-20210322-15-lyawn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/390812/original/file-20210322-15-lyawn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/390812/original/file-20210322-15-lyawn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/390812/original/file-20210322-15-lyawn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/390812/original/file-20210322-15-lyawn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=479&fit=crop&dpr=1 754w, https://images.theconversation.com/files/390812/original/file-20210322-15-lyawn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=479&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/390812/original/file-20210322-15-lyawn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=479&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A warmer atmosphere can hold more moisture which can lead to more extreme rainfall events.</span>
<span class="attribution"><span class="source">Climate Council</span></span>
</figcaption>
</figure>
<p>Since the <a href="http://www.bom.gov.au/climate/influences/graphs/">winter of 2020</a>, Australia has been influenced by the La Niña phase of the El Niño–Southern Oscillation (<a href="http://www.bom.gov.au/climate/about/?bookmark=enso">ENSO</a>). Historically, sustained <a href="http://www.bom.gov.au/climate/enso/lnlist/">La Niña conditions</a>, sometimes with the help of a <a href="http://www.bom.gov.au/climate/iod/#tabs=Negative-IOD-impacts">warmer than average Indian Ocean</a>, have set the scene for severe flooding in eastern Australia.</p>
<p>During these events, easterly winds intensify and oceans around Australia warm. This is associated with the <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/walker-circulation">Walker Circulation</a> – a giant seesaw of atmospheric pressure that influences the distribution of warm ocean waters across the Pacific Ocean. </p>
<p>The last La Niña occurred in <a href="http://www.bom.gov.au/climate/enso/lnlist/">2010–2012</a>. It led to widespread flooding across eastern Australia, with particularly devastating effects in <a href="https://knowledge.aidr.org.au/resources/flood-queensland-2010-2011/">Queensland</a>. The event caused the <a href="http://www.bom.gov.au/climate/enso/history/ln-2010-12/index.shtml">wettest two-year period</a> in the Australian rainfall record, ending the 1997–2009 <a href="http://www.bom.gov.au/climate/updates/articles/a010-southern-rainfall-decline.shtml">Millennium Drought</a>.</p>
<p>Oceanographers from UNSW studied the exceptional event. <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL065948">They demonstrated</a> how a warmer ocean increased the likelihood of extreme rain during that event, primarily through increased transport of moist air along the coast. </p>
<p>Their analysis highlighted how long‐term ocean warming can modify rain-producing systems, increasing the probability of extreme rainfall during La Niña events.</p>
<p>It is important to point out that changes in large-scale atmospheric circulation patterns are still not as well understood as fundamental changes in thermodynamics. However, because regional rainfall changes will be influenced by <a href="https://www.nature.com/articles/nclimate2976">both factors</a>, it will take researchers time to tease everything out.</p>
<h2>So what about climate change?</h2>
<p>The theoretical changes to the global water cycle are <a href="https://nyaspubs.onlinelibrary.wiley.com/doi/10.1111/nyas.14337">well understood</a>. However, determining the contribution of natural and human influences on climate variability and extremes – known as “<a href="https://unfccc.int/files/adaptation/workstreams/loss_and_damage/application/pdf/attributingextremeevents.pdf">attribution</a>” – is still an emerging science. </p>
<p>More studies are needed to distinguish natural or “background” rainfall variability from recent human-caused changes to the water cycle. This is particularly the case in a country like Australia, which has very high yearly rainfall variability. This contrasts with some regions of the Northern Hemisphere with less variable rainfall, where a clear climate change signal has <a href="https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter10_FINAL.pdf">already emerged</a>.</p>
<p>Right now, La Niña conditions are <a href="http://www.bom.gov.au/climate/enso/#tabs=Overview">decaying</a> in the Pacific Ocean. As expected, the 2020–2021 La Niña has brought above-average rainfall to much of eastern Australia. This helped ease the severe drought conditions across eastern Australia since 2017, particularly in NSW.</p>
<figure class="align-center ">
<img alt="NSW rainfall total, week ending March 22, 2021" src="https://images.theconversation.com/files/391056/original/file-20210323-13-1bnedb7.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/391056/original/file-20210323-13-1bnedb7.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=370&fit=crop&dpr=1 600w, https://images.theconversation.com/files/391056/original/file-20210323-13-1bnedb7.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=370&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/391056/original/file-20210323-13-1bnedb7.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=370&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/391056/original/file-20210323-13-1bnedb7.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=465&fit=crop&dpr=1 754w, https://images.theconversation.com/files/391056/original/file-20210323-13-1bnedb7.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=465&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/391056/original/file-20210323-13-1bnedb7.gif?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">
<figcaption>
<span class="caption">NSW rainfall totals for the week ending March 22, 2021.</span>
<span class="attribution"><span class="source">Bureau of Meteorology</span></span>
</figcaption>
</figure>
<p>What’s interesting about the 2020–2021 La Niña is that it was <a href="http://www.bom.gov.au/climate/influences/graphs/">weak</a> compared with historical events. The relationship between La Niña and rainfall is generally weaker in coastal NSW than further inland. However, it’s concerning that this weak La Niña caused flooding comparable to the iconic floods of the <a href="http://www.bom.gov.au/climate/enso/lnlist/">1950s and 1970s</a>. </p>
<p>The rainfall totals for the current floods are yet to be <a href="http://www.bom.gov.au/climate/current/statements/">analysed</a>. However, early figures reveal the enormity of the downpours. For example, over the week to March 23, the town of Comboyne, southwest of Port Macquarie, recorded an extraordinary 935mm of rainfall. This included three successive days with more than 200mm.</p>
<p>The NSW coast is no stranger to extreme rainfall – there have been five events in the past decade with daily totals exceeding 400mm. However, the current event is unusual because of its duration and geographic extent. </p>
<p>It’s also worth noting the current extreme rainfall in NSW was associated with a <a href="http://media.bom.gov.au/social/blog/2140/know-your-lows-east-coast-lows-and-lookalikes/">coastal trough</a>, not an <a href="http://www.bom.gov.au/weather-services/severe-weather-knowledge-centre/eastcoastlows.shtml">East Coast Low</a>. Many of the region’s <a href="https://doi.org/10.1007/s00382-019-04836-8">torrential rainfall events</a> in the past have resulted from East Coast Lows, although their rainfall is normally more localised than has been the case in this widespread event.</p>
<p>Remember that as the air warms, its water-holding capacity increases, particularly over the oceans. Current ocean temperatures around eastern and northern Australia are about 1°C warmer than the long-term average, and closer to 1.5°C warmer than average off the NSW coast. These warmer conditions are likely to be fuelling the systems driving the extreme rainfall and associated flooding in NSW.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/391089/original/file-20210323-20-qbc3i0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/391089/original/file-20210323-20-qbc3i0.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=721&fit=crop&dpr=1 600w, https://images.theconversation.com/files/391089/original/file-20210323-20-qbc3i0.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=721&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/391089/original/file-20210323-20-qbc3i0.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=721&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/391089/original/file-20210323-20-qbc3i0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=906&fit=crop&dpr=1 754w, https://images.theconversation.com/files/391089/original/file-20210323-20-qbc3i0.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=906&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/391089/original/file-20210323-20-qbc3i0.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=906&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sea surface temperature anomalies along the NSW coast.</span>
<span class="attribution"><span class="source">Bureau of Meteorology</span></span>
</figcaption>
</figure>
<h2>A nation exposed</h2>
<p>Weather and climate are not the only influences on extreme flood events. Others factors include the shape and size of water catchments, the presence of hard surfaces in urban areas (which cant’t absorb water), and the density of human settlement in <a href="https://www.theguardian.com/commentisfree/2021/mar/22/increased-urban-density-in-australia-could-make-future-floods-worse">flood-prone areas</a>.</p>
<p>The Hawkesbury–Nepean region in Western Sydney, currently experiencing major flooding, is a prime example. Five major tributaries, including the Warragamba and Nepean Rivers, flow into this extensively urbanised valley.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/28SN9KixO2I?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Improving our understanding of historical weather data may <a href="https://nyaspubs.onlinelibrary.wiley.com/doi/abs/10.1111/nyas.13966">help improve</a> future climate change risk assessment. For example, past floods in the Hawkesbury–Nepean have been a lot worse than the current disaster. In 1867, the Hawkesbury River at Windsor reached <a href="https://www.ses.nsw.gov.au/news/all-news/2017/reflecting-on-the-record-1867-hawkesbury-nepean-flood/">19.7 metres</a> above normal, and in 1961 peaked at <a href="http://insw.com/media/1393/insw-factsheet-flooding-in-the-hawkesbury-nepean-valley.pdf">14.5 metres</a>. This is worse than the 13.12 metres above normal recorded at <a href="http://www.bom.gov.au/cgi-bin/wrap_fwo.pl?IDN60143.html#Hawkesbury_River_to_Windsor">Freemans Reach on March 23</a>.</p>
<p>It’s sobering to think the Hawkesbury River once peaked 6 metres higher than what we’re seeing right now. Imagine the potential future flooding caused by an East Coast Low during strong La Niña conditions.</p>
<p>It will take time before scientists can provide a detailed analysis of the 2020–2021 La Niña event. But it’s crystal clear that Australia is very exposed to damage caused by extreme rainfall. Our theoretical understanding of water cycle changes tells us these events will only become more intense as our planet continues to warm.</p><img src="https://counter.theconversation.com/content/157586/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Joelle Gergis has received funding from the Australian Research Council in the past. She currently receives funding from the Australian National University and the Australian Government's Department of Industry, Science, Energy and Resources.</span></em></p>The NSW floods are a textbook example of the theoretical impacts we can expect on Australian rainfall as climate change continues.Joelle Gergis, Senior Lecturer in Climate Science, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1469802020-11-02T13:24:50Z2020-11-02T13:24:50ZA few heavy storms cause a big chunk of nitrogen pollution from Midwest farms<figure><img src="https://images.theconversation.com/files/364813/original/file-20201021-23-1sop9qc.jpg?ixlib=rb-1.1.0&rect=26%2C0%2C3000%2C1998&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Corn plants in a flooded field near Emden, Ill., May 29, 2019.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.ie/detail/news-photo/corn-grows-in-a-saturated-farm-field-on-may-29-2019-near-news-photo/1152539969?adppopup=true">Scott Olson/Getty Images</a></span></figcaption></figure><p>Some effects of extreme weather are visible – like <a href="https://www.marketwatch.com/story/devastating-august-derecho-prompts-usda-to-cut-iowa-corn-acres-by-550-000-11599849936">half a million acres of flattened corn in Iowa</a> left behind after a <a href="https://theconversation.com/what-is-a-derecho-an-atmospheric-scientist-explains-these-rare-but-dangerous-storm-systems-140319">derecho</a> that hit the Midwestern United States on Aug. 10. </p>
<p>Other effects are harder to measure, but can be just as harmful. One example is agricultural nitrogen runoff from farmlands in the Mississippi River Basin. It mainly comes from fertilizer that farmers apply to <a href="https://pubs.usgs.gov/fs/old.2003/fs-105-03/">millions of acres of crops</a>. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/366499/original/file-20201029-19-1c171bd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of Mississippi River basin" src="https://images.theconversation.com/files/366499/original/file-20201029-19-1c171bd.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/366499/original/file-20201029-19-1c171bd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=550&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366499/original/file-20201029-19-1c171bd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=550&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366499/original/file-20201029-19-1c171bd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=550&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366499/original/file-20201029-19-1c171bd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=691&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366499/original/file-20201029-19-1c171bd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=691&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366499/original/file-20201029-19-1c171bd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=691&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 Mississippi River Basin covers over 1.245 million square miles across 32 U.S. states and two Canadian provinces.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Mississippi_River_System#/media/File:Mississippiriver-new-01.png">Shannon1/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Plants can’t use all of the nitrogen in fertilizer because fertilizers are usually applied in excess. This excess can wash off farm fields into local rivers and lakes, degrading water quality and <a href="https://theconversation.com/how-your-diet-contributes-to-nutrient-pollution-and-dead-zones-in-lakes-and-bays-118902">stimulating algae blooms</a>. Traveling down the Mississippi River, it contributes to the yearly formation of a <a href="https://coastalscience.noaa.gov/news/large-dead-zone-measured-in-gulf-of-mexico/">dead zone in the northern Gulf of Mexico</a>, covering several thousand square miles; oxygen levels there are so low that fish and shellfish cannot survive. </p>
<p>Excess nitrogen in drinking water also <a href="https://www.wsj.com/articles/farms-more-productive-than-ever-are-poisoning-drinking-water-in-rural-america-11547826031">threatens public health</a>. Ingesting high levels of nitrate, a nitrogen compound, can <a href="https://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=1186&tid=258">reduce red blood cells’ ability to transport oxygen</a>, a condition that is especially dangerous for infants. </p>
<p>My work as a <a href="https://scholar.google.com/citations?user=VI_Lb-YAAAAJ&hl=en">quantitative ecologist</a> examines how ecosystems respond to external factors such as adding nitrogen. In a recently published study, I worked with colleagues to quantify nitrogen runoff from land into rivers and streams. We found that infrequent but heavy rainfall events account for <a href="https://doi.org/10.1038/s43247-020-00020-7">one-third of annual total runoff and nitrogen leaching from soils</a> across the Mississippi Basin. This tells us that managing nitrogen is likely to be more challenging if climate change continues to make heavy rains more frequent.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/OQFjmWGONCA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">To use nitrogen fertilizer efficiently, farmers need to consider factors including yield goals, soil quality, chemistry and weather.</span></figcaption>
</figure>
<h2>Too much of a good thing</h2>
<p>Plants can’t grow without nitrogen, but using too much or applying it improperly can cause problems. In the U.S. Midwest, one of the <a href="https://pubs.usgs.gov/fs/fs155-99/fs155-99.html">most intensively farmed areas in the world</a>, farmers have added <a href="https://doi.org/10.5194/essd-10-969-2018">large amounts of synthetic nitrogen fertilizer</a> to the land to boost crop yields. </p>
<p>Long-term monitoring data from river gauges shows large year-to-year variations in the quantity of nitrogen that flows down from the Mississippi River Basin into the Gulf of Mexico. Yearly changes in farmers’ fertilizer use are not large enough to explain these fluctuations.</p>
<p>Studies show that annual total precipitation is a <a href="https://carnegiescience.edu/news/projected-precipitation-increases-are-bad-news-water-quality">significant factor in these changes</a>. But we know less about the role of daily rainfall – particularly heavy rains – in mobilizing and transporting nitrogen. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/366164/original/file-20201028-19-1obdcnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graph showing nitrogen runoff from Midwest states to the Gulf of Mexico, 1980-2017." src="https://images.theconversation.com/files/366164/original/file-20201028-19-1obdcnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/366164/original/file-20201028-19-1obdcnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366164/original/file-20201028-19-1obdcnf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366164/original/file-20201028-19-1obdcnf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366164/original/file-20201028-19-1obdcnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=479&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366164/original/file-20201028-19-1obdcnf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=479&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366164/original/file-20201028-19-1obdcnf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=479&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Stream gauge measurements show that the amount of dissolved inorganic nitrogen (DIN) moving from Mississippi River Basin states to the Gulf of Mexico fluctuates dramatically from year to year. Heavy rainfalls can produce higher nitrogen levels.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1038/s43247-020-00020-7">Modified from Lu et al., 2020</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Heavy rains have an outsized impact</h2>
<p>My collaborators and I wanted to assess the impacts of extreme rainfall events in the Midwest. In this region, many cropped fields are laced with buried networks of drainage channels, known locally as <a href="https://en.wikipedia.org/wiki/Tile_drainage">tile drainage</a>. These pipelines are designed to move excess moisture out of fields. But they can also channel large surges of water and nutrients into rivers and streams after heavy rainfalls.</p>
<p>It is challenging to determine how individual rainfall events affect nitrogen leaching and movement within a <a href="https://www.britannica.com/science/drainage-basin">drainage basin</a>. Rain happens here and there, so it’s hard to distinguish a single storm’s impact from river gauge monitoring data. Rainfall events also vary a lot by season and intensity. </p>
<p>Our study used a well-tested model to quantify how much nitrogen is washed out by each rainfall event, as well as total nitrogen delivered to the Gulf of Mexico. We looked closely at heavy rainfall events, which we defined as the top 10% of historical daily precipitation amounts for any location in a given month. </p>
<p>Climate records show that over the past 20 years, a growing share of annual precipitation has come in heavy rainfall events across two-thirds of the Mississippi River Basin’s land area. The region that receives a total of more than 15.7 inches (400 millimeters) of heavy rain per year has expanded from areas in Louisiana and Arkansas northward to Corn Belt states like Illinois and Indiana, where nitrogen fertilizer is heavily used.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/366496/original/file-20201029-21-1uua7k7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="U.S. map showing more precipitation falling during very heavy events" src="https://images.theconversation.com/files/366496/original/file-20201029-21-1uua7k7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/366496/original/file-20201029-21-1uua7k7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=541&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366496/original/file-20201029-21-1uua7k7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=541&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366496/original/file-20201029-21-1uua7k7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=541&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366496/original/file-20201029-21-1uua7k7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=679&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366496/original/file-20201029-21-1uua7k7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=679&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366496/original/file-20201029-21-1uua7k7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=679&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Percentage increases in the amount of precipitation falling in very heavy events (defined as the heaviest 1% of all daily events) from 1958 to 2012.</span>
<span class="attribution"><a class="source" href="https://nca2014.globalchange.gov/report/our-changing-climate/heavy-downpours-increasing#:~:text=National%20Climate%20Assessment%20Home&text=Heavy%20downpours%20are%20increasing%20nationally,Explore%20extreme%20precipitation.">Globalchange.gov</a></span>
</figcaption>
</figure>
<p>We found that one-third of annual total runoff and nitrogen leaching loss come from heavy rainfall events, which happen on only about nine days per year on average across the basin. Nearly half to three-quarters of heavy rainfall in the basin occurs in spring and summer, with a monthly peak in May. </p>
<p>This timing coincides with the planting and seed germinating stages of corn, when the plants are using <a href="http://nmsp.cals.cornell.edu/publications/factsheets/factsheet98.pdf">minimal amounts of nitrogen</a>. We wondered whether changing when and how farmers apply fertilizer could reduce nitrogen runoff.</p>
<h2>When to fertilize</h2>
<p>When during the year to apply fertilizer is a long-standing question in both <a href="https://theconversation.com/farmers-of-the-future-will-utilize-drones-robots-and-gps-37739">precision agriculture</a> and environmental science. Midwest farmers apply over 90% of nitrogen fertilizer before crops germinate in springtime and after harvesting. This means that a fair amount of available nitrogen accumulates in the soil before crops start taking it up. When heavy rainfalls occur, it is likely to be washed out. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1318214328403767303"}"></div></p>
<p>We set up modeling experiments to test whether postponing fertilizer application could make the water running off of farmlands cleaner. In our alternative fertilizer management scenario, we assumed fertilizer was applied only twice, after crops developed. We expected this would reduce the amount of unused nitrogen accumulating in soils.</p>
<p>Our results predicted that this modification could reduce nitrogen loading to the Gulf of Mexico by up to 16%. This would be a significant step toward goals set by the U.S. Environmental Protection Agency, which is working with states to reduce nutrient loads entering the Gulf of Mexico by <a href="https://archive.epa.gov/epa/newsreleases/states-develop-new-strategies-reduce-nutrient-levels-mississippi-river-gulf-mexico.html">20% by 2025 and 45% by 2035</a>. </p>
<p>However, even under the postponed fertilizer application scenario, we still found the frequent heavy rains in the recent decade could enhance nitrogen loss during summer and early fall. Scientists predict that if climate change continues at its current rate, it will cause <a href="https://nca2014.globalchange.gov/highlights/regions/midwest#intro-section-2">more extreme rainfall events in the Midwest</a>, which, we think, would reduce environmental benefits from alternative nitrogen management practices. </p>
<p>Reducing the amount of nitrogen that escapes from land into water bodies while maintaining food production is a significant challenge. Our study complements the well-known <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/ia/technical/ecoscience/nutrient/nrcs142p2_008196/">4R concept</a> for managing nutrients: Using the right fertilizer product, at the right rate, at the right time, and in the right place. To get that timing right, our research shows that along with crop nitrogen demand, farmers should also consider the occurrence of heavy rainfall.</p>
<p>[<em>Get our best science, health and technology stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-best">Sign up for The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/146980/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chaoqun Lu receives funding from the National Science Foundation, Iowa State University, and the Iowa Nutrient Research Center.</span></em></p>New research shows that one-third of yearly nitrogen runoff from Midwest farms to the Gulf of Mexico occurs during a few heavy rainstorms. New fertilizing schedules could reduce nitrogen pollution.Chaoqun Lu, Assistant Professor of Ecology, Evolution and Organismal Biology, Iowa State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1447022020-08-24T20:04:46Z2020-08-24T20:04:46ZYes, it’s been raining a lot – but that doesn’t mean Australia’s drought has broken<figure><img src="https://images.theconversation.com/files/354274/original/file-20200823-18-18haf3n.jpeg?ixlib=rb-1.1.0&rect=14%2C0%2C3149%2C2352&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Peter Lorrimer/AAP</span></span></figcaption></figure><p>Heavy rain in parts of Australia in recent months has <a href="https://www.abc.net.au/radionational/programs/breakfast/states-call-for-radical-change-to-murray-darling-basin-plan/12564276">raised</a> <a href="https://www.sbs.com.au/news/the-drought-broke-just-in-time-for-australia-s-farmers-now-they-re-battling-coronavirus">hopes</a> Australia’s protracted drought is finally over. But determining whether a region has recovered from drought is a complex undertaking. </p>
<p>For example, a drought-stricken area may get enough rain that farmers can plant a viable crop, but that same rain may not affect major water storages. We’ve seen that in southern Queensland, where water restrictions <a href="https://www.sdrc.qld.gov.au/living-here/water-wastewater/water-restrictions/faqs-water-restrictions">remain in place</a> despite recent rain.</p>
<p>And from a social, economic and environmental perspective, one great season of rain does not usually make up for a run of bad seasons. </p>
<p>So today, in <a href="https://www.worldwaterweek.org">World Water Week</a>, we consider the effect of this year’s rain. The upshot is that most drought-ravaged areas still need sustained, above-average rain before streamflow and water storage levels return to average. And in other parts of Australia where little rain has fallen in 2020, unfortunately drought areas have expanded.</p>
<figure class="align-center ">
<img alt="Rainbow over letterboxes in a rural setting" src="https://images.theconversation.com/files/354273/original/file-20200823-18-1o4unsc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/354273/original/file-20200823-18-1o4unsc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/354273/original/file-20200823-18-1o4unsc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/354273/original/file-20200823-18-1o4unsc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/354273/original/file-20200823-18-1o4unsc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/354273/original/file-20200823-18-1o4unsc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/354273/original/file-20200823-18-1o4unsc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">2020 has brought rain to Australia’s east, but more is needed to break the drought.</span>
<span class="attribution"><span class="source">Peter Lorrimer/AAP</span></span>
</figcaption>
</figure>
<h2>Three years with little rain</h2>
<p>The Bureau of Meteorology is not responsible for declaring whether a region is or isn’t in drought – that’s a state government responsibility. But we do analyse rainfall and water data, which indicate whether a region is recovering. </p>
<p>In the three years from January 2017 to the end of 2019, rainfall for much of Australia was greatly reduced – with both 2018 and 2019 especially dry. Rainfall deficiencies were most severe in the northern Murray–Darling Basin; the period was the <a href="http://www.bom.gov.au/climate/current/annual/aus/2019/">driest and hottest</a> on record for the basin as a whole. </p>
<p>These record warm temperatures exacerbated dry conditions, at times rapidly drying soils in only a matter of months. This led to periods in 2017 and 2019 that researchers have <a href="https://www.abc.net.au/news/2019-07-20/how-flash-droughts-strike-fast-and-hard/11320654">termed</a> “flash drought”.</p>
<figure class="align-center ">
<img alt="Rainfall deciles from January 2017 to December 2019" src="https://images.theconversation.com/files/354283/original/file-20200824-24-1ysv8cj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/354283/original/file-20200824-24-1ysv8cj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=412&fit=crop&dpr=1 600w, https://images.theconversation.com/files/354283/original/file-20200824-24-1ysv8cj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=412&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/354283/original/file-20200824-24-1ysv8cj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=412&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/354283/original/file-20200824-24-1ysv8cj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=518&fit=crop&dpr=1 754w, https://images.theconversation.com/files/354283/original/file-20200824-24-1ysv8cj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=518&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/354283/original/file-20200824-24-1ysv8cj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=518&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rainfall deciles from January 2017 to December 2019 showing the depth of longer-term rainfall deficiencies over large areas.</span>
<span class="attribution"><span class="source">BOM</span></span>
</figcaption>
</figure>
<h2>2020: partial recovery in the east</h2>
<p>Since January this year, above-average rainfall has fallen on some parts of eastern Australia, particularly across some of the worst drought-affected areas of central and western New South Wales and southwest Queensland. In February, much of eastern NSW experienced heavy rain, while there were more widespread and consistent falls through many parts of southeastern Australia from February to April. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/its-official-the-last-five-years-were-the-warmest-ever-recorded-133056">It's official: the last five years were the warmest ever recorded</a>
</strong>
</em>
</p>
<hr>
<p>But some areas have largely missed out on recent rains. Southern South Australia and southwest Western Australia have received below-average rainfall in 2020, continuing the dry conditions of 2019. Drought areas in parts of the southern coast of Western Australia and southwestern South Australia have expanded this year, and the regions may face a difficult spring and summer.</p>
<figure class="align-center ">
<img alt="Graph showing the impact of recent rain across Australia" src="https://images.theconversation.com/files/354284/original/file-20200824-16-j1n1h4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/354284/original/file-20200824-16-j1n1h4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=412&fit=crop&dpr=1 600w, https://images.theconversation.com/files/354284/original/file-20200824-16-j1n1h4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=412&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/354284/original/file-20200824-16-j1n1h4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=412&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/354284/original/file-20200824-16-j1n1h4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=518&fit=crop&dpr=1 754w, https://images.theconversation.com/files/354284/original/file-20200824-16-j1n1h4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=518&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/354284/original/file-20200824-16-j1n1h4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=518&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rainfall deciles from January 1, 2020 to July 31, 2020, showing the impact of recent rainfall across Australia.</span>
<span class="attribution"><span class="source">BOM</span></span>
</figcaption>
</figure>
<h2>Wetter soils, better crops</h2>
<p>Eastern Australia’s recent rain has helped replenish soil moisture levels, enabling favourable crop and pasture growth in many areas. For August to date, soil moisture is above average across eastern coastal areas and mostly average to above average in Murray–Darling Basin catchments. </p>
<p>This increase in soil moisture is a very positive foundation – catchments are now primed to produce runoff and inflows to water storages if there is significant rainfall in spring. </p>
<p>But soil moisture levels are below average for August across much of southwestern Australia, southern parts of South Australia, northern Tasmania, northern parts of the Northern Territory and parts of central Queensland. </p>
<h2>Not all dams have filled up</h2>
<p>In Sydney, water storage levels had been declining since July 2016. This resulted in level 2 water restrictions introduced in December 2019 and Sydney’s desalination plant operating at full capacity. But heavy rain in February and August this year filled Warragamba Dam to capacity, further increasing Sydney’s storage levels. </p>
<figure class="align-center ">
<img alt="Total Sydney storage as at 18 August 2020" src="https://images.theconversation.com/files/354301/original/file-20200824-16-19fiq72.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/354301/original/file-20200824-16-19fiq72.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/354301/original/file-20200824-16-19fiq72.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/354301/original/file-20200824-16-19fiq72.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/354301/original/file-20200824-16-19fiq72.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/354301/original/file-20200824-16-19fiq72.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/354301/original/file-20200824-16-19fiq72.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Total storage as at 18 August 2020 (% of total capacity) compared to the last ten years for Sydney storages.</span>
<span class="attribution"><span class="source">BOM</span></span>
</figcaption>
</figure>
<p>In contrast to Sydney, major storage levels in the northern Murray–Darling Basin remain low, at only 21% of total capacity despite rainfall in recent months. Unlike the significant and rapid recovery of these storages in 2010 and 2016, the current rate of recovery is slow. Significant follow-up rain is needed to replenish these northern basin water storages.</p>
<figure class="align-center ">
<img alt="Northern Murray–Darling Basin: total storage as at 31 July" src="https://images.theconversation.com/files/354286/original/file-20200824-20-14atin9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/354286/original/file-20200824-20-14atin9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/354286/original/file-20200824-20-14atin9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/354286/original/file-20200824-20-14atin9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/354286/original/file-20200824-20-14atin9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/354286/original/file-20200824-20-14atin9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/354286/original/file-20200824-20-14atin9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Total storage as at 31 July (% of total capacity) compared to the last ten years for the northern Murray–Darling Basin.</span>
<span class="attribution"><span class="source">BOM</span></span>
</figcaption>
</figure>
<p>In the west, while Perth’s water supply system relies on desalinated water and groundwater to supplement its storages, the dry conditions are reflected in the Harvey rural supply system south of Perth. It needs a further 100,000 megalitres to replenish the drawdown of the past two years.</p>
<figure class="align-center ">
<img alt="Total storage as at July 31 for the Harvey system" src="https://images.theconversation.com/files/354287/original/file-20200824-22-13rk8ax.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/354287/original/file-20200824-22-13rk8ax.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/354287/original/file-20200824-22-13rk8ax.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/354287/original/file-20200824-22-13rk8ax.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/354287/original/file-20200824-22-13rk8ax.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/354287/original/file-20200824-22-13rk8ax.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/354287/original/file-20200824-22-13rk8ax.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Total storage as at July 31 (% of total capacity) compared to the last ten years for the Harvey system.</span>
<span class="attribution"><span class="source">BOM</span></span>
</figcaption>
</figure>
<h2>So, is the drought over?</h2>
<p>For many regions in eastern Australia, rainfall in 2020 has eased drought conditions by wetting soils and helping fill dams on farms. But most drought-affected areas still need sustained above average rainfall for streamflow and water storages to increase to at least average levels. </p>
<p>Recently the Bureau of Meteorology <a href="http://www.bom.gov.au/climate/enso/outlook/">raised</a> its El Niño–Southern Oscillation (ENSO) status to La Niña ALERT. This means there is three times the normal likelihood of a La Niña weather pattern in 2020. La Niña events typically result in wetter than average conditions over Australia in winter and spring. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-city-by-city-guide-to-how-water-supplies-fared-in-australias-summer-of-extremes-132669">A city-by-city guide to how water supplies fared in Australia's summer of extremes</a>
</strong>
</em>
</p>
<hr>
<p>Separately, warmer conditions in the eastern Indian Ocean may also boost the chance of a wetter end to the year. </p>
<p>The bureau’s latest outlook indicates the eastern two-thirds of Australia is very likely to receive above average rainfall in coming months. However, southwest Western Australia is less likely to have above average rainfall. </p>
<p>The bureau will provide further updates on current rainfall deficiencies through regular reports such as its monthly Drought Statement and weekly rainfall tracker.</p>
<hr>
<p><em>The bureau’s <a href="http://www.bom.gov.au/climate/drought/knowledge-centre/">Drought Knowledge Centre</a> provides information about drought in your area. <a href="http://www.bom.gov.au/water/nrtwreporting/">Water Reporting Summaries</a> for the Murray–Darling Basin provide an overview of water currently in storage and commitments made for this water to different users, including the environment. The <a href="http://www.bom.gov.au/water/dashboards/#/water-storages/summary/state">Water Storage Dashboard</a> tracks water storages levels across Australia. <a href="https://e.bom.gov.au/link/id/zzzz4e93af6f85dc4480/page.html?prompt=1%26parent_id=zzzz4e938f4426c59538">Subscribe</a> to receive our climate and water emails.</em></p><img src="https://counter.theconversation.com/content/144702/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>Downpours in eastern Australia this year have been good for crops and some dams. But when it comes to drought, Australia is not out of the woods yet.Lynette Bettio, Senior Climatologist, Australian Bureau of MeteorologyShannon Symons, Hydrologist, Australian Bureau of MeteorologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1344372020-04-02T14:55:59Z2020-04-02T14:55:59ZLagos is getting less rain, but more heavy storms. What it can do to prepare<figure><img src="https://images.theconversation.com/files/324008/original/file-20200330-146671-t2l75r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lagos residents need to know more about the risk of heavy storms. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/photos/rainfall-in-lagos-nigeria?agreements=pa:77130&family=editorial&phrase=rainfall%20in%20lagos,%20nigeria&sort=best#license">Pius Utomi Ekpe/AFP via Getty Images </a></span></figcaption></figure><p><em>Lagos State can expect to experience <a href="https://punchng.com/lagos-to-experience-270-days-of-rainfall-in-2020/">270 days of rainfall</a> in 2020. Many Lagosians who suffered from the 2012 and 2017 <a href="https://theconversation.com/why-flooding-in-nigeria-is-an-increasingly-serious-problem-82272">devastating flooding</a> are wondering whether this is usual or not. Nelson Odume unpacks the issues.</em></p>
<p><strong>What have been the notable rainfall patterns in Lagos over the last 60 years</strong>?</p>
<p>When one looks at the average annual rainfall received from 1960 – 2010, there is a <a href="https://link.springer.com/article/10.1007/s10661-016-5549-z">gradual decrease</a> in rainfall amount. </p>
<p>Also, from 1960 – 2010, on average, rainfall in Lagos began in late March, peaked in June and then ended in October. But there was a shifting rainfall events from the months of May, June, July to the months of August, September and October. The second peaking of rainfall happened in September. </p>
<p>A <a href="https://iwaponline.com/jwcc/article/doi/10.2166/wcc.2019.047/69712/Challenges-in-water-resources-of-Lagos-mega-city">research paper</a> of projected climate change between 2010 – 2099, showed that, apart from a few years towards the end of the century, rainfall amount will continue to decrease in Lagos and temperature will continue to rise. The decrease in rainfall can be up to 140 mm. </p>
<h2>So, where do the risks lie for people living in the city?</h2>
<p>While the amount of rainfall has been decreasing in Lagos, the frequency and intensity of extreme whether events are on the rise. So, the risk is not much about the annual rainfall amount, but its distribution and intensity when it happens. </p>
<p>These are not entirely new. For example, on June 17, 2004, Victoria Island received <a href="https://www.preventionweb.net/files/11042_FrameworkforCity.pdf">rainfall amount of about 243 mm </a>(78% of the month’s rainfall), causing devastating flooding. More recently, intense precipitations are happening more frequently in the months of June, July and September, increasing the risk of flooding. </p>
<p><strong>What are the biggest weather risks faced by people in the city?</strong></p>
<p>The risk is the growing 1-5 day extreme rainfall events, which have been predicted to increase in Lagos State. It is these extreme precipitation events that Lagosians should be more worried about. </p>
<p>Apart from extreme rainfall, storm surges are also predicted to rise in Lagos. These are also not entirely new. For example, on August 17, 1995 Victoria Island <a href="https://www.preventionweb.net/files/11042_FrameworkforCity.pdf">suffered</a> from a devastating storm surge that destroyed properties worth billions of Naira. </p>
<p><strong>What makes Lagos so vulnerable?</strong></p>
<p>Lagos is bordered in the south by the Atlantic Ocean, in the east and southwest by lagoons and creeks. The relative position of Lagos, being a coastal city, makes it very vulnerable to coastal flooding and coastal erosion as a result of sea level rise. It is <a href="https://www.preventionweb.net/files/11042_FrameworkforCity.pdf">predicted</a> that Lagos could experience about 12-17 cm sea level rise by 2050. This could increase coastal flooding because Lagos topography is flat and only about 0-5 m above sea level. In addition, sea level rise would increase coastal erosion and saltwater intrusion into groundwater. This would make the city’s groundwater salty and would increase treatment costs.</p>
<p>Another factor that makes Lagos more vulnerable is that about 90% of Lagos is already built up. What this means is that land surfaces are covered with buildings, roofs, concrete and roads. These materials are largely impermeable. The natural soil and vegetation, which usually retain rainwater and make it to flow slowly, are removed giving way to materials that do not hold rainwater. </p>
<p>The implication is that when it rains, water is quickly collected into adjacent rivers, and these rivers easily become overwhelmed, leading to flooding. Because of the increased run-off, river channels can become modified, which can also increase the risk of flooding.</p>
<p>Insufficient drainage system and solid waste collection, illegal dumps, unplanned building on flood prone areas such as wetlands, as well as high population density are all contributing to flooding in Lagos.</p>
<p><strong>What are government’s responsibilities?</strong> </p>
<p>First, Lagos state government needs to strengthen its capacity for evidence-based decision making. The scientific community (researchers), practitioners and political class must work closely together so that decisions are informed by up to date scientific analysis. And the science must be informed by on the ground challenges.</p>
<p>Second, Lagos state government should embark on structural measures such as the construction of dikes, embankment and seawalls to minimise the risk of flooding in the city. The clearing of waterways, channels and drainage systems as well as efficient solid waste collection system would also help. And there are structural steps that could be taken such as building design codes that promote the use of permeable pavement as well as infiltration trenches.</p>
<p>Third, Lagos state government flood predictive capacity must be matched with effective early warning communication of risk, particularly to risk-prone population. Prediction is not enough. Communities should be mobilised to mitigate flooding risk through effective communication of early warning systems.</p>
<p>Fourth, land use planning and protection of ecosystems hold promise for mitigating risk. Lagos state government must continue to strengthen compliance and enforcement about land use planning, ensuring that developments are prohibited in flood prone areas, and sensitive ecosystems such as wetlands.</p>
<p>Finally, without adequate involvement of local communities, including local knowledge systems, the above measures would likely fail due to a lack of sense of ownership by the people. Therefore, Lagos state must also continue to strengthen its capacity to work with local communities and diverse stakeholders in addressing flooding risk within the city. </p>
<p><strong>What should Lagosians do to prepare for the rainy season?</strong></p>
<p>They must join government efforts to reduce the effects of flooding in the city. One way every person can do this is to avoid indiscriminate dumping of wastes on waterways, water channels and wetlands. </p>
<p>Lagosians can also form voluntary community-based organisations whose aims are to sensitise local people on the importance of keeping the drainage clean and liaising with relevant government authorities for effective communication of risk. </p>
<p>Finally, the threat of flooding in Lagos is an opportunity to look in the direction of nature-based solutions such as creating green spaces and protection of wetlands. These will mitigate the devastating effects of flooding. They can also <a href="https://www.nature.com/articles/s41467-018-04396-1">help</a> create jobs through recreation and tourism, conserve ecosystems and storing carbon.</p><img src="https://counter.theconversation.com/content/134437/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nelson Odume receives funding from International Science Council, Network of African Science Academies, National Research Foundation, Water Research Commission and the European Union Education, Audiovisual and Cultural Executive Agency. </span></em></p>Lagos is vulnerable to heavy storms but the impact can be mitigated with better preparation.Nelson Odume, Researcher, Rhodes UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1328622020-03-03T03:07:07Z2020-03-03T03:07:07ZAfter a summer of extremes, here’s what to expect this autumn<p>The past Australian summer was a season of two contrasting halves. So did the midsummer weather change make a dent in the drought, and is it likely to continue through autumn?</p>
<p>The first half of summer was exceptionally hot, dry and dusty. Parts of eastern and southern Australia were engulfed by significant bushfires, and smoke haze covered large areas.</p>
<p>In the second half of the season, tropical moisture at times extended into southern Australia, producing well above-average rainfall for some areas. This was great news for many, but some parts of the country missed out. Other areas need follow-up falls over the coming months to ease the long-term dry, and inland water storages increased only slightly.</p>
<p>The autumn outlook suggests warmer-than-average temperatures for most of the country. There is also a slightly increased chance of wetter-than-average conditions in parts of southern Australia, indicating some areas could see a gradual easing of the drought conditions. </p>
<h2>What happened this summer?</h2>
<p>Summer 2019-20 was the nation’s second hottest in 110 years of records, driven in part by Australia’s hottest December on record in 2019. Warmth across much of the tropical north and east persisted into January and February. Summer nights were second-warmest on record.</p>
<p>Total summer rainfall was closer to normal – 8% below the long-term average. But the rainfall figures hide the significant shift in the climate mid-way through the season.</p>
<p>Australia experienced very warm and dry conditions in the lead-up to summer. With a delayed onset of the monsoon moving into the southern hemisphere, heat built across northern and central Australia from the start of December and was drawn south by weather systems.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/some-say-weve-seen-bushfires-worse-than-this-before-but-theyre-ignoring-a-few-key-facts-129391">Some say we've seen bushfires worse than this before. But they're ignoring a few key facts</a>
</strong>
</em>
</p>
<hr>
<p>Australia had its hottest day on record on December 18, with a nationwide average temperature of 41.88°C. This was far above the previous record of 40.32°C set on January 7, 2013.</p>
<p>Six other days in December 2019 also exceeded this previous record. To put this in context, the Australia-wide average maximum temperature has exceeded 40°C for
more days in the past two summers than in the preceding 110 years combined.</p>
<p>The hottest temperature recorded this summer was at Nullabor, South Australia, on December 19, when it reached 49.9°C.</p>
<p>Averaged across the continent, December maximum temperatures were 4.15°C above
average - the previous December record was 2.41°C above average, set in 2018.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/318281/original/file-20200303-66089-1lyacgv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/318281/original/file-20200303-66089-1lyacgv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=527&fit=crop&dpr=1 600w, https://images.theconversation.com/files/318281/original/file-20200303-66089-1lyacgv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=527&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/318281/original/file-20200303-66089-1lyacgv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=527&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/318281/original/file-20200303-66089-1lyacgv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=662&fit=crop&dpr=1 754w, https://images.theconversation.com/files/318281/original/file-20200303-66089-1lyacgv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=662&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/318281/original/file-20200303-66089-1lyacgv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=662&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Bureau of Meteorology/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<hr>
<h2>Then the rains came</h2>
<p>Early January brought a noticeable change to the weather, with the first tropical cyclones of the season and the belated arrival of the monsoon.</p>
<p>Tropical cyclones Blake and Claudia brought heavy rain to much of the Top End and northern and central parts of Western Australia, while the east coast saw heavy falls in northern New South Wales and southeast Queensland.</p>
<p>February brought more tropical moisture to the continent and another two cyclones—Damien and Esther.</p>
<p>Despite this, temperatures across the north remained very warm. The monsoon did not arrive until January 18, some three weeks later than normal, though almost a week earlier than the previous year. Even after the monsoon arrived it was sporadic, so did little to temper the heat.</p>
<p>The Darwin River Dam (Darwin’s main water storage) dropped to 54% capacity - the result of two relatively dry wet seasons in a row.</p>
<p>In contrast, in southern parts of Australia, February felt milder than normal. After Melbourne had three days over 40°C in December – the most in December since 1897 - it had no days at all over 35°C in February. This last happened in 1994.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/318282/original/file-20200303-66106-ms1tzn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/318282/original/file-20200303-66106-ms1tzn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=527&fit=crop&dpr=1 600w, https://images.theconversation.com/files/318282/original/file-20200303-66106-ms1tzn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=527&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/318282/original/file-20200303-66106-ms1tzn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=527&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/318282/original/file-20200303-66106-ms1tzn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=662&fit=crop&dpr=1 754w, https://images.theconversation.com/files/318282/original/file-20200303-66106-ms1tzn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=662&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/318282/original/file-20200303-66106-ms1tzn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=662&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Bureau of Meteorology/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<hr>
<h2>What’s driving all this?</h2>
<p>The abrupt change in weather patterns mid-season can be attributed to changes in two key Australian climate drivers: a strong positive phase of the <a href="http://www.bom.gov.au/climate/iod/">Indian Ocean Dipole (IOD)</a>, and a negative phase of the <a href="http://www.bom.gov.au/climate/sam/">Southern Annular Mode (SAM)</a>. </p>
<p>A positive IOD typically brings drier weather to much of southern, central and northern Australia. The 2019 positive IOD was the strongest since 1997 and affected large parts of the country (and eastern Africa) during the second half of the year. Normally such an event ends with the movement of the Asian monsoon into the southern hemisphere in late spring/early summer, but in 2019–20 this movement occurred about a month later than usual.</p>
<p>The delayed arrival of the Australian monsoon was likely related to the strength of the IOD itself, which prevented the monsoon’s southward shift.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-air-above-antarctica-is-suddenly-getting-warmer-heres-what-it-means-for-australia-123080">The air above Antarctica is suddenly getting warmer – here's what it means for Australia</a>
</strong>
</em>
</p>
<hr>
<p>The negative SAM typically brings drier and hotter than average weather to much of southeast and eastern Australia in spring and summer. It was triggered by a <a href="https://theconversation.com/the-air-above-antarctica-is-suddenly-getting-warmer-heres-what-it-means-for-australia-123080">sudden warming of the stratosphere</a> above Antarctica, identified in early September. This rare event affected Australian climate from October to December.</p>
<p>Both negative SAM and positive IOD are known to enhance the likelihood of <a href="https://rd.springer.com/article/10.1007%2Fs00382-013-2016-1">increased springtime heatwaves</a> and fire weather in southeast Australia.</p>
<p>In addition to these events, Australia’s <a href="http://www.bom.gov.au/state-of-the-climate/">changing climate</a> underpinned the drier and warmer weather across southern Australia in winter and spring.</p>
<h2>What to expect in autumn</h2>
<p>Rain has <a href="https://theconversation.com/rain-has-eased-the-dry-but-more-is-needed-to-break-the-drought-131660">eased the dry in some places</a>, but more is needed. Most heavy rain was recorded east of the Great Dividing Range, while larger totals west of the range generally fell in regions that didn’t feed into water storages, or where soils were so dry there was little runoff into storages.</p>
<p>While Sydney’s water storages rose from 42% to 81% during the second half of summer, storages in the northern Murray—Darling Basin only rose from 6% to 12% - similar to levels at the height of the Millennium drought.</p>
<p>And while some areas had good summer rainfall, others missed out. Western NSW and southwest Queensland endured another dry summer.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/this-crisis-has-been-unfolding-for-years-4-photos-of-australia-from-space-before-and-after-the-bushfires-129450">'This crisis has been unfolding for years': 4 photos of Australia from space, before and after the bushfires</a>
</strong>
</em>
</p>
<hr>
<p>The autumn outlook suggests parts of southern Australia have a slightly increased chance of being wetter-than-average, while scattered parts of the north may see a drier end to the northern wet season. Autumn days are likely to be warmer than average for most of the country, except for parts of southern Australia, suggesting evaporation will remain above average.</p>
<p>This outlook would indicate some areas could see a gradual easing of the drought conditions.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/318212/original/file-20200303-18275-142m9ui.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/318212/original/file-20200303-18275-142m9ui.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/318212/original/file-20200303-18275-142m9ui.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/318212/original/file-20200303-18275-142m9ui.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/318212/original/file-20200303-18275-142m9ui.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/318212/original/file-20200303-18275-142m9ui.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/318212/original/file-20200303-18275-142m9ui.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Bureau of Meteorology/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<hr>
<p>For more information, watch the Bureau’s March–May 2020 <a href="http://www.bom.gov.au/climate/outlooks/#/overview/summary">Climate and Water Outlook video</a> and <a href="https://e.bom.gov.au/link/id/zzzz53bb31db150fb433/page.html?prompt=1">subscribe</a> to receive Climate Information emails.</p><img src="https://counter.theconversation.com/content/132862/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>Autumn may bring wetter-than-average conditions in parts of southern Australia, indicating a gradual easing of the drought in some areas.Catherine Ganter, Senior Climatologist, Australian Bureau of MeteorologyAndrew B. Watkins, Head of Long-range Forecasts, Australian Bureau of MeteorologyDavid Jones, Climate Scientist, Australian Bureau of MeteorologySkie Tobin, Climatologist, Australian Bureau of MeteorologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1139312019-03-20T14:11:47Z2019-03-20T14:11:47ZTropical cyclone Idai: The storm that knew no boundaries<figure><img src="https://images.theconversation.com/files/264845/original/file-20190320-93054-1vezzf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">People leaving their homes in the flooded section of Praia Nova, Beira, Mozambique in the wake of tropical cyclone Idai.</span> <span class="attribution"><span class="source">Denis Onyodi/ IFRC handout</span></span></figcaption></figure><p>Tropical cyclone Idai has made <a href="https://www.economist.com/middle-east-and-africa/2019/03/19/tropical-cyclone-idai-may-have-killed-more-than-1000-in-mozambique">headlines</a> across southern Africa throughout the month of March. Lingering in the Mozambique Channel at tropical cyclone intensity for six days, the storm made landfall in Beira, Mozambique in the middle of the month, then tracked in a westerly direction until its dissipation. </p>
<p>The greatest impact of the storm was experienced on landfall. It caused flooding, excessive wind-speed and storm surge damage in the central region of Mozambique. Adjacent countries of <a href="https://theconversation.com/why-malawi-is-failing-to-protect-people-from-floods-and-what-needs-to-be-done-113794">Malawi</a> and <a href="https://www.iol.co.za/news/africa/cycloneidai-death-toll-in-zimbabwe-soars-to-150-about-2000-missing-19974637">Zimbabwe</a> experienced severe rainfall, flooding and damage from the high wind speed. <a href="https://www.accuweather.com/en/weather-news/tropical-storm-likely-to-form-near-madagascar-by-end-of-the-weekend/70007641">Madagascar</a> also experienced bouts of high rainfall during the storm’s pathway to Beira. </p>
<p>The flooding has left hundreds of thousands of people <a href="https://www.afp.com/en/news/717/mozambique-zimbabwe-cyclone-deaths-exceed-300-un-boosts-aid-doc-1er9m712">homeless and displaced</a> across the region while the death toll has continued to rise in the week following landfall. The effects of the cyclone were felt as far south as South Africa and introduced <a href="https://city-press.news24.com/News/eskom-blames-cyclone-idai-for-sas-power-outages-20190317">rolling blackouts</a> due to damaged transmission lines that supply the country with 1100 MW of power from Cahora Bassa in northern Mozambique.</p>
<p>Historically, <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.3932">nine storms</a> that had reached tropical cyclone intensity made landfall on Mozambique. A larger number of weaker tropical systems, including tropical storms and depressions affect the region, with a total landfall of all tropical systems of 1.1 per annum. </p>
<p>The <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.3932">most severe </a>tropical cyclone to make landfall in Mozambique was tropical cyclone Eline in February 2000. It had a category 4 intensity on landfall and resulted in 150 deaths, 1000 casualties from flooding, 300 000 people displaced and four ships sunk.</p>
<p>The storms off Africa’s east coast are weaker than their northern hemisphere counterparts. Category 4 and 5 tropical cyclones make landfall at a near-annual rate in the North Atlantic and North Pacific. </p>
<h2>Why the wide impact</h2>
<p>Why have so many countries been affected?</p>
<p>Tropical cyclones are large storm systems. Immediately surrounding the eye of the storm – a region of calm weather, no wind and no rain – are spirals of storm clouds that span a minimum radius of ~100km. These cloud bands represent the thunder storm conditions, with the rain and winds typical of a tropical cyclone.</p>
<p>A ~100km radius is typical of category 1 tropical cyclones, the lowest intensity ones. As the storms intensify to categories 2, 3, 4 and 5, the <a href="https://journals.ametsoc.org/doi/10.1175/MWR-D-10-05062.1">size</a> increases significantly. This means that a high intensity storm, such as tropical cyclone Idai, has a range of impact significantly larger than the storm track that it follows.</p>
<p>In recent years concerns have been growing about the impact of climate change on cyclones. <a href="https://www.nature.com/articles/nature07234">Research</a> has shown that changes to the world’s temperature, as well as ocean warming, are responsible for an increase in the severity of tropical cyclones. This has recently been <a href="http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532018000600018">researched</a> for the South Indian Ocean. As the ocean is warming, the region which experiences temperatures conducive to tropical cyclone formation is expanding and temperatures in the tropical regions are becoming warm enough for cyclone intensification. Category 5 tropical cyclones, which have been experienced in the North Atlantic for almost a century, started to occur in the South Indian Ocean since 1994, and have occurred increasingly frequently since then.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/rising-sea-temperatures-are-shaping-tropical-storms-in-southern-africa-73139">Rising sea temperatures are shaping tropical storms in southern Africa</a>
</strong>
</em>
</p>
<hr>
<p>This means that as climate change continues and intensifies, so too do these storms. This will mean a greater frequency of not only severe damage from storms, but damage over a larger region. In addition to the impact of warming on the storm intensity, climate warming has also been found to <a href="https://www.nature.com/articles/s41598-017-08533-6">increase the expanse</a> of the storms within any given intensity.</p>
<h2>Cyclone Idai</h2>
<p>So how intense was tropical cyclone Idai? </p>
<p>Storm track records, which include the geographic location of the storm at set time intervals, the wind speed and the atmospheric pressure, are documented by a number of regional climatological organisations. This data is synthesised by the National Oceanographic and Atmospheric Association, providing a useful resource for scientists to explore storm behaviour. </p>
<p>Tropical cyclones are classified on the basis of their wind speed and central pressure. The weakest storms to be classified as tropical cyclones – category 1 – have a minimum sustained wind speed of 119km/hr. At category 3 the storms have a minimum wind speed of 178 km/h. As the category increases, so too does the potential for damage. Category 1 storms are <a href="http://hydromet.gov.bz/tropical-weather/saffir-simpson-scale">classified</a> as resulting in dangerous winds that cause some damage, whereas category 3 storms are expected to cause devastating damage.</p>
<p>The history of tropical cyclone Idai is documented in these records. The cyclone reached <a href="http://www.atms.unca.edu/ibtracs/ibtracs_v04r00/index.php?name=v04r00-2019068S17040#intensity">category 3</a> intensity between 03:00-06:00 on the 11th March 2019, while positioned at its most easterly extent of the storm track. By 03:00 on the 12th March the storm had dissipated to category 2 intensity, and it fluctuated between intensities of categories 2 and 3 over the 36 hours that followed. </p>
<p>From noon on the 13th March the storm maintained a category 3 intensity which persisted until landfall on the 14th.</p>
<h2>What needs to be done</h2>
<p>Storms that affect many countries present particular challenges. They clearly have no regard for political boundaries. The fact that they affect lots of countries presents challenges in both preparing for storm events in a proactive way and responding to prevent loss of life and livelihood. This requires countries to communicate effectively with one another, to provide coherent messages about the forecasting of the storm track and potential damage, and to facilitate effective evacuations. </p>
<p>This storm provides a grim prospect of the future of tropical cyclones in a region under continued threat from climate change. Effective adaptation to minimise storm damage is essential in preparing the region for an increase in the severity of these storms. Disaster risk management plans are also very important to minimise the loss of life.</p><img src="https://counter.theconversation.com/content/113931/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Fitchett receives funding from the DST-NRF Centre of Excellence for Palaeoscience. </span></em></p>The recent storms provide a grim reminder of the prospect of future tropical cyclones in a region under continued threat from climate change.Jennifer Fitchett, Senior Lecturer in Physical Geography, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.