tag:theconversation.com,2011:/us/topics/water-cycle-6493/articlesWater cycle – The Conversation2024-03-05T15:02:19Ztag:theconversation.com,2011:article/2248692024-03-05T15:02:19Z2024-03-05T15:02:19ZArctic rivers face big changes with a warming climate, permafrost thaw and an accelerating water cycle − the effects will have global consequences<figure><img src="https://images.theconversation.com/files/579392/original/file-20240303-24-mmw6cz.jpg?ixlib=rb-1.1.0&rect=0%2C1333%2C9000%2C6157&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Water from the Mackenzie River, seen from a satellite, carries silt and nutrients from land to the Arctic Ocean.</span> <span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/90703/mackenzie-meets-beaufort">Jesse Allen/NASA Earth Observatory</a></span></figcaption></figure><p>As the Arctic warms, its mighty rivers are changing in ways that could have vast consequences – not only for the Arctic region but for the world.</p>
<p>Rivers represent the land branch of the earth’s hydrological cycle. As rain and snow fall, rivers transport freshwater runoff along with dissolved organic and particulate materials, including carbon, to coastal areas. With the Arctic now warming nearly <a href="https://theconversation.com/arctic-is-warming-nearly-four-times-faster-than-the-rest-of-the-world-new-research-188474">four times faster</a> than the rest of the world, the region <a href="https://doi.org/10.1175/2010JCLI3421.1">is seeing more precipitation</a> and the permafrost is thawing, leading to stronger river flows.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows major rivers and their water sheds, primarily in Russia, Alaska and Canada." src="https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=596&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=596&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=596&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=749&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=749&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579353/original/file-20240303-28-rq37ng.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=749&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Major river basins of the Arctic region.</span>
<span class="attribution"><a class="source" href="https://www.pmel.noaa.gov/arctic-zone/detect/land-river.shtml">NOAA Arctic Report Card</a></span>
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<p>We’re climate scientists who study how warming is influencing the water cycle and ecosystems. <a href="https://doi.org/10.5194/tc-18-1033-2024">In a new study</a> using historical data and sophisticated computer models of Earth’s climate and hydrology, we explored how climate change is altering Arctic rivers. </p>
<p>We found that thawing permafrost and intensifying storms will change how water moves into and through Arctic rivers. These changes will affect coastal regions, the Arctic Ocean and, potentially, the North Atlantic, as well as the climate.</p>
<h2>Thawing permafrost: Big changes in Arctic soils</h2>
<p>Permafrost thaw is one of the most consequential changes that the Arctic is experiencing as temperatures rise. </p>
<p>Permafrost is soil that has been <a href="https://climate.mit.edu/explainers/permafrost">frozen for at least two years</a> and often for millennia. It covers approximately 8.8 million square miles (about 22.8 million square kilometers) in Earth’s Northern Hemisphere, but that area is shrinking as the permafrost thaws.</p>
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<a href="https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two people stand on a cliff with permafrost evident." src="https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579355/original/file-20240303-22-s4w5f9.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">Erosion reveals ice-rich permafrost near Teshekpuk Lake, Alaska.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/usgeologicalsurvey/12116729705">Brandt Meixell/USGS</a></span>
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<a href="https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows where permafrost is found, both in ground and below the ocean." src="https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=425&fit=crop&dpr=1 600w, https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=425&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=425&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=534&fit=crop&dpr=1 754w, https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=534&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/564666/original/file-20231210-25-jz5ezj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=534&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Known permafrost zones in the Northern Hemisphere.</span>
<span class="attribution"><a class="source" href="https://www.grida.no/resources/13519">GRID-Arendal/Nunataryuk</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>Historically, most water going into Arctic rivers flows atop frozen permafrost soils in spring. Scientists call this “overland runoff.” </p>
<p>However, our results suggest that as warming continues, an increasing fraction of annual river flow will come from under the surface, through thawed soils in the degrading permafrost. As the overall flow increases with more precipitation, as much as 30% more of it could be moving underground by the end of this century as subsurface pathways expand.</p>
<p>When water flows through soil, it picks up different chemicals and metals. As a result, water coming into rivers will likely have a different chemical character. For example, it may carry more nutrients and dissolved carbon that can affect coastal zones and the global climate. The fate of that mobilized carbon is an active area of study.</p>
<p>More carbon in river water could end up “outgassed” upon reaching placid coastal waters, increasing the amount of carbon dioxide released into the atmosphere, which further drives <a href="https://doi.org/10.1038/nature14338">climate warming</a>. The thaw is also revealing other nasty surprises, such as the <a href="https://www.usatoday.com/story/news/politics/2023/11/18/arctic-permafrost-thawing-deadly-pathogens/71581668007/">emergence of long-frozen viruses</a>. </p>
<h2>More rain and snow, more runoff</h2>
<p>The Arctic’s water cycle is also ramping up as temperatures rise, meaning more precipitation, evaporation, plant transpiration and river discharge. This is primarily due to a warmer atmosphere’s inherent ability to hold more moisture. It’s the same reason that <a href="https://theconversation.com/why-a-warming-climate-can-bring-bigger-snowstorms-176201">bigger snowstorms are occurring</a> as the climate warms. </p>
<p>Our study found that the bulk of the additional precipitation will occur across far northern parts of the Arctic basin. As sea ice disappears in a warming climate, computer models agree that a more open Arctic Ocean will feed more water to the atmosphere, where it will be transported to adjacent land areas to fall as precipitation. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/579640/original/file-20240304-28-gtrh1a.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two maps show increasing snow and rainfall" src="https://images.theconversation.com/files/579640/original/file-20240304-28-gtrh1a.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579640/original/file-20240304-28-gtrh1a.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=326&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579640/original/file-20240304-28-gtrh1a.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=326&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579640/original/file-20240304-28-gtrh1a.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=326&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579640/original/file-20240304-28-gtrh1a.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=410&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579640/original/file-20240304-28-gtrh1a.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=410&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579640/original/file-20240304-28-gtrh1a.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=410&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Changes projected this century in annual rainfall and snowfall simulated by the computer model used in the study. Red areas represent increases.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.5194/tc-18-1033-2024">Rawlins and Karmalkar, 2024</a></span>
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<p>More snow in northern Alaska, Siberia and Canada will lead to more water flowing in rivers, potentially up to 25% more under a high-warming scenario based on our research. There is more carbon in the soil in northern parts of the Arctic compared with the south. With permafrost thaw, those regions will also see more water coming into rivers from below the surface, where additional soil carbon can leach into the water and become dissolved organic carbon.</p>
<p>More <a href="https://doi.org/10.1088/1748-9326/aaa1fe">old carbon is already showing up</a> in samples gathered from Arctic rivers, attributed to permafrost thaw. Carbon dating shows that some of this carbon has been frozen for thousands of years. </p>
<h2>Impacts will cascade through Arctic ecosystems</h2>
<p>So, what does the future hold? </p>
<p>One of the most notable changes expected involves the transport of fresh water and associated materials, such as dissolved organic carbon and heat energy, to Arctic coastal zones. </p>
<figure class="align-center ">
<img alt="A scientist in a rain jacket and cap holds up a water sample in a jar." src="https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579395/original/file-20240303-28-uto6m1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">James McClelland of the Beaufort Lagoon Ecosystems Long Term Ecological Research program examines a water sample from a stream near Utqiagvik on Alaska’s North Slope. The brown tint is dissolved organic matter.</span>
<span class="attribution"><span class="source">Michael A. Rawlins</span></span>
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<p><a href="https://ble.lternet.edu/">Coastal lagoons</a> may become fresher. This change would affect organisms up and down the food chain, though <a href="https://doi.org/10.3389/fmars.2022.738363">our current understanding</a> of the potential affects of changes in fresh water and dissolved organic carbon is still murky.</p>
<p>River water will also be warmer as the climate heats up and has the potential to melt coastal sea ice earlier in the season. Scientists <a href="https://theconversation.com/arctic-report-card-2023-from-wildfires-to-melting-sea-ice-the-warmest-summer-on-record-had-cascading-impacts-across-the-arctic-218872">observed this in spring 2023</a>, when unusually warm water in Canada’s Mackenzie River carried heat to the Beaufort Sea, contributing to early coastal sea ice melting.</p>
<figure class="align-center ">
<img alt="A satellite view of the Arctic coast showing a river and sea ice breaking up." src="https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579397/original/file-20240303-20-8tx0p.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">
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<span class="caption">Fresh water flowing from rivers such as Canada’s Mackenzie River, at the bottom center of the satellite image, into the Beaufort Sea can break up sea ice early.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/83271/river-discharge-alters-arctic-sea-ice">NASA Earth Observatory</a></span>
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<p>Finally, more river water reaching the coast has the potential to freshen the Arctic Ocean, particularly along northern Eurasia, where big Russian rivers export massive amounts of fresh water each year. </p>
<p>There are concerns that <a href="https://arctic.noaa.gov/report-card/report-card-2021/river-discharge/">rising river flows in that region</a> are influencing the Atlantic Meridional Overturning Circulation, the currents that circulate heat from the tropics, up along the U.S. East Coast and toward Europe. Evidence is mounting that these currents <a href="https://theconversation.com/the-atlantic-oceans-major-current-system-is-slowing-down-but-a-21st-century-collapse-is-unlikely-214647">have been slowing in recent years</a> as more fresh water enters the North Atlantic. If the circulation shuts down, it would <a href="https://theconversation.com/atlantic-ocean-is-headed-for-a-tipping-point-once-melting-glaciers-shut-down-the-gulf-stream-we-would-see-extreme-climate-change-within-decades-study-shows-222834">significantly affect temperatures</a> across North America and Europe.</p>
<p>At the coast, changing river flows will also affect the plants, animals and Indigenous populations that call the region home. For them and for the global climate, our study’s findings highlight the need to closely watch how the Arctic is being transformed and take steps to mitigate the effects.</p><img src="https://counter.theconversation.com/content/224869/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael A. Rawlins receives funding from The Department of Energy, the National Aeronautics and Space Administration and the U.S. National Science Foundation. </span></em></p><p class="fine-print"><em><span>Ambarish Karmalkar receives funding from the Department of Energy and the United States Geological Survey. </span></em></p>A new study shows how thawing permafrost and intensifying storms will change how water moves into and through Arctic rivers.Michael A. Rawlins, Associate Director, Climate System Research Center and Associate Professor of Climatology, UMass AmherstAmbarish Karmalkar, Assistant Professor of Geosciences, University of Rhode IslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2208362024-01-10T19:15:34Z2024-01-10T19:15:34ZHow 2023’s record heat worsened droughts, floods and bushfires around the world<p>2023 was a year of record-breaking heat, devastating storms and floods, deepening droughts and raging wildfires. These events showed how climate change is affecting the global water cycle and our livelihoods.</p>
<p>Our international team of researchers has released a report, the <a href="https://www.globalwater.online/">Global Water Monitor</a>, documenting the impact of the record heat in 2023 on the water cycle. We used data from thousands of ground stations and satellites to provide real-time information on various environmental parameters. </p>
<p>The report summarises conditions and events in 2023 and long-term trends. We found global warming is profoundly changing the water cycle. As a result, we are seeing more rapid and severe droughts as well as more severe storms and flood events. </p>
<p>Scores of countries had record average annual temperatures in 2023. Severe droughts hit three continents. The world’s largest forests suffered, with Canada battling <a href="https://theconversation.com/yellowknife-and-kelowna-wildfires-burn-in-what-is-already-canadas-worst-season-on-record-211817">huge fires</a> and the Amazon <a href="https://www.nature.com/articles/d41586-023-03469-6">hit hard by drought</a>.</p>
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Read more:
<a href="https://theconversation.com/a-heatwave-in-antarctica-totally-blew-the-minds-of-scientists-they-set-out-to-decipher-it-and-here-are-the-results-220672">A heatwave in Antarctica totally blew the minds of scientists. They set out to decipher it – and here are the results</a>
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<h2>Heat is drying out the world</h2>
<p>The most obvious sign of the climate crisis is the unprecedented heat waves that swept the globe in 2023. Earth’s <a href="https://www.science.org/content/article/even-warmer-expected-2023-was-hottest-year-record">hottest year on record</a> gave us a glimpse of what a typical year with 1.5°C of warming may look like. Global warming consistently more than 1.5°C above pre-industrial levels is expected to have extreme and irreversible impacts on the Earth system.</p>
<p>Some 77 countries experienced their highest average annual temperature in at least 45 years. Temperature records were shattered from Canada to Brazil, Spain to Thailand.</p>
<p>The high temperatures were often accompanied by very low air humidity. The relative air humidity of the global land surface was the second-driest on record in 2023.</p>
<p>Rapid drying of farms and forests caused crops to fail and <a href="https://theconversation.com/fire-is-consuming-more-than-ever-of-the-worlds-forests-threatening-supplies-of-wood-and-paper-216643">forests to burn</a>. Lack of rain and soaring temperatures intensified multi-year droughts in vulnerable regions such as South America, the Horn of Africa and the Mediterranean.</p>
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Read more:
<a href="https://theconversation.com/fire-is-consuming-more-than-ever-of-the-worlds-forests-threatening-supplies-of-wood-and-paper-216643">Fire is consuming more than ever of the world's forests, threatening supplies of wood and paper</a>
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<p>The past two decades have significantly increased air temperatures and reduced air humidity. This continuing trend toward drier conditions is threatening agriculture, biodiversity and overall water security.</p>
<p>These conditions heighten heat stress and increase the water needs of people, crops and ecosystems.</p>
<p>Scorching conditions inflicted extensive damage on the world’s largest forests. Massive wildfires ravaged Canada during the northern summer. Later in the year the Amazon rainforest and rivers descended into severe drought.</p>
<p>The world’s forests have been soaking up a lot of our fossil fuel emissions. That’s because plant photosynthesis absorbs carbon dioxide from the atmosphere. Large disturbances like fire and drought reduce or even <a href="https://theconversation.com/unprecedented-drought-in-the-amazon-threatens-to-release-huge-stores-of-carbon-podcast-219250">reverse that function</a>.</p>
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Read more:
<a href="https://theconversation.com/unprecedented-drought-in-the-amazon-threatens-to-release-huge-stores-of-carbon-podcast-219250">Unprecedented drought in the Amazon threatens to release huge stores of carbon – podcast</a>
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<h2>Water cycle changes fuel intense storms</h2>
<p>A change in circulation and sea temperatures in the Pacific Ocean to El Niño conditions influenced the global water cycle in 2023. But this happened against a backdrop of increasing sea surface temperatures due to global warming.</p>
<p>Rising sea surface and air temperatures have been intensifying the strength and rainfall intensity of monsoons, cyclones and other storm systems.</p>
<p>We saw this happen close to home. <a href="https://theconversation.com/north-queenslands-record-breaking-floods-are-a-frightening-portent-of-whats-to-come-under-climate-change-220039">Cyclone Jasper</a> battered northern Queensland and severe storms formed in south-east Queensland, leaving a trail of destruction. The cyclone moved much slower than expected, causing torrential rains and widespread flooding. </p>
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Read more:
<a href="https://theconversation.com/north-queenslands-record-breaking-floods-are-a-frightening-portent-of-whats-to-come-under-climate-change-220039">North Queensland's record-breaking floods are a frightening portent of what's to come under climate change</a>
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<p>In 2023, we also saw other cyclones behave in unexpected and deadly ways. A cyclone <a href="https://theconversation.com/floods-cyclones-thunderstorms-is-climate-change-to-blame-for-new-zealands-summer-of-extreme-weather-201161">travelled across to New Zealand</a>. The <a href="https://theconversation.com/cyclone-freddy-was-the-most-energetic-storm-on-record-is-it-a-harbinger-of-things-to-come-201771">longest-lived cyclone ever recorded</a> battered south-eastern Africa for weeks. And a cyclone <a href="https://theconversation.com/was-the-freak-medicane-storm-that-devastated-libya-a-glimpse-of-north-africas-future-213680">developed in the Mediterranean Sea</a>, crossing from Greece to destroy reservoir dams in Libya, killing thousands. </p>
<p>The estimated global damage from cyclones in 2023 surpassed <a href="https://www.globalwater.online/">US$45 billion</a>.</p>
<p>Warmer sea temperatures fuel such freak events. As the climate crisis deepens, we can expect more unprecedented storms.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/cyclone-freddy-was-the-most-energetic-storm-on-record-is-it-a-harbinger-of-things-to-come-201771">Cyclone Freddy was the most energetic storm on record. Is it a harbinger of things to come?</a>
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</em>
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<h2>Outlook: 2024 and beyond</h2>
<p>At the start of 2024, the greatest risk of developing or intensifying drought appears in Central and South America (except southern Brazil and Uruguay), southern Africa and western Australia. </p>
<p>Regions that received much rainfall towards the end of 2023 are unlikely to develop drought for at least several months. These include the Sahel region and the Horn of Africa, northern Europe, India, China and South-East Asia.</p>
<p>The events of 2023 show how the threat of ongoing climate change to our planet and lives is growing by the year. There were many such events in 2023, and the human and economic toll was large. These events should not be viewed as isolated incidents but as part of a broader emerging pattern. </p>
<p>Globally, the frequency and intensity of rainfall events and flooding are increasing. At the same time, there are also more and faster developing droughts, or flash droughts, that can cause crop failure and destructive wildfires within weeks or months. With the <a href="https://www.oecd.org/food-systems/understanding/triple-challenge/">global food challenge</a>, <a href="https://www.theguardian.com/environment/2022/dec/06/the-biodiversity-crisis-in-numbers-a-visual-guide-aoe">biodiversity crisis</a> and an extremely urgent need to reduce carbon emissions, these droughts and fires are among our greatest global threats.</p>
<p>Overall, 2023 provided a stark reminder of the consequences of our continued reliance on fossil fuels and the urgent need but apparent inability of humanity to act decisively to cut greenhouse gas emissions.</p><img src="https://counter.theconversation.com/content/220836/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>The impacts of record heat on the global water cycle were severe and wide-ranging – and the trend will continue in 2024.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/2169282023-11-02T18:05:50Z2023-11-02T18:05:50ZEl Niño may be drying out the southern hemisphere – here’s how that affects the whole planet<figure><img src="https://images.theconversation.com/files/557296/original/file-20231102-19-vu2x45.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4493%2C2526&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">FoxPictures / shutterstock</span></span></figcaption></figure><p>It is a well-known fact that water is the key to life on Earth. But it is less well known that only about 1% of all water on the planet is fresh water available to humans, plants or land-based animals.</p>
<p>The rest is in the oceans, or locked up in polar ice sheets and rocks. In a climate changing world, the global distribution of that 1% takes on a whole new significance.</p>
<p>A <a href="https://www.science.org/doi/10.1126/science.adh0716">new study</a> has shown that the southern hemisphere has been drying out more than the northern hemisphere over the past two decades (2001-2020). The authors suggest the principle cause is the weather phenomenon known as <a href="https://theconversation.com/uk/topics/el-nino-5638">El Niño</a>, which occurs every few years when ocean water in the eastern Pacific is warmer than usual.</p>
<p>The findings are based on data from satellites and measurements of river and stream flows, which enabled the authors to model and calculate changes in water availability. Water availability is the net difference between the amount of water supplied to the landscape, in the form of rainfall on land, and the water removed to the atmosphere by general evaporation or by plants through their leaves. </p>
<p>Even though the southern hemisphere has only a quarter of the global land area (excluding Antarctica), it appears to have a substantially greater effect on global water availability than the northern hemisphere. </p>
<p>The new analysis reveals a strong decrease in water availability in South America, most of Africa, and central and northwestern Australia. However, some regions such as the southern part of South America will have more water available.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/557299/original/file-20231102-29-fpmgkz.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Shaded world map" src="https://images.theconversation.com/files/557299/original/file-20231102-29-fpmgkz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/557299/original/file-20231102-29-fpmgkz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557299/original/file-20231102-29-fpmgkz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557299/original/file-20231102-29-fpmgkz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557299/original/file-20231102-29-fpmgkz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=440&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557299/original/file-20231102-29-fpmgkz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=440&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557299/original/file-20231102-29-fpmgkz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=440&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Trends in water availability 2001-2020. The Southern Hemisphere has more orange than blue.</span>
<span class="attribution"><a class="source" href="https://www.science.org/doi/10.1126/science.adh0716">Zhang et al / Science</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>By contrast, despite significant variations between regions, the study suggests water availability in the northern hemisphere is more or less balanced. This is in part due to extensive human influences such as irrigation, dams and food production. Such factors are more relevant in the northern hemisphere since about 90% of the world population lives there.</p>
<p>But why does any of this rather technical modelling about water availability and drying matter? What are some possible implications if the southern hemisphere is drying out more than the northern?</p>
<h2>What happens in the south affects the north too</h2>
<p>Part of the answer lies in the regions likely to experience increased drying. South America includes the Amazon rainforest, which is a key regulator for the climate, as well as a globally important habitat for species and home to many Indigenous communities. </p>
<p><a href="https://theconversation.com/is-the-amazon-rainforest-on-the-verge-of-collapse-178580">Drying of the rainforest</a> would reduce vegetation and increase the risk of fire. This would be bad news for humans and animals that live in the forest, and has the potential to release <a href="https://theconversation.com/amazon-rainforests-that-were-once-fire-proof-have-become-flammable-91775">billions of tons of carbon</a> currently locked into forest vegetation and soils. </p>
<p>South America is also a major agricultural exporter of soybeans, sugar, meat, coffee and fruits for the global market. Changes in water availability will increase stress on food systems globally.</p>
<p>Drying across most of Africa is also a real challenge. This huge continent has many climatic zones and socio-economic contrasts, with often limited resources to mitigate and adapt. </p>
<p>Pressures on food systems and habitats will create additional stresses across the continent which is already suffering from increases in global food prices linked to inflation and the <a href="https://theconversation.com/how-russia-ukraine-conflict-could-influence-africas-food-supplies-177843">war in Ukraine</a>. </p>
<p>Yields of the staple cassava have been declining due to droughts. And exports such as coffee and cocoa could also be reduced, leading to a spiral of loss of livelihoods, poverty and hunger.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/557300/original/file-20231102-27-fi48yb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Dry landscape, mountains in background" src="https://images.theconversation.com/files/557300/original/file-20231102-27-fi48yb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/557300/original/file-20231102-27-fi48yb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557300/original/file-20231102-27-fi48yb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557300/original/file-20231102-27-fi48yb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557300/original/file-20231102-27-fi48yb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557300/original/file-20231102-27-fi48yb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557300/original/file-20231102-27-fi48yb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">North west Australia is going from dry to very dry.</span>
<span class="attribution"><span class="source">Sara Winter/ shutterstock</span></span>
</figcaption>
</figure>
<p>North-west Australia is one of the country’s great wildernesses. But it would be a major error to consider the region “empty” and therefore unimportant in terms of drying. (Like most environmental issues and concerns, it is rarely advisable to isolate one aspect from another.) </p>
<p>Drying will change vegetation patterns and further increase temperatures, which could be above 35°C for large parts of the year by 2100 if emission rates continue to be high. This would have severe effects on the health of humans and habitats. </p>
<p>Similarly, drying in central Australia has knock-on effects on weather and climate for coastal areas where most of Australia’s major cities and population are situated. Drying trends are also being experienced in the <a href="https://theconversation.com/drying-land-and-heating-seas-why-nature-in-australias-southwest-is-on-the-climate-frontline-170377">south-west</a> and south-east of the country leading to habitat stresses and change, <a href="https://theconversation.com/its-official-australia-is-set-for-a-hot-dry-el-nino-heres-what-that-means-for-our-flammable-continent-209126">wildfires</a>, depleted rivers and impacts on human health, especially in urban areas.</p>
<p>As with many aspects of climate, the exact nature and scale of changes and impacts are hard to predict or model at local or regional scales. But this new paper points to clear shifts in patterns and complex climate processes in the southern hemisphere which will reduce water availability during El Niño events.</p>
<p>Drying will generate additional stresses on habitats and species in key regions. It will also impact human populations with varying capacities to adapt and, ultimately, our global food systems. Although the southern hemisphere is mostly water, what happens there really matters for the whole planet.</p>
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<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">
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<p class="fine-print"><em><span>Kevin Collins 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>New research finds fresh water losses are concentrated in South America, most of Africa and much of Australia.Kevin Collins, Senior Lecturer, Environment & Systems, The Open UniversityLicensed 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>
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<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/2011362023-03-08T17:53:06Z2023-03-08T17:53:06ZRainforests pump water round the tropics – but the pulse of this heart is weakening<figure><img src="https://images.theconversation.com/files/514181/original/file-20230308-18-wrt3cx.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6720%2C4476&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/aerial-view-fog-touching-sunlight-covered-2185967209">Jack-Sooksan/Shutterstock</a></span></figcaption></figure><p>Tropical forests are often referred to as the “lungs of the world”, describing the way their trees exchange gases with the atmosphere. By “breathing in” carbon dioxide and “breathing out” oxygen during photosynthesis, tropical forests remove about <a href="https://www.science.org/doi/10.1126/science.1201609">15%</a> of man-made carbon emissions and help to slow climate change. </p>
<p>This is not the only way tropical forests influence the climate, however. Anyone who has walked through a woodland on a hot day will know that trees have an immediate cooling effect. As well as shading the ground, trees draw water up from the soil and release it through tiny holes in their leaves called stomata. By doing this, trees cool their environment the same way evaporating sweat cools our bodies. </p>
<p>By pumping water from the land into the air, tropical forests also function like a heart. Water sucked up by tree roots is pumped back into the atmosphere where it forms clouds which eventually release the water as rain to be reabsorbed by trees. This cycle <a href="https://www.nature.com/articles/s41558-018-0177-y">can occur multiple times</a> as air moves over large forests. In fact, it’s critical to the survival of forests situated far from the ocean. In the Amazon and Congo river basins, somewhere between a <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021GL095136">quarter and a half</a> of all rainfall comes from moisture pumped from the forest itself. This recycling of moisture helps to maintain the large amounts of rainfall tropical forests need.</p>
<figure class="align-center ">
<img alt="The Amazon rainforest seen from a tower observatory." src="https://images.theconversation.com/files/514177/original/file-20230308-26-ivbp2d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514177/original/file-20230308-26-ivbp2d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514177/original/file-20230308-26-ivbp2d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514177/original/file-20230308-26-ivbp2d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514177/original/file-20230308-26-ivbp2d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514177/original/file-20230308-26-ivbp2d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514177/original/file-20230308-26-ivbp2d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rainforests are filled with trees drawing water from the earth to the air.</span>
<span class="attribution"><span class="source">Jess Baker</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The environmental scientist Antonio Nobre was the first to describe how the rainforest can function like a heart. In the <a href="https://www.science.org/content/article/controversial-russian-theory-claims-forests-don-t-just-make-rain-they-make-wind">biotic pump theory</a>, conceived by physicists Anastassia Makarieva and the late Victor Gorshkov, forests pump moisture-laden air currents deep into the interior of continents, helping to govern patterns of wind and rain far away.</p>
<p>Cutting down trees stops this transfer of water between the earth and the air and causes the surrounding area to heat up. People living near tropical forests are well aware of this effect, and scientists have since proved it using ground and <a href="https://www.science.org/doi/10.1126/science.aac8083">satellite</a> temperature measurements.</p>
<h2>The world’s heartbeat is slowing down</h2>
<p>Scientists have long understood the theory linking deforestation and decreasing rainfall. Frustratingly, the evidence to prove it has been harder to pin down. Rainfall varies so much from year to year and between regions that it has been challenging to conclusively demonstrate the impact of deforestation. </p>
<p>In a recent <a href="https://www.nature.com/articles/s41586-022-05690-1">study</a>, we used satellite measurements to investigate whether rainfall patterns changed after tropical forests were cleared. By comparing the rainfall over deforested regions with that over neighbouring forest we were able to isolate the impacts of forest loss. We found rainfall reduced after deforestation across all tropical regions, including the Amazon, Congo and in Southeast Asia. As the area of cleared forest expanded, rainfall decreased by a larger amount. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/amazon-fires-deforestation-has-a-devastating-heating-impact-on-the-local-climate-new-study-122914">Amazon fires: deforestation has a devastating heating impact on the local climate – new study</a>
</strong>
</em>
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<p>Our work suggests that so much tropical forest has been cleared globally over the past two decades that the tropical forest heartbeat has started to slow, resulting in less rainfall in the surrounding regions. We estimate that if tropical forests continue to be cleared, rainfall could decrease by an additional 10% by 2100 over the most heavily deforested regions. If enough forests are cleared and rainfall declines too much, a <a href="https://theconversation.com/is-the-amazon-rainforest-on-the-verge-of-collapse-178580">tipping point</a> could be reached where there is not enough rain to sustain the remaining forests.</p>
<figure class="align-center ">
<img alt="Fluffy clouds over distant forest at dusk." src="https://images.theconversation.com/files/514010/original/file-20230307-22-e1jbsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514010/original/file-20230307-22-e1jbsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514010/original/file-20230307-22-e1jbsp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514010/original/file-20230307-22-e1jbsp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514010/original/file-20230307-22-e1jbsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514010/original/file-20230307-22-e1jbsp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514010/original/file-20230307-22-e1jbsp.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">Deforestation threatens to break the tropical forest water pump.</span>
<span class="attribution"><span class="source">Callum Smith</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>How to value tropical forests</h2>
<p>Tropical nations are tasked with conserving their forests at the same time as developing their economies. Conservation is often perceived as a trade-off, but the local and regional climate benefits of healthy forests can reduce <a href="https://www.nature.com/articles/s43247-021-00275-8">heat stress</a>, boost <a href="https://www.nature.com/articles/s41467-021-22840-7">crop yields</a> and maintain stable water flows to predictably generate <a href="https://www.nature.com/articles/s41893-020-0492-y">hydroelectricity</a>. It can make more economic sense to protect forests rather than clear them. </p>
<p>If deforestation of the Amazon continues unabated, reductions in rainfall would cut hydropower production in the region to <a href="https://www.pnas.org/doi/full/10.1073/pnas.1215331110">25%</a> of its potential. Another recent <a href="https://www.nature.com/articles/s41467-021-22840-7">study</a> showed that reducing deforestation in the Amazon to sustain rainfall could prevent agricultural losses of US$1 billion annually. </p>
<p>As the crucial role of tropical forests in maintaining a cooler and wetter climate becomes better understood, the incentive to conserve them will grow.</p>
<p><em>This article was update on March 21 2023 to credit the work of Anastassia Makarieva, Victor Gorshkov and Antonio Nobre in developing and articulating the biotic pump theory.</em></p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
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<p class="fine-print"><em><span>Callum Smith receives funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (DECAF project, grant agreement no. 771492) and the Newton Fund through the Met Office Climate Science for Service Partnership Brazil.</span></em></p><p class="fine-print"><em><span>Dominick Spracklen receives funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (DECAF project, grant agreement no. 771492) and the Newton Fund through the Met Office Climate Science for Service Partnership Brazil.. </span></em></p><p class="fine-print"><em><span>Jess Baker receives funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (DECAF project, grant agreement no. 771492) and the Newton Fund through the Met Office Climate Science for Service Partnership Brazil</span></em></p>Calling the Amazon “the lungs of the world” overlooks the forest’s vital role in the water cycle.Callum Smith, PhD Candidate in Biosphere-Atmosphere Interactions, University of LeedsDominick Spracklen, Professor of Biosphere-Atmosphere Interactions, University of LeedsJess Baker, Postdoctoral Research Fellow, Tropical Climate, University of LeedsLicensed 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/1961682023-01-05T06:18:01Z2023-01-05T06:18:01ZPFAS: you can’t smell, see or taste these chemicals, but they are everywhere – and they’re highly toxic to humans<figure><img src="https://images.theconversation.com/files/500433/original/file-20221212-108108-c5cvm1.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C998%2C663&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">PFAS are persistent and spread through the atmosphere via hydrological processes.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/technician-use-professional-water-testing-equipment-1927772186">Chatchawal Phumkaew/Shutterstock</a></span></figcaption></figure><p>Humans perceive risk based largely on what we can see, smell and taste. Those senses serve us well when there are perceptible dangers to our health and the environment. </p>
<p>We can see and smell raw sewage and as such it is widely perceived as a risk to human and environmental health. The increasing concern of <a href="https://www.bbc.co.uk/news/uk-england-suffolk-63681034">scientists</a> about the presence of antibiotic-resistant bacteria in sewage has confirmed its actual risk. The Environment Agency also reports that pollution from sewage discharge is a leading cause of <a href="https://www.theguardian.com/environment/2020/sep/17/rivers-in-england-fail-pollution-tests-due-to-sewage-and-chemicals">poor river quality</a> in England.</p>
<p>But there are serious chemical threats, called perflouroalkyl and polyfluoroalkyl substances (PFAS), that we cannot perceive because they are colourless and odourless. Now present in our drinking water and natural ecosystems, high level exposure to these toxic chemicals can elicit a range of <a href="https://www.atsdr.cdc.gov/pfas/index.html">negative health effects in humans and wildlife</a>. These include an increased risk of certain cancers, kidney disease, cholesterol, reproductive and developmental disruption and a decreased vaccine response.</p>
<p>Humans cannot see, smell or taste PFAS in our water. Yet they are a serious <a href="https://pubs.acs.org/doi/10.1021/acs.est.2c02765">global threat</a>. The actual risk of PFAS is high, but in my experience as a scientist working on environmental pollution, many people are <a href="https://onlinelibrary.wiley.com/doi/10.1111/1467-9566.13253">unaware of them</a>.</p>
<h2>What are PFAS?</h2>
<p>First developed in the 1940s, PFAS are a large group of more than 4,000 synthetic chemicals. Commonly known as “forever chemicals”, their properties make them water and oil repellent and highly resistant to chemical and thermal breakdown. </p>
<p>They are therefore ingredients in various everyday products and as such are all around us. Non-stick frying pans, waterproof rain jackets, flame retardant sofas and carpets, <a href="https://chemtrust.org/wp-content/uploads/PFAS-UK-food-packaging_CHEMTrust_May2021.pdf">food packaging</a>, makeup and countless other items all contain these chemicals. </p>
<p>But PFAS can persist in the environment for hundreds or thousands of years. <a href="https://pubs.acs.org/doi/10.1021/es0710499">Research</a> estimates that it takes more than 1,000 years on average for the chemical concentration of some PFAS to reduce by 50% in soil.</p>
<h2>PFAS exposure</h2>
<p>Due to their persistence, PFAS have <a href="https://www.nature.com/articles/s41370-018-0094-1">steadily accumulated</a> in drinking water sources and oceans worldwide. This can happen as contaminated water leaks away from landfills into groundwater. PFAS in household items can also be washed into rivers and oceans through sewage systems. </p>
<figure class="align-center ">
<img alt="A garbage truck dumping waste on a landfill." src="https://images.theconversation.com/files/500441/original/file-20221212-109965-hv1x1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/500441/original/file-20221212-109965-hv1x1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500441/original/file-20221212-109965-hv1x1s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500441/original/file-20221212-109965-hv1x1s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500441/original/file-20221212-109965-hv1x1s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500441/original/file-20221212-109965-hv1x1s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500441/original/file-20221212-109965-hv1x1s.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">Contaminated water can leak from landfills into groundwater.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/garbage-truck-dumping-on-landfill-529228804">Dalibor Danilovic/Shutterstock</a></span>
</figcaption>
</figure>
<p>In 2019, at least one PFAS was detected in 60% of the public groundwater wells and 20% of the private groundwater wells used as drinking water sources in the <a href="https://pubs.acs.org/doi/10.1021/acs.est.1c04795">eastern USA</a>. And in England, the <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1012230/Poly-_and_perfluoroalkyl_substances_-sources_pathways_and_environmental_data_-_report.pdf">Environment Agency</a> analysed 470 freshwater sites between 2014 and 2019 and found PFAS contamination in 97% of them.</p>
<p>The freshwater contaminants then accumulate in plants and animals, where they can be <a href="https://www.frontiersin.org/articles/10.3389/ftox.2020.601149/full">transferred</a> to humans via ingestion.</p>
<p>In the city of Charleston in South Carolina, scientists <a href="https://www.sciencedirect.com/science/article/pii/S0013935119300222#:%7E:text=PFOS%20was%20predominant%20PFAS%20compound%20in%20fish%20muscle%20and%20whole%20fish.&text=%E2%88%91PFAS%20concentrations%20were%20higher,than%20fillets%20by%202%E2%80%933X.&text=Frequent%20consumption%20of%20wild%20fish%20may%20pose%20health%20risks%20to%20local%20population.&text=PFOS%20levels%20exceeded%20wildlife%20protective,fish%2C%20a%20concern%20for%20dolphins.">recorded</a> concentrations of 11 PFAS in six species of fish. Levels of the most abundant chemical recorded in each species – perfluorooctane sulfonate – exceeded wildlife protective guidelines in 83% of whole fish examined. The consumption of wild fish therefore represents a serious health concern for the local population.</p>
<h2>Here to stay</h2>
<p>Most people in the world are likely to have been exposed to PFAS. In 2012, more than <a href="https://www.mdpi.com/1660-4601/12/6/6098">97% of Americans</a> were estimated to have detectable levels of PFAS in their blood for example.</p>
<p>But, unlike most other chemical pollutants, PFAS are able to cycle continuously in hydrological processes and spread throughout the atmosphere. Scientists have, for example, <a href="https://pubs.acs.org/doi/10.1021/acs.est.2c02765">recorded</a> concentrations of PFAS in rainwater almost everywhere on Earth. This means that contamination may be largely irreversible. </p>
<p>Distributed by the water cycle, PFAS have been allowed to contaminate remote corners of the planet and negatively impact its wildlife. In Antarctica, accumulations of one type of PFAS – perfluorobutanoic acid – in snow <a href="https://pubs.acs.org/doi/10.1021/acs.est.2c02592">increased</a> more than 200-fold between 1957 and 2015.</p>
<p><a href="https://pubs.acs.org/doi/10.1021/acs.est.1c01645">Researchers</a> have also found high concentrations of PFAS in Arctic algae. Algae are an important food source for zooplankton, with their contamination feeding upwards through the food chain to fish and shrimp, then seals, and finally to apex predators such as polar bears. A study of East Greenland polar bears revealed that PFAS contamination can disrupt a <a href="https://www.sciencedirect.com/science/article/pii/S0160412016302732">polar bear’s</a> hormone system, which may negatively impact reproduction. </p>
<figure class="align-center ">
<img alt="Two polar bear cubs eating a fish." src="https://images.theconversation.com/files/500436/original/file-20221212-112724-p3m533.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/500436/original/file-20221212-112724-p3m533.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=344&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500436/original/file-20221212-112724-p3m533.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=344&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500436/original/file-20221212-112724-p3m533.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=344&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500436/original/file-20221212-112724-p3m533.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=432&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500436/original/file-20221212-112724-p3m533.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=432&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500436/original/file-20221212-112724-p3m533.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=432&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">PFAS can be passed through the food chain.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/polar-bear-cubs-eat-fish-1930967618">evaurban/Shutterstock</a></span>
</figcaption>
</figure>
<p>For many people, current PFAS exposure levels are unlikely to be high enough to warrant serious concern. But exposure in <a href="https://www.epa.gov/pfas/our-current-understanding-human-health-and-environmental-risks-pfas">some occupations</a>, including firefighting and chemical manufacturing and processing, are likely to be much higher. As will the risk for people whose <a href="https://www.nature.com/articles/s41370-018-0099-9">drinking water</a> or food sources have been contaminated.</p>
<p>Science, and even <a href="https://www.theguardian.com/film/2020/feb/27/dark-waters-review-todd-haynes-mark-ruffalo-west-virginia-dupont-poison-">Hollywood</a>, has warned us of the global chemical threat posed by PFAS. Yet many of us do not perceive them to be a threat. </p>
<p>This may be due to the fact that PFAS are an “invisible” threat and not as obvious as sewage or plastic pollution. But these toxic chemicals have accumulated in many of our water sources and are now interfering with natural ecosystems. Governments, scientists and the media must improve their communication of the risks associated with PFAS.</p><img src="https://counter.theconversation.com/content/196168/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Patrick Byrne receives funding from the Natural Environment Research Council.</span></em></p>Toxic synthetic chemicals, called PFAS, are a serious threat to humans and wildlife – but many people are unaware of them.Patrick Byrne, Reader in Hydrology and Environmental Pollution, Liverpool John Moores UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1908862022-11-14T13:27:07Z2022-11-14T13:27:07ZWhat is hydroelectric energy and how does it work?<figure><img src="https://images.theconversation.com/files/493383/original/file-20221103-21-bvfyk2.jpg?ixlib=rb-1.1.0&rect=0%2C2%2C1997%2C1326&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Seli’š Ksanka Qlispe’ Dam provides enough electricity for about 147,000 homes in the Flathead Indian Reservation in Montana.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:SQK_Dam_DSC_3657.jpg">Martina Nolte via Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>What is hydroelectric energy and how does it work? – Luca, age 13, Boston, Massachusetts</strong></p>
</blockquote>
<p>If you’ve ever observed a river rushing down a mountain or played in the waves at the beach, you’ve felt that moving water contains a lot of energy. A river can push you and your kayak downstream, sometimes very quickly, and waves crashing into you at the beach can knock you back, or even knock you over.</p>
<p>There is a <a href="https://www.energy.gov/eere/water/history-hydropower">long history of harnessing the energy in the flowing waters of rivers</a> to do useful work. For centuries, people used water power <a href="https://thekidshouldseethis.com/post/watermill-demonstration-video-flour-water-power">to grind grain to make flour and meal</a>. In modern times, people use water power to generate clean electricity to help power buildings, factories and even cars.</p>
<h2>Energy in flowing waters</h2>
<p>The energy in these moving waters comes from gravity. As part of the Earth’s water cycle, water evaporates from the Earth’s surface or is released from plants. When the released water vapor is carried to cooler, higher altitudes like mountainous regions, it condenses into cloud droplets. When these cloud droplets become big enough, they fall from the sky as precipitation, either as a liquid (rain) or, if it is cold enough, as a solid (snow). Over land, precipitation tends to fall on high altitude areas at first.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/490173/original/file-20221017-13-qvvkh1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graphic showing land, a river, a mountain, sun and clouds" src="https://images.theconversation.com/files/490173/original/file-20221017-13-qvvkh1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490173/original/file-20221017-13-qvvkh1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=496&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490173/original/file-20221017-13-qvvkh1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=496&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490173/original/file-20221017-13-qvvkh1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=496&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490173/original/file-20221017-13-qvvkh1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=623&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490173/original/file-20221017-13-qvvkh1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=623&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490173/original/file-20221017-13-qvvkh1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=623&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 water cycle.</span>
<span class="attribution"><a class="source" href="https://www.weather.gov/jetstream/hydro">National Weather Service</a></span>
</figcaption>
</figure>
<p>The pull of gravity causes the water to flow. If the water falls as rain, some of it flows downhill into natural channels and becomes rivers. If the water falls as snow, it will slowly melt into water as temperatures warm and follow the same paths. The rivers that form consist of water from precipitation starting at high altitudes and flowing down the steep slopes of mountains.</p>
<h2>Converting flowing water to electricity</h2>
<p>Hydropower facilities capture the energy in flowing water by using a device called a turbine. As water runs over the blades of a turbine – kind of like a giant pinwheel – they spin. This spinning turbine is connected to a shaft that spins inside a device called a <a href="https://www.explainthatstuff.com/generators.html">generator</a>, which uses an effect called <a href="https://www.youtube.com/watch?v=S3Qwf4P6x9w">induction</a> to convert energy in the spinning shaft to electricity.</p>
<p>There are two main kinds of hydropower facilities. The first kind is called a “run-of-the-river” hydropower facility. These facilities consist of a channel to divert water flow from a river to a turbine. The electricity production from the turbine follows the timing of the river flow. When a river is running full with lots of spring meltwater, it means the turbine can produce more electricity. Later in the summer, when the river flow decreases, so does the turbine’s electricity production. These facilities are typically small and simple to construct, but there is limited ability to control their output.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/490177/original/file-20221017-26-3w8wui.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a graphic showing a river and water diverted to a series of structures" src="https://images.theconversation.com/files/490177/original/file-20221017-26-3w8wui.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490177/original/file-20221017-26-3w8wui.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=455&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490177/original/file-20221017-26-3w8wui.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=455&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490177/original/file-20221017-26-3w8wui.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=455&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490177/original/file-20221017-26-3w8wui.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=572&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490177/original/file-20221017-26-3w8wui.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=572&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490177/original/file-20221017-26-3w8wui.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=572&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 run-of-the-river hydropower facility.</span>
<span class="attribution"><a class="source" href="https://www.energy.gov/eere/water/types-hydropower-plants">U.S. Department of Energy</a></span>
</figcaption>
</figure>
<p>The second kind is called a “reservoir” or “dam” hydropower facility. These facilities use a dam to hold back the flow of a river and create an artificial lake behind the dam. Hydropower dams have intakes that control how much water flows through passages inside the dam. Turbines at the bottom of these passages convert the flowing water into electricity. </p>
<p>To produce electricity, the dam operator releases water from the artificial lake. This water speeds up as it falls down from the intakes near the top of the dam to the turbines near the bottom. The water that exits the turbines is released back into the river downstream. These reservoir hydropower facilities are usually large and can affect river habitats, but they can also produce a lot of electricity in a controllable manner.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/490178/original/file-20221017-18-c0dtqn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a graphic showing a cutaway view of a dam with a turbine at its base" src="https://images.theconversation.com/files/490178/original/file-20221017-18-c0dtqn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490178/original/file-20221017-18-c0dtqn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=363&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490178/original/file-20221017-18-c0dtqn.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=363&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490178/original/file-20221017-18-c0dtqn.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=363&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490178/original/file-20221017-18-c0dtqn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=456&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490178/original/file-20221017-18-c0dtqn.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=456&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490178/original/file-20221017-18-c0dtqn.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=456&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 dam-based hydropower facility.</span>
<span class="attribution"><a class="source" href="https://www.energy.gov/eere/water/types-hydropower-plants">U.S. Department of Energy</a></span>
</figcaption>
</figure>
<h2>The future of hydropower</h2>
<p>Hydropower depends on the availability of water in flowing rivers. As climate change affects the water cycle, some regions may have less precipitation and consequently <a href="https://thebulletin.org/2021/08/hydroelectric-drought-how-climate-change-complicates-californias-plans-for-a-carbon-free-future/">less hydropower generation</a>. </p>
<p>Also, making electricity isn’t the only thing dam operators have to think about when they decide how much water to let through. They have to make sure to keep some water behind the dam for people to use and let enough water through to preserve the river habitat below the dam.</p>
<p>Hydropower can also play a role in limiting climate change because it is a form of renewable electricity. Hydropower facilities can increase and decrease their electricity production to fill in gaps in wind and solar generation.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/190886/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brian Tarroja 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>How does flowing water make electricity? An engineer explains hydroelectric generation.Brian Tarroja, Associate Professional Researcher and Lecturer of Civil and Environmental Engineering, University of California, IrvineLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1941412022-11-10T13:42:59Z2022-11-10T13:42:59ZWhat is a flash drought? An earth scientist explains<figure><img src="https://images.theconversation.com/files/533774/original/file-20230623-23-ed4we5.jpg?ixlib=rb-1.1.0&rect=22%2C0%2C4962%2C3196&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">As of June 20, 2023, 64% of the U.S. corn crop faced moderate or more intense drought.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/drought-stricken-corn-on-the-mcintosh-farm-in-missouri-news-photo/150263135">Jim Watson/AFP/GettyImages</a></span></figcaption></figure><p>Many people are familiar with <a href="https://theconversation.com/what-is-a-flash-flood-a-civil-engineer-explains-187961">flash floods</a> – torrents that develop quickly after heavy rainfall. But there’s also such a thing as a flash drought, and these sudden, extreme dry spells are becoming a big concern <a href="https://theconversation.com/farmers-face-a-soaring-risk-of-flash-droughts-in-every-major-food-growing-region-in-coming-decades-new-research-shows-206265">for farmers</a> and water utilities.</p>
<p>Flash droughts start and intensify quickly, over periods of weeks to months, compared to years or decades for conventional droughts. Still, they can cause substantial economic damage, since communities have less time to prepare for the impacts of a rapidly evolving drought. In 2017, a flash drought in Montana and the Dakotas damaged crops and grasses that served as forage for cattle, causing <a href="https://www.drought.gov/documents/flash-drought-lessons-learned-2017-drought-across-us-northern-plains-and-canadian">US$2.6 billion in agricultural losses</a>.</p>
<p>Flash droughts also can increase wildfire risks, <a href="https://www.drought.gov/dews/northeast">cause public water supply shortages and reduce stream flow</a>, which harms fish and other aquatic life.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/533776/original/file-20230623-25-ed4we5.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of drought regions in U.S. with central Plains highlighted." src="https://images.theconversation.com/files/533776/original/file-20230623-25-ed4we5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/533776/original/file-20230623-25-ed4we5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=452&fit=crop&dpr=1 600w, https://images.theconversation.com/files/533776/original/file-20230623-25-ed4we5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=452&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/533776/original/file-20230623-25-ed4we5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=452&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/533776/original/file-20230623-25-ed4we5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=568&fit=crop&dpr=1 754w, https://images.theconversation.com/files/533776/original/file-20230623-25-ed4we5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=568&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/533776/original/file-20230623-25-ed4we5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=568&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A developing flash drought in the central U.S. covered 64% of corn territory and 57% of soybean territory in late June 2023. Areas marked ‘S’ are under short-term drought; ‘L’ signifies long-term drought.</span>
<span class="attribution"><a class="source" href="https://www.usda.gov/sites/default/files/documents/AgInDrought.pdf">U.S. Drought Monitor via USDA</a></span>
</figcaption>
</figure>
<h2>Less rain, warmer air</h2>
<p>Flash droughts typically result from a combination of lower-then-normal precipitation and higher temperatures. Together, these factors reduce overall land surface moisture. </p>
<p>Water constantly cycles between land and the atmosphere. Under normal conditions, moisture from rainfall or snowfall accumulates in the soil during wet seasons. Plants draw water up through their roots and release water vapor into the air through their leaves, a process called <a href="https://www.usgs.gov/special-topics/water-science-school/science/evapotranspiration-and-water-cycle">transpiration</a>. Some moisture also evaporates directly from the soil into the air. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/493942/original/file-20221107-16833-ug4zxf.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graphic showing precipitation, evaporation and transpiration between soil and the atmosphere" src="https://images.theconversation.com/files/493942/original/file-20221107-16833-ug4zxf.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/493942/original/file-20221107-16833-ug4zxf.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=503&fit=crop&dpr=1 600w, https://images.theconversation.com/files/493942/original/file-20221107-16833-ug4zxf.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=503&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/493942/original/file-20221107-16833-ug4zxf.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=503&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/493942/original/file-20221107-16833-ug4zxf.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=632&fit=crop&dpr=1 754w, https://images.theconversation.com/files/493942/original/file-20221107-16833-ug4zxf.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=632&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/493942/original/file-20221107-16833-ug4zxf.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=632&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Water constantly circulates between soil and the atmosphere – sometimes directly, sometimes via plants.</span>
<span class="attribution"><a class="source" href="https://www.usgs.gov/media/images/evapotranspiration-sum-plant-transpiration-and-evaporation">USGS</a></span>
</figcaption>
</figure>
<p>Scientists refer to the amount of water that could be transferred from the land to the atmosphere as <a href="https://www.climate.gov/news-features/feed/evaporative-demand-increase-across-lower-48-means-less-water-supplies-drier">evaporative demand</a> – a measure of how “thirsty” the atmosphere is. Higher temperatures increase evaporative demand, which makes water evaporate faster. When soil contains enough moisture, it can meet this demand. </p>
<p>But if soil moisture is depleted – for example, if precipitation drops below normal levels for months – then evaporation from the land surface can’t provide all the moisture that a thirsty atmosphere demands. Reduced moisture at the surface increases surface air temperatures, drying out the soil further. These processes <a href="https://doi.org/10.1038/s41558-020-0709-0">amplify each other</a>, making the area increasingly hot and dry.</p>
<h2>Moist regions can have flash droughts</h2>
<p>Flash droughts started receiving more attention in the U.S. after <a href="https://doi.org/10.1175/BAMS-D-17-0149.1">notable events in 2012, 2016 and 2017</a> that reduced crop yields and increased wildfire risks. In 2012, areas in the Midwest that had near-normal precipitation conditions through May fell into severe drought conditions in June and July, causing more than <a href="https://www.ncei.noaa.gov/access/billions/">$30 billion in damages</a>. </p>
<p>New England, typically one of the <a href="https://www.climate.gov/news-features/featured-images/new-maps-annual-average-temperature-and-precipitation-us-climate">wetter U.S. regions</a>, experienced a flash drought in the summer of 2022, with areas including Boston and Rhode Island <a href="https://www.wbur.org/news/2022/08/26/climate-change-flash-drought-massachusetts">receiving only a fraction of their normal rainfall</a>. Across Massachusetts, critically low water levels forced towns to issue <a href="https://www.mass.gov/info-details/outdoor-water-use-restrictions-for-cities-towns-and-golf-courses">mandatory water restrictions</a> for residents.</p>
<h2>Planning for flash droughts in a changing climate</h2>
<p>Conventional droughts, like the <a href="https://drought.unl.edu/dustbowl/">Dust Bowl of the 1930s</a> or the current <a href="https://www.theguardian.com/environment/2022/sep/12/us-west-megadrought-climate-disaster">22-year drought across the southwestern U.S.</a>, develop over periods of years. Scientists rely on monitoring and prediction tools, such as measurements of temperature and rainfall, as well as models, to forecast their evolution. </p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/CW7X5M_lqcT/?utm_source=ig_web_copy_link\u0026igshid=MzRlODBiNWFlZA==","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<p>Predicting flash drought events that occur on monthly to weekly time scales is much harder with current data and tools, largely due to the <a href="https://doi.org/10.1029/2019EA000586">chaotic nature of weather and limitations in weather models</a>. That’s why weather forecasters don’t typically make projections <a href="https://www.washingtonpost.com/weather/2019/11/07/science-says-specific-weather-forecasts-cant-be-made-more-than-ten-days-advance/">beyond 10 days</a> – there is a lot of variation in what can happen over longer time spans.</p>
<p>And climate patterns can shift from year to year, adding to the challenge. For example, Boston had <a href="https://twitter.com/NWSBoston/status/1552127339277889536">a very wet summer in 2021</a> before its very dry summer in 2022.</p>
<p>Scientists expect climate change to make precipitation <a href="https://doi.org/10.1038/s41598-017-17966-y">even more variable</a>, especially in wetter regions like the U.S. Northeast. This will make it more difficult to forecast and prepare for flash droughts well in advance. </p>
<p>But new monitoring tools that measure evaporative demand can provide <a href="https://doi.org/10.1175/BAMS-D-14-00219.1">early warnings</a> for regions experiencing abnormal conditions. Information from these systems can give farmers and utilities sufficient lead time to adjust their operations and minimize their risks. </p>
<p><em>This is an updated version of an article originally published on Nov. 10, 2022.</em></p><img src="https://counter.theconversation.com/content/194141/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Antonia Hadjimichael receives funding from the U.S. Department of Energy</span></em></p>Flash droughts can develop within a few weeks, causing water shortages, damaging crops and worsening fire risks.Antonia Hadjimichael, Assistant Professor of Geosciences, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1925652022-11-01T15:48:48Z2022-11-01T15:48:48ZThe Horn of Africa has had years of drought, yet groundwater supplies are increasing – why?<figure><img src="https://images.theconversation.com/files/492348/original/file-20221028-64500-j3d8z7.jpg?ixlib=rb-1.1.0&rect=14%2C441%2C4955%2C3300&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Harvepino / shutterstock</span></span></figcaption></figure><p>The Horn of Africa – which includes Somalia, Ethiopia, Kenya and some surrounding countries – has been hit by increasingly frequent and devastating droughts. Despite this, it seems the region has an increasing amount of groundwater. And this water could help support drought-stricken rural communities. </p>
<p>That’s the key finding from our <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2022GL099299">new research</a>, in which we discovered that while overall rainfall is decreasing, an increase in “high-intensity” rainfall has led to more water being stored deep underground. It’s a paradoxical finding, yet one that may help one of the world’s most vulnerable regions adapt to climate change. </p>
<p>In the Horn of Africa, rural communities live in a constant state of water scarcity punctuated by frequent periods of <a href="https://theconversation.com/somalia-four-lessons-from-past-experience-of-dealing-with-famine-192067">food insecurity</a>. People there rely on the “long rains” between March and May and the “short rains” between October and December to support their lives and livelihoods. </p>
<p>As we write this, the region’s drylands are experiencing a <a href="https://public.wmo.int/en/media/news/greater-horn-of-africa-faces-5th-failed-rainy-season">fifth consecutive season of below-average rainfall</a>. This has left <a href="https://news.un.org/en/story/2022/08/1125552">50 million people in acute food insecurity</a>. The droughts have caused water shortages, livestock deaths, crop failures, conflict and even <a href="https://www.cambridge.org/core/journals/bjpsych-international/article/mental-health-and-climate-change-in-africa/65A414598BA1D620F4208A9177EED94B">mental health challenges</a>. </p>
<p>The drought is so severe that it is even affecting <a href="https://edition.cnn.com/2022/10/05/africa/kenya-drought-wildlife-climate-intl-cmd/index.html">zebras</a>, <a href="https://www.theguardian.com/world/2021/dec/14/six-dead-giraffes-kenya-drought-horror-captured-picture">giraffes</a> and other wildlife, as all surface waters are drying up and edible vegetation is becoming scarce. Worryingly, a sixth failed rainy season has already been <a href="https://blog.chc.ucsb.edu/?p=1240">predicted</a> for March to May 2023. </p>
<h2>Long rains down, short rains up</h2>
<p>In a <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2022GL099299">new paper</a> we investigated changes in seasonal rainfall in the Horn of Africa over the past 30 years. We found the total rainfall within the “long rains” season is declining, perhaps related to the <a href="https://rmets.onlinelibrary.wiley.com/doi/10.1002/qj.3266">warming of a particular part of the Pacific Ocean</a>. However, rainfall is increasing in the “short rains”. That’s largely due to a climate phenomenon known as the <a href="https://www.bbc.co.uk/news/science-environment-50602971">Indian Ocean Dipole</a>, when a warmer-than-usual Indian Ocean produces higher rainfall in east Africa, similar to El Niño in the Pacific.</p>
<p>We then investigated what these rainfall trends mean for water stored below ground. Has it decreased in line with declining “long rains”, or risen due to the increasing “short rains”?</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/492790/original/file-20221101-26-5aqn3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of East Africa" src="https://images.theconversation.com/files/492790/original/file-20221101-26-5aqn3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/492790/original/file-20221101-26-5aqn3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=682&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492790/original/file-20221101-26-5aqn3j.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=682&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492790/original/file-20221101-26-5aqn3j.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=682&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492790/original/file-20221101-26-5aqn3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=857&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492790/original/file-20221101-26-5aqn3j.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=857&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492790/original/file-20221101-26-5aqn3j.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=857&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 Horn of Africa borders the Red Sea, the Gulf of Aden and the Indian Ocean.</span>
<span class="attribution"><span class="source">Peter Hermes Furian / shutterstock</span></span>
</figcaption>
</figure>
<p>To do this we made use of a pair of satellites which orbit repeatedly and detect small changes in the Earth’s gravitational field that can be interpreted as <a href="https://edo.jrc.ec.europa.eu/documents/factsheets/factsheet_grace_tws_anomaly.pdf">changes in the mass of water storage</a>. If there’s a significant increase in water storage underground, then the satellite will record a stronger gravity field at that location compared to the previous measurement, and vice versa. From this, the mass of water added or lost in that location can be determined. </p>
<p>Using these <a href="https://www.jpl.nasa.gov/missions/gravity-recovery-and-climate-experiment-grace">satellite-derived</a> estimates, we found that water storage has been increasing in recent decades. The increase correlates with the increasing “short rains”, and has happened despite the “long rains” getting drier.</p>
<p>Given that the long rains deliver more seasonal rain than the short rains, we wanted to understand the paradoxical finding that underground water is increasing. A clue is given by examining how rainfall is converted into groundwater in drylands. </p>
<p>When rain is light and drizzly, much of the water that reaches the ground dampens the soil surface and soon evaporates back into the warm, dry atmosphere. To become groundwater, rainfall instead needs to be intense enough so that water will quickly infiltrate deep into the soil. This mostly happens when lots of rain falls at once and causes dry riverbeds to fill with water which can then <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/hyp.13847">leak into underground aquifers</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/492791/original/file-20221101-22-62x1oe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="People stand in river, rainy sky." src="https://images.theconversation.com/files/492791/original/file-20221101-22-62x1oe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/492791/original/file-20221101-22-62x1oe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/492791/original/file-20221101-22-62x1oe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/492791/original/file-20221101-22-62x1oe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/492791/original/file-20221101-22-62x1oe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/492791/original/file-20221101-22-62x1oe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/492791/original/file-20221101-22-62x1oe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Heavy rains fill a dry river bed in the Somali region of Ethiopia.</span>
<span class="attribution"><span class="source">Stanley Dullea / shutterstock</span></span>
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</figure>
<p>These most intense rainfall events are increasing in the “short rains”, in line with the overall increase in total rain in that season. And despite a decrease in overall rainfall in the “long rains”, intense rainfall has remained consistently high over time. This means that both rainy seasons have enough intense rainfall to increase the amount of water stored underground. </p>
<p>Finally, we demonstrated that the increasing water storage in this region is not connected to any rise in soil moisture near the surface. It therefore represents “banked” water that resides deep below ground and likely contributes to a growing regional groundwater aquifer in this region. </p>
<h2>Groundwater can help people adapt to climate change</h2>
<p>While <a href="https://fews.net/east-africa">early warning networks</a> and <a href="https://www.unicef.org.uk/donate/east-africa-crisis/?https://www.unicef.org.uk/donate/east-africa-crisis/&gclid=Cj0KCQjwy5maBhDdARIsAMxrkw2qNJBJSlL4Kl1CIwwB4p4nhyK5PWQnqvPy1J4FeyXsM-zmF9hqWV4aAnTcEALw_wcB">humanitarian organisations</a> focus on the urgent impacts of drought, our new research points to a silver lining that may support long-term climate adaptation. Those rising groundwater supplies we have identified may potentially be exploited to support people in rural areas whose food and water are increasingly insecure. </p>
<p>But there are some caveats. First, we have not assessed the depth of the available groundwater across the region, but we suggest that the water table is shallow enough to be affected by seasonal rainfall. This means it may also be shallow enough to support new bore holes to extract it. Second, we do not know anything about the quality of the stored groundwater and whether it can be deemed suitable for drinking. Finally, we do not know exactly what will happen if the most extreme droughts of the past few seasons continue and both long and short rains fail, causing intense rainfall to decrease too. </p>
<p>Nevertheless, our findings point to the need for extensive groundwater surveys across the Horn of Africa drylands to ascertain whether this increasing water resource may be viable enough to offset the devastating droughts. Groundwater could potentially irrigate fields and provide drinking water for humans and livestock, as part of a strategy to help this vulnerable region adapt to the effects of climate change.</p><img src="https://counter.theconversation.com/content/192565/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Singer received funding for this work from the European Union, The Royal Society, and UK Research and Innovation. </span></em></p><p class="fine-print"><em><span>Katerina Michaelides receives funding from the Royal Society, the EU Horizon 2020 funding program and UKRI. </span></em></p><p class="fine-print"><em><span>Markus Adloff received funding from UK Research and Innovation.</span></em></p>High intensity rain has actually increased, which is topping up underground water stores.Michael Singer, Professor in Physical Geography (Hydrology and Geomorphology), Cardiff UniversityKaterina Michaelides, Associate Professor, School of Geographical Sciences , University of BristolMarkus Adloff, PostDoctoral Researcher, Earth System Modelling, University of BernLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1892702022-08-30T17:08:45Z2022-08-30T17:08:45ZRivers worldwide are running dry – here’s why and what we can do about it<p>Rivers around the world have been drying up recently. The <a href="https://www.reuters.com/world/europe/frances-river-loire-sets-new-lows-drought-dries-up-its-tributaries-2022-08-17/">Loire</a> in France broke records in mid-August for its low water levels, while photos circulating online show the mighty <a href="https://twitter.com/unsc1325/status/1560742351424720897?s=21&t=7kIuG1joccAGQJ7K5MbU-Q">Danube, Rhine, Yangtze and Colorado</a> rivers all but reduced to trickles.</p>
<p>It is not just rivers that are running low but the reservoirs they replenish, leading to water shortages in many parts of the world including the UK. Yet floods have wreaked havoc in many of these rivers in the last decade, in some cases only a few months before the recent drought. So what is happening to them?</p>
<p>Climate change has many guises. The Earth system is interdependent, so when something changes, it cascades to affect lots of other things. When atmospheric temperatures rise, weather patterns affect where, when, and how much rain will fall. Therefore, water distribution changes across regions, and the rivers adapt accordingly, which affects how much freshwater is available for people to drink.</p>
<p>Freshwater makes up a tiny fraction of all water on the planet, and much of it is locked away in ice. While this has been true for as long as humans have been around, climate change is altering where freshwater is found: such that, in general, places with plenty are getting more while places with little are getting less.</p>
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Read more:
<a href="https://theconversation.com/human-disruption-to-earths-freshwater-cycle-has-exceeded-the-safe-limit-our-research-shows-182562">Human disruption to Earth's freshwater cycle has exceeded the safe limit, our research shows</a>
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<p>Differences in how water is distributed are increasingly stark, not just across regions but also over time. When a river’s behaviour becomes more extreme, consistently breaking records for highest and lowest water levels, river scientists say it is becoming more “flashy”. Some desert rivers are very flashy and only flow at certain times of the year.</p>
<p>A river’s flashiness reflects how much water is available, which depends on the climate. Though a river can have higher or lower flows for longer periods of time, it may still transport about the same volume of water over a year.</p>
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<p>Management strategies are typically designed according to how a river has behaved in the past. But we must take account of the full extremities of how rivers can flow, because how it seems now is not how it has always been, and not how it always will be.</p>
<h2>Flashy futures?</h2>
<p>Rivers are wild watercourses that have shaped the land for billions of years, which is a lot longer than humans have been around. Rivers naturally morph as their environment changes, which includes the climate, rainfall, vegetation, sea level and many other things. Geologists can read clues of these changes from rocks and landscapes. </p>
<p>We tend to adapt rivers to us more than we adapt to them. Engineering measures limit their ability to make natural changes such as flooding or forging a new course. Urban rivers may be encased in concrete and their flow somewhat straightened, while drains in paved cityscapes rush water to rivers without it needing to drain slowly through soil.</p>
<figure class="align-center ">
<img alt="Water flowing into a sewer drain during heavy rain on a suburban street." src="https://images.theconversation.com/files/481075/original/file-20220825-22-o2fyvk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/481075/original/file-20220825-22-o2fyvk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/481075/original/file-20220825-22-o2fyvk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/481075/original/file-20220825-22-o2fyvk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/481075/original/file-20220825-22-o2fyvk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/481075/original/file-20220825-22-o2fyvk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/481075/original/file-20220825-22-o2fyvk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Concrete paving pools water that drainage systems then rush towards rivers.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/heavy-rain-falling-on-street-flowing-1483443854">Feng Cheng/Shutterstock</a></span>
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</figure>
<p>Such human-engineered changes can make rivers flashier. If there is a drought, water leaves the land faster while if there is a lot of rain, it accumulates in one place more rapidly. As rivers respond to global change, we need to find ways to prioritise their natural coping strategies in how we manage them. </p>
<p>That could involve so-called slow-water strategies such as China’s “<a href="https://www.theguardian.com/environment/2022/jun/07/slow-water-urban-floods-drought-china-sponge-cities">sponge cities</a>”: urban areas with abundant trees, ponds and parks to absorb water and alleviate droughts and floods.</p>
<p>There is a lot of work ahead of us to ensure that we cherish and manage a stable and safe supply of water from our increasingly unruly rivers. Respecting and working with nature can ensure enough clean water – not just for humans, but for all living creatures and the environment too.</p>
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<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">
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<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
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<p class="fine-print"><em><span>Catherine E. Russell receives funding from a Fulbright-Lloyd's Scholarship and UNESCO IGCP Project 732.</span></em></p>The world’s great rivers are see-sawing from trickles to floods.Catherine E. Russell, Fulbright-Lloyd's Visiting Scholar, University of New Orleans & Honorary Researcher, University of LeicesterLicensed 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/1825622022-06-27T14:20:26Z2022-06-27T14:20:26ZHuman disruption to Earth’s freshwater cycle has exceeded the safe limit, our research shows<figure><img src="https://images.theconversation.com/files/466060/original/file-20220530-20-zvmbva.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6613%2C3720&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/extreme-drought-cornfield-under-hot-sun-1129539992">Scott Book/Shutterstock</a></span></figcaption></figure><p>Green water – the rainwater available to plants in the soil – is indispensable for life on and below the land. But in a <a href="https://www.nature.com/articles/s43017-022-00287-8">new study</a>, we found that widespread pressure on this resource has crossed a critical limit.</p>
<p>The planetary boundaries framework – a concept that scientists <a href="https://www.nature.com/articles/461472a">first discussed in 2009</a> – identified nine processes that have remained remarkably steady in the Earth system over the last 11,700 years. These include a relatively stable global climate and an intact biosphere that have allowed civilisations based on agriculture to thrive. Researchers proposed that each of these processes has a boundary that, once crossed, puts the Earth system, or substantial components of it, at risk of upset.</p>
<p>A <a href="https://www.science.org/doi/10.1126/science.1259855">comprehensive scientific assessment</a> in 2015 found that human activity has already breached four of the planetary boundaries. Greenhouse gas emissions are brewing a <a href="https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_SummaryForPolicymakers.pdf">hotter climate</a>, the <a href="https://www.pnas.org/doi/10.1073/pnas.1922686117">sixth mass extinction</a> of species is unpicking the web of life that makes up the global biosphere, intensive farming is <a href="https://e360.yale.edu/features/can-the-world-find-solutions-to-the-nitrogen-pollution-crisis">polluting the environment</a> and natural habitats are being <a href="https://www.carbonbrief.org/land-use-change-has-affected-almost-a-third-of-worlds-terrain-since-1960/">destroyed</a> on a significant scale. Earlier in 2022, researchers announced that a fifth planetary boundary had been <a href="https://theconversation.com/chemical-pollution-exceeds-safe-planetary-limit-researcher-q-a-on-consequences-for-life-on-earth-175256">crossed</a> with the emission and accumulation of <a href="https://pubs.acs.org/doi/10.1021/acs.est.1c04158">chemical pollution and plastics</a>. </p>
<p>So far, it has been suggested that human use of freshwater is still <a href="https://www.science.org/doi/10.1126/science.1259855">within safe limits globally</a>. But earlier assessments only considered the extraction of what is called blue water – that which flows in rivers and resides in underground aquifers. Even then, <a href="https://www.sciencedirect.com/science/article/abs/pii/S1877343513001498?via%3Dihub">regional boundaries</a> are likely to have been crossed in many river basins due to a sixfold increase in the extraction of blue water <a href="https://gmd.copernicus.org/articles/9/175/2016/">over the past century</a>. Besides irrigating crops to sate growing demand from people and livestock, population growth and higher standards of living have raised global <a href="https://www.sciencedirect.com/science/article/abs/pii/S0959378012001318">domestic and industrial water consumption</a>, disrupting aquatic ecosystems and <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0032688">decimating</a> the life within them.</p>
<p>By including green water in our assessment, we found that freshwater’s ability to sustain a stable Earth system is even more threatened than first reported.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/465324/original/file-20220525-14-qgqzqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/465324/original/file-20220525-14-qgqzqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465324/original/file-20220525-14-qgqzqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=567&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465324/original/file-20220525-14-qgqzqv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=567&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465324/original/file-20220525-14-qgqzqv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=567&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465324/original/file-20220525-14-qgqzqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=713&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465324/original/file-20220525-14-qgqzqv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=713&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465324/original/file-20220525-14-qgqzqv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=713&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 crossing of planetary boundaries could destabilise humanity’s safe operating space in the Earth system.</span>
<span class="attribution"><span class="source">Azote/Stockholm Resilience Centre</span></span>
</figcaption>
</figure>
<h2>Red alert for green water</h2>
<p>Radiation from the sun evaporates green water in the soil, cooling the environment and returning moisture to the atmosphere where it forms <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010WR009127">clouds and rain</a>. This cycle sustains some of Earth’s most important ecosystems, such as the Amazon rainforest which makes up roughly <a href="https://www.pnas.org/doi/full/10.1073/pnas.0801915105">40% of global tropical forest</a>, stores roughly <a href="https://www.pnas.org/doi/10.1073/pnas.1019576108">112 billion tonnes of carbon</a> and <a href="https://www.worldbank.org/en/news/feature/2019/05/22/why-the-amazons-biodiversity-is-critical-for-the-globe">harbours 25% of land-based life</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-clouds-are-the-missing-piece-in-the-climate-change-puzzle-140812">Why clouds are the missing piece in the climate change puzzle</a>
</strong>
</em>
</p>
<hr>
<p><a href="https://www.sciencedirect.com/science/article/abs/pii/0022169482901172">Research</a> shows that clearing forests reduces the flow of moisture to the atmosphere, dampening how efficiently the Earth system can circulate water and ultimately putting ecosystems like the Amazon <a href="https://www.nature.com/articles/ncomms14681">at risk of collapse</a>. Global heating and changes to how the land is used, especially deforestation, are among the biggest factors responsible for humanity’s transgression of this planetary boundary. Their combined influence indicates that the planetary boundaries interact and need to be treated as <a href="https://www.cell.com/one-earth/fulltext/S2590-3322(21)00478-4">one networked system</a>.</p>
<figure class="align-center ">
<img alt="An excavator digs up soil in a tropical forest clearing." src="https://images.theconversation.com/files/471120/original/file-20220627-20-fk82u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471120/original/file-20220627-20-fk82u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471120/original/file-20220627-20-fk82u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471120/original/file-20220627-20-fk82u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471120/original/file-20220627-20-fk82u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471120/original/file-20220627-20-fk82u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471120/original/file-20220627-20-fk82u.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">Deforestation can halt the flow of green water in the hydrological cycle.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/deforestation-rainforest-environmental-problem-destruction-forest-1956048232">Santhosh Varghese/Shutterstock</a></span>
</figcaption>
</figure>
<p>Food production also depends on green water. Around <a href="https://www.sciencedirect.com/science/article/pii/S1464190900000046">60% of staple food production</a> globally and <a href="https://ascelibrary.org/doi/10.1061/%28ASCE%290733-9496%282006%29132%3A3%28129%29">80% of cultivated land</a> is rain-fed. In these areas, the only water reaching the crop is what rain provides. Even irrigated crops rely on rain to some extent.</p>
<p>We found that since the industrial revolution, and especially since the 1950s, larger parts of the world are subject to significantly drier or wetter soil. This shift towards extreme conditions is an alarming development due to the indispensable role of water in <a href="https://www.sciencedirect.com/science/article/pii/S2589915518300099">maintaining resilient societies and ecosystems</a> </p>
<p>More frequent and severe dry spells mean prolonged and more intense <a href="https://www.pnas.org/doi/full/10.1073/pnas.2002411117">droughts</a> in many regions, like those currently affecting <a href="https://theconversation.com/the-window-of-opportunity-to-address-increasing-drought-and-expanding-drylands-is-vanishing-176731">Chile and the western US</a>. This limits photosynthesis in plants, which absorb <a href="https://www.nature.com/articles/s41586-018-0424-4">less of the CO₂</a> heating Earth’s atmosphere. The land carbon sink, which currently soaks up about <a href="https://essd.copernicus.org/articles/11/1783/2019/">30% of annual CO₂ emissions</a>, is weakened as a result, and could even <a href="https://iopscience.iop.org/article/10.1088/1748-9326/11/4/044002">become a net source</a> of carbon in the future.</p>
<p>Too much soil water is no good either. Water-saturated soils make floods more likely and suffocate plant growth. Abnormally large quantities of water evaporating from wet soils can <a href="https://science.thewire.in/environment/india-monsoon-refuses-retreat-erratic-rainfal-uttarakhand-floods/">delay the onset of monsoons</a> in places like India, where the dry season has extended and disrupted farming. High humidity combined with high temperatures can also cause deadly heatwaves, as the human body quickly overheats when sweating <a href="https://www.vice.com/en/article/qjbq5p/indias-heat-wave-is-a-grim-warning-for-deadly-wet-bulb-temperatures">becomes impossible in very moist air</a>. Several regions, like South Asia, the coastal Middle East and the Gulf of California and Mexico, are <a href="https://www.science.org/content/article/lethal-levels-heat-and-humidity-are-gripping-global-hot-spots-sooner-expected">experiencing this lethal combination</a> much earlier than expected.</p>
<h2>What can be done?</h2>
<p>Growing scientific evidence suggests that the planet is both drier and wetter than at any point within the last 11,700 years. This threatens the ecological and climatic conditions that support life. </p>
<p>Our analysis shows that the sixth planetary boundary has been crossed. But ambitious efforts to slow climate change and halt deforestation could still prevent dangerous changes to the cycling of Earth’s <a href="https://www.pnas.org/doi/full/10.1073/pnas.1817380116">green water</a>. Along with other measures, switching farming practices <a href="https://link.springer.com/referenceworkentry/10.1007/978-1-4939-2493-6_1129-1">to sustainable alternatives</a> would prevent more soil being degraded and losing its moisture. <a href="https://wires.onlinelibrary.wiley.com/doi/10.1002/wat2.1406">Explicitly governing green water</a> and its protection in policy and legal frameworks may also be necessary. </p>
<p>Research has shown that farming is a major cause of <a href="https://www.ecologyandsociety.org/vol22/iss4/art8/">multiple planetary limits</a> being breached. Shifting diets towards sustainable plant-based food is a <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(18)31788-4/fulltext">simple yet highly effective</a> option for keeping humanity within these boundaries.</p>
<p>Humanity is no longer in the safe zone. Immediate action is needed to maintain a resilient and nourishing freshwater cycle. </p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
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<p class="fine-print"><em><span>Arne Tobian receives funding from the European Research Council through the ‘Earth Resilience in the Anthropocene’ project (no. ERC-2016- ADG 743080). He is affiliated with the Stockholm Resilience Centre and the Potsdam Institute for Climate Impact Research. </span></em></p><p class="fine-print"><em><span>Dieter Gerten is research team leader at the Potsdam Institute for Climate Impact Research and also professor for Global Change Climatology and Hydrology at the Geographical Institute of Humboldt-Universität zu Berlin. </span></em></p><p class="fine-print"><em><span>Lan Wang-Erlandsson receives funding from the European Research Council through the ‘Earth Resilience in the Anthropocene’ project (no. ERC-2016- ADG 743080) and financial support from the IKEA Foundation.</span></em></p>‘Green water’ is essential for healthy soils and a benign climate, but it’s under threat.Arne Tobian, PhD Candidate in Planetary Boundaries, Stockholm UniversityDieter Gerten, Working Group Leader, Terrestrial Safe Operating Space, Potsdam Institute for Climate Impact ResearchLan Wang Erlandsson, Researcher and Theme leader, Anthropocene Dynamics, Stockholm Resilience Centre, Stockholm UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1774532022-02-23T19:13:03Z2022-02-23T19:13:03ZClimate change is warping our fresh water cycle – and much faster than we thought<figure><img src="https://images.theconversation.com/files/447974/original/file-20220223-15-1xyzaw5.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4665%2C3456&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Fresh water cycles from ocean to air to clouds to rivers and back to the oceans. This constant shuttling can give us the illusion of certainty. Fresh water will always come from the tap. Won’t it? </p>
<p>Unfortunately, that’s not guaranteed. Climate change is shifting where the water cycle deposits water on land, with drier areas becoming drier still, and wet areas becoming even wetter. </p>
<p>Our research <a href="https://www.nature.com/articles/s41586-021-04370-w">published today in <em>Nature</em></a> has found the water cycle is changing faster than we had thought, based on changes in our oceans. </p>
<p>This concerning finding underlines the ever more pressing need to end the emissions of gases warming the atmosphere before the water cycle changes beyond recognition.</p>
<p>If this sounds serious, it is. Our ability to harness fresh water makes possible modern society. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/447981/original/file-20220223-21-tecojb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Rain falling on ocean" src="https://images.theconversation.com/files/447981/original/file-20220223-21-tecojb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/447981/original/file-20220223-21-tecojb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/447981/original/file-20220223-21-tecojb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/447981/original/file-20220223-21-tecojb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/447981/original/file-20220223-21-tecojb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/447981/original/file-20220223-21-tecojb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/447981/original/file-20220223-21-tecojb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">It’s hard to track how much rain falls on our oceans.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>The water cycle has already changed</h2>
<p>As the Earth warms up, the water cycle has begun to intensify in a “<a href="https://www.doi.org/10.1111/nyas.14337">wet-gets-wetter-dry-gets-drier</a>” pattern. </p>
<p>This means more and more freshwater is leaving dry regions of the planet and ending up in wet regions.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-water-cycle-is-intensifying-as-the-climate-warms-ipcc-report-warns-that-means-more-intense-storms-and-flooding-165590">The water cycle is intensifying as the climate warms, IPCC report warns – that means more intense storms and flooding</a>
</strong>
</em>
</p>
<hr>
<p>What might this look like? <a href="https://theconversation.com/the-water-cycle-is-intensifying-as-the-climate-warms-ipcc-report-warns-that-means-more-intense-storms-and-flooding-165590">Weather, intensified</a>. In relatively dry areas, more intense droughts, more often. In relative wet areas, more extreme storms and flooding. </p>
<p>Think of the <a href="https://www.theguardian.com/environment/2022/feb/15/us-west-megadrought-worst-1200-years-study">megadrought afflicting </a>America’s west, of the unprecedented floods <a href="https://www.theguardian.com/environment/2021/jul/16/climate-scientists-shocked-by-scale-of-floods-in-germany">in Germany</a>, or of the increase in severe rainfall seen in <a href="https://www.theatlantic.com/science/archive/2022/02/mumbai-flooding-climate-change/621471/">cities like Mumbai</a>. </p>
<p>This shift is already happening. In its landmark 2021 report, the UN’s Intergovernmental Panel on Climate Change (IPCC) drew on this growing body of research to conclude climate change was already causing <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">long-term changes to the water cycle</a>. </p>
<p>The changes we’re seeing are just the start. Over the next few decades, this water cycle intensification could make it much harder for people to get reliable supplies of fresh water across large areas of the planet. </p>
<p>Troublingly, while we know the water cycle is intensifying, we don’t fully know how much and how fast. That’s where the ocean comes into play. </p>
<h2>How to use the ocean as a rain gauge</h2>
<p>The main reason it’s hard to directly measure changes to the water cycle is that we don’t have enough measurements of rainfall and evaporation over our planet. </p>
<p>On a practical level, it’s very hard to set up permanent rain gauges or evaporation pans on the 70% of our planet’s surface covered in water. Plus, when we assess change over the long term, we need measurements from decades ago. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/447980/original/file-20220223-15-1l9rs2p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="evaporation off ocean" src="https://images.theconversation.com/files/447980/original/file-20220223-15-1l9rs2p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/447980/original/file-20220223-15-1l9rs2p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/447980/original/file-20220223-15-1l9rs2p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/447980/original/file-20220223-15-1l9rs2p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/447980/original/file-20220223-15-1l9rs2p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/447980/original/file-20220223-15-1l9rs2p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/447980/original/file-20220223-15-1l9rs2p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Evaporation over the Barents Sea, which has been warming rapidly.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The solution scientists have landed on is to use the ocean. Many may not realise the ocean can be less or more salty depending on the region. For instance, the Atlantic is saltier than the Pacific on average. </p>
<p>Why? Rain. When fresh water falls as rain on the ocean, it dilutes the sea water and makes it less salty. When water evaporates from the surface, the salt is left behind, increasing the salinity. This means we can use the better-recorded changes in the ocean’s salinity as a kind of rain gauge to detect water cycle changes. </p>
<p>Earlier research used this method to track changes to the salinity at the ocean’s surface. This research suggested the water cycle is <a href="https://www.doi.org/10.1126/science.1212222">intensifying dramatically</a>. </p>
<p>Unfortunately, the ocean does not stay still like a conventional rain gauge. Currents, waves and circular eddy currents keep the ocean’s waters in constant motion. This uncertainty has left a question mark over how exact the link between salinity and water cycle change actually is. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/predicting-droughts-and-floods-why-were-studying-19th-century-ocean-records-164985">Predicting droughts and floods: why we're studying 19th-century ocean records</a>
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</em>
</p>
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<p>In response, we have developed new methods enabling us to precisely link changes in the ocean’s salinity to changes in the part of the water cycle moving fresh water from warmer to colder regions. Our estimates indicate how the broader water cycle is changing in the atmosphere, over land and through our oceans. </p>
<p>What did we find in our <a href="https://www.nature.com/articles/s41586-021-04370-w">new study</a>? The fresh water equivalent of 123,000 times the waters of Sydney Harbour have shifted from the tropics to the cooler areas since 1970. That’s an estimated 46,000 to 77,000 cubic kilometres of water. </p>
<p>This is consistent with an intensification of the water cycle of up to 7%. That means up to 7% more rain in wetter areas and 7% less rain (or more evaporation) in dryer areas. </p>
<p>This is at the upper end of estimates established by several <a href="https://doi.org/10.1038/srep38752">previous studies</a>, which suggested an intensification closer to 2-4%. </p>
<p>Unfortunately, these findings suggest potentially disastrous changes to the water cycle may be approaching faster than previously thought. </p>
<h2>What would the future be like with an altered water cycle?</h2>
<p>If our water cycle is getting more intense at a faster rate, that means stronger and more frequent extreme droughts and rainfall events. </p>
<p>Even if the world’s governments meet their target and keep global warming to a ceiling of 2°C, the IPCC predicts we would still endure extreme events <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">an average of 14% stronger</a> relative to a baseline period of 1850-1900. </p>
<p>Some people and ecosystems will be hit harder than others, as the IPCC report last year made clear. For example, Mediterranean nations, south-west and south-east Australia, and central America will all become drier, while monsoon regions and the poles will become wetter (or snowier).</p>
<p>In dry areas hit by these water cycle changes, we can expect to see real threats to the viability of cities unless alternatives such as desalination are put in place.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/447982/original/file-20220223-19-t000s8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Hand under tap with no water coming out" src="https://images.theconversation.com/files/447982/original/file-20220223-19-t000s8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/447982/original/file-20220223-19-t000s8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/447982/original/file-20220223-19-t000s8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/447982/original/file-20220223-19-t000s8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/447982/original/file-20220223-19-t000s8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/447982/original/file-20220223-19-t000s8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/447982/original/file-20220223-19-t000s8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Droughts are likely to be more severe and more common in dry parts of the world.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>What should we do? You already know the answer. </p>
<p>Decades of scientific research have shown the extremely clear relationship between greenhouse gas emissions and rising global temperatures, which in turn drives water cycle intensification. </p>
<p>This is yet another reason why we must move as quickly as humanly possible towards net-zero emissions to reduce the damage from climate change. </p>
<p>The changes to the water cycle we observed were largely due to older emissions, from the mid 20th century and earlier. We have increased our emissions dramatically since then. </p>
<p>What comes next is entirely up to us.</p><img src="https://counter.theconversation.com/content/177453/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Taimoor Sohail receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Jan Zika receives funding from the Australian Research Council and has received funding from the Natural Environment Research Council (United Kingdom).</span></em></p>Dry regions will get drier and wet regions wetter as the climate changes. How quickly? Quicker than we thought, unfortunately.Taimoor Sohail, Postdoctoral research associate, UNSW SydneyJan Zika, Associate Professor, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1762012022-02-02T13:06:53Z2022-02-02T13:06:53ZWhy a warming climate can bring bigger snowstorms<figure><img src="https://images.theconversation.com/files/443923/original/file-20220202-21-1vr2vha.jpg?ixlib=rb-1.1.0&rect=0%2C30%2C6720%2C4436&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Boston got socked with nearly 2 feet of snow in late January 2022.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/tall-snow-drifts-and-buried-cars-line-the-sidewalk-on-news-photo/1238082640">Scott Eisen/Getty Images</a></span></figcaption></figure><p>Many of the Northeast’s <a href="https://xmacis.rcc-acis.org/">heaviest snowfalls</a> in over a century of reliable record keeping have occurred since 1990. How can the spate of big snowstorms be reconciled with our warming climate? </p>
<p>I’m an <a href="https://scholar.google.com/citations?user=h3tGrwsAAAAJ&hl=en">atmospheric scientist</a>. Let’s look at an important law of physics and some theories that can help explain the changes.</p>
<p><iframe id="Pgnpr" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/Pgnpr/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>Warmer air, more moisture</h2>
<p>First, warmer air can hold more moisture than cold air.</p>
<p>Think of the atmosphere like a sponge. Air holds about 4% more water vapor for each additional degree Fahrenheit increase in temperature (that’s about 7% per degree Celsius). The physical law that explains this relationship is known as <a href="https://eos.org/research-spotlights/extreme-precipitation-expected-to-increase-with-warming-planet">the Clausius-Clapyron relation</a>.</p>
<p>This increased atmospheric moisture is helping to intensify the water cycle. The Northeast and Mid-Atlantic have become wetter – not just in winter, but in spring, summer and fall, too. In addition to more total precipitation over a season and year, the additional moisture also fuels extreme events, like <a href="https://www.scientificamerican.com/article/vapor-storms-are-threatening-people-and-property/">more intense hurricanes and flooding rains</a>. The Northeast has seen an <a href="https://nca2018.globalchange.gov/chapter/2/">increase of more than 50% in the heaviest precipitation events</a> in recent decades, the largest increase of any region of the U.S.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-is-snowfall-measured-a-meteorologist-explains-how-volunteers-tally-up-winter-storms-175628">How is snowfall measured? A meteorologist explains how volunteers tally up winter storms</a>
</strong>
</em>
</p>
<hr>
<p>In the early 1900s, winters across the Northeast typically averaged around 22 degrees Fahrenheit. Now, 26 degrees is the <a href="https://theconversation.com/warming-is-clearly-visible-in-new-us-climate-normal-datasets-159684">official new “normal” temperature</a>, defined as the average over 1991-2020. A few recent winters have been over 30. </p>
<p>In the Northeast, then, we have an environment that has warmed yet is often still below freezing. Put another way, regions of the world that are cold enough for snow have warmed enough to now be visited by storms capable of holding and dropping more moisture. Rather than intense downpours, the region gets heavy snow. </p>
<h2>The warming ocean plays a role</h2>
<p>The historic blizzard that buried Boston under nearly 2 feet of snow in January 2022 was fueled by ocean waters in the western Atlantic that are warmer than normal. That’s also part of a consistent pattern.</p>
<p><iframe id="cPPU2" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/cPPU2/16/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>The oceans have been absorbing more than 90% of the additional heat attributable to rising atmospheric greenhouse gases from human activities, particularly burning fossil fuels. The oceans now <a href="https://theconversation.com/ocean-heat-is-at-record-levels-with-major-consequences-174760">contain more heat energy</a> than any time since measurements began six decades ago.</p>
<p>Scientists are studying whether global warming may be driving a slowing of the ocean conveyor belt of currents that transport water around the globe. Satellite imagery and ocean measurements show that <a href="https://doi.org/10.1038/s43247-021-00143-5">warmer waters have “piled up</a>” along the East Coast, a possible indication of a slowing of the <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/oceans/amoc">Atlantic Meridional Overturning Circulation</a>.</p>
<p>Moisture evaporated from ocean water provides much of the energy for both tropical and mid-latitude extra-tropical cyclones, known commonly as nor’easters.</p>
<h2>The Arctic influences the snow pattern, too</h2>
<p>While tropical storm systems are fueled primarily by warm water, <a href="https://theconversation.com/what-is-a-bomb-cyclone-an-atmospheric-scientist-explains-175825">nor’easters gain energy from sharp temperature gradients</a> where cold and warm air masses meet. The frequency of cold air outbreaks is another aspect of climate change that may be contributing to recent increases in extreme snowfall events.</p>
<p>Recent research has suggested that a warming Arctic, including declines in Arctic sea ice and snow cover, is influencing behavior of the polar vortex, a band of strong westerly winds that forms in the stratosphere between about 10 and 30 miles above the Arctic every winter. The winds enclose a large pool of extremely cold air. </p>
<p>When the Arctic is relatively warm, the <a href="https://cpo.noaa.gov/Divisions-Programs/Communication-Education-and-Engagement/CEE-News/ArtMID/8293/ArticleID/2369/Research-Links-Extreme-Cold-Weather-in-the-United-States-to-Arctic-Warming">polar vortex tends to be weaker</a> and more easily elongates or “stretches,” allowing extremely cold air to dip south. Episodes of <a href="https://theconversation.com/how-arctic-warming-can-trigger-extreme-cold-waves-like-the-texas-freeze-a-new-study-makes-the-connection-166550">polar-vortex stretching have markedly increased in the past few decades</a>, leading, at times, to more severe winter weather in some places.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/6KEkSfgHJNk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">What is the polar vortex? NASA explains.</span></figcaption>
</figure>
<p>Arctic amplification, the enhanced warming to our north, may, paradoxically, be helping to shuttle cold air to the Eastern Seaboard during polar vortex disruptions, where the cold air can interact with warmer, moisture-laden air from the warmer-than-normal western Atlantic Ocean. The most recent stretched polar vortex event helped to bring together key ingredients for the historic blizzard.</p>
<h2>What’s ahead?</h2>
<p>Global climate models project an <a href="https://doi.org/10.1038/s41598-021-95979-4">increase in the most extreme snowfall events</a> across large areas of the Northern Hemisphere with future warming. In some other parts of the world, like Western Europe, <a href="https://theconversation.com/the-water-cycle-is-intensifying-as-the-climate-warms-ipcc-report-warns-that-means-more-intense-storms-and-flooding-165590">intensification of the hydrological cycle</a> will mean more winter rain than snow as temperatures rise.</p>
<p>For the east coast of North America, as well as Northern Asia, winter temperatures are expected to still be cold enough for storms to bring heavy snow – at least through mid-century. Climate models suggest that extreme snowfalls will become rarer, but not necessarily less intense, in the second half of the century, as more storms produce rain.</p>
<p>The sharp increase in high-impact Northeast winter storms is an expected manifestation of a warming climate. It’s another risk the U.S. will have to prepare for as extreme events become more common with climate change.</p><img src="https://counter.theconversation.com/content/176201/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael A. Rawlins receives funding from The Department of Energy, the National Aeronautics and Space Administration, and the National Science Foundation. </span></em></p>Winters are getting warmer, yet Bostonians were digging out from nearly 2 feet of snow from a historic blizzard in late January. Why is the Northeast seeing more big snowstorms like this?Michael A. Rawlins, Associate Director, Climate System Research Center, UMass AmherstLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1729302021-12-01T16:45:08Z2021-12-01T16:45:08ZWhy increased rainfall in the Arctic is bad news for the whole world<figure><img src="https://images.theconversation.com/files/435062/original/file-20211201-27-ih0xtx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A rainy day in Baffin Island, northern Canada. </span> <span class="attribution"><span class="source">Petr Kahanek / shutterstock</span></span></figcaption></figure><p>Before the end of this century, most of the Arctic will for the first time receive more rain than snow across a whole year. That’s one of the key findings of a new study on precipitation in the Arctic which has major implications – not just for the polar region, but for the whole world.</p>
<p>While a reduction in <a href="https://www.ipcc.ch/srocc/chapter/chapter-3-2/">frozen ocean surface</a> is one of the most widely recognised impacts of Arctic warming, it has also long been anticipated that a warmer Arctic will be a wetter one too, with more intense cycling of water between land, atmosphere and ocean. The shift from a frozen region towards a warmer, wetter Arctic is driven by the capacity of a warmer atmosphere to hold more moisture, by increased rates of evaporation from ice-free oceans, and by the jet stream relaxing.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/435063/original/file-20211201-27-1po1hba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="graphic of water cycle" src="https://images.theconversation.com/files/435063/original/file-20211201-27-1po1hba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435063/original/file-20211201-27-1po1hba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=610&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435063/original/file-20211201-27-1po1hba.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=610&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435063/original/file-20211201-27-1po1hba.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=610&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435063/original/file-20211201-27-1po1hba.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=767&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435063/original/file-20211201-27-1po1hba.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=767&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435063/original/file-20211201-27-1po1hba.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=767&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">How water cycles through the Arctic.</span>
<span class="attribution"><a class="source" href="http://arcticchamp.sr.unh.edu/pdffiles/reportfull.pdf.">Vörösmarty et al., 2001</a></span>
</figcaption>
</figure>
<p>The Arctic water cycle is expected to shift from a snow-dominated one towards a rain-dominated one during the 21st century, although the timing of this is <a href="https://doi.org/10.1002/2015JG003128">uncertain</a>. Now, a team of scientists have published a study in the journal <a href="https://doi.org/10.1038/s41467-021-27031-y">Nature Communications</a> which suggests that this shift will occur earlier than previously projected. The effect will be particularly strong in autumn, with most of the Arctic Ocean, Siberia and the Canadian Archipelago becoming rain-dominated by the 2070s instead of the 2090s.</p>
<h2>Warmer and wetter isn’t necessarily better</h2>
<p>Such a profound change to the Arctic water cycle will inevitably affect ecosystems on land and in the ocean. You might intuitively expect that a warmer and wetter Arctic would be very favourable for ecosystems – rainforests have many more species than tundra, after all. But the plants and animals of the Arctic have evolved for cold conditions over millions of years, and their relatively simple food web is vulnerable to disturbance. </p>
<p>For example, warmer temperatures can cause larval insects to emerge earlier, before the fish species that feed upon them have hatched. More rainfall means more nutrients washed into rivers, which should benefit the microscopic plants at the base of the food chain. </p>
<p>However, this also makes rivers and coastal waters more murky, blocking light needed for photosynthesis and potentially clogging filter-feeding animals, including some whales or sharks. Brackish water typically supports fewer species than either freshwater or seawater, so increasing flows of freshwater offshore may well <a href="https://www.amap.no/documents/doc/the-arctic-freshwater-system-in-a-changing-climate/1375">reduce the range</a> of animals and plants along Arctic coasts.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/435099/original/file-20211201-20-jxalf2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Brown water meets blue water, icy mountains in background" src="https://images.theconversation.com/files/435099/original/file-20211201-20-jxalf2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435099/original/file-20211201-20-jxalf2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435099/original/file-20211201-20-jxalf2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435099/original/file-20211201-20-jxalf2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435099/original/file-20211201-20-jxalf2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435099/original/file-20211201-20-jxalf2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435099/original/file-20211201-20-jxalf2.png?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">Murky river water on an Arctic coastal plain near Ny-Ålesund, Svalbard.</span>
<span class="attribution"><span class="source">Guy Tallentire</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Further into the Arctic Ocean, there are more reasons to doubt the potential benefits of warmer temperatures and greater freshwater circulation. The dissolved constituents of rainfall, river water and melting snow and ice reduce the alkalinity of Arctic surface waters, which makes it harder for marine organisms to build shells and skeletons, and limits chemical neutralisation of the acidifying effects of <a href="https://www.amap.no/documents/doc/the-arctic-freshwater-system-in-a-changing-climate/1375">CO₂ absorbed in seawater</a>.</p>
<p>At the same time, rivers flowing through degrading permafrost will wash organic material into the sea that bacteria can convert to CO₂, making the ocean more acidic. Fresh water also essentially floats on denser seawater. </p>
<p>This causes the ocean to become stratified, impeding exchanges of nutrients and organisms between the deep sea and the surface, and restricting biological activity. Therefore the likely impacts of a warmer, wetter Arctic on food webs, biodiversity and food security are uncertain, but are unlikely to be uniformly positive.</p>
<h2>Arctic change is decades ahead of global averages</h2>
<p>Temperature increases in the Arctic have raced ahead of the global average. This will only be reinforced as snowfall is reduced and rainfall increases, since snow reflects the sun’s energy back into space. As the land becomes less snowy and less reflective, bare ground will absorb more solar energy, and thus will warm up. The Arctic is set to continue warming faster than elsewhere, further diminishing the difference in temperature between the warmest and coldest parts of the planet, with <a href="https://doi.org/10.1029/2018EF001088">complex implications</a> for the oceans and atmosphere.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/435064/original/file-20211201-27-1ixu6ee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of predicted global warming." src="https://images.theconversation.com/files/435064/original/file-20211201-27-1ixu6ee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435064/original/file-20211201-27-1ixu6ee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=189&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435064/original/file-20211201-27-1ixu6ee.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=189&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435064/original/file-20211201-27-1ixu6ee.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=189&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435064/original/file-20211201-27-1ixu6ee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=238&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435064/original/file-20211201-27-1ixu6ee.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=238&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435064/original/file-20211201-27-1ixu6ee.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=238&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The Arctic is the fastest-warming region in the world.</span>
<span class="attribution"><a class="source" href="https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM_final.pdf">IPCC 5th Assessment Report</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/435066/original/file-20211201-13-maiarn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of predicted precipitation change." src="https://images.theconversation.com/files/435066/original/file-20211201-13-maiarn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435066/original/file-20211201-13-maiarn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=195&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435066/original/file-20211201-13-maiarn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=195&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435066/original/file-20211201-13-maiarn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=195&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435066/original/file-20211201-13-maiarn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=245&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435066/original/file-20211201-13-maiarn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=245&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435066/original/file-20211201-13-maiarn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=245&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 Arctic is also expected to get a lot more rain.</span>
<span class="attribution"><a class="source" href="https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM_final.pdf">IPCC 5th Assessment Report</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The recent COP26 climate summit in Glasgow focused on efforts to “<a href="https://ukcop26.org/cop26-keeps-1-5c-alive-and-finalises-paris-agreement/">keep 1.5°C alive</a>”. It is worth remembering that the 1.5°C figure is a global average, and that the Arctic will warm by at least twice as much as this, even for modest projections. </p>
<p>The new study underscores the importance of the global 1.5°C target for the Arctic. For instance, at that level of warming <a href="https://theconversation.com/what-greenlands-record-breaking-rain-means-for-the-planet-166567">Greenland</a> is expected to transition to a rainfall-dominated climate for most of the year. While at 3°C warming, which is close to the current pathway <a href="https://climateactiontracker.org/global/cat-thermometer/">based on existing policies</a> rather than pledges, most regions of the Arctic will transition to a rainfall-dominated climate before the end of the 21st-century. </p>
<p>It’s research that adds further weight to calls for <a href="https://doi.org/10.5281/zenodo.4294063">improved monitoring</a> of Arctic hydrological systems and to the growing awareness of the considerable impacts of even small increments of atmospheric warming.</p>
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Read more:
<a href="https://theconversation.com/less-snow-more-rain-in-store-for-the-arctic-study-finds-172732">Less snow, more rain in store for the Arctic, study finds</a>
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<img src="https://counter.theconversation.com/content/172930/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Hodgkins has received funding from the UK Natural Environment Research Council, the Svalbard Integrated Arctic Earth Observing System, and the Royal Society.</span></em></p>Some Arctic regions will see more rain than snow decades earlier than previously thought, say scientists.Richard Hodgkins, Senior Lecturer in Physical Geography, Loughborough UniversityLicensed 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>
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<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">
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<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>
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<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>
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<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>
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<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>
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<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>
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<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/1657972021-08-09T08:03:59Z2021-08-09T08:03:59ZThe global water cycle has become more intense, and that makes New Zealand’s wet regions wetter, and dry ones drier<figure><img src="https://images.theconversation.com/files/415154/original/file-20210809-23-md4lis.jpg?ixlib=rb-1.1.0&rect=77%2C252%2C6412%2C4067&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Sanka Vidanagama/NurPhoto via Getty Images</span></span></figcaption></figure><p>The Intergovernmental Panel on Climate Change (<a href="https://www.ipcc.ch/">IPCC</a>) has delivered a sobering update on how much the Earth has warmed and how the climate system is responding.</p>
<p>The IPCC’s Sixth Assessment Report (<a href="https://www.ipcc.ch/assessment-report/ar6/">AR6</a>) is the most comprehensive yet. It shows Earth is now 1.09°C warmer than it was in the 1850s, and that each incremental increase in warming will bring more extreme weather events.</p>
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Read more:
<a href="https://theconversation.com/this-is-the-most-sobering-report-card-yet-on-climate-change-and-earths-future-heres-what-you-need-to-know-165395">This is the most sobering report card yet on climate change and Earth's future. Here’s what you need to know</a>
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<p>For the first time, the assessment also includes a regional breakdown of observed and projected changes. </p>
<p>It shows that while the Australian continent has warmed faster than the global average, at 1.4°C since 1850, New Zealand’s climate has been changing in line with global trends over the last century. </p>
<p>The average temperature has gone up by 1.1°C and sea levels have risen about 20cm. The wetter western parts of the country have become even wetter, with more heavy rainfall events, while the drier regions in the east and in Northland have become drier. </p>
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<img alt="Sheep paddock during drought" src="https://images.theconversation.com/files/415158/original/file-20210809-23-v4orgg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415158/original/file-20210809-23-v4orgg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=370&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415158/original/file-20210809-23-v4orgg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=370&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415158/original/file-20210809-23-v4orgg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=370&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415158/original/file-20210809-23-v4orgg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=465&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415158/original/file-20210809-23-v4orgg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=465&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415158/original/file-20210809-23-v4orgg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=465&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">New Zealand’s east and far north regions can expect longer and more intense droughts.</span>
<span class="attribution"><span class="source">Shutterstock/S Curtis</span></span>
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</figure>
<p>Projections for the future continue this theme, becoming wetter in the west, while the eastern regions and the far north continue to dry, especially in winter and spring. </p>
<h2>Irreversible changes</h2>
<p>The change in rainfall is associated with an overall increase in the strength of the westerly winds across the country, along with an increase in high pressures and settled weather over the far north as the atmospheric band known as the “subtropical high pressure region” is moving south, closer towards the pole.</p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/CSWJ-p2hXyu/?utm_source=ig_web_copy_link","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<p>The overall average warming brings an increase in hot days around the country and more frequent marine heatwaves, with warmer sea surface temperatures over the Tasman Sea and around New Zealand. </p>
<p>The AR6 shows that some of the changes have now become irreversible, at least on time scales of hundreds or even thousands of years. </p>
<p>Across the globe, glaciers will keep retreating as the climate warms. New Zealand’s glaciers will also continue to melt and recede and could disappear right up their valleys if warming reaches 2°C or more. </p>
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<p>
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<strong>
Read more:
<a href="https://theconversation.com/rising-seas-and-melting-glaciers-these-changes-are-now-irreversible-but-we-have-to-act-to-slow-them-down-165527">Rising seas and melting glaciers: these changes are now irreversible, but we have to act to slow them down</a>
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<p>The seas will also continue to rise, but how much and how quickly also depends on the amount of warming the world experiences. Even if we manage to cap warming at around 1.5°C, New Zealand will experience up to half a metre of sea level rise by the end of this century.</p>
<h2>A changing water cycle</h2>
<p>The latest assessment report takes a storyline approach and dedicates each chapter to a specific element of Earth’s climate system. I was an author for a chapter on the water cycle.</p>
<p>Water is vital for life, and changes in water availability have serious implications worldwide. Overall, we see that the water cycle is becoming more intense, that is, a warming atmosphere leads to both more precipitation over land and higher evaporation. </p>
<p>The magnitude and frequency of floods and droughts are increasing in many parts of the world. There is not enough published literature on such trends in New Zealand specifically, but we do know that climate change has made individual floods and droughts more intense in this country. </p>
<p>It is clear that all aspects of the water cycle are affected by warming, including rain and snowfall, glacier mass, groundwater storage, river flows and the oceans. </p>
<p>One clear signal is that variability and extremes in precipitation are increasing, above the rate of the global average. Unless we can reduce greenhouse gas emissions rapidly, we will see even more substantial changes in the water cycle worldwide, including the loss of glaciers and the river flows they feed, more intense precipitation, more extreme rainfall events and associated river floods, but also more intense droughts and an increased risk of wildfires.</p>
<p>As the climate warms, storm tracks are moving towards the poles in many regions, notably across the southern hemisphere. At the same time, the high-pressure regions in the subtropics are expanding poleward. The net effects for New Zealand are that the west and south will see increased precipitation in winter and spring, while the north and east will see reductions. </p>
<h2>Abrupt changes</h2>
<p>We now have a much better understanding of how aerosols (air pollution) affect the water cycle, especially for tropical monsoons and tropical rainfall generally. An increase in aerosols has generally offset the effect of warming in recent decades. </p>
<p>One proposed technique for managing climate change is known as solar radiation modification. It involves blocking out sunlight by spraying aerosols into the stratosphere. </p>
<p>But recent research shows this could drive abrupt changes in the water cycle and affect different regions in potentially disruptive ways. For example, continued Amazon deforestation, combined with a warming climate, could tip the Amazon ecosystem into a dry state during the 21st century. </p>
<p>Climate change has never been more obvious or better understood. Nor has the urgency of action been clearer, if we are to avoid the really catastrophic consequences. Reduction of carbon dioxide and other greenhouse gas emissions must by a priority, from now. </p>
<p><em><a href="https://theconversation.com/au/topics/ipcc-report-2021-108383">Click here</a> to read more of The Conversation’s coverage of the IPCC report</em></p><img src="https://counter.theconversation.com/content/165797/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Renwick receives funding from the NZ Ministry of Business, Innovation and Employment. He is a Commissioner at the NZ Climate Change Commission and is a Coordinating Lead Author for the IPCC 6th Assessment Report.</span></em></p>New Zealand’s climate has been changing in line with global trends over the last century, warming by 1.1°C. But unless we curb emissions fast, we can brace for more extreme downpours and droughts.James Renwick, Professor, Physical Geography (climate science), Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1629102021-07-27T12:01:47Z2021-07-27T12:01:47ZSnow can disappear straight into the atmosphere in hot, dry weather<figure><img src="https://images.theconversation.com/files/412186/original/file-20210720-17-l3bga2.jpg?ixlib=rb-1.1.0&rect=421%2C0%2C1897%2C735&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In high alpine terrain, sun and dry air can turn snow straight into water vapor. </span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Matterhorn_(4448885336).jpg#/media/File:Matterhorn_(4448885336).jpg">Jeffrey Pang/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Creeks, rivers and lakes that are fed by melting snow across the U.S. West are <a href="https://www.usgs.gov/special-topic/water-science-school/science/snowmelt-runoff-and-water-cycle?qt-science_center_objects=0#qt-science_center_objects">already running low as of mid-July 2021</a>, much to the worry of farmers, biologists and <a href="https://scholar.google.com/citations?user=p4UqsX0AAAAJ&hl=en&oi=sra">snow hydrologists like me</a>. This is not surprising in California, where snow levels over the previous winter were <a href="https://water.ca.gov/News/News-Releases/2021/April-21/Statewide-Snowpack-Well-Below-Normal-as-Wet-Season-Winds-Down">well below normal</a>. But it is also true across Colorado and the Rocky Mountains, which in general received a <a href="https://www.cpr.org/2021/04/02/colorados-snowpack-was-almost-normal-this-winter-but-it-may-not-be-enough-water-for-the-year/">normal amount of snow</a>. You’d think if there was normal amount of snow you’d have plenty of water downstream, right?</p>
<p>Over a century ago, snow scientist James Church at the University of Nevada, Reno, began examining how the amount of <a href="https://doi.org/10.1002/qj.49704016905">snow on mountains related to the amount of water in rivers</a> fed by the melting snow. But as hydrologists have learned over the many decades since, the <a href="https://doi.org/10.1175/1525-7541(2004)005%3C0896:EOOWUS%3E2.0.CO;2">correlations between snows and river flows are not perfect</a>. Surprisingly, there is a lot researchers don’t know about <a href="https://www.usgs.gov/special-topic/water-science-school/science/snowmelt-runoff-and-water-cycle">how the snowpack is connected to rivers</a>. </p>
<p>Of course, a dry winter will result in <a href="https://www.cpr.org/2021/01/09/in-2020-colorado-saw-one-of-its-driest-and-warmest-years-ever-recorded/">meager flows in spring and summer</a>. But there are other reasons snow from the mountains won’t reach a river below. One growing area of research is exploring how <a href="https://doi.org/10.1126/science.aaz9600">droughts</a> can lead to chronically dry soil that sucks up more water than normal. This water also refills the groundwater below. </p>
<p>But another less studied way moisture can be lost is by <a href="https://doi.org/10.1002/hyp.7320">evaporating straight into the atmosphere</a>. Just as the amount of snow varies each year, so too does the loss of water to the air. Under the right conditions, more snow can disappear into the air than melts into rivers. But how snowfall and loss of moisture into the air itself relate to water levels in rivers and lakes is an <a href="https://www.usgs.gov/centers/co-water/science/snowpack-sublimation-measurements-and-modeling-colorado-river-basin?qt-science_center_objects=0#qt-science_center_objects">important and not well understood part of the water cycle</a>, particularly in drought years.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/8Gj8dr6AsYg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Under most conditions, frozen carbon dioxide, otherwise known as dry ice, doesn’t melt, but jumps straight from a solid to a gas when it is warmed up.</span></figcaption>
</figure>
<h2>Losing moisture to the air</h2>
<p>There are two ways moisture can be lost to the atmosphere before it reaches a creek or river. </p>
<p>The first is through <a href="https://www.usgs.gov/special-topic/water-science-school/science/evaporation-and-water-cycle">evaporation</a>. When water absorbs enough energy from the Sun, the water molecules will change into a gas called water vapor. This floating water vapor is then stored in the air. Most of this evaporation happens from the surface of lakes, from water in the soil or as snow melts and the water flows over rocks or other surfaces.</p>
<p>Another way moisture can be lost to the atmosphere is one you might be less familiar with: sublimation. Sublimation is when a solid turns directly into a gas – think of dry ice. The same can happen to water when <a href="https://www.usgs.gov/special-topic/water-science-school/science/sublimation-and-water-cycle?qt-science_center_objects=0#qt-science_center_objects">snow or ice turns directly into water vapor</a>. When the air is colder than freezing, sublimation happens when molecules of ice and snow absorb so much energy that they skip the liquid form and jump straight to a gas.</p>
<p>A number of atmospheric conditions can lead to increased <a href="https://www.usgs.gov/special-topic/water-science-school/science/evaporation-and-water-cycle">evaporation</a> and <a href="https://www.usgs.gov/special-topic/water-science-school/science/sublimation-and-water-cycle">sublimation</a> and eventually, less water making it to creeks and streams. Dry air can <a href="https://www.energy.gov/energysaver/evaporative-coolers">absorb more moisture than moist air</a> and pull more moisture from the ground into the atmosphere. High winds can also blow moisture into the air and away from the area where it initially fell. And finally, the warmer air is and more Sun that shines, the more energy is available for snow or water to change to vapor. When you get combinations of these factors – like <a href="https://www.livescience.com/58884-chinook-winds.html">warm, dry winds in the Rockies called Chinook winds</a> – evaporation and sublimation can happen quite fast. On a dry, windy day, <a href="https://doi.org/10.1002/2017WR021172">up to around two inches of snow can sublimate into the atmosphere</a>. That translates to about one swimming pool of water for each football field-sized area of snow.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412197/original/file-20210720-21-f8f12f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A small green metal tower and green wooden box in a snowy mountain forest." src="https://images.theconversation.com/files/412197/original/file-20210720-21-f8f12f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412197/original/file-20210720-21-f8f12f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412197/original/file-20210720-21-f8f12f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412197/original/file-20210720-21-f8f12f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412197/original/file-20210720-21-f8f12f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412197/original/file-20210720-21-f8f12f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412197/original/file-20210720-21-f8f12f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Snow survey sites, like the one seen here in Montana, can help scientists measure snowpack, but most sublimation happens above the treeline, a zone for which there is little data.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Snow_Survey72_(27281994099).jpg#/media/File:Snow_Survey72_(27281994099).jpg">USDA NRCS Montana/WikimediaCommons</a></span>
</figcaption>
</figure>
<h2>Sublimation is mysterious</h2>
<p>It is relatively easy to measure how much water is flowing through a river or in a lake. And using <a href="https://doi.org/10.1002/wat2.1140">satellites and snow surveys</a>, hydrologists can get decent estimates of how much snow is on a mountain range. Measuring evaporation, and especially sublimation, is much harder to do.</p>
<p>Today researchers usually estimate sublimation indirectly using <a href="https://doi.org/10.1002/hyp.10864">physics equations and wind and weather models</a>. But there are lots of <a href="https://doi.org/10.1007/s11707-018-0721-0">uncertainties and unknowns in these calculations</a>. Additionally, researchers know that the most moisture loss from sublimation <a href="https://doi.org/10.1002/2017WR021172">occurs in alpine terrain</a> above the treeline – but <a href="https://doi.org/10.5194/tc-8-329-2014">snow scientists rarely measure snow depths there</a>. This further adds to the uncertainty around sublimation because if you don’t know how much moisture a system started out with, it is hard to know how much was lost.</p>
<p>Finally, weather and <a href="https://doi.org/10.1175/1520-0442(1996)009%3C0928:ICVASI%3E2.0.CO;2">snowpack</a> depths <a href="https://doi.org/10.1175/JCLI-D-11-00356.1">vary a lot from year to year</a>. All of this makes measuring the amount of snow that falls and then <a href="https://doi.org/10.1002/hyp.5806">is lost to the atmosphere incredibly difficult</a>. </p>
<p>When scientists have been able to measure and estimate sublimation, they have measured moisture losses that range from a <a href="https://doi.org/10.1002/hyp.7320">few percent to more than half of the total snowfall</a>, depending on the climate and where you are. And even in one spot, sublimation can <a href="https://doi.org/10.1007/s11707-018-0721-0">vary a lot year to year</a> depending on snow and weather.</p>
<p>When moisture is lost into the atmosphere, it will fall to the surface as rain or snow eventually. But that could be on the other side of the Earth and is not helpful to drought-stricken areas.</p>
<h2>Important knowledge</h2>
<p>It is hard to say how important loss of moisture to the atmosphere is to the total water cycle in any given mountain range. <a href="https://www.nrcs.usda.gov/wps/portal/wcc/home/aboutUs/monitoringPrograms/automatedSnowMonitoring/">Automated snow monitoring systems</a> – especially at high elevations <a href="https://snowstudies.org/senator-beck-study-plot/">above the treeline</a> – can help researchers better understand what is happening to the snow and the conditions that cause losses to the atmosphere.</p>
<p>The amount of water in rivers – and when that water appears – influences agriculture, ecosystems and how people live. When there is a water shortage, problems occur. With climate change leading to <a href="https://blogs.edf.org/climate411/2021/04/30/how-climate-change-is-worsening-drought/">more droughts</a> and <a href="https://earthjustice.org/features/how-climate-change-is-fueling-extreme-weather">variable weather</a>, filling a knowledge gap of the water cycle like the one around sublimation is important.</p><img src="https://counter.theconversation.com/content/162910/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Steven R. Fassnacht is affiliated with Cooperative Institute for Research in the Atmosphere. </span></em></p>As rivers run dry in the Rocky Mountains and the West, it’s easy to wonder where all the snow you see on mountain peaks goes. Some of it ends up in the air, but researchers aren’t sure how much.Steven R. Fassnacht, Professor of Snow Hydrology, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1649852021-07-26T16:02:35Z2021-07-26T16:02:35ZPredicting droughts and floods: why we’re studying 19th-century ocean records<figure><img src="https://images.theconversation.com/files/412869/original/file-20210723-15-zbzn0l.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5050%2C3364&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/frothy-foaming-white-backwash-indian-ocean-1611860710">Alybaba/Shutterstock</a></span></figcaption></figure><p>Floods have caused <a href="https://www.bbc.co.uk/news/world-europe-57858829">unprecedented damage</a> in Europe recently, while in the Chinese city of Zhengzhou, the equivalent of a year’s worth of average rainfall fell in <a href="https://www.bbc.co.uk/news/world-asia-china-57861067">just three days</a>. In stark contrast, extreme heat and droughts have spawned wildfires and <a href="https://www.theguardian.com/us-news/2021/jul/08/pacific-northwest-heatwave-deaths">caused hundreds of deaths</a> in northwest America.</p>
<p>This kind of extremely wet or dry weather is likely to becoming more common as climate change intensifies. This is because in a warmer world, the amount of moisture that the atmosphere can hold <a href="https://glossary.ametsoc.org/wiki/Clausius-clapeyron_equation">will increase</a>. As a rough rule-of-thumb, for every 1°C temperature rise, the amount of moisture the atmosphere can store increases by as much as 7%.</p>
<p>More moisture means greater rainfall extremes. Perversely, it also means that dry regions may lose more water to the atmosphere through evaporation, and so droughts could lengthen and intensify. </p>
<p>Knowing how rainfall varied in the past can help scientists predict future changes, and the longer the record, the more valuable it is. But how can we assess how worldwide rainfall patterns have changed over decades and even centuries, given that we have only recently been able to make accurate global measurements thanks to satellite technology?</p>
<p>A new technique uses the salinity of the ocean at its surface to forecast how seasonal precipitation over land will change. The ocean’s average surface salinity is close to 35g of salt for each kilogram of seawater. But areas in the subtropics, where lots of water evaporates, are saltiest, while the polar regions and tropics are less salty, reflecting how much snow and rain they tend to get. Essentially, scientists have worked out a way to use the ocean as an enormous rain gauge.</p>
<h2>Measuring rainfall</h2>
<p>Using measurements from research ships and buoys, scientists have <a href="https://phys.org/news/2020-09-ocean-salinity-substantial-amplification-global.html">shown</a> that since the 1950s, the salty areas of the ocean have become saltier and the fresh areas fresher. This confirms that the global water cycle of evaporation and precipitation has intensified over the past 70 years.</p>
<p>But in order to understand how climate change will accelerate this process, it would help to know what ocean salinities were like early in the industrial age, before scientific observations of the global ocean were available.</p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&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>This story is part of <a href="https://theconversation.com/uk/topics/oceans-21-96784">Oceans 21</a></em></strong>
<br><em>Our series on the global ocean opened with <a href="https://oceans21.netlify.app/">five in-depth profiles</a>. Look out for new articles on the state of our oceans in the lead up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.</em></p>
<hr>
<p>Happily, there were two pioneering round-the-world oceanographic voyages in the 1870s. That of HMS Challenger (1872-6), led by Sir John Murray, is widely regarded as marking the start of large-scale marine science. Its many reports document new discoveries in marine biology and geology as well as ocean chemistry and physics. </p>
<p>Less well known is the voyage of the German Navy’s SMS Gazelle (1874-6) that made similar measurements to the Challenger. Neither ship measured salinity – a poorly defined concept in those days – but they did carefully measure the specific gravity of seawater samples.</p>
<figure class="align-center ">
<img alt="A contemporary drawing of a 19th-century research vessel." src="https://images.theconversation.com/files/412723/original/file-20210722-13-ilvoft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412723/original/file-20210722-13-ilvoft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412723/original/file-20210722-13-ilvoft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412723/original/file-20210722-13-ilvoft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412723/original/file-20210722-13-ilvoft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412723/original/file-20210722-13-ilvoft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412723/original/file-20210722-13-ilvoft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">HMS Challenger in the Southern Ocean.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/HMS_Challenger_(1858)#/media/File:HMS_challenger_William_Frederick_Mitchell.jpg">William Frederick Mitchell</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We converted these gravity values to salinity, allowing us to compare changes in the saltiness of the ocean that occurred before and after the 1950s. Our <a href="https://www.nature.com/articles/s43247-021-00161-3">research</a> showed that the trend of salty areas of the ocean getting saltier and fresh areas getting fresher also held true between the 1870s and the 1950s. </p>
<p>However, the rate of change over those 80 years, early in the industrial era, was half the rate between the 1950s and the present day. In simple terms, the trend is speeding up, matching the acceleration of sea surface temperature changes over the past 150 years. The water cycle has been intensifying since the Victorian era, making floods, droughts and wildfires more frequent and intense.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/412724/original/file-20210722-19-11q4lzx.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A world ocean map with rising and falling salinity levels highlighted." src="https://images.theconversation.com/files/412724/original/file-20210722-19-11q4lzx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412724/original/file-20210722-19-11q4lzx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412724/original/file-20210722-19-11q4lzx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412724/original/file-20210722-19-11q4lzx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412724/original/file-20210722-19-11q4lzx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412724/original/file-20210722-19-11q4lzx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412724/original/file-20210722-19-11q4lzx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Salinity changes in the ocean since the 1950s.</span>
<span class="attribution"><span class="source">Nature Communications in Earth and Environment</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Unravelling the complicated relationship between ocean surface salinity, rainfall and sea and air temperatures uses complex models of the ocean and atmosphere, run on the biggest computers. We can be certain that global temperatures will continue to rise with the continued emission of greenhouse gases. And our confidence in scientific predictions of future floods and droughts can also increase if those same models reproduce the changes in ocean salinity that have been measured as far back as the 19th century, as well as the faster changes since the mid-20th century.</p>
<p>As recent extreme weather events have shown, this is not just of academic interest – it will determine the course of millions of lives.</p><img src="https://counter.theconversation.com/content/164985/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Marsh received funding from NERC.</span></em></p><p class="fine-print"><em><span>Stuart Cunningham received funding from NERC.</span></em></p><p class="fine-print"><em><span>Simon Alasdair Josey and William John Gould 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>The water cycle is intensifying as the world warms, bringing heavier downpours and longer droughts.William John Gould, Emeritus Fellow, Marine Physics and Ocean Climate, National Oceanography CentreRobert Marsh, Professor of Oceanography and Climate, University of SouthamptonSimon Alasdair Josey, Professor of Ocean-Atmosphere Interaction, National Oceanography CentreStuart Cunningham, Professor of Ocean Circulation and Climate, Scottish Association for Marine ScienceLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1639132021-07-06T16:32:17Z2021-07-06T16:32:17ZReforesting Europe would increase rainfall – new research<figure><img src="https://images.theconversation.com/files/409695/original/file-20210705-35826-1kgcy2h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Evgeny Drablenkov / shutterstock</span></span></figcaption></figure><p>“Plant more trees” is often the first idea that comes to mind when we think about how to prevent further climate change or at least adapt to its impacts. There are good reasons for this. Multiple studies have shown that as well as trees being a fantastic way to store carbon dioxide, they offer other benefits, such as a <a href="https://iopscience.iop.org/article/10.1088/1748-9326/abdcf1/meta">cooling effect in cities</a>, the ability to <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/hyp.13802">reduce flood risk</a> and boost biodiversity, among other things. </p>
<p>Our new study in <a href="https://www.nature.com/articles/s41561-021-00773-6">Nature Geoscience</a> shows that trees could also affect rainfall patterns.</p>
<p>We used measurements of rainfall across Europe to investigate what effect forests have on rainfall totals. We know that forests mostly increase local and downwind rainfall in the summer and winter, but the magnitude of this effect varies across regions and seasons. </p>
<p>To identify a realistic reforestation strategy we used the <a href="https://doi.org/10.5281/zenodo.883444">global reforestation potential map</a>. In the area we looked at in our research (most of Europe), 14.4% of the land surface was considered suitable for reforestation, an area larger than France.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/409958/original/file-20210706-25-1y8gl2l.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of Europe with green shaded areas" src="https://images.theconversation.com/files/409958/original/file-20210706-25-1y8gl2l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/409958/original/file-20210706-25-1y8gl2l.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=405&fit=crop&dpr=1 600w, https://images.theconversation.com/files/409958/original/file-20210706-25-1y8gl2l.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=405&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/409958/original/file-20210706-25-1y8gl2l.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=405&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/409958/original/file-20210706-25-1y8gl2l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=509&fit=crop&dpr=1 754w, https://images.theconversation.com/files/409958/original/file-20210706-25-1y8gl2l.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=509&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/409958/original/file-20210706-25-1y8gl2l.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=509&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Much of Europe could be reforested (green = areas with realistic reforestation potential)</span>
<span class="attribution"><a class="source" href="https://www.arcgis.com/apps/mapviewer/index.html?layers=c529c9eb1df140859da92f560ef4bf70">'Global Reforestation Potential Map' Griscom et al (2017)</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>We then compared the effect of turning all that land into forest to the precipitation changes in a <a href="https://doi.org/10.18751/climate/scenarios/ch2018/1.0">future scenario</a> in which the world faces intermediate levels of climate change, based on current predictions. While the climate scenario projects wetter winters and drier summers, the inclusion of reforestation could enhance European summertime rainfall by an average of 7.6%, potentially offsetting some of the drying that climate change is projected to cause. However, we also found reforestation may exacerbate the increase in winter rainfall. </p>
<p>In the UK and Ireland for example, where around 37% of the land area has the potential for reforestation, we estimate that reforestation on this scale would increase precipitation by an average of 0.74 mm/day (24%) in winter and 0.48 mm/day (19%) during summer.</p>
<p>Several factors potentially contribute to this. Forests typically have a higher surface “roughness” than agricultural land. This creates more turbulence over the trees and slows the movement of heavy clouds causing them to rain over and downwind of the forests. The same is true of urban areas too – increased surface roughness from buildings can amplify the <a href="https://doi.org/10.1038/s41598-019-42494-2">precipitation over cities and downwind of cities</a>. And forests typically evaporate more water than agricultural land, particularly during the summer season, which likely means more rain.</p>
<p>These findings demonstrate the relevance of land management in the assessment of climate change pathways. Many countries are considering how changes to land cover could contribute to their climate mitigation and adaptation efforts. </p>
<p>For instance the recently published <a href="https://www.theccc.org.uk/publication/independent-assessment-of-uk-climate-risk/">climate change risk assessment</a> from the UK government’s Climate Change Committee advisory body highlights that the <a href="https://theconversation.com/why-the-uk-is-so-unprepared-for-the-impacts-of-climate-change-162976">gap has widened</a> between the level of risk we face and the level of adaptation underway. Intervention measures are therefore urgently needed but require careful consideration. The new report points out that we must avoid poor planning being “locked-in”.</p>
<p>Reforestation in particular needs careful planning, as trees need decades to grow, and as they interact in such a complex way with multiple aspects of the environment. For example, while we may see increased rainfall from forestation, we may also see decreased runoff and water availability, since trees typically evaporate more water than crops or grass. </p>
<p>The species of tree we plant also needs to be carefully considered – will it be able to cope with <a href="https://www.nature.com/articles/s41598-020-71055-1">higher temperatures</a>? Will the type of tree be resilient to the <a href="https://www.ukclimaterisk.org/wp-content/uploads/2021/06/CCRA3-Chapter-3-FINAL.pdf">invasive species and pathogens</a> projected to increase with climate change? If not, then we have wasted our time and money. </p>
<p>Policy makers therefore need to thoroughly and carefully assess any kind of nature-based solution before embarking on a scheme that may provide no long term benefit. It is all about making sure that we are putting the right intervention in the right place, at the right time.</p><img src="https://counter.theconversation.com/content/163913/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elizabeth Lewis receives funding from UK Research and Innovation and the European Research Council. </span></em></p><p class="fine-print"><em><span>Edouard Davin receives funding from the Swiss National Science Foundation. </span></em></p><p class="fine-print"><em><span>Ronny Meier works for ETH Zurich and receives funding from the Swiss National Science Foundation as well as the Swiss Federal Office of Environment FOEN.</span></em></p>Mass tree planting could affect precipitation patterns.Elizabeth Lewis, Lecturer in Computational Hydrology, Newcastle UniversityEdouard Davin, Senior Scientist, Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology ZurichRonny Meier, PostDoc, Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology ZurichLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1527762021-01-11T16:36:22Z2021-01-11T16:36:22ZLake Poopó: why Bolivia’s second largest lake disappeared – and how to bring it back<figure><img src="https://images.theconversation.com/files/377762/original/file-20210108-15-pzpont.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lake Poopó at a low point in early 2016.</span> <span class="attribution"><span class="source">Chiliguanca / flickr</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>A huge lake in Bolivia has almost entirely disappeared. Lake Poopó used to be the country’s second largest, after Lake Titicaca, and just a few decades ago in its wet season peak it would stretch almost 70km end to end and cover an area of <a href="https://link.springer.com/referenceworkentry/10.1007%2F978-1-4020-4410-6_137">3,000 sq km</a> – the size of a small country like Luxembourg. Today, the lake is largely a flat expanse of salty mud. </p>
<p>What happened? We’ve looked into this in various scientific studies over the past few years, and the answer is a mix of both climate factors and more direct human factors such as too much irrigation. This does at least provide some hope: Bolivians cannot reverse climate change themselves, but they can do a better job managing their water.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/378090/original/file-20210111-13-z608de.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of Bolivia" src="https://images.theconversation.com/files/378090/original/file-20210111-13-z608de.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/378090/original/file-20210111-13-z608de.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=740&fit=crop&dpr=1 600w, https://images.theconversation.com/files/378090/original/file-20210111-13-z608de.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=740&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/378090/original/file-20210111-13-z608de.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=740&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/378090/original/file-20210111-13-z608de.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=930&fit=crop&dpr=1 754w, https://images.theconversation.com/files/378090/original/file-20210111-13-z608de.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=930&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/378090/original/file-20210111-13-z608de.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=930&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bolivia is largely divided between the high altitude Altiplano (grey) and the Amazon basin (green). Lake Popoó is in the centre of the picture, south of Oruro.</span>
<span class="attribution"><a class="source" href="https://www.google.com/maps/@-17.7564879,-69.0182169,6z">Google Maps</a></span>
</figcaption>
</figure>
<p>Lake Poopó, is found at nearly 3,700 meters above sea level in the “Altiplano”, a large plateau in the centre of the Andes mountains. It is an <a href="https://www.worldatlas.com/articles/fluvial-landforms-what-is-an-endorheic-basin.html">endorheic basin</a>: nothing flows out, and water is lost only through evaporation. Since dissolved minerals stick around when water is evaporated, the lake is as salty as the ocean – in some places considerably saltier. </p>
<p>Nonetheless, some decades ago Poopó was home to large communities of plants and animals and was a source of resources for the region’s inhabitants. Nowadays, the situation is drastically different. Water levels have declined over the past two decades, and eventually the lake <a href="https://earthobservatory.nasa.gov/images/87363/bolivias-lake-poopo-disappears">dried out entirely</a> at the end of 2015 after the extreme weather phenomenon of El Niño.</p>
<figure> <img src="https://media.giphy.com/media/d8WznwFJnJpNF3CmqX/giphy.gif"><figcaption>The disappearance of Lake Poopó.</figcaption></figure>
<p>This was ecological devastation. Many of the lake’s 200 or so animal species disappeared, including reptiles, mammals, birds – it hosts a huge community of flamingos – and of course fish. There was also an exodus of rural people to the nearest big cities. Worst affected of all are the <a href="https://www.theguardian.com/world/2018/jan/04/the-ecological-catastrophe-that-turned-a-vast-bolivian-lake-to-a-salt-desert">Urus-Muratos</a>, an indigenous community whose entire way of life was based around fishing Lake Poopó. </p>
<p>Throughout Lake Poopó’s history, there have been several <a href="https://www.tandfonline.com/doi/pdf/10.1623/hysj.51.1.98?needAccess=true">periods when water levels were very low</a> but the lake used to recover by itself thanks to the rainy season and water from its main tributary the Desaguadero River, which itself drains Lake Titicaca and flows into the slightly lower altitude Poopó.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/377759/original/file-20210108-21-tlxlsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A river winds through a plateau" src="https://images.theconversation.com/files/377759/original/file-20210108-21-tlxlsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/377759/original/file-20210108-21-tlxlsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/377759/original/file-20210108-21-tlxlsp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/377759/original/file-20210108-21-tlxlsp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/377759/original/file-20210108-21-tlxlsp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/377759/original/file-20210108-21-tlxlsp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/377759/original/file-20210108-21-tlxlsp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The high altitude Desaguadero River.</span>
<span class="attribution"><span class="source">Stefan Haider / shutterstock</span></span>
</figcaption>
</figure>
<p>But during the past few decades, much of the Desaguadero was diverted for irrigation, so there was less water left to top up the lake. As Poopó is <a href="https://www.researchgate.net/figure/Bathymetry-of-Lake-Poopo-a-inclined-view-b-viewed-from-top_fig7_276042539">unusually shallow</a>, mostly just a few metres deep, relatively small changes in overall water volume make a big difference to its surface area. Though the lake has partially recovered due to above-average precipitation in the years since 2015, the situation is still dire.</p>
<p>In our <a href="https://www.mdpi.com/2072-4292/12/1/73">most recent study</a>, we analysed satellite data from the Lake Poopó catchment area over the past two decades and found that more water has been gained through precipitation than has been lost through evaporation. This points to poor management of the water resources in the area, rather than climatic variability, as the principle cause of the lake drying up. </p>
<p>This is not to minimise the role of climate variability. In a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0022169420309458">separate study</a>, we looked at changes in rainfall patterns and how they affected Lake Poopó. We found that, as time goes by, the rainy season is getting shorter but more intense. This will is amplifying the cycle of water storage in the lake, with the lake holding less water at the end of the dry season and more at the end of the wet one. It will become even more necessary to regulate resources, for instance by storing water during the wet season to use when it is dry.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/378046/original/file-20210111-19-v4igs1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Dried shore, boats on lake, hills in distance." src="https://images.theconversation.com/files/378046/original/file-20210111-19-v4igs1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/378046/original/file-20210111-19-v4igs1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/378046/original/file-20210111-19-v4igs1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/378046/original/file-20210111-19-v4igs1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/378046/original/file-20210111-19-v4igs1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/378046/original/file-20210111-19-v4igs1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/378046/original/file-20210111-19-v4igs1.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">Fishing boats on Lake Poopó back in 2006.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Fishing_boat_Lake_Poopo.jpg">Lovisa Selander / wiki</a></span>
</figcaption>
</figure>
<p>We found the highest increases in water losses took place in the area around the city of Oruro, which lies to the north of the lake. This is an area with lots of human activity, urban growth, new highways, and where river water has been used for mining and agriculture. Bolivia is the biggest producer of quinoa in the world and the crop increased by 45.5% from 1980 to 2011. As quinoa became more popular around the world over the past decade, production increased a further <a href="https://www.ine.gob.bo/index.php/estadisticas-economicas/agropecuaria/agricultura-cuadros-estadisticos">60% in just five years</a> to meet global demand.</p>
<p>This all highlights how vulnerable a place such as Lake Poopó can be when relationships between land, human politics and cycles of water and people <a href="https://www.sciencedirect.com/science/article/abs/pii/S0016718518300861">break apart</a>. The ecological disaster is a consequence of not only natural factors but also human activities – but at least this is one reason there is still hope we can reverse the problem.</p><img src="https://counter.theconversation.com/content/152776/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Juan Torres-Battló receives funding from the University of Surrey. </span></em></p><p class="fine-print"><em><span><a href="mailto:b.marti-cardona@surrey.ac.uk">b.marti-cardona@surrey.ac.uk</a> receives funding from University of Surrey, UKRI. </span></em></p>It’s an ecological disaster, but my research shows we should not lose hope.Juan Torres-Batlló, PhD Candidate, University of SurreyBelen Marti-Cardona, Lecturer in Earth Observation and Hydrology, University of SurreyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1500542020-11-17T05:22:13Z2020-11-17T05:22:13ZClimate Explained: what would happen if we cut down the Amazon rainforest?<figure><img src="https://images.theconversation.com/files/369707/original/file-20201117-15-1pr0bsu.jpg?ixlib=rb-1.1.0&rect=16%2C98%2C5439%2C3459&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Gustavo Frazao</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?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>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to <a href="mailto:climate.change@stuff.co.nz">climate.change@stuff.co.nz</a></em></p>
<hr>
<blockquote>
<p><strong>What would happen if we cut down the entire Amazon rainforest? Could it be replaced by an equal amount of reforestation elsewhere?</strong></p>
</blockquote>
<p>Removing the entire Amazon rainforest would have myriad consequences, with the most obvious ones possibly not the worst. </p>
<p>Most people will first think of the carbon currently stored in the Amazon, the world’s largest rainforest. But the consequences would be far-reaching for the climate as well as biodiversity and ecosystems — and, ultimately, people. </p>
<p>The overall impact of the Amazon’s complete removal is unthinkable and beyond the power of our current predictive tools. But let’s look at some aspects we can describe.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/statistic-of-the-decade-the-massive-deforestation-of-the-amazon-128307">Statistic of the decade: The massive deforestation of the Amazon</a>
</strong>
</em>
</p>
<hr>
<h2>Storing carbon, distributing water</h2>
<p>The Amazon rainforest is estimated to harbour about <a href="https://iopscience.iop.org/article/10.1088/1748-9326/aabc61/meta">76 billion tonnes of carbon</a>. If all trees were cut down and burned, the forest’s carbon storage capacity would be lost to the atmosphere. </p>
<p>Some of this carbon would be taken up by the oceans, and some by other ecosystems (such as temperate or arctic forests), but no doubt this would exacerbate climate warming. For comparison, humans emit about 10 billion tonnes of carbon every year through the <a href="https://ueaeprints.uea.ac.uk/id/eprint/69293/">burning of fossil fuels</a>.</p>
<p>But the Amazon forest does more than store carbon. It is also responsible for the circulation of huge quantities of water. </p>
<figure class="align-center ">
<img alt="Clouds over the Amazon rainforest." src="https://images.theconversation.com/files/369682/original/file-20201116-23-f8e6tx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/369682/original/file-20201116-23-f8e6tx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=771&fit=crop&dpr=1 600w, https://images.theconversation.com/files/369682/original/file-20201116-23-f8e6tx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=771&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/369682/original/file-20201116-23-f8e6tx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=771&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/369682/original/file-20201116-23-f8e6tx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=969&fit=crop&dpr=1 754w, https://images.theconversation.com/files/369682/original/file-20201116-23-f8e6tx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=969&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/369682/original/file-20201116-23-f8e6tx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=969&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A uniform layer of tiny ‘popcorn’ clouds covers the Amazon rainforest during the dry season.</span>
<span class="attribution"><span class="source">NASA/Jeff Schmaltz</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>This image, captured by NASA’s Aqua satellite in 2009, shows how the forest and the atmosphere interact to create a uniform layer of “popcorn” clouds during the dry season. It is during this period, the time without rain, that the <a href="https://earthobservatory.nasa.gov/images/39936/afternoon-clouds-over-the-amazon-rainforest">forest grows the most</a>. </p>
<p>If the Amazon’s cloud systems and its capacity to recycle water were to be disrupted, the ecosystem would tip over and irreversibly <a href="https://www.nature.com/articles/d41586-019-03595-0#ref-CR8">turn into dry savannah</a> very quickly. Estimates of where this tipping point could lie range from 40% deforestation to just <a href="https://advances.sciencemag.org/content/5/12/eaba2949?intcmp=trendmd-adv">20% loss of forest cover</a> from the Amazon. </p>
<p>Reforestation elsewhere to achieve the same amount of carbon storage is technically possible, but we have neither the time (several hundred years would be needed) nor the land (at least an equivalent surface area would be required). </p>
<p>Another reason why reforestation is not a remedy is that the water the rainforest circulates — and with it the availability of nutrients — would disappear. </p>
<p>Once you cut the circulation of water through (partial) deforestation, there is a point of no return. The water doesn’t disappear from the planet, but certainly from the forest ecosystems, with immediate and powerful <a href="https://www.nature.com/articles/d41586-019-03595-0?fbclid=IwAR0axCO7TmkJ34bprB2948XqNQUXPr8tMX4VZjz4AC6dm_f7uvH37hUSMQo">consequences for the world’s climate</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-found-2-c-of-warming-will-push-most-tropical-rainforests-above-their-safe-heat-threshold-139071">We found 2˚C of warming will push most tropical rainforests above their safe 'heat threshold'</a>
</strong>
</em>
</p>
<hr>
<h2>Loss of life</h2>
<p>Perhaps the most drastic, and least reversible, impact would be the loss of wildlife diversity. </p>
<p>The Amazon hosts an estimated <a href="https://www.pnas.org/content/105/Supplement_1/11498">50,000 plant species</a> — although more recent estimates cite a <a href="https://www.pnas.org/content/114/40/10695">slightly lower number</a>. </p>
<p>The number of animal species found in the Amazon is even higher, with the largest part made up by insects, representing around <a href="http://periodicos.uefs.br/ojs/index.php/sociobiology/article/view/4061">10% of the known insect fauna</a>, as well as a large but unknown number of fungi and microbes. </p>
<p>Once species are lost, they are lost forever, and this would ultimately be the most harmful consequence of cutting down the Amazon. It would possibly be worse than the loss of its role as a massive redistributor and storage of water and carbon.</p>
<p>Last but certainly not least, there are about <a href="https://wwf.panda.org/knowledge_hub/where_we_work/amazon/about_the_amazon/">30 million people</a> living in and near the Amazon rainforest. </p>
<p>The consequences of losing the forest as a provider of the ecosystem services mentioned above and as a source of food and habitat are unfathomable. The repercussions would reach far into global politics, the global economy, and societal issues.</p><img src="https://counter.theconversation.com/content/150054/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sebastian Leuzinger receives funding from The Royal Society of New Zealand. </span></em></p>As the world’s largest rainforest, the Amazon is not only an important carbon sink, but also home to thousands of species of plants and animals and a crucial part of the water cycle.Sebastian Leuzinger, Professor, Auckland University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1411232020-06-23T20:16:36Z2020-06-23T20:16:36ZWhy long-term environmental observations are crucial for New Zealand’s water security challenges<figure><img src="https://images.theconversation.com/files/343086/original/file-20200622-75529-oz7678.jpg?ixlib=rb-1.1.0&rect=41%2C113%2C3947%2C1764&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Andrew Lorrey</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Brewster Glacier in New Zealand’s Southern Alps lost 13 million cubic metres of ice between March 2016 and March 2019 - almost the equivalent of the basic drinking water needs of all New Zealanders during that time. </p>
<figure>
<iframe src="https://player.vimeo.com/video/405686001" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">Climate and glacier scientists monitor New Zealand’s ice and snow. Video produced by Rebekah Parsons-King and Stuart MacKay.</span></figcaption>
</figure>
<p>Simultaneously, seasonal extremes for Auckland - New Zealand’s largest city - swung from the wettest autumn on record to one of the most severe multi-season droughts.</p>
<p>Water is arguably the most precious resource in New Zealand. These contrasting extreme events in two very different regions highlight the critical importance of long-term observations as we confront water security challenges.</p>
<h2>Water extremes</h2>
<p>2017 became the wettest autumn on record for Auckland when an “<a href="https://www.nature.com/articles/ngeo2894">atmospheric river</a>” drenched the city for several days. Within a month, ex-tropical cyclones <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.3753">dumped even more extreme rainfall</a>. </p>
<p>Exceptionally high autumn rainfall (more than 200% higher than normal for many sites) during 2017 saturated soils and produced numerous slips. Sediment hampered water treatment for regional reservoirs that provide about 75% of the city’s water supply. </p>
<p>Fast forward to 2019, when one of the most significant multi-season droughts since the early 20th century started unfolding. Four Auckland sites we monitor show it was the driest summer in recent memory. The drought has continued, and <a href="https://www.stuff.co.nz/auckland/121614214/auckland-drought-little-sign-of-relief-for-declining-water-supply">water restrictions</a> are currently in place.</p>
<p>The big wet versus the big dry in Auckland only three years apart gives us a taste of New Zealand’s water future - a higher likelihood of <a href="https://knowledgeauckland.org.nz/media/1171/tr2017-031-2-auckland-region-climate-change-projections-and-impacts-summary-revised-jan-2018.pdf">more frequent water extremes with stronger impacts</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=408&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=408&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=408&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=513&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=513&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=513&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The stark contrast between extreme wet and dry conditions for the North Island (top) had significantly different impacts on Upper Mangatawhiri Reservoir (bottom). Both led to water conservation calls in Auckland.</span>
<span class="attribution"><span class="source">Climate data and visualisation: NIWA ; Google Earth maps</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Shrinking ice</h2>
<p>The Southern Alps tell a different story arising from climate extremes, where recent changes have been rapid, widespread and exceptional. The National Institute of Water and Atmosphere <a href="https://niwa.co.nz/climate/research-projects/climate-present-and-past/southern-alps-glaciers/end-of-summer-snowline-survey">end-of-summer snowline mission</a> – which has run nearly unbroken since the 1970s – provides valuable “time capsules” of glaciers and snowlines through a changing climate. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-birds-eye-view-of-new-zealands-changing-glaciers-97074">A bird’s eye view of New Zealand's changing glaciers</a>
</strong>
</em>
</p>
<hr>
<p>The long-term permanent snowline – the boundary between exposed glacial ice and recent snow – must sit below the mountain top for a glacier to exist. The 2018 Tasman Sea <a href="https://niwa.co.nz/climate/special-climate-statement-record-warmth-march-2018">marine heatwave</a> drove snowlines off the top of many peaks. Then, 2019 produced a second marine heatwave around northern New Zealand. Some small glaciers sustained so much damage during these extreme years that they are now on a path to extinction. </p>
<p>As if this wasn’t enough, <a href="https://www.theguardian.com/world/2020/jan/02/new-zealand-glaciers-turn-brown-from-australian-bushfires-smoke-ash-and-dust">ash and dust from Australian bushfires</a> blanketed Southern Alps glaciers during the 2020 summer and increased the potential for seasonal melt. </p>
<p>New <a href="https://www.nature.com/articles/s43017-020-0023-4">photogrammetry techniques</a> that produce digital elevation models with annual glacier photos help to define the impacts from extreme years like the last three. We are extending these techniques to our historic image archive to construct a 4D vision of ice volume, which brings us closer to quantifying water volume loss and gain for individual glaciers. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=326&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=326&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=326&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=410&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=410&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=410&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rising temperatures, higher snowlines, glacial lake expansion and dust from Australian bushfires are pushing some South Island glaciers towards extinction.</span>
<span class="attribution"><span class="source">Andrew Lorrey</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The recent ice loss from Brewster Glacier is only a small part of the frozen water volume stored in New Zealand’s Southern Alps. Since the first New Zealand glacier survey in the late 1970s, there’s been a long-term trend of glacial retreat through climate warming. </p>
<p>Southern Alps glaciers are estimated to <a href="https://theconversation.com/new-zealands-southern-alps-have-lost-a-third-of-their-ice-28916">have lost more than 30%</a> of their volume - about 16 billion cubic metres of ice, or the equivalent of about 200 litres a day for each New Zealander over 40 years. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-zealands-southern-alps-have-lost-a-third-of-their-ice-28916">New Zealand’s Southern Alps have lost a third of their ice</a>
</strong>
</em>
</p>
<hr>
<p>While water loss from vanishing glaciers is deeply troubling, it is a reminder that more severe and immediate concerns can arise from long and intense seasonal droughts and changes to <a href="https://www.mfe.govt.nz/sites/default/files/media/Climate%20Change/Hydrological%20projections%20report-final.pdf">rivers in a warming world</a>.</p>
<h2>Past and present observations help prepare for the future</h2>
<p>Long-term environmental observations help to inform national water security policy and water resource management. Our observations also underpin weather forecasts, <a href="https://niwa.co.nz/climate/seasonal-climate-outlook">seasonal climate predictions</a> and <a href="https://www.mfe.govt.nz/publications/climate-change/climate-change-projections-new-zealand">climate change projections</a> that cover a spectrum of advance warnings for extreme weather and climate impacts. </p>
<p>We need to grow environmental observations, but making and archiving them can be costly and difficult. Global support for their long-term stewardship once they are gathered is also at risk. As a result, small countries like New Zealand confront hard choices about which observations to make, what sites they come from, and how they are continued. </p>
<p>Amid the many COVID-19 announcements was an increase in funding for <a href="https://www.mbie.govt.nz/science-and-technology/science-and-innovation/agencies-policies-and-budget-initiatives/budget-initiatives/">nationally significant databases and collections</a>. This boost is a welcome signal for maintaining valuable scientific resources, including environmental observations, for future generations. </p>
<p>But ongoing support is needed to reduce attrition of our comprehensive evidence base. It would be even more risky to abandon long-term water and climate observations, and simply fly blind into an uncertain future.</p><img src="https://counter.theconversation.com/content/141123/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>AL receives financial support from NIWA for climate research and forecasting.
Rebekah Parsons-King and Stuart MacKay produced the video “Glaciers: A time capsule” with some support from the NIWA core-funded project “Climate Present and Past” (Contract CAOA2001) that AL leads.
</span></em></p><p class="fine-print"><em><span>BN receives financial support from NIWA for climate research and forecasting.</span></em></p><p class="fine-print"><em><span>LV receives financial support from a NIWA subcontract to VUW to undertake Structure From Motion work using the NIWA EOSS photo archive.</span></em></p>Auckland’s extreme drought and the rapid retreat of glaciers in the Southern Alps both highlight how important long-term observations are for water management policy and planning.Andrew Lorrey, Principal Scientist & Programme Leader of Climate Observations and Processes, National Institute of Water and Atmospheric ResearchBen Noll, Meteorologist/forecaster, National Institute of Water and Atmospheric ResearchLauren Vargo, Research Fellow in the Antarctic Research Centre, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1278762020-02-02T13:39:21Z2020-02-02T13:39:21ZClimate change, pollution and urbanization threaten water in Canada<figure><img src="https://images.theconversation.com/files/313120/original/file-20200131-41527-1brxgka.jpg?ixlib=rb-1.1.0&rect=163%2C98%2C5283%2C3530&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">If we're not careful, water may not be clean enough or available when we need it. </span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>In recent years, the daily news has been flooded with stories of water woes from coast to coast to coast. </p>
<p>There are <a href="https://globalnews.ca/news/4795735/glaciers-b-c-alberta-disappears-50-years/">melting glaciers and ice sheets in northern and western Canada</a> and lead in drinking water in the older neighbourhoods of many cities in Canada. We see toxic blue green algae <a href="https://www.empireadvance.ca/news/local-news/toxic-algae-endangers-pets-livestock-1.23923710">threatening pets, livestock</a> and <a href="https://news.usask.ca/articles/research/2019/health-threat-from-blue-green-blooms-extends-beyond-single-toxin-usask-study.php">drinking water</a> as well as catastrophic <a href="https://www.ctvnews.ca/canada/flooding-in-4-provinces-sparks-evacuations-1.4397911">floods</a>, <a href="https://www.cbc.ca/news/canada/manitoba/severe-drought-farmers-declare-disaster-1.5264877">droughts</a> and <a href="https://www.ctvnews.ca/sci-tech/how-wildfires-may-be-permanently-changing-canada-s-boreal-forest-1.4763748">fires</a>. </p>
<p>In 2018, parts of British Columbia experienced <a href="https://www.thestar.com/vancouver/2018/06/19/for-bc-fire-and-flood-disaster-cycle-wont-let-up-anytime-soon-and-may-get-worse.html">devastating floods, followed by wildfires a couple of months later</a>. </p>
<p>Our water resources are under threat from contamination, land use, urbanization and <a href="https://www.cbc.ca/news/technology/hottest-decade-1.5427846">climate change</a>. If we’re not careful, it may not be clean enough or available when we need it. </p>
<h2>An opportunity to lead</h2>
<p>The public supports environmental — and water — leadership in Canada. Many political pundits have suggested the federal election result of October 2019 was a <a href="https://www.cbc.ca/news/canada/calgary/election-2019-climate-change-andrew-leach-1.5321425">clear call for climate action</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/canadians-in-every-riding-support-climate-action-new-research-shows-122918">Canadians in every riding support climate action, new research shows</a>
</strong>
</em>
</p>
<hr>
<p>And yet Canada is on the front lines of <a href="https://changingclimate.ca/CCCR2019/">rapid climate changes</a> that affect the water cycle. Where, when, and how much rain, snow or freezing rain falls is changing across Canada.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/311505/original/file-20200123-162210-1ailoak.jpg?ixlib=rb-1.1.0&rect=140%2C95%2C4109%2C2726&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/311505/original/file-20200123-162210-1ailoak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311505/original/file-20200123-162210-1ailoak.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311505/original/file-20200123-162210-1ailoak.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311505/original/file-20200123-162210-1ailoak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311505/original/file-20200123-162210-1ailoak.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311505/original/file-20200123-162210-1ailoak.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">We cannot have good health if we do not have clean and accessible water.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>This is the water that we depend upon to replenish our groundwater, rivers and lakes, which continue to have a significant and increasing impact on water availability and quality in Canada and around the world.</p>
<p>However, Canadians remain divided on energy policy and resource development, and on appropriate solutions that balance environmental, economic and social needs. As Canadians, we must move beyond this and implement changes to better manage our water resources sustainably.</p>
<h2>Water front and centre</h2>
<p>We must manage our water sustainably because water is central to environmental, social and economic sustainability and therefore sustainable societies. This is the focus of the <a href="https://sustainabledevelopment.un.org/?menu=1300">UN’s Sustainable Development Goals</a>. These 17 goals identify targets that must be achieved for livelihoods, health, education, environment, cities, oceans, equity and partnership. </p>
<p>It’s important to understand that these goals are not isolated, but interrelated. This is why, even though there is a goal for water (<a href="https://www.unwater.org/what-we-do/monitor-and-report/">SDG 6</a>), there are 40 targets in the other 16 goals that relate directly to water. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/311501/original/file-20200123-162210-ysexjy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/311501/original/file-20200123-162210-ysexjy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311501/original/file-20200123-162210-ysexjy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311501/original/file-20200123-162210-ysexjy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311501/original/file-20200123-162210-ysexjy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=542&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311501/original/file-20200123-162210-ysexjy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=542&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311501/original/file-20200123-162210-ysexjy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=542&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The river system that the Grassy Narrows First Nation in northern Ontario relies on for food and water has been contaminated with mercury for almost 50 years. Since November 2015, 88 long-term drinking water advisories have been lifted across the country; 55 remain in place.</span>
<span class="attribution"><span class="source">THE CANADIAN PRESS/Paul Chiasson</span></span>
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</figure>
<p>For example, we cannot have good health if we do not have clean and accessible water, and children cannot go to school or adults to work, if they are not healthy. With water often at the heart of many social and economic inequities, it is critical to address water quantity, quality and access issues in order to meet all of the goals and to achieve the global sustainable development vision.</p>
<p><a href="https://gwf.usask.ca/sdgreport/">The recipe for managing Canada’s water resources</a> in a sustainable and equitable manner requires all of us to urgently recognize our changing climate and water resources, including drinking water, and act appropriately. </p>
<p>It requires federal co-ordination and leadership on water to overcome challenges of fragmented jurisdiction, such as following through with their commitment to create a <a href="https://www2.liberal.ca/our-platform/fresh-water/">Canada Water Agency</a>, develop a <a href="https://globalnews.ca/news/5221630/canada-is-the-only-g7-country-without-a-national-flood-forecasting-system-experts-say-theres-a-cost-to-that/">national flood forecasting system</a> and ensure universal access to adequate drinking water supplies. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/urban-floods-we-can-pay-now-or-later-96160">Urban floods: We can pay now or later</a>
</strong>
</em>
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<p>Research institutions must also step up to advance our knowledge, develop and assess decision support tools and solutions, and communicate their findings to communities, governments and economic sectors. </p>
<p>Finally, it requires reconciliation through shared nations’ governance of water resources and recognition of the <a href="https://www.waterteachings.com/water-is-knowledge">long history of successful, sustainable management of natural resources through Indigenous Knowledge</a> and <a href="http://www.unesco.org/new/fileadmin/MULTIMEDIA/FIELD/Venice/pdf/special_events/bozza_scheda_DOW_6_1.0.pdf">historical local knowledge</a>.</p>
<h2>Getting our own house in order</h2>
<p>Canada could support the world in achieving water sustainability, but it must first get its own house in order and achieve the UN’s water goals nationally. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/305557/original/file-20191206-39032-17fwb9c.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/305557/original/file-20191206-39032-17fwb9c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/305557/original/file-20191206-39032-17fwb9c.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/305557/original/file-20191206-39032-17fwb9c.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/305557/original/file-20191206-39032-17fwb9c.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/305557/original/file-20191206-39032-17fwb9c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/305557/original/file-20191206-39032-17fwb9c.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/305557/original/file-20191206-39032-17fwb9c.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Canada’s water opportunities and challenges.</span>
<span class="attribution"><span class="source">(Global Water Futures)</span></span>
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<p>Canada still has not reached universal access to reliable, potable water supplies for everyone, especially <a href="https://thetyee.ca/News/2019/10/17/First-Nations-Water-Crises-Explained/">First Nations communities</a>. Lead pipes, disinfection byproducts and aging infrastructure are interrupting drinking water service and negatively affecting human health. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/lead-tainted-water-how-to-keep-homes-schools-daycares-and-workplaces-safe-126815">Lead-tainted water: How to keep homes, schools, daycares and workplaces safe</a>
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<p>These water threats also cost our economy big time — as much as <a href="https://gwf.usask.ca/documents/meetings/water-security-for-canada/WaterSecurityForCanada_April-25-2019-2pg1.pdf">$28 billion between 2010 and 2017</a> — and those <a href="http://www.ibc.ca/on/resources/media-centre/media-releases/options-for-managing-the-flood-costs-of-canada%E2%80%99s-highest-risk-residential-properties">costs are rising</a>.</p>
<h2>The bottom line</h2>
<p>Canada already has the expertise, technologies, industries and research capacity to make good on a commitment to water sustainability and universal achievement of the UN’s water goals for all Canadians. But it needs leadership to advance research and practice to expand our existing strengths, and export these internationally. </p>
<p>Canadian research institutions have a role to play in bringing the country together by showing Canada and the world the solutions and benefits of achieving these goals. </p>
<p>There are significant long-term benefits at stake, including the enhanced health and well-being of current and future generations, as well as expanded economic opportunity. But, to achieve these, political leadership needs to transcend partisan lines in order to do what is right.</p>
<p>Ultimately, we have an opportunity to make where we live a better place and to get our own watersheds in order. This will help us create a better, more just, equitable and sustainable world for all. The alternative is, quite simply, unthinkable.</p><img src="https://counter.theconversation.com/content/127876/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Corinne Schuster-Wallace receives funding from Global Water Futures and the Canadian Tri-Agency. She is co-chair of the Working Group on Climate Change for the Canadian Coalition for Global Health Research. </span></em></p><p class="fine-print"><em><span>Robert Sandford receives partial funding from the Global Water Futures program at the University of Saskatchewan.</span></em></p><p class="fine-print"><em><span>Stephanie Merrill is a volunteer board member of the Saskatchewan branch and National board of the Canadian Water Resources Association and the Nashwaak Watershed Association.</span></em></p>The water that replenishes groundwater, rivers and lakes is under threat from climate change, pollution and aging infrastructure.Corinne Schuster-Wallace, Associate Professor, Department of Geography and Planning, University of SaskatchewanRobert Sandford, Chair in Water and Climate Security, Institute for Water, Environment and Health (UNU-INWEH), United Nations UniversityStephanie Merrill, Research Scientist, Knowledge Mobilization, Global Insitute for Water Security, Global Water Futures Program, University of SaskatchewanLicensed as Creative Commons – attribution, no derivatives.