tag:theconversation.com,2011:/au/topics/atmosphere-25442/articlesAtmosphere – The Conversation2024-02-26T13:38:23Ztag:theconversation.com,2011:article/2228512024-02-26T13:38:23Z2024-02-26T13:38:23ZHow is snow made? An atmospheric scientist describes the journey of frozen ice crystals from clouds to the ground<figure><img src="https://images.theconversation.com/files/576863/original/file-20240220-22-v6kq2o.jpg?ixlib=rb-1.1.0&rect=22%2C5%2C3764%2C2055&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some parts of the U.S. see well over 100 inches (2.5 meters) of snow per year.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/downhill-sledging-royalty-free-image/488074477?phrase=sledding+in+snow">Edoardo Frola/Moment Open via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<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>
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<p><strong>How is snow made? – Tenley, age 7, Rockford, Michigan</strong></p>
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<p>The thought of snow can conjure up images of powdery slopes, days out of school or hours of shoveling. For millions of people, it’s an inevitable part of life – but you may rarely stop to think about what made the snow.</p>
<p>As a <a href="https://www.eaps.purdue.edu/people/profile/ablanch.html">professor of atmospheric and planetary sciences</a>, <a href="https://scholar.google.com/citations?user=xClwTzUAAAAJ&hl=en&oi=ao">I’ve studied how ice crystals floating</a> in the sky become the snow that coats the ground.</p>
<p>It all starts in the clouds.</p>
<p>Clouds form when air near the Earth’s surface rises. This happens when sunlight warms the ground and the air closest to it, just like the Sun can warm your face on a cold winter day. </p>
<p>As the slightly warmer air rises, it cools – and the water vapor in that rising air condenses to form liquid water or water ice. From that, <a href="https://climatekids.nasa.gov/cloud-formation/#:%7E">a cloud is born</a>. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/Cf6El0mI1fM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">You need just two things for snow to form.</span></figcaption>
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<h2>Endless pathways</h2>
<p>When temperatures are well below freezing on the ground, the clouds are primarily made of water in the form of ice. Under 32 degrees Fahrenheit – that’s zero degrees Celsius – the frozen water molecules arrange themselves into a hexagonal, or six-sided, crystalline shape. As ice crystals grow and clump together, they become too heavy to stay aloft. With the help of gravity, they begin to fall back down through and eventually out of the cloud.</p>
<p>What these ice crystals look like once they reach land depends on the temperature and humidity of the atmosphere. As the humidity – or the amount of water vapor in the cloud – increases, some of the ice crystals will grow intricate arms at their six corners. That branching process creates what we think of as the <a href="https://www.timeforkids.com/g2/snowflake-science-g2-5-plus/?rl=en-500">characteristic shapes of snowflakes</a>. </p>
<p>No two ice crystals take the same path through a cloud. Instead, every ice crystal experiences different temperatures and humidities as it travels through the cloud, whether going up or down. The ever-changing conditions, combined with the infinite number of paths the crystals could take, result in a unique growth history and crystalline shape for each and every snowflake. This is why you’ve likely heard the saying, “<a href="https://www.willyswilderness.org/post/no-two-snowflakes-are-alike-it-s-actually-true">No two snowflakes are exactly alike</a>.” </p>
<p>Many times, these differences are visible to the naked eye; sometimes a microscope is required to tell them apart. Either way, scientists who study clouds and snow can examine a snowflake and ultimately understand the path it took through the cloud to land on your hand. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Snow crystals attached to a window." src="https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=636&fit=crop&dpr=1 600w, https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=636&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=636&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=799&fit=crop&dpr=1 754w, https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=799&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/576901/original/file-20240220-23-n5kry6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=799&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">It takes approximately one hour for a snowflake to reach the ground.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/snowflakes-royalty-free-image/158720307?phrase=snowflakes">LiLi/iStock via Getty Images Plus</a></span>
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<h2>Liquid water as glue</h2>
<p>When snow falls from the sky, you don’t usually see individual ice crystals, but rather clumps of <a href="https://scied.ucar.edu/learning-zone/storms/snowflakes">crystals stuck together</a>. One way ice crystals aggregate is through what’s called mechanical interlocking. When ice crystals bump into each other, crystals with intricate branches and arms intertwine and stick to others. </p>
<p>This mechanism is the main sticking process in cooler, drier conditions – what people call a “<a href="https://compuweather.com/the-important-difference-between-wet-snow-and-dry-snow/">dry snow</a>.” The result is a snow perfect for skiing, and easily picked up by the wind, but that won’t hold together when formed into a snowball. </p>
<p>The second way to stick ice crystals together is to warm them up a bit. When ice crystals fall through a region of cloud or atmosphere where the temperature is slightly above freezing, the edges of the crystals start to melt. Just a tiny bit of liquid water allows ice crystals that bump into each other to stick together very efficiently, almost like glue. </p>
<p>The result? Large clumps of ice crystals falling from the sky, what we call a “<a href="https://www.acurite.com/blog/types-of-snow.html">wet snow</a>” – less than ideal for hitting the slopes but perfect for building a snowman. </p>
<p>Snow formed in clouds typically reaches the ground only in winter. But almost all clouds, no matter the time of year or location, <a href="https://scijinks.gov/clouds/">contain some ice</a>. This is true even for clouds in warm tropical regions, because the atmosphere above us is much colder and can reach temperatures below freezing even on the warmest of days. In fact, scientists who study weather discovered that clouds containing ice produce more rain than those that don’t contain any ice at all.</p>
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<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>
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<p class="fine-print"><em><span>Alexandria Johnson receives funding from NASA. </span></em></p>There are an infinite number of paths an ice crystal can take before you touch it.Alexandria Johnson, Professor of Atmospheric and Planetary Sciences, Purdue UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2153952023-10-12T12:30:45Z2023-10-12T12:30:45ZWhat is a strong El Niño? Meteorologists anticipate a big impact in winter 2023-2024, but the forecasts don’t all agree<figure><img src="https://images.theconversation.com/files/553361/original/file-20231011-29-363wak.png?ixlib=rb-1.1.0&rect=32%2C873%2C3211%2C2058&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The El Niño pattern stands out in the warm sea surface temperature anomalies in the Pacific in 2023</span> <span class="attribution"><a class="source" href="https://www.climate.gov/maps-data/data-snapshots/data-source/sst-enso-region-monthly-difference-average">NOAA Climate.gov</a></span></figcaption></figure><p><em>Meteorologists have been talking for weeks about <a href="https://www.accuweather.com/en/winter-weather/us-winter-forecast-for-the-2023-2024-season/1583853">a snowy season ahead</a> in the southern Rockies and the Sierra Nevada. They anticipate <a href="https://www.powder.com/trending-news/el-nino-huge-snow-east">more storms</a> in the U.S. South and Northeast, and warmer, drier conditions across the already dry Pacific Northwest and the upper Midwest.</em></p>
<p><em>One phrase comes up repeatedly with these projections: <a href="https://www.wcpo.com/weather/weather-101/a-strong-el-nino-expected-this-winter-heres-what-that-means-for-our-weather">a strong El Niño</a> is coming.</em></p>
<p><em>It sounds ominous. But what does that actually mean? We asked <a href="https://scholar.google.com/citations?user=z7CXcXkAAAAJ&hl=en">Aaron Levine</a>, an atmospheric scientist at the University of Washington whose research focuses on El Niño.</em></p>
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<figcaption><span class="caption">NOAA explains in animations how El Niño forms.</span></figcaption>
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<h2>What is a strong El Niño?</h2>
<p>During a normal year, the warmest sea surface temperatures are in the western Pacific and the Indian Ocean, in what’s known as the <a href="https://doi.org/10.1186/s40562-016-0054-3">Indo-Western Pacific warm pool</a>.</p>
<p>But every few years, the trade winds that blow from east to west weaken, allowing that warm water to slosh eastward and <a href="https://www.pmel.noaa.gov/elnino/schematic-diagrams">pile up along the equator</a>. The warm water causes the air above it to warm and rise, fueling precipitation in the central Pacific and shifting atmospheric circulation patterns across the basin.</p>
<p>This pattern is <a href="https://www.pmel.noaa.gov/elnino/what-is-el-nino">known as El Niño</a>, and it can <a href="https://www.climate.gov/media/13628">affect weather around the world</a>.</p>
<figure class="align-center ">
<img alt="An animation shows how warm water builds up along the equator off South America. The box where temperatures are measured is south of Hawaii." src="https://images.theconversation.com/files/553048/original/file-20231010-23-c36xip.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553048/original/file-20231010-23-c36xip.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=272&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553048/original/file-20231010-23-c36xip.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=272&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553048/original/file-20231010-23-c36xip.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=272&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553048/original/file-20231010-23-c36xip.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=342&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553048/original/file-20231010-23-c36xip.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=342&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553048/original/file-20231010-23-c36xip.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=342&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The box shows the Niño 3.4 region as El Niño begins to develop in the tropical Pacific, from January to June 2023.</span>
<span class="attribution"><a class="source" href="https://www.climate.gov/">NOAA Climate.gov</a></span>
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<p>A strong El Niño, in the most basic definition, occurs once the average sea surface temperature in the equatorial Pacific is at least 1.5 degrees Celsius (2.7 Fahrenheit) warmer than normal. It’s measured in an imaginary box along the equator, roughly south of Hawaii, known as the <a href="https://svs.gsfc.nasa.gov/4695">Nino 3.4 Index</a>.</p>
<p>But El Niño is a coupled ocean-atmosphere phenomenon, and the atmosphere also plays a crucial role.</p>
<p>What has been surprising about this year’s El Niño – and still is – is that the atmosphere hasn’t responded as much as we would have expected based on the rising sea surface temperatures.</p>
<h2>Is that why El Niño didn’t affect the 2023 hurricane season the way forecasts expected?</h2>
<p>The 2023 Atlantic hurricane season is a good example. Forecasters often use El Niño as a predictor of <a href="https://www.weather.gov/ilx/swop-springtopics">wind shear</a>, which can tear apart Atlantic hurricanes. But with the atmosphere not responding to the warmer water right away, the impact on Atlantic hurricanes was lessened and it turned out to be a <a href="https://www.nytimes.com/article/tropical-storm-sean-hurricane.html">busy season</a>.</p>
<p><a href="https://doi.org/10.1175/JCLI-D-12-00097.1">The atmosphere is what transmits El Niño’s impact</a>. Heat from the warm ocean water causes the air above it to warm and rise, which fuels precipitation. That air sinks again over cooler water. </p>
<p>The rising and sinking creates giant loops in the atmosphere <a href="https://www.climate.gov/news-features/blogs/enso/walker-circulation-ensos-atmospheric-buddy">called the Walker Circulation</a>. When the warm pool’s water shifts eastward, that also shifts where the rising and sinking motions happen. The atmosphere reacts to this change like ripples in a pond when you throw a stone in. These ripples affect the jet stream, which steers weather patterns in the U.S.</p>
<p>This year, in comparison with other large El Niño events – such as <a href="https://www.climate.gov/news-features/blogs/enso/united-states-el-ni%C3%B1o-impacts-0">1982-83, 1997-98</a> and <a href="https://www.climate.gov/news-features/understanding-climate/2015-state-climate-el-ni%C3%B1o-came-saw-and-conquered">2015-16</a> – we’re not seeing the same change in where the precipitation is happening. It’s taking much longer to develop, and it’s not as strong.</p>
<p>Part of that, presumably, is related to the whole tropics being very, very warm. But <a href="https://doi.org/10.1029/2019GL086182">this is still an emerging field of research</a>.</p>
<p>How El Niño will change with global warming is a big and open question. El Niño <a href="https://www.climate.gov/news-features/understanding-climate/climate-variability-oceanic-nino-index">only happens every few years</a>, and there’s a fair amount of variability between events, so just getting a baseline is tough.</p>
<h2>What does a strong El Niño typically mean for US weather?</h2>
<p>During <a href="https://www.climate.gov/enso">a typical El Niño winter</a>, the U.S. South and Southwest are cooler and wetter, and the Northwest is warmer and drier. The upper Midwest tends to be drier, while the Northeast tends to be a little wetter. </p>
<p>The likelihood and the intensity generally scale with the strength of the El Niño event.</p>
<p>El Niño has traditionally been good for the mountain snowpack in California, which the state relies for a large percentage of its water. But it is often not so good for the Pacific Northwest snowpack.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/553424/original/file-20231012-15-3wfvdw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two maps showing wetter, cooler weather in the Southeast and drier warmer air in the north during El Nino." src="https://images.theconversation.com/files/553424/original/file-20231012-15-3wfvdw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553424/original/file-20231012-15-3wfvdw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=834&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553424/original/file-20231012-15-3wfvdw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=834&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553424/original/file-20231012-15-3wfvdw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=834&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553424/original/file-20231012-15-3wfvdw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1047&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553424/original/file-20231012-15-3wfvdw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1047&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553424/original/file-20231012-15-3wfvdw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1047&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 jet stream takes a very different path in a typical El Niño vs. La Niña winter weather pattern. But these patterns have a great deal of variability. Not every El Niño or La Niña year is the same.</span>
<span class="attribution"><a class="source" href="https://www.climate.gov/media/14484">NOAA Climate.gov</a></span>
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<p>The <a href="https://www.climate.gov/news-features/featured-images/how-el-ni%C3%B1o-and-la-ni%C3%B1a-affect-winter-jet-stream-and-us-climate">jet stream plays a role</a> in that shift. When the polar jet stream is either displaced very far northward or southward, storms that would normally move through Washington or British Columbia are steered to California and Oregon instead.</p>
<h2>What do the forecasts show for the months ahead?</h2>
<p>Whether forecasters think a strong El Niño will develop depends on whose forecast model they trust.</p>
<p>This past spring, the <a href="https://www.weather.gov/media/climateservices/NWS%20Climate%20Forecast%20and%20Tools.pdf">dynamical forecast models</a> were <a href="https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/?enso_tab=enso-sst_table">already very confident</a> about the potential for a strong El Niño developing. These are big models that solve basic physics equations, starting with current oceanic and atmospheric conditions. </p>
<p>However, statistical models, which use statistical predictors of El Niño calculated from historical observations, were less certain.</p>
<p>Even in the <a href="https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/?enso_tab=enso-sst_table">most recent forecast model outlook</a>, the dynamical forecast models were predicting a stronger El Niño than the statistical models were.</p>
<p>If you go by just a sea surface temperature-based El Niño index, the forecast is for a fairly strong El Niño. </p>
<p>But the indices that incorporate the atmosphere are not responding in the same way. We’ve seen <a href="https://psl.noaa.gov/enso/enso.current.html">atmospheric anomalies</a> – as measured by cloud height monitored by satellites or sea-level pressure at monitoring stations – on and off in the Pacific since May and June, <a href="https://images.theconversation.com/files/553327/original/file-20231011-15-kprvx9.png">but not in a very robust fashion</a>. Even in September, they were nowhere near as large as they were in 1982, in terms of overall magnitude.</p>
<p>We’ll see if the atmosphere catches up by wintertime, when El Niño peaks.</p>
<h2>How long do El Niños last?</h2>
<p>Often during El Niño events – particularly strong El Niño events – the sea surface temperature anomalies collapse really quickly during the Northern Hemisphere spring. Almost all end in April or May.</p>
<p>One reason is that El Niño sows the seeds of its own demise. When El Niño happens, it <a href="https://doi.org/10.1175/1520-0469(1997)054%3C0811:AEORPF%3E2.0.CO;2">uses up that warm water</a> and the warm water volume shrinks. <a href="https://doi.org/10.1175/1520-0442(2000)013%3C3551:OOWWVC%3E2.0.CO;2">Eventually, it has eroded its fuel</a>.</p>
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<p>The surface can stay warm for a while, but once the heat from the subsurface is gone and the trade winds return, the El Niño event collapses. At the end of past El Niño events, the sea surface anomaly dropped very fast and we saw conditions typically switch to La Niña – El Niño’s cooler opposite.</p><img src="https://counter.theconversation.com/content/215395/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Aaron Levine receives funding from NOAA and has received funding in the past from the National Research Council. He is a member of the American Geophysical Union </span></em></p>An atmospheric scientist explains how El Niño works, this year’s oddities and why this phenomenon doesn’t last long.Aaron Levine, Atmospheric Research Scientist, CICOES, University of WashingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2137242023-09-19T12:18:13Z2023-09-19T12:18:13ZAs extreme downpours trigger flooding around the world, scientists take a closer look a global warming’s role<p>Torrential downpours sent muddy water racing through streets in <a href="https://www.washingtonpost.com/world/2023/09/14/libya-flood-death-toll-derna-news/">Libya</a>, <a href="https://twitter.com/WxNB_/status/1699014872015479212">Greece</a> and <a href="https://www.theguardian.com/world/2023/sep/05/boy-rescued-from-flood-waters-after-record-heavy-rain-in-spain">Spain</a> and flooded parts of <a href="https://www.straitstimes.com/asia/east-asia/hong-kong-hit-with-heavy-rain-flooding-days-after-typhoon">Hong Kong</a> and <a href="https://www.nytimes.com/2023/09/29/nyregion/nyc-flooding-video-photo.html">New York City</a> in September 2023. Thousands of people died in the city of Derna, Libya. Zagora, Greece, saw a record 30 inches of rain, the equivalent of <a href="https://public.wmo.int/en/media/news/storm-daniel-leads-extreme-rain-and-floods-mediterranean-heavy-loss-of-life-libya">a year and a half of rain falling in 24 hours</a>.</p>
<p>A few weeks earlier, monsoon rains triggered deadly landslides and flooding in <a href="https://www.youtube.com/watch?v=8VMBIlKjuKg">the Himalayas</a> that <a href="https://www.pbs.org/newshour/world/heavy-rain-landslides-have-killed-at-least-72-people-this-week-in-indias-himalayas">killed dozens of people</a> in India.</p>
<p>After severe flooding on almost every continent this year, including <a href="https://theconversation.com/epic-snow-from-all-those-atmospheric-rivers-in-the-west-is-starting-to-melt-and-the-flood-danger-is-rising-203874">mudslides and flooding in California</a> in early 2023 and devastating <a href="https://theconversation.com/how-climate-change-intensifies-the-water-cycle-fueling-extreme-rainfall-and-flooding-the-northeast-deluge-was-just-the-latest-209476">floods in Vermont and New York</a> in July, it can seem like extreme rainfall is becoming more common.</p>
<p>So, what role does global warming play in this? And importantly, what can we do to adapt to this new reality?</p>
<figure class="align-center ">
<img alt="A man and woman sit on a park bench with water up to the man's knees. The woman is sitting on the chair back. A car in the street is flooded up to the roof." src="https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/544111/original/file-20230822-17-ybv7br.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A powerful storm system in 2023 flooded communities across Vermont and left large parts of the capital, Montpelier, underwater.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/michelle-whitehouse-and-her-husband-will-whitehouse-from-news-photo/1526471468">John Tully for The Washington Post via Getty Images</a></span>
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<p>As a <a href="https://clasp.engin.umich.edu/people/mohammed-ombadi/">climate scientist</a> with a background in civil engineering, I am interested in exploring the links between the science of climate change and extreme weather events on one hand and the impacts those events have on our daily lives on the other. Understanding the connections is crucial in order to develop sound strategies to adapt to climate change.</p>
<h2>Thirstier atmosphere, more extreme precipitation</h2>
<p>As temperatures rise, the warmer atmosphere can <a href="https://sealevel.jpl.nasa.gov/ocean-observation/understanding-climate/air-and-water/">hold more water vapor</a>. Evaporation of water from land and oceans also increases. That water has to eventually come back to land and oceans. </p>
<p>Simply, as the atmosphere absorbs more moisture, it dumps more precipitation during storms. Scientists expect about a <a href="https://science2017.globalchange.gov/chapter/7/">7% increase</a> in precipitation intensity during extreme storms for every 1 degree Celsius (1.8 degrees Fahrenheit) of warming. </p>
<p>This increase in the amount of moisture that air can hold is what scientists call the <a href="https://doi.org/10.1073/pnas.2304077120">Clausius Clapeyron relationship</a>. But other factors, such as changes in wind patterns, <a href="https://doi.org/10.1073/pnas.2304077120">storm tracks and how saturated the air is</a>, also play a role in how intense the precipitation is.</p>
<h2>Liquid vs. frozen: Rain matters most</h2>
<p>One factor that determines the severity of floods is whether water falls as rain or snow. The almost instantaneous runoff from rain, as opposed to the slower release of water from melting snow, leads to more severe flooding, landslides and other hazards – particularly in mountain regions and areas downstream, where about a quarter of the global population lives. </p>
<p>A higher proportion of extreme rainfall rather than snow is believed to have been a key contributor to the <a href="https://www.bbc.com/news/world-asia-india-66519698">devastating floods and landslides in the Himalayas</a> in August 2023, though research is still underway to confirm that. Additionally, a <a href="https://doi.org/10.1029/2019WR025571">2019 examination of flood patterns</a> across 410 watersheds in the Western U.S. found that the largest runoff peaks driven by rainfall were more than 2.5 times greater than those driven by snowmelt.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Maps show the US and other regions of the Northern Hemisphere with rising rainfall intensity. Western North America and the Himalayas stand out" src="https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548585/original/file-20230915-29-73yoeq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Rainfall intensity is projected to increase more in certain regions by the end of the 21st century, based on climate model data. Light colors show a twofold increase and dark colors indicate an eightfold increase in future rainfall extremes compared to the recent past.</span>
<span class="attribution"><span class="source">Mohammed Ombadi.</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>In a <a href="https://doi.org/10.1038/s41586-023-06092-7">2023 study in the journal Nature</a>, my colleagues and I demonstrated that the intensity of extreme precipitation is increasing at a faster rate than the Clausius Clapeyron relationship would suggest – up to 15% per 1 C (1.8 F) of warming – in high-latitude and mountain regions such as the Himalayas, Alps and Rockies.</p>
<p>The reason for this amplified increase is that rising temperatures are shifting precipitation toward more rain and less snow in these regions. A larger proportion of this extreme precipitation is falling as rain.</p>
<p>In our study, we looked at the heaviest rains in the Northern Hemisphere since the 1950s and found that the increase in the intensity of extreme rainfall varied with altitude. Mountains in the American West, parts of the Appalachian Mountains, the Alps in Europe and the Himalayas and Hindu Kush mountains in Asia also showed strong effects. Furthermore, climate models suggest that most of these regions are likely to see a sevenfold-to-eightfold increase in the occurrence of extreme rainfall events by the end of the 21st century.</p>
<h2>Flooding isn’t just a short-term problem</h2>
<p>Deaths and damage to homes and cities capture the lion’s share of attention in the aftermath of floods, but increased flooding also has long-term effects on water supplies in reservoirs that are crucial for communities and agriculture in many regions. </p>
<p>For example, in the Western U.S., reservoirs are often kept as close to full capacity as possible during the spring snowmelt to provide water for the dry summer months. The mountains act as natural reservoirs, storing winter snowfall and then releasing the melted snow at a slow pace.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=527&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=527&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548589/original/file-20230915-27-tbcn9v.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=527&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A series of atmospheric rivers in California dumped so much water on the region that Tulare Lake, which had dried up years earlier, reemerged as water spread across miles of California farmland.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/agribusiness-consultant-mark-grewel-stands-on-a-farm-road-news-photo/1249529651">Luis Sinco / Los Angeles Times via Getty Images</a></span>
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<p>However, <a href="https://doi.org/10.1038/s41586-023-06092-7">our recent findings</a> suggest that with the world rapidly shifting toward a climate dominated by heavy downpours of rain – not snow – water resource managers will increasingly have to leave more room in their reservoirs to store large amounts of water in anticipation of disasters to minimize the risk of flooding downstream.</p>
<h2>Preparing for a fiercer future</h2>
<p>Global efforts to reduce greenhouse gas emissions have been increasing, but people still need to prepare for a fiercer climate. The destructive <a href="https://public.wmo.int/en/media/news/storm-daniel-leads-extreme-rain-and-floods-mediterranean-heavy-loss-of-life-libya">storms that hit the Mediterranean region</a> in 2023 provide a cogent case for the importance of adaptation. They shattered records for extreme precipitation across many countries and caused extensive damage.</p>
<p>A main factor that contributed to the catastrophe in Libya was the <a href="https://theconversation.com/libya-dam-collapse-happened-because-of-bad-management-not-bad-weather-213546">bursting of aging dams</a> that had managed water pouring down from <a href="https://www.washingtonpost.com/world/2023/09/12/deadly-libya-flooding-cause/">mountainous terrain</a>.</p>
<p>This underscores the importance of updating design codes so infrastructure and buildings are built to survive future downpours and flooding, and investing in new engineering solutions to improve resiliency and protect communities from extreme weather. It may also mean <a href="https://theconversation.com/managed-retreat-done-right-can-reinvent-cities-so-theyre-better-for-everyone-and-avoid-harm-from-flooding-heat-and-fires-163052">not building in regions</a> with high future risks of flooding and landslides.</p>
<p><em>This article, originally published Sept. 19, 2023, has been updated with flooding in New York City.</em></p><img src="https://counter.theconversation.com/content/213724/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mohammed Ombadi has received funding from Lawrence Berkeley National Laboratory to conduct the Nature study discussed in this article. </span></em></p>There’s a rule of thumb that rainfall intensity increases by about 7% per degree Celsius as temperatures rise. But the increase is much higher in the mountains, scientists found.Mohammed Ombadi, Assistant Professor of Climate and Space Sciences Engineering, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2133942023-09-13T13:57:15Z2023-09-13T13:57:15ZPossible hints of life found on distant planet – how excited should we be?<figure><img src="https://images.theconversation.com/files/547762/original/file-20230912-19-lzosd4.jpeg?ixlib=rb-1.1.0&rect=5%2C0%2C3811%2C2160&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The exoplanet K2-18b might host a water ocean.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18b">Credits: Illustration: NASA, CSA, ESA, J. Olmsted (STScI), Science: N. Madhusudhan (Cambridge University)</a></span></figcaption></figure><p>Data from the <a href="https://webb.nasa.gov/">James Webb Space Telescope</a> (JWST) has shown that an exoplanet around a star in the constellation Leo has some of the chemical markers that, on Earth, are associated with living organisms. But these are vague indications. So how likely is it that this exoplanet harbours alien life?</p>
<p>Exoplanets are worlds that orbit stars other than the Sun. The planet in question is named <a href="http://www.exoplanetkyoto.org/exohtml/K2-18.html">K2-18b</a>. It’s so named because it was the first planet found to orbit the red dwarf star K2-18. There is a K2-18c as well – the second planet to be discovered. The star itself is dimmer and cooler than the Sun, meaning that, to get the same level of light as we do on Earth, the planet would need to be much closer to its star than we are. </p>
<p>The system is roughly 124 light years away, which is close in astronomical terms. So what are conditions like on this exoplanet? This is a difficult question to answer. We have telescopes and techniques powerful enough to tell us what the star is like, and how far away the exoplanet is, but we can’t capture direct images of the planet. We can work out a few basics, however. </p>
<p>Working out how much light hits K2-18b is important for assessing the planet’s potential for life. K2-18b orbits closer to its star than Earth does: it’s at roughly 16% of the distance from Earth to the Sun. Another measurement we need is the star’s power output: the total amount of energy it radiates per second. K2-18’s power output is 2.3% that of the Sun. </p>
<p>Using geometry, we can work out that K2-18b receives about 1.22 kilowatts (kW) in solar power per square metre. <a href="https://www.sws.bom.gov.au/Educational/2/1/12">This is similar</a> to the 1.36 kW of incoming light we receive on Earth. Although there’s less energy coming from K2-18, it evens out because the planet is closer. So far, so good. However, the incoming light calculation doesn’t take into account clouds or how reflective the planet’s surface is.</p>
<figure class="align-center ">
<img alt="JWST" src="https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?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">Artist’s impression of the James Webb Space Telescope (JWST).</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/feature/ames/webb">NASA</a></span>
</figcaption>
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<p>When we consider life on other planets, a popular term to use is the <a href="https://exoplanets.nasa.gov/search-for-life/habitable-zone/">habitable zone</a>, which means that at an average surface temperature, water will be in a liquid state – as this condition is considered essential for life. In 2019, the Hubble Space Telescope determined that K2-18b showed signs of <a href="https://www.nature.com/articles/s41550-019-0878-9#change-history">water vapour</a>, suggesting that liquid water would be present on the surface. It is currently thought that there are large oceans on the planet.</p>
<p>This caused a ripple of excitement at the time, but without further evidence it was just an interesting result. Now we have reports that JWST has identified carbon dioxide, methane and – possibly – the compound dimethyl sulfide (DMS) <a href="https://www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18b">in the atmosphere</a>. The tentative detection of DMS is significant because it is only produced on Earth by <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/dimethyl-sulfide">algae</a>. We currently know of no way it can be naturally produced without a life-form.</p>
<h2>Is there life on K2-18b?</h2>
<p>All these indications seem to suggest that K2-18b might be the place to go to find alien life. It is not quite as simple as that, though, as we have no idea how accurate the results are. The method used to determine what is in the atmosphere of an exoplanet involves light from a different source (usually a star or galaxy) passing through the edge of the atmosphere that is then observed by us. Any chemical compounds will <a href="https://webbtelescope.org/contents/media/images/01FEE26XVSM851DHPVCE1KB4S2">absorb light in specific wavelengths</a> which can then be identified. </p>
<p>Imagine it as looking at a light bulb through a glass tumbler. You can see through it perfectly when empty. If you fill it with water, you can still see through pretty well, but there are some optical effects and colouration, which are the equivalent of hydrogen and dust clouds in space. Now imagine you poured in red food dye – this might be the equivalent of the main chemical constituent in a planet’s atmosphere. </p>
<p>But most atmospheres are made up of many chemicals. The equivalent of looking for any one of them would be like pouring 50 – likely many more – coloured food dyes, in different amounts, into your tumbler and trying to identify how much of one particular colour is present. It is an incredibly difficult task with plenty of room for subjective assessment and errors. In addition, the light going through the atmosphere contains a signal of the star’s chemical constituents – further complicating the analysis.</p>
<figure class="align-center ">
<img alt="Atmospheric composition of K2-18 b." src="https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?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">The chemical composition of K2-18b’s atmosphere.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18b">Credits: Illustration: NASA, CSA, ESA, R. Crawford (STScI), J. Olmsted (STScI), Science: N. Madhusudhan (Cambridge University)</a></span>
</figcaption>
</figure>
<p>Only a few years ago there was a surge of interest in <a href="https://www.nytimes.com/2020/09/14/science/venus-life-clouds.html">whether life existed on Venus</a>, as observations had indicated the presence of phosphine gas, which can be produced by microbes. </p>
<p>However, this finding was later successfully refuted by <a href="https://arxiv.org/pdf/2010.09761.pdf">several studies</a>. If there can be confusion about what is in the atmosphere of a planet that’s just next door, in astronomical terms, it’s easy to see why analysing a planet that’s many times further away is a difficult task.</p>
<h2>What can we take from this?</h2>
<p>The chances of life on exoplanet K2-18b are low but not impossible. These results will likely not change anybody’s opinions or beliefs about extraterrestrial life. Instead, they do demonstrate the advancing ability to look into worlds that are not our own and find more information. </p>
<figure class="align-center ">
<img alt="Rho Ophiuchi" src="https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=562&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=562&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=562&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=706&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=706&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=706&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">JWST image of Rho Ophiuchi, the closest star-forming region to Earth.</span>
<span class="attribution"><a class="source" href="https://webbtelescope.org/contents/media/images/2023/128/01H449193V5Q4Q6GFBKXAZ3S03?news=true">NASA, ESA, CSA, STScI, Klaus Pontoppidan (STScI)</a></span>
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<p>The power of JWST is not only in producing incredible pictures, but in providing <a href="https://webbtelescope.org/contents/news-releases/2023/news-2023-103.html">more detailed</a> and accurate data on celestial objects themselves. Knowing which exoplanets host water and which do not could provide information on how the Earth formed. </p>
<p>Studying the atmospheres of gas giant exoplanets can inform the study of similar worlds in the Solar System, such as Jupiter and Saturn. And identifying levels of CO2 indicates how an extreme greenhouse effect might affect a planet. This is the real power of studying the composition of planetary atmospheres.</p><img src="https://counter.theconversation.com/content/213394/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Whittaker does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The results are intriguing, but analysing the atmospheres of exoplanets is no easy task.Ian Whittaker, Senior Lecturer in Physics, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2134582023-09-13T07:13:57Z2023-09-13T07:13:57ZSigns of life? Why astronomers are excited about carbon dioxide and methane in the atmosphere of an alien world<figure><img src="https://images.theconversation.com/files/547922/original/file-20230913-23-zphpi7.jpeg?ixlib=rb-1.1.0&rect=28%2C5%2C3805%2C2149&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA / CSA / ESA / J. Olmsted (STScI) / Science: N. Madhusudhan (Cambridge University)</span></span></figcaption></figure><p>Are we alone? This question is nearly as old as humanity itself. Today, this question in astronomy focuses on finding life beyond our planet. Are we, as a species, and as a planet, alone? Or is there life somewhere else?</p>
<p>Usually the question inspires visions of weird, green versions of humans. However, life is more than just us: animals, fish, plants and even bacteria are all the kinds of things we seek signs of in space.</p>
<p>One thing about life on Earth is that it leaves traces in the chemical makeup of the atmosphere. So traces like that, which are visible from a long way away, are something we look for when we’re hunting aliens. </p>
<p>Scientists in the United Kingdom and the United States <a href="https://arxiv.org/abs/2309.05566">have just reported</a> some very interesting chemical traces in the atmosphere of a planet called K2-18b, which is about 124 light-years from Earth. In particular, they may have detected a substance which on Earth is only produced by living things. </p>
<h2>Meet exoplanet K2-18b</h2>
<p>K2-18b is an interesting exoplanet – a planet that orbits another star. Discovered in 2015 by the Kepler Space Telescope’s K2 mission, it is a type of planet called a sub-Neptune. As you probably guessed, these are smaller than Neptune in our own Solar System.</p>
<p>The planet is about eight and a half times heavier than Earth, and orbits a type of star called a red dwarf, which is much cooler than our Sun. However, K2-18b orbits much closer to its star than Neptune does – in what we call the habitable zone. This is the area that is not too hot and not too cold, where liquid water can exist (instead of freezing to ice or boiling into steam).</p>
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<p>Earth is what is called a rocky planet (for obvious reasons), but sub-Neptunes are gas planets, with much larger atmospheres containing lots of hydrogen and helium. Their atmosphere can also contain other elements.</p>
<p>Which brings us to the excitement around K2-18b. </p>
<h2>How to fingerprint an atmosphere</h2>
<p>The planet was first discovered by the Kepler Space Telescope, which was monitoring distant stars and hoping for planets to pass in front of them. When a planet does pass between us and a star, the star becomes momentarily dimmer – which is what tells us a planet is there.</p>
<p>By measuring how big the dip in brightness is, how long it takes for the planet to pass in front of the star, and how often it happens, we can work out the size and orbit of the planet. This technique is great at finding planets, but it doesn’t tell us about their atmospheres – which is a key piece of information to understand if they hold life or are habitable.</p>
<p>NASA’s James Webb Space Telescope – the big space telescope launched at the end of 2021 – has now observed and measured the atmosphere of this exoplanet. </p>
<p>The telescope did this by measuring the colour of light so finely, it can detect traces of specific atoms and molecules. This process, called spectroscopy, is like measuring the fingerprint of elements. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A chart showing the absorption of different wavelengths of light by the atmosphere of K2-18b, and which wavelengths correspond to different substances in the atmosphere." src="https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The atmosphere of the exoplanet K2-18b showed strong signs of methane and carbon dioxide, as well as a weak indication of dimethyl sulfide.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18b">NASA / CSA / ESA / R. Crawford (STScI) / J. Olmsted (STScI) / N. Madhusudhan (Cambridge University)</a></span>
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<p>Each element and molecule has its own colour signature. If you can look at the colour signature, you can do a bit of detective work, and work out what elements or compounds are in the planet.</p>
<p>While the planet does not have its own light, astronomers waited for when K2-18b passed in front of its star, and measured the starlight as it went through the planet’s atmosphere, allowing the team to detect fingerprints of substances in the atmosphere.</p>
<h2>Alien marine farts?</h2>
<p>The new study found a lot of carbon dioxide and methane. This is interesting as this is like what is found on Earth, Mars, and Venus in our Solar System – rather than Neptune.</p>
<p>However, it also found a small amount of dimethyl sulfide. Dimethyl sulfide is an interesting molecule, made up of carbon, hydrogen, and sulfur.</p>
<p>On Earth, it’s generally a bit smelly. But it’s also closely linked to life.</p>
<p>The only process we know that creates dimethyl sulfide on our planet is life. In particular, marine life and plankton emit it in the form of flatulence.</p>
<p>So yes, scientists are excited by the potential idea of alien marine farts. If it is real. And linked to life.</p>
<h2>The search continues</h2>
<p>While on Earth, dimethyl sulfide is linked to life, on other planets it may somehow be related to geological or chemical processes.</p>
<p>After all, K2-18b is something like Neptune – a planet we do not really know a lot about. Just last month, researchers discovered that <a href="https://www.sciencedirect.com/science/article/abs/pii/S0019103523002440">clouds on Neptune are strongly linked</a> to the Sun’s 11-year cycle of activity. We have a lot to learn about planets and their atmospheres.</p>
<p>Also, the measurement of dimethyl sulfide is very subtle – not nearly as strong as the carbon dioxide and methane. This means more detailed measurements, to improve the strength of the signal, are required. </p>
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Read more:
<a href="https://theconversation.com/the-webb-telescope-has-released-its-very-first-exoplanet-image-heres-what-we-can-learn-from-it-189876">The Webb telescope has released its very first exoplanet image – here's what we can learn from it</a>
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<p>Other telescopes may need to join the effort. Instruments on the Very Large Telescope in Chile are able to measure the atmospheres of planets around other stars – as is a new instrument called Veloce on the Anglo Australian Telescope at Siding Spring Observatory in Australia.</p>
<p>And new space telescopes, like Europe’s PLATO which is under construction, will also help us get a better look at alien atmospheres.</p>
<p>So while the signs of dimethyl sulfide on K2-18b may not be linked to life, they are still an exciting prospect. There is plenty more to explore.</p><img src="https://counter.theconversation.com/content/213458/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brad E Tucker receives funding from the Australian Research Council and Australian Capital Territory Government. </span></em></p>The James Webb Space Telescope has detected key carbon-bearing molecules on the potential ocean world K2-18b, including tantalising hints of a substance produced by tiny plankton on Earth.Brad E Tucker, Astrophysicist/Cosmologist, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2112112023-08-14T15:35:44Z2023-08-14T15:35:44ZRising methane could be a sign that Earth’s climate is part-way through a ‘termination-level transition’<figure><img src="https://images.theconversation.com/files/542605/original/file-20230814-9314-9s19nb.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5472%2C3645&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Soaring wetland emissions of methane mirror those which accompanied previous abrupt changes in Earth's climate.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/scientist-collecting-sediment-core-asses-carbon-1986241904">I. Noyan Yilmaz/Shutterstock</a></span></figcaption></figure><p>Since 2006, the amount of heat-trapping methane in Earth’s atmosphere has been rising fast and, unlike the rise in carbon dioxide (CO₂), methane’s recent increase seems to be driven by biological emissions, not the burning of fossil fuels. This might just be ordinary variability – a result of natural climate cycles such as <a href="https://theconversation.com/uk/topics/el-nino-southern-oscillation-61187">El Niño</a>. Or <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023GB007875">it may signal</a> that a great transition in Earth’s climate has begun.</p>
<p>Molecule for molecule, methane is a much more potent greenhouse gas than CO₂ but it lasts slightly less than a decade in the atmosphere compared with centuries for CO₂. Methane emissions threaten humanity’s ability to limit warming to relatively safe levels. Even more troubling, the rate at which methane is increasing in the atmosphere has accelerated recently. Something like this has happened before: sudden surges in methane marked the transitions from cold ice ages to warm interglacial climates.</p>
<p>Methane was about <a href="https://www.science.org/doi/full/10.1126/science.1115193?casa_token=SO-68A9Lm3QAAAAA:updtgEm-JlhLIaCTTldcjAWM4dVriBaMQIxZL14LwlVbB-qIeQHcLmyZfGA7v9fSjZKliUmXAv_DI6s">0.7 parts per million</a> (ppm) of the air before humans began burning fossil fuels. Now it is <a href="https://gml.noaa.gov/ccgg/trends_ch4/">over 1.9 ppm</a> and rising fast. Roughly three-fifths of emissions come from fossil fuel use, farming, landfills and waste. The remainder is from natural sources, especially vegetation rotting in tropical and northern wetlands.</p>
<p>Methane is both a driver and a messenger of climate change. We don’t know why it is now rising so rapidly, but the pattern of growth since late 2006 resembles how methane behaved during great flips in Earth’s climate in the distant past.</p>
<h2>The methane record: 2006 to present</h2>
<p>In late 2006, atmospheric methane unexpectedly <a href="https://www.science.org/doi/full/10.1126/science.1247828?casa_token=ZtY4QHzYPL8AAAAA:aXanfP6nE_aHHNnODZCRtCkojp78rOg5fKIvKgnU7fWVRrypW0ln9TEchFLxtUFyyUzr1JQh_MI364U">began rising</a>. Methane had risen fast in the 19th and 20th centuries but plateaued by the end of the 1990s. This rise was driven by fossil fuel emissions, especially from gasfields and coal mines.</p>
<p>Imagine accelerating a car with your foot flat down. The car speeds up but eventually air resistance equals engine power and the car hits maximum speed. In 1999, it looked like methane had reached a similar equilibrium between its sources and sinks. Then in late 2006, the amount of methane in the air <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GB005406">climbed fast</a>. Even more unexpectedly five years later, the rate of growth <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsta.2020.0440">sped up again</a>. During the 2020s the growth rate has become yet faster, faster even than during the peak of gas industry leaks <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023GB007875">in the 1980s</a>.</p>
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<img alt="A line graph showing methane in the air rising rapidly from 2006." src="https://images.theconversation.com/files/542595/original/file-20230814-19-qrx4vh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/542595/original/file-20230814-19-qrx4vh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/542595/original/file-20230814-19-qrx4vh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/542595/original/file-20230814-19-qrx4vh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/542595/original/file-20230814-19-qrx4vh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/542595/original/file-20230814-19-qrx4vh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/542595/original/file-20230814-19-qrx4vh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&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">Methane in the air rose rapidly from 2006 – then it rose again, and again.</span>
<span class="attribution"><a class="source" href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023GB007875">NOAA/Nisbet et al. (2023)</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Today’s growth seems to be driven by <a href="https://acp.copernicus.org/articles/23/4863/2023/acp-23-4863-2023.html">new emissions</a> from <a href="https://www.nature.com/articles/s43247-022-00488-5">wetlands</a>, especially near the equator but perhaps also from Canada (<a href="https://www.nature.com/articles/334295a0">beavers are methane factories</a> which pull <a href="https://cdnsciencepub.com/doi/abs/10.1139/z88-076">huge amounts of plant matter</a> into ponds they’ve made) and Siberia. This is a result of climate change: increasing rainfall has made wetlands wetter and bigger while rising temperatures have boosted plant growth, providing more decomposing matter and so more methane. Emissions from huge cattle lots in tropical Africa, India and Brazil may also be <a href="https://edgar.jrc.ec.europa.eu/dataset_ghg70">rising</a> and rotting waste in <a href="https://www.science.org/doi/full/10.1126/sciadv.abn9683">landfills</a> near megacities like Delhi are important sources too. </p>
<h2>Climate terminations</h2>
<p>In the past <a href="https://www.episodes.org/journal/view.html?volume=31&number=2&spage=211&vmd=Full">few million years</a>, Earth’s climate has <a href="https://www.pnas.org/doi/abs/10.1073/pnas.1613883114">flipped repeatedly</a> between long, cold glacial periods, with ice sheets covering northern Europe and Canada, and shorter warm inter-glacials. </p>
<p>When each ice age ended, Earth’s surface warmed by as much as several degrees centigrade over a few millennia. Recorded in air bubbles in ice cores, sharply rising methane concentrations are the bellwethers of these great climate-warming events. With each flip from a glacial to an interglacial climate there have been sudden, sharp rises in atmospheric methane, likely from <a href="https://www.pnas.org/doi/abs/10.1073/pnas.1613883114">expanding tropical wetlands</a>.</p>
<p>These great climate flips that ended each ice age are known as <a href="https://www.sciencedirect.com/science/article/pii/0277379190900267?casa_token=Gowdxvu24OcAAAAA:2CHMqxymEdYWZXRZzDYYNALL5iHHUp5_pZbvSFTW1GiUw9tSXY-a6jHCYolLpVlx0Dte-fLbmuA">terminations</a>. Each has a Roman numeral, ranging from Termination IX which happened about 800,000 years ago to Termination IA which initiated the modern climate less than <a href="https://www.pnas.org/doi/epdf/10.1073/pnas.2007869117">12,000 years ago</a>. For example, around <a href="https://www.sciencedirect.com/science/article/pii/S0277379115300512">131,000 years ago</a> during Termination II, the British climate suddenly flipped from glaciers in the Cotswolds to hippopotami wallowing in what is now Trafalgar Square.</p>
<p>Full terminations take several thousands of years to complete, but many include a creeping onset of warming, then a very abrupt phase of extremely rapid climate change that can take <a href="https://www.nature.com/articles/34346">a century or less</a>, followed by a longer, slower period during which the great ice caps finally melt. In the abrupt phase of the great change that brought about the modern climate, Greenland’s temperature rose by around 10°C within a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0277379104003245?via%3Dihub">few decades</a>. During these abrupt phases, methane climbs very steeply indeed.</p>
<h2>Is something dramatic underway?</h2>
<p>Methane fluctuated widely in pre-industrial times. But its increasingly rapid growth since 2006 is comparable with records of methane from the early years of abrupt phases of past termination events, like the one that warmed Greenland so dramatically <a href="https://www.sciencedirect.com/science/article/abs/pii/S0277379104003245?via%3Dihub">less than 12,000 years ago</a>.</p>
<p>There is already lots of evidence that the climate is shifting. Atlantic ocean currents are <a href="https://www.nature.com/articles/s41558-021-01097-4.">slowing</a>, tropical weather regions are <a href="https://www.nature.com/articles/s41558-018-0227-5">expanding</a>, the far north and south are <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac0acc/meta">warming fast</a>, <a href="https://link.springer.com/article/10.1007/s00376-023-2385-2">ocean heat</a> is breaking records and <a href="https://www.nature.com/articles/s43017-023-00397-x">extreme weather</a> is becoming routine.</p>
<p>In glacial terminations, the entire climate system reorganises. In the past, this took Earth out of stable ice age climates and into warm inter-glacials. But we are already in a warm interglacial. What comes next is hard to imagine: loss of sea ice in the Arctic in summer, thinning or partial collapse of the ice caps in Greenland and West Antarctica, reorganisation of the Atlantic’s ocean currents and the poleward expansion of tropical weather circulation patterns. The consequences, both for the biosphere in general and food production in south and east Asia and parts of Africa in particular, would be very significant.</p>
<p>There’s much to be done that could hastily <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019RG000675">stop methane’s rise</a>: plugging leaks in the oil and gas industry, covering landfills with soil, reducing crop-waste burning. Shooting the methane messenger won’t stop climate change, which is primarily driven by CO₂ emissions, but it will help. </p>
<p>Roman numerals IX to I denote past great climate transitions. There is no Roman number zero, but then any future termination-scale transition will be different – a temperature step from our present interglacial climate to some new future that is warmer yet. Methane’s signal is still unclear, but the question remains: has <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023GB007875">Termination Zero</a> begun?</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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</figure>
<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
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<hr><img src="https://counter.theconversation.com/content/211211/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Euan Nisbet receives funding from the Natural Environment Research Council and the European Union. All studies of greenhouse gases in the modern atmosphere are underpinned by data from US NOAA's Cooperative Air Sampling Network, a partnership of volunteers sampling a globally distributed network of sites.</span></em></p>The last time methane in the air rose so fast, Greenland warmed by 10°C within decades.Euan Nisbet, Professor of Earth Sciences, Royal Holloway University of LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2098692023-07-18T20:02:02Z2023-07-18T20:02:02ZDid the Anthropocene start in 1950 – or much earlier? Here’s why debate over our world-changing impact matters<figure><img src="https://images.theconversation.com/files/537960/original/file-20230718-29-f4vh8k.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3853%2C2549&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>It made world news last week when a small lake in Canada was chosen as the “<a href="https://www.vox.com/future-perfect/2023/7/11/23791629/anthropocene-climate-epoch-canada-lake-crawford">Golden Spike</a>” – the location where the emergence of the Anthropocene is most clear. The Anthropocene is the proposed new geological epoch defined by humanity’s impact on the planet. </p>
<p>It took 14 years of scouring the world before the geoscientists in the <a href="http://quaternary.stratigraphy.org/working-groups/anthropocene">Anthropocene Working Group</a> chose Lake Crawford – the still, deep waters of which are exceptionally good at <a href="https://www.nytimes.com/2023/07/11/climate/anthropocene-epoch-crawford-lake.html">preserving history</a> in the form of sediment layers. Core samples from the lake give us an unusually good record of geological change, including, some scientists believe, the moment we began to change everything. For this group, that date is around 1950. </p>
<p>But what didn’t get reported was the resignation of a key member, global ecosystem expert Professor Erle Ellis, who left the working group and published an <a href="https://anthroecology.org/why-i-resigned-from-the-anthropocene-working-group">open letter</a> about his concerns. In short, Ellis believes pinning the start of our sizeable impact on the planet to 1950 is an error, given we’ve been changing the face of the planet for much longer. </p>
<p>The other working group scientists argue 1950 is well chosen, as it’s when humans started to really make their presence felt through surging populations, fossil fuel use and deforestation, amongst other things. This phenomenon has been dubbed the <a href="http://www.igbp.net/news/pressreleases/pressreleases/planetarydashboardshowsgreataccelerationinhumanactivitysince1950.5.950c2fa1495db7081eb42.html#:%7E:text=We%20can%20say%20that%20around,to%20the%20global%20economic%20system.">Great Acceleration</a>.</p>
<p>The disagreement speaks to something vital to science – the ability to accommodate dissent through debate. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/537958/original/file-20230718-19-afp9e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="lake crawford" src="https://images.theconversation.com/files/537958/original/file-20230718-19-afp9e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537958/original/file-20230718-19-afp9e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537958/original/file-20230718-19-afp9e7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537958/original/file-20230718-19-afp9e7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537958/original/file-20230718-19-afp9e7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537958/original/file-20230718-19-afp9e7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537958/original/file-20230718-19-afp9e7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Canada’s Lake Crawford was chosen because it’s a rare meromictic lake, meaning different layers of water don’t intermix. That, in turn, makes it better at laying down sediment.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>What’s the debate about?</h2>
<p>Would the public embrace the idea that our actions are making the world almost wholly unnatural? The answer, of course, depends on the quality of the science. Since most people aren’t scientists, we rely on the scientific community to hash out debate and present the best explanations for the data.</p>
<p>That’s why Ellis’s departure is so interesting. His resignation letter is explosive: </p>
<blockquote>
<p>It’s […] [im]possible to avoid the reality that narrowly defining the Anthropocene […] has become more than a scholarly concern. The AWG’s choice to systematically ignore overwhelming evidence of Earth’s long-term anthropogenic transformation is not just bad science, it’s bad for public understanding and action on global change. </p>
</blockquote>
<p>It’s not that Ellis thinks the way we live is problem-free. The central issue, in his view, is that there’s powerful evidence of much earlier global-scale impacts caused by pre- and proto-capitalist societies. </p>
<p>For instance, as Earth systems experts Simon Lewis and Mark Maslin <a href="https://theconversation.com/why-the-anthropocene-began-with-european-colonisation-mass-slavery-and-the-great-dying-of-the-16th-century-140661">have shown</a>, the violent Portuguese and Spanish colonisation of Central and South America indirectly lowered atmospheric carbon dioxide levels. How? By killing millions of indigenous people and destroying local empires. With the people gone, the trees regrew during the 17th century and covered the <a href="https://www.discovermagazine.com/planet-earth/lost-society-found-in-amazon-rainforest">villages and cities</a>, expanding the Amazon rainforest. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/537963/original/file-20230718-17-5eworn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/537963/original/file-20230718-17-5eworn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537963/original/file-20230718-17-5eworn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537963/original/file-20230718-17-5eworn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537963/original/file-20230718-17-5eworn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537963/original/file-20230718-17-5eworn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537963/original/file-20230718-17-5eworn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537963/original/file-20230718-17-5eworn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Villages and towns dotted many parts of the Amazon before colonisation. This image shows what’s left of a village.</span>
<span class="attribution"><span class="source">University of Exeter</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Why we should welcome honest disagreement in science</h2>
<p>Scientists have been debating in recent years over whether the Anthropocene should be deemed an “epoch” with a specific start date, or else an historically extended “event” caused by different human practices in different places, such as early agriculture, European colonisation and the spread of European and North American capitalism worldwide. </p>
<p>Ellis’ resignation stems from this debate. He’s not alone – other group members and experts have also <a href="https://onlinelibrary.wiley.com/doi/10.1002/jqs.3416">worked to refute</a> the epoch idea. </p>
<p>As philosopher of science Karl Popper and others have argued, productive scientific debate can only occur if there’s space for dissent and alternative perspectives. Ellis clearly believes the Anthropocene group has gone from debate to group think, which, if true, would challenge the free exchange at the heart of science. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-canadian-lake-holds-the-key-to-the-beginning-of-the-anthropocene-a-new-geological-epoch-209576">A Canadian lake holds the key to the beginning of the Anthropocene, a new geological epoch</a>
</strong>
</em>
</p>
<hr>
<p>Longer term, a compromise may well be reached. If the Anthropocene group were to shift tack and label the start of the epoch a multi-century event (a “long Anthropocene”), we’d still benefit from having labels for periods such as our current one where the human impact ramped-up significantly. </p>
<p>One issue with such tensions is what happens when they hit the media. Consider Climategate, the 2009 incident in which an attacker stole emails from a key climate research centre in the United Kingdom. Bad faith actors seized on perceived issues in the emails and <a href="https://www.theguardian.com/theobserver/2019/nov/09/climategate-10-years-on-what-lessons-have-we-learned">used them</a> to claim anthropogenic climate change was fabricated. The scientists at the heart of the controversy were cleared of wrongdoing, but the whole affair helped seed doubt and slow our transition away from fossil fuels. </p>
<p>The risk here is that if the public gets only a glancing, oversimplified view of these debates, they may come to doubt the abundant proof of our impact on Earth. It falls to journalists and science communicators to convey this accurately. </p>
<p>As for our trust in science, the case for declaring the Anthropocene will be subject to very close scrutiny and may not be ratified by the International Commission on Stratigraphy, the <a href="https://stratigraphy.org/">body responsible</a> for separating out <a href="https://theconversation.com/all-things-will-outlast-us-how-the-indigenous-concept-of-deep-time-helps-us-understand-environmental-destruction-132201">deep time</a> into specific epochs. </p>
<p>Stratigraphers such as Lucy Edwards <a href="https://rock.geosociety.org/net/gsatoday/archive/26/3/abstract/i1052-5173-26-3-4.htm">have argued</a> that an emerging epoch isn’t a fit subject for stratigraphy at all because all the evidence cannot, by definition, be in. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/537959/original/file-20230718-23-3qk1b4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="hutton unconformit" src="https://images.theconversation.com/files/537959/original/file-20230718-23-3qk1b4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537959/original/file-20230718-23-3qk1b4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537959/original/file-20230718-23-3qk1b4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537959/original/file-20230718-23-3qk1b4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537959/original/file-20230718-23-3qk1b4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=496&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537959/original/file-20230718-23-3qk1b4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=496&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537959/original/file-20230718-23-3qk1b4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=496&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This unassuming rock formation in Scotland is the site of a famous geological discovery, where James Hutton first realised the boundary between two types of rock separated geological epochs.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>What does this tension mean for the Anthropocene?</h2>
<p>The epoch versus event debate doesn’t mean we’re off the hook in terms of our impact on the planet. It is abundantly clear we have become the first species in Earth’s long history to alter the functioning of the atmosphere, cryosphere, hydrosphere, biosphere and pedosphere (the soil layer) all at once and very quickly. Species such as cyanobacteria or blue-green algae had <a href="https://asm.org/Articles/2022/February/The-Great-Oxidation-Event-How-Cyanobacteria-Change">huge impact</a> by adding oxygen to the atmosphere, but they did not affect all spheres with the speed and severity we have.</p>
<p>While we did not set out to alter the planet, its implications are profound. Humans are not only altering the climate but the entirety of the irreplaceable envelope sustaining life on the only planet known to have life. This is a complex story and we should not expect science to simplify it for political or other reasons.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-the-anthropocene-began-with-european-colonisation-mass-slavery-and-the-great-dying-of-the-16th-century-140661">Why the Anthropocene began with European colonisation, mass slavery and the 'great dying' of the 16th century</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/209869/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Noel Castree 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>Our activities now affect the entire planet. But there’s a vital debate over when we started disrupting these systems. Was it 1950 – or hundreds and thousands of years earlier?Noel Castree, Professor of Society & Environment, University of Technology SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2098622023-07-18T03:57:15Z2023-07-18T03:57:15ZA climate expert explains the Northern Hemisphere’s weird, wild summer – and what it means for Australia<p>The Northern Hemisphere summer has brought one extreme event after another – from heatwaves to wildfires and floods. It comes as the world likely heads into an El Niño pattern, which brings a higher chance of hot, dry weather in much of Australia.</p>
<p>So is the weird northern summer a portent of what Australia can expect in a few months?</p>
<p>The extremes in the Northern Hemisphere are linked to persistent weather patterns which allow heat to build in some places and rain to continue in others. On top of this, human-caused climate change is raising temperatures to new heights.</p>
<p>It’s too early to say whether Australia is in for a scorching summer. The predicted El Niño is a worry, but doesn’t guarantee the record-smashing heat we’re seeing in parts of the Northern Hemisphere.</p>
<p>Having said that, continued global warming will bring more record-high temperatures in Australia. So we must remain on high-alert – and ramp up reductions in greenhouse gas emissions.</p>
<h2>Extreme weather across the world</h2>
<p>Wild weather in the Northern Hemisphere at this time of year is to be expected. However, recent extremes are off the charts.</p>
<p>Major heatwaves are underway in North America, Europe, North Africa and Asia. In California’s Death Valley, temperatures on Sunday <a href="https://www.9news.com.au/world/californias-death-valley-sizzles-as-brutal-heat-wave-continues/f1f90160-9b55-434f-8b07-76107c4b6a23">reached 53.3°C</a>. Parts of Italy were <a href="https://www.theguardian.com/world/2023/jul/17/extreme-temperatures-recorded-across-northern-hemisphere">expected</a> to reach 45°C on Tuesday, and later in the week could approach Europe’s hottest temperature on record: 48.8°C. </p>
<p>China provisionally reached 52.2°C on Sunday, shattering the previous record for the country by more than 1.5°C.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1680925410723262466"}"></div></p>
<p>Meanwhile, wildfires are tearing through <a href="https://www.cbsnews.com/news/map-canadian-wildfires-2023-where-are-the-fires-ontario-quebec/">Canada</a>, <a href="https://www.bbc.com/news/world-europe-66226500">Greece</a> and <a href="https://www.9news.com.au/world/la-palma-fire-bushfire-on-la-palma-spain-canary-islands-out-of-control-as-2000-evacuated/ba346a55-a0ac-4b2c-94db-8c5bfa76b1aa">Spain</a>, destroying properties and forcing evacuations.</p>
<p>So what’s causing these simultaneous heatwaves across multiple regions? They’re all linked to high-pressure weather systems that are “blocking” or <a href="https://www.carbonbrief.org/jet-stream-is-climate-change-causing-more-blocking-weather-events/">deflecting</a> oncoming low-pressure systems (and associated clouds and rain). </p>
<p>These low-pressure systems have moved to other areas and caused extreme rainfall and flooding. Flooding in South Korea has <a href="https://www.abc.net.au/news/2023-07-17/south-korea-floods-rain-death-toll-underpass-rescue/102609930">left 40 people dead</a> and destroyed critical infrastructure. Vermont, in the northeast United States, was also flooded after up to <a href="https://www.bbc.com/news/world-us-canada-66154757">two months of rain</a> fell in a few days.</p>
<p>Alarmingly, the atmospheric patterns driving the extremes in the Northern Hemisphere appear to be getting <a href="https://www.nature.com/articles/s41467-022-31432-y">more common</a> under climate change. On top of this, human-caused global warming is greatly increasing the chance of <a href="https://www.nature.com/articles/s41558-021-01092-9">record-breaking</a> extreme heat events and <a href="https://journals.ametsoc.org/view/journals/clim/35/3/JCLI-D-21-0200.1.xml">concurrent heatwaves</a> across many regions. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-are-so-many-climate-records-breaking-all-at-once-209214">Why are so many climate records breaking all at once?</a>
</strong>
</em>
</p>
<hr>
<h2>What this means for Australia</h2>
<p>All this begs the question of what might be coming Australia’s way this summer. </p>
<p>There’s one factor working in our favour: the particular atmospheric pattern bringing extremes to the Northern Hemisphere isn’t replicated in the Southern Hemisphere, because we have more ocean and less land. </p>
<p>However, Australia does experience its own “blocking” high pressure patterns which also bring <a href="https://theconversation.com/the-stubborn-high-pressure-system-behind-australias-record-heatwaves-110442">major heatwaves</a> and <a href="https://theconversation.com/heres-why-climate-change-isnt-always-to-blame-for-extreme-rainfall-206958">extreme rain events</a>. Unfortunately we can’t predict these months in advance. </p>
<p>El Niño is a little more easily predicted. Currently, the tropical Pacific Ocean is trending towards El Niño conditions, as waters off the west coast of Ecuador and Peru continue to warm. </p>
<p>El Niño is part of a natural fluctuation in the Earth’s climate system which typically lasts for the best part of a year. It raises the chance of a warmer and drier spring in Australia.</p>
<p>Some meteorological agencies <a href="https://public.wmo.int/en/media/press-release/world-meteorological-organization-declares-onset-of-el-ni%C3%B1o-conditions">say</a> an El Niño has already arrived. Australia’s Bureau of Meteorology is holding off on a declaration, for now. That’s because while the Pacific has fallen into an El Niño pattern, the atmosphere <a href="http://www.bom.gov.au/climate/enso/">hasn’t yet followed</a>. </p>
<p>But the bureau still puts the likelihood of an El Niño at 70%, and <a href="http://www.bom.gov.au/climate/outlooks/#/overview/summary/">forecasts</a> warmer and drier conditions across much of Australia from August to November.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/537674/original/file-20230717-20840-dx61m2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/537674/original/file-20230717-20840-dx61m2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537674/original/file-20230717-20840-dx61m2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537674/original/file-20230717-20840-dx61m2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537674/original/file-20230717-20840-dx61m2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537674/original/file-20230717-20840-dx61m2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537674/original/file-20230717-20840-dx61m2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537674/original/file-20230717-20840-dx61m2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Spring is predicted to be warmer than average across the continent.</span>
<span class="attribution"><span class="source">Bureau of Meteorology</span></span>
</figcaption>
</figure>
<p>The extreme weather in the Northern Hemisphere isn’t strongly related to the developing El Niño. But by the time Australia’s summer arrives, we’ll likely see El Niño’s effects in the weather. </p>
<p>What’s more, another driver of Australia’s climate, the <a href="http://www.bom.gov.au/climate/iod/">Indian Ocean Dipole</a>, is likely to enter a positive phase in coming months. </p>
<p>This phase is associated with warmer seas in the west Indian Ocean. This leads to fewer low pressure systems, on average, over southeast Australia and less atmospheric moisture over most of the continent. This would likely suppress winter and spring rainfall over much of Australia and exacerbate an El Niño’s drying effect.</p>
<p>Not all El Niño and positive Indian Ocean Dipole events bring <a href="https://climateextremes.org.au/what-is-el-ninos-impact-on-australias-weather-and-climate/">warm, dry weather</a>. And there <a href="https://www.publish.csiro.au/es/pdf/ES17004">isn’t a strong relationship</a> between the magnitude of an El Niño and the lack of rain in Australia. But these background climate conditions raise the chance of a warmer and drier spring.</p>
<p>We can’t yet predict if Australia will swelter this summer. But an El Niño increases the chance of hotter and drier summer conditions, with more heatwaves and a greater frequency of <a href="https://www.nature.com/articles/s43247-020-00065-8">weather conducive to fire spread</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/537675/original/file-20230717-218013-93bviy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/537675/original/file-20230717-218013-93bviy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537675/original/file-20230717-218013-93bviy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537675/original/file-20230717-218013-93bviy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537675/original/file-20230717-218013-93bviy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537675/original/file-20230717-218013-93bviy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537675/original/file-20230717-218013-93bviy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537675/original/file-20230717-218013-93bviy.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Australia’s spring is likely to be drier than average, especially across the east and south.</span>
<span class="attribution"><span class="source">Bureau of Meteorology</span></span>
</figcaption>
</figure>
<h2>Australia in a warming world</h2>
<p>Of course, all this comes on top of human-driven global warming. In Australia, land areas have already warmed by <a href="https://www.ipcc.ch/report/ar6/wg1/downloads/factsheets/IPCC_AR6_WGI_Regional_Fact_Sheet_Australasia.pdf">1.4°C over the past century</a>, and the cool summers common before 1980 are now far less likely.</p>
<p>In fact, even if global warming is limited to well below 2°C, historically hot summers in Australia <a href="https://www.nature.com/articles/nclimate3296">will become common</a>.</p>
<p>The Northern Hemisphere’s current extreme weather, and predictions of hotter summers in Australia, are all evidence of humanity’s fingerprints on Earth’s climate. This should spur urgent action to reduce greenhouse gas emissions.</p>
<p>Because if global warming continues, Australia is certain to be hit by more record-breaking heat events – and that is <a href="https://theconversation.com/theres-no-end-to-the-damage-humans-can-wreak-on-the-climate-this-is-how-bad-its-likely-to-get-166031">not</a> something we want to experience. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/heres-why-climate-change-isnt-always-to-blame-for-extreme-rainfall-206958">Here's why climate change isn't always to blame for extreme rainfall</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/209862/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew King receives funding from the National Environmental Science Program. </span></em></p>The predicted El Niño is a worry, but it doesn’t guarantee the record-breaking heat we’re seeing in parts of the Northern Hemisphere.Andrew King, Senior Lecturer in Climate Science, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2009662023-04-17T16:09:39Z2023-04-17T16:09:39ZHow soils changed life on Earth<p>For the first 4 billion years of Earth’s existence, its continents were dusty, barren and rocky landscapes similar to the surface of Mars. But, around 500 million years ago, this all changed. </p>
<hr>
<iframe id="noa-web-audio-player" style="border: none" src="https://embed-player.newsoveraudio.com/v4?key=x84olp&id=https://theconversation.com/how-soils-changed-life-on-earth-200966 &bgColor=F5F5F5&color=D8352A&playColor=D8352A" width="100%" height="110px"></iframe>
<p><em>You can listen to more articles from The Conversation, narrated by Noa, <a href="https://theconversation.com/us/topics/audio-narrated-99682">here</a>.</em></p>
<hr>
<p>Land plants began to evolve from their freshwater algal ancestors and gradually covered the planet’s rocky surface. Originally just a few centimetres tall, the first land plants quickly evolved into more complex forms. By 385 million years ago, extensive forests covered the planet’s surface. </p>
<p>This new plant diversity was underpinned by a transition that occurred below the ground – the formation of roots and soils. Soils are so abundant today that we often take them for granted or assume they are a constant feature of our planet. But this is not the case. Deep soils as we know them have existed for <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/pala.12185">less than 10% of our planet’s history</a>. </p>
<p>The formation of these soils dramatically changed life on Earth. Soils altered terrestrial landscapes, water courses, nutrient and mineral cycling and even the composition of the atmosphere. The role soil played in making Earth habitable highlights the importance of protecting our soils today.</p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?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><em>Many people think of plants as nice-looking greens. Essential for clean air, yes, but simple organisms. A step change in research is shaking up the way scientists think about plants: they are far more complex and more like us than you might imagine. This blossoming field of science is too delightful to do it justice in one or two stories.</em> </p>
<p><em><a href="https://theconversation.com/topics/plant-curious-137238?utm_source=TCUK&utm_medium=linkback&utm_campaign=PlantCurious2023&utm_content=InArticleTop">This article is part of a series, Plant Curious</a>, exploring scientific studies that challenge the way you view plantlife.</em></p>
<hr>
<h2>The first soils</h2>
<p>The earliest evidence for how soils evolved comes from ancient land plant fossils. A rock formation in the northeast of Scotland, called the <a href="https://pubs.geoscienceworld.org/geolmag/article-abstract/157/1/47/581268/An-introduction-to-the-Rhynie-chertIntroduction-to">Rhynie Chert</a>, contains exceptionally well preserved 407 million-year-old plant fossils. This allows scientists to <a href="https://royalsocietypublishing.org/toc/rstb/2018/373/1739">study the diversity of life</a> that thrived here. </p>
<p>The majority of the plants preserved in the Rhynie chert lack the large complex roots typical of plants you may be familiar with today. Their rooting systems were instead composed of <a href="https://royalsocietypublishing.org/doi/10.1098/rstb.2017.0042">thin stems that were covered by hairs called rhizoids</a>. These hairs helped anchor plants to the planet’s rocky surface and absorb water and nutrients. </p>
<figure class="align-center ">
<img alt="Artists reconstruction of rhizoid-based rooting systems from the Rhynie chert." src="https://images.theconversation.com/files/516630/original/file-20230321-24-8ozpwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/516630/original/file-20230321-24-8ozpwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=478&fit=crop&dpr=1 600w, https://images.theconversation.com/files/516630/original/file-20230321-24-8ozpwe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=478&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/516630/original/file-20230321-24-8ozpwe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=478&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/516630/original/file-20230321-24-8ozpwe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=600&fit=crop&dpr=1 754w, https://images.theconversation.com/files/516630/original/file-20230321-24-8ozpwe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=600&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/516630/original/file-20230321-24-8ozpwe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=600&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artists reconstruction of rhizoid-based rooting systems from the Rhynie chert, Aberdeenshire.</span>
<span class="attribution"><a class="source" href="https://royalsocietypublishing.org/doi/10.1098/rstb.2017.0042">Rosemary Wise/Royal Society Publishing</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>New hairy stems grew and intertwined with the mass of decaying older stems to gradually build up a thin peaty soil just a few centimetres thick. Despite its thinness, this soil could resist being blown or washed away, so provided a foothold for more plants to grow. </p>
<p>Early soils, like those preserved in the Rhynie chert, supported a diverse range of fungi. Some formed beneficial relationships with plants, helping them mine for nutrients in exchange for carbon provided by the plants – others fed on decaying plant tissue. </p>
<p>These soils also formed a hunting ground for <a href="https://www.britannica.com/animal/mite">mites</a>, <a href="https://www.britannica.com/animal/nematode">nematodes (roundworms)</a> and early arachnids. The plants, animals and fungi together formed a complex food web. </p>
<p>This thin soil was already teaming with life.</p>
<h2>Diversity of plants</h2>
<p>Skip forward 20 million years and Earth’s continents are covered by forests with <a href="https://www.sciencedirect.com/science/article/pii/S0960982219315696">soils over a metre deep</a>. This remarkable increase in soil depth, in what is considered a short space of geological time, was fuelled by the evolution of plant roots. Roots increase soil depth by growing downwards and adding organic matter deeper into the sediment.</p>
<p>Roots are specialised organs that enable plants to anchor and mine for water and nutrients. They are specially adapted for life below the ground and for pushing their way down into the rocky substrate below Earth’s surface.</p>
<p>The move from hairy stems clinging to the top of the rocky substrate to roots that drilled down over a metre in depth, transformed soils and allowed plants to access deep reserves of water and nutrients. This below-ground revolution provided an entirely new ecosystem for life to diversify into. </p>
<figure class="align-center ">
<img alt="Exposed modern tree roots." src="https://images.theconversation.com/files/516636/original/file-20230321-1234-v5a9sw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/516636/original/file-20230321-1234-v5a9sw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/516636/original/file-20230321-1234-v5a9sw.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/516636/original/file-20230321-1234-v5a9sw.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/516636/original/file-20230321-1234-v5a9sw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/516636/original/file-20230321-1234-v5a9sw.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/516636/original/file-20230321-1234-v5a9sw.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">Exposed modern tree roots, Sutherland, Scotland.</span>
<span class="attribution"><span class="source">Sandy Hetherington</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Soils changed more than what’s under our feet</h2>
<p>Soils are the key interface between geology, the atmosphere and the water and nutrient cycles. The advent of deep soils transformed the interaction between these parts of the Earth and brought about a number of surprising changes.</p>
<p>One change was to the water cycle. What was once a landscape covered in a large number of small crisscrossing streams was transformed into floodplains with large <a href="https://www.nature.com/articles/ngeo1376">meandering river channels</a>. At the same time, soils were storing water that could sustain more plant life and be cycled quickly back into the atmosphere.</p>
<p>The period in which soils were expanding in depth and extent was also accompanied by an <a href="https://www.sciencedirect.com/science/article/pii/S0012825217304117">enormous drop in atmospheric CO₂ levels</a> and cooling global temperatures. This change to the composition of the atmosphere was partly due to two features of roots and soils. </p>
<p>Plant roots helped to increase the weathering of rocks by physically and chemically breaking down bedrock – a process that results in a <a href="https://www.pnas.org/doi/full/10.1073/pnas.0408724102">net drawdown of CO₂ from the atmosphere</a>. </p>
<p>Soils, especially organic rich peat soils, are also huge carbon reservoirs. Plants require CO₂ to grow and when plants decay, CO₂ is released back to the atmosphere. But this plant material does not fully decay in many soils and much of it is gradually buried. </p>
<p>This locks carbon in peaty soils, which if buried, can form coal. The origin of deep soils and forests <a href="https://www.pnas.org/doi/10.1073/pnas.1517943113#:%7E:text=Rather%20than%20a%20consequence%20of,during%20the%20assembly%20of%20Pangea.">greatly increased carbon burial rates</a> on Earth.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/516640/original/file-20230321-28-n6814o.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An example of modern peaty soil." src="https://images.theconversation.com/files/516640/original/file-20230321-28-n6814o.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/516640/original/file-20230321-28-n6814o.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/516640/original/file-20230321-28-n6814o.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/516640/original/file-20230321-28-n6814o.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/516640/original/file-20230321-28-n6814o.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/516640/original/file-20230321-28-n6814o.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/516640/original/file-20230321-28-n6814o.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">Modern peaty soil, Isle of Skye, Scotland.</span>
<span class="attribution"><span class="source">Sandy Hetherington</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Soil underpins a huge amount of life on Earth. Its role in the water cycle, nutrient cycle and critically as a reserve of carbon remain key today and in the future. The fossil record serves as a reminder that we must <a href="https://theconversation.com/soil-is-our-best-ally-in-the-fight-against-climate-change-but-were-fast-running-out-of-it-128166">protect our soils</a>.</p><img src="https://counter.theconversation.com/content/200966/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sandy Hetherington works for The University of Edinburgh, and his research is currently funded by a UKRI Future Leaders Fellowship.</span></em></p>What fossil records tell us about when the Earth was first covered by plants.Sandy Hetherington, Plant Evolutionary Biologist, The University of EdinburghLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1984042023-02-24T00:45:54Z2023-02-24T00:45:54ZCurious Kids: where does wind actually come from?<figure><img src="https://images.theconversation.com/files/507272/original/file-20230131-16-wacbvj.jpg?ixlib=rb-1.1.0&rect=66%2C26%2C4218%2C2932&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/YNM4KStg78I">Saad Chaudhry/Unsplash</a></span></figcaption></figure><blockquote>
<p>Where does wind come from? – Zoya, age 14, Bhopal, India</p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>The short answer is wind happens because the Sun heats some parts of the planet more than others, and this uneven heating starts a wind going. That means wind energy is really a kind of solar energy!</p>
<h2>All winds are made the same way</h2>
<p><a href="https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjH3IOSyd_8AhU-zqACHcjqDE0QFnoECAsQAQ&url=https%3A%2F%2Fwww.nature.com%2Fscitable%2Fknowledge%2Flibrary%2Fwhere-do-winds-come-from-100578316%2F&usg=AOvVaw0K54CQ7PpdSsYr5Izp8obD">Wind systems on Earth</a> vary from the global-scale trade winds and jet streams to local sea breezes, but they all ultimately depend on Earth being unevenly heated by the Sun.</p>
<p>When the ground is heated during the day and gets very hot, it heats the air above it by a process called heat conduction. This makes the air expand to occupy a larger volume. According to something called the “<a href="https://www.britannica.com/science/ideal-gas-law">ideal gas law</a>”, the volume increases in direct proportion to the temperature.</p>
<p>In other words, the heated air is less dense. If this happens to all air, no wind will be created; the whole air layer will just be a bit thicker.</p>
<p>However, if it happens to air in one location but not its surroundings, the heated air will rise. This is the principle that allows hot air balloons to remain buoyant in the air: the total weight of the air in the balloon, plus the basket and people inside, must be about the same as the weight of the same volume of colder air outside the balloon.</p>
<p>If there is no load or tether, the balloon will just keep accelerating upward until it cools off.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507274/original/file-20230131-18-yczmof.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A rocky desert scene with several colourful hot air balloons in the sky" src="https://images.theconversation.com/files/507274/original/file-20230131-18-yczmof.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507274/original/file-20230131-18-yczmof.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507274/original/file-20230131-18-yczmof.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507274/original/file-20230131-18-yczmof.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507274/original/file-20230131-18-yczmof.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507274/original/file-20230131-18-yczmof.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507274/original/file-20230131-18-yczmof.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">Hot air balloons use the principle of the air changing density as it heats up and cools down.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/vCArUMDcHCQ">Timur Garifov/Unsplash</a></span>
</figcaption>
</figure>
<p>A rising hot air balloon doesn’t create any wind because it’s too small. But imagine if the same thing happens to all the air over a whole city or larger region!</p>
<p>When such a large amount of heated air rises away from the surface, other air near the ground has to flow in sideways to take its place. The larger the area over which this happens, the stronger the horizontal wind needs to be to get all that air into position.</p>
<p>This phenomenon gives us daytime sea breezes near coasts that can be fairly strong, where cooler ocean air flows in to replace the warmed continental air as it rises up. </p>
<p>Over many days, a similar process gives us monsoons, because the heating is stronger in summer and weaker in winter, leading to strong temperature contrasts and winds in summer (and often, opposite ones in winter).</p>
<p>In turn, this leads to seasonal shifts in the prevailing wind, which often bring rains during the warm season in tropical areas including India and the top end of Australia.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-the-australian-monsoon-69411">Explainer: what is the Australian monsoon?</a>
</strong>
</em>
</p>
<hr>
<h2>There are some very big wind systems</h2>
<p>The biggest wind systems on the planet are called the <a href="https://en.wikipedia.org/wiki/Atmospheric_circulation">general circulation of the atmosphere</a>. They include the <a href="http://www.bom.gov.au/climate/about/?bookmark=trades#:%7E:text=tropical%20Ridge%20ENSO-,What%20are%20they%3F,global%20circulation%20of%20the%20atmosphere.">trade winds or easterlies</a>, the middle-latitude <a href="https://www.climate-policy-watcher.org/global-climate-2/winds-westerlies.html">westerlies</a> and the <a href="https://oceanservice.noaa.gov/facts/roaring-forties.html">Roaring Forties</a>. </p>
<p>These large wind systems happen because the tropics get more Sun than the poles and (obviously) become a lot warmer. That warm air naturally starts to rise and wants to flow toward the poles, while polar air wants to come down to the tropics.</p>
<p>Of course, it takes a long time (many days) for the air to make such a long trip. Meanwhile Earth is constantly rotating, which means <a href="https://www.schooltube.com/media/Merry+Go+Round+and+the+Coriolis+Effect/1_uo3uoomf/129088791">things trying to move in a straight line will seem to gradually turn</a>.</p>
<p>The poleward-flowing wind gradually turns toward the east and becomes the middle-latitude westerlies (westerly means “from the west”). </p>
<p>The low-level wind heading toward the tropics turns toward the west and becomes the easterlies, also known as trade winds because ship captains have used these to cross the oceans for centuries. The middle-latitude westerlies are very strong at high altitude, approaching 300km per hour in some places!</p>
<p>You can see a great interactive visualisation <a href="https://earth.nullschool.net/#current/wind/isobaric/250hPa/orthographic=-195.00,0.00,472">of all the winds on the planet here</a>.</p><img src="https://counter.theconversation.com/content/198404/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Steven Sherwood receives funding from the Australian Research Council. </span></em></p>It can be disruptive or refreshing, and we feel it every single day. But do you ever stop to think what creates wind on our planet?Steven Sherwood, Professor of Atmospheric Sciences, Climate Change Research Centre, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1981052023-01-26T16:02:34Z2023-01-26T16:02:34ZFour possible consequences of El Niño returning in 2023<figure><img src="https://images.theconversation.com/files/506579/original/file-20230126-20-pu1ru1.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3872%2C2590&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Dry conditions are likely to resume in northeastern Brazil.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/livestock-cattle-being-driven-by-dirt-2143454947">Cacio Murilo/Shutterstock</a></span></figcaption></figure><p>Every two to seven years, the equatorial Pacific Ocean gets up to 3°C warmer (what we know as an El Niño event) or colder (La Niña) than usual, triggering a cascade of effects felt around the world. This cycle is called the El Niño Southern Oscillation (ENSO) because every El Niño is naturally followed by a La Niña and vice versa, with some months of neutral conditions in between events. The change in sea surface temperature associated with ENSO events might seem marginal, but it is more than enough to disrupt weather patterns globally and even the large-scale circulation of air in the polar stratosphere 8km above the Earth.</p>
<p>It is not surprising for La Niña conditions to last two consecutive years, but a three-year La Niña, which the world has had since 2020, is more rare. The US National Oceanic and Atmospheric Administration (NOAA) has <a href="https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf">reported</a> that the equatorial Pacific Ocean will return to its neutral state between March and May of 2023, and it is likely that El Niño conditions will develop during the northern hemisphere’s autumn and winter.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/506382/original/file-20230125-18-cfktl7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A bar chart depicting a shift from La Niña to El Niño over the course of 2023." src="https://images.theconversation.com/files/506382/original/file-20230125-18-cfktl7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/506382/original/file-20230125-18-cfktl7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/506382/original/file-20230125-18-cfktl7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/506382/original/file-20230125-18-cfktl7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/506382/original/file-20230125-18-cfktl7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=479&fit=crop&dpr=1 754w, https://images.theconversation.com/files/506382/original/file-20230125-18-cfktl7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=479&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/506382/original/file-20230125-18-cfktl7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=479&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Probability of El Niño (red), La Niña (blue) or ENSO-neutral conditions developing during the coming months.</span>
<span class="attribution"><a class="source" href="https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf">Climate Prediction Center/NOAA</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Given the strong influence of ENSO on global patterns of precipitation and temperature, scientists keep a close watch on the status of the tropical Pacific to provide the best possible information. So what can the world expect from the next El Niño event?</p>
<h2>1. Likelihood of exceeding 1.5°C</h2>
<p>During an El Niño, the ocean transfers some of that excess heat and moisture to the atmosphere, as when you cook pasta and your kitchen gets steamy. On top of the global warming trend, a strong El Niño can add up to 0.2°C to the average temperature of the Earth. The hottest year on record was 2016, during a particularly strong El Niño. A La Niña year can also break heat records, as the warming trend imposed by the increasing accumulation of greenhouse gases in the atmosphere can mask the cooling effect of natural processes.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/506530/original/file-20230126-11748-v3hf40.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A series of bar charts depicting annual average surface temperatures, grouped by decade, from 1950 to 2021. The warmest and coldest years of each decade are topped with circles: red for El Niño-influenced years and blue for La Niña years." src="https://images.theconversation.com/files/506530/original/file-20230126-11748-v3hf40.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/506530/original/file-20230126-11748-v3hf40.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/506530/original/file-20230126-11748-v3hf40.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/506530/original/file-20230126-11748-v3hf40.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/506530/original/file-20230126-11748-v3hf40.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/506530/original/file-20230126-11748-v3hf40.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/506530/original/file-20230126-11748-v3hf40.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">As the world has warmed, the hottest years have occurred during El Niño events.</span>
<span class="attribution"><span class="source">NOAA Climate/NOAA National Centers for Environmental Information</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Since the planet has already warmed by around 1.2°C relative to pre-industrial times and El Niño adds some extra heat to the atmosphere, it’s possible that Earth’s rising temperature will temporarily exceed the <a href="https://theconversation.com/after-cop27-all-signs-point-to-world-blowing-past-the-1-5-degrees-global-warming-limit-heres-what-we-can-still-do-about-it-195080">1.5°C threshold</a> of the Paris agreement some time after the peak of the El Niño in 2024, though it is too early to know how strong this next event will be.</p>
<h2>2. More heat, drought and fires in Australia</h2>
<p>Australia has had three years of above average rainfall due to prolonged La Niña conditions that brought severe floods, especially in the east. During El Niño, scientists expect the opposite: less rain, higher temperatures and increased fire risk, especially during winter and spring in the southern hemisphere.</p>
<p>As the globe heats up, some regions are warming faster than others. A good example is <a href="https://www.nature.com/articles/s41467-021-27225-4">Australia</a>, which is 1.4°C hotter now than in the early 20th century. Every year, the area of the continent scorched by wildfires increases, fuelled by a dry trend induced by climate change. This occurs despite the anomalous wet years that Australia has experienced during the recent La Niña event. The underlying influence of climate change makes the country extremely vulnerable to the effects of an El Niño.</p>
<figure class="align-center ">
<img alt="The undergrowth burns in an Australian eucalypt forest." src="https://images.theconversation.com/files/506575/original/file-20230126-24-p45etq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/506575/original/file-20230126-24-p45etq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/506575/original/file-20230126-24-p45etq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/506575/original/file-20230126-24-p45etq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/506575/original/file-20230126-24-p45etq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/506575/original/file-20230126-24-p45etq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/506575/original/file-20230126-24-p45etq.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">Heatwaves and wildfires could become more frequent and severe in 2023.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/fire-undergrowth-eucalypt-forest-flames-dense-750956152">Metriognome/Shutterstock</a></span>
</figcaption>
</figure>
<h2>3. Slower carbon uptake in South America</h2>
<p>South America is where the effects of ENSO were first documented by Peruvian fishermen centuries ago. Given the proximity to the equatorial Pacific Ocean, South American weather is significantly disrupted every time an El Niño event occurs, with flooding on the west coasts of Peru and Ecuador and drought in the Amazon and northeast, where the consequences of crop failures can reverberate across the continent.</p>
<p>During El Niño events, the fall in precipitation and rise in temperature in Colombia has been linked to outbreaks of diseases spread by insects, such as <a href="http://users.clas.ufl.edu/prwaylen/Geo3280articles/Poveda.pdf">malaria and dengue fever</a>. Higher temperatures during El Niño boost the rates at which mosquitoes breed and bite.</p>
<p>Elsewhere during an El Niño, the Amazon rainforest dries and vegetation growth slows so that less CO₂ is absorbed from the atmosphere, a trend <a href="https://journals.ametsoc.org/view/journals/clim/14/21/1520-0442_2001_014_4113_tccrte_2.0.co_2.xml">repeated</a> in the tropical forests of Africa, India and Australia.</p>
<figure class="align-center ">
<img alt="A scientist inspecting a tree in a tropical forest." src="https://images.theconversation.com/files/506532/original/file-20230126-14416-41uyq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/506532/original/file-20230126-14416-41uyq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/506532/original/file-20230126-14416-41uyq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/506532/original/file-20230126-14416-41uyq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/506532/original/file-20230126-14416-41uyq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/506532/original/file-20230126-14416-41uyq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/506532/original/file-20230126-14416-41uyq.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">Scientists in 2019 studying the damage from Amazon forest fires that burned during the 2015/16 El Niño.</span>
<span class="attribution"><span class="source">Marizilda Cruppe/Rede Amazônia Sustentável</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>4. Cold winters in northern Europe</h2>
<p>The balance between high pressure over the Azores and low pressure over Iceland determines where rain goes in Europe during winter by pushing the jet stream – a band of strong eastward winds that carries rain across the Atlantic – north or south. During El Niño winters, both pressure centres lose strength, and the jet stream brings wetter conditions to southern Europe. </p>
<p>The largest effect is observed in northern Europe, however, where winters become drier and colder. A frosty 2023-24 winter season is likely if El Niño ramps up sufficiently by then. As a result of global warming, scientists expect El Niño’s influence over the North Atlantic and northern European winter will <a href="https://www.frontiersin.org/articles/10.3389/fclim.2022.941055/full">strengthen</a>.</p>
<p>Understanding the intricacies of the climate system is similar to trying to assemble a <a href="https://www.jstor.org/stable/1691792#metadata_info_tab_contents">big jigsaw puzzle</a>. The oceans talk to each other, and to the atmosphere, which at the same time feeds back to the ocean. Scientists are still unsure how El Niño will behave in the future, but its effects will probably be amplified by climate change in different regions of the world.</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>
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<hr><img src="https://counter.theconversation.com/content/198105/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paloma Trascasa-Castro receives funding from the Natural Environment Research Council (NERC).</span></em></p>From bushfires in Australia to insect-borne disease outbreaks in Colombia.Paloma Trascasa-Castro, PhD Candidate in Climate Science, Barcelona Supercomputing Centre, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1962692023-01-12T18:29:43Z2023-01-12T18:29:43ZHow do snowflakes form? Is each snowflake really unique? Why is some snow light and fluffy or heavy? The amazing science of snow<figure><img src="https://images.theconversation.com/files/504098/original/file-20230111-46586-breuxu.jpg?ixlib=rb-1.1.0&rect=0%2C75%2C656%2C479&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">If you catch a snowflake, take a moment to look at it: It's a formation no one has ever seen before.</span> <span class="attribution"><span class="source">(Damian McCoig/Unsplash)</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/how-do-snowflakes-form-is-each-snowflake-really-unique-why-is-some-snow-light-and-fluffy-or-heavy-the-amazing-science-of-snow" width="100%" height="400"></iframe>
<p>In northern communities, <a href="https://www.cbc.ca/news/canada/saskatchewan/year-weather-2022-1.6693807">seasonal snow plays a central role</a> in day-to-day activities. </p>
<p>For some, it means a day off from school. For others, it’s a signal that <a href="https://www.cbc.ca/sports/u-sports-notebook-jan-10-1.6708008">skiing season is starting</a>. Or maybe it’s a harbinger of an extra long <a href="https://barrie.ctvnews.ca/wicked-winter-system-creates-messy-driving-conditions-1.6193962">commute to work</a>. It’s remarkable how many memories and emotions can be evoked by a few billion tiny ice crystals.</p>
<p>We may see snow as a blanket or drifts across the landscape or our driveway. But when was the last time you took a closer look at snow, and I mean a really close look? </p>
<p>Many a writer has mused about snowflakes as a <a href="https://libquotes.com/henry-david-thoreau/quote/lbr3v4q">natural work</a> of art. Here’s a scientific look at the amazing nature of snowflakes and snow.</p>
<figure class="align-center ">
<img alt="A person catching snow in their mouth smiling." src="https://images.theconversation.com/files/504090/original/file-20230111-20-92bhy6.jpg?ixlib=rb-1.1.0&rect=0%2C498%2C2627%2C1410&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504090/original/file-20230111-20-92bhy6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504090/original/file-20230111-20-92bhy6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504090/original/file-20230111-20-92bhy6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504090/original/file-20230111-20-92bhy6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504090/original/file-20230111-20-92bhy6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504090/original/file-20230111-20-92bhy6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">When was the last time you caught a snowflake?</span>
<span class="attribution"><span class="source">THE CANADIAN PRESS/Darryl Dyck</span></span>
</figcaption>
</figure>
<h2>How do snowflakes form?</h2>
<p>While different catalogues will say that there are <a href="https://archive.las.iastate.edu/2014/01/17/how-snowflakes-get-their-shapes/">seven types of snowflakes</a>, <a href="https://www.compoundchem.com/2014/12/10/snowflakes/">or eight</a> <a href="https://www.smithsonianmag.com/smart-news/snowflakes-all-fall-one-35-different-shapes-180953760/">or 35</a>, we are probably most familiar with <a href="https://www.buffalo.edu/news/tipsheets/2018/001.html">the classic six-sided dendrite forms</a>, characterized by elaborate and nearly symmetrical branches. You know, the type that you would <a href="https://assets.marthastewart.com/d18/snowflake-template/snowflake-template.pdf">cut out of a piece of paper</a>. </p>
<p>The dendrite form is a study in water chemistry. When ice forms at the molecular level, the angle between the hydrogen and oxygen atoms will always <a href="http://www.ankn.uaf.edu/curriculum/athabascan/observingsnow/stuff.html#">be 120 degrees</a>;
put three of these together to get a full ring of molecules with a six-sided structure. In fact, every time a water molecule attaches itself to this ring, it will do so at the same angle. </p>
<p>As the snowflake grows, the attachment of water molecules is determined <a href="https://scied.ucar.edu/learning-zone/storms/snowflakes#">by the temperature</a> and humidity of the air. Since these characteristics don’t change too much at the size of a growing snowflake, those attachments tend to occur evenly across the six points of the hexagonal flake. </p>
<p>Molecule by molecule, the snowflake grows and eventually begins to fall. This takes the snowflake to a <a href="https://education.nationalgeographic.org/resource/atmosphere">new part of the atmosphere</a>, where temperature and humidity are different, resulting in new ice structures forming, but still with the same set of angles.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/JK0x-jNJ-ns?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Video about ice and snow crystal growth with physics professor Ken Libbrecht.</span></figcaption>
</figure>
<h2>Is each snowflake really unique?</h2>
<p>A typical dendrite is made up of <a href="https://www.snexplores.org/article/how-snowflake-made">about a quintillion</a> (that’s a one with 18 zeroes after it) individual water molecules. Given slight changes in temperature and humidity and the huge number of molecules and bonding opportunities involved, the ice structures created can be incredibly diverse and complicated.</p>
<p>For this reason, it is entirely likely that no two snowflakes form in exactly the same way, and consequently no two snowflakes are alike. </p>
<p><a href="https://www.newscientist.com/article/mg25233653-800-kenneth-libbrecht-interview-a-grand-unified-theory-of-snowflakes/">Twin snowflakes have been grown in a lab</a>, where temperature and humidity are closely controlled, but that’s a bit of a cheat.</p>
<h2>Why is some snow light and fluffy and some is heavy?</h2>
<figure class="align-right ">
<img alt="A red cardinal sits in snowy branches as snow falls all around." src="https://images.theconversation.com/files/503870/original/file-20230110-4890-h790cv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/503870/original/file-20230110-4890-h790cv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=692&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503870/original/file-20230110-4890-h790cv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=692&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503870/original/file-20230110-4890-h790cv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=692&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503870/original/file-20230110-4890-h790cv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=870&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503870/original/file-20230110-4890-h790cv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=870&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503870/original/file-20230110-4890-h790cv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=870&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Freshly fallen snow tends to be light and fluffy because the flakes take up a lot of space.</span>
<span class="attribution"><span class="source">THE CANADIAN PRESS/Justin Tang</span></span>
</figcaption>
</figure>
<p>The story of snow crystal growth doesn’t end high above in the clouds. Once the snowflakes reach the ground and accumulate as a blanket of snow, they begin to change. </p>
<p>Freshly fallen snow tends to be light and fluffy because the flakes take up a lot of space and there is a lot of air between and within them. But over time, they break apart, pack tighter together and the density increases. </p>
<p>This process <a href="https://doi.org/10.3189/S0022143000019535">is known as sintering</a> and is useful for building snow shelters like igloos and quinzees. But some of the most remarkable changes happen at the bottom of the snowpack, where warmth from the ground below and cold from the air above interact. </p>
<p>Through a process of sublimation — water molecules change from ice directly to vapour, skipping the liquid phase — and refreezing, cup-shaped crystals a few centimetres across <a href="https://utahavalanchecenter.org/blog/28021">known as depth hoar</a> can form. Though beautiful to look at, depth hoar has a low density and when it forms on a steep slope there is a chance for the snowpack to slide as an avalanche.</p>
<p>So next time you’re out in the snow, even if you’re grumbling about having to shovel the driveway for the umpteenth time this winter, take a moment to catch a snowflake on your mitten and have a look at it. You’re looking at a formation
no one has ever seen before.</p>
<p>Check out physics professor <a href="https://press.princeton.edu/books/hardcover/9780691200378/snow-crystals">Kenneth Libbrecht’s</a> website <a href="http://www.snowcrystals.com/">for a full description</a> of snowflake forms.</p><img src="https://counter.theconversation.com/content/196269/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Krystopher Chutko 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>Molecule by molecule, a snowflake grows and eventually begins to fall. A scientific look at the amazing nature of snowflakes and snow.Krystopher Chutko, Assistant Professor, Department of Geography and Planning, University of SaskatchewanLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1963862022-12-29T20:56:44Z2022-12-29T20:56:44ZThe sky isn’t just blue – airglow makes it green, yellow and red too<figure><img src="https://images.theconversation.com/files/502097/original/file-20221220-6052-nvokjs.JPG?ixlib=rb-1.1.0&rect=0%2C7%2C4920%2C3268&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://eol.jsc.nasa.gov/SearchPhotos/photo.pl?mission=ISS043&roll=E&frame=143486">NASA</a></span></figcaption></figure><p>Look up on a clear sunny day and you will see a blue sky. But is this the true colour of the sky? Or is it the only colour of the sky? </p>
<p>The answers are a little complicated, but they involve the nature of light, atoms and molecules and some quirky parts of Earth’s atmosphere. And big lasers too – for science!</p>
<h2>Blue skies?</h2>
<p>So first things first: when we see a blue sky on a sunny day, what are we seeing? Are we seeing blue nitrogen or blue oxygen? The simple answer is no. Instead the blue light we see is scattered sunlight. </p>
<p>The Sun produces a broad <a href="https://science.nasa.gov/ems/09_visiblelight">spectrum of visible light</a>, which we see as white but it includes all the colours of the rainbow. When sunlight passes through the air, atoms and molecules in the atmosphere scatter blue light in all directions, far more than red light. This is called <a href="https://theconversation.com/curious-kids-why-is-the-sky-blue-and-where-does-it-start-81165">Rayleigh scattering</a>, and results in a white Sun and blue skies on clear days.</p>
<p>At sunset we can see this effect dialled up, because sunlight has to pass through more air to reach us. When the Sun is close to the horizon, almost all the blue light is scattered (or absorbed by dust), so we end up with a red Sun with bluer colours surrounding it. </p>
<p>But if all we are seeing is scattered sunlight, what is the true colour of the sky? Perhaps we can get an answer at night.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-is-the-sky-blue-and-where-does-it-start-81165">Curious Kids: Why is the sky blue and where does it start?</a>
</strong>
</em>
</p>
<hr>
<h2>The colour of dark skies</h2>
<p>If you look at the night sky, it is obviously dark, but it isn’t perfectly black. Yes, there are the stars, but the night sky itself glows. This isn’t light pollution, but the atmosphere glowing naturally. </p>
<p>On a dark moonless night in the countryside, away from city lights, you can see the trees and hills silhouetted against the sky. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/502094/original/file-20221220-13-trarsj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/502094/original/file-20221220-13-trarsj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502094/original/file-20221220-13-trarsj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502094/original/file-20221220-13-trarsj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502094/original/file-20221220-13-trarsj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502094/original/file-20221220-13-trarsj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502094/original/file-20221220-13-trarsj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502094/original/file-20221220-13-trarsj.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">Trees are silhouetted against the glowing night sky.</span>
<span class="attribution"><span class="source">Rodney Campbell / flickr</span></span>
</figcaption>
</figure>
<p>This glow, called <a href="https://theconversation.com/beautiful-green-airglow-spotted-by-aurora-hunters-but-what-is-it-68188">airglow</a>, is produced by atoms and molecules in the atmosphere. In visible light, oxygen produces green and red light, hydroxyl (OH) molecules produce red light, and sodium produces a sickly yellow. Nitrogen, while far more abundant in the air than sodium, does not contribute much to airglow.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/beautiful-green-airglow-spotted-by-aurora-hunters-but-what-is-it-68188">Beautiful green 'airglow' spotted by aurora hunters – but what is it?</a>
</strong>
</em>
</p>
<hr>
<p>The distinct colours of airglow are the result of atoms and molecules releasing particular amounts of energy (quanta) in the form of light. For example, at high altitudes ultraviolet light can split oxygen molecules (O₂) into pairs of oxygen atoms, and when these atoms later <a href="https://theconversation.com/beautiful-green-airglow-spotted-by-aurora-hunters-but-what-is-it-68188">recombine into oxygen molecules they produce a distinct green light</a>. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/EwqWdy_ZUX8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">You can see airglow at dark sites, such as the European Southern Observatory in Chile.</span></figcaption>
</figure>
<h2>Yellow light, shooting stars and sharp images</h2>
<p>Sodium atoms make up a minuscule fraction of our atmosphere, but they make up a big part of airglow, and have a very unusual origin – shooting stars. </p>
<p>You can see shooting stars on any clear dark night, if you’re willing to wait. They are teensy tiny meteors, produced by grains of dust heating up and vaporising in the upper atmosphere as they travel at over 11 kilometres per second. </p>
<p>As shooting stars blaze across the sky, at roughly 100 kilometres altitude, they leave behind a trail of atoms and molecules. Sometimes you can see shooting stars with distinct colours, resulting from the atoms and molecules they contain. Very bright shooting stars can even leave visible smoke trails. And among those atoms and molecules is a smattering of sodium.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/502235/original/file-20221220-6028-umwpul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A shooting star and airglow seen from the International Space Station." src="https://images.theconversation.com/files/502235/original/file-20221220-6028-umwpul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502235/original/file-20221220-6028-umwpul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502235/original/file-20221220-6028-umwpul.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502235/original/file-20221220-6028-umwpul.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502235/original/file-20221220-6028-umwpul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502235/original/file-20221220-6028-umwpul.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502235/original/file-20221220-6028-umwpul.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">A shooting star and airglow seen from the International Space Station.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>This high layer of sodium atoms is actually useful to astronomers. Our atmosphere is perpetually in motion, it’s turbulent, and it blurs images of planets, stars and galaxies. Think of the shimmering you see when you look along a long road on a summer’s afternoon. </p>
<p>To compensate for the turbulence, astronomers take quick images of bright stars and measure how the stars’ images are distorted. A special deformable mirror can be adjusted to remove the distortion, producing images that can be sharper than the ones from space telescopes. (Although space telescopes still have the advantage of not peering through airglow.)</p>
<p>This technique – called “adaptive optics” – is powerful, but there’s a big problem. There are not enough natural bright stars for adaptive optics to work over the whole sky. So astronomers make their own artificial stars in the night sky, called “laser guide stars”. </p>
<p>Those sodium atoms are high above the turbulent atmosphere, and we can make them glow brightly by firing a power laser at them tuned to the distinct yellow of sodium. The resulting artificial star can then be used for adaptive optics. The shooting star you see at night helps us see the Universe with sharper vision.</p>
<p>So the sky isn’t blue, at least not always. It is a glow-in-the-dark night sky too, coloured a mix of green, yellow and red. Its colours result from scattered sunlight, oxygen, and sodium from shooting stars. And with a little bit of physics, and some big lasers, we can make artificial yellow stars to get sharp images of our cosmos. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/mEJnEMtGYD8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Sodium laser guide stars at ESO’s Very Large Telescope in Chile.</span></figcaption>
</figure><img src="https://counter.theconversation.com/content/196386/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael J. I. Brown receives research funding from the Australian Research Council and Monash University.
</span></em></p><p class="fine-print"><em><span>Matthew Kenworthy receives research funding from the Nederlandse Organisatie voor Wetenschappelijk (Dutch Science Council) and has previously received funding from NASA, the National Science Foundation and the Nederlandse Onderzoekschool voor Astronomie (NOVA). </span></em></p>The sky looks blue on a sunny day – but at night we can see the faint glow of its true colour.Michael J. I. Brown, Associate Professor in Astronomy, Monash UniversityMatthew Kenworthy, Associate professor in Astronomy, Leiden UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1967132022-12-20T13:36:46Z2022-12-20T13:36:46Z2022’s US climate disasters, from storms and floods to heat waves and droughts<figure><img src="https://images.theconversation.com/files/501982/original/file-20221219-16-o96kqe.jpg?ixlib=rb-1.1.0&rect=500%2C20%2C1732%2C1091&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rain and fast snowmelt sent the Yellowstone River and nearby streams raging beyond their banks in June 2022.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/YEClimateChangePhotos2022/647437279ccf446abe297139183af11f/photo">AP Photo/David Goldman</a></span></figcaption></figure><p>The year 2022 will be remembered across the U.S. for its devastating flooding and storms – and also for its extreme heat waves and droughts.</p>
<p>The nation saw <a href="https://www.ncei.noaa.gov/access/billions/events/US/2022?disasters%5B%5D=all-disasters">18 disasters</a> that caused more than US$1 billion in damage each, well above the average. The year started and ended with widespread severe winter storms from Texas to Maine, affecting tens of million of people and causing significant damages. Then, March <a href="https://www.nbcnews.com/news/weather/march-sets-record-tornado-reports-rcna22537">set the record</a> for the most reported <a href="https://theconversation.com/tornadoes-climate-change-and-why-dixie-is-the-new-tornado-alley-178863">tornadoes</a> in the month – 233.</p>
<p>During a period of five weeks over the summer, <a href="https://www.washingtonpost.com/climate-environment/2022/08/23/flood-united-states-climate-explainer/">five 1,000-year rainfall events</a> occurred in <a href="https://www.weather.gov/lsx/July262022Flooding">St. Louis</a>, <a href="https://theconversation.com/climate-change-is-intensifying-the-water-cycle-bringing-more-powerful-storms-and-flooding-heres-what-the-science-shows-187951">eastern Kentucky</a>, <a href="https://news.yahoo.com/illinois-flash-flooding-rain-climate-change-184218523.html">southern Illinois</a>, California’s <a href="https://www.nps.gov/deva/learn/news/death-valley-experiences-1-000-year-rain-event.htm">Death Valley</a> and <a href="https://www.texastribune.org/2022/08/22/dallas-flooding-fort-worth/">Dallas</a>, causing devastating and sometimes deadly flash floods. Severe flooding in Mississippi <a href="https://theconversation.com/intense-heat-and-flooding-are-wreaking-havoc-on-power-and-water-systems-as-climate-change-batters-americas-aging-infrastructure-189761">knocked out Jackson’s troubled water supply</a> for weeks. A <a href="https://theconversation.com/climate-change-is-making-flooding-worse-3-reasons-the-world-is-seeing-more-record-breaking-deluges-and-flash-floods-185364">historic flood in Montana</a>, brought on by heavy rain and melting snow, forced large areas of Yellowstone National Park to be evacuated. </p>
<p>In the fall, <a href="https://www.weather.gov/ilm/HurricaneIan">hurricanes Ian</a> and <a href="https://www.weather.gov/sju/fiona2022">Fiona</a> deluged Florida and Puerto Rico with over 2 feet (0.6 meters) of rain in areas and deadly, destructive storm surge. Ian became <a href="https://apnews.com/article/floods-europe-pakistan-climate-and-environment-87a354ddc9f2333e3175d0578c50a592">one of the most expensive</a> hurricanes in U.S. history. And a <a href="https://theconversation.com/typhoon-merbok-fueled-by-unusually-warm-pacific-ocean-pounded-alaskas-vulnerable-coastal-communities-at-a-critical-time-190898">typhoon pounded</a> 1,000 miles (1,600 km) of the Alaska coast. </p>
<figure class="align-center ">
<img alt="A girl in rain boots walks through a mud-filled yard. Damaged mattresses and other belongings from a flooded house are piled nearby." src="https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=452&fit=crop&dpr=1 600w, https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=452&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=452&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=568&fit=crop&dpr=1 754w, https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=568&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/484438/original/file-20220913-14-z0q39y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=568&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Flash flooding swept through mountain valleys in eastern Kentucky in July 2022, killing more than three dozen people. It was one of several destructive flash floods.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/local-fire-chief-and-his-daughter-drop-off-goods-for-a-news-photo/1242236541">Seth Herald/AFP via Getty Images</a></span>
</figcaption>
</figure>
<p>While too much rainfall threatened some regions, extreme heat and too little precipitation worsened risks elsewhere.</p>
<p>Persistent heat waves lingered over many parts of the country, setting temperature records. Wildfires raged in <a href="https://tucson.com/news/local/photos-wildfires-in-arizona-2022/collection_6555f988-c4dd-11ec-a7da-effb4de9da49.html#1">Arizona</a> and <a href="https://www.nytimes.com/2022/12/10/business/new-mexico-climate-change-wildfires-floods.html">New Mexico</a> on the background of a <a href="https://www.nature.com/articles/s41558-022-01290-z">megadrought in the Southwestern U.S.</a> more severe than anything the region has experienced in at least 1,200 years. </p>
<p>Drought also left the <a href="https://theconversation.com/record-low-water-levels-on-the-mississippi-river-in-2022-show-how-climate-change-is-altering-large-rivers-193920">Mississippi River so low</a> near Memphis in the fall that barges couldn’t get through without additional dredging and upstream water releases. That snarled grain shipping during the <a href="https://www.bloomberg.com/graphics/2022-mississippi-river-drought-global-impact/?sref=Hjm5biAW">critical harvest period</a>. Along the Colorado River, officials discussed even tighter water use restrictions as <a href="https://www.washingtonpost.com/climate-environment/2022/12/17/colorado-river-crisis-conference/">water levels neared dangerously low levels</a> in the major reservoirs. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/503887/original/file-20230110-13-zrsvbi.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map showing disasters, including several severe storms" src="https://images.theconversation.com/files/503887/original/file-20230110-13-zrsvbi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503887/original/file-20230110-13-zrsvbi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=327&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503887/original/file-20230110-13-zrsvbi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=327&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503887/original/file-20230110-13-zrsvbi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=327&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503887/original/file-20230110-13-zrsvbi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=410&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503887/original/file-20230110-13-zrsvbi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=410&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503887/original/file-20230110-13-zrsvbi.png?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">2022 had 18 disasters that exceeded $1 billion each in damage.</span>
<span class="attribution"><a class="source" href="https://www.ncei.noaa.gov/access/billions/">NCEI/NOAA</a></span>
</figcaption>
</figure>
<p>The United States was hardly alone in its climate disasters.</p>
<p>In Pakistan, <a href="https://theconversation.com/pakistan-floods-what-role-did-climate-change-play-189833">record monsoon rains</a> inundated more than one-third of the country, killing over 1,500 people. In <a href="https://www.newyorker.com/magazine/2022/08/01/living-through-indias-next-level-heat-wave">India</a> and <a href="https://www.theguardian.com/world/2022/sep/07/china-reports-most-severe-heatwave-and-lowest-rainfall-on-record">China</a>, prolonged heat waves and droughts dried up rivers, disrupted power grids and threatened food security for billions of people. Widespread flooding and mudslides brought on by torrential rains also killed hundreds of people <a href="https://www.cnn.com/2022/05/13/africa/south-africa-floods-climate-intl/index.html">in South Africa</a>, <a href="https://www.reuters.com/world/americas/death-toll-brazilian-floods-rises-57-thousands-displaced-2022-05-29/">Brazil</a> and <a href="https://www.nytimes.com/2022/10/17/world/africa/nigeria-floods.html">Nigeria</a>.</p>
<p>In Europe, heat waves set record temperatures <a href="https://www.washingtonpost.com/world/2022/07/28/human-caused-climate-change-made-uk-heat-wave-10-times-more-likely-study-says/">in Britain</a> and other parts of the continent, leading to severe droughts, <a href="https://www.theguardian.com/environment/2022/aug/13/europes-rivers-run-dry-as-scientists-warn-drought-could-be-worst-in-500-years">low river flows that slowed shipping</a>, and wildfires in many parts of the continent. Much of East Africa is still in the grips of a multiyear drought – the <a href="https://news.un.org/en/story/2022/11/1131107">worst in over 40 years</a>, according to the United Nations – leaving millions of people vulnerable to food shortages and starvation. The last eight years have been the <a href="https://www.ncei.noaa.gov/access/monitoring/monthly-report/global/202213">warmest in over 140 years</a> of record-keeping.</p>
<p>This isn’t just a freak year: Such extreme events are occurring with increasing frequency and intensity.</p>
<h2>Climate change is intensifying these disasters</h2>
<p>The most <a href="https://theconversation.com/climate-change-is-intensifying-the-water-cycle-bringing-more-powerful-storms-and-flooding-heres-what-the-science-shows-187951">recent global climate assessment</a> from the United Nations Intergovernmental Panel on Climate Change found significant increases in both the frequency and intensity of extreme temperature and precipitation events, leading to more droughts and floods.</p>
<p>Extreme flooding and droughts are also <a href="https://doi.org/10.1038/s41586-022-04917-5">getting deadlier and more expensive</a>, despite an improving capacity to manage climate risks, a study published in 2022 found. Part of the reason is that today’s extreme events, enhanced by climate change, often exceed communities’ management capabilities.</p>
<figure class="align-center ">
<img alt="A woman with her eyes closed holds a screaming 1-year-old boy in a National Guard helicopter, with a guard member standing in the open helicopter door." src="https://images.theconversation.com/files/485651/original/file-20220920-14-jz4qqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/485651/original/file-20220920-14-jz4qqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/485651/original/file-20220920-14-jz4qqj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/485651/original/file-20220920-14-jz4qqj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/485651/original/file-20220920-14-jz4qqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/485651/original/file-20220920-14-jz4qqj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/485651/original/file-20220920-14-jz4qqj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A family had to be airlifted from their home in eastern Kentucky after it was surrounded by floodwater in July 2022.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/command-sergeant-major-tim-lewis-of-the-kentucky-national-news-photo/1242203173">Michael Swensen/Getty Images</a></span>
</figcaption>
</figure>
<p>Extreme events, by definition, occur rarely. A 100-year flood has a 1% chance of happening in any given year. So when such events occur with increasing frequency and intensity, they are a clear indication of a changing climate state.</p>
<h2>Climate models showed these risks were coming</h2>
<p>Much of this is well understood and consistently reproduced by climate models.</p>
<p>As the climate warms, a shift in temperature distribution leads to more extremes. For example, globally, a 1 degree Celsius increase in annual average temperature is associated with a 1.2 C to 1.9 C (2.1 Fahrenheit to 3.4 F) <a href="https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter11.pdf">increase in the annual maximum temperature</a>.</p>
<figure class="align-center ">
<img alt="A man works on a car with an older mechanic in overalls standing next to him under the shade of a large beach umbrealla." src="https://images.theconversation.com/files/485653/original/file-20220920-11202-l4elwo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/485653/original/file-20220920-11202-l4elwo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/485653/original/file-20220920-11202-l4elwo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/485653/original/file-20220920-11202-l4elwo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/485653/original/file-20220920-11202-l4elwo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/485653/original/file-20220920-11202-l4elwo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/485653/original/file-20220920-11202-l4elwo.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">Heat waves, like the heat dome over the South in July 2022, can hit outdoor workers especially hard.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/community-mechanic-lloyd-bush-works-on-a-neighbors-vehicle-news-photo/1410189284">Brandon Bell/Getty Images</a></span>
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</figure>
<p>In addition, global warming leads to changes in how the atmosphere and ocean move. The temperature difference between the equator and the poles is the driving force for global wind. As the polar regions warm at much higher rates than the equator, the reduced temperature difference causes a weakening of global winds and leads to a <a href="https://e360.yale.edu/features/global-stilling-is-climate-change-slowing-the-worlds-wind">more meandering jet stream</a>.</p>
<p>Some of these changes can create conditions such as persistent high-pressure systems and atmospheric blocking that bring more intense heat waves. The <a href="https://theconversation.com/what-is-a-heat-dome-an-atmospheric-scientist-explains-the-weather-phenomenon-baking-california-and-the-west-185569">heat domes</a> over the Southern Plains and South in June and in the West in September were both examples.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1538941467686756352"}"></div></p>
<p>Warming can be further amplified by positive feedbacks.</p>
<p>For example, <a href="https://www.ncei.noaa.gov/news/global-climate-202212">higher temperatures</a> tend to dry out the soil, and less soil moisture reduces the land’s heat capacity, making it easier to heat up. More frequent and persistent heat waves lead to excessive evaporation, combined with decreased precipitation in some regions, causing more severe droughts and more frequent wildfires. </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>Higher temperatures <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">increase the atmosphere’s capacity</a> to hold moisture at a rate of about 7% per degree Celsius. This increased humidity leads to heavier rainfall events. </p>
<p>In addition, storm systems are <a href="https://thinktv.pbslearningmedia.org/resource/nves.sci.earth.hurricane/water-vapor-fuels-hurricanes/">fueled by latent heat</a> – the large amount of energy released when water vapor condenses to liquid water. Increased moisture content in the atmosphere also enhances latent heat in storm systems, increasing their intensity. Extreme heavy or persistent rainfall leads to increased flooding and landslides, with devastating social and economic consequences.</p>
<p>Even though it’s difficult to link specific extreme events directly to climate change, when these supposedly rare events occur with greater frequency in a warming world, it is hard to ignore the changing state of our climate. </p>
<h2>The new abnormal</h2>
<p>This year might provide a glimpse of our near future, as these extreme climate events become more frequent.</p>
<p>To say this is the “new normal,” though, is misleading. It suggests that we have reached a new stable state, and that is far from the truth. Without serious effort to curb greenhouse gas emissions, this trend toward more extreme events will continue. </p>
<p><em>This article was updated Jan. 12, 2023, with the release of NOAA’s billion-dollar disaster list and global temperatures for 2022.</em></p><img src="https://counter.theconversation.com/content/196713/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shuang-Ye Wu 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>Millions of people around the world suffered through deadly flooding and long-lasting heat waves in 2022. A climate scientist explains the rising risks.Shuang-Ye Wu, Professor of Geology and Environmental Geosciences, University of DaytonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1968722022-12-20T04:34:03Z2022-12-20T04:34:03ZWhat is air turbulence?<figure><img src="https://images.theconversation.com/files/502061/original/file-20221220-18-124g72.jpg?ixlib=rb-1.1.0&rect=29%2C14%2C4882%2C3254&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/iiqpxCg2GD4">Philip Myrtorp / Unsplash</a></span></figcaption></figure><p>You probably know the feeling: you’re sitting on a plane, happily cruising through the sky, when suddenly the seat-belt light comes on and things get a little bumpy.</p>
<p>Most of the time, turbulence leads to nothing worse than momentary jitters or perhaps a spilled cup of coffee. In rare cases, passengers or flight attendants might end up with some injuries.</p>
<p>What’s going on here? Why are flights usually so stable, but sometimes get so unsteady?</p>
<p>As a meteorologist and atmospheric scientist who studies air turbulence, let me explain.</p>
<h2>What is air turbulence?</h2>
<p>Air turbulence is when the air starts to flow in a chaotic or random way. </p>
<p>At high altitudes the wind usually moves in a smooth, horizontal current called “laminar flow”. This provides ideal conditions for steady flight.</p>
<figure class="align-center ">
<img alt="A diagram showing laminar flow and turbulent flow." src="https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In ‘laminar flow’, air moves smoothly in one direction. When turbulence begins, it goes every which way.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Turbulence occurs when something disrupts this smooth flow, and the air starts to move up and down as well as horizontally. When this happens, conditions can change from moment to moment and place to place.</p>
<p>You can think of normal flying conditions as the glassy surface of the ocean on a still day. But when a wind comes up, things get choppy, or waves form and break – that’s turbulence.</p>
<h2>What causes air turbulence?</h2>
<p>The kind of turbulence that affects commercial passenger flights has three main causes.</p>
<p>The first is thunderstorms. Inside a thunderstorm, there is strong up-and-down air movement, which makes a lot of turbulence that can spread out to the surrounding region. Thunderstorms can also create “atmospheric waves”, which travel through the surrounding air and eventually break, causing turbulence. </p>
<p>Fortunately, pilots can usually see thunderstorms ahead (either with the naked eye or on radar) and will make efforts to go around them.</p>
<p>The other common causes of turbulence create what’s typically called “clear-air turbulence”. It comes out of air that looks perfectly clear, with no clouds, so it’s harder to dodge.</p>
<figure class="align-center ">
<img alt="A diagram showing mountains, air currents and turbulence." src="https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=464&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=464&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=464&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=583&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=583&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=583&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Jet streams and mountains are common causes of clear-air turbulence.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The second cause of turbulence is jet streams. These are high-speed winds in the upper atmosphere, at the kind of altitudes where passenger jets fly. </p>
<p>While air inside the jet stream moves quite smoothly, there is often turbulence near the top and bottom of the stream. That’s because there is a big difference in air speed (called “wind shear”) between the jet stream and the air outside it. High levels of wind shear create turbulence.</p>
<p>The third thing that makes turbulence is mountains. As air flows over a mountain range, it creates another kind of wave – called, of course, a “mountain wave” – that disrupts air flow and can create turbulence.</p>
<h2>Can air turbulence be avoided?</h2>
<p>Pilots do their best to avoid air turbulence – and they’re pretty good at it!</p>
<p>As mentioned, thunderstorms are the easiest to fly around. For clear-air turbulence, things are a little trickier.</p>
<p>When pilots encounter turbulence, they will change altitude to try to avoid it. They also report the turbulence to air traffic controllers, who pass the information on to other flights in the area so they can try to avoid it. </p>
<p>Weather forecasting centres also provide turbulence forecasts. Based on their models of what’s happening in the atmosphere, they can predict where and when clear-air turbulence is likely to occur.</p>
<h2>Will climate change make turbulence worse?</h2>
<p>As the globe warms and the climate changes in coming decades, we think air turbulence will also be affected.</p>
<p>One reason is that the jet streams which can cause turbulence are shifting and may become more intense. As Earth’s tropical climate zones spread away from the equator, the jet streams are moving with them.</p>
<p>This is likely to increase turbulence on at least some flight routes. Some studies also <a href="https://www.nature.com/articles/s41586-019-1465-z">suggest</a> the wind shear around jet streams has become more intense.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/could-climate-change-have-played-a-role-in-the-airasia-crash-36002">Could climate change have played a role in the AirAsia crash?</a>
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<p>Another reason is that the most severe thunderstorms are also likely to become more intense, partly because a warmer atmosphere can hold more water vapour. This too is likely to generate more intense turbulence.</p>
<p>These predictions are largely based on climate models, because it is difficult to collect the data needed to identify trends in air turbulence. These data largely come from reports by aircraft, the quality and extent of which are changing over time. These measurements are quite different from the long-term, methodically gathered data usually used to detect trends in the weather and climate.</p>
<h2>How dangerous is air turbulence?</h2>
<p>Around the globe, air turbulence causes hundreds of injuries each year among passengers and flight attendants on commercial aircraft. But, given the hundreds of millions of people who fly each year, those are pretty good odds.</p>
<p>Turbulence is usually short-lived. What’s more, modern aircraft are engineered to comfortably withstand all but the most extreme air turbulence. </p>
<p>And among people who are injured, the great majority are those who aren’t strapped in. So if you’re concerned, the easiest way to protect yourself is to wear your seat belt. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/heres-the-real-reason-to-turn-on-aeroplane-mode-when-you-fly-188585">Here's the real reason to turn on aeroplane mode when you fly</a>
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<img src="https://counter.theconversation.com/content/196872/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Todd Lane receives funding from the Australian Research Council.</span></em></p>When something disrupts the smooth, laminar flow of high-altitude winds, your flight might get a little bumpy.Todd Lane, Professor, School of Geography, Earth and Atmospheric Sciences, The University of Melbourne, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1960352022-12-20T00:20:13Z2022-12-20T00:20:13ZArtist Tomás Saraceno wants to improve our knowledge about atmospheres – and arachnids<figure><img src="https://images.theconversation.com/files/501783/original/file-20221219-13-is3nbf.jpg?ixlib=rb-1.1.0&rect=29%2C9%2C6544%2C4366&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">How to entangle the universe in a spider/web?, 2022, Tomás Saraceno. Courtesy the artist with thanks to Arachnophilia, neugerriemschneider, Berlin and Tanya Bonakdar Gallery, New York / Los Angeles.</span> <span class="attribution"><span class="source">Photo Credit: Mona/Jesse Hunniford Image Courtesy Studio Tomás Saraceno and MONA Museum of Old and New Art, Hobart, Tasmania, Australia</span></span></figcaption></figure><p>In Oceans of Air, the new exhibition at Hobart’s Mona, artist Tomás Saraceno imagines a future where humans become as sensitive to the environment as a spider in its web. He invites visitors to become participants in his multiple networks and projects. He aims to make us aware of our interconnections with each other and the world. </p>
<p>Held in the underground labyrinthine galleries of Mona, we are invited to reconsider the boundaries between natural and cultural worlds. </p>
<p>As we descend through Mona’s central staircases, the reflective sculptural orbs Aerocene 4 and 5 weave Mona’s architecture and collections into the Saraceno world. Stairs and artworks twist and turn in the reflections. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/501759/original/file-20221219-25-j9r7xh.jpg?ixlib=rb-1.1.0&rect=30%2C10%2C6679%2C4456&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/501759/original/file-20221219-25-j9r7xh.jpg?ixlib=rb-1.1.0&rect=30%2C10%2C6679%2C4456&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/501759/original/file-20221219-25-j9r7xh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501759/original/file-20221219-25-j9r7xh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501759/original/file-20221219-25-j9r7xh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501759/original/file-20221219-25-j9r7xh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501759/original/file-20221219-25-j9r7xh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501759/original/file-20221219-25-j9r7xh.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">Aerocene 2.5, 4, and 5, 2018, Tomás Saraceno Courtesy the artist with the Aerocene Foundation, neugerriemschneider, Berlin and Tanya Bonakdar Gallery, New York / Los Angeles.</span>
<span class="attribution"><span class="source">Photo Credit: Mona/Jesse Hunniford Image Courtesy Studio Tomás Saraceno and MONA Museum of Old and New Art, Hobart, Tasmania, Australia</span></span>
</figcaption>
</figure>
<p>Reminiscent of Escher’s <a href="https://en.wikipedia.org/wiki/Relativity_(M._C._Escher)">1923 Relativity lithograph</a>, the laws of gravity are confounded. The binding on the balloons could be tethering them to the building or preventing their fall, like eggs in a spider web.</p>
<p>Before entering the dark subterranean galleries, a photograph shows Saraceno floating below a fuel-free hot air balloon on the boundary between earth and sky. </p>
<h2>A multi-sensory experience</h2>
<p>Argentinean Tomás Saraceno is a Berlin-based artist, interested in collaborations with research institutes to further our collective knowledge around atmospheres and arachnids.</p>
<p>Submerging into dark gallery spaces may seem a strange phenomenon for an exhibition titled Oceans of Air, however Saraceno and Mona curators Emma Pike and Olivier Varenne have carefully orchestrated the experience. They play with beams of light and the twisting turns of the galleries to make participants slow down and engage in a multi-sensory experience.</p>
<p>Within one darkened room, we encounter Particular Matter(s), 2021, a single light beam travelling across space, landing as a moon formation on the felted wall. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/501775/original/file-20221219-14-nzzq9p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/501775/original/file-20221219-14-nzzq9p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/501775/original/file-20221219-14-nzzq9p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501775/original/file-20221219-14-nzzq9p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501775/original/file-20221219-14-nzzq9p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501775/original/file-20221219-14-nzzq9p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501775/original/file-20221219-14-nzzq9p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501775/original/file-20221219-14-nzzq9p.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">Particular Matter(s), 2021, Tomás Saraceno. Courtesy the artist, neugerriemschneider, Berlin and Tanya Bonakdar Gallery, New York / Los Angeles.</span>
<span class="attribution"><span class="source">Photo Credit: Mona/Jesse Hunniford Image Courtesy Studio Tomás Saraceno and MONA Museum of Old and New Art, Hobart, Tasmania, Australia</span></span>
</figcaption>
</figure>
<p>Floating in this light beam (according to the guide), is cosmic dust, PM2.5 (particulate matter), stellar wind, air movement, kinaesthetic feedback and sonic waves. </p>
<p>In other words: the dust and atmospheric conditions present in the gallery today. </p>
<p>Adjacent is a photograph, NORAD 40983 (2015-059B), 2016 displaying the <a href="https://en.wikipedia.org/wiki/Large_Magellanic_Cloud">Large Magellanic Cloud</a>, one of the closest galaxies to our own Milky Way, with a line revealing the trail of a satellite. Saraceno encountered this image when visiting Bolivia’s <a href="https://en.wikipedia.org/wiki/Salar_de_Uyuni">Salar de Uyuni</a>, the world’s largest salt pan. </p>
<p>Here, the sky is reflected on a large salt flat. We become suspended in space, our bodies becoming insignificant matter. Standing between this photograph and the salt covered ground, we shift from godlike creatures scattering particles with our movements to an insignificant speck in the galaxy.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/an-expanding-universe-and-distant-stars-tips-on-how-to-experience-cosmology-from-your-backyard-90105">An expanding universe and distant stars: tips on how to experience cosmology from your backyard</a>
</strong>
</em>
</p>
<hr>
<h2>Fleetingly visible</h2>
<p>The images in We Do Not All Breathe the Same Air are presented in the format of moon charts revealing the natural rhythms of the solar system. </p>
<p>But instead of charting our solar system, these digital prints capture samples of air pollution collected from each state of Australia. The traces of pollutants are a physical reminder of what is invisible in this part of the world, but painfully obvious in cities like Mumbai. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/501781/original/file-20221219-25-86sbgm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/501781/original/file-20221219-25-86sbgm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/501781/original/file-20221219-25-86sbgm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501781/original/file-20221219-25-86sbgm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501781/original/file-20221219-25-86sbgm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501781/original/file-20221219-25-86sbgm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501781/original/file-20221219-25-86sbgm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501781/original/file-20221219-25-86sbgm.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">We Do Not All Breathe the Same Air, 2022, Tomás Saraceno. Courtesy the artist, neugerriemschneider, Berlin and Tanya Bonakdar Gallery, New York / Los Angeles.</span>
<span class="attribution"><span class="source">Photo Credit: Mona/Jesse Hunniford Image Courtesy Studio Tomás Saraceno and MONA Museum of Old and New Art, Hobart, Tasmania, Australia</span></span>
</figcaption>
</figure>
<p>Printed Matter(s) are exquisite images of cosmic dust invisible to the naked eye that surround us. They are printed with black carbon PM2.5 pollution extracted from the air in Mumbai on featherlight handmade paper. </p>
<p>Distantly spotlit, the images shift in and out of focus in response to currents of air. The invisible is made fleetingly visible, the insubstantial paper accentuating what is held in currents of air.</p>
<p>In Webs of At-tent(s)ion, 2022, Saraceno convincingly lays claim to the cultural activity of the “<a href="https://www.youtube.com/watch?v=t_2B5lyNt_o">More Than Human World</a>”: a phrase coined by the ecologist and philosopher David Abrams to include humans within a broader understanding of the natural world.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/501777/original/file-20221219-21-pq96ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/501777/original/file-20221219-21-pq96ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/501777/original/file-20221219-21-pq96ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501777/original/file-20221219-21-pq96ta.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501777/original/file-20221219-21-pq96ta.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501777/original/file-20221219-21-pq96ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501777/original/file-20221219-21-pq96ta.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501777/original/file-20221219-21-pq96ta.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">Webs of At-tent(s)ion, 2022, Tomás Saraceno. Courtesy the artist with Arachnophilia, neugerriemschneider, Berlin and Tanya Bonakdar Gallery, New York / Los Angeles Photo Credit: Tomás Saraceno.</span>
<span class="attribution"><span class="source">Image Courtesy Studio Tomás Saraceno and MONA Museum of Old and New Art, Hobart, Tasmania, Australia</span></span>
</figcaption>
</figure>
<p>We are presented with glass and metal frames containing exquisite spider web architectures. The constellations of webs were made from spiders invited by a thread to weave within the carbon-fibre frames provided in the space of the studio.</p>
<p>The resilience of the fully formed webs when preserved in glass boxes is made testament through surviving shipping from Saraceno’s Berlin studio. </p>
<p>These intricate universes are spotlit in the darkened gallery. Walking around these forms in the gallery reveals innovations in materials and forms undreamed of by humans.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-are-the-environmental-humanities-20040">Explainer: what are the environmental humanities?
</a>
</strong>
</em>
</p>
<hr>
<h2>New ways of being</h2>
<p>The video Living at the bottom of the ocean of air takes us into the life of the <a href="https://en.wikipedia.org/wiki/Diving_bell_spider">diving bell spider</a> who gathers a bubble of air to live under the surface of water. It is in keeping with the sensation of being in the subterranean depths of Mona where air has been trapped and circulated for our survival. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/501774/original/file-20221219-11363-60ep0w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/501774/original/file-20221219-11363-60ep0w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/501774/original/file-20221219-11363-60ep0w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501774/original/file-20221219-11363-60ep0w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501774/original/file-20221219-11363-60ep0w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501774/original/file-20221219-11363-60ep0w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501774/original/file-20221219-11363-60ep0w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501774/original/file-20221219-11363-60ep0w.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">Living at the bottom of the ocean of air, 2018, Tomás Saraceno, Courtesy the artist and Andersen’s, Copenhagen; Ruth Benzacar, Buenos Aires; Tanya Bonakdar Gallery, New York/Los Angeles; Pinksummer Contemporary Art, Genoa; neugerriemschneider, Berlin.</span>
<span class="attribution"><span class="source">Photo Credit: Mona/Jesse Hunniford Image Courtesy Studio Tomás Saraceno and MONA Museum of Old and New Art, Hobart, Tasmania, Australia</span></span>
</figcaption>
</figure>
<p>In the many rooms, we begin to realise the networks Saraceno has set up. He is weaving interconnections around the world using human technology to question itself, ask new questions and imagine new ways of being in the world.</p>
<p>Nearing the end of the exhibits we encounter Sounding the Air, 2022, which has threads of spider silk suspended between poles, inspired by <a href="https://en.wikipedia.org/wiki/Ballooning_(spider)">ballooning</a> – where some spiders release threads to take flight on currents of air. As the threads here drift in the air, their physical undulations are translated by video into sound. </p>
<p>As we exit the exhibition and once again encounter the silver orbs floating in the Mona staircases, we connect again with Saraceno’s invitation to become explorers in sympathy with the rhythms of the earth.</p>
<hr>
<p><em>Tomás Saraceno: Oceans of Air is at Mona, Hobart, until July 24.</em></p><img src="https://counter.theconversation.com/content/196035/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jan Hogan 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>This new exhibition at Hobart’s Mona captures Tomás Saraceno’s collaborations with research institutes.Jan Hogan, Senior lecturer, School of Creative Arts & Media, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1923492022-10-14T18:35:57Z2022-10-14T18:35:57ZEarth’s oxygen has varied dramatically over time – here’s how our data could help us spot alien life<figure><img src="https://images.theconversation.com/files/489539/original/file-20221013-19-882mfm.jpg?ixlib=rb-1.1.0&rect=0%2C44%2C4905%2C3150&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>Are we alone in the universe? This is a question that has intrigued humans for centuries and inspired countless studies and works of fiction. But are we getting closer to finding this out? Now that the <a href="https://webb.nasa.gov/">James Webb Space Telescope</a> (JWST) <a href="https://theconversation.com/james-webb-telescope-a-scientist-explains-what-its-first-amazing-images-show-and-how-it-will-change-astronomy-186668">is in operation</a>, we might have taken one giant leap in being able to answer this one day.</p>
<p>One of the four main objectives of the JWST is to study exoplanets – planets which reside outside of our solar system – and determine what gases their atmospheres are composed of. Now our new <a href="http://www.science.org/doi/10.1126/sciadv.abm8191">research</a> into the variation of oxygen on Earth over geological time has offered clues about what to actually look for.</p>
<p>To try and comprehend how, when and why life might evolve on other planets, it makes sense to look to the only planet we currently know of which hosts life: Earth. Understanding our own planet’s complicated evolutionary history might provide the key to finding other planets capable of supporting life.</p>
<h2>Life and oxygen</h2>
<p>We know that animals require oxygen in order to survive, although some, such as sponges, require less than others. Yet, while oxygen is readily available today, making up 21% of the atmosphere, we also know that this was <a href="https://www.nature.com/articles/nature06587">not true for the majority of Earth’s history</a>.</p>
<p>If we travelled deep into our past, beyond around 450 million years ago, we would need to carry a handy supply of oxygen tanks with us. But what we are less certain of is the absolute amount of oxygen in the atmosphere and oceans through time and whether rises in oxygen levels fuelled the evolution of animal life, or vice versa. These questions have in fact sparked numerous debates and <a href="https://www.nature.com/articles/nature13068">decades of research</a>. </p>
<p>The current thinking is that oxygen levels have risen in three broad steps. The first, called the “<a href="https://www.sciencedirect.com/science/article/pii/S0960982209011890">great oxidation event</a>”, occurred around 2.4 billion years ago, transforming the Earth from a planet essentially devoid of oxygen in the atmosphere and oceans to one with oxygen as a permanent feature of it. The third occurred around 420 million years ago and is called the “<a href="https://www.nature.com/articles/s41467-018-06383-y">Paleozoic oxygenation event</a>”, which saw a rise in atmospheric oxygen to present day levels. </p>
<p>But in between, some 800 million years ago, lies the second step: the “<a href="https://www.frontiersin.org/articles/10.3389/feart.2015.00044/full">Neoproterozoic oxygenation event</a>” or NOE. Initially, information extracted from sedimentary rocks formed on the ocean floor suggested that it was <a href="https://www.geosociety.org/gsatoday/archive/21/3/article/i1052-5173-21-3-4.htm">during this time</a> that oxygen rose to something like modern levels. </p>
<p>However, more data gathered since has suggested a more <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gbi.12182">intriguing</a> oxygen history. Importantly, the NOE occurred just <a href="https://www.pnas.org/doi/10.1073/pnas.1403669112">before evidence of the very first animals</a>, appearing around 600 million years ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="James Webb image of a cluster of galaxies about 4 billion light years from Earth." src="https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=612&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=612&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=612&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=769&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=769&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=769&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">James Webb image of a cluster of galaxies about 4 billion light years from Earth.</span>
<span class="attribution"><span class="source">NASA, ESA, CSA, and STScI</span></span>
</figcaption>
</figure>
<h2>Modelling oxygen levels</h2>
<p>We set out to explore and reconstruct atmospheric oxygen levels during the NOE to see what conditions the first animals appeared under. To do this, we built a computer model of the Earth, incorporating knowledge about the various processes which can deliver oxygen to the atmosphere or remove it.</p>
<p>We investigated carbon-bearing rocks, deposited worldwide, to calculate ancient photosynthesis rates. Photosynthesis is the process by which plants and microbes use sunlight, water and carbon dioxide to create oxygen and energy in the form of sugars – the main source of oxygen on Earth. </p>
<p>Carbon naturally exists in many <a href="https://www.energy.gov/science/doe-explainsisotopes#:%7E:text=Isotopes%20are%20members%20of%20a,and%20is%20atomic%20number%206.">isotopes</a> – atoms with a different number of neutrons in their nucleus (the nucleus is made up of protons and neutrons). Different isotopes therefore have slightly different sizes and masses from one another. </p>
<p>We looked at isotopes of carbon known as carbon-12 and carbon-13, which do not undergo radioactive decay. Plants prefer to use carbon-12 - the lightest isotope - during photosynthesis, leaving the seawater and subsequently the rocks which form on the ocean floor enriched in carbon-13 instead. </p>
<p>When we analyse these rocks, millions or even billions of years later, if we find more carbon-13 than carbon-12 we can predict that more photosynthesis, and thus more oxygen production, occurred. We then modelled volcanic activity, which can release gases that react with oxygen, removing it from the atmosphere. </p>
<p>This approach might sound a little strange, and you might ask why there was nothing more direct for us to measure. This is because most geological evidence from this time is not preserved, and these carbon isotope ratios are one of the few well-defined data sets we have through this time period.</p>
<p>What we found is that, rather than a simple jump in oxygen levels during the Neoproterozoic era, the amount of oxygen in the atmosphere changed significantly and, on geological timescales, very rapidly. While 750 million years ago, oxygen made up 12% of the atmosphere, in just a few tens of millions of years, it had dropped to about 0.3% – a tiny fraction – before rising again a few million years later. </p>
<p>Our research shows that atmospheric oxygen probably continued this dance between high and low levels until plants gained a foothold on the land some 450 million years ago.</p>
<h2>Searching for alien life</h2>
<p>These results are intriguing for a number of reasons. We have often thought that the relative stability that Earth has experienced for much of the last 4.5 billion years is necessary for life to flourish. After all, when big events, such as asteroid impacts, have occurred it has not gone well for some of Earth’s inhabitants (sorry, dinosaurs). </p>
<p>But if the first animals did evolve against a backdrop of highly variable oxygen levels, it suggests that some dynamic changes might instead be required in order to foster ecological innovation. </p>
<p>Our results suggest that periods of low atmospheric oxygen levels could have been important for developing more complex life by driving the extinction of some simple organisms and allowing the survivors to <a href="https://www.pnas.org/doi/pdf/10.1073/pnas.91.15.6758">expand and diversify</a> when oxygen levels rose again. So, we should not rule out taking a closer look at exoplanets that have a poorly oxygenated atmosphere. </p>
<p>Of course, this is a very Earth and even animal-centric view. Alien life may be completely different to life on Earth. For example, it could well exist on planetary bodies such as Titan – one of Saturn’s moons – which has seas of liquid methane and ethane. But as a starting point in our search for extra-terrestrial life, understanding the history of atmospheric oxygen on Earth is a useful guide.</p><img src="https://counter.theconversation.com/content/192349/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alex Krause received funding from the NERC SPHERES Doctoral Training Partnership NE/L002574/1.</span></em></p><p class="fine-print"><em><span>Benjamin J. W. Mills receives funding from UK Research and Innovation / NERC grant NE/S009663/1</span></em></p>We should not rule out taking a closer look at exoplanets that have a poorly oxygenated atmosphere.Alex Krause, Research Fellow in Earth System Modelling, UCLBenjamin J. W. Mills, Associate Professor of Biogeochemical Modelling, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1919492022-10-06T04:21:51Z2022-10-06T04:21:51ZOn our wettest days, stormclouds can dump 30 trillion litres of water across Australia<figure><img src="https://images.theconversation.com/files/488424/original/file-20221006-11-q7otx3.jpg?ixlib=rb-1.1.0&rect=589%2C155%2C4586%2C3290&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>This week, rain has drenched almost all of Australia – even the arid interior. The heaviest falls have hit the continent’s southeast, where the huge deluge <a href="https://www.theguardian.com/australia-news/2022/oct/06/nsw-weather-state-braces-for-storms-hail-and-floods-amid-warning-dams-and-rivers-are-full">has just propelled</a> Sydney past its annual rainfall record of 2.2 metres with three months to go until year’s end. </p>
<p>Other parts of the eastern seaboard are bracing for yet more flooding <a href="https://www.abc.net.au/news/2022-10-04/more-flooding-bom-forecast-heavy-falls/101496026">in coming days</a>. So what’s actually causing all this rain? </p>
<p>It all started last week, when unusually warm seas off northwest Australia gave off vast volumes of moist air. This air rose to form huge clouds which, propelled by winds, carried billions of tonnes of water across the continent. </p>
<p>Clouds might look fluffy and insubstantial, but they actually carry truly gigantic quantities of water. Let’s take the nearly 100 millimetres of rain that’s fallen so far this week on Sydney’s inner city – about 25 square kilometres. That’s about <a href="https://water.usgs.gov/edu/activity-howmuchrain-metric.html">2.5 billion litres</a> of water!</p>
<p>On the wettest days, we can accumulate more than 4mm of rain on average across the whole continent. This equates to about <a href="https://water.usgs.gov/edu/activity-howmuchrain-metric.html">30 <em>trillion</em> litres of water</a>. Or, to use the colloquial Australian measurement, 60 Sydney Harbour’s worth (1 Sydharb = 500 gigalitres).</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1577852593677561856"}"></div></p>
<h2>Why do we get rain in the first place?</h2>
<p>Major rain events need two main ingredients: moisture and rising motion in the atmosphere. Most of that moisture comes <a href="https://theconversation.com/the-east-coast-rain-seems-endless-where-on-earth-is-all-the-water-coming-from-178316">from evaporation from oceans</a> but some comes from evaporation from the land, especially when it’s wet.</p>
<p>We get rising motion with surface heating or when air is forced to go up over obstacles (like mountains), or when we have weather systems that cause the air to ascend.</p>
<p>A blob of moist air rising from the surface will expand as it moves higher up in the atmosphere, since air pressure drops quickly with height. This is why balloons eventually pop when they go up in the sky. We can’t see this blob as it rises – it hasn’t turned white and fluffy yet.</p>
<p>The expansion of this moist air blob requires work, so energy has to be found from somewhere. The energy is taken from the movement of air and water molecules within the blob, and since temperature is a measure of the movement of molecules, the air cools.</p>
<p>As the air cools and the water molecules slow down, they stick together more easily, forming droplets. This is the process of condensation and it results in clouds forming. Clouds range in sizes but the biggest cumulonimbus – towering dark storm clouds – can reach more than 10km above the surface. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-wet-spring-what-is-a-negative-indian-ocean-dipole-and-why-does-it-mean-more-rain-for-australias-east-188167">A wet spring: what is a 'negative Indian Ocean Dipole' and why does it mean more rain for Australia's east?</a>
</strong>
</em>
</p>
<hr>
<p>Even small clouds contain a lot of water. A single cloud covering one cubic kilometre would hold around <a href="https://www.usgs.gov/special-topics/water-science-school/science/how-much-does-cloud-weigh">500 tonnes of water</a>. You might wonder why this weight doesn’t bring the whole cloud down immediately. The answer is the moisture is very spread out throughout the cloud, and the air beneath the cloud is denser. </p>
<p>At a certain point, enough water has condensed and come together into droplets for gravity to win out and pull the water to the ground as rain.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/488428/original/file-20221006-22-foygpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="uluru rainy day" src="https://images.theconversation.com/files/488428/original/file-20221006-22-foygpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488428/original/file-20221006-22-foygpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488428/original/file-20221006-22-foygpz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488428/original/file-20221006-22-foygpz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488428/original/file-20221006-22-foygpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488428/original/file-20221006-22-foygpz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488428/original/file-20221006-22-foygpz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">On rare days, rain can fall across a third of Australia - even on the arid interior, as this 2019 photo of Uluru shows.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>So why’s it raining so much right now?</h2>
<p>Right now, we have abundant moisture in the air. The weather is primed to move moisture up through the atmosphere, via low pressure systems and cold fronts moving from west to east.</p>
<p>Low pressure systems mean air pressure is lower than the surrounding areas. Because nature likes to even things out, air at the surface moves in to try and cancel out differences in pressure, although the rotation of the Earth forces the air to spiral in rather than moving directly in. This creates winds which move in towards the low pressure centre and then have to move upwards, carrying moisture with them. That’s why low pressure systems are associated with winds and rain.</p>
<p>Cold fronts are characterised by rising masses of air because they mark divisions between colder and warmer air. The warmer air is less dense and forced to rise over the colder air.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/488425/original/file-20221006-18-ftg0d5.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="bureau of meteorology forecast with lows and highs" src="https://images.theconversation.com/files/488425/original/file-20221006-18-ftg0d5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488425/original/file-20221006-18-ftg0d5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=720&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488425/original/file-20221006-18-ftg0d5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=720&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488425/original/file-20221006-18-ftg0d5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=720&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488425/original/file-20221006-18-ftg0d5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=904&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488425/original/file-20221006-18-ftg0d5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=904&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488425/original/file-20221006-18-ftg0d5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=904&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Low pressure is expected to dominate over eastern Australia with troughs and cold fronts crossing the region and bringing rain.</span>
<span class="attribution"><span class="source">Bureau of Meteorology</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Why is there so much moisture in the air? That’s linked to warmer sea temperatures off northern Australia, which cause more water to evaporate from the sea surface. </p>
<p>La Niña conditions – which we’re experiencing for <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">the third year running</a> – brings cooler seas in the central and eastern Pacific Ocean near the equator and above-average sea surface temperatures in the western Pacific, including around Australia. </p>
<p>But La Niña has company. We also have what’s called <a href="https://theconversation.com/a-wet-spring-what-is-a-negative-indian-ocean-dipole-and-why-does-it-mean-more-rain-for-australias-east-188167">a negative Indian Ocean Dipole</a>, where westerly winds intensify, warming the waters around Indonesia and Australia’s northwest. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/488242/original/file-20221005-16-ot7n77.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/488242/original/file-20221005-16-ot7n77.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488242/original/file-20221005-16-ot7n77.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488242/original/file-20221005-16-ot7n77.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488242/original/file-20221005-16-ot7n77.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488242/original/file-20221005-16-ot7n77.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=458&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488242/original/file-20221005-16-ot7n77.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=458&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488242/original/file-20221005-16-ot7n77.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=458&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">During La Niña, sea surface temperatures are lower than average in the tropical central and eastern Pacific but warmer than normal around Australia.</span>
<span class="attribution"><span class="source">National Oceanic and Atmospheric Administration</span></span>
</figcaption>
</figure>
<p>With these two climate cycles intersecting, we get more and more moisture in the air around Australia. When low pressure systems emerge, they draw the moisture over the continent and cause the air to rise and form heavily-laden clouds. </p>
<p>We can get heavy rains without La Niña, but La Niña loads the dice, making it more likely we get heavier and more widespread rain events. For example, the chance of having a wet day across a third of Australia more than doubles during La Niña compared to neutral conditions – and is more than five times more likely than in an El Niño event.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/488253/original/file-20221005-16-yt3448.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/488253/original/file-20221005-16-yt3448.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488253/original/file-20221005-16-yt3448.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488253/original/file-20221005-16-yt3448.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488253/original/file-20221005-16-yt3448.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488253/original/file-20221005-16-yt3448.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=527&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488253/original/file-20221005-16-yt3448.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=527&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488253/original/file-20221005-16-yt3448.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=527&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Australia has more days with widespread rain during the La Niña (LN) phase of the El Niño-Southern Oscillation (ENSO) climate cycle compared to El Niño (EN) or neutral spring seasons. Histograms of percentage area of Australia experiencing a wet day (greater than 1 mm of rain) by ENSO phase based on Bureau of Meteorology gridded rainfall data.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>During most spring days, only a small percentage of Australia has a day with more than 1mm of rain. But occasionally, we can have days when a third or more of the continent experiences rain – just as we’ve seen this week. </p>
<h2>Rain, rain, go away</h2>
<p>With the <a href="https://theconversation.com/one-of-the-most-extreme-disasters-in-colonial-australian-history-climate-scientists-on-the-floods-and-our-future-risk-178153">devastating floods of February and March</a> still fresh in our memories, most Australians will be hoping for the rain to stop. </p>
<p>But the deluge isn’t done with us yet. </p>
<p>As La Niña continues, we can expect more widespread heavy rain events. And since eastern Australia’s soils are saturated in many areas, there’s a renewed chance of flooding. </p>
<p>By the start of next year, most forecast models predict <a href="http://www.bom.gov.au/climate/enso/index.shtml#tabs=Pacific-Ocean">a weakening La Niña</a>. But it will most likely be a wet summer. Keep your eye on the horizon – and look for the clouds. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/la-nina-3-years-in-a-row-a-climate-scientist-on-what-flood-weary-australians-can-expect-this-summer-190542">La Niña, 3 years in a row: a climate scientist on what flood-weary Australians can expect this summer</a>
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</em>
</p>
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<img src="https://counter.theconversation.com/content/191949/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew King receives funding from the National Environmental Science Program. </span></em></p>On Australia’s rainiest days, more than 30 trillion litres can fall from the skies.Andrew King, Senior Lecturer in Climate Science, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1872342022-09-27T12:29:12Z2022-09-27T12:29:12ZHurricane hunters flew through Ian’s powerful winds to forecast intensity – here’s what happens when the plane plunges into the eyewall of a storm<figure><img src="https://images.theconversation.com/files/474652/original/file-20220718-24-9bzmk2.jpg?ixlib=rb-1.1.0&rect=152%2C8%2C2802%2C1675&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Flying into Hurricane Harvey aboard a a P-3 Hurricane Hunter nicknamed Kermit in 2018.</span> <span class="attribution"><span class="source">Lt. Kevin Doreumus/NOAA</span></span></figcaption></figure><p><em>As Hurricane Ian intensified on its way toward the Florida coast, <a href="https://www.omao.noaa.gov/find/media/video/dropsonde-launch-and-flight-center-tropical-storm-ian-noaa-wp-3d-orion-miss-piggy-september-25-2022-credit-lt-cmdr-kevin-doremus-0">hurricane hunters were in the sky</a> doing something almost unimaginable: flying through the center of the storm. With each pass, the scientists aboard these planes take measurements that satellites can’t and send them to forecasters at the National Hurricane Center.</em></p>
<p><em>Jason Dunion, a <a href="https://scholar.google.com/citations?user=BFiIdhQAAAAJ&hl=en">University of Miami meteorologist</a>, leads the National Oceanic and Atmospheric Administration’s 2022 hurricane field program. He described the technology the team is using to gauge hurricane behavior in real time and the experience aboard a <a href="https://www.omao.noaa.gov/learn/aircraft-operations/aircraft/lockheed-wp-3d-orion">P-3 Orion</a> as it plunges through the eyewall of a hurricane.</em> </p>
<h2>What happens aboard a hurricane hunter when you fly into a storm?</h2>
<p>Basically, we’re take a flying laboratory into the heart of the hurricane, all the way up to Category 5s. While we’re flying, we’re crunching data and sending it to forecasters and climate modelers.</p>
<p>In the <a href="https://www.omao.noaa.gov/learn/aircraft-operations/about/hurricane-hunters">P-3s</a>, we routinely cut through the middle of the storm, right into the eye. Picture <a href="https://scied.ucar.edu/video/dropsonde-animation-noaa">an X pattern</a> – we keep cutting through the storm multiple times during a mission. These might be developing storms, or they might be Category 5s.</p>
<figure class="align-center ">
<img alt="View out the aircraft window of the eyewall." src="https://images.theconversation.com/files/486820/original/file-20220927-18-3ei8of.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/486820/original/file-20220927-18-3ei8of.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/486820/original/file-20220927-18-3ei8of.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/486820/original/file-20220927-18-3ei8of.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/486820/original/file-20220927-18-3ei8of.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/486820/original/file-20220927-18-3ei8of.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/486820/original/file-20220927-18-3ei8of.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">In the eye of Hurricane Teddy in 2020. The eye is the calmest part of the storm, but it’s surrounded by the most intense part: the eyewall.</span>
<span class="attribution"><a class="source" href="https://www.omao.noaa.gov/learn/aircraft-operations/media/images">Lt. Cmdr. Robert Mitchell/NOAA Corps</a></span>
</figcaption>
</figure>
<p>We’re typically flying at an altitude of around 10,000 feet, about a quarter of the way between the ocean surface and the top of the storm. We want to cut through the roughest part of the storm because we’re trying to measure <a href="https://www.unidata.ucar.edu/data/NGCS/lobjects/chp/structure/">the strongest winds</a> for the Hurricane Center. </p>
<h2>That has to be intense. Can you describe what scientists are experiencing on these flights?</h2>
<p>My most intense flight was Dorian in 2019. The storm was near the Bahamas and <a href="https://www.nhc.noaa.gov/data/tcr/AL052019_Dorian.pdf">rapidly intensifying to a very strong Category 5</a> storm, with winds around 185 mph. It felt like being a feather in the wind.</p>
<p>When we were coming through the eyewall of Dorian, it was all seat belts. You can lose a few hundred feet in a couple of seconds if you have a down draft, or you can hit an updraft and gain a few hundred feet in a matter of seconds. It’s a lot like a rollercoaster ride, only you don’t know exactly when the next up or down is coming.</p>
<figure class="align-center ">
<img alt="View of Earth and a large hurricane from a portal on the space station." src="https://images.theconversation.com/files/486822/original/file-20220927-12-shn7r8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/486822/original/file-20220927-12-shn7r8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/486822/original/file-20220927-12-shn7r8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/486822/original/file-20220927-12-shn7r8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/486822/original/file-20220927-12-shn7r8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/486822/original/file-20220927-12-shn7r8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/486822/original/file-20220927-12-shn7r8.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">Hurricane Dorian seen from the International Space Station.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/145559/a-devastating-stall-by-hurricane-dorian">NASA Expedition 60</a></span>
</figcaption>
</figure>
<p>At one point, we had G-forces of 3 to 4 Gs. That’s what <a href="https://www.spaceanswers.com/space-exploration/what-g-force-do-astronauts-experience-during-a-rocket-launch/">astronauts experience</a> during a rocket launch. We can also get <a href="https://twitter.com/TheAstroNick/status/1575179322599493632">zero G for a few seconds</a>, and anything that’s not strapped down will float off.</p>
<p>Even in the rough parts of the storm, scientists like myself are busy on computers working up the data. A technician in the back may have launched a dropsonde from the belly of the plane, and we’re checking the quality of the data and sending it off to modeling centers and the National Hurricane Center.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1575288070223630336"}"></div></p>
<h2>What are you learning about hurricanes from these flights?</h2>
<p>One of our goals is to better understand why storms <a href="https://theconversation.com/the-2020-atlantic-hurricane-season-was-a-record-breaker-and-its-raising-more-concerns-about-climate-change-150495">rapidly intensify</a>. </p>
<p>Rapid intensification is when a storm increases in speed by 35 mph in just a day. That equates to going from Category 1 to a major Category 3 storm in a short period of time. <a href="https://theconversation.com/hurricane-ida-turned-into-a-monster-thanks-to-a-giant-warm-patch-in-the-gulf-of-mexico-heres-what-happened-167029">Ida</a> (2021), <a href="https://www.nhc.noaa.gov/data/tcr/AL052019_Dorian.pdf">Dorian</a> (2019) and <a href="https://www.nhc.noaa.gov/data/tcr/AL142018_Michael.pdf">Michael</a> (2018) are just a few recent hurricanes that rapidly intensified. When that happens near land, it can catch people unprepared, and that gets dangerous fast.</p>
<p>Since rapid intensification can happen in a really short time span, we have to be out there with the hurricane hunters taking measurements while the storm is coming together.</p>
<figure class="align-center ">
<img alt="A pilot at the controls with the storm seen through the window" src="https://images.theconversation.com/files/486826/original/file-20220927-24-tc8raz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/486826/original/file-20220927-24-tc8raz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/486826/original/file-20220927-24-tc8raz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/486826/original/file-20220927-24-tc8raz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/486826/original/file-20220927-24-tc8raz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/486826/original/file-20220927-24-tc8raz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/486826/original/file-20220927-24-tc8raz.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">A hurricane hunter flies through Hurricane Ida in 2021.</span>
<span class="attribution"><a class="source" href="https://www.omao.noaa.gov/learn/aircraft-operations/media/images">Lt. Cmdr. Kevin Doremus/NOAA Corps</a></span>
</figcaption>
</figure>
<p>So far, rapid intensification is <a href="https://www.science.org/content/article/why-scientists-had-trouble-predicting-hurricane-michael-s-rapid-intensification">hard to predict</a>. We might start to see the ingredients quickly coming together: Is the ocean warm to a great depth? Is the atmosphere nice and juicy, with a lot of moisture around the storm? Are the winds favorable? We also look at the inner core: What does the structure of the storm look like, and is it starting to consolidate?</p>
<p>Satellites can offer forecasters a basic view, but we need to get our hurricane hunters into the storm itself to really pick the hurricane apart.</p>
<h2>What does a storm look like when it’s rapidly intensifying?</h2>
<p>Hurricanes like to stand up straight – think of a spinning top. So, one thing we look for is alignment.</p>
<p>A storm that isn’t yet fully together might have low-level circulation, a few kilometers above the ocean, that isn’t lined up with its mid-level circulation 6 or 7 kilometers up. That isn’t a very healthy storm. But a few hours later, we might fly back into the storm and notice that the two centers are more lined up. That’s a sign that it could rapidly intensify.</p>
<p>We also look at the <a href="https://www.aoml.noaa.gov/news/planetary-boundary-layer-parametrization/">boundary layer</a>, the area just above the ocean. Hurricanes breathe: They draw air in at low levels, the air rushes up at the eyewall, and then it vents out at the top of the storm and away from the center. That’s why we get those huge updrafts in the eyewall.</p>
<p>So we might watch our dropsonde or tail doppler radar data for how the winds are flowing at the boundary layer. Is that really moist air rushing in toward the center of the storm? If the boundary layer is deep, the storm can also take a bigger inhale.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/474543/original/file-20220718-18-7tvint.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/474543/original/file-20220718-18-7tvint.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=328&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474543/original/file-20220718-18-7tvint.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=328&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474543/original/file-20220718-18-7tvint.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=328&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474543/original/file-20220718-18-7tvint.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=412&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474543/original/file-20220718-18-7tvint.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=412&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474543/original/file-20220718-18-7tvint.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">Cross-section of a hurricane.</span>
<span class="attribution"><a class="source" href="https://www.weather.gov/jetstream/tc_structure">National Weather Service</a></span>
</figcaption>
</figure>
<p>We also look at the structure. A lot of times the storm looks healthy on satellite, but we’ll get in with the radar and the structure is sloppy or the eye may be filled with clouds, which tells us the storm isn’t quite ready to rapidly intensify. But, during that flight, we might start to see the structure change pretty quickly.</p>
<p>Air in, up and out – the breathing – is a great way to diagnose a storm. If that breathing looks healthy, it can be a good sign of an intensifying storm.</p>
<h2>What instruments do you use to measure and forecast hurricane behavior?</h2>
<p>We need instruments that not only measure the atmosphere but also the ocean. The winds can steer a storm or tear it apart, but the ocean heat and moisture are its fuel.</p>
<p>We use <a href="https://www.eol.ucar.edu/content/what-dropsonde">dropsondes</a> to measure temperature, humidity, pressure and wind speed, and send back data every 15 feet or so all the way to the ocean surface. All of that data goes to the National Hurricane Center and to modeling centers so they can get a better representation of the atmosphere.</p>
<figure class="align-center ">
<img alt="A scientist in a flight suit puts a device into a tube in the bottom of the plane to drop it." src="https://images.theconversation.com/files/486828/original/file-20220927-12-391k29.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/486828/original/file-20220927-12-391k29.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/486828/original/file-20220927-12-391k29.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/486828/original/file-20220927-12-391k29.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/486828/original/file-20220927-12-391k29.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/486828/original/file-20220927-12-391k29.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/486828/original/file-20220927-12-391k29.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A NOAA technician deploys an airborne expendable bathythermograph.</span>
<span class="attribution"><a class="source" href="https://www.omao.noaa.gov/learn/aircraft-operations/media/images">Paul Chang/NOAA</a></span>
</figcaption>
</figure>
<p>One P-3 has a laser – a <a href="https://www.aoml.noaa.gov/wp-content/uploads/2021/04/3_2021HFP_InstrumentDescriptions.pdf">CRL, or compact rotational raman LiDAR</a> – that can measure temperature, humidity and aerosols from the aircraft all the way down to the ocean surface. It can give us a sense of how juicy the atmosphere is, so how conducive it is for feeding a storm. The CRL operates continuously over the entire flight track, so you get this beautiful curtain below the aircraft showing the temperature and humidity.</p>
<p>The planes also have <a href="https://www.aoml.noaa.gov/real-time-doppler-radar/">tail doppler radars</a>, which measure how moisture droplets in the air are blowing to determine how the wind is behaving. That gives us a 3D look at the wind field, like an X-ray of the storm. You can’t get that from a satellite.</p>
<p>We also launch ocean probes call AXBTs – <a href="https://www.aoml.noaa.gov/phod/dhos/axbt.php">aircraft expendable bathythermograph</a> – out ahead of the storm. These probes measure the water temperature down several hundred feet. Typically, a surface temperature of 26.5 degrees Celsius (80 Fahrenheit) and above is favorable for a hurricane, but the depth of that heat is also important. </p>
<p>If you have warm ocean water that’s maybe 85 F at the surface, but just 50 feet down the water is quite a bit colder, the hurricane is going to mix in that cold water pretty quickly and weaken the storm. But deep warm water, <a href="https://theconversation.com/hurricane-ida-turned-into-a-monster-thanks-to-a-giant-warm-patch-in-the-gulf-of-mexico-heres-what-happened-167029">like we find in eddies</a> in the Gulf of Mexico, provides extra energy that can fuel a storm.</p>
<figure class="align-center ">
<img alt="Map showing Ida's track and the depth of heat" src="https://images.theconversation.com/files/476567/original/file-20220728-27592-3cxnt3.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/476567/original/file-20220728-27592-3cxnt3.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=570&fit=crop&dpr=1 600w, https://images.theconversation.com/files/476567/original/file-20220728-27592-3cxnt3.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=570&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/476567/original/file-20220728-27592-3cxnt3.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=570&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/476567/original/file-20220728-27592-3cxnt3.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=716&fit=crop&dpr=1 754w, https://images.theconversation.com/files/476567/original/file-20220728-27592-3cxnt3.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=716&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/476567/original/file-20220728-27592-3cxnt3.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=716&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The depth of ocean heat as Hurricane Ida headed for a warm eddy boundary on Aug. 28, 2021.</span>
<span class="attribution"><span class="source">University of Miami</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>This year, we’re also testing a new technology – small drones that we can launch out of the belly of a P-3. They have about a 7- to 9-foot wingspan and are basically a weather station with wings.</p>
<p>One of these drones dropped in the eye could measuring pressure changes, which indicate whether a storm is getting stronger. If we could drop a drone in the eyewall and have it orbit there, it could measure where the strongest winds are – that’s another important detail for forecasters. We also don’t have a lot of measurements in the boundary layer because it’s not a safe place for a plane to fly. </p>
<h2>You also targeted the Cabo Verde islands off Africa for the first time this year. What are you looking for there?</h2>
<p>The Cabo Verde Islands are in the Atlantic’s hurricane nursery. The seedlings of hurricanes come off Africa, and we’re trying to determine the tipping points for theses disturbances to form into storms.</p>
<p>Over half the named storms we get in the Atlantic come from this nursery, including <a href="https://oceanweatherservices.com/blog/2022/03/20/what-should-we-expect-for-the-2022-hurricane-season/">about 80% of the major hurricanes</a>, so it’s important, even though the disturbances are maybe seven to 10 days ahead of a hurricane forming.</p>
<figure class="align-center ">
<img alt="The plane on a runway at sunrise." src="https://images.theconversation.com/files/486821/original/file-20220927-16-bc6a7c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/486821/original/file-20220927-16-bc6a7c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/486821/original/file-20220927-16-bc6a7c.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/486821/original/file-20220927-16-bc6a7c.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/486821/original/file-20220927-16-bc6a7c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/486821/original/file-20220927-16-bc6a7c.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/486821/original/file-20220927-16-bc6a7c.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">NOAA’s P-3 Orion nicknamed ‘Kermit’ prepares to take off.</span>
<span class="attribution"><a class="source" href="https://www.omao.noaa.gov/learn/aircraft-operations/media/images">Lt. Cmdr Rannenberg/NOAA Corps</a></span>
</figcaption>
</figure>
<p>In Africa, a lot of thunderstorms develop along the Sahara desert’s southern border with the cooler, <a href="https://doi.org/10.1093/acrefore/9780190228620.013.510">moister Sahel region</a> in the summer. The temperature difference can cause ripples to develop in the atmosphere that we call tropical waves. Some of those tropical waves are the precursors for hurricanes. However, the <a href="https://www.aoml.noaa.gov/saharan-air-layer/">Saharan air layer</a> – huge dust storms that come rolling off Africa every three to five days or so – <a href="https://doi.org/10.1175/BAMS-D-20-0212.1">can suppress a hurricane</a>. These storms peak from June to mid-August. After that, tropical disturbances have a better chance of reaching the Caribbean.</p>
<p>At some point not too far in the future, the National Hurricane Center will have to do a seven-day forecast, rather than just five days. We’re figuring out how to improve that early forecasting.</p><img src="https://counter.theconversation.com/content/187234/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jason Dunion receives funding from NOAA, NASA, and the Office of Naval Research.</span></em></p>The meteorologist leading NOAA’s 2022 hurricane field program describes flying through eyewalls and the technology in these airborne labs for tracking rapid intensification in real time.Jason Dunion, Research Meteorologist, University of MiamiLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1859252022-07-05T14:48:45Z2022-07-05T14:48:45ZMethane emissions reach new highs despite pandemic – they are four times more sensitive to climate change than first thought<figure><img src="https://images.theconversation.com/files/472501/original/file-20220705-12-stmhco.jpg?ixlib=rb-1.1.0&rect=0%2C6%2C4042%2C2680&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Wildfires may be slowing the rate at which the atmosphere removes methane.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/fire-jobs-patagonia-argentina-1905100318">Gonzalo Keogan/Shutterstock</a></span></figcaption></figure><p>Eliminating emissions of CO₂ is high up the environmental agenda – but the world should not lose sight of the threat from methane. There has been a disturbing recent surge in atmospheric methane, which is more than <a href="https://www.epa.gov/gmi/importance-methane">25 times more potent</a> as a greenhouse gas over the course of a century than CO₂.</p>
<p>Anthropogenic methane emissions account for roughly 60% of the total and come mainly from agriculture, in particular beef and dairy farms and paddy fields, as well as from oil and gas wells and coal mines, and from sewage treatment plants and landfills. Methane is also emitted naturally from wetlands, sometimes known as marsh or swamp gas, which makes up the remaining 40%.</p>
<p>The latest <a href="https://www.ipcc.ch/report/ar6/wg1/figures/summary-for-policymakers/figure-spm-2/">report</a> from the Intergovernmental Panel on Climate Change (IPCC) showed that methane is responsible for around one-third of the estimated 1.5°C of global warming (sulphur dioxide emissions have contributed around <a href="https://www.ipcc.ch/report/ar6/wg1/figures/summary-for-policymakers/figure-spm-2/">0.5°C of cooling</a>, so total warming is now just over 1°C since pre-industrial times), with around half due to CO₂. </p>
<p>Scientists have puzzled over the fact that methane emissions have not only grown rapidly since 2007, but have been increasing at an even faster rate in just the past two years. Despite the pandemic, when lockdowns and stuttering industrial activity might have dampened many sources, methane emissions increased by the <a href="https://gml.noaa.gov/ccgg/trends_ch4/">highest amount on record</a> in 2021. The amount of methane in the atmosphere just <a href="https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Sentinel-5P/Methane_levels_surged_in_2020_despite_lockdowns">keeps on growing</a>.</p>
<figure class="align-center ">
<img alt="An oil and gas rig on land silhouetted against the setting sun." src="https://images.theconversation.com/files/472499/original/file-20220705-17-duqjrj.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5660%2C3770&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472499/original/file-20220705-17-duqjrj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472499/original/file-20220705-17-duqjrj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472499/original/file-20220705-17-duqjrj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472499/original/file-20220705-17-duqjrj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472499/original/file-20220705-17-duqjrj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472499/original/file-20220705-17-duqjrj.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">Methane leaks from oil and gas extraction sites.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/abandoned-oil-gas-rig-profiled-on-550109887">Calin Tatu/Shutterstock</a></span>
</figcaption>
</figure>
<p>The past four decades of <a href="https://psl.noaa.gov">temperature and rain data</a> – which indicate that the Earth is not only delivering more methane to the atmosphere, but removing less of it – may hold the answer. In <a href="https://www.nature.com/articles/s41467-022-31345-w">a new study</a>, my colleague Chin-Hsien Cheng and I showed that climate change has increased the rate at which methane accumulates in the atmosphere, trapping more heat and causing the Earth to warm more and faster and, potentially, releasing more methane in a vicious cycle. This indicates that climate change has an effect on methane – ultimately increasing the amount of it in the atmosphere – that is up to four times greater than estimates in the <a href="https://theconversation.com/mass-starvation-extinctions-disasters-the-new-ipcc-reports-grim-predictions-and-why-adaptation-efforts-are-falling-behind-176693">latest IPCC report</a>, which was only published in February 2022.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/methane-in-the-atmosphere-is-at-an-all-time-high-heres-what-it-means-for-climate-change-174908">Methane in the atmosphere is at an all-time high – here's what it means for climate change</a>
</strong>
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<h2>Wildfires gobbling up methane scrubbers</h2>
<p>To explain why atmospheric methane keeps growing, we need to understand how the input and removal of methane to and from the atmosphere is balanced. Even if inputs from gas leaks and coal extraction fall, as may be expected during an economic slowdown, the total annual increase can still rise if the removal rate decreases by even more, or becomes less efficient. </p>
<p>Our study suggests increasing methane emissions may be due to unexpected and complex linkages. For example, wildfires, which are becoming <a href="https://theconversation.com/climate-change-wildfire-risk-has-grown-nearly-everywhere-but-we-can-still-influence-where-and-how-fires-strike-185465">more common</a> as the world warms, may increase atmospheric methane – not necessarily by adding more, but by slowing down how it is removed from the atmosphere. </p>
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<strong>
Read more:
<a href="https://theconversation.com/climate-change-wildfire-risk-has-grown-nearly-everywhere-but-we-can-still-influence-where-and-how-fires-strike-185465">Climate change: wildfire risk has grown nearly everywhere – but we can still influence where and how fires strike</a>
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<p>The hydroxyl radical, a powerful oxidising agent found in air which is composed of an oxygen and hydrogen atom (•OH), has been called the detergent of the atmosphere because it cleanses the air of harmful trace gases. Methane is removed by an oxidation reaction with hydroxyl radicals, and this reaction is by far the most important way that methane disappears from the atmosphere. </p>
<p>Wildfires burn carbon-rich wood and plant matter and typically generate carbon monoxide (CO) in the smoke. This gas reacts strongly with hydroxyl, becoming oxidised to form CO₂. On average, a carbon monoxide molecule remains in the atmosphere for about three months before it is oxidised, while methane persists for about a decade. So, plumes of carbon monoxide from wildfires swiftly use up the hydroxyl “detergent”, leaving less to react with and remove methane.</p>
<figure class="align-center ">
<img alt="A satellite image of a forest fire." src="https://images.theconversation.com/files/472502/original/file-20220705-20-yzoey2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472502/original/file-20220705-20-yzoey2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472502/original/file-20220705-20-yzoey2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472502/original/file-20220705-20-yzoey2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472502/original/file-20220705-20-yzoey2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472502/original/file-20220705-20-yzoey2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472502/original/file-20220705-20-yzoey2.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">Fires consume the atmosphere’s methane ‘detergent’.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/forest-fire-space-elements-this-image-1987708634">Artsiom P/Shutterstock</a></span>
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</figure>
<p>These results are shocking, as they highlight one way the effects of climate change on the Earth system have been underestimated. The world cannot ignore the worrying sensitivity of methane emissions to increasing global temperatures given the strength of methane as a greenhouse gas.</p>
<p>Methane emissions must not go unchecked. But which sources do we have the greatest ability to reduce? Reducing how much methane seeps from landfills and fossil fuel extraction is important. Cutting back on how much beef and dairy products you eat will <a href="https://theconversation.com/the-uk-urgently-needs-to-cut-its-methane-emissions-by-2030-cows-and-sheep-hold-the-key-to-success-185621">certainly help too</a>. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-uk-urgently-needs-to-cut-its-methane-emissions-by-2030-cows-and-sheep-hold-the-key-to-success-185621">The UK urgently needs to cut its methane emissions by 2030: cows and sheep hold the key to success</a>
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<p>But changes in farming practises, such as banning the burning of vegetation, adjusting what cattle are fed and regularly draining rice paddies have <a href="https://www.mckinsey.com/business-functions/sustainability/our-insights/curbing-methane-emissions-how-five-industries-can-counter-a-major-climate-threat">all been identified</a> as routes to lowering how much methane reaches the atmosphere.</p>
<p>But to protect the atmopshere’s natural ability to remove methane, the world must redouble efforts to slow climate change and its assault on the natural world.</p>
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<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">
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<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
<br><em><a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeTop">Get a weekly roundup in your inbox instead.</a> Every Wednesday, The Conversation’s environment editor writes Imagine, a short email that goes a little deeper into just one climate issue. <a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeBottom">Join the 10,000+ readers who’ve subscribed so far.</a></em></p>
<hr><img src="https://counter.theconversation.com/content/185925/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Redfern receives funding from the Nanyang Technological University, Singapore, and A*STAR, Singapore. </span></em></p>Climate change’s assault on the natural world may explain mystery methane emission surge.Simon Redfern, Professor in Earth Sciences, Nanyang Technological University, Singapore, and Emeritus Professor of Mineral Physics, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1852702022-06-23T14:22:16Z2022-06-23T14:22:16ZCosmic dust from Venus is inspiring new air pollution-busting technology<figure><img src="https://images.theconversation.com/files/470562/original/file-20220623-52339-jw2nyz.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6000%2C3089&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Venus has a thick, toxic atmosphere filled with carbon dioxide.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/thick-clouds-over-planet-venus-3d-1313293106">Jurik Peter/Shutterstock</a></span></figcaption></figure><p>Reducing carbon emissions from roads, railways and shipping requires implementing a range of solutions simultaneously. As far as cars are concerned, cutting the number of journeys altogether (by making it easier for people to walk and cycle and improving public transport), changing the fuel in vehicles and making the most of those vehicles already on the road must all play a part. None of these solutions are sufficient on their own.</p>
<p>In 2030, the sale of new diesel and petrol passenger cars <a href="https://www.gov.uk/government/news/government-takes-historic-step-towards-net-zero-with-end-of-sale-of-new-petrol-and-diesel-cars-by-2030">will be outlawed</a> in the UK. The future of passenger motoring will be electric. But recent <a href="https://theconversation.com/electric-car-supplies-are-running-out-and-could-drastically-slow-down-the-journey-to-net-zero-182787">problems supplying parts</a> and the <a href="https://academic.oup.com/cje/article/44/4/953/5859377?login=true">high carbon cost of manufacturing</a> electric vehicles could delay the climate benefits of this transition.</p>
<p>To make best use of existing petrol and diesel burning vehicles – and the carbon that was invested in creating them – drivers and manufacturers can reduce the emissions of a family of compounds called nitrogen oxides, which are <a href="https://climatenexus.org/wp-content/uploads/2015/09/HumanHealthEffectsofAirPollutionKampaandCastanas.pdf">linked to respiratory diseases</a>, through better treatment of exhaust fumes. This way, the communities most blighted by air pollution can at least be protected before harmful vehicle emissions are finally eradicated.</p>
<p>My research team is developing a new generation of catalytic converters – the devices fitted to exhaust pipes to reduce the release of toxic gases. Inspired by chemistry observed on the surface of extremely hot planets such as Venus, we have <a href="https://doi.org/10.1016/j.jastp.2016.08.011">produced a synthetic material</a> that could improve air quality. </p>
<h2>From Venus to vehicle exhausts</h2>
<p>The Sun’s light destroys carbon dioxide (CO₂) in the atmospheres of planets, producing carbon monoxide (CO). Not fast enough to avert climate change, but enough that atmospheres like Venus should contain far more CO than we observe there.</p>
<p>Our group studies the effects of meteoric material (dust arriving from space) in atmospheres. An iron silicate powder we made which replicates this dust <a href="https://doi.org/10.1016/j.icarus.2017.06.005">can speed up</a> the conversion of CO to CO₂. This is what the first catalytic converters in cars were designed to do, since CO is a toxic gas. </p>
<figure class="align-center ">
<img alt="A series of metal chambers and pipes on the underside of a car." src="https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.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">Catalytic converters turn toxic gases generated in petrol and diesel engines into safer alternatives.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/catalytic-converter-exhaust-system-modern-car-1651656655">Ulianenko Dmitrii/Shutterstock</a></span>
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<p>That got us thinking about whether this material could help with other problems, such as nitrogen oxide pollution, which <a href="https://www.theguardian.com/environment/2021/mar/04/uk-has-broken-air-pollution-limits-for-a-decade-eu-court-finds">exceeds legal limits</a> in the air of many UK cities. Poor air quality from vehicle exhausts costs <a href="https://www.eea.europa.eu/publications/air-quality-in-europe-2021/health-impacts-of-air-pollution">tens of thousands of lives annually</a>. </p>
<p>We’ve found that not only can the powder <a href="https://www.sciencedirect.com/science/article/abs/pii/S138589472103391X">simultaneously clean up</a> CO and nitrogen oxide emissions, but it can convert nitrogen dioxide (NO₂, a harmful gas which is specifically regulated) to harmless molecular nitrogen (N₂) and water at room temperature.</p>
<p>Catalysts for processing nitrogen oxide (NOx) emissions installed in modern diesel vehicles only work at exhaust temperatures above 150°C. Even if your car uses an additive fluid to reduce nitrogen oxide emissions, it’s unlikely to work while driving slowly when the exhaust is cooler. This is when vehicles emit the most NO₂ – often in traffic jams where the most polluted air can accumulate.</p>
<p>When the electricity grid is decarbonised and sufficiently robust to charge millions of electric vehicles, catalytic converters capable of removing nitrogen oxides may still be important. For example, the natural gas fuel in industrial furnaces <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/824592/industrial-fuel-switching.pdf">is likely to be replaced</a> with hydrogen. </p>
<p>Unlike buses and cars running on hydrogen, which produce energy via a reaction in a fuel cell, larger applications such as furnaces in steelworks will burn hydrogen fuel directly. This high-temperature combustion will convert molecular nitrogen in the air to nitrogen oxide pollution, which will need to be removed.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/hydrogen-where-is-low-carbon-fuel-most-useful-for-decarbonisation-147696">Hydrogen: where is low-carbon fuel most useful for decarbonisation?</a>
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<p>That’s why we’re excited to be developing a prototype emissions converter that can work in most situations, with the potential to radically reduce toxic emissions from combustion engines and other sources in the future.</p><img src="https://counter.theconversation.com/content/185270/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexander James is a listed inventor on the patent protecting intellectual property on LowCat. He and his team received funding from the Science and Technology Funding Council.</span></em></p>New catalytic converters can remove toxic chemicals from the exhaust fumes of combustion-engine cars.Alexander James, Research Fellow in Atmospheric Chemistry, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1855692022-06-22T12:35:23Z2022-06-22T12:35:23ZWhat is a heat dome? An atmospheric scientist explains the weather phenomenon baking Texas and the Southwest<figure><img src="https://images.theconversation.com/files/534155/original/file-20230626-27-2k6wiq.png?ixlib=rb-1.1.0&rect=0%2C143%2C811%2C564&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A heat dome began sizzling Texas and its neighbors in mid-June 2023, with warm nights providing little relief.</span> <span class="attribution"><a class="source" href="https://graphical.mdl.nws.noaa.gov/sectors/sectorDay.php?view=public&sector=conus&element=T">National Weather Service</a></span></figcaption></figure><p>A heat dome occurs when a persistent region of high pressure traps heat over an area. The heat dome can stretch over several states and linger for days to weeks, leaving the people, crops and animals below to suffer through stagnant, hot air that can feel like an oven.</p>
<p>Typically, heat domes are tied to the behavior of <a href="https://www.youtube.com/watch?v=o203JXAnSA0">the jet stream</a>, a band of fast winds high in the atmosphere that generally runs west to east. </p>
<p>Normally, the jet stream has a <a href="https://www.weather.gov/jetstream/jet">wavelike pattern, meandering</a> north and then south and then north again. When these meanders in the jet stream become bigger, they move slower and can become stationary. That’s when heat domes can occur. </p>
<figure class="align-center ">
<img alt="Map of U.S. with a bubble over the Midwest showing arrows moving, with the ridge air sinking" src="https://images.theconversation.com/files/470123/original/file-20220621-23-no5s1r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/470123/original/file-20220621-23-no5s1r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=329&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470123/original/file-20220621-23-no5s1r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=329&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470123/original/file-20220621-23-no5s1r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=329&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470123/original/file-20220621-23-no5s1r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=413&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470123/original/file-20220621-23-no5s1r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=413&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470123/original/file-20220621-23-no5s1r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=413&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Heat domes involve high-pressure areas that trap and heat up the air below.</span>
<span class="attribution"><a class="source" href="https://oceanservice.noaa.gov/facts/heat-dome.html">NOAA</a></span>
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<p>When the jet stream swings far to the north, air piles up and sinks. The <a href="https://glossary.ametsoc.org/wiki/Heat_dome">air warms as it sinks</a>, and the sinking air also keeps skies clear since it lowers humidity. That allows the sun to create hotter and hotter conditions near the ground. </p>
<p>If the air near the ground passes over mountains and descends, it can <a href="https://blog.weather.us/downsloping/">warm even more</a>. This downslope warming played a large role in the extremely hot temperatures in the Pacific Northwest during a <a href="https://en.wikipedia.org/wiki/2021_Western_North_America_heat_wave">heat dome event in 2021</a>, when Washington set a state record with 120 degrees Fahrenheit (49 Celsius), and temperatures reached 121 F in British Columbia in Canada, surpassing the previous Canadian record by 8 degrees F (4 C).</p>
<h2>The human impact</h2>
<p>Heat domes normally persist for several days in any one location, but they can last longer. They can also move, influencing neighboring areas over a week or two. The heat dome that started in Texas and Mexico in <a href="https://origin.wpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=pmdspd">June 2023</a> spread into the Southwest in July, with little relief in sight.</p>
<p>On rare occasions, the heat dome can be more persistent. That happened in the <a href="https://www.hsdl.org/c/tl/1980-us-heat-wave/">southern Plains in 1980</a>, when as many as 10,000 people died during weeks of high summer heat. It also happened over much of the United States <a href="https://doi.org/10.1038/s41558-020-0771-7">during the Dust Bowl years</a> of the 1930s.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1677793035487444992"}"></div></p>
<p>A heat dome can have serious impacts on people, because the stagnant weather pattern that allows it to exist usually results in weak winds and an increase in humidity. Both factors make the heat feel worse – <a href="https://theconversation.com/knowing-how-heat-and-humidity-affect-your-body-can-help-you-stay-safe-during-heat-waves-163700">and become more dangerous</a> – because the human body is not cooled as much by sweating.</p>
<p>The <a href="https://www.weather.gov/ama/heatindex">heat index</a>, a combination of heat and humidity, is often used to convey this danger by indicating what the temperature will feel like to most people. The high humidity also reduces the amount of cooling at night. Warm nights can leave people without air conditioners unable to cool off, which increases the risk of heat illnesses and deaths. With global warming, <a href="https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature">temperatures are already higher</a>, too.</p>
<p>One of the worst recent examples of the impacts from a heat dome with high temperatures and humidity in the U.S. occurred <a href="https://www.weather.gov/lot/1995_heatwave_anniversary">in the summer of 1995</a>, when an estimated <a href="https://www.chicagomag.com/Chicago-Magazine/July-2015/1995-Chicago-heat-wave/">739 people died in the Chicago area</a> over five days.</p>
<p><em>This article was updated July 10, 2023, with the heat dome in the Southwest.</em></p><img src="https://counter.theconversation.com/content/185569/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William Gallus receives funding from the National Science Foundation. </span></em></p>Heat domes are a dangerous part of summer weather.William Gallus, Professor of Atmospheric Science, Iowa State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1840282022-06-06T12:51:07Z2022-06-06T12:51:07ZWhy does the Moon look close some nights and far away on other nights?<figure><img src="https://images.theconversation.com/files/466990/original/file-20220603-24-gaj6i5.jpg?ixlib=rb-1.1.0&rect=7%2C5%2C688%2C337&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Moon often looks enormous when it first rises because of what is known as the Moon illusion.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Harvest_moon.jpg#/media/File:Harvest_moon.jpg">Roadcrusher/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">
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<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>Why does the moon look close some nights and far away on other nights? – Gabriel H., age 7, Providence, Rhode Island</p>
</blockquote>
<hr>
<p>Some nights the Moon seems really close and bigger than usual.</p>
<p>One summer evening when I was a child, I remember being mystified and then startled at a huge round shape slowly creeping up behind my friend Nancy’s house, which sat on a hill on the other side of our village.</p>
<p>At some point I suddenly realized it was the Moon, and I ran yelling through the garden to tell my dad and get him to come and see. It was bigger than a house, deep orange in color and surely of great significance. My dad muttered something about perspective and went back to gardening or playing the piano.</p>
<p>Unconvinced, I kept watching the Moon. Later, once the Moon had risen higher in the sky, it was back to looking like its usual self.</p>
<p>Welcome to what astronomers like me call <a href="https://solarsystem.nasa.gov/news/1191/the-moon-illusion-why-does-the-moon-look-so-big-sometimes/">the Moon illusion</a>. </p>
<p>It can be hard to believe that it is just an illusion when the Moon looks huge, but it is true. You can actually test the illusion yourself and even capture it with a camera. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/466992/original/file-20220603-12-5tpa8e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An image of a city skyline with two images of the Moon – one higher in the sky and one near a distant horizon." src="https://images.theconversation.com/files/466992/original/file-20220603-12-5tpa8e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466992/original/file-20220603-12-5tpa8e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466992/original/file-20220603-12-5tpa8e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466992/original/file-20220603-12-5tpa8e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466992/original/file-20220603-12-5tpa8e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466992/original/file-20220603-12-5tpa8e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466992/original/file-20220603-12-5tpa8e.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">The two Moons in this edited image are the same size, but the one near the horizon on the right side looks bigger because of the Moon illusion.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Moon_illusion_on_city.svg#/media/File:Moon_illusion_on_city.svg">Heeheemalu/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>A trick of the mind</h2>
<p>Astronomers have discussed the Moon illusion for centuries, and there are some facts they all agree on. </p>
<p>People mainly notice the Moon looking bigger and closer when it is full and near the horizon. This is because your mind judges how big or small an object like the Moon is <a href="https://doi.org/10.1073/pnas.97.1.500">by comparing it with other, familiar things</a>. </p>
<p>Imagine you are standing outside close to your house. Your house will look big, and if the Moon rises next to it, the Moon will look normal. If you look at a house from far away, though, the house looks very small. </p>
<p>The illusion comes from the fact that the Moon is so far away that no matter where you are on Earth, the Moon always looks the same size. It is actually the things your mind compares the Moon with – a house, a mountain or anything else – that look bigger or smaller depending on how far away from them you are. So when the Moon rises next to a distant house or a faraway mountain, the Moon looks enormous. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/466994/original/file-20220603-14205-cvld76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An image showing two circles of the same size surrounded by other circles that are larger or smaller." src="https://images.theconversation.com/files/466994/original/file-20220603-14205-cvld76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466994/original/file-20220603-14205-cvld76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=369&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466994/original/file-20220603-14205-cvld76.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=369&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466994/original/file-20220603-14205-cvld76.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=369&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466994/original/file-20220603-14205-cvld76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=464&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466994/original/file-20220603-14205-cvld76.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=464&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466994/original/file-20220603-14205-cvld76.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=464&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 two orange circles in the center of the gray circles are the same size, but they look different because of the different sizes of the circles surrounding them.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Mond-vergleich.svg#/media/File:Mond-vergleich.svg">Phrood/Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>Photographers use this trick to take spectacular images of distant objects with the Moon behind them. People often experience the Moon illusion on vacations when they go to wide-open spaces. This may be why big Moons become powerful memories of happy times. </p>
<h2>Atmospheric zoom and changing orbits</h2>
<p>There are several convincing-sounding but wrong explanations for the Moon illusion. Most are grounded in some truth, so they persist. </p>
<p>First is the idea that the atmosphere acts like a lens and magnifies the Moon. When the Moon is near the horizon, its light has to travel though much more of the Earth’s atmosphere than when the Moon is directly overhead. It’s true that all that air <a href="https://doi.org/10.1007/BF02521844">acts like a giant prism and bends the rays of light</a>, distorting the color and shape of the Moon. But it does not act like a magnifying glass.</p>
<p>Next is the idea that on some nights the Moon really is closer. The Moon’s orbit is not perfectly circular – it’s more like an oval shape, called an ellipse – so the Moon does get nearer and farther away over the course of a month. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/466995/original/file-20220603-24-oj5qmw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An image showing the elliptical orbit of the Moon." src="https://images.theconversation.com/files/466995/original/file-20220603-24-oj5qmw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466995/original/file-20220603-24-oj5qmw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=522&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466995/original/file-20220603-24-oj5qmw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=522&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466995/original/file-20220603-24-oj5qmw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=522&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466995/original/file-20220603-24-oj5qmw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=655&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466995/original/file-20220603-24-oj5qmw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=655&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466995/original/file-20220603-24-oj5qmw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=655&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 orbit of the Moon makes it so that it is not always the same distance from Earth – as shown in the is exaggerated image – but the difference in distance is not enough to account for the Moon illusion.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Moon_apsidal_precession.png#/media/File:Moon_apsidal_precession.png">Rfassbind / Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>When the close part of the orbit coincides with a full moon, it’s called a <a href="https://theconversation.com/supermoon-red-blood-lunar-eclipse-its-all-happening-at-once-but-what-does-that-mean-161262">supermoon</a>. But when the Moon is closest to Earth, it is only about 12% to 15% closer than when it is farthest from Earth – too small a difference to explain the Moon illusion. It is hard to notice a 15% difference in size by just looking at the Moon alone in the sky. </p>
<h2>Testing the illusion</h2>
<p>It’s easy to test the Moon illusion, and you can do it yourself. Next time you see the Moon looking huge and closer than usual, hold out your hand with a straight arm. Then close one eye and see which finger tip just barely covers the Moon – for me, it’s my pinkie finger. Wait a little while until the Moon moves higher into the sky and try the experiment again. The Moon may look smaller, but your same finger will cover it just the same.</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/184028/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Silas Laycock works at The University of Massachusetts Lowell. He receives funding from NASA and the NSF. He is affiliated with the American Astronomical Society, and the Lowell Center for Space Science and Technology. </span></em></p>The Moon illusion is what makes the Moon look giant when you see it rising over a distant horizon. An astronomer explains what causes this awe-inspiring trick of the mind.Silas Laycock, Professor of Astronomy, UMass LowellLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1782952022-03-29T12:36:30Z2022-03-29T12:36:30ZHow fast can we stop Earth from warming?<figure><img src="https://images.theconversation.com/files/453654/original/file-20220322-21-4h6qc0.jpg?ixlib=rb-1.1.0&rect=17%2C180%2C3864%2C2403&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The ocean retains heat for much longer than land does. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/crowded-sunset-silhouette-royalty-free-image/1179557108">Aliraza Khatri's Photography via Getty Images</a></span></figcaption></figure><p>Global warming doesn’t stop on a dime. If people everywhere stopped burning fossil fuels tomorrow, stored heat would still continue to warm the atmosphere.</p>
<p>Picture how a radiator heats a home. Water is heated by a boiler, and the hot water circulates through pipes and radiators in the house. The radiators warm up and heat the air in the room. Even after the boiler is turned off, the already heated water is still circulating through the system, heating the house. The radiators are, in fact, cooling down, but their stored heat is still warming the air in the room.</p>
<p>This is known as <a href="https://doi.org/10.1038/s41558-020-00955-x">committed warming</a>. Earth similarly has ways of storing and releasing heat. </p>
<p>Emerging research is refining scientists’ understanding of how Earth’s committed warming will affect the climate. Where we once thought it would take 40 years or longer for global surface air temperature to peak once humans stopped heating up the planet, research now suggests <a href="https://doi.org/10.1088/1748-9326/9/12/124002">temperature could peak in closer to 10 years</a>.</p>
<p>But that doesn’t mean the planet returns to its preindustrial climate or that we avoid disruptive effects such as sea level rise.</p>
<p>I am a professor of climate science, and my research and teaching focus on the usability of climate knowledge by practitioners such as urban planners, public health professionals and policymakers. Let’s take a look at the bigger picture.</p>
<h2>How understanding of peak warming has changed</h2>
<p>Historically, the <a href="https://www.carbonbrief.org/timeline-history-climate-modelling">first climate models</a> represented only the atmosphere and were greatly simplified. Over the years, scientists <a href="https://celebrating200years.noaa.gov/breakthroughs/climate_model/welcome.html">added oceans</a>, land, ice sheets, chemistry and biology.</p>
<p>Today’s models can more explicitly represent the behavior of greenhouse gases, especially carbon dioxide. That allows scientists to better separate heating due to carbon dioxide in the atmosphere from the role of heat stored in the ocean.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/_WUNMzC98jI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Why global warming is ocean warming.</span></figcaption>
</figure>
<p>Thinking about our radiator analogy, increasing concentrations of greenhouse gases in Earth’s atmosphere keep the boiler on – holding energy near the surface and raising the temperature. Heat accumulates and is stored, <a href="https://climate.nasa.gov/vital-signs/ocean-heat/">mostly in the oceans</a>, which take on the role of the radiators. The heat is distributed around the world through weather and oceanic currents.</p>
<p>The <a href="https://bg.copernicus.org/articles/17/2987/2020/">current understanding</a> is that if all of the additional heating to the planet caused by humans was eliminated, a plausible outcome is that Earth would reach <a href="https://www.carbonbrief.org/explainer-will-global-warming-stop-as-soon-as-net-zero-emissions-are-reached">a global surface air temperature peak in closer to 10 years than 40</a>. The previous estimate of 40 or more years has been widely used over the years, <a href="https://theconversation.com/what-would-happen-to-the-climate-if-we-stopped-emitting-greenhouse-gases-today-35011">including by me</a>.</p>
<p>It is important to note that this is only the peak, when the temperature starts to stabilize – not the onset of rapid cooling or a reversal of climate change.</p>
<p>I believe there is <a href="https://bg.copernicus.org/articles/17/2987/2020/">enough uncertainty to justify caution</a> about exaggerating the significance of the new research’s results. The authors applied the concept of peak warming to global surface air temperature. Global surface air temperature is, metaphorically, the temperature in the “room,” and is not the best measure of climate change. The concept of instantly cutting off human-caused heating is also idealized and entirely unrealistic – doing that would involve much more than just ending fossil fuel use, including widespread changes to agriculture – and it only helps illustrate how parts of the climate might behave. </p>
<p>Even if the air temperature were to peak and stabilize, “<a href="https://youtu.be/AT5jdqHUeKM">committed ice melting</a>,” “committed sea level rise” and numerous other land and biological trends would continue to evolve from the accumulated heat. Some of these could, in fact, cause a <a href="https://doi.org/10.1130/G48580.1">release of carbon dioxide and methane</a>, especially from the Arctic and other high-latitude reservoirs that are <a href="https://yaleclimateconnections.org/2018/02/the-permafrost-bomb-is-ticking/">currently frozen</a>. </p>
<p>For these reasons and others, it is important to consider the how far into the future studies like this one look.</p>
<h2>Oceans in the future</h2>
<p>Oceans will continue to store heat and exchange it with the atmosphere. Even if emissions stopped, the excess heat that has been accumulating in the ocean since preindustrial times would influence the climate for another 100 years or more.</p>
<p>Because the ocean is dynamic, it has currents, and it will not simply diffuse its excess heat back into the atmosphere. There will be ups and downs as the temperature adjusts.</p>
<p>The oceans also influence the amount of carbon dioxide in the atmosphere, because carbon dioxide is both absorbed and emitted by the oceans. <a href="https://www.ncei.noaa.gov/products/paleoclimatology/paleo-perspectives/global-warming">Paleoclimate studies show</a> large changes in carbon dioxide and temperature in the past, with the oceans playing an important role.</p>
<figure class="align-center ">
<img alt="Chart showing ocean heating increasing fastest and going to greater depths over time." src="https://images.theconversation.com/files/453639/original/file-20220322-24-c0zec5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/453639/original/file-20220322-24-c0zec5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=432&fit=crop&dpr=1 600w, https://images.theconversation.com/files/453639/original/file-20220322-24-c0zec5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=432&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/453639/original/file-20220322-24-c0zec5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=432&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/453639/original/file-20220322-24-c0zec5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=543&fit=crop&dpr=1 754w, https://images.theconversation.com/files/453639/original/file-20220322-24-c0zec5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=543&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/453639/original/file-20220322-24-c0zec5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=543&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The chart shows how excess heat – thermal energy – has built up in ocean, land, ice and atmosphere since 1960 and moved to greater ocean depths with time. TOA CERES refers to the top of the atmosphere.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Earth%27s_Heat_Accumulation.png">Karina von Schuckman, LiJing Cheng, Matthew D. Palmer, James Hansen, Caterina Tassone, et al.</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Countries aren’t close to ending fossil fuel use</h2>
<p>The possibility that a policy intervention might have measurable impacts in <a href="https://doi.org/10.1088/1748-9326/9/12/124002">10 years</a> rather than several decades could motivate more aggressive efforts to remove carbon dioxide from the atmosphere. It would be very satisfying to see policy interventions having present rather than notional future benefits.</p>
<p>[<em>Over 150,000 readers rely on The Conversation’s newsletters to understand the world.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-150ksignup">Sign up today</a>.]</p>
<p>However, today, countries aren’t anywhere close to ending their fossil fuel use. Instead, all of the <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">evidence points to humanity experiencing rapid global warming</a> in the coming decades. </p>
<p>Our most robust finding is that the less carbon dioxide humans release, the better off humanity will be. Committed warming and human behavior point to a need to accelerate efforts both to reduce greenhouse gas emissions and to adapt to this warming planet now, rather than simply talking about how much needs to happen in the future.</p><img src="https://counter.theconversation.com/content/178295/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Rood receives funding from the National Oceanographic and Atmospheric Administration and the National Science Foundation. He is a co-principal investigator at the Great Lakes Integrated Sciences and Assessment Center at the University of Michigan.</span></em></p>If fossil fuel burning stopped, emerging research suggests air temperatures could level off sooner than expected. But that doesn’t mean the damage stops.Richard B. (Ricky) Rood, Professor of Climate and Space Sciences and Engineering, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1767112022-02-27T00:00:45Z2022-02-27T00:00:45ZLike rivers in the sky: the weather system bringing floods to Queensland will become more likely under climate change<p>The severe floods in southeast Queensland this week have forced hundreds of residents to flee the town of Gympie and have cut off major roads, after intense rain battered the state for several days. The rain is expected to continue today, and travel south into New South Wales.</p>
<p>We research a weather system called “atmospheric rivers”, which is causing this inundation. Indeed, atmospheric rivers triggered many of the world’s floods in 2021, including the devastating floods across eastern Australia <a href="https://www.smh.com.au/politics/nsw/la-nina-s-final-fury-20210427-p57mvj.html">in March</a> which killed two people and saw 24,000 evacuate.</p>
<p>Our recently published <a href="https://journals.ametsoc.org/view/journals/clim/aop/JCLI-D-21-0606.1/JCLI-D-21-0606.1.xml">research</a> was the first to quantify the impacts these weather systems have in Australia, and <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021GL095335">another study</a> we published in November looked closely at the floods in March last year</p>
<p>We found while atmospheric rivers bring much-needed rainfall to the agriculturally significant Murray-Darling Basin, their potential to bring devastating floods will become more likely in a warmer world under climate change.</p>
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<h2>What are atmospheric rivers?</h2>
<p>Atmospheric rivers are like highways of water vapour between the tropics and poles, located in the first one to three kilometres of the atmosphere. They are responsible for <a href="https://journals.ametsoc.org/view/journals/mwre/126/3/1520-0493_1998_126_0725_apafmf_2.0.co_2.xml">about 90%</a> of the water vapour moving from north to south of the planet, despite covering only 10% of the globe.</p>
<p>When atmospheric rivers crash into mountain ranges or interact with cold fronts, they rain out this water with potentially disastrous impacts. Mountains and fronts lift the water vapour up in the atmosphere where it cools and condenses into giant, liquid-forming bands of clouds. Intense thunderstorms can also form within atmospheric rivers.</p>
<figure class="align-center ">
<img alt="Map of the world with water vapour shown" src="https://images.theconversation.com/files/445656/original/file-20220210-25-icld7u.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/445656/original/file-20220210-25-icld7u.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=282&fit=crop&dpr=1 600w, https://images.theconversation.com/files/445656/original/file-20220210-25-icld7u.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=282&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/445656/original/file-20220210-25-icld7u.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=282&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/445656/original/file-20220210-25-icld7u.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=354&fit=crop&dpr=1 754w, https://images.theconversation.com/files/445656/original/file-20220210-25-icld7u.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=354&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/445656/original/file-20220210-25-icld7u.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=354&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A snapshot of water vapour in the atmosphere. Atmospheric rivers are the narrow streamers branching off the equator.</span>
<span class="attribution"><span class="source">Space Science and Engineering Center, University of Wisconsin-Madison</span></span>
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<p>Three atmospheric rivers last year were particularly devastating. </p>
<p>In January, California was hit with a strong atmospheric river that caused <a href="https://www.washingtonpost.com/weather/2021/01/27/california-winter-storm-flooding-blizzard/">record-breaking rainfall and blizzards</a>. It also triggered a <a href="https://www.theguardian.com/us-news/2021/feb/06/california-highway-1-landslide-climate-crisis">landslide</a> on California’s iconic Highway 1. </p>
<p>In November, British Columbia, Canada was battered with <a href="https://theconversation.com/how-an-atmospheric-river-drenched-british-columbia-and-led-to-floods-and-mudslides-172021">record breaking rainfall</a> that left Vancouver isolated from the rest of the country.</p>
<p>And in March, Eastern Australia copped a drenching that led to widespread flooding and <a href="https://insurancecouncil.com.au/wp-content/uploads/2021/09/ICA008_CatastropheReport_6.5_FA1_online.pdf">A$652 million</a> worth of damage. All mainland states and territories except WA faced simultaneous weather warnings.</p>
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<h2>What we found</h2>
<p>Our <a href="https://journals.ametsoc.org/view/journals/clim/aop/JCLI-D-21-0606.1/JCLI-D-21-0606.1.xml">recently published research</a> provides the first quantitative summary of atmospheric rivers over Australia. It’s not all bad news – most of the time, atmospheric rivers bring beneficial rainfall to Australia. About 30% of southeast Australia’s rainfall comes from atmospheric rivers, including in the Murray-Darling Basin.</p>
<p>Rainfall is vital to this region. The Murray-Darling Basin supports over <a href="https://www.mdba.gov.au/importance-murray-darling-basin/environment">500 species</a> of birds, reptiles and fish, and around 30,000 wetlands. Agriculture in the Murray-Darling Basin contributes <a href="https://www.mdba.gov.au/why-murray-darling-basin-matters">A$24 billion</a> to the Australian economy.</p>
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Read more:
<a href="https://theconversation.com/how-an-atmospheric-river-drenched-british-columbia-and-led-to-floods-and-mudslides-172021">How an 'atmospheric river' drenched British Columbia and led to floods and mudslides</a>
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<p>However, we also found that 30-40% of the heaviest rainfall days in the Northern Murray-Darling Basin, where towns such as Tamworth, Dubbo and Orange are located, were associated with atmospheric rivers. </p>
<p>A heavy downpour in Australia’s bread basket might lead to happier farmers during a dry period, but following a wet summer – such as from La Niña – these days are less welcome. </p>
<h2>La Niña saturates soil</h2>
<p>La Niña can play a big role in flooding, as it exacerbates damage wrought by atmospheric rivers.</p>
<p>A La Niña was declared in spring in 2020 and fizzled out by March in 2021. <a href="https://theconversation.com/back-so-soon-la-nina-heres-why-were-copping-two-soggy-summers-in-a-row-173684">A second La Niña</a> arrived in the summer of 2021 and 2022. </p>
<p>During a La Niña, winds that blow from east to west near the equator strengthen. This leads to cold, deep ocean water rising up to the surface in the East Pacific, near South America, and warm ocean waters to build near Australia. </p>
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Read more:
<a href="https://theconversation.com/back-so-soon-la-nina-heres-why-were-copping-two-soggy-summers-in-a-row-173684">Back so soon, La Niña? Here's why we're copping two soggy summers in a row</a>
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<p>Warm sea surface temperatures promote rainfall, which is why La Niña is associated with <a href="http://www.bom.gov.au/climate/current/statement_archives.shtml">rainier weather</a> over much of Australia. </p>
<p>Soil is like a kitchen sponge. It absorbs water, but once it becomes saturated it can no longer soak up any more. This is what happened to eastern Australia in the months before the March floods – and when the record-breaking rain fell, the ground flooded.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/448707/original/file-20220226-32551-3u0tue.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/448707/original/file-20220226-32551-3u0tue.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/448707/original/file-20220226-32551-3u0tue.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/448707/original/file-20220226-32551-3u0tue.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/448707/original/file-20220226-32551-3u0tue.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/448707/original/file-20220226-32551-3u0tue.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/448707/original/file-20220226-32551-3u0tue.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/448707/original/file-20220226-32551-3u0tue.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">On March 23, 2021, 800kg of water vapour flowed over Sydney every second.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>Our <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021GL095335">recent research found</a> that in March 17-24 last year, NSW experienced an almost constant stream of high water vapour in the atmosphere above from both an atmospheric river that originated in the Indian Ocean and a high pressure system in the Tasman Sea. </p>
<p>On March 23, over 800kg of water vapour passed over Sydney every second - that’s 9.6 Sydney Harbours of water in one day.</p>
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Read more:
<a href="https://theconversation.com/sydneys-disastrous-flood-wasnt-unprecedented-were-about-to-enter-a-50-year-period-of-frequent-major-floods-158427">Sydney's disastrous flood wasn't unprecedented: we're about to enter a 50-year period of frequent, major floods</a>
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<p>Likewise, soil moisture in south-east Queensland has been <a href="http://www.bom.gov.au/water/landscape/?hootPostID=13514ca44d1deadb3fee343b2c226877#/sm/Relative/month/-28.4/130.4/3/Point////2022/2/26/">above average</a> since October last year. Last November was Australia’s <a href="http://www.bom.gov.au/climate/current/statements/scs75.pdf?20220214">wettest</a> November on record with south-east Queensland receiving very-much-above average rainfall. </p>
<p>This meant the ground was already sodden. So when the heavy rain fell this week, Queensland flooded.</p>
<h2>What’s the role of climate change?</h2>
<p>We also calculated the likelihood of future atmospheric rivers as big as the one in March 2021 flowing over Sydney using the <a href="https://www.carbonbrief.org/cmip6-the-next-generation-of-climate-models-explained">latest generation</a> of climate models. </p>
<p>Earth is currently on track for <a href="https://climateactiontracker.org/global/cat-thermometer/">2.7°C warming</a> by the end of the century. Under this scenario, we found the chance of a similar weather event to the March floods will become 80% more likely. This means we are on track for more extreme rainfall and flooding in Sydney.</p>
<p>We also know climate change will increase the occurrence of atmospheric rivers over the planet, but more research is needed to determine just how often we can expect these damaging events to happen, including in southeast Queensland.</p>
<p>However, this path is not final. There is still time to change the outcome if we urgently reduce emissions to stop global warming beyond 1.5°C this century. Every little bit we do to limit carbon emissions might mean one less flood and one less person who has to rebuild.</p>
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Read more:
<a href="https://theconversation.com/floods-leave-a-legacy-of-mental-health-problems-and-disadvantaged-people-are-often-hardest-hit-157576">Floods leave a legacy of mental health problems — and disadvantaged people are often hardest hit</a>
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<img src="https://counter.theconversation.com/content/176711/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kimberley Reid receives funding from the Australian Government Research Training Program. </span></em></p><p class="fine-print"><em><span>Andrew King receives funding from the Australian Research Council and the National Environmental Science Program. </span></em></p>A weather system called ‘atmospheric rivers’ is causing this inundation. In March last year, an atmospheric river brought 800kg of water vapour over Sydney every second.Kimberley Reid, PhD Researcher in Atmospheric Science, The University of MelbourneAndrew King, Senior Lecturer in Climate Science, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.