tag:theconversation.com,2011:/us/topics/clouds-807/articles
Clouds – The Conversation
2024-03-12T19:15:29Z
tag:theconversation.com,2011:article/225088
2024-03-12T19:15:29Z
2024-03-12T19:15:29Z
Pacific Islanders have long drawn wisdom from the Earth, the sky and the waves. Research shows the science is behind them
<p>One afternoon last year, we sat in a village hall in Fiji chatting to residents about traditional ways of forecasting tropical cyclones. One man mentioned a black-winged storm bird known as “manumanunicagi” that glides above the land only when a cyclone is forming out to sea. As the conversation continued, residents named at least 11 bird species, the odd behaviour of which signalled imminent changes in the weather. </p>
<p>As we were leaving later that evening, an elder took us aside. He was pleased we had taken their beliefs seriously and said many older Pacific people won’t talk about traditional knowledge for fear of ridicule.</p>
<p>This reflects the dominance of science-based understandings in adapting to climate change and its threats to ways of life. Our <a href="https://wires.onlinelibrary.wiley.com/doi/10.1002/wcc.882">new research</a> suggests this attitude should change. </p>
<p>We reviewed evidence on traditional knowledge in the Pacific for coping with climate change, and found much of it was scientifically plausible. This indicates such knowledge should play a significant role in sustaining Pacific Island communities in future.</p>
<h2>A proven, robust system</h2>
<p>Our research was co-authored with 26 others, most Pacific Islanders with long-standing research interests in traditional knowledge.</p>
<p>People have inhabited the Pacific Islands for 3,000 years or <a href="https://www.routledge.com/Archaeology-of-Pacific-Oceania-Inhabiting-a-Sea-of-Islands/Carson/p/book/9781032486376">more</a> and have experienced many climate-driven challenges to their livelihoods and survival. They have coped not by luck but by design – through robust systems of traditional knowledge built by diverse groups of people over time.</p>
<p>The main short-term climate-related threats to island livelihoods in the Pacific are tropical cyclones which can damage food crops, pollute fresh water and destroy infrastructure. Prolonged droughts – common during El Niño events in the southwest Pacific – <a href="https://doi.org/10.1007/s10584-021-03112-1">also cause</a> widespread damage.</p>
<p>Traditional knowledge in the Pacific explains the causes and manifestations of natural phenomena, and identifies the best ways to respond. It is commonly communicated orally between generations. </p>
<p>Here, we describe such knowledge relating to animals, plants, water and sky – and show how these beliefs make scientific sense.</p>
<p>It’s important to note, however, that traditional knowledge has its own intrinsic value. Scientific explanations are not required to validate it.</p>
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<strong>
Read more:
<a href="https://theconversation.com/secrets-in-the-canopy-scientists-discover-8-striking-new-bee-species-in-the-pacific-222599">Secrets in the canopy: scientists discover 8 striking new bee species in the Pacific</a>
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<h2>Reading the ocean and sky</h2>
<p>Residents of Fiji’s Druadrua Island interpret breaking waves to predict a cyclone as long as one month before it hits. In Vanuatu’s Torres Islands, 13 phrases exist to describe the state of the tide, including anomalies that <a href="https://doi.org/10.1002/j.1834-4461.2004.tb02856.x">herald uncommon events</a>.</p>
<p>These observations make scientific sense. Distant storms can drive ocean swells onto coasts long before the winds and rain arrive, changing the usual patterns of waves.</p>
<p>In Samoa, <a href="https://journals.sagepub.com/doi/abs/10.1177/25148486211047739">ten types of wind</a> are recognised in traditional lore. Winds that blow from the east (matā ‘upolu) indicate the imminent arrival of heavy rain, possibly a tropical cyclone. The south wind (tuā'oloa) is most feared. It will cease to blow, it is said, only when its appetite for death is <a href="https://link.springer.com/article/10.1007/s10584-009-9722-z">sated</a>.</p>
<p>Many Pacific Island communities believe a cloudless, dark blue sky signals the arrival of a tropical cyclone. Other signs include unusually rapid cloud movements and the appearance of “short rainbows”. </p>
<p>These beliefs are supported by science. Rainbows are sometimes “shortened” or partly obscured by a distant rain shower. And Western science has <a href="https://link.springer.com/book/10.1007/978-0-387-71543-8">long recognised</a> changes in clouds and winds can signal the development of cyclones.</p>
<p>In Vanuatu, a halo around a moon signals <a href="https://doi.org/10.1175/wcas-d-13-00053.1">imminent rainfall</a>. Again, this belief is scientifically sound. According to Western science, high thin cirrus clouds signal nearby storms. The clouds contain ice crystals through which moonlight is filtered, creating a halo effect.</p>
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Read more:
<a href="https://theconversation.com/teaching-our-children-from-books-not-the-sea-how-climate-change-is-eroding-human-rights-in-vanuatu-192016">'Teaching our children from books, not the sea': how climate change is eroding human rights in Vanuatu</a>
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</p>
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<h2>The wisdom of animals and plants</h2>
<p>As mentioned above, birds are are said to herald weather changes across the Pacific.</p>
<p>In Tonga, when the frigate bird flies across the land – unusual behaviour for an ocean species – it signals a tropical cyclone is developing. This traditional knowledge is captured in the logo of the <a href="https://met.gov.to">Tonga Meteorological Service</a>. Birds are similarly interpreted in <a href="https://doi.org/10.1080/17477891.2015.1046156">Fiji</a> and <a href="https://doi.org/10.1177/25148486211047739">northern Vanuatu</a>.</p>
<p>This belief stacks up scientifically. One <a href="https://doi.org/10.1016/j.cub.2014.10.079">study</a> in North America, for example, showed golden-winged warblers dodged tornadoes by detecting shifts in infrasound. Another <a href="https://doi.org/10.1038/s41598-019-41481-x">study</a>, which included data on frigate birds in the Pacific, found seabirds appeared to circumvent cyclones, probably by sensing wind strength and direction.</p>
<figure class="align-right ">
<img alt="plantain tree in field" src="https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=799&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=799&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=799&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.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">
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<span class="caption">When the central shoot of the plantain is curled, people know a cyclone is developing.</span>
<span class="attribution"><span class="source">Patrick Nunn</span></span>
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<p>Traditional knowledge about insect behaviour in the Pacific Islands is also used to predict wet weather.</p>
<p>Bees, wasps and hornets usually build nests in tree branches. When nests are built close to the ground, Pacific Islanders know the forthcoming wet season will be wetter than normal, probably due to more tropical cyclones. This type of nest-building may <a href="https://doi.org/10.1080/17477891.2015.1046156">prompt</a> residents to make appropriate preparations such as storing food.</p>
<p>Studies suggest insect behaviour can predict changes in weather. For example, <a href="https://doi.org/10.1016/j.crvi.2009.10.007">a study</a> of wasp nesting in French Guiana found their ability to quickly move nests to more sheltered locations may help them survive wet years.</p>
<p>Across the Pacific, common signs of impending wet weather are found in the <a href="https://doi.org/10.1007/s10113-020-01613-w">behaviours</a> of <a href="https://doi.org/10.5751/ES-08100-210207">some plants</a>. The central shoot of the plantain, for example, will be conspicuously curled instead of straight.</p>
<p>This can be <a href="https://doi.org/10.1093/jxb/eru327">explained</a> scientifically by a process in which plant leaves close to protect their reproductive organs from extreme weather.</p>
<h2>Planning for a warmer future</h2>
<p>Since colonisation imposed Western worldviews around the world, traditional knowledge has been sidelined. This is true of the Pacific Islands, where in some places, traditional knowledge is all but <a href="https://theconversation.com/teaching-our-children-from-books-not-the-sea-how-climate-change-is-eroding-human-rights-in-vanuatu-192016">forgotten</a>. </p>
<p>But both Western and traditional knowledges have their pros and cons. Science-based knowledge, for example, is generic and often can’t realistically be applied <a href="https://theconversation.com/pacific-islands-must-stop-relying-on-foreign-aid-to-adapt-to-climate-change-because-the-money-wont-last-132095">at local scales</a>. </p>
<p>As climate change impacts worsen, optimal planning for island peoples should combine both approaches. This will require open-mindedness and a respect for diverse sources of knowledge.</p><img src="https://counter.theconversation.com/content/225088/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Patrick D. Nunn receives funding from the Department of Foreign Affairs and Trade (DFAT) via the Australia Pacific Climate Partnership (APCP), the Australian Research Council, and the Asia-Pacific Network for Global Change Research.</span></em></p><p class="fine-print"><em><span>Roselyn Kumar receives funding from the Department of Foreign Affairs and Trade (DFAT) via the Australia Pacific Climate Partnership (APCP)</span></em></p>
We reviewed evidence on traditional knowledge in the Pacific for coping with climate change, and found much of it was scientifically plausible.
Patrick D. Nunn, Professor of Geography, School of Law and Society, University of the Sunshine Coast
Roselyn Kumar, Adjunct Research Fellow in Geography and Social Sciences, University of the Sunshine Coast
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/222851
2024-02-26T13:38:23Z
2024-02-26T13:38:23Z
How 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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<blockquote>
<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>
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<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>
<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/222851/count.gif" alt="The Conversation" width="1" height="1" />
<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 University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/211088
2023-10-12T21:13:09Z
2023-10-12T21:13:09Z
How clouds protect coral reefs, but will not be enough to save them from us
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<p>Coral reefs are vital <a href="https://www.noaa.gov/education/resource-collections/marine-life/coral-reef-ecosystems">ecosystems</a> for people and coastal communities. They provide <a href="https://www.coast.noaa.gov/states/fast-facts/coral-reefs.html">food and livelihoods</a> and protect coastlines from storms, contribute to local economies and preserve cultural heritage.</p>
<p>However, warming ocean temperatures as a result of human-made climate change present considerable risks to the reefs. The recent rise in <a href="https://doi.org/10.1038/nature21707">coral bleaching</a> all over the world is the most visible impact.</p>
<p>But what is <a href="https://oceanservice.noaa.gov/facts/coral_bleach.html">coral bleaching</a>? Coral bleaching is a phenomenon that occurs when the white skeleton of the corals becomes visible after the microalgae that live inside their translucent tissues are expelled. </p>
<p>Even though coral reefs can <a href="https://reefresilience.org/stressors/bleaching/bleaching-biology/">recover</a> from bleaching events, the process, much like the regrowth of a forest following a windstorm or wildfire, requires a considerable amount of time. And, as our research has shown, an appreciation of the role of cloud cover.</p>
<h2>Relief in the clouds</h2>
<p>Although coral bleaching is generally linked only to ocean temperatures, the process itself is a product of the interaction between high <a href="https://reefresilience.org/stressors/bleaching/bleaching-biology/">temperatures and sunlight levels in a given area</a>. </p>
<p>If the temperatures are high enough, the coral and microalgae become more light-sensitive. When combined with <a href="https://doi.org/10.3389/fmicb.2014.00422">excessive sunlight</a>, this sensitivity harms the microalgae which, in turn, results in the production of chemical compounds called <a href="https://doi.org/10.1242/jeb.009597">reactive oxygen species</a>. These compounds are harmful to many species and in the case of reefs cause the coral to expel its microalgae.</p>
<p>In the same way that clouds protect us from harmful exposure to UV rays, clouds also provide a protective barrier for the world’s coral reefs. Field studies of coral bleaching events in <a href="https://www.int-res.com/abstracts/meps/v222/p209-216/">French Polynesia</a> and in the <a href="https://doi.org/10.1038/s41598-019-40150-3">Republic of Kiribati</a> found that periods of cloudiness may have reduced the bleaching severity and extent. </p>
<p>Climate change is projected to kill off most of the world’s coral reefs, even in scenarios with only <a href="http://dx.doi.org/10.1038/nclimate1674">1.5 C</a> of global warming. Yet, to date, most analysis has only considered the effect of temperature. Could incorporating clouds change the forecast?</p>
<h2>Considering cloudiness</h2>
<p>In order to understand how cloudiness might influence the response of coral reefs to climate change, <a href="https://doi.org/10.1371/journal.pclm.0000090">our recent study</a> used a <a href="https://doi.org/10.1371/journal.pone.0281719">global historical database</a> containing almost 38,000 coral bleaching reports to train an algorithm that estimates bleaching severity based on incoming light and temperature stress. </p>
<p>Our algorithm was then <a href="https://www.climateneutralgroup.com/en/news/five-future-scenarios-ar6-ipcc/">applied to four different future climate scenarios</a> on the world’s coral reefs to assess if and when bleaching conditions would become too frequent for reefs to recover. The results indicate that under a low emissions scenario, increased cloudiness would indeed have an effect on the coral bleaching conditions. This means that corals would have more time to recover from the impacts of rising temperatures and improve their resilience. </p>
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Read more:
<a href="https://theconversation.com/coral-reefs-how-climate-change-threatens-the-hidden-diversity-of-marine-ecosystems-211007">Coral reefs: How climate change threatens the hidden diversity of marine ecosystems</a>
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<p>However, even under a low carbon emission scenario, this extra time will not be enough to prevent more than 70 per cent of global reefs experiencing frequent bleaching conditions with not enough time in between to fully recover.</p>
<p>This highlights the severity of the coral bleaching crisis caused by thermal stress and the limitations of relying solely on cloudiness as a protective mechanism. Simply put, while clouds can offer some relief to corals, they cannot mitigate the long-term consequences of climate change when the sea surface temperature becomes too high.</p>
<h2>Clear implications</h2>
<p>Cloud cover may offer temporary relief to coral reefs by delaying the adverse environmental conditions responsible for coral bleaching. However, that seems to be partially true only in the lowest emission scenario which would be possible only if we dramatically cut greenhouse gas emissions.</p>
<p>Without doing that, dangerously frequent bleaching conditions are unavoidable and reefs will continue to be threatened even if we cut down emissions now. Moreover, we also need to get serious about habitat and biodiversity protection <a href="https://www.epa.gov/coral-reefs/threats-coral-reefs">to increase resilience</a>. </p>
<p>Only by doing this could coral reefs stand a chance at surviving the increasing pressures of climate change. Any other approach has its head in the clouds.</p><img src="https://counter.theconversation.com/content/211088/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Pedro C. González Espinosa receives funding from the Nippon Foundation Ocean Nexus, School of Resource and Environmental Management (REM), Simon Fraser University (SFU). </span></em></p><p class="fine-print"><em><span>Simon Donner receives funding from Natural Sciences and Engineering Research Council and the Social Sciences and Humanities Research Council.</span></em></p>
Understanding how both cloud cover and temperature work to promote coral bleaching provides valuable insight into how reefs will change over various climate scenarios.
Pedro C. González Espinosa, Postdoctoral Reserach Fellow, The School of Resource and Environmental Management, Simon Fraser University
Simon Donner, Professor, Department of Geography, University of British Columbia
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/192433
2022-11-16T16:30:39Z
2022-11-16T16:30:39Z
Air pollution cools climate more than expected – this makes cutting carbon emissions more urgent
<figure><img src="https://images.theconversation.com/files/494072/original/file-20221108-20-f4wftr.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5991%2C3988&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rising pollution on the Delhi-Jaipur Expressway, India.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/people-pass-through-rising-pollution-on-2073480677">Sudarshan Jha/Shutterstock</a></span></figcaption></figure><p>Air pollutants kill around seven million people <a href="https://ourworldindata.org/data-review-air-pollution-deaths">every year</a>. Much of this pollution is tiny particles suspended in the air which, when inhaled, can cause people to develop <a href="https://www.sciencedirect.com/science/article/pii/S0146280615000043">heart</a> and <a href="https://link.springer.com/article/10.1007/s11356-021-13208-x">lung</a> diseases, as well as <a href="https://jamanetwork.com/journals/jama/article-abstract/194704">cancer</a>.</p>
<p>Small particles in the atmosphere also birth clouds, whether they are crystals of sea salt from the Southern Ocean or sulphate from industrial chimneys. Collectively, these particles are called aerosols. </p>
<p>Moisture in the atmosphere can only condense into cloud droplets with aerosols. The aerosols that fossil fuel burning adds to the atmosphere make these droplets more numerous and clouds more reflective of sunlight, and potentially longer-lasting. All of this increases the amount of sunlight that clouds scatter back to space instead of being absorbed by the Earth. This is partly why the Intergovernmental Panel on Climate Change (IPCC) has <a href="https://www.ipcc.ch/report/ar6/wg1/chapter/summary-for-policymakers/">concluded</a> that human-made aerosols cool the climate and mask some of the warming from greenhouse gases.</p>
<p>This may sound like good news, but there is no cause for celebration. Aerosols (and their cooling effect) are very short-lived. While the CO₂ emitted into the atmosphere today from cars and coal power stations will still be there <a href="https://climate.nasa.gov/news/2915/the-atmosphere-getting-a-handle-on-carbon-dioxide/">centuries later</a>, the aerosols emitted as air pollution will cease to have an influence a month from now. This means that as soon as we stop emitting aerosols, their buffering effect on climate change disappears, while the greenhouse gases in our atmosphere will continue to heat the planet.</p>
<p>And in <a href="https://www.nature.com/articles/s41586-022-05122-0">new research</a>, we found that the effect of air pollution on the reflectivity of clouds may be bigger than previously assessed. If the extent to which air pollution masks the greenhouse effect is indeed bigger, delegates gathered in Sharm El-Sheikh for COP27, the latest <a href="https://unfccc.int/event/cop-27">UN climate change summit</a>, must work even harder to reduce fossil fuel burning.</p>
<h2>The effect of aerosols on clouds</h2>
<p>We used data on ship emissions to quantify the effect of human-emitted aerosols on the climate. Ship emissions often pollute relatively clear air far from land, which makes it easier to study the effects of aerosols in isolation. Some of the aerosols emitted by ships are visible in satellite images as long, white streaks called ship tracks. But our data suggest that less than 5% of this pollution is visible.</p>
<figure class="align-center ">
<img alt="A satellite image showing white streaks of cloud over the ocean." src="https://images.theconversation.com/files/493893/original/file-20221107-12049-du86z8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/493893/original/file-20221107-12049-du86z8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=665&fit=crop&dpr=1 600w, https://images.theconversation.com/files/493893/original/file-20221107-12049-du86z8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=665&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/493893/original/file-20221107-12049-du86z8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=665&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/493893/original/file-20221107-12049-du86z8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=835&fit=crop&dpr=1 754w, https://images.theconversation.com/files/493893/original/file-20221107-12049-du86z8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=835&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/493893/original/file-20221107-12049-du86z8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=835&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ship tracks arise when aerosol emissions from ships enter clouds and make them brighter.</span>
<span class="attribution"><span class="source">NASA WorldView/D Watson-Parris</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our study used a global database of ship routes containing more than 2 million tracks over six years. Combined with weather forecasting models, we simulated where these emissions were carried by the wind and entered clouds, which allowed us to study the aerosol effect even when no ship tracks were visible. Using satellite data, we measured the number of droplets and the amount of water in polluted versus unpolluted clouds.</p>
<p>We found that ship emissions – even when invisible in satellite images – make nearby clouds more reflective. This is partly because invisible ship emissions (the vast majority) increase the amount of water in clouds. <a href="https://www.nature.com/articles/s41586-019-1423-9">Previous estimates</a> suggested that ship emissions had a slight drying effect on clouds, which is why scientists are likely to have underestimated how much air pollution cools the atmosphere. The same may be true for aerosols more generally: air pollution may brighten clouds more than previously understood, entailing a stronger cooling effect. More research is needed before scientists can apply these results to all air pollution, </p>
<p>Another <a href="http://pnas.org/doi/abs/10.1073/pnas.2206885119">recent study</a> from our research group gave a glimpse of a future with less air pollution. We used computer algorithms trained to find visible ship tracks in satellite images before and after <a href="https://www.imo.org/en/MediaCentre/HotTopics/Pages/Sulphur-2020.aspx">regulations</a> were introduced in 2020 by the International Maritime Organization to lower air pollution from global shipping. We found that the resulting reduction in ship pollution slashed the number of visibly brighter (and so, more reflective) clouds in ship tracks by 25%. This illustrates how reducing air pollution alone may unintentionally warm the climate.</p>
<h2>Air pollution and climate action</h2>
<p>But regulating air pollution is <a href="https://iopscience.iop.org/article/10.1088/1748-9326/abe06b/meta">not at odds</a> with protecting the climate. In many cases, both are achievable by eliminating their common cause: <a href="https://www.nature.com/articles/s41586-019-1554-z">fossil fuels</a>. </p>
<p>In the transport sector, that means reducing the number of cars running on fossil fuels, for example, and not just applying better filters to their exhaust pipes. Similar arguments can be made for industry, electricity generation and heating. </p>
<p>Overall, scientific understanding of air pollution and climate change compels us to end the burning of fossil fuels – both for human health and for the planet.</p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
<br><em><a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeTop">Get a weekly roundup in your inbox instead.</a> Every Wednesday, The Conversation’s environment editor writes Imagine, a short email that goes a little deeper into just one climate issue. <a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeBottom">Join the 10,000+ readers who’ve subscribed so far.</a></em></p>
<hr><img src="https://counter.theconversation.com/content/192433/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Manshausen receives funding from the European Union’s Horizon 2020 research and innovation programme under Marie Skłodowska-Curie action iMIRACLI (grant no. 860100). </span></em></p><p class="fine-print"><em><span>Philip Stier receives funding from the European Research Council Project RECAP (grant no. 724602) and the FORCeS project (grant no. 821205), both under the EU Horizon 2020 research programme. He has also received funding from the UK Natural Environment Research Council project ACRUISE (NE/S005099/1).</span></em></p><p class="fine-print"><em><span>Duncan Watson-Parris 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 best way to cut air pollution is to burn less fossil fuel.
Peter Manshausen, PhD Candidate in Atmospheric Physics, University of Oxford
Duncan Watson-Parris, Senior Research Associate in Atmospheric Physics, University of Oxford
Philip Stier, Professor of Atmospheric Physics, University of Oxford
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/191949
2022-10-06T04:21:51Z
2022-10-06T04:21:51Z
On 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>
</strong>
</em>
</p>
<hr>
<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 Melbourne
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/177233
2022-03-16T12:34:02Z
2022-03-16T12:34:02Z
Cloud seeding might not be as promising as drought-troubled states hope
<figure><img src="https://images.theconversation.com/files/446845/original/file-20220216-25-1vorff5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cloud seeding equipment near Winter Park in Colorado.</span> <span class="attribution"><a class="source" href="https://www.denverwater.org/tap/cloud-seedings-role-winter-season">Denver Water</a></span></figcaption></figure><p>On mountain peaks scattered across Colorado, <a href="https://cwcb.colorado.gov/focus-areas/supply/weather-modification-program">machines are set up to fire chemicals into the clouds</a> in attempts to generate snow. The process is called cloud seeding, and as global temperatures rise, more <a href="https://public.wmo.int/en/resources/bulletin/seeding-change-weather-modification-globally">countries</a> and <a href="https://www.theguardian.com/environment/2021/mar/23/us-stated-cloud-seeding-weather-modification">drought-troubled states</a> are using it in sometimes desperate efforts to modify the weather.</p>
<p>But cloud seeding isn’t as simple as it sounds, and it might not be as promising as people wish.</p>
<hr>
<iframe id="noa-web-audio-player" style="border: none" src="https://embed-player.newsoveraudio.com/v4?key=x84olp&id=https://theconversation.com/cloud-seeding-might-not-be-as-promising-as-drought-troubled-states-hope-177233&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>As an <a href="https://www.researchgate.net/scientific-contributions/William-R-Cotton-72102078">atmospheric scientist</a>, I have studied and <a href="https://www.cambridge.org/core/books/abs/human-impacts-on-weather-and-climate/rise-of-the-science-of-weather-modification-by-cloud-seeding/973C1181FD0E4220848FC83AFE05D2D2">written about weather modification</a> for 50 years. Cloud seeding <a href="https://doi.org/10.1073/pnas.1917204117">experiments that produce snow or rain</a> require the <a href="https://doi.org/10.1175/JAMC-D-18-0341.1">right kind of clouds</a> with enough moisture, and the right temperature and wind conditions. The percentage increases in precipitation are small, and it’s difficult to tell when snow or rain fell naturally and when it was triggered by seeding.</p>
<h2>How modern cloud seeding began</h2>
<p>The modern age of weather modification began in the 1940s in Schenectady, New York. </p>
<p>Vince Schaefer, a scientist working for General Electric, <a href="https://patentimages.storage.googleapis.com/7f/03/d4/b4e0d609dd15ee/US2570867.pdf">discovered that adding small pellets of dry ice</a> to a freezer containing “<a href="https://www.pnnl.gov/news-media/supercooled-water-stable-liquid-scientists-show-first-time">supercooled</a>” water droplets triggered a proliferation of ice crystals. </p>
<p><a href="https://rammb.cira.colostate.edu/wmovl/vrl/tutorials/euromet/courses/glossary/bergeron.htm">Other scientists had theorized</a> that the right mix of supercooled water drops and ice crystals could cause precipitation. <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/snow/how-does-snow-form">Snow forms</a> when ice crystals in clouds stick together. If ice-forming particles could be added to clouds, the scientists reasoned, moisture that would otherwise evaporate might have a greater chance of falling. Schaefer proved it could work.</p>
<p>On Nov. 13, 1946, Schaefer <a href="https://archive.org/stream/historyofproject00have/historyofproject00have_djvu.txt">dropped crushed dry ice</a> from a plane into supercooled stratus clouds. “I looked toward the rear and was thrilled to see long streamers of snow falling from the base of the cloud through which we had just passed,” <a href="https://archive.org/stream/historyofproject00have/historyofproject00have_djvu.txt">he wrote in his journal</a>. A few days later, he wrote that trying the same technique appeared to have improved visibility in fog.</p>
<figure class="align-center ">
<img alt="A man looks into a freezer looking amazed at what he sees." src="https://images.theconversation.com/files/446705/original/file-20220216-3223-1u7dpe1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446705/original/file-20220216-3223-1u7dpe1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=827&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446705/original/file-20220216-3223-1u7dpe1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=827&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446705/original/file-20220216-3223-1u7dpe1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=827&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446705/original/file-20220216-3223-1u7dpe1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1040&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446705/original/file-20220216-3223-1u7dpe1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1040&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446705/original/file-20220216-3223-1u7dpe1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1040&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Vincent Schaefer, in foreground, examines snow created in a modified GE freezer in 1947, with Irving Langmuir, at left, and Bernard Vonnegut.</span>
<span class="attribution"><a class="source" href="https://nyheritage.contentdm.oclc.org/digital/collection/p16694coll20/id/5747/rec/33">General Electric Company/Museum of Science and Innovation</a></span>
</figcaption>
</figure>
<p>A colleague at GE, Bernie Vonnegut, searched through chemical tables for materials with a crystallographic structure similar to ice and discovered that <a href="https://doi.org/10.1063/1.1697813">a smoke of silver iodide particles</a> could have the same effect at temperatures below -20 C (-4 F) as dry ice.</p>
<p>Their research led to <a href="https://archive.org/stream/historyofproject00have/historyofproject00have_djvu.txt">Project Cirrus</a>, a joint civilian-military program that explored seeding a variety of clouds, including supercooled stratus clouds, cumulus clouds and <a href="https://vlab.noaa.gov/web/nws-heritage/-/almost-science-fiction-hurricane-modification-and-project-stormfury">even hurricanes</a>. Within a few years, communities and companies that rely on water were spending US$3 million to $5 million a year on cloud-seeding projects, particularly in the drought-troubled western U.S., <a href="https://www.nsf.gov/nsb/publications/1965/nsb1265.pdf">according to congressional testimony in the early 1950s</a>.</p>
<h2>But does cloud seeding actually work?</h2>
<p>The results of about 70 years of research into the effectiveness of cloud seeding are mixed.</p>
<p>Most scientific studies aimed at evaluating the effects of seeding cumulus clouds have shown little to no effect. However, the results of seeding wintertime <a href="https://cloudatlas.wmo.int/en/orographic-influences-on-clouds.html">orographic clouds</a> – clouds that form as air rises over a mountain – have <a href="https://doi.org/10.1073/pnas.1917204117">shown increases in precipitation</a>.</p>
<p>There are two basic approaches to cloud seeding. One is to seed supercooled clouds with silver iodide or dry ice, causing ice crystals to grow, consume moisture from the cloud and fall as snow or rain. It might be shot into the clouds in rockets or sprayed from an airplane or mountaintop. The second involves warm clouds and <a href="https://www.nytimes.com/2003/09/02/science/q-a-salt-and-humidity.html">hygroscopic</a> materials like salt particles. These particles take on water vapor, becoming larger to fall faster.</p>
<figure class="align-center ">
<img alt="A drawing of a plane flying" src="https://images.theconversation.com/files/446703/original/file-20220216-28-1gyqh5x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446703/original/file-20220216-28-1gyqh5x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=906&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446703/original/file-20220216-28-1gyqh5x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=906&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446703/original/file-20220216-28-1gyqh5x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=906&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446703/original/file-20220216-28-1gyqh5x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1139&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446703/original/file-20220216-28-1gyqh5x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1139&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446703/original/file-20220216-28-1gyqh5x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1139&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An illustration of cloud-seeding processes.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Cloud_seeding#/media/File:Cloudseedingimagecorrected.jpg">Naomi E. Tesla/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The amount of snow or rain tied to cloud seeding has varied, with <a href="https://public.wmo.int/en/resources/bulletin/seeding-change-weather-modification-globally">up to 14% reported in experiments in Australia</a>. In the U.S., studies have found a few percentage points of increase in precipitation. In a 2020 study, scientists <a href="https://doi.org/10.1073/pnas.1917204117">used radar to watch as 20 minutes of cloud seeding</a> caused moisture inside clouds to thicken and fall. In all, about one-tenth of a millimeter of snow accumulated on the ground below in a little over an hour.</p>
<p>Another study, in 2015, used climate data and a <a href="https://doi.org/10.1175/JAMC-D-17-0335.1">six-year cloud-seeding experiment</a> in the mountains of Wyoming to estimate that <a href="https://doi.org/10.1175/JAMC-D-14-0163.1">conditions there were right</a> for cloud seeding about a quarter of the time from November to April. But the results likely would increase the snowpack by <a href="https://doi.org/10.1175/JAMC-D-18-0341.1">no more than about 1.5%</a> for the season.</p>
<p>While encouraging, these experiments have by no means reached the level of significance that Schaefer and his colleagues had anticipated.</p>
<h2>Weather modification is gaining interest again</h2>
<p><a href="https://doi.org/10.1175/JAMC-D-18-0341.1">Scientists today are continuing to carry out randomized seeding experiments</a> to determine when cloud seeding enhances precipitation and by how much.</p>
<p>People have raised a few concerns about negative effects from cloud seeding, but those effects appear to be minor. Silver ion is a <a href="https://doi.org/10.1029/WR006i001p00088">toxic heavy metal</a>, but the amount of silver iodide in seeded snowpack is so small that extremely sensitive instrumentation must be used to detect its presence. </p>
<figure class="align-center ">
<img alt="A man attaches a row of canisters to an airplane wing." src="https://images.theconversation.com/files/446701/original/file-20220216-27-1tukw0v.jpg?ixlib=rb-1.1.0&rect=5%2C5%2C3637%2C2419&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446701/original/file-20220216-27-1tukw0v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446701/original/file-20220216-27-1tukw0v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446701/original/file-20220216-27-1tukw0v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446701/original/file-20220216-27-1tukw0v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446701/original/file-20220216-27-1tukw0v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446701/original/file-20220216-27-1tukw0v.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">Several companies attempt cloud seeding from airplanes.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/DroughtCloudSeeding/afa3c57641344d3f9165eedf834b388e/photo">AP Photo/Dave Kolpack</a></span>
</figcaption>
</figure>
<p>Meanwhile, extreme weather and droughts are increasing interest in weather modification. </p>
<p>The World Meteorological Organization reported in 2017 that weather modification programs, including suppressing crop-damaging hail and increasing rain and snowfall, were underway in <a href="https://public.wmo.int/en/resources/bulletin/seeding-change-weather-modification-globally">more than 50 countries</a>. My home state of Colorado has <a href="https://cwcb.colorado.gov/weather-modification-grant-program">supported cloud-seeding operations</a> for years. Regardless of the mixed evidence, many communities are counting on it to work.</p><img src="https://counter.theconversation.com/content/177233/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William R. Cotton 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>
Several states are experimenting with weather modification to try to generate snow as water supplies shrink. An atmospheric scientist explains the history behind it – and the challenges.
William R. Cotton, Professor Emeritus of Meteorology, Colorado State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/167869
2021-12-20T13:14:33Z
2021-12-20T13:14:33Z
What’s the record for how long it’s ever rained without stopping?
<figure><img src="https://images.theconversation.com/files/436774/original/file-20211209-172173-1watr8u.jpg?ixlib=rb-1.1.0&rect=7%2C29%2C4881%2C3224&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some places rarely see the sun.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-raindrops-on-plant-royalty-free-image/963251882">Donat Photography / EyeEm</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
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</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>What is the longest time it has ever rained for? – Wayne</strong></p>
</blockquote>
<hr>
<p>The answer is – it depends. If you live in a dry place, like the Atacama Desert in South America, and it rains for an hour, that may be the precipitation record for that location. If you live in a wet place, like the Amazon rain forest, raining for 40 days in a row wouldn’t be a big deal. </p>
<p>As <a href="https://scholar.google.com/citations?hl=en&user=sWxyDPYAAAAJ">scientists who</a> <a href="https://scholar.google.com/citations?user=kok88kUAAAAJ&hl=en&oi=sra">study the weather</a>, we love rain data – and use it to learn how storm systems work. We’ve also learned what conditions produce rain records.</p>
<h2>What happens inside clouds</h2>
<p>Rain forms when moist air is lifted into the sky where it cools. As moist air chills, the water vapor molecules press together to form tiny microscopic droplets. <a href="https://theconversation.com/what-would-it-feel-like-to-touch-a-cloud-133219">Together they look like clouds</a>. Air motion inside clouds can sometimes cause the droplets to bang into each other and become larger droplets. In the upper parts of clouds, the temperature is cold enough to make ice crystals, which eventually get heavy enough to fall – and melt into rain on their way to the ground. </p>
<p>Rain can come from many different types of storms. Thunderstorms, for example, have a short life span and can produce intense downpours. Other storms, such as winter storms, can linger for several days and produce gentle rain, steady rain or, if it’s cold enough, snow. </p>
<p>In most places, weather alternates between dry and wet periods. That’s because each period of stormy weather is followed by a period of dry air with plentiful sunshine and few clouds.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/431086/original/file-20211109-19-1awmni3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A person walks with an umbrella on a rain soaked trail." src="https://images.theconversation.com/files/431086/original/file-20211109-19-1awmni3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/431086/original/file-20211109-19-1awmni3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/431086/original/file-20211109-19-1awmni3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/431086/original/file-20211109-19-1awmni3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/431086/original/file-20211109-19-1awmni3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/431086/original/file-20211109-19-1awmni3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/431086/original/file-20211109-19-1awmni3.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 new record for the amount of rain in a three-day period was set in Hilo, Hawaii - 31.85 inches fell in August 2018.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/visitors-stand-in-the-rain-at-an-overlook-for-rainbow-falls-news-photo/1023655644">Mario Tama via Getty Images News</a></span>
</figcaption>
</figure>
<p>An exception to this rule is where mountains are near oceans. In that case, as moist ocean air blows toward the land, it encounters the mountains and is forced to lift over them. Clouds can form there almost continuously, bringing rainfall that can last for weeks or longer. </p>
<h2>Days and days of rain</h2>
<p>Rainfall records exist only in places where people live and keep records. Many towns and cities don’t bother collecting rainfall data. And records don’t exist for the many uninhabited locations on Earth, like over the ocean or deep in rain forests. So rainfall data is incomplete. </p>
<p>In modern record keeping, rainfall is measured by the amount in a given time period, usually hourly or daily. A few drops of rain is called a “trace” of rain. Rainfall is “measurable” if it adds up to 0.01 inch (0.25 millimeters) or more. </p>
<p>In the U.S., the longest periods of daily rain have occurred in Hawaii, where easterly trade winds blow toward the mountains. An incredible <a href="https://weather.com/news/weather/news/rain-331-days-hawaii-record">331 consecutive days of measurable rainfall</a> were recorded at Manuawili Ranch, Maui, in 1939-40. If you include a trace of rain, the record is 881 consecutive days, or <a href="https://weather.com/news/weather/news/rain-331-days-hawaii-record">nearly three straight years</a>, at Honomu Maki, Oahu, from 1913 to 1916. This dependable and continuous rainfall is the reason that region is a tropical rainforest.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/436721/original/file-20211209-21-1j5xll6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An enormous tree trunk." src="https://images.theconversation.com/files/436721/original/file-20211209-21-1j5xll6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/436721/original/file-20211209-21-1j5xll6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/436721/original/file-20211209-21-1j5xll6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/436721/original/file-20211209-21-1j5xll6.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/436721/original/file-20211209-21-1j5xll6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/436721/original/file-20211209-21-1j5xll6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/436721/original/file-20211209-21-1j5xll6.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"></a>
<figcaption>
<span class="caption">A western cedar in the Olympic National Park rainforest in Port Angeles, Washington.</span>
<span class="attribution"><span class="source">Bill Baccus</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>In the continental U.S., the longest daily rainfalls have occurred in winter near the coastal mountain ranges of the Pacific Northwest. In 1997-98, <a href="https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?orotis">Otis, Oregon, received 79 straight days</a> of measurable rainfall. The Pacific Northwest has temperate rainforests, where the continuously wet cold season nurtures huge trees, even though it is often relatively dry in the summer.</p>
<p>There are plenty of <a href="https://www.escape.com.au/escape-travel/the-top-10-wettest-places-on-earth/news-story/993eaffca1d3d5fabc0c9d73bef06b96">other rainy places in the world</a> where moist air flows over mountains. The Meteorological Observatory in <a href="https://cherrapunjee.com/daily-weather-data/">Cherrapunjee, India, recorded 86 consecutive days of measurable rainfall</a> during the monsoon in 1995. Other rainy places include Southern New Zealand, Bioko Island in Equatorial Guinea and western Colombia in South America.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/431091/original/file-20211109-19-143i1sb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Closeup of a rain gauge." src="https://images.theconversation.com/files/431091/original/file-20211109-19-143i1sb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/431091/original/file-20211109-19-143i1sb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/431091/original/file-20211109-19-143i1sb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/431091/original/file-20211109-19-143i1sb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/431091/original/file-20211109-19-143i1sb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/431091/original/file-20211109-19-143i1sb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/431091/original/file-20211109-19-143i1sb.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">Rain gauges are the most common tool for measuring rain.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/empty-rain-gauge-during-periods-of-low-rainfall-and-drought-news-photo/1296529895">Morel J/Andia/Universal Images Group via Getty Images</a></span>
</figcaption>
</figure>
<p>If you want to know how much it rains where you live, the best way is to install a rain gauge and start recording your own daily rainfall measurements. A great resource is the <a href="https://www.cocorahs.org/">CoCoRahs Network</a>, a community of volunteers working to measure and map rain, hail and snow. </p>
<p>Collecting data about the location and intensity of all kinds of precipitation really helps scientists like us understand weather systems and improve our weather forecasting. </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/167869/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Extended periods of rain are most likely found in locations where mountains are near oceans.
Lynn McMurdie, Research Associate Professor of Atmospheric Sciences, University of Washington
Joe Boomgard-Zagrodnik, Postdoctoral Research Associate in Crop and Soil Sciences, Washington State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/168373
2021-11-04T19:08:20Z
2021-11-04T19:08:20Z
Clouds in a new light: rejected satellite data gives a fresh view of our floating companions
<figure><img src="https://images.theconversation.com/files/422557/original/file-20210922-13-4xlw96.jpg?ixlib=rb-1.1.0&rect=161%2C325%2C1203%2C776&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Grayson Cooke</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Clouds have been objects of reverie and wonder throughout human history, inspiring art and imagination, and of course warning of extreme weather events. </p>
<p>Clouds are also central players in Earth’s climate. They move water around the globe, reflect sunlight and interact with radiation emitted by the Earth, and in so doing can both cool and warm the planet. </p>
<p>How clouds react as the planet heats up is a matter of serious concern. As the <a href="https://www.ipcc.ch/report/ar6/wg1/">latest Intergovernmental Panel on Climate Change (IPCC) report</a> reiterates, we sit on the brink of a precipice in terms of our ability to slow or halt the global heating humans are causing. </p>
<p>Climate scientists study clouds closely, but translating scientific findings into forms that catch the public imagination is not always an easy task. Our new film, <a href="https://www.graysoncooke.com/path99">Path 99</a>, uses satellite imagery and the tools of art and science to show clouds in a spectacular new light. </p>
<figure>
<iframe src="https://player.vimeo.com/video/407353796" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">Data from the Himawari 8 weather satellite shows water vapour flowing through Earth’s atmosphere.</span></figcaption>
</figure>
<h2>Satellites, clouds and invalid data</h2>
<p>Remote sensing satellite data is produced by a very large multinational effort, and it makes an immense contribution to our knowledge of the world. Meteorology, geoscience and climate science all rely on satellite data. </p>
<p>But we can gain even more from this data if we explore it via the creative arts. When we bring knowledge to life through imagination and feeling, we can create new ways of experiencing, understanding and responding to our planet. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-where-do-clouds-come-from-and-why-do-they-have-different-shapes-102404">Curious Kids: where do clouds come from and why do they have different shapes?</a>
</strong>
</em>
</p>
<hr>
<p><a href="https://www.graysoncooke.com/path99">Path 99</a> – which launches next week at the <a href="https://www.nziff.co.nz/2021/wellington/path-99/">New Zealand International Film Festival</a> – uses satellite images of clouds over Australia to highlight the importance of clouds to climate. Designed to be viewed on the domed screen of a planetarium with an enveloping electronic soundtrack, it combines art, science and Earth. </p>
<p>We used data from two satellites, America’s <a href="https://www.usgs.gov/core-science-systems/nli/landsat/landsat-8?qt-science_support_page_related_con=0#qt-science_support_page_related_con">Landsat 8</a> and Japan’s <a href="https://en.wikipedia.org/wiki/Himawari_8">Himawari 8</a>, made available by Geoscience Australia and the <a href="https://www.dea.ga.gov.au/">Digital Earth Australia</a> program, and the Bureau of Meteorology.</p>
<p>Landsat 8 is an Earth observation satellite mainly used for monitoring environmental conditions at ground level. Its orbit takes it over the poles while the planet spins beneath it, which means it can view the entire globe over the course of a 16-day cycle of 233 orbits or “paths”. The track running down the centre of Australia is path 99, hence the film’s title.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/an-artists-surreal-view-of-australia-created-from-satellite-data-captured-700km-above-earth-96718">An artist's surreal view of Australia – created from satellite data captured 700km above Earth</a>
</strong>
</em>
</p>
<hr>
<p>For geoscientists, clouds are an obstruction to the view of the land from orbit. They use software to comb through satellite data pixel by pixel, identifying and removing clouds and other atmospheric noise to obtain clear images.</p>
<p>At any given time, clouds cover around two-thirds of Earth, so what the scientists sift out creates a vast archive of “invalid data” – a multi-year record of incredible cloud formations.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/422550/original/file-20210922-19-1y05asx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Satellite image showing clouds over Kati Thanda / Lake Eyre" src="https://images.theconversation.com/files/422550/original/file-20210922-19-1y05asx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422550/original/file-20210922-19-1y05asx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422550/original/file-20210922-19-1y05asx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422550/original/file-20210922-19-1y05asx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422550/original/file-20210922-19-1y05asx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422550/original/file-20210922-19-1y05asx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422550/original/file-20210922-19-1y05asx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">‘Invalid Data: Kati Thanda / Lake Eyre 12/03/2017’ (2019). This Landsat 8 satellite image shows clouds over Kati Thanda / Lake Eyre on March 12 2017.</span>
<span class="attribution"><span class="source">Grayson Cooke. NASA/USGS Landsat 8 OLI.</span></span>
</figcaption>
</figure>
<p>Our project focuses on this “invalid data”, showing the clouds, cloud shadow and gauzy fragments of land that are deemed unusable for scientific Earth observation. </p>
<p>A scientist’s waste can be an artist’s treasure. Projects like ours, combining art and science, show what can be gained when we look at the aesthetic qualities of the objects of scientific enquiry from a more human-centred perspective.</p>
<h2>Clouds in a new light</h2>
<p>Landsat 8’s sensor records what is known as “multi-spectral” imagery. This is data recorded in “bands” that isolate specific parts of the electromagnetic spectrum, from visible light to the near infrared. </p>
<p>Scientists use the infrared bands to study <a href="https://www.dea.ga.gov.au/products/dea-water-observations">plants and water</a>. When we used them to render clouds, we discovered startling colours, textures and forms.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/422551/original/file-20210922-19-z0ub2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="True colour and false colour images of clouds." src="https://images.theconversation.com/files/422551/original/file-20210922-19-z0ub2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/422551/original/file-20210922-19-z0ub2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/422551/original/file-20210922-19-z0ub2x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/422551/original/file-20210922-19-z0ub2x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/422551/original/file-20210922-19-z0ub2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/422551/original/file-20210922-19-z0ub2x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/422551/original/file-20210922-19-z0ub2x.jpg?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">On the right is a ‘true colour’ image, mapping the red, green and blue bands (432) of the sensor to RGB in the output image. On the left is a ‘false colour’ image, mapping the near infrared, and two shortwave infrared bands (567) of the sensor to RGB. The infrared image picks out large variation in cloud structure and therefore height, temperature and opacity more effectively than the true colour image.</span>
<span class="attribution"><span class="source">Grayson Cooke. NASA/USGS Landsat 8 OLI.</span></span>
</figcaption>
</figure>
<p>The dramatic shift in colouration that results from mapping the infrared bands into the visible spectrum, turning shades of white and grey into highly coloured tableaux, translates clouds into something radically unexpected. </p>
<p>Scientifically speaking, the coloured images reveal the remarkable spectral complexity of clouds, in terms of which wavelengths of sunlight they reflect and which they absorb. The variations in colour reflect wide ranges of cloud temperatures, densities, and heights, as well as the presence or absence of dust and other aerosol particles.</p>
<h2>Tracing vapour</h2>
<p>The Himawari 8 satellite sits in a geostationary orbit high above a point on the equator just north of Papua New Guinea. Its field of view allows it to record multi-spectral images of much of the Asia-Pacific region every 10 minutes, including several infrared bands used to track gases and other particles in the atmosphere. </p>
<p>In the video clips shown in this article, Path 99 uses bands designed to show the transport of water vapour around the planet. This allows us to see Australia’s clouds in their wider context, as part of the massive circulations that distribute thermal energy around the Earth.</p>
<figure>
<iframe src="https://player.vimeo.com/video/469357066" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">The “Path 99” trailer for planetarium. Imagine the circular image as a dome flipped up and rotated above your head.</span></figcaption>
</figure>
<h2>Heads in the clouds</h2>
<p>As modern human existence increasingly transforms the Earth, its atmosphere and climate, we need new ways to understand, represent and address this impact. </p>
<p>Cloud behaviours are vital clues to the extent of the changes in climate and weather. Now more than ever, we should all have our heads in the clouds.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/artists-are-not-at-the-negotiating-table-at-cop26-but-art-is-everywhere-what-can-they-accomplish-through-their-work-170786">Artists are not at the negotiating table at COP26 but art is everywhere. What can they accomplish through their work?</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/168373/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>This project has been produced with the support of Geoscience Australia and Digital Earth Australia, and with the assistance of resources from the National Computational Infrastructure (NCI) which is supported by the Australian Government.</span></em></p><p class="fine-print"><em><span>Christian Jakob receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Dugal McKinnon 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>
Clouds are central players in climate change, and ‘Path 99’ reveals them in a new light using data discarded by scientists.
Grayson Cooke, Associate Professor, Chair of Creative Arts, Southern Cross University
Christian Jakob, Professor in Atmospheric Science, Monash University
Dugal McKinnon, Associate Professor, Composition and Sonic Arts, Te Herenga Waka — Victoria University of Wellington
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/165430
2021-08-04T18:42:44Z
2021-08-04T18:42:44Z
5 things to watch for in the latest IPCC report on climate science
<figure><img src="https://images.theconversation.com/files/414584/original/file-20210804-307-1hdsycu.jpg?ixlib=rb-1.1.0&rect=76%2C69%2C4540%2C2526&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Wildfires burn on the island of Evia, north of Athens, Greece, on Aug. 3, 2021, as the country dealt with the worst heat wave in decades. Temperatures reached 41 C in parts of Athens. </span> <span class="attribution"><span class="source">(AP Photo/Michael Pappas) </span></span></figcaption></figure><p>On Aug. 9, the Intergovernmental Panel on Climate Change (IPCC) will release its most comprehensive report on the science of climate change <a href="https://www.ipcc.ch/assessment-report/ar5/">since 2013</a>. It will be the first of four reports released under the IPCC’s latest assessment cycle, with subsequent reports coming in 2022.</p>
<p>Over the past eight years, climate scientists have improved the methods they use to measure different aspects of climate and to model (or project) what might happen in the future. They’ve also been monitoring the changes that have developed right before our eyes. </p>
<p>This updated assessment comes three months before world leaders gather in Glasgow, Scotland, to find ways to avoid the worst effects of climate change and renew their commitments to reduce greenhouse gases. It also comes amid another year of <a href="https://www.cbc.ca/news/science/extreme-weather-2021-1.6128874">severe heat waves, droughts, wildfires, flooding and storms</a>. </p>
<p>The report will provide policy-makers with the best possible information regarding the physical science of climate change, which is essential for long-term planning in many sectors, from infrastructure to energy to social welfare. Here are five things to look for in the new report:</p>
<h2>1. How sensitive is the climate to increasing carbon dioxide?</h2>
<p>Atmospheric carbon dioxide (CO2) levels are higher now than they have been in 800,000 years, <a href="https://research.noaa.gov/article/ArtMID/587/ArticleID/2764/Coronavirus-response-barely-slows-rising-carbon-dioxide">reaching 419 parts per million (ppm) in May 2021</a>. Average global temperature rises with each increase in atmospheric CO2 concentration, but how much it rises depends on many factors. </p>
<p>Climate scientists use models to understand how much warming occurs when CO2 concentrations double from pre-industrial levels — from 260 ppm to 520 ppm — a concept called “<a href="https://www.metoffice.gov.uk/research/climate/understanding-climate/climate-sensitivity-explained">climate sensitivity</a>.” The more sensitive the climate, the faster greenhouse gas emissions must be curbed to stay below 2 C.</p>
<figure class="align-center ">
<img alt="Climate sensitivity is greater in CMIP6 than previous model intercomparisons." src="https://images.theconversation.com/files/414193/original/file-20210802-18-19bqb14.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414193/original/file-20210802-18-19bqb14.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=454&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414193/original/file-20210802-18-19bqb14.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=454&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414193/original/file-20210802-18-19bqb14.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=454&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414193/original/file-20210802-18-19bqb14.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=570&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414193/original/file-20210802-18-19bqb14.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=570&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414193/original/file-20210802-18-19bqb14.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=570&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Equilibrium climate sensitivity from the last three major climate model intercomparisons. (Note: There was no ‘CMIP4’.)</span>
<span class="attribution"><span class="source">(Data: IPCC, Graph: Alex Crawford)</span></span>
</figcaption>
</figure>
<p>Older climate models estimated that a doubling of atmospheric CO2 would lead to a temperature increase of <a href="https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter09_FINAL.pdf">2.1 C to 4.7 C</a>. The latest set of climate models, <a href="https://www.carbonbrief.org/cmip6-the-next-generation-of-climate-models-explained">called CMIP6</a>, broadened the range to <a href="https://www.doi.org/10.1126/sciadv.aba1981">1.8 C to 5.6 C</a>, meaning the climate is at least as sensitive to doubling of carbon dioxide as previous models showed, but may, in fact, <a href="https://doi.org/10.1029/2019GL085782">be even more sensitive</a>.</p>
<p>The range is influenced by uncertainties in a number of climate factors, including water vapour and cloud cover, and how they will increase or decrease the effects of warming. Scientists are working to narrow the range in climate projections so that we know more about how quickly we must reduce greenhouse gas emissions to avoid the worst effects of climate change and adapt to others.</p>
<h2>2. What’s going on with clouds?</h2>
<p>Clouds are a wild card in the climate change game. They create <a href="https://climate.nasa.gov/nasa_science/science/">feedbacks to warming</a>, meaning that warming changes cloud cover, but <a href="http://www.climate.be/textbook/chapter4_node8.html">cloud cover can also speed up or slow down warming</a> in different situations. </p>
<p>Clouds reflect about <a href="https://earthobservatory.nasa.gov/features/EnergyBalance">a quarter of incoming sunlight</a> away from the Earth. So, if more warming leads to more clouds, we would expect more sunlight to be reflected, slowing warming. However, clouds also insulate the Earth, trapping the heat given off by the surface. So, increasing cloud cover (like during nighttime) could amplify warming. </p>
<figure class="align-center ">
<img alt="Multiple cloud types" src="https://images.theconversation.com/files/414192/original/file-20210802-22-1kxulbf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414192/original/file-20210802-22-1kxulbf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414192/original/file-20210802-22-1kxulbf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414192/original/file-20210802-22-1kxulbf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414192/original/file-20210802-22-1kxulbf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414192/original/file-20210802-22-1kxulbf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414192/original/file-20210802-22-1kxulbf.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">Cloud feedback properties depend in part on the type and altitude of the cloud.</span>
<span class="attribution"><span class="source">(Alex Crawford)</span></span>
</figcaption>
</figure>
<p><a href="https://e360.yale.edu/features/why-clouds-are-the-key-to-new-troubling-projections-on-warming">Two main issues stand out</a>: First, many factors, including cloud type, altitude and season, determine a cloud’s overall effect on warming. Second, clouds are incredibly difficult to model; how the models treat clouds is key to the range in climate sensitivity.</p>
<h2>3. Did climate change fuel recent extreme weather?</h2>
<p>Since the last IPCC report, our ability to assess global warming’s impact on extreme events has improved immensely. <a href="https://www.ipcc.ch/site/assets/uploads/2018/09/AR6_WGI_outlines_P46.pdf">Chapter 11 of the latest report</a> is devoted to this. </p>
<p>Global warming means <a href="https://www.worldweatherattribution.org/western-north-american-extreme-heat-virtually-impossible-without-human-caused-climate-change/">stronger summer heat waves</a> and <a href="https://climateatlas.ca/map/canada/tropicalnights_2060_85#">more frequent tropical nights</a> (temperatures above 20 C) are occurring in middle latitudes, like Canada and Europe.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/record-breaking-temperatures-mean-we-must-change-the-way-we-talk-about-the-climate-emergency-163627">Record-breaking temperatures mean we must change the way we talk about the climate emergency</a>
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</em>
</p>
<hr>
<p><a href="https://news.climate.columbia.edu/2019/09/23/climate-change-impacts-water/">Warmer air can hold more water</a>. This can cause more evaporation from land, and lead to drought and wildfires. In addition, an atmosphere with more water can produce more precipitation and flooding. </p>
<p>Scientists projected decades ago that these changes to the water cycle <a href="https://www.ipcc.ch/report/ar4/wg1/">would occur</a>, but now it’s clear they’re <a href="https://doi.org/10.1038/s41586-018-0673-2">already happening</a>. </p>
<h2>4. Have regional climate projections improved?</h2>
<figure class="align-right ">
<img alt="head of Shamrock glacier, with bare mountain peaks behind it" src="https://images.theconversation.com/files/414197/original/file-20210802-28-1fyf84o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/414197/original/file-20210802-28-1fyf84o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414197/original/file-20210802-28-1fyf84o.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414197/original/file-20210802-28-1fyf84o.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414197/original/file-20210802-28-1fyf84o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414197/original/file-20210802-28-1fyf84o.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414197/original/file-20210802-28-1fyf84o.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Shamrock Glacier, like many other glaciers in Alaska, has been thinning and retreating since the 1950s.</span>
<span class="attribution"><span class="source">(Alex Crawford)</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The climate models evaluated by the IPCC <a href="https://www.climate.gov/maps-data/primer/climate-models">are global models</a>. This is essential to capture the connections between tropics and poles or land and ocean. However, it comes at a cost — the models struggle to simulate many features smaller than 100 kilometres across, like small storms or islands. </p>
<p>Regional relationships can be complex: For example, extreme storms help <a href="https://doi.org/10.1175/JCLI-D-19-0925.1">break up summer Arctic sea ice</a>, but reduced sea ice cover may also <a href="https://doi.org/10.1029/2020JD034366">lead to stronger storms</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/5-ways-climate-driven-ocean-change-can-threaten-human-health-162341">5 ways climate-driven ocean change can threaten human health</a>
</strong>
</em>
</p>
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<p>Since the last IPCC report, <a href="https://www.gfdl.noaa.gov/climate-model-downscaling/">techniques for taking this large-scale information and refining it</a> have shown how regional and local climate has changed and could change in the future. Other experiments target regional issues, like the <a href="https://www.wcrp-climate.org/modelling-wgcm-mip-catalogue/cmip6-endorsed-mips-article/1303-modelling-cmip6-pamip">impacts of Arctic sea ice loss</a> on storms.</p>
<h2>5. How will Antarctic ice sheets contribute to sea-level rise?</h2>
<p><a href="https://sealevel.nasa.gov/understanding-sea-level/global-sea-level/overview">Global sea level is rising</a> because <a href="https://www.carbonbrief.org/explainer-how-climate-change-is-accelerating-sea-level-rise">water expands slightly when it warms up</a>, and <a href="https://www.nps.gov/glac/learn/nature/climate-change.htm">mountain glaciers</a> and the <a href="https://nsidc.org/greenland-today/">Greenland Ice Sheet</a> are melting and adding water to the ocean. </p>
<p>But the largest potential source of sea-level rise over the next century is Antarctica. <a href="https://www.carbonbrief.org/studies-shed-new-light-on-antarcticas-future-contribution-to-sea-level-rise">Ice sheet models show</a> that melting of Antarctic ice sheets will add between 14 and 114 centimetres to sea-level rise by 2100. That is a huge range, and it all depends on whether the West Antarctic Ice Sheet remains relatively stable or begins a slow but unstoppable collapse. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/high-tide-flood-risk-is-accelerating-putting-coastal-economies-at-risk-164481">High-tide flood risk is accelerating, putting coastal economies at risk</a>
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</em>
</p>
<hr>
<p>How the IPCC communicates this scientific debate will impact how <a href="https://www.ducks.ca/stories/conservator/rising-sea-levels-on-canadas-coasts/">coastal communities plan for sea-level rise</a>. Low-lying cities, like <a href="https://www.cnn.com/2021/08/01/africa/lagos-sinking-floods-climate-change-intl-cmd/index.html">Lagos, Nigeria</a>, could become uninhabitable by the end of the century due to sea-level rise, especially if the higher model estimates prove most prescient.</p>
<figure class="align-center ">
<img alt="Edge of the West Antarctic Ice Sheet" src="https://images.theconversation.com/files/414187/original/file-20210802-19-13frmz4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414187/original/file-20210802-19-13frmz4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414187/original/file-20210802-19-13frmz4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414187/original/file-20210802-19-13frmz4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414187/original/file-20210802-19-13frmz4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414187/original/file-20210802-19-13frmz4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414187/original/file-20210802-19-13frmz4.jpeg?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">The fate of the West Antarctic Ice Sheet lies with the Thwaites Glacier. If the front of the Thwaites breaks up, it would expose an even larger body of ice to warm waters.</span>
<span class="attribution"><span class="source">(Karen Alley)</span></span>
</figcaption>
</figure>
<p>The IPCC report will give policy-makers a better understanding of how climate change is affecting us today. This will be especially helpful for putting short-term adaptation strategies in place. </p>
<p>But as the science has improved, the outlook on future change has become more sobering, and the large uncertainties that remain mean substantial future work for climate scientists.</p><img src="https://counter.theconversation.com/content/165430/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alex Crawford receives funding through the Canada-150, Canada Excellence Research Chair (CERC), and Canada Research Chair (CRC) programs as well as the Natural Sciences and Engineering Research Council (NSERC).</span></em></p>
The latest report on climate science comes on the heels of heatwaves, wildfires, flooding and storms. It will help policy-makers act on plans to curb emissions or adapt to climate change.
Alex Crawford, Research Associate at the Centre for Earth Observation Science, Clayton H. Riddle Faculty of Environment, Earth, and Resources, University of Manitoba
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/162230
2021-06-24T12:58:03Z
2021-06-24T12:58:03Z
Solar geoengineering could limit global warming, but Canada should study risks and benefits first
<figure><img src="https://images.theconversation.com/files/407696/original/file-20210622-17-1hii20d.jpg?ixlib=rb-1.1.0&rect=46%2C23%2C5077%2C3344&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">If successful, solar geoengineering would would reduce the amount of sunlight that reaches the Earth's surface and warms the planet. </span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>The Swedish Space Corporation recently cancelled a <a href="https://www.keutschgroup.com/scopex">field test of a high altitude balloon</a>, intended to better understand solar geoengineering techniques that might be used to cool the Earth. </p>
<p>The proposed experiment, led by researchers at Harvard University and <a href="https://www.saamicouncil.net/news-archive/open-letter-requesting-cancellation-of-plans-for-geoengineering">opposed</a> by the Saami Council (an Indigenous organization) and Swedish environmental groups, was benign in terms of its potential impacts. Rather the opposition was over a more general concern about solar geoengineering itself, the implications of its deployment and the moral hazard that it presents by detracting from global efforts to address climate change through emissions reduction. </p>
<p>This leaves solar geoengineering research in a kind of limbo. There are concerns over its potential environmental and socio-political impacts, but there’s also hostility towards resolving some of these uncertainties through scientific research. </p>
<p>Aware of the need to find a way through this morass, the U.S. National Academies of Sciences <a href="https://www.nap.edu/catalog/25762/reflecting-sunlight-recommendations-for-solar-geoengineering-research-and-research-governance">released a report in March</a> that recommended the U.S. government invest up to $200 million over five years into <a href="https://doi.org/10.1146/annurev-earth-042711-105548">solar geoengineering research</a> to understand its risks and benefits. This report is significant not only because it signals a mainstreaming of the debate on solar geoengineering research, but also because of its thoughtful and balanced approach to a subject that has been fraught with controversies, such as the cancellation of the SCoPEx experiment.</p>
<p>Canadian climate policy <a href="https://www.cigionline.org/publications/developing-national-strategy-climate-engineering-research-canada/">has yet to address solar geoengineering</a>, but the <a href="https://publications.gc.ca/collections/collection_2020/eccc/En4-414-2020-eng.pdf">government acknowledges</a> the need to understand the implications of these hypothesized technologies. In developing its own approach to solar geoengineering research, the Canadian government would do well to heed the key takeaways from the National Academies of Sciences report.</p>
<h2>The reality beyond pop-culture</h2>
<p>Solar geoengineering covers a variety of Earth-cooling strategies, such as adding reflective particles to the upper atmosphere or manipulating clouds in the lower atmosphere. If successful, these techniques would reduce the amount of sunlight that reaches the Earth’s surface and warms the planet. </p>
<p>Solar geoengineering raises profoundly difficult governance issues due to its potential to impact large-scale human support systems such water availability, agriculture and energy on global scales. That said, solar geoengineering is unlikely to resemble its dystopian portrayal in <a href="https://www.imdb.com/title/tt1981128/">movies</a> and <a href="https://www.imdb.com/title/tt1706620/">television</a>.</p>
<p>Solar geoengineering is at best a <a href="https://www.belfercenter.org/publication/implications-paris-agreement-carbon-dioxide-removal-and-solar-geoengineering">complement to</a>, not a substitute for, emissions reduction. This is not a political statement, but reflects the inability of solar geoengineering to address key climate impacts, such as <a href="https://doi.org/10.1098/rsta.2012.0167">ocean acidification</a>, caused by the ocean’s increased absorption of carbon dioxide.</p>
<figure class="align-center ">
<img alt="A field of staghorn corals" src="https://images.theconversation.com/files/407699/original/file-20210622-21-15ywq1z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/407699/original/file-20210622-21-15ywq1z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407699/original/file-20210622-21-15ywq1z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407699/original/file-20210622-21-15ywq1z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407699/original/file-20210622-21-15ywq1z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407699/original/file-20210622-21-15ywq1z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407699/original/file-20210622-21-15ywq1z.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 quarter of the carbon dioxide released into the atmosphere is absorbed by the ocean, which makes the seawater more acidic. Coral skeletons are made from a type of calcium carbonate, which can’t form when ocean acidity surpasses a certain level. Solar geoengineering won’t address ocean acidification.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Solar geoengineering may temporarily lower or moderate the Earth’s temperature, but it’s unable to return the Earth’s climate to some prior state. Limiting changes in temperature and precipitation patterns requires limiting carbon dioxide emissions, and likely <a href="https://doi.org/10.3389/fclim.2019.00004">removing past emissions</a> from the atmosphere.</p>
<p>Despite its limitations, solar geoengineering could help <a href="https://doi.org/10.1080/14693062.2019.1623165">moderate the most extreme temperature changes</a> and provide governments, private enterprise, and civil society <a href="https://ssrn.com/abstract=1450781">more time</a> to mitigate emissions, remove carbon dioxide from the atmosphere and adapt to new climatic conditions. Yet the report points out that <a href="https://doi.org/10.1002/2016EF000407">we simply do not know enough</a> to determine whether solar geoengineering would be safe, effective and acceptable. A focused and co-ordinated program of research would address these uncertainties.</p>
<h2>Addressing the moral hazard</h2>
<p>Conducting research on solar geoengineering is neither neutral nor <a href="https://thebulletin.org/2008/05/20-reasons-why-geoengineering-may-be-a-bad-idea/">risk free</a>. There are <a href="https://www.jstor.org/stable/24113611">well-founded concerns</a> that research could divert attention, resources and political will away from mitigation efforts. It could <a href="https://doi.org/10.1002/wcc.296">create political momentum</a> and powerful constituencies that favour its deployment. But failing to do research also brings the risk of <a href="https://science.sciencemag.org/content/339/6125/1278">making uninformed decisions</a> in the future. </p>
<p>Research on solar geoengineering should not be undertaken <a href="https://doi.org/10.1002/2016EF000445">at the expense of decarbonization efforts</a> and should include clear “exit ramps” — predetermined criteria, such as low efficacy or unacceptable risks — for terminating research activities. Although those risks remain unclear, some research has suggested <a href="https://doi.org/10.1029/2020EF001595">weather patterns might change</a>, which could have impacts on things ranging from agriculture to biodiversity. Research activities should be directed towards <a href="https://doi.org/10.1016/j.cosust.2020.06.004">addressing knowledge gaps</a>, but should not be directed towards developing or deploying solar geoengineering.</p>
<figure class="align-right ">
<img alt="Children playing in a water fountain" src="https://images.theconversation.com/files/407697/original/file-20210622-20-18o479g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/407697/original/file-20210622-20-18o479g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=899&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407697/original/file-20210622-20-18o479g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=899&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407697/original/file-20210622-20-18o479g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=899&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407697/original/file-20210622-20-18o479g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1129&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407697/original/file-20210622-20-18o479g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1129&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407697/original/file-20210622-20-18o479g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1129&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Children cool off in water fountains in Montréal. The average temperature in the city will rise 0.5 C by 2035, meaning longer and hotter summers.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Because the decision-making environment surrounding solar geoengineering research is characterized by deep divisions (<a href="https://doi.org/10.1111/geoj.12116">conspiracy theories abound in this field</a>) within both expert and lay communities, considerable attention must be paid to governance of research. The research must ensure transparency — of research funding, methods and outcomes — be subject to robust oversight by governments, scientific institutions and scientists themselves, and <a href="https://doi.org/10.1007/s10584-013-0763-y">proactively inform and engage the public</a>. </p>
<p>Public trust in the motivations of scientists and credibility of outcomes will be crucial to ensuring that future debates on solar geoengineering proceed on the basis of publicly accepted science. Failure to address these issues could result in a unilateral deployment where one nation state or even possibly a private company could deploy geoengineering technologies. Without global involvement and collaborative governance, possible negative side effects might be ignored or intentionally distributed to benefit those who initiate it.</p>
<p>Understanding the full implications of solar geoengineering requires research be directed to scientific and technical matters, but also to the <a href="https://doi.org/10.3390/su10010269">social dimensions</a> of solar geoengineering. Solar geoengineering <a href="https://doi.org/10.1146/annurev-environ-102017-030032">raises profoundly difficult questions</a> respecting ethics, justice and the political and security aspects of a technology that intervenes in the climate at a global scale. </p>
<p>This requires a <a href="https://doi.org/10.1111/j.1467-7660.2011.01744.x">research program</a> that engages social scientists and humanists, as well as natural scientists. As intervening in the climate would have global implications, questions of consent and unequal impacts (economic, environmental and social) are raised not just in Canada, but internationally.</p>
<h2>A just path forward</h2>
<p><a href="https://www.cigionline.org/articles/case-climate-geoengineering-strategy/">Canada can, and should</a>, bring important perspectives to research on solar geoengineering. <a href="https://www.thecanadianencyclopedia.ca/en/article/middle-power">As a middle power</a>, with a credible emissions reduction plan and a long-standing commitment to international scientific cooperation, <a href="https://doi.org/10.1080/11926422.2012.674385">Canada is well positioned</a> to be an honest broker in international debates on solar geoengineering research and its potential role in addressing climate change. </p>
<p>Given its global nature, solar geoengineering requires international governance. Canada, which has always supported multilateralism over American exceptionalism, can play a crucial role in steering this discussion towards key international institutions.</p>
<p>As the SCoPEx controversy illustrates, bringing Indigenous voices and traditional knowledge systems to bear on solar geoengineering research questions is a moral and legal imperative that Canada can lead, on given the <a href="https://www.rcaanc-cirnac.gc.ca/eng/1331832510888/1609421255810">constitutional requirements for consultation in Canada</a>, as well as <a href="https://www.justice.gc.ca/eng/declaration/index.html">Canada’s embrace</a>, albeit hesitant, of the United Nations Declaration on the Rights of Indigenous Peoples.</p>
<p>Recognizing the need to research solar geoengineering is an acknowledgement of a <a href="https://doi.org/10.1073/pnas.1713456114">broader policy failure</a> to address climate change. A clear-eyed response to this failure requires Canada to redouble its efforts to reduce emissions, and not place false hope in unproven technological fixes. But the urgency of the current climate emergency also necessitates the responsible exploration of all options that may contribute to a more liveable planet.</p><img src="https://counter.theconversation.com/content/162230/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Burgess Langshaw Power is a PhD student at the Balsillie School of International Affairs (University of Waterloo), where he is studying the governance of climate altering technologies.</span></em></p><p class="fine-print"><em><span>Juan Moreno-Cruz receives funding from the Social Sciences and Humanities Research Council and the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Neil Craik is a Professor at the University of Waterloo and a Senior Fellow at the Centre for International Governance Innovation. He receives funding from the Social Sciences and Humanities Research Council of Canada.</span></em></p>
Solar geoengineering could theoretically cool the Earth to slow global warming, and it has been controversial. Still, countries should research its risks and benefits.
Burgess Langshaw Power, PhD Student, Global Governance program at the Balsillie School for International Affairs, University of Waterloo
Juan Moreno-Cruz, Canada Research Chair in Energy Transitions, University of Waterloo
Neil Craik, Professor of law, University of Waterloo
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/162779
2021-06-18T10:41:46Z
2021-06-18T10:41:46Z
Contrails from aeroplanes warm the planet – here’s how new low-soot fuels can help
<p>While aviation accounts for <a href="https://theicct.org/publications/co2-emissions-commercial-aviation-2018">2.4% of all emissions</a> from fossil fuel use globally, two-thirds of the sector’s warming effect depends on something other than its CO₂ emissions. And one of the most significant ways aviation contributes to global warming is through the clouds aeroplanes create in the upper atmosphere. </p>
<p>But, <a href="https://www.nature.com/articles/s43247-021-00174-y">in a new study</a>, researchers have shown that alternative fuels to the kerosene that aeroplanes typically burn can help.</p>
<p>At cruising altitudes where the atmosphere is cold and humid enough, contrails (short for condensation trails) form in the wake of aircraft. These are clouds made of ice crystals that are initially produced from the plane engine’s soot and water emissions – you’ll probably have seen them as white, puffy streaks in the sky on a clear day. When the atmosphere is especially cold and humid at high altitudes, these line-shaped contrails can last for many hours and spread to form vast webs of cirrus clouds, which look like white wisps of hair.</p>
<p>These clouds reflect the sun’s radiation back to space, cooling the atmosphere, but they can also trap infrared radiation reflected from the Earth. This process ultimately warms the atmosphere, as the warming effect exceeds the cooling. This is <a href="https://doi.org/10.1016/j.atmosenv.2020.117834">calculated</a> to be aviation’s largest current warming effect – nearly double that from historic CO₂ emissions.</p>
<figure class="align-center ">
<img alt="A blue sky with a contrail line and wispy cirrus clouds." src="https://images.theconversation.com/files/407015/original/file-20210617-17-yc3wrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/407015/original/file-20210617-17-yc3wrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407015/original/file-20210617-17-yc3wrn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407015/original/file-20210617-17-yc3wrn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407015/original/file-20210617-17-yc3wrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407015/original/file-20210617-17-yc3wrn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407015/original/file-20210617-17-yc3wrn.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">Contrails track the flight paths of aeroplanes, but can also spread out to form cirrus clouds.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/contrail-due-airliner-passing-earlier-diagonally-1532064569">Daniel Albach/Shutterstock</a></span>
</figcaption>
</figure>
<p>Reducing aviation’s climate impacts from contrails will depend on minimising soot particles from aeroplane exhausts. Aircraft exhaust plumes used to be smoky, as they contained a lot of soot. Modern engines are designed to reduce the heaviness of soot emissions, but the size and number of ice crystals that form depends on the large number soot of particles. There’s only so much more that can be achieved by cleaning aeroplane exhausts – future efforts must focus on the fuel itself.</p>
<p>Impurities such as napthalene, which are naturally present in aircraft fossil fuels like kerosene, are called aromatic compounds. These are carbon ring-shaped chemical structures that form the building blocks of soot particles. <a href="https://theconversation.com/flight-to-greener-aviation-fuel-has-hit-turbulence-heres-why-7274">Biofuels</a> made from crops and waste vegetable oils, and synthetic fuels made using renewable electricity, hydrogen and CO₂, are designed to reduce the carbon footprint of flying.</p>
<p>There are no aromatic impurities in these fuels, meaning <a href="https://doi.org/10.1038/nature21420">fewer soot particles</a> are generated when they’re burned. In the new study, the researchers found that they also generate fewer (but larger) ice crystals in the atmosphere during flight. This, in turn, makes the contrails and the cirrus clouds they form warm the Earth less.</p>
<h2>The future of flying</h2>
<p>Currently, aeroplanes can only fuel up with kerosene or kerosene-biofuel blends. The authors of the new paper found that blends of fuels with low aromatic impurities cut ice crystal formation by between 50 and 70%. In another paper, researchers <a href="https://doi.org/10.1038/s41612-018-0046-4">predicted</a> that would equate to a reduction in the overall warming effect of contrails by approximately 20%-50%. Flights are likely to be permitted to run on pure biofuels at some point in the future, so the potential reduction in the warming caused by aviation could be even greater.</p>
<p>The new study’s findings suggest that sustainable fuel blends offer a win-win situation for lowering aviation’s CO₂ output and its production of contrail cirrus clouds. </p>
<p>Other solutions, such as electric flight, are only likely to be possible for very short routes. Even hydrogen-fuelled aircraft may only be developed to manage medium distances. Both technologies will take more than a decade to mature before they can be introduced into the global aircraft fleet. Long-haul aviation is likely to depend on liquid kerosene-type fuels for the foreseeable future.</p>
<p>Another option is for pilots to avoid parts of the atmosphere where contrails are more likely to form. On a flight-by-flight basis though, navigating to avoid these regions would almost certainly increase the flight’s CO₂ emissions. Weather models also <a href="https://doi.org/10.3390/aerospace7120169">cannot predict</a> the areas where contrails will form with enough accuracy.</p>
<p>Of course, the financial costs of developing and distributing biofuels and synthetic fuels at sufficient scale will probably be large, and may increase the costs of flying. In all likelihood, governments will need to mandate a phase-out of fossil-based kerosene and provide large incentives for airlines to switch. But time is running short to decarbonise flying, and this is an effective option that airlines can develop straight away to reduce the industry’s overall climate impact.</p><img src="https://counter.theconversation.com/content/162779/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Simon Lee receives funding from the UK Department for Transport and EU Horizon 2020.</span></em></p>
Soot from aeroplane exhausts can linger in the atmosphere, seeding ice clouds which trap heat.
David Simon Lee, Professor of atmospheric science, Aviation and Climate Research Group Leader, Manchester Metropolitan University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/157828
2021-03-30T11:36:50Z
2021-03-30T11:36:50Z
Solar geoengineering is worth studying but not a substitute for cutting emissions, study finds
<figure><img src="https://images.theconversation.com/files/392061/original/file-20210327-13-r8qzcl.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C5405%2C3018&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Solar geoengineering could mean taking steps to alter the formation of clouds.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/flying-above-the-clouds-royalty-free-image/1158077392">Matt Dutcher/Getty Images</a></span></figcaption></figure><p><em>A new report from the National Academies of Sciences, Engineering and Medicine <a href="https://www.nap.edu/catalog/25762/reflecting-sunlight-recommendations-for-solar-geoengineering-research-and-research-governance">tackles a controversial question</a>: Is solar geoengineering – an approach designed to cool the Earth by reflecting sunlight back into space or modifying clouds – a potential tool for countering climate change?</em></p>
<p><em>The report, produced by a committee of <a href="https://www.nap.edu/read/25762/chapter/1#v">16 experts from diverse fields</a>, does not take a position but concludes that the concept should be studied. It calls for creating a multidisciplinary research program, in coordination with other countries and managed by the <a href="https://www.globalchange.gov/">U.S. Global Change Research Program</a>, that seeks to fill in the many knowledge gaps on this issue.</em></p>
<p><em>The study emphasizes that such research is not a substitute for cutting greenhouse gas emissions and should be a minor part of the U.S. response to climate change. It notes that “engineering the climate” would not address the root cause of climate change – greenhouse gas emissions from human activities. And it calls for a research program that draws on physical science, social science and ethics and includes public input.</em> </p>
<p><em>These perspectives from three members of the study committee underline the complexity of this issue.</em></p>
<p></p><hr><p></p>
<h2>Three options, many questions</h2>
<p><strong>James W. Hurrell, Professor and Scott Presidential Chair of Environmental Science and Engineering, Colorado State University</strong></p>
<p>Solar geoengineering strategies are very controversial within and beyond the climate science community. It is a major step forward to have 16 experts from different disciplines agree that now is the time to establish a research program on this topic. Our committee traveled a long road to reach this recommendation, working through many complex and contentious issues to reach consensus, but we did it collegially and productively. Each of us learned a great deal. </p>
<p>The three options we considered raise many questions: </p>
<p>– <a href="https://www.nap.edu/read/25762/chapter/4#34">Stratospheric aerosol injection</a> would increase the number of small reflective particles (aerosols) in the upper atmosphere to increase reflection of sunlight back into space. While strong evidence exists that this approach <a href="https://www.nasa.gov/topics/earth/features/stratospheric-aerosols.html">can induce cooling at a global scale</a>, there is <a href="https://www.energy.gov/sites/prod/files/2019/03/f61/Chapter%205.pdf">limited understanding</a> of how cooling potential relates to the amounts of injected aerosols, their location and type, and the ensuing regional climate responses and impacts. </p>
<p>– <a href="https://www.nap.edu/read/25762/chapter/4#34">Marine cloud brightening</a> would add materials to low clouds over the ocean to make them more reflective. Water vapor in clouds condenses into droplets when it comes into contact with particles, such as salt; adding particles produces more droplets, making the clouds more reflective. </p>
<p>Where and by how much the brightness of clouds can be modified, and whether feedback processes will mask or amplify some of the effects, are important research questions. Key processes occur at scales too small to include directly into the current generation of global climate models, and these process uncertainties will need to be reduced in order to develop reliable projections of climate impacts. </p>
<p>– <a href="https://www.nap.edu/read/25762/chapter/4#35">Cirrus cloud thinning</a> would seek to reduce the formation of <a href="https://scied.ucar.edu/image/cirrus-clouds">wispy, thin clouds</a> that retain heat radiating upward from Earth’s surface. The efficacy of this approach is unknown because of very limited understanding of cirrus cloud properties and the microphysical processes determining how cirrus clouds may be altered. Existing climate model simulations have yielded contradictory results. </p>
<p>Given the risks of rapid warming and its impacts, it is important to consider a portfolio of response options, and to understand as quickly and efficiently as possible whether solar geoengineering could be a reasonably safe and effective option. A transdisciplinary, coordinated and well-governed research program might prove that more investment is warranted. Or it could indicate that solar geoengineering should not be considered further. The key point is that either outcome will be guided by sound science.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/392059/original/file-20210327-19-1rb7n1f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/392059/original/file-20210327-19-1rb7n1f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/392059/original/file-20210327-19-1rb7n1f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=904&fit=crop&dpr=1 600w, https://images.theconversation.com/files/392059/original/file-20210327-19-1rb7n1f.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=904&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/392059/original/file-20210327-19-1rb7n1f.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=904&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/392059/original/file-20210327-19-1rb7n1f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1136&fit=crop&dpr=1 754w, https://images.theconversation.com/files/392059/original/file-20210327-19-1rb7n1f.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1136&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/392059/original/file-20210327-19-1rb7n1f.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1136&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 new report examines three solar geoengineering options: stratospheric aerosol injection, marine cloud brightening and cirrus cloud thinning.</span>
<span class="attribution"><a class="source" href="https://www.nationalacademies.org/news/2021/03/new-report-says-u-s-should-cautiously-pursue-solar-geoengineering-research-to-better-understand-options-for-responding-to-climate-change-risks">NAS</a></span>
</figcaption>
</figure>
<p></p><hr><p></p>
<h2>A thoughtful and inclusive process</h2>
<p><strong>Ambuj D. Sagar, Founding Head, School of Public Policy, and Professor of Policy Studies, The Indian Institute of Technology Delhi</strong></p>
<p>Few climate issues are as polarizing as solar geoengineering, and for good reason. To many, even considering it could dilute efforts to cut emissions. It also reinforces the notion that as a society we are willing to place our faith in technology to solve our self-inflicted problems. </p>
<p>But refusing to engage with solar geoengineering also raises questions. Can we be sure that we won’t need it in the future? What if greenhouse warming generates horrendous climate impacts? And if it turns out that solar geoengineering is not technically feasible or socially acceptable, should we not learn that now? </p>
<p>This report recognizes that there is value in understanding more about the feasibility, acceptance, risks, ethics and governance of solar geoengineering to inform decision-making. But it also calls for a measured, nuanced and integrative approach. And it makes the point that exploring solar geoengineering should not compromise research or action on climate mitigation and adaptation.</p>
<p>Public engagement and participation, and insights from various disciplines, are key to carrying out effective research on solar geoengineering. At the same time, suitable expertise and institutional arrangements are needed to engage better with this complex topic. We need to understand how to effectively enhance such participation and strengthen such capacity.</p>
<p>Paying attention to these issues will open the door to including perspectives and researchers from the global south and other communities that often are marginalized. It also will help make the research agenda more robust and help people better understand potential risks around the world from solar geoengineering. A strong and inclusive research program should also fully involve developing countries and other relevant communities in exploring governance models for solar geoengineering. </p>
<p>Our panel recommended that the proposed U.S. research program be carried out in coordination with other countries. We hope this approach will spur deeper engagement worldwide, especially by developing countries that need to be part of global conversations and decisions on this issue. </p>
<p>Overall, I hope that perspectives and approaches presented in this report will catalyze a thoughtful and socially robust research program and equally thoughtful deliberations by scholars, policymakers and citizens on this thorny topic. </p>
<figure class="align-center ">
<img alt="Volcanic cloud over Clark Air Base, Philippines." src="https://images.theconversation.com/files/392060/original/file-20210327-25-5ta0cg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/392060/original/file-20210327-25-5ta0cg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=625&fit=crop&dpr=1 600w, https://images.theconversation.com/files/392060/original/file-20210327-25-5ta0cg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=625&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/392060/original/file-20210327-25-5ta0cg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=625&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/392060/original/file-20210327-25-5ta0cg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=786&fit=crop&dpr=1 754w, https://images.theconversation.com/files/392060/original/file-20210327-25-5ta0cg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=786&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/392060/original/file-20210327-25-5ta0cg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=786&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The 1991 eruption of Mt. Pinatubo in the Philippines injected into Earth’s stratosphere vast quantities of aerosol particles, which scattered and reflected sunlight, reducing Earth’s average global temperature by about 1 degree Fahrenheit over the next 15 months. Afterward, however, temperatures resumed rising.</span>
<span class="attribution"><a class="source" href="https://web.archive.org/web/20100531212028/http://vulcan.wr.usgs.gov/Volcanoes/Philippines/Pinatubo/images.html">Richard Hoblitt/USGS</a></span>
</figcaption>
</figure>
<p></p><hr><p></p>
<h2>Broadening the discussion</h2>
<p><strong>Marion Hourdequin, Professor of Philosophy, Colorado College</strong></p>
<p>Geoengineering evolved <a href="https://doi.org/10.1002/2016EF000521">from a fringe concept to a serious research topic</a> less than 20 years ago, and today solar geoengineering technologies are largely in the idea stage. Computer modeling simulations and <a href="https://www.usgs.gov/natural-hazards/volcano-hazards/volcanoes-can-affect-climate">natural analogs such as volcanoes</a> indicate that adding reflective aerosols to the stratosphere or increasing the “brightness” of marine clouds could have cooling effects. However, there are risks and uncertainties associated with these approaches, and the potential benefits – which may not be evenly distributed around the globe – are not well understood. </p>
<p>For example, scientists know very little about the regional effects of different solar geoengineering strategies. And researchers are just starting to explore the ecological, social, political, economic and ethical dimensions of these approaches.<br>
What’s more, many people in the U.S. and the world are unaware that research is moving forward and <a href="https://www.keutschgroup.com/scopex">outdoor experiments have been proposed</a>. So far, discussions about solar geoengineering have been concentrated among a relatively small group of researchers, primarily from <a href="https://www.nap.edu/read/25762/chapter/4?term=diversity#37">North America and Europe</a>. </p>
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<p>But like climate change itself, solar geoengineering would affect everyone. The technologies that our committee considered would have global and multigenerational effects. With this in mind, now is the time for broader and more inclusive conversations about how solar geoengineering should be studied and governed – and whether or not it should be seriously considered. These conversations need to include climate-vulnerable communities, Indigenous peoples and nations of the global south.</p>
<p>Our committee’s report calls for a program that weaves together multidisciplinary research, public and stakeholder engagement, and thoughtful limits and guidelines for research. This program should facilitate cooperation and capacity building, support a more demographically and geographically diverse research community, enable equitable participation and prioritize strategies that build trust, transparency and legitimacy.</p>
<p>Geoengineering raises big technical, social and ethical questions that should be informed by research but can’t be adequately answered by a small set of experts. And regardless of what we learn through geoengineering research, one thing is clear: Reducing emissions, decarbonizing economies and supporting adaptation to current and future climate impacts need to take center stage.</p><img src="https://counter.theconversation.com/content/157828/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Is it time to take drastic steps to modify Earth’s climate to avoid catastrophic warming? A panel of experts says the idea deserves study.
James W. Hurrell, Professor and Scott Presidential Chair in Environmental Science and Engineering, Colorado State University
Ambuj D Sagar, Founding Head, School of Public Policy, and Vipula and Mahesh Chaturevdi Professor of Policy Studies, The Indian Institute of Technology Delhi
Marion Hourdequin, Professor of Philosophy, Colorado College
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/152736
2021-01-28T13:30:24Z
2021-01-28T13:30:24Z
Thawing permafrost is full of ice-forming particles that could get into atmosphere
<figure><img src="https://images.theconversation.com/files/380952/original/file-20210127-13-mp8t1c.jpg?ixlib=rb-1.1.0&rect=0%2C62%2C5184%2C2498&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Permafrost is thawing across the Arctic, releasing microbes and organic materials that have been trapped in the frozen ground for thousands of years.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Road_dip_caused_by_melting_permafrost.jpg">NOAA via Wikimedia Commons</a></span></figcaption></figure><p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em></p>
<h2>The big idea</h2>
<p>Permafrost – frozen soil in the far north – <a href="https://doi.org/10.1029/2010EO260001">is thawing</a>, <a href="https://www.nationalgeographic.com/science/2020/02/arctic-thawing-ground-releasing-shocking-amount-dangerous-gases/">releasing greenhouse gases</a> and <a href="https://www.npr.org/sections/goatsandsoda/2018/01/24/575974220/are-there-zombie-viruses-in-the-thawing-permafrost">long-lost microbes</a>. But one thing that scientists have not studied extensively is whether permafrost contains certain kinds of particles that could affect clouds and weather.</p>
<p>As <a href="https://scholar.google.com/citations?user=SDZfxGQAAAAJ&hl=en&oi=ao">atmospheric</a> <a href="http://chem.atmos.colostate.edu/k_members.html">scientists</a>, we found in a 2021 study that thawing permafrost contains lots of <a href="https://doi.org/10.1088/1748-9326/ab87d3">microscopic ice-nucleating particles</a>. These particles make it <a href="https://en.wikipedia.org/wiki/Ice_nucleus">easier for water droplets to freeze</a>; and if the ones in permafrost get airborne, they could affect Arctic clouds.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/380989/original/file-20210127-17-llb6qu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The study author using a drill to take a sample of permafrost in a large tunnel." src="https://images.theconversation.com/files/380989/original/file-20210127-17-llb6qu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/380989/original/file-20210127-17-llb6qu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=801&fit=crop&dpr=1 600w, https://images.theconversation.com/files/380989/original/file-20210127-17-llb6qu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=801&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/380989/original/file-20210127-17-llb6qu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=801&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/380989/original/file-20210127-17-llb6qu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1007&fit=crop&dpr=1 754w, https://images.theconversation.com/files/380989/original/file-20210127-17-llb6qu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1007&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/380989/original/file-20210127-17-llb6qu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1007&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ancient permafrost can be accessed in deep tunnels underground.</span>
<span class="attribution"><span class="source">Jessie Creamean</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>In the summer of 2018, one of us, <a href="https://scholar.google.com/citations?user=SDZfxGQAAAAJ&hl=en&oi=ao">Jessie Creamean</a>, went to Fairbanks, Alaska, and collected samples of permafrost from a research tunnel deep underground. These samples ranged from <a href="https://doi.org/10.1088/1748-9326/ab87d3">18,000 to 30,000 years old</a>, and our team tested them to see how many ice-nucleating particles are hiding in permafrost.</p>
<p>It turns out permafrost <a href="https://doi.org/10.1088/1748-9326/ab87d3">contains a ton of them</a> – up to 100 million highly active individual particles per gram of mostly dead microbes and pieces of plants. This density is on par with what is found in fertile soils, which are some of the <a href="https://doi.org/10.1016/j.envint.2020.106197">most concentrated sources of ice-nucleating particles on Earth</a>. Everywhere in the world, ice-nucleating particles typically play a major role in <a href="https://doi.org/10.1175/AMSMONOGRAPHS-D-16-0006.1">cloud behavior</a>, and the strength of that effect is still being studied.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/380956/original/file-20210127-23-1v3bmj0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A beaker containing a sample of permafrost." src="https://images.theconversation.com/files/380956/original/file-20210127-23-1v3bmj0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/380956/original/file-20210127-23-1v3bmj0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/380956/original/file-20210127-23-1v3bmj0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/380956/original/file-20210127-23-1v3bmj0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/380956/original/file-20210127-23-1v3bmj0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=497&fit=crop&dpr=1 754w, https://images.theconversation.com/files/380956/original/file-20210127-23-1v3bmj0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=497&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/380956/original/file-20210127-23-1v3bmj0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=497&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This 18,000-year-old permafrost sample contains millions of ice-nucleating particles per gram.</span>
<span class="attribution"><a class="source" href="http://chem.atmos.colostate.edu/k_home.html">Thomas Hill</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Why it matters</h2>
<p>No one yet knows whether ice-nucleating particles from permafrost are getting into the atmosphere and affecting clouds. But the theory of how ice-nucleating particles change clouds is understood.</p>
<p>Clouds are made up of billions of tiny <a href="https://scied.ucar.edu/learning-zone/clouds/how-clouds-form">water droplets or ice crystals</a>, often a mix of both. A cloud is like a forest of trees: All water droplets of the cloud require a seed – a tiny aerosol particle – to form and grow on. Almost any little speck of material from the land or the ocean can be the seed of a liquid cloud droplet. Because of their unique ability to line up water molecules into an icelike grid, they help supercooled liquid in a cloud to freeze at warmer temperatures. </p>
<p>Ice-nucleating particles are extremely good at <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ice-nuclei">forming small ice crystals</a> – a rare skill found in less than <a href="https://doi.org/10.1073/pnas.0910818107">1 in a million of all the particles</a> floating around in the air. Ice-nucleating particles can be <a href="https://doi.org/10.5194/acp-16-9067-2016">mineral dust from deserts</a>, specks of <a href="https://doi.org/10.5194/acp-16-7195-2016">soil from farm fields</a> or – like what we found in the permafrost – <a href="https://doi.org/10.1175/AMSMONOGRAPHS-D-16-0006.1">bacteria</a> and bits of biological material from <a href="https://doi.org/10.1029/2019GL083039">oceans</a> or plants. </p>
<p>The ability to easily form ice has big consequences for clouds and weather.</p>
<p>Most of the time, airborne water droplets need to freeze before they can fall to the ground as snow or rain. Ice-nucleating particles allow cloud ice to form at warmer air temperatures than normal, up to around 28 degrees Fahrenheit. Without these particles, a water droplet can supercool to about <a href="https://doi.org/10.1175/AMSMONOGRAPHS-D-16-0006.1">negative 36 F before freezing</a>. When ice-nucleating particles are in a cloud, water droplets freeze more easily. This can cause the cloud to rain or snow and disappear earlier, and reflect less sunlight. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/380958/original/file-20210127-17-11lm5sv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Thawing permafrost forming a lake." src="https://images.theconversation.com/files/380958/original/file-20210127-17-11lm5sv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/380958/original/file-20210127-17-11lm5sv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/380958/original/file-20210127-17-11lm5sv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/380958/original/file-20210127-17-11lm5sv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/380958/original/file-20210127-17-11lm5sv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/380958/original/file-20210127-17-11lm5sv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/380958/original/file-20210127-17-11lm5sv.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">As permafrost thaws, ice-nucleating particles are getting into rivers, lakes and eventually the ocean.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Permafrost_Thaw_(14413865677).jpg#/media/File:Permafrost_Thaw_(14413865677).jpg">National Park Service/C.Ciancibelli via Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>What still isn’t known</h2>
<p>Our work found there are a lot of these ice-nucleating particles in thawing permafrost, which is important because permafrost covers <a href="https://nsidc.org/cryosphere/sotc/permafrost.html">24% of the exposed land surface in the Northern Hemisphere</a>. The question now is whether these particles are getting into the atmosphere or not. No other researchers that we’re aware of have looked at permafrost’s effect on cloud formation, or the mechanisms by which ice-nucleating particles from permafrost become airborne. </p>
<p>We hypothesize that ice-nucleating particles from thawing permafrost could get into lakes and rivers, make their way to coastal Arctic Ocean waters and spread over large areas. Then, <a href="https://www.pnas.org/content/113/21/5797">winds could eject these ice-nucleating particles into the air</a>, where they could enhance the freezing of clouds and affect weather. </p>
<p>There are still many unknowns and a lot of work to do.</p>
<h2>What’s next</h2>
<p>We are teaming up with colleagues from the Cold Regions Research and Engineering Laboratory in Fairbanks and the National Center for Atmospheric Research in Boulder, Colorado, to set out for a six-week expedition to the Alaskan Arctic tundra. We will collect hundreds of samples of permafrost, lake water, river water, coastal ocean water and air samples to see whether ice-nucleating particles from permafrost are present, and in what amounts. Our goal is to use these findings in models to predict how thawing permafrost could alter the region’s clouds.</p><img src="https://counter.theconversation.com/content/152736/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jessie Creamean receives funding for this work from the National Science Foundation (Award OPP-1946657).</span></em></p><p class="fine-print"><em><span>Thomas Hill receives funding for this work from the National Science Foundation (Award OPP-1946657). </span></em></p>
New research shows that permafrost contains huge amounts of particles that make it easier for cloud moisture to freeze. Thawing permafrost is releasing these ice-nucleating particles.
Jessie Creamean, Research Scientist, Colorado State University
Thomas Hill, Research Scientist, Colorado State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/140812
2020-09-11T10:01:39Z
2020-09-11T10:01:39Z
Why clouds are the missing piece in the climate change puzzle
<figure><img src="https://images.theconversation.com/files/357535/original/file-20200910-15-1ds0rno.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4752%2C3165&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/E9aetBe2w40">Sam Schooler/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>How much our world <a href="https://blogs.scientificamerican.com/hot-planet/global-warming-how-hot-exactly-is-it-going-to-get/">will warm this century</a> depends on the actions we take in coming decades. In order to keep global temperature rise below 1.5°C and avoid dangerous levels of warming, governments need to know how much carbon they can emit, and over what timeframe.</p>
<p>But current climate models don’t agree on where that threshold lies. In <a href="https://doi.org/10.1088/1748-9326/ab97c9">new research</a>, we discovered one of the reasons why there is such a large range of estimates for how much carbon can be safely emitted: the uncertain behaviour of clouds. In some climate models, clouds strongly amplify warming. In others, they have a neutral effect or even dampen warming slightly. So why are clouds likely to play such a pivotal role in deciding our fate?</p>
<p>Projections by climate models typically reveal global temperatures rising almost in tandem with the total amount of carbon emitted over time. This is represented by the black line in the graph below. To avoid exceeding a certain level of warming, the world needs to limit how much carbon is emitted so that it remains within a certain carbon budget. In climate models where clouds amplify warming, this carbon budget is smaller (red dashed line and arrow). Where clouds have a near neutral or damping effect, the carbon budget is larger (blue dashed line and arrow).</p>
<p><strong>Remaining carbon budgets in climate model projections</strong></p>
<figure class="align-center ">
<img alt="Graph showing relationship between cumulative emissions and global temperature, explained in previous paragraph." src="https://images.theconversation.com/files/346677/original/file-20200709-42-19vqpzk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/346677/original/file-20200709-42-19vqpzk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=493&fit=crop&dpr=1 600w, https://images.theconversation.com/files/346677/original/file-20200709-42-19vqpzk.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=493&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/346677/original/file-20200709-42-19vqpzk.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=493&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/346677/original/file-20200709-42-19vqpzk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=619&fit=crop&dpr=1 754w, https://images.theconversation.com/files/346677/original/file-20200709-42-19vqpzk.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=619&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/346677/original/file-20200709-42-19vqpzk.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=619&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Paulo Ceppi</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Why are clouds so important?</h2>
<p>Clouds can act like a parasol, cooling the Earth by reflecting sunlight away from the planet’s surface and back into space. But they can also act like an insulating blanket, warming the Earth by preventing some of the heat in our atmosphere from escaping into space as infrared radiation. This “blanket” effect is particularly noticeable during the winter, when cloudy nights are typically much warmer than cloud-free ones.</p>
<p>Which of these two effects dominates – parasol or blanket – depends on the altitude and thickness of the clouds. As a general rule, the higher a cloud is, the more effective it is at preventing heat from escaping into space. The thicker a cloud is, the better it is at reflecting sunlight away from Earth’s surface.</p>
<p>High, thin clouds let sunlight through while effectively preventing heat from escaping to space as infrared radiation, providing a net warming effect. Low, thick clouds strongly reflect sunlight, while having little impact on infrared radiation escaping to space, creating a net cooling effect.</p>
<p>As the atmosphere contains far more low, thick clouds than high, thin clouds, the parasol effect dominates and our planet would be much hotter if clouds did not exist.</p>
<figure class="align-center ">
<img alt="Diagram showing how different clouds trap heat or reflect sunlight, as explained two paragraphs prior." src="https://images.theconversation.com/files/346673/original/file-20200709-87080-1iac67g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/346673/original/file-20200709-87080-1iac67g.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=339&fit=crop&dpr=1 600w, https://images.theconversation.com/files/346673/original/file-20200709-87080-1iac67g.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=339&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/346673/original/file-20200709-87080-1iac67g.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=339&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/346673/original/file-20200709-87080-1iac67g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=426&fit=crop&dpr=1 754w, https://images.theconversation.com/files/346673/original/file-20200709-87080-1iac67g.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=426&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/346673/original/file-20200709-87080-1iac67g.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=426&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Thick, low clouds tend to act as a parasol, while high, thin clouds act as a blanket.</span>
<span class="attribution"><span class="source">Paulo Ceppi</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>The clouds are changing</h2>
<p>Global warming is expected to cause changes in the amount of cloud cover, and the height and thickness of these clouds in the future, shifting the balance between the parasol and blanket effects of clouds. The knock-on effect this will have on temperature is known as cloud feedback. Climate change projections cannot ignore cloud feedback, as even relatively small changes in cloud properties can have significant implications for global temperature.</p>
<p>To predict how clouds will change in the future, <a href="https://doi.org/10.1002/wcc.465">our research</a> combines evidence from observations and climate models with theoretical understanding of cloud physics. Taken together, this tells us that clouds are more likely to amplify global warming than they are to dampen it for two reasons. </p>
<p>First, the cover of low clouds is expected to decrease in the tropics as global temperatures rise, reducing their parasol effect. Second, it is well understood that high clouds will move into higher regions of the atmosphere as it warms, making them more effective blankets. These warming effects may be mitigated slightly by an increase in the thickness of clouds at high latitudes only, particularly over the Southern Ocean around Antarctica, but this will not cancel out the overall warming effect.</p>
<p>While we do know that clouds will likely amplify global warming, there is still a great deal of uncertainty about how strong this effect will be. Here climate models are of little help, as they can only simulate the bulk properties of the atmosphere over scales of tens of kilometres and several hours. Tiny cloud droplets form and evaporate in minutes. Models miss these small-scale details, but they’re needed for accurate predictions.</p>
<p>Climate models have to resort to simplifications in order to represent clouds, which introduces error. As different models make different simplifications in their portrayal of cloud processes, they also make different predictions of the cloud feedback, which results in a range of global warming projections and differences in our remaining carbon budget. For a given future carbon emissions scenario, clouds are the single most important factor behind the differences in future warming predicted between models.</p>
<h2>Should we be worried?</h2>
<p>Climate sensitivity, the amount of long-term global warming expected if we double the amount of carbon in the atmosphere, is currently estimated to lie between <a href="https://www.ipcc.ch/report/ar5/wg1/summary-for-policymakers/">1.5° and 4.5°C</a>. This consequences of this level of warming are already disturbing, but several new climate models currently being developed by world-leading researchers are projecting warming <a href="https://doi.org/10.1029/2019GL085782">in excess of 5°C</a>. These new models also feature an improved representation of cloud processes, so this seems to suggest that global warming could be even worse than we thought.</p>
<hr>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/just-how-hot-will-it-get-this-century-latest-climate-models-suggest-it-could-be-worse-than-we-thought-137281">Just how hot will it get this century? Latest climate models suggest it could be worse than we thought</a>
</strong>
</em>
</p>
<hr>
<p>Thankfully, there are <a href="https://doi.org/10.1126/sciadv.aaz9549">alternative projections</a> that point towards more moderate warming. The same models with the highest long-term warming also overestimated warming trends that have already been observed. In the meantime, further research efforts are underway to pin down the role of clouds in climate sensitivity.</p>
<p>It is clear that our planet will continue to warm as we carry on emitting carbon into the atmosphere. But by how much will remain written in the clouds.</p><img src="https://counter.theconversation.com/content/140812/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paulo Ceppi receives funding from the Natural Environment Research Council. </span></em></p><p class="fine-print"><em><span>Ric Williams receives funding from the Natural Environment Research Council.</span></em></p>
Clouds can act as both blanket and parasol – warming our atmosphere at the same time as cooling it. But which effect will dominate?
Paulo Ceppi, Lecturer in Climate Science, Imperial College London
Ric Williams, Professor of Ocean Sciences, University of Liverpool
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/143402
2020-08-13T12:07:07Z
2020-08-13T12:07:07Z
Why does some rain fall harder than other rain?
<figure><img src="https://images.theconversation.com/files/352560/original/file-20200812-18-1v5ghbk.jpg?ixlib=rb-1.1.0&rect=20%2C0%2C2674%2C1729&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A downpour or a drizzle: What causes the difference?</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/rainbow-in-rain-royalty-free-image/122286751?adppopup=true"> David Pinzer Photography/Moment via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>Why does some rain fall harder than other rain? – Naomi B., age 9, San Fancisco, California</strong></p>
</blockquote>
<hr>
<p>There are some days when the rain falls peacefully and gently, nourishing the Earth. But on some other days the rain comes down in a torrential downpour that <a href="https://ges.umbc.edu/halverson/">meteorologists like me</a> call a cloudburst. Standing outside in one of these intense rainstorms can feel like being smothered in a heavy, wet towel. These storms can flood the lands below them and lead to great destruction.</p>
<p>So what causes this difference?</p>
<p>All rain comes from a combination of two things: moisture in the air – usually in the form of clouds – and currents of air moving upwards. As moist air rises up through a cloud, the air cools and the water in it turns into tiny raindrops.</p>
<p>This is the same thing that happens when you can <a href="https://www.loc.gov/everyday-mysteries/item/why-do-i-see-my-breath-when-its-cold-outside/">see your breath on a cold evening</a>. The temperature change from warm to cool causes water droplets to form in your breath. </p>
<p>In a cloud, these tiny raindrops are very light and float as the rising air pushes them up. But the higher they go, the larger and heavier they get. Eventually, they get so heavy that they fall to the Earth as rain.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/352061/original/file-20200810-18-1sa6tnv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="People cross a street holding umbrellas and in long coats during a winter storm in Philadelphia." src="https://images.theconversation.com/files/352061/original/file-20200810-18-1sa6tnv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/352061/original/file-20200810-18-1sa6tnv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/352061/original/file-20200810-18-1sa6tnv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/352061/original/file-20200810-18-1sa6tnv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/352061/original/file-20200810-18-1sa6tnv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/352061/original/file-20200810-18-1sa6tnv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/352061/original/file-20200810-18-1sa6tnv.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">All-day drizzles come from steady storms that don’t have much upward wind flow.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Winter-Storm/78d6c8efa1954f2cb9decc3bb2b770fd/89/0">AP Photo/Matt Rourke</a></span>
</figcaption>
</figure>
<h2>Cold air storms are steady and slow</h2>
<p>Cold air can hold much less moisture than warm air, so wintertime clouds don’t have much water in them; they are <a href="https://en.wikipedia.org/wiki/Nimbostratus_cloud">thin and layered rather</a> than puffy and tall and full of water.</p>
<p>Since cold air likes to sink to the ground, it’s difficult to get that air to rise quickly, so these wintertime clouds have only gentle upward air currents. As these slow currents sweep up through the thin clouds that don’t have much moisture, small raindrops form. Gravity easily pulls them down against the air current before they get too big. When clouds are thin and the air is moving slowly, you get nice calm rain.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/352058/original/file-20200810-20-1zyxdz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large mushroom shaped cloud formation against a blue sky in New Mexico" src="https://images.theconversation.com/files/352058/original/file-20200810-20-1zyxdz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/352058/original/file-20200810-20-1zyxdz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/352058/original/file-20200810-20-1zyxdz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/352058/original/file-20200810-20-1zyxdz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/352058/original/file-20200810-20-1zyxdz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/352058/original/file-20200810-20-1zyxdz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/352058/original/file-20200810-20-1zyxdz.jpeg?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">Massive thunderstorms called supercells can form when the right weather ingredients come together.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Thunderstorm#/media/File:Chaparral_Supercell_2.JPG">Greg Lundeen/NOAA</a></span>
</figcaption>
</figure>
<h2>Thunderstorms and big winter storms are quick and intense</h2>
<p>Hard rainstorms happen when there is a lot of moisture in the air and the air moves upwards very fast. Summer thunderstorms are the perfect example. </p>
<p>The warm, moist air rises very quickly – like a hot air balloon – and can be moving <a href="https://www.koaa.com/news/covering-colorado/just-how-fast-does-an-updraft-need-to-be-to-create-colorados-record-breaking-hailstone">as fast as 30 to 40 miles per hour</a>. The air also holds <a href="https://www.lsop.colostate.edu/wp-content/uploads/sites/6/2014/10/WhyDoesWarmAirHoldMoreWater.pdf">much more moisture than winter clouds</a> – up to five times as much.</p>
<p>All of this creates <a href="https://en.wikipedia.org/wiki/Cumulonimbus_cloud">very tall, thick clouds that are full of moisture</a>. Water droplets form quickly as the air moves up through the clouds. But since the wind is blowing upwards so fast, the droplets can get huge before gravity drags them down to Earth. When the weight of all the water droplets gets to be too much for the wind, the wind current collapses, and all the raindrops in the cloud come crashing down at once. These are summer thunderstorms.</p>
<p>Thunderstorms can drop one, two or even three inches of rain in <a href="https://en.wikipedia.org/wiki/Flash_flood">less than an hour</a>. These sudden torrential downpours, called cloudbursts, can lead to flash flooding that can overflow streams and roads and trap people wherever they are.</p>
<p>[<em>The Conversation’s science, health and technology editors pick their favorite stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-favorite">Weekly on Wednesdays</a>.]</p>
<p>Thankfully, because thunderstorms are so violent and relatively small, they don’t last very long. Once the rain falls from the clouds and squashes the upward air currents, the clouds disappear and you often see a nice blue sky. </p>
<p>Of course, winter can deliver some strong storms too – especially over the warmer ocean water. When strong winter storms drop lots of heavy rain, the same principles are at work: lots of moisture in the air, fast upwards wind currents and tall clouds. </p>
<p>No two rainstorms are ever the same. Sometimes clouds can rain so hard it feels like you are standing in the shower. Other times they bring only a nice peaceful drizzle. Now, whether you are soaked or singing in the rain, you’ll know why. </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>.</em> </p>
<p><em>Please tell us your name, age and the city where you live. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/143402/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jeffrey B. Halverson 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>
Some rainstorms drench you in a second, while others drop rain in a nice peaceful drizzle. A meteorologist explains how rainstorms can be so different.
Jeffrey B. Halverson, Professor of Geography & Environmental Systems, Associate Dean of the Graduate School, University of Maryland, Baltimore County
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/143271
2020-07-27T20:01:48Z
2020-07-27T20:01:48Z
Carbon emissions are chilling the atmosphere 90km above Antarctica, at the edge of space
<figure><img src="https://images.theconversation.com/files/349532/original/file-20200727-19-1oaacdj.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C4601%2C3456&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Ashleigh Wilson</span></span></figcaption></figure><p>While greenhouse gases are warming Earth’s surface, they’re also causing rapid cooling far above us, at the edge of space. In fact, the upper atmosphere about 90km above Antarctica is cooling at a rate ten times faster than the average warming at the planet’s surface. </p>
<p>Our <a href="https://www.antarctica.gov.au/news/2020/antarctic-research-unlocks-mysteries-of-the-upper-atmosphere/">new research</a> has precisely measured this cooling rate, and revealed an important discovery: a new four-year temperature cycle in the polar atmosphere. The results, based on 24 years of continuous measurements by Australian scientists in Antarctica, were published in <a href="https://www.atmos-chem-phys.net/20/6379/2020/">two</a> <a href="https://www.atmos-chem-phys.net/20/8691/2020/">papers</a> this month.</p>
<p>The findings show Earth’s upper atmosphere, in a region called the “mesosphere”, is extremely sensitive to rising greenhouse gas concentrations. This provides a new opportunity to monitor how well government interventions to reduce emissions are working.</p>
<p>Our project also monitors the spectacular natural phenomenon known as “noctilucent” or “night shining” clouds. While beautiful, the more frequent occurrence of these clouds is <a href="https://www.sciencedirect.com/science/article/pii/S0273117703904704">considered</a> a bad sign for climate change.</p>
<h2>Studying the ‘airglow’</h2>
<p>Since the 1990s, scientists at Australia’s Davis research station have taken more than 600,000 measurements of the temperatures in the upper atmosphere above Antarctica. We’ve done this using sensitive optical instruments called <a href="https://www.antarctica.gov.au/about-antarctica/ice-and-atmosphere/atmosphere/studying-the-atmosphere/hydroxyl-airglow-temperature-observations/">spectrometers</a>.</p>
<p>These instruments analyse the infrared glow radiating from so-called hydroxyl molecules, which exist in a thin layer about 87km above Earth’s surface. This “airglow” allows us to measure the temperature in this part of the atmosphere.</p>
<figure class="align-right ">
<img alt="Scientific equipment" src="https://images.theconversation.com/files/349522/original/file-20200727-25-nzp4ev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/349522/original/file-20200727-25-nzp4ev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=489&fit=crop&dpr=1 600w, https://images.theconversation.com/files/349522/original/file-20200727-25-nzp4ev.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=489&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/349522/original/file-20200727-25-nzp4ev.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=489&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/349522/original/file-20200727-25-nzp4ev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=614&fit=crop&dpr=1 754w, https://images.theconversation.com/files/349522/original/file-20200727-25-nzp4ev.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=614&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/349522/original/file-20200727-25-nzp4ev.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=614&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Spectrometer in the optical laboratory at Davis station, Antarctica.</span>
<span class="attribution"><span class="source">John French</span></span>
</figcaption>
</figure>
<p>Our results show that in the high atmosphere above Antarctica, carbon dioxide and other greenhouse gases do not have the warming effect they do in the lower atmosphere (by colliding with other molecules). Instead the excess energy is radiated to space, causing a cooling effect.</p>
<p>Our new research more accurately determines this cooling rate. Over 24 years, the upper atmosphere temperature has cooled by about 3°C, or 1.2°C per decade. That is about ten times greater than the average warming in the lower atmosphere – <a href="https://climate.nasa.gov/vital-signs/global-temperature/">about 1.3°C over the past century</a>.</p>
<h2>Untangling natural signals</h2>
<p>Rising greenhouse gas emissions are contributing to the temperature changes we recorded, but a number of other influences are also at play. These include the seasonal cycle (warmer in winter, colder in summer) and the Sun’s 11-year activity cycle (which involves quieter and more intense solar periods) in the mesosphere.</p>
<p>One challenge of the research was untangling all these merged “signals” to work out the extent to which each was driving the changes we observed. </p>
<p>Surprisingly in this process, we discovered a new natural cycle not previously identified in the polar upper atmosphere. This four-year cycle which we called the Quasi-Quadrennial Oscillation (QQO), saw temperatures vary by 3-4°C in the upper atmosphere.</p>
<p>Discovering this cycle was like stumbling across a gold nugget in a well-worked claim. More work is needed to determine its origin and full importance.</p>
<p>But the finding has big implications for climate modelling. The physics that drive this cycle are unlikely to be included in global models currently used to predict climate change. But a variation of 3-4°C every four years is a large signal to ignore.</p>
<p>We don’t yet know what’s driving the oscillation. But whatever the answer, it also seems to affect the winds, sea surface temperatures, atmospheric pressure and sea ice concentrations around Antarctica. </p>
<h2>‘Night shining’ clouds</h2>
<p>Our research also monitors how cooling temperatures are affecting the occurrence of <a href="https://www.antarctica.gov.au/magazine/issue-14-2008/science/first-antarctic-ground-satellite-view-of-ice-aerosol-clouds-at-the-edge-of-space/">noctilucent</a> or “night shining” clouds.</p>
<p><a href="https://www.google.com/amp/s/spaceweatherarchive.com/2020/03/26/noctilucent-clouds-over-the-south-pacific/amp/">Noctilucent clouds</a> are very rare – from Australian Antarctic stations we’ve recorded about ten observations since 1998. They occur at an altitude of about 80km in the polar regions during summer. You can only see them from the ground when the sun is below the horizon during twilight, but still shining on the high atmosphere.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/humans-are-encroaching-on-antarcticas-last-wild-places-threatening-its-fragile-biodiversity-142648">Humans are encroaching on Antarctica’s last wild places, threatening its fragile biodiversity</a>
</strong>
</em>
</p>
<hr>
<p>The clouds appear as thin, pale blue, wavy filaments. They are comprised of ice crystals and require temperatures around minus 130°C to form. While impressive, noctilucent clouds are <a href="https://phys.org/news/2018-07-climate-night-shining-clouds-visible.html">considered</a> a “<a href="http://userweb.eng.gla.ac.uk/william.ward/eos_review.pdf">canary</a> in the coalmine” of climate change. Further cooling of the upper atmosphere as a result of greenhouse gas emissions will likely lead to more frequent noctilucent clouds. </p>
<p>There is already some evidence the clouds are becoming brighter and more widespread in the <a href="https://spaceweatherarchive.com/2020/06/09/record-cold-in-the-mesosphere/">Northern Hemisphere</a>.</p>
<figure class="align-center ">
<img alt="Sea ice in Antarctica" src="https://images.theconversation.com/files/349537/original/file-20200727-35-1scxyrg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/349537/original/file-20200727-35-1scxyrg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=393&fit=crop&dpr=1 600w, https://images.theconversation.com/files/349537/original/file-20200727-35-1scxyrg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=393&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/349537/original/file-20200727-35-1scxyrg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=393&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/349537/original/file-20200727-35-1scxyrg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=493&fit=crop&dpr=1 754w, https://images.theconversation.com/files/349537/original/file-20200727-35-1scxyrg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=493&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/349537/original/file-20200727-35-1scxyrg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=493&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The new temperature cycle is reflected in the concentration of sea ice in Antacrtica.</span>
<span class="attribution"><span class="source">John French</span></span>
</figcaption>
</figure>
<h2>Measuring change</h2>
<p>Human-induced climate change threatens to alter radically the conditions for life on our planet. Over the next several decades - less than one lifetime - the average global air temperature is expected to increase, bringing with it sea level rise, weather extremes and changes to ecosystems across the world.</p>
<p>Long term monitoring is important to measure change and test and calibrate ever more complex climate models. Our results contribute to a global network of observations coordinated by the <a href="https://ndmc.dlr.de/">Network for Detection of Mesospheric Change</a> for this purpose. </p>
<p>The accuracy of these models is critical to determining whether government and other interventions to curb climate change are indeed effective.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/anatomy-of-a-heatwave-how-antarctica-recorded-a-20-75-c-day-last-month-134550">Anatomy of a heatwave: how Antarctica recorded a 20.75°C day last month</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/143271/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John French receives funding from the Australian Antarctic Division. </span></em></p><p class="fine-print"><em><span>Andrew Klekociuk receives funding from the Australian Antarctic Division. </span></em></p><p class="fine-print"><em><span>Frank Mulligan lectures and carries out research in Experimental Physics at Maynooth University in Ireland. </span></em></p>
Carbon emissions are chilling the atmosphere 90km above Antarctica, at the edge of space
John French, Atmospheric Physicist at Australian Antarctic Division and Adjunct Lecturer, University of Tasmania
Andrew Klekociuk, Principal Research Scientist, Australian Antarctic Division and Adjunct Senior Lecturer, University of Tasmania
Frank Mulligan, National University of Ireland Maynooth
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/143215
2020-07-24T12:04:34Z
2020-07-24T12:04:34Z
Curious Kids: How much does a cloud weigh?
<figure><img src="https://images.theconversation.com/files/349331/original/file-20200724-17-tw3oty.jpg?ixlib=rb-1.1.0&rect=0%2C52%2C4985%2C2687&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cute-kid-girl-standing-on-house-773037775">Khakimullin Aleksandr/Shutterstock</a></span></figcaption></figure><p><strong>How much do clouds weigh? – Torben, aged 10, London, UK</strong></p>
<p>We see clouds often: fluffy clouds on a nice summer’s day, towering thunderstorms, wispy high clouds or even grey clouds that cover the whole sky for days. </p>
<p>Clouds seem to be floating in the air, which might make you think that they don’t weigh very much at all – but you would be wrong. </p>
<p>We can use our knowledge of different types of cloud and <a href="http://downloads.bbc.co.uk/tv/greatbritishweather/cloudspottingguide.pdf">what clouds are made of</a>, as well as some maths, to work out how much they weigh.</p>
<h2>Water and air</h2>
<p>We first need to think about what clouds are made of. Clouds are actually mostly made from air, plus small water droplets (which might be frozen into small ice crystals). When we think about how much a cloud weighs, we need to measure both the weight of the water and the weight of the air.</p>
<p>The next question is what type of cloud we are weighing. There are lots of different types of cloud, all with <a href="https://www.rmets.org/resource/cloud-names-and-cloud-classifications">their own names</a>. The fluffy clouds that drift across the sky in summer are called cumulus clouds.</p>
<figure class="align-center ">
<img alt="Cumulus clouds in blue sky" src="https://images.theconversation.com/files/349332/original/file-20200724-37-bc1uu3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/349332/original/file-20200724-37-bc1uu3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/349332/original/file-20200724-37-bc1uu3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/349332/original/file-20200724-37-bc1uu3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/349332/original/file-20200724-37-bc1uu3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/349332/original/file-20200724-37-bc1uu3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/349332/original/file-20200724-37-bc1uu3.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">
<figcaption>
<span class="caption">Fluffy cumulus clouds.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/white-cumulus-clouds-blue-sky-20671912">Lars Christensen/Shutterstock</a></span>
</figcaption>
</figure>
<p>To start with, we will think about that fluffy summer cloud, the <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/clouds/low-level-clouds/cumulus">cumulus</a> cloud. A cumulus has approximately a quarter of a gram of water for every cubic metre of cloud. A quarter of a gram of water, all together, would make a drop of about the size of a marble. But really in our cubic metre there would be around 1 million drops, so they are very tiny, too small to see.</p>
<h2>How big?</h2>
<p>The next thing to consider is the size of the cloud. You can see how big cumulus clouds really are if you look at their shadow on the ground from a high view point on a sunny summer day.</p>
<p>Summer cumulus clouds vary in size, but a typical one would be about one kilometre across and about the same tall. This means we can consider it to be a cube, with each side measuring 1km across. That means our cloud is 1,000 x 1,000 x 1,000 cubic metres in size – and this makes 1 billion cubic metres. </p>
<p>Our cloud had only a quarter of a gram of water per cubic metre, but that’s going to work out as rather a lot now there’s a billion of them. The weight of the water in the cumulus cloud is 250,000,000 grams – 250 tonnes. This is about the same as two adult blue whales. </p>
<figure class="align-center ">
<img alt="Thunderstorm clouds over tropical beach" src="https://images.theconversation.com/files/349334/original/file-20200724-19-81z7fr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/349334/original/file-20200724-19-81z7fr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/349334/original/file-20200724-19-81z7fr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/349334/original/file-20200724-19-81z7fr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/349334/original/file-20200724-19-81z7fr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/349334/original/file-20200724-19-81z7fr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/349334/original/file-20200724-19-81z7fr.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">
<figcaption>
<span class="caption">Thunderstorm clouds approaching.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/sandy-beach-moored-indonesian-boats-on-1257414619">Fisher_Y/Shutterstock</a></span>
</figcaption>
</figure>
<p>What about the other cloud types? A thunderstorm cloud is bigger, measuring about 10 km tall and the same across. They also contain much more water, which is why they rain so hard: about two grams per cubic metre. Do the maths again and we have 2 million tonnes of water.</p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a> that gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a>. We won’t be able to answer every question, but we’ll do our very best.</em></p>
<hr>
<p>Then there’s that grey sky cloud layer. This has about the same amount of water per cubic metre as the cumulus cloud, but they cover the whole sky. They are often very shallow – perhaps 200 metres thick – but they could easily be 500 km across. This makes them 50,000 times bigger than the cumulus, so that’s somewhere around 10 million tonnes of water.</p>
<p>Finally, we need to add the weight of the water in the cloud to the weight of the air. Let us return to our summer cumulus cloud. Where these low clouds are, the air weighs around one kilogram for every cubic metre – 4,000 times more than the water did. </p>
<p>Given the volume of our cumulus cloud, that’s 1 billion kg, or one million tonnes. That is why the cloud can stay up in the air – the tiny water drops are held up by all that air.</p>
<p>If we do the same maths for a thunderstorm cloud, we get one billion tonnes of air. For the grey sky cloud layer, it’s 50 billion tonnes.</p>
<p>If we add together the weight of the water and the air in a cumulus cloud, then, it weighs a total of 1,000,250 tonnes. You could say, though, that maybe the air doesn’t count as part of the cloud’s weight, as it would have been there anyway. Either way, clouds are heavier than you might think.</p>
<hr>
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<hr><img src="https://counter.theconversation.com/content/143215/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rob Thompson receives funding from NERC.</span></em></p>
It’s a lot more than you might think.
Rob Thompson, Postdoctoral Research Scientist in Meteorology, University of Reading
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/140041
2020-06-19T12:07:46Z
2020-06-19T12:07:46Z
We caught bacteria from the most pristine air on earth to help solve a climate modeling mystery
<figure><img src="https://images.theconversation.com/files/342540/original/file-20200617-94040-1jy5ehs.jpg?ixlib=rb-1.1.0&rect=8%2C24%2C5377%2C2987&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Not all clouds are the same, and climate models have been predicting the wrong kinds of clouds over the Southern Ocean. </span> <span class="attribution"><span class="source">Kathryn Moore</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>The Southern Ocean is a vast band of open water that encircles the entire planet between Antarctica and the Southern Hemisphere landmasses. It is the cloudiest place on Earth, and the amount of sunlight that reflects off or passes through those clouds plays a surprisingly important role in global climate. It affects weather patterns, <a href="https://doi.org/10.1029/2012GL053115">ocean currents</a>, <a href="https://doi.org/10.1038/s41467-018-05634-2">Antarctic sea ice cover</a>, sea surface temperature and even <a href="https://doi.org/10.1073/pnas.1213302110">rainfall in the tropics</a>.</p>
<p>But due to how remote the Southern Ocean is, there have been very few actual studies of the clouds there. Because of this lack of data, computer models that simulate present and future climates <a href="https://doi.org/10.1175/2009JCLI3152.1">overpredict how much sunlight reaches the ocean surface</a> compared to what satellites actually observe. The main reason for this inaccuracy is due to how the <a href="https://doi.org/10.1175/JCLI-D-13-00169.1">models simulate clouds</a>, but nobody knew exactly why the clouds were off. For the models to run correctly, researchers needed to understand how the clouds were being formed.</p>
<p>To discover what is actually happening in clouds over the Southern Ocean, a <a href="https://www.eol.ucar.edu/content/socrates-project-overview">small army of atmospheric scientists</a>, <a href="http://chem.atmos.colostate.edu/">including us</a>, went to find out how and when clouds form in this remote part of the world. What we found was surprising – unlike the Northern Hemisphere oceans, the <a href="https://doi.org/10.1073/pnas.2000134117">air we sampled over the Southern Ocean contained almost no particles from land</a>. This means the clouds might be different from those above other oceans, and we can use this knowledge to help improve the climate models.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/342539/original/file-20200617-94060-w5fy6r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/342539/original/file-20200617-94060-w5fy6r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/342539/original/file-20200617-94060-w5fy6r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/342539/original/file-20200617-94060-w5fy6r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/342539/original/file-20200617-94060-w5fy6r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/342539/original/file-20200617-94060-w5fy6r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/342539/original/file-20200617-94060-w5fy6r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/342539/original/file-20200617-94060-w5fy6r.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">Whether clouds contain small liquid droplets or ice crystals or both is influenced by the particles in the air.</span>
<span class="attribution"><span class="source">Kathryn Moore</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Ice clouds and liquid clouds</h2>
<p>Clouds are made of tiny water droplets or ice crystals, or often a mixture of the two. These form on small particles in the air. The type of particle plays a big role in determining whether a liquid droplet or ice crystal forms. These particles can be natural – like sea spray, pollen, dust or even bacteria – or from human sources like cars, stoves, power plants and so on.</p>
<p>To the untrained eye, an ice cloud and a liquid cloud look much the same, but they have very different properties. Ice clouds <a href="https://doi.org/10.1175/AMSMONOGRAPHS-D-17-0001.1">reflect less sunlight</a>, precipitate more and don’t last as long as liquid clouds. It matters to the weather – and to climate models – what kinds of clouds are around. </p>
<p>Climate models tend to predict <a href="https://doi.org/10.1175/JCLI-D-15-0564.1">too many ice clouds</a> over the Southern Ocean and not enough liquid clouds when compared to satellite readings. But satellite measurements around the poles are hard to make and <a href="https://doi.org/10.1029/2018JD028535">less accurate than other regions</a>, so we wanted to collect direct evidence of how many liquid clouds are actually present and determine why there were more than the models predict.</p>
<p>This was the mystery: Why are there more liquid clouds than the models think there are? To solve it, we needed to know what kinds of particles are floating around in the atmosphere around Antarctica.</p>
<p>Before we went down there, we had a few clues. </p>
<p>Previous modeling studies have suggested that the ice–forming particles found over the Southern Ocean may be very different from those found in the Northern Hemisphere. Dust is a great ice cloud seeder, but due to the lack of dusty land sources in the Southern Hemisphere, some scientists have hypothesized that other types of particles might be <a href="https://doi.org/10.5194/acp-13-245-2013">driving ice cloud formation</a> over the Southern Ocean.</p>
<p>Since <a href="https://doi.org/10.1029/2011RG000363">most models are based on data from the Northern Hemisphere</a>, if the particles in the atmosphere were somehow different in the Southern Hemisphere, that might explain the errors.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/342851/original/file-20200618-41200-fize9k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/342851/original/file-20200618-41200-fize9k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/342851/original/file-20200618-41200-fize9k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=475&fit=crop&dpr=1 600w, https://images.theconversation.com/files/342851/original/file-20200618-41200-fize9k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=475&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/342851/original/file-20200618-41200-fize9k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=475&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/342851/original/file-20200618-41200-fize9k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=597&fit=crop&dpr=1 754w, https://images.theconversation.com/files/342851/original/file-20200618-41200-fize9k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=597&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/342851/original/file-20200618-41200-fize9k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=597&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 used these sampling instruments to capture airborne bacteria and determine where the air, and the particles that start the clouds, came from.</span>
<span class="attribution"><span class="source">Kathryn Moore</span></span>
</figcaption>
</figure>
<h2>Bacterial maps</h2>
<p>It’s hard to directly measure the composition of particles over the Southern Ocean – there simply aren’t very many particles around. So, to help us track down what is inside the clouds, we used an indirect approach: the bacteria in the air. </p>
<p>The atmosphere is full of microorganisms that are carried hundreds to thousands of kilometers on air currents before returning to Earth. These bacteria are like airborne license plates, they are unique and tell you where the car – or air – came from. Since scientists know where most bacteria live, it’s possible to look at the microbes in an air sample and determine where that air came from. And once you know that, you can predict where the particles in the air came from as well - the same place the bacteria usually live.</p>
<p>In order to sample airborne bacteria in this remote ocean region, one of us headed out on the Australian Marine National Facility’s R/V Investigator for a six-week expedition. The weather was unruly and the waves were often white-capped, but for one to two days at a time, we sucked air from the bow of the ship through a filter that caught the airborne particles and bacteria. We then froze the filters to keep the bacterial DNA intact.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/342534/original/file-20200617-94054-5en3g0.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/342534/original/file-20200617-94054-5en3g0.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/342534/original/file-20200617-94054-5en3g0.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/342534/original/file-20200617-94054-5en3g0.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/342534/original/file-20200617-94054-5en3g0.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/342534/original/file-20200617-94054-5en3g0.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/342534/original/file-20200617-94054-5en3g0.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/342534/original/file-20200617-94054-5en3g0.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 bacteria in the air above the Southern Ocean are locals, almost entirely the same bacteria that live in the waters below.</span>
<span class="attribution"><span class="source">Thomas Hill</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Ocean bacteria alone</h2>
<p>In most ocean regions around the world, especially in the Northern Hemisphere where there is a lot of land, the air contains both <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2001JD001174">marine and terrestrial particles</a>. That’s what we expected to find down south.</p>
<p>With the frozen filters safely back at our lab in Colorado, we extracted DNA from the bacteria and sequenced it to determine what species we had caught. Much to our surprise, the <a href="https://doi.org/10.1073/pnas.2000134117">bacteria were essentially all marine species</a> that live in the Southern Ocean. We found almost no land-based bacteria. </p>
<p>If the bacteria were from the ocean, then so were the cloud-forming particles. This was the answer we were looking for. </p>
<p>Ice nucleating particles are <a href="https://doi.org/10.1029/2018GL079981">very rare in seawater</a> and marine particles are very good at forming liquid clouds. With mostly marine-based particles in the air, we’d expect the clouds to mostly be made of liquid droplets, which is what we observed. Since most models treat clouds in this region the same way they do clouds in the dustier Northern Hemisphere, it’s no wonder the models were off.</p>
<h2>Going forward</h2>
<p>Now that we know the summertime Southern Ocean clouds are being formed from purely marine particles, we need to figure out if the <a href="https://www.arm.gov/research/campaigns/osc2016micre">same is true in other seasons</a> and at higher altitudes. The larger project, which involved <a href="https://www.eol.ucar.edu/content/socrates-project-overview">planes</a> as well as <a href="https://www.arm.gov/research/campaigns/amf2017marcus">ships</a>, has given atmospheric scientists a much better idea of the clouds both close to the ocean surface and high up in the atmosphere. The climate modelers among us are already incorporating these new data into their models and will hopefully have results to share soon.</p>
<p>Discovering that the airborne particles over the Southern Ocean are mostly coming from the ocean is a remarkable finding. It not only improves global climate models, it also means we confirmed the Southern Ocean is <a href="https://doi.org/10.1073/pnas.1415440111">one of the most environmentally pristine regions</a> on Earth – a place that has probably changed very little due to human activities. Our work will hopefully improve climate models, but has also given researchers a baseline for what a truly pristine marine environment looks like. </p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklysmart">You can get our highlights each weekend</a>.]</p><img src="https://counter.theconversation.com/content/140041/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>This research was funded by the National Science Foundation (NSF). Related research was funded by the Department of Energy. I also receive funding from the NSF through a Graduate Research Fellowship.</span></em></p><p class="fine-print"><em><span>The research is funded by the National Science Foundation. </span></em></p><p class="fine-print"><em><span>This research was supported by US NSF Award 1660486 in support of SOCRATES. Related research was funded by the Department of Energy.</span></em></p>
Climate models have been overestimating how much sunlight hits the Southern Ocean. This is because the clouds there are different from clouds anywhere else. Bacterial DNA helped us understand why.
Kathryn Moore, PhD student in Atmospheric Science, Colorado State University
Jun Uetake, Postdoctoral Atmospheric Scientist, Colorado State University
Thomas Hill, Research Scientist, Colorado State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/133219
2020-05-28T12:13:41Z
2020-05-28T12:13:41Z
What would it feel like to touch a cloud?
<figure><img src="https://images.theconversation.com/files/336133/original/file-20200519-152298-1icmco7.jpg?ixlib=rb-1.1.0&rect=867%2C810%2C3877%2C2347&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">They may look comfy to sit on but you'd plummet through and hit the ground.</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/E9aetBe2w40">Sam Schooler/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>What would it feel like to touch a cloud? – Violet V., age 6, Somerville, Massachusetts</strong></p>
</blockquote>
<hr>
<p>You might already know how it feels to touch a cloud without realizing it.</p>
<p>If you’ve ever been outside on a foggy day, you’ve essentially been inside a cloud, just one very close to the ground instead of high in the sky. Fog and clouds are both made of tiny water droplets – like the ones you can sometimes see or feel in a hot, steamy shower.</p>
<p>Clouds form through evaporation and condensation. Water in lakes, rivers, oceans or puddles evaporates into water vapor as the sun heats it up. <a href="https://sciencing.com/science-projects-teaching-evaporation-condensation-8029453.html">You can evaporate water yourself</a> by boiling it – watch it disappear as vapor.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/q87Ekar3emA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How do clouds form?</span></figcaption>
</figure>
<p>Water vapor, which is invisible, naturally rises up from the Earth’s surface into the atmosphere as warm bubbles, like the bubbles you’d see rising in a lava lamp. The higher it goes, the more it cools, until eventually the water vapor condenses back into liquid water.</p>
<p>Clouds are made of millions of these tiny liquid water droplets. The droplets scatter the colors of the sunlight equally, which makes <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/clouds/why-are-clouds-white">clouds appear white</a>. Even though they can look like cushy puffballs, a cloud can’t support your weight or hold anything up but itself.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/336200/original/file-20200519-152315-abcowj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/336200/original/file-20200519-152315-abcowj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/336200/original/file-20200519-152315-abcowj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=654&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336200/original/file-20200519-152315-abcowj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=654&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336200/original/file-20200519-152315-abcowj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=654&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336200/original/file-20200519-152315-abcowj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=822&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336200/original/file-20200519-152315-abcowj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=822&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336200/original/file-20200519-152315-abcowj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=822&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Water vapor in your bathroom can fog up the mirror.</span>
</figcaption>
</figure>
<p>The process of evaporation and condensation in the atmosphere is similar to what happens in your bathroom when you take a hot shower: Warm water evaporates and then condenses back into water on the cold mirror.</p>
<p>Water vapor does not condense spontaneously. It needs tiny particles or a surface – like your bathroom mirror – on which to form a drop. <a href="https://scholar.google.com/citations?user=BSQl42wAAAAJ&hl=en&oi=ao">Atmospheric scientists like me</a> call these tiny particles cloud condensation nuclei, or CCN for short. These CCN are just dirt or dust particles that have been lifted by the wind and are <a href="https://gmao.gsfc.nasa.gov/research/aerosol/modeling/nr1_movie/">floating around in the atmosphere</a>.</p>
<p>Does that mean that places with a lot of dust and pollution, like cities, have more drops than clean places? Researchers have found more tiny droplets and more clouds in areas where there are a lot of these cloud condensation nuclei, while in areas without them fewer clouds are observed, <a href="https://eos.org/editors-vox/atmospheric-aerosol-in-the-changing-arctic">like over the ocean or the Arctic</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/336199/original/file-20200519-152288-wz4zrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/336199/original/file-20200519-152288-wz4zrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/336199/original/file-20200519-152288-wz4zrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=336&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336199/original/file-20200519-152288-wz4zrm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=336&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336199/original/file-20200519-152288-wz4zrm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=336&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336199/original/file-20200519-152288-wz4zrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=423&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336199/original/file-20200519-152288-wz4zrm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=423&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336199/original/file-20200519-152288-wz4zrm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=423&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Water evaporates and rises up into the sky, condensing to form clouds.</span>
<span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/30580">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>As cloud droplets rise in the atmosphere, the air temperature decreases. The tiny cloud droplets start to freeze when the temperature drops below below 32 degrees Fahrenheit (0 degrees Celsius). It’s the exact same process as making ice cubes in a freezer.</p>
<p>The frozen droplets are now ice crystals. They continue to grow in size as water vapor turns into ice and sticks onto them. Scientists call this process of a gas turning into a solid “deposition.” It creates the beautiful branched ice crystals that you find in snowstorms.</p>
<p>Steady updrafts of air keep these very light water droplets or ice crystals floating in the cloud. So how do they turn into rain and snow and fall to the ground? Easy, they join forces.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/336201/original/file-20200519-152344-1qvj0ie.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/336201/original/file-20200519-152344-1qvj0ie.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/336201/original/file-20200519-152344-1qvj0ie.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=715&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336201/original/file-20200519-152344-1qvj0ie.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=715&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336201/original/file-20200519-152344-1qvj0ie.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=715&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336201/original/file-20200519-152344-1qvj0ie.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=899&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336201/original/file-20200519-152344-1qvj0ie.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=899&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336201/original/file-20200519-152344-1qvj0ie.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=899&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Those spiky arms can grab on to other snowflakes.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/5p_hbvdcEvo">Aaron Burden/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Larger droplets collect smaller droplets on their way to the ground as raindrops. Snow grows in a similar way, with the crystals sticking to each other. Their little arms can interlock to form a bigger snowflake. When water droplets merge with ice crystals, that makes hail.</p>
<p>Rain droplets grow on their way down to the ground, eventually becoming unstable and breaking up. <a href="https://www.washington.edu/news/2004/07/22/record-rain-uw-scientists-find-some-of-the-biggest-raindrops-ever/">The largest raindrop</a> that researchers have found was about a third of an inch across. Some <a href="https://www.nytimes.com/2007/03/20/science/20snow.html">giant snowflakes</a> have been reported to be as big as 6 inches across. And the biggest piece of hail? In 2010, someone found <a href="https://www.weather.gov/abr/vivianhailstone">a hailstone 8 inches in diameter</a> in South Dakota and took a photo – so scientists know it was real.</p>
<p>That would be a lot more painful to collide with than a wispy cloud of water vapor.</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/133219/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katja Friedrich 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>
You might have already felt what it would be like inside a cloud made of condensed water vapor.
Katja Friedrich, Associate Professor of Atmospheric and Oceanic Sciences, University of Colorado Boulder
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/124743
2019-10-09T12:51:02Z
2019-10-09T12:51:02Z
Curious Kids: why is the sea salty?
<figure><img src="https://images.theconversation.com/files/296197/original/file-20191009-3872-f1k9k1.jpg?ixlib=rb-1.1.0&rect=21%2C173%2C4804%2C3038&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/aWo49dHxYVE">Grant Elliott/Unsplash.</a>, <a class="license" href="http://artlibre.org/licence/lal/en">FAL</a></span></figcaption></figure><p><strong>Why is the sea salty? – Torben, aged nine, Sussex, UK.</strong></p>
<p>Two-thirds of the Earth’s surface is covered in water, and <a href="https://enviroliteracy.org/water/oceans/">97% of that is salty seawater</a>. Only 3% of our planet’s water is fresh, and 2% is trapped, frozen in ice caps, glaciers and soils. That leaves less than 1% as fresh, liquid water in rivers, lakes and streams – and this fresh water plays a big role in explaining why the sea is salty. </p>
<p>Water moves around our planet in <a href="https://www.metoffice.gov.uk/weather/learn-about/met-office-for-schools/other-content/other-resources/water-cycle">a cycle</a> powered by the sun: from the sea, to the sky, to the land and then back to the sea. When the sun heats the water in the sea, it changes into a gas called “water vapour” and rises into the air, through a process called “evaporation”. </p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a>, which gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a>. We won’t be able to answer every question, but we’ll do our very best.</em></p>
<hr>
<p>While floating in the air, the water vapour cools off and turns back into liquid water, forming clouds (through a process called “condensation”). This water eventually falls from the clouds in the sky as rain, sleet, hail or snow (that’s called “precipitation”). </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/296200/original/file-20191009-3887-1r501t4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296200/original/file-20191009-3887-1r501t4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296200/original/file-20191009-3887-1r501t4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296200/original/file-20191009-3887-1r501t4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296200/original/file-20191009-3887-1r501t4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296200/original/file-20191009-3887-1r501t4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296200/original/file-20191009-3887-1r501t4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The water cycle in action.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/2eujrTV8NG8">Vikas Anand Dev/Unsplash.</a>, <a class="license" href="http://artlibre.org/licence/lal/en">FAL</a></span>
</figcaption>
</figure>
<p>When precipitation falls on land, the water flows into streams and rivers, and eventually makes its way back out to the sea. Then the sun heats the sea water and the cycle starts all over again. </p>
<h2>(Slightly) acid rain</h2>
<p>You’re probably still wondering where the salt comes in. Well, the rain that falls from the sky is not just pure water – it actually contains small amounts of chemicals called carbon dioxide and sulphur dioxide, which are <a href="https://sciencetrends.com/what-is-chemical-weathering-with-examples/">absorbed by the water</a> while it is still in the air. </p>
<p>This means that rain is actually very slightly acidic (but not enough to do you any harm). When the rain falls on the ground, this weak acid <a href="https://www.bbc.co.uk/bitesize/guides/zwd2mp3/revision/2">can dissolve</a> small amounts of mineral salts from the rocks, including sodium and chloride, which then enter the water.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/296199/original/file-20191009-3872-1bof5jj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296199/original/file-20191009-3872-1bof5jj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296199/original/file-20191009-3872-1bof5jj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296199/original/file-20191009-3872-1bof5jj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296199/original/file-20191009-3872-1bof5jj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296199/original/file-20191009-3872-1bof5jj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296199/original/file-20191009-3872-1bof5jj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Run, river, run.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/JJdBjI5BXzA">Matt Heaton/Unsplash.</a>, <a class="license" href="http://artlibre.org/licence/lal/en">FAL</a></span>
</figcaption>
</figure>
<p>Sodium chloride is the main salt in seawater, and the same one you might have on your table at home. The rain water flows off the land and into the rivers and streams that lead all the way to the sea – carrying the dissolved salts along with it. </p>
<h2>Salinity in streams?</h2>
<p>But if the rivers and streams are carrying these dissolved salts, then why aren’t they as salty as the sea? In fact, they’re only carrying very low levels of these salts. The salts in the seas have built up over billions of years, and seawater contains about <a href="http://ocean.stanford.edu/courses/bomc/chem/lecture_04.pdf">300 times more dissolved salts</a> than average river water. </p>
<p>To put it another way, every one litre of seawater has <a href="https://oceanservice.noaa.gov/facts/whysalty.html">35 grams of salts</a> dissolved in it, while a litre of freshwater would only have 0.5 grams. That’s why we say that seawater has a much higher concentration of salt – or “salinity” – than the freshwater flowing through rivers and streams. </p>
<p>Some salts can also enter the seas from hot vents on the deep ocean floor and from volcanoes on the land and in the sea. Some salts (particularly chloride) are also moved around as part of the water cycle – these are known as “cyclic salts” and originally <a href="https://www.futurelearn.com/courses/exploring-our-ocean/0/steps/730">came from volcanoes</a>. </p>
<h2>Tipping the balance</h2>
<p>Since salt is always flowing from the land to the sea, you might think the sea is getting saltier. But actually, some of this salt is removed by algae and animals that live in the sea, and some is deposited as sediment on the bottom of the ocean. So the salt going into the sea keeps a balance with the salt being deposited or removed. </p>
<p>The salinity of the sea isn’t the same everywhere. In warmer, tropical areas, more evaporation occurs, so the water is saltier. Towards the north and south poles, the seawater is diluted by melting ice, so the water is not so salty. This is natural. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/296205/original/file-20191009-3856-1r1vi0u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296205/original/file-20191009-3856-1r1vi0u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296205/original/file-20191009-3856-1r1vi0u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296205/original/file-20191009-3856-1r1vi0u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296205/original/file-20191009-3856-1r1vi0u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296205/original/file-20191009-3856-1r1vi0u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296205/original/file-20191009-3856-1r1vi0u.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">Melting sea ice.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/qbtyUQtqJ8k">Roxanne Desgagnés/Unsplash.</a>, <a class="license" href="http://artlibre.org/licence/lal/en">FAL</a></span>
</figcaption>
</figure>
<p>But these differences in salinity might get bigger in the future, <a href="https://insideclimatenews.org/news/07052018/atlantic-ocean-circulation-slowing-climate-change-heat-temperature-rainfall-fish-why-you-should-care">because of climate change</a>. Warmer climates may lead to more rain and melting ice in the northern hemisphere, and more evaporation in the southern hemisphere, which could change the saltiness of our seas. </p>
<p>The saltier that water is, the more dense (or heavier) it becomes. Along with warmer temperatures, this could affect how water moves around in the oceans, which could affect all life on our planet – not just the creatures living in the sea. </p>
<p><em>This article has been updated to reflect the fact that sodium and chloride ions separate out when dissolved in water.</em></p>
<hr>
<p><em>Children can have their own questions answered by experts – just send them in to <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, along with the child’s first name, age and town or city. You can:</em></p>
<ul>
<li><em>email <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a></em></li>
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<p><em>Here are some more <a href="https://theconversation.com/topics/curious-kids-36782?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Curious Kids</a> articles, written by academic experts:</em></p>
<ul>
<li><p><em><a href="https://theconversation.com/curious-kids-why-does-the-light-turn-on-124549?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Why does the light turn on? – Ben, aged three, UK.</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-why-do-i-have-boogies-and-why-does-my-nose-keep-replicating-them-122660?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Why do I have boogies and why does my nose keep replicating them? – Duncan, aged seven, Sydney, Australia.</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-could-humans-live-on-kepler-452-b-123786?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Can we live on Kepler 452-b? – Year Five, Globe Primary School, London, UK.</a></em></p></li>
</ul><img src="https://counter.theconversation.com/content/124743/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sally Little 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 salt in the sea has built up over billions of years – but it wouldn’t have got there without freshwater rivers and streams.
Sally Little, Senior Lecturer in Ecology, Nottingham Trent University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/119771
2019-07-03T11:00:00Z
2019-07-03T11:00:00Z
Blue ‘noctilucent’ clouds are appearing further south than ever seen before – and pollution may be a cause
<p>Cloud watchers have recently been given <a href="https://spaceweatherarchive.com/2019/06/17/low-latitude-noctilucent-clouds/">record-breaking glimpses</a> of the rarest clouds in the skies. Stunning rippled blue clouds have been forming in the highest reaches of the atmosphere <a href="https://spaceweatherarchive.com/2019/06/23/extreme-noctilucent-clouds-over-europe/">over Europe</a> and <a href="https://spaceweatherarchive.com/2019/06/12/record-setting-noctilucent-clouds/">the USA</a>. These clouds are normally only seen around the poles, but this summer is set to be the best observing season in years – they have already been seen at the lowest latitudes ever recorded.</p>
<p>These clouds are called “noctilucent” or night-shining clouds, as we can only see them at dusk and dawn. They form extremely high up in the atmosphere, at about 80km (50 miles) above the Earth’s surface in a region called the mesosphere. This is about four <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/clouds/high-clouds/cirrus">times higher</a> than the highest clouds we normally see, the wispy cirrus clouds.</p>
<p>Because the air is so thin in this part of the atmosphere, it needs to be much colder than 0°C for water to freeze – <a href="https://www.atmos-chem-phys.net/4/2601/2004/">-120°C in fact</a>. We only see air temperatures this low in the mesosphere around the North or South poles when it is summer.</p>
<p>This strangely means that the part of the atmosphere constantly in sunlight is actually the coldest point in the atmosphere. This is because in the mesosphere, air flows away from the pole where it is summer towards the <a href="https://progearthplanetsci.springeropen.com/articles/10.1186/s40645-015-0035-8">one where it is winter</a>. This is replaced by air rising from lower in the atmosphere, which expands and cools, leading to the extremely low temperatures.</p>
<p>The water in noctilucent clouds is either transported up into the mesosphere from the lower atmosphere, or forms when methane in the mesosphere breaks down by absorbing the sun’s rays. But, for clouds to form, they also need some other kind of particles for the water to condense on to. In the lower atmosphere, these are normally aerosol particles from <a href="https://scied.ucar.edu/shortcontent/how-clouds-form">dust, sand and salt</a>.</p>
<p>But in the mesosphere, the main source of these particles is <a href="https://www.sciencedirect.com/science/article/pii/003206338290126X">from meteors</a>. As these lumps of space debris burn up in the higher layers of the atmosphere, they can leave behind trails of meteor dust. And at cold enough temperatures the water in the mesosphere can condense on this dust and grow into clouds.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/282263/original/file-20190702-126400-12eqa03.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/282263/original/file-20190702-126400-12eqa03.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/282263/original/file-20190702-126400-12eqa03.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282263/original/file-20190702-126400-12eqa03.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282263/original/file-20190702-126400-12eqa03.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282263/original/file-20190702-126400-12eqa03.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282263/original/file-20190702-126400-12eqa03.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282263/original/file-20190702-126400-12eqa03.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"></a>
<figcaption>
<span class="caption">Noctilucent clouds over Rabka-Zdrój, Poland, 2017.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Noctilucent_clouds_over_Rabka-Zdroj_17.07.02B.jpg">Radoslaw Ziomber/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Noctilucent clouds are so faint that they are only visible to us when the rest of the atmosphere is in darkness. This happens when the sun is below the horizon and, like a spotlight pointing upwards, illuminates only the higher regions of the atmosphere from below. The light that bounces off these clouds passes through the ozone layer before it gets to our eyes. Ozone absorbs red light and allows blue light to pass through, which is why these clouds take on a striking blue colour.</p>
<p>Noctilucent clouds can also show us how the atmosphere flows at the edge of space. The ripples seen in these clouds are from <a href="https://www.nasa.gov/multimedia/imagegallery/image_feature_484.html">atmospheric gravity waves</a>. These are just like waves on the surface of the ocean, but travel through the air. They form when air blows over mountains or in thunderstorms, and can travel all the way into the highest points in the atmosphere. Even though the air may look still in the mesosphere, these waves completely <a href="https://www.youtube.com/watch?v=6SqMCIKV364">dominate the flow,</a> and we can see these otherwise invisible waves in noctilucent clouds.</p>
<h2>What’s causing the record-breaking clouds?</h2>
<p>The lowest latitude at which noctilucent clouds are seen each year has been moving gradually south every year <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013JD021017">since at least 2002</a>. And in June 2019 the record was broken for the lowest point we have ever seen these clouds when they appeared not far from <a href="https://spaceweatherarchive.com/2019/06/17/low-latitude-noctilucent-clouds/">Los Angeles</a>. This was because the mesosphere was <a href="https://spaceweatherarchive.com/2019/06/19/mysterious-moisture-in-the-mesosphere/">strangely wet</a>, containing much more water than we usually see. This could be because a <a href="https://spaceweatherarchive.com/2019/06/19/mysterious-moisture-in-the-mesosphere/">giant planetary wave</a> was transporting cold air and moisture into the North Pole.</p>
<p>We are also in a deep solar minimum, the period of the sun’s 11-year cycle when it is least active. That means the ultraviolet radiation from the sun that usually destroys the water modules which form these clouds is <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/90JD02312">less intense</a>, so more of them can form.</p>
<p><a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL077719">Human emissions could also be a factor</a>. Over the past 130 years we have released more and more methane into the atmosphere, which means that more water modules are produced in the mesosphere. These clouds were once a rare sight for humans of the past to observe, first recorded only after the 1883 <a href="https://science.nasa.gov/science-news/science-at-nasa/2003/19feb_nlc/">eruption of Krakatoa</a> spewed an incredible amount of dust into the atmosphere. But since then they have become a more and more common sight.</p>
<p>So next time you’re out after dark, look up. You might just see the rarest clouds in the sky.</p><img src="https://counter.theconversation.com/content/119771/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jon Perrett 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>
‘Night-shining’ clouds normally found above the poles have now been seen as far south as Los Angeles.
Jon Perrett, PhD Candidate in Atmospheric Dynamics, University of Bath
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/110444
2019-02-11T13:27:25Z
2019-02-11T13:27:25Z
Curious Kids: how does thunder work? And why is it so loud?
<figure><img src="https://images.theconversation.com/files/255392/original/file-20190124-135148-15t9ins.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A thunderstorm builds over the Karoo in South Africa.</span> <span class="attribution"><span class="source">Sean Nel/Shutterstock</span></span></figcaption></figure><p><em>Curious Kids is a series for children in which we ask experts to answer questions from kids.</em></p>
<p><strong>How does thunder work, and why is it so loud? (Savaar, 6, Johannesburg)</strong></p>
<p>Thunder is the sound that lightning makes. So before I can explain how thunder works, I have to explain how lightning works, and clouds too – they all go together.</p>
<h2>Thunderclouds</h2>
<p>Not every cloud can make thunder and lightning. Thunderclouds are very tall – of course, from the earth you can’t always tell how tall the cloud is because you just see the bottom. But above that, it stretches up tall into the sky.</p>
<p><a href="https://theconversation.com/six-clouds-you-should-know-about-and-what-they-can-reveal-about-the-weather-93402">Clouds</a> are made of tiny water droplets. It’s so cold high up in the sky that ice crystals start to form inside the clouds. Then the ice crystals move to the top of the cloud and the water droplets stay near the bottom of the cloud. When they move past each other and rub against each other, they make <a href="https://www.livescience.com/4077-shocking-truth-static-electricity.html">static electricity</a>. </p>
<p>You can make static electricity by rubbing a balloon against your hair and then the static electricity makes your hair stand up. Sometimes, if you have socks on and you rub your feet on a carpet, then it makes a tiny shock when you touch somebody else. That is also static electricity.</p>
<p>The static electricity in the cloud makes the ice crystals positively charged and the water droplets negatively charged. If you have ever played with magnets, you will know that the positive side of a magnet is attracted to the negative side of another magnet – but it pushes away the positive side of another magnet. Opposites attract each other: those with the same charge (that is, positive or negative) push each other away. The same thing happens with the negatively charged water droplets near the bottom of the thunder cloud.</p>
<p>All the negative bits that collect near the bottom of the cloud are called electrons. Positive bits known as particles start to collect under the thunder cloud because they are attracted by the electrons near the bottom of the cloud. </p>
<p>The attraction of positive and negative bits is strong, so the electrons in the cloud start to make jagged fingers reaching down to the earth. As soon as the negative bits from the cloud connect with the positive bits from the earth, a huge current made of all those electrons flows to the earth – and that is the lightning flash you see. </p>
<p>The lightning flash heats the air around it so quickly that the air expands very fast. When you heat something, it gets bigger – it expands. The air around the lightning flash expands so fast that it makes a shock wave in the air. That shock wave is the thunder that you hear.</p>
<h2>A big noise</h2>
<p>Why is thunder so loud? It’s because the amount of electrical energy that flows from the cloud to the ground is so enormous: it’s like a very big waterfall of electricity. </p>
<p>The louder the sound that you hear, the closer you are to the lightning. Light travels through air much faster than sound. That’s why sometimes you see the lightning flash first and then you hear the thunder a few seconds later. If you see the lightning and hear the thunder immediately, then the lightning is very close to you. </p>
<p>Lightning is very dangerous.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/some-truths-about-lightning-when-thunder-roars-go-indoors-42098">Some truths about lightning: when thunder roars, go indoors</a>
</strong>
</em>
</p>
<hr>
<p>So, remember this important lesson: when thunder roars, go indoors. You can listen to the thunder getting louder as it gets closer, and softer as it moves away – and you’ll be safe from the lightning inside your house.</p>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to africa-curiouskids@theconversation.com. Please tell us your name, age, and which city you live in. We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/110444/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Estelle Trengove 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>
Why is thunder so loud? It’s because the amount of electrical energy that flows from the cloud to the ground is so enormous.
Estelle Trengove, Associate professor in electrical engineering, with a research interest in lightning safety, University of the Witwatersrand
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/102404
2018-09-12T23:47:42Z
2018-09-12T23:47:42Z
Curious Kids: where do clouds come from and why do they have different shapes?
<figure><img src="https://images.theconversation.com/files/235952/original/file-20180912-181254-s09p4f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sometimes air goes up past the condensation level then falls back below the condensation level, then up, then below, again and again. This creates clouds that are stripy, often with lines between the clouds. </span> <span class="attribution"><span class="source">Robert Lawry/Author provided</span>, <span class="license">Author provided</span></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky! You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em> </p>
<hr>
<blockquote>
<p><strong>Where do clouds come from and why do they all have different shapes? – Ryan Potts, age 7, Canberra.</strong></p>
</blockquote>
<hr>
<p>Hi Ryan, great question!</p>
<p>When it comes to understanding clouds, it helps first to understand water. </p>
<p>You know the water you drink out of a glass? That’s liquid water. There is also solid water, such as ice from the freezer or a slushy. </p>
<p>But water also exists as a gas. It’s called water vapour. You can’t can’t see, taste or feel this water but it’s everywhere. It’s all around you right now. Water vapour is in the air we breathe. When it’s warm and there is a lot of water vapour in the air, it can feel very sticky and sweaty.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-you-blink-when-there-is-a-sudden-loud-noise-close-by-99437">Curious Kids: Why do you blink when there is a sudden loud noise close by?</a>
</strong>
</em>
</p>
<hr>
<p>Now let’s go back to clouds.</p>
<p>For clouds to form, air needs to be cooled to a temperature at which the water vapour turns into liquid water. The best way to do this is to make the air rise, because the higher we go in the atmosphere the colder the temperature. There are many reasons air might lift, but one reason is because during the day the sun heats up the surfaces around us. </p>
<p>Imagine the oval near your school on a warm day. Starting in the morning the sun warms the surface of the oval and before too long the entire oval is warming up. </p>
<p>Warm air weighs less than cooler air. So a big bubble of warm air, filled with water vapour, slowly lifts off your school oval.</p>
<p>As the bubble of air (filled with water vapour) rises upwards, it starts to cool down. The higher it goes the cooler it gets. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/235950/original/file-20180912-181257-145rnm7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/235950/original/file-20180912-181257-145rnm7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235950/original/file-20180912-181257-145rnm7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235950/original/file-20180912-181257-145rnm7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235950/original/file-20180912-181257-145rnm7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235950/original/file-20180912-181257-145rnm7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235950/original/file-20180912-181257-145rnm7.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">Bubbles of warm air that have reached and passed beyond the condensation level.</span>
<span class="attribution"><span class="source">Robert Lawry</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Eventually, well off the ground above your school, the bubble of air has cooled so much that the water vapour turns into liquid water. We call this point the condensation level. When the water vapour turns into tiny specks of liquid water, a cloud forms.</p>
<p>Clouds are simply liquid water: very, very small drops of liquid water. So small in fact, that they can be held up in the air by rising air currents. </p>
<p>Back on the school oval: the day keeps getting warmer, more and more bubbles of rising air race upwards, cooling as they rise. When these bubbles of air reach the condensation level, more cloud forms.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/235947/original/file-20180912-181279-1llr875.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/235947/original/file-20180912-181279-1llr875.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/235947/original/file-20180912-181279-1llr875.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235947/original/file-20180912-181279-1llr875.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235947/original/file-20180912-181279-1llr875.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235947/original/file-20180912-181279-1llr875.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235947/original/file-20180912-181279-1llr875.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235947/original/file-20180912-181279-1llr875.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"></a>
<figcaption>
<span class="caption">A fluffy, bumpy cloud, formed by rising warm air currents.</span>
<span class="attribution"><span class="source">Robert Lawry</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Clouds formed by rising warm air currents are called “convection clouds”. Because of all the rising air coming up, these clouds can be bumpy on the top, sometimes producing very high thick clouds looking like cotton wool or cauliflower heads.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/235549/original/file-20180910-123110-1f9h0l0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/235549/original/file-20180910-123110-1f9h0l0.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=652&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235549/original/file-20180910-123110-1f9h0l0.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=652&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235549/original/file-20180910-123110-1f9h0l0.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=652&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235549/original/file-20180910-123110-1f9h0l0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=819&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235549/original/file-20180910-123110-1f9h0l0.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=819&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235549/original/file-20180910-123110-1f9h0l0.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=819&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<hr>
<p>When air rises very <em>slowly</em> and <em>gently</em> over an area and reaches the condensation level you get a cloud that is very smooth looking, like this:</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/235951/original/file-20180912-181245-1kpz2c6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/235951/original/file-20180912-181245-1kpz2c6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/235951/original/file-20180912-181245-1kpz2c6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235951/original/file-20180912-181245-1kpz2c6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235951/original/file-20180912-181245-1kpz2c6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235951/original/file-20180912-181245-1kpz2c6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235951/original/file-20180912-181245-1kpz2c6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235951/original/file-20180912-181245-1kpz2c6.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 smooth cloud.</span>
<span class="attribution"><span class="source">Robert Lawry</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Sometimes air goes up past the condensation level then falls back below the condensation level, then up, then below, again and again. This creates clouds that are stripy, often with lines between the clouds. </p>
<p>The way the air moves creates all the different clouds we see.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/235550/original/file-20180910-123134-x6s60c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/235550/original/file-20180910-123134-x6s60c.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=272&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235550/original/file-20180910-123134-x6s60c.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=272&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235550/original/file-20180910-123134-x6s60c.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=272&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235550/original/file-20180910-123134-x6s60c.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=342&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235550/original/file-20180910-123134-x6s60c.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=342&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235550/original/file-20180910-123134-x6s60c.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=342&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<hr>
<p>All the grey clouds that you see contain liquid water. However, as we discussed earlier, water can also exist as a solid (ice). Clouds that are very high are extremely cold and may appear pure white. These clouds contain ice.</p>
<p>I used to wonder what it would feel like to touch a cloud. Would it be fluffy? Hard, soft, warm or cold?</p>
<p>Well, we don’t need to wonder. Because every time we see fog, we are looking at cloud. </p>
<p>Fog is simply air that has cooled to the point where the water vapour has turned into liquid water. That forms fog – which is really just a cloud on the ground.</p>
<p>So next time you see fog, go outside and touch a cloud!</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/235946/original/file-20180912-181251-13apf3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/235946/original/file-20180912-181251-13apf3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/235946/original/file-20180912-181251-13apf3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235946/original/file-20180912-181251-13apf3n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235946/original/file-20180912-181251-13apf3n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235946/original/file-20180912-181251-13apf3n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235946/original/file-20180912-181251-13apf3n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235946/original/file-20180912-181251-13apf3n.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">Fog is really just cloud at ground level.</span>
<span class="attribution"><span class="source">Robert Lawry</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-dont-dogs-live-as-long-as-humans-93374">Curious Kids: Why don't dogs live as long as humans?</a>
</strong>
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<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:</em></p>
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?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"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age, and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/102404/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Lawry 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>
Clouds formed by rising warm air currents are called ‘convection clouds’. Because of all the rising air coming up, these clouds can be bumpy on top, sometimes looking like cotton wool or cauliflower.
Robert Lawry, Hydrologist, Australian Bureau of Meteorology
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/99964
2018-07-19T13:01:16Z
2018-07-19T13:01:16Z
Curious Kids: how do the clouds stay up in the sky?
<figure><img src="https://images.theconversation.com/files/228393/original/file-20180719-142423-4065mr.jpg?ixlib=rb-1.1.0&rect=201%2C0%2C2907%2C1702&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/windysydney/3766592456/sizes/l">windy_sydney/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children of all ages. The Conversation is asking young people to send in questions they’d like an expert to answer. All questions are welcome. Skip to the bottom to see how to enter.</em> </p>
<hr>
<blockquote>
<p><strong>How do the clouds stay up in the sky? – Samson, age four, London, UK.</strong></p>
</blockquote>
<hr>
<p>Thanks for the question, Samson. Believe it or not, I <a href="http://www.bbc.co.uk/guides/zsbwjxs">once weighed a cloud</a> and not many people can say they have done that! My scientist friends and I flew up into the sky in a giant airship, and went all the way through a fluffy, white cloud. Actually, it was very wet up there, because clouds are made up of billions of tiny water droplets. </p>
<p>As we flew through the cloud, we used lasers and other special scientific devices to measure how big the cloud was, and count how many tiny droplets of water were in it. Then, we did some maths and found that this cloud – which was actually pretty small, for a cloud – weighed four tonnes. That’s the same as two elephants! So, you’re right to wonder how such a heavy thing can stay up in the sky. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/gZEirvA-f64?wmode=transparent&start=140" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>There are three pieces to this puzzle, and the first one is gravity. Like everything on this planet, the tiny droplets that make up a cloud are drawn towards the Earth by gravity. But these droplets are so small that it’s hard for them to push past all the air beneath them. This means that they don’t fall very fast at all – in fact, only about <a href="http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/forces/forcesvelocityrev1.shtml">one centimetre per second</a>. And any wind blowing upwards can carry the droplets back up. </p>
<p>To fit the second piece of the puzzle, we’ll need to learn some proper chemistry; not too much, though, just enough for our story. Let me introduce the periodic table: a map of all the elements that we humans know about. Elements are the building blocks of all things – just like the smallest pieces of Lego, which you use to build bigger and more complex objects. </p>
<p>The periodic table is organised so that the lightest element of each row is always on the left. Hydrogen is the lightest of all elements, so you’ll find it at the top left. As you move along each row from left to right, the elements get heavier and heavier. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/228395/original/file-20180719-142408-xahaow.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/228395/original/file-20180719-142408-xahaow.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/228395/original/file-20180719-142408-xahaow.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=334&fit=crop&dpr=1 600w, https://images.theconversation.com/files/228395/original/file-20180719-142408-xahaow.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=334&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/228395/original/file-20180719-142408-xahaow.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=334&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/228395/original/file-20180719-142408-xahaow.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=420&fit=crop&dpr=1 754w, https://images.theconversation.com/files/228395/original/file-20180719-142408-xahaow.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=420&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/228395/original/file-20180719-142408-xahaow.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=420&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 periodic table of the elements (you might need to zoom in to see clearly).</span>
<span class="attribution"><a class="source" href="http://www.sbcs.qmul.ac.uk/iupac/AtWt/table.html">G. P. Moss/QMUL</a></span>
</figcaption>
</figure>
<p><em><a href="https://public.tableau.com/views/PeriodicTable_6/PeriodicTable?:embed=y&:display_count=yes&:showVizHome=no">Click here for a larger, interactive version.</a></em></p>
<p>Dry air is mostly made up of two gases, nitrogen and oxygen, plus a little bit of argon and tiny amounts of other gases. For now, we can just focus on nitrogen and oxygen. As you can see on the periodic table, the weight of a single nitrogen atom is 14, while oxygen weighs almost 16. </p>
<p>But neither nitrogen nor oxygen atoms like to be alone, so they almost always go in pairs – two atoms in a molecule, like two peas in a pod. Because of this, a nitrogen molecule usually weighs 28, and an oxygen molecule weighs 32. </p>
<p>As soon as we add water (H₂O) to the air, things get interesting. A water molecule is made up of two hydrogen atoms and one oxygen atom. Remember how hydrogen is the lightest element? Well, a single water molecule weighs just 18. So it’s actually lighter than a molecule of nitrogen or oxygen. That’s why moist air is lighter than dry air. </p>
<p>The next piece of the puzzle is temperature. As a rule, warm air rises up, while cold air sinks down. When water in the air is warmer, it’s more likely to be a gas. When it’s cooler, it prefers to take a liquid form, such as cloud droplets, rain, hail or snow. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/228402/original/file-20180719-142420-8hh4l8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/228402/original/file-20180719-142420-8hh4l8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/228402/original/file-20180719-142420-8hh4l8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/228402/original/file-20180719-142420-8hh4l8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/228402/original/file-20180719-142420-8hh4l8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/228402/original/file-20180719-142420-8hh4l8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/228402/original/file-20180719-142420-8hh4l8.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">Clouds often form at the top of mountains, where warm moist air blows upwards and then cools very quickly.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/clouds-over-ben-nevis-1125498203?src=6R9CrQmiVm--hVwj9Illjw-1-18">Shutterstock.</a></span>
</figcaption>
</figure>
<p>As warm, moist air rises, it gets cooler and cooler. And as it cools, more tiny water droplets form. You might expect the water droplets just to fall down as rain, but instead, something fun happens. You know how sweat cools our skin when it dries and changes from liquid into gas? Well, when gas turns into liquid, the exact opposite happens: it actually gives off heat. </p>
<p>This means that the cloud droplets are now surrounded by a tiny blanket of warm air. And what does warm air do? It rises! Not very far, though, because the air will cool again as it goes up.</p>
<p>Now our puzzle is complete: clouds are made up of tiny droplets of water, which are hardly affected by gravity, embedded in moist air, which is lighter than dry air. And they’re surrounded by tiny warm blankets of air, which lift them up towards the sky. That’s how clouds weighing billions of tonnes can stay afloat up in the sky. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-you-have-to-wear-a-helmet-in-space-92992">Curious Kids: Why do you have to wear a helmet in space?</a>
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<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?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">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em>This article has been updated to reflect the effects of air resistance and gravity on cloud droplets more accurately.</em></p><img src="https://counter.theconversation.com/content/99964/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jim McQuaid receives funding from NERC and the European Union</span></em></p>
Even a small cloud can weigh as much as four tonnes – but gravity, chemistry and temperature keep them floating in the sky.
Jim McQuaid, Associate Professor of Atmospheric Composition, University of Leeds
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/93450
2018-03-27T08:26:10Z
2018-03-27T08:26:10Z
How to discover a new ‘species’ of cloud – a sky spotter’s guide
<figure><img src="https://images.theconversation.com/files/211399/original/file-20180321-165580-1mj5vws.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Asperitas cloud over Newtonia, Missouri, US. </span> <span class="attribution"><a class="source" href="https://cloudappreciationsociety.org/asperitas-for-media/">© Elaine Patrick, Cloud Appreciation Society Member 31940.</a></span></figcaption></figure><p>Clouds form in a multitude of different shapes and sizes, their infinite combinations and position across the sky offering a visual drama in response to the light conditions. But despite their apparent randomness, a detailed naming convention is in place to categorise them. </p>
<p>When a cloud ultimately can’t be fitted into one of the many existing categories, it can be nominated for a classification of its own. In 2017, the World Meteorological Organisation (WMO) added 12 new types of cloud to the <a href="https://cloudatlas.wmo.int/home.html">International Cloud Atlas</a>, the world standard guide for cloud classification. And I worked as part of a small team investigating the science behind one newly categorised cloud, <a href="https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/wea.2996">Asperitas</a>, which exhibits wave-like perturbations, reminiscent of a rough sea in the base of the cloud.</p>
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<img alt="" src="https://images.theconversation.com/files/211412/original/file-20180321-165571-14jqubm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211412/original/file-20180321-165571-14jqubm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211412/original/file-20180321-165571-14jqubm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211412/original/file-20180321-165571-14jqubm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211412/original/file-20180321-165571-14jqubm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211412/original/file-20180321-165571-14jqubm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211412/original/file-20180321-165571-14jqubm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Asperitas over Erm, The Netherlands.</span>
<span class="attribution"><a class="source" href="https://cloudappreciationsociety.org/asperitas-for-media/">© Nienke Lantman, Cloud Appreciation Society Member 24009.</a></span>
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<p>Clouds are named using a Latin-based system proposed by <a href="https://www.rmets.org/weather-and-climate/observing/luke-howard-and-cloud-names">Luke Howard in 1803</a>, which laid the foundations for the WMO cloud atlas in 1939. Clouds are separated into ten basic genera, which are shown in the image below, and are described by their shape and altitude. </p>
<p>For example, Cumulus, from the Latin for heaped or puffed, describes clouds with a “cotton wool” appearance. Stratus describes a low-level layer cloud with a uniform, even base that covers much of the sky. Nimbus means rain-bearing, so a cloud called Nimbostratus is a layer cloud that produces rain or, sometimes, snow.</p>
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<a href="https://images.theconversation.com/files/211183/original/file-20180320-31617-1k89wzw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/211183/original/file-20180320-31617-1k89wzw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211183/original/file-20180320-31617-1k89wzw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1263&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211183/original/file-20180320-31617-1k89wzw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1263&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211183/original/file-20180320-31617-1k89wzw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1263&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211183/original/file-20180320-31617-1k89wzw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1587&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211183/original/file-20180320-31617-1k89wzw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1587&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211183/original/file-20180320-31617-1k89wzw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1587&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">Ten genera of cloud.</span>
<span class="attribution"><span class="source">Met Office (Crown copyright)</span></span>
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<p>Beyond the basic types provided by the genera, clouds may be sub-categorised into several species and varieties which, in turn, can also exhibit supplementary features. This leads to very precise descriptions of the clouds. For example, in the diagram below there are four Cumulus clouds: a) is Cumulus humilis, which is a species of cumulus having a short vertical extent; b) is Cumulus radiatus, a variety of cumulus arranged into lines across the sky; c) and d) are both Cumulus congestus species formed due to deep convection. However, d) has a layer cloud at the top, called Pileus, which is a further supplementary feature.</p>
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<img alt="" src="https://images.theconversation.com/files/211940/original/file-20180326-148729-nh316x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211940/original/file-20180326-148729-nh316x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211940/original/file-20180326-148729-nh316x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211940/original/file-20180326-148729-nh316x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211940/original/file-20180326-148729-nh316x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211940/original/file-20180326-148729-nh316x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211940/original/file-20180326-148729-nh316x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">a) Cumulus humilis (Image Copyright © Stephen Burt), b) Cumulus radiatus (KairoK via Wikimedia Commons), c) Cumulus congestus (Carptrash via Wikimedia Commons) and d) Cumulus congestus with Pileus (Marra38 via Wikimedia Commons).</span>
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<h2>Why the fuss?</h2>
<p>The WMO cloud atlas has only been updated three times in its 79 years, in 1975, 1987 and, most recently, 2017. Consequently, it is rare to have a new cloud recognised. Why, then, is it important to make additions? </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/six-clouds-you-should-know-about-and-what-they-can-reveal-about-the-weather-93402">Six clouds you should know about – and what they can reveal about the weather</a>
</strong>
</em>
</p>
<hr>
<p>Clouds provide an indication of the current state of the atmosphere and cloud type is reported by weather observers worldwide. Atmospheric observatories have long-term weather data for at least 100 years, which are important for learning about changes in our climate. Therefore, having a thorough and up-to-date identification system for clouds is important in describing weather and climate.</p>
<p>These rare updates occur for two principal reasons. First, some of the newly classified clouds, such as Cirrus homogenitus (meaning manmade cirrus), known commonly as contrails, have only been present since the age of the airliner. These additions to the cloud atlas, then, show human effects on the atmosphere.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/211305/original/file-20180321-165587-1fi9jus.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211305/original/file-20180321-165587-1fi9jus.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211305/original/file-20180321-165587-1fi9jus.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211305/original/file-20180321-165587-1fi9jus.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211305/original/file-20180321-165587-1fi9jus.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211305/original/file-20180321-165587-1fi9jus.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211305/original/file-20180321-165587-1fi9jus.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Contrails, otherwise known as Cirrus homogenitus (manmade cirrus).</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/159692186?src=xvmFXeRV-OprQcbFQnZhow-1-11&size=medium_jpg">Shutterstock</a></span>
</figcaption>
</figure>
<p>Second, with the advent of smartphone technology, the opportunities for the public to observe and share pictures of cloud formations has rapidly increased. The <a href="https://cloudappreciationsociety.org/">Cloud Appreciation Society</a> (CAS) has a cloud spotting app that lets its members upload pictures of clouds, which also have location data attached. This is a form of citizen science. It means that new cloud formations are now more likely to be reported than ever before. Campaigning by CAS founder, Gavin Prator-Pinney, led to Asperitas’ recognition as a supplementary feature in the latest WMO cloud atlas.</p>
<h2>New skies</h2>
<p>In my work at the University of Reading’s Department of Meteorology, the atmospheric conditions surrounding the CAS app sightings of Asperitas were investigated using satellite imagery, laser cloud recorders and weather forecasting models. Through this we found that Asperitas was a supplementary feature of a Stratus or Stratocumulus cloud. </p>
<p>The wavelike formation observed in the cloud base was found to be associated with atmospheric waves being channelled along the cloud base. These waves are a result of atmospheric motion and the effect of gravity, and are known as atmospheric gravity waves (not to be confused with gravitational waves). They function like ripples of water passing over the surface of a still lake, but instead pass through the atmosphere. </p>
<p>They are often generated by thunderstorms, jet streams and the passage of air over mountains. The interaction of the gravity wave along the cloud base gives Asperitas its wave-like features. Our paper fully describing this is available <a href="https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/wea.2996">here</a>.</p>
<p>Asperitas provides an excellent example of how citizen science can be used to make scientific discoveries. Our millions of smartphones are micro-measurement devices that can record the sky. Combined, they give an unprecedented atmospheric measurement system. So next time you’re out and about and spot a cloud you’ve never seen before, snap a picture and see if you can find it in the WMO cloud atlas. </p>
<p>You might just have witnessed a new cloud formation.</p><img src="https://counter.theconversation.com/content/93450/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Graeme Marlton 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>
Clouds can reveal a great deal about the world we live in. Here’s what happens when scientists find a whole new type.
Graeme Marlton, Postdoctoral Researcher, University of Reading
Licensed as Creative Commons – attribution, no derivatives.