tag:theconversation.com,2011:/ca-fr/topics/temperature-4977/articlesTemperature – La Conversation2024-02-15T22:55:49Ztag:theconversation.com,2011:article/2143462024-02-15T22:55:49Z2024-02-15T22:55:49Z20°C seems the optimal temperature for life on Earth to thrive – what does this mean in a warming world?<p>Have you ever wondered about the optimal temperature for life on Earth? For humans, 20°C is comfortable. Any warmer and we <a href="https://www.nature.com/articles/nature15725">work less efficiently</a> because releasing heat requires energy.</p>
<p>We know many species can live at much colder or warmer temperatures than humans. But our <a href="https://escholarship.org/uc/item/3mr1d0z4">systematic review</a> of published research found the thermal ranges of animals, plants and microbes living in air and water overlap at 20°C. Could this be a coincidence?</p>
<p>For all species, the relationship with temperature is an asymmetric bell-shaped curve. This means biological processes <a href="https://www.sciencedirect.com/science/article/abs/pii/S0956713512003210">increase in line with temperature</a>, reach a maximum, and then rapidly decline when it gets too hot. </p>
<p>Recently, a New Zealand research group noticed the number of marine species <a href="https://www.pnas.org/doi/abs/10.1073/pnas.2015094118">did not peak at the equator</a>, as has been commonly assumed. Rather, the number dipped, with peaks in the subtropics. </p>
<p>Follow-up <a href="https://www.pnas.org/doi/abs/10.1073/pnas.1916923117">studies</a> showed this dip has been getting deeper since the last ice age about 20,000 years ago. And it has been deepening faster due to global ocean warming. </p>
<p>When the number of species was plotted against the average annual temperature, there was a decline above 20°C. A second coincidence?</p>
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Read more:
<a href="https://theconversation.com/remote-pacific-coral-reef-shows-at-least-some-ability-to-cope-with-ocean-warming-new-study-211852">Remote Pacific coral reef shows at least some ability to cope with ocean warming – new study</a>
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<h2>Biological processes and biodiversity</h2>
<p>Research in Tasmania <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0153343">modelled the growth rates</a> of microbes and multi-cellular organisms and found the most stable temperature for their biological processes was also 20°C. </p>
<p>This “Corkrey model” built on <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/ecog.01948">other studies</a> showing 20°C was the most stable temperature for biological molecules. A third coincidence?</p>
<p>We teamed up with colleagues from Canada, Scotland, Germany, Hong Kong and Taiwan to search for general patterns in how temperature affects life. To our surprise, everywhere we looked we kept finding that, indeed, 20°C is a pivotal temperature for many measures of biodiversity, and not only for marine species. </p>
<p>Examples show temperatures warmer than around 20°C result in decreases in various crucial measures: </p>
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<li><p>marine and freshwater species’ tolerance of low oxygen</p></li>
<li><p>marine pelagic (open water living) and benthic (seabed living) algal productivity and fish predation rates on bait</p></li>
<li><p>global species richness in pelagic fishes, plankton, benthic invertebrates and fossil molluscs</p></li>
<li><p>and genetic diversity. </p></li>
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<p>There were also increased extinctions in the fossil record when temperatures exceeded 20°C.</p>
<h2>Increased species richness</h2>
<p>Globally, the range of temperatures that reef fishes and invertebrates live at is narrowest among species whose geographic distributions centred on 20°C. The same effect is seen in microbes.</p>
<p>While many species have evolved to live at warmer and colder temperatures, most species live at 20°C. Also, extinctions in the fossil record – including sponges, lamp shells, molluscs, sea mats (<a href="https://www.sciencelearn.org.nz/resources/147-bryozoans">bryozoans</a>), starfish and sea urchins, worms and crustaceans – were lower at 20°C.</p>
<p>As species evolve to live at temperatures above and below 20°C, their thermal niche gets wider. This means most can still live at 20°C even if they inhabit hotter or colder places.</p>
<p>The mathematical Corkrey model predicts that thermal breadth should be minimised, and biological processes most stable and efficient, at 20°C. In turn, this should maximise species richness across all domains of life, from bacteria to the multi-cellular plants and animals. The model therefore provides a theoretical explanation for this “20°C effect”.</p>
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Read more:
<a href="https://theconversation.com/marine-life-is-fleeing-the-equator-to-cooler-waters-history-tells-us-this-could-trigger-a-mass-extinction-event-158424">Marine life is fleeing the equator to cooler waters. History tells us this could trigger a mass extinction event</a>
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<h2>Predicting the effects of climate change</h2>
<p>That life seems centred around 20°C implies fundamental constraints that compromise the ability of tropical species to adapt to higher temperatures. </p>
<p>As long as species can shift their ranges to adapt to global warming, the 20°C effect means there will be local increases in species richness up to an annual average of 20°C. Above that, richness will decline. </p>
<p>This means the many marine species that can adapt to global warming by shifting their geographic distribution are unlikely to go extinct due to climate change. </p>
<p>However, land species may not be able to shift their geographic distributions so easily due to landscapes modified by cities, farming and other human infrastructures.</p>
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Read more:
<a href="https://theconversation.com/warming-oceans-may-force-new-zealands-sperm-and-blue-whales-to-shift-to-cooler-southern-waters-188522">Warming oceans may force New Zealand's sperm and blue whales to shift to cooler southern waters</a>
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<p>The 20°C effect is the simplest explanation for the above phenomena, including: trends in species richness and genetic diversity with temperature; extinction rates in the fossil record; biological productivity; optimal growth rate; and marine predation rates. </p>
<p>Despite the complexity of multi-cellular species, it is remarkable that the cellular-level temperature efficiencies are reflected in those other aspects of biodiversity.</p>
<p>Exactly why 20°C is pivotal and energy-efficient for cellular processes may be due to the molecular properties of water associated with cells. These properties may also be why ~42°C seems an absolute limit for most species. </p>
<p>A greater awareness of this 20°C effect may lead to new insights into how temperature controls ecosystem processes, species abundance and distribution, and the evolution of life.</p><img src="https://counter.theconversation.com/content/214346/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark John Costello received funding from the Royal Society of New Zealand-Te Apārangi that contributed to this research.. </span></em></p><p class="fine-print"><em><span>Ross Corkrey 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 ‘20°C effect’ could give us new insights into how temperature controls ecosystems and influences evolution – as well as how species might adapt to climate change.Mark John Costello, Professor, Faculty of Biosciences and Aquaculture, Nord UniversityRoss Corkrey, Adjunct Senior Researcher in Biostatistics, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2208182024-02-02T13:17:06Z2024-02-02T13:17:06ZHow can I get ice off my car? An engineer who studies airborne particles shares some quick and easy techniques<figure><img src="https://images.theconversation.com/files/572255/original/file-20240130-29-7n5wna.jpeg?ixlib=rb-1.1.0&rect=0%2C3%2C1024%2C763&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Condensation and cold combine to create that layer of ice on car windshields in winter. </span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Oblodzone_szyby_samochodu,_zima_2009_%28ubt%29.jpeg">Tomasz Sienicki/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>If you live somewhere that gets cold in the winter, you’ve probably seen cars parked outdoors covered in a thin layer of ice on a chilly morning. But what causes this frost, and how can you get rid of it quickly?</p>
<p>I’m a <a href="https://scholar.google.com/citations?user=xcpTqRYAAAAJ&hl=en">mechanical engineering professor</a> who studies how water vapor interacts with airborne particles under different atmospheric conditions. Frosty windshields are similar to some of the thermodynamic questions I study in the lab, and they’re also a pesky issue that I deal with every winter on my way to work. </p>
<h2>Windshield condensation</h2>
<p>The air in Earth’s atmosphere always contains a certain amount of water vapor, but there’s only so much water vapor the air can hold. Scientists call that limit 100% <a href="https://www.britannica.com/science/humidity">relative humidity</a>. <a href="https://www.weather.gov/arx/why_dewpoint_vs_humidity">The dew point</a> refers to the temperature at which relative humidity reaches 100%. </p>
<p>Wet air has high dew point temperature, while dry air has a low dew point temperature. With each degree drop in temperature, the air gets closer to its dew point temperature – or its water vapor carrying capacity. Any cooling after the dew point temperature has been reached causes <a href="https://sealevel.jpl.nasa.gov/ocean-observation/understanding-climate/air-and-water/">water to condense onto surfaces</a>, or form into fog.</p>
<p>Overnight, car windshields facing the cold dark sky are <a href="https://www.energy.gov/energysaver/principles-heating-and-cooling">radiatively cooled</a>, meaning they release heat out into their surrounding area in the form of visible and invisible light. As air comes in contact with the cold windshield, it can reach its dew point temperature. Then, the water vapor condenses onto the windshield.</p>
<p>When this radiative cooling drops the temperature on the windshield’s surface to <a href="https://www.britannica.com/science/freezing-point">below the freezing point</a>, 32 degrees Fahrenheit (zero degrees Celsius), the layer of condensed water on the windshield turns to frost. </p>
<h2>Defrosting your car</h2>
<p>To defrost an icy windshield, you can follow a few different approaches, some of which take longer and require more effort than others.</p>
<p>One option is to directly spray a small amount of warm liquid on the layer of frost to help melt it. For this approach to work, the spray liquid must be hot enough to raise the overall temperature of the frost layer to above <a href="https://pubchem.ncbi.nlm.nih.gov/ptable/melting-point/">the melting point</a>. But the temperature can’t be way hotter than the temperature of the glass or you’ll crack your windshield. </p>
<p>A better way to melt the ice without damaging your car is to spray your windows with a warm liquid that has a lower freezing point than water, like a mixture of rubbing alcohol and water. This warm mixture will melt the frost layer without heating up the glass, and the resulting liquid layer on the windshield will have a lower freezing point than water. It will remain liquid, and you can wipe it away with your windshield wipers. </p>
<p>Similar alcohol and water mixtures – <a href="https://www.britannica.com/science/glycol">glycol, for example</a> – are commonly used to maintain the <a href="https://mayekawa.es/images/pdf/ASHRAE_ENERGY_EFFICIENT_ICE_RINK_2015.pdf">icy surface of skating rinks</a>.</p>
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<figcaption><span class="caption">A mix of water and rubbing alcohol can melt ice on your windshield.</span></figcaption>
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<p>This approach can melt the ice reasonably quickly and easily, without too much effort. You don’t even have to turn on your car. </p>
<p>If you have a little more time, you can start the car and run <a href="https://www.lifewire.com/how-do-car-defrosters-work-534663">the air defrost system</a> to blow hot air – aim for above 80 degrees Fahrenheit – onto the inside of the windshield. This warms the windshield and will eventually melt the frost layer. Once you see some melting, you can use the windshield wipers to wipe the rest of the ice away. </p>
<p>This option consumes more energy, as your car will have to heat up the windshield, but it doesn’t require you to do much. </p>
<p>Using the defrost system to blow warm air toward the windshield will also help to clear the inside of the windshield when it gets fogged up from condensation. Otherwise, if it’s dry outside, you can also clear up windshield fog by opening the car window and letting in outside air.</p>
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<a href="https://images.theconversation.com/files/572257/original/file-20240130-23-r3f30r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A person wearing a winter jacket uses a scraper on their frost-covered windshield." src="https://images.theconversation.com/files/572257/original/file-20240130-23-r3f30r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/572257/original/file-20240130-23-r3f30r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/572257/original/file-20240130-23-r3f30r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/572257/original/file-20240130-23-r3f30r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/572257/original/file-20240130-23-r3f30r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=497&fit=crop&dpr=1 754w, https://images.theconversation.com/files/572257/original/file-20240130-23-r3f30r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=497&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/572257/original/file-20240130-23-r3f30r.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>
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<span class="caption">You can use an ice scraper to break the ice on your windshield into chunks, so your wiper blades can clean them off.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/ColoradoWeather/c8d71e03eb5144afad7c01e72eccf5c2/photo?Query=windshield%20wipers&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=296&digitizationType=Digitized&currentItemNo=17&vs=true&vs=true">AP Photo/David Zalubowski</a></span>
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<p>If you are in a hurry or need some exercise, you can use an ice scraper to break up frost on your windshield, creating smaller islands of ice. The windshield wiper can then mechanically dislodge the chunks by moving them around and melting them. This requires more energy on your part, but it doesn’t require much from your car.</p>
<p>If you have a relaxed start to your day, you can let the Sun warm the windshield and slowly melt the frost layer for you. This technique saves energy in every way imaginable.</p><img src="https://counter.theconversation.com/content/220818/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Suresh Dhaniyala 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>When you’re running late in the winter, you don’t want to have to spend time scraping frost off your windshield. Try some expert-recommended techniques instead.Suresh Dhaniyala, Bayard D. Clarkson Distinguished Professor of Mechanical and Aeronautical Engineering, Clarkson UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2183972023-11-27T20:33:32Z2023-11-27T20:33:32ZQuébec’s hardwood trees could move north. Here’s how that could affect the boreal forest landscape<figure><img src="https://images.theconversation.com/files/561078/original/file-20231101-23-x790gm.jpg?ixlib=rb-1.1.0&rect=2%2C2%2C994%2C663&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The combined impact of increasing temperatures (2 to 8°C by 2100) and forest development in the mixed boreal forest could modify the growth and distribution of temperate species.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>In Québec, there are two distinct types of forest: the northern temperate forest in the south, and the boreal forest in the north.</p>
<p>These forest ecosystems provide <a href="https://doi.org/10.1126/science.abf3903">many different and essential services</a> to the overall functioning of the planet, and to our economy. For example, the storage of large quantities of atmospheric carbon and habitats for many species, as well as a supply of raw materials to the wood industry, which is a pillar of the economies of both Québec and Canada.</p>
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<p><strong>This article is part of <em>La Conversation Canada’s</em> series <a href="https://theconversation.com/ca-fr/topics/foret-boreale-138017">The boreal forest: A thousand secrets, a thousand dangers</a></strong></p>
<p><br><em>La Conversation Canada invites you to take a virtual walk in the heart of the boreal forest. In this series, our experts focus on management and sustainable development issues, natural disturbances, the ecology of terrestrial wildlife and aquatic ecosystems, northern agriculture and the cultural and economic importance of the boreal forest for Indigenous peoples. We hope you have a pleasant — and informative — walk through the forest!</em></p>
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<p>As a doctoral student at Université du Québec en Abitibi-Témiscamingue (UQAT), I work on the colonization potential of sugar maple, yellow birch and red maple north of their range, in the mixed boreal forest. These three emblematic species of North American forests are of capital economic importance (for lumber, manufacture of plywood, pulp, or maple syrup for sugar maple) and contribute to the diversity of Québec’s forests.</p>
<h2>The mixed forest, between the temperate and boreal biomes</h2>
<p>The mixed forest is located in the transition zone (ecotone) between the boreal and temperate forests. </p>
<p>It refers to the region where these two forests meet, creating an area in which the <a href="https://www.researchgate.net/figure/Quebecs-vegetation-zones-subzones-and-bioclimatic-domains_fig16_269095315">characteristics of these two types of forest intermingle</a>. This amalgam is characterized by a complex coexistence between temperate hardwood species and the conifers typical of the boreal forest. </p>
<p>It is in this ecotone that temperate hardwoods reach the northern limit of their distribution. </p>
<h2>An uncertain future for the mixed boreal forest</h2>
<p>The combined impact of rising temperatures (2-8°C by 2100) and forest management in the boreal mixedwood forest could <a href="https://doi.org/10.1111/gcb.16014">alter the growth and distribution of temperate species</a>. The ecosystem services provided by these species could then be altered.</p>
<p>This transformation could be profound. Temperate hardwood species could migrate northwards and even become <a href="https://doi.org/10.1111/ecog.06525">dominant species</a> in boreal mixedwood <a href="https://cfs.nrcan.gc.ca/terms/read/1106">stands</a>.</p>
<p>Such a change in the forest composition of the boreal mixedwood forest could have major consequences for the forest industry, natural disturbance regimes and the biodiversity associated with the dominant tree species in the forests. However, there is still considerable uncertainty surrounding the factors that influence the successful establishment and growth of temperate hardwoods in the boreal mixedwood forest. </p>
<p>In order to get a complete picture of the future of the boreal mixedwood forest, it is essential to understand how the growth and establishment of temperate hardwoods within mixedwood stands is influenced by factors such as climate, soil characteristics and competitive interactions between trees.</p>
<h2>Hardwoods in the mixed boreal forest?</h2>
<p>As part of my doctoral work, we attempted to model competitive interactions between trees by taking into account the effects of climate change on their growth. This model simulates each tree in a stand. Each year, trees grow, reproduce and eventually die. The growth of each tree depends on the light the tree receives, competition for nutrients and space, and climate.</p>
<p>In our study, <a href="https://doi.org/10.1111/ecog.06525">published in the journal <em>Ecography</em></a>, we used this model to evaluate the capacity of temperate deciduous trees to establish themselves within mixed species stands in the boreal forest. To do this, we modelled typical mixed stands of the boreal forest, then integrated temperate deciduous species into these, giving the trees the opportunity to colonize these stands.</p>
<p>We showed that the three species of temperate hardwoods could colonize the stand. Yellow birch had a better colonization capacity, with its more numerous and lighter seeds which can disperse further. Red maple and sugar maple had similar abilities when it came to colonizing boreal mixed stands. However, sugar maple showed a better ability to colonize older forests, due to its superior growth under a closed canopy.</p>
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<a href="https://images.theconversation.com/files/557904/original/file-20231106-27-ukk16g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="snowy forest" src="https://images.theconversation.com/files/557904/original/file-20231106-27-ukk16g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/557904/original/file-20231106-27-ukk16g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557904/original/file-20231106-27-ukk16g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557904/original/file-20231106-27-ukk16g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557904/original/file-20231106-27-ukk16g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557904/original/file-20231106-27-ukk16g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557904/original/file-20231106-27-ukk16g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Temperate hardwood species could migrate north and even become dominant species within the forest’s stands.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
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<p>The establishment capacity of temperate hardwoods in the boreal mixed forest was higher in the youngest stands, as well as in stands after clear-cutting. Therefore, forest management and forest fires, by rejuvenating boreal mixed forest landscapes, could accelerate the northward migration of temperate tree species.</p>
<p>Increased temperatures due to climate change are not expected to increase the ability of temperate hardwoods to colonize boreal mixedwood forest stands, either in the current climate or under high climate forcing scenarios. This means that climate would not be a factor influencing the northern limit of distribution of temperate hardwood species, and therefore, that climate change should not have an immediate effect on the northern distribution of temperate hardwoods.</p>
<p>The soil types of the boreal mixed forest could, however, be a limit to the growth of temperate hardwoods. In clay soils, the growth of red maple and sugar maple would be poor and would not allow them to be competitive with the species already present, which tolerate clay very well.</p>
<p>Factors governing tree growth such as climate, soil and competition interact together and can <a href="https://cdnsciencepub.com/doi/10.1139/cjfr-2019-0319">make predictions about the future distribution of different tree species very complex</a>.</p>
<h2>Both positive and negative effects</h2>
<p>The establishment of temperate hardwoods in the boreal mixed forest could increase the complexity and diversity in stands. This could strengthen the <a href="https://doi.org/10.1111/1365-2435.13257">resistance and resilience of the boreal mixed forest to disturbances</a>.</p>
<p>The presence of temperate deciduous trees in mixed boreal forests could, in particular, attenuate spruce budworm epidemics, because the proportion of fir and spruce trees would be lower and these species would be <a href="http://link.springer.com/10.1007/s004420050441">more dispersed in the stands</a>.</p>
<p>The establishment of temperate deciduous trees will cause an increase in the proportion of deciduous trees in the landscape. This phenomenon, known as enfoliation, has been observed in the mixed boreal forest for the last 100 years and is mainly due to forest management. This envelopment could make epidemics of <a href="https://open.canada.ca/data/en/dataset/663c3ba7-9d26-4243-a6f4-de6866d1685b">forest livery</a> more severe. This defoliating insect attacks deciduous trees and especially aspen, paper birch and sugar maple.</p>
<p>Finally, wildfire regimes could be modified by the differences in flammability of hardwoods and conifers. The presence of temperate deciduous trees, which are less flammable than conifers, could lengthen fire cycles. This positive effect will, however, be associated with a major challenge for the forestry industry which manages the mixed boreal forest, since the industry is currently focused mainly on conifers.</p>
<h2>We can’t stop there</h2>
<p>Further modelling studies are needed to explore the impact of other factors that may influence the ability of temperate hardwoods to colonize boreal mixedwood forest.</p>
<p>In particular, we can think of the impact of soil and mycorrhizae (symbiosis between the roots of plants and fungi) on the germination and growth of trees, but also the effect of weather phenomena, such as late frosts, which can affect the survival and growth of young temperate trees.</p>
<p>Additionally, landscape scale modeling would be beneficial in order to be able to consider the topography of the land, a potentially influential factor on the ability of temperate hardwoods to establish further north.</p><img src="https://counter.theconversation.com/content/218397/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Fabio Gennaretti received funding from the Canada Research Chair in Dendroecology and Dendroclimatology (CRC-2021-00368) and from the Ministère des Ressources Naturelles et des Forêts (contract no. 142332177-D), and the Natural Sciences and Engineering Research Council of Canada (Discovery Grant no. RGPIN-2021-03553 and Alliance Grant no. ALLRP 557148-20, obtained in partnership with the MRNF and Resolute Forest Products).</span></em></p><p class="fine-print"><em><span>Maxence Soubeyrand ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>Research shows that the distribution of temperate hardwoods (sugar maple, red maple and yellow birch) could be shifting northward, which would have serious consequences for the boreal forest.Maxence Soubeyrand, Doctorant en écologie forestière, Université du Québec en Abitibi-Témiscamingue (UQAT)Fabio Gennaretti, Professeur en sciences forestière, Université du Québec en Abitibi-Témiscamingue (UQAT)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2101262023-07-21T12:28:31Z2023-07-21T12:28:31ZIs it really hotter now than any time in 100,000 years?<figure><img src="https://images.theconversation.com/files/538655/original/file-20230721-25-nhjvk8.jpg?ixlib=rb-1.1.0&rect=199%2C0%2C6214%2C4023&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Recent heat waves underscore Earth's new climate state.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/hot-arid-climate-landscape-royalty-free-image/1181240920">Sean Gladwell via Getty Images</a></span></figcaption></figure><p>As <a href="https://www.reuters.com/world/wmo-warns-risk-heart-attacks-deaths-heatwave-intensifies-2023-07-18/">scorching heat</a> grips large swaths of the Earth, a lot of people are trying to put the extreme temperatures into context and asking: When was it ever this hot before?</p>
<p>Globally, 2023 has seen some of the <a href="https://public.wmo.int/en/media/news/preliminary-data-shows-hottest-week-record-unprecedented-sea-surface-temperatures-and">hottest days</a> in modern measurements, but what about farther back, before weather stations and satellites?</p>
<p>Some news outlets have reported that daily temperatures hit a 100,000-year high. </p>
<p>As a <a href="https://scholar.google.com/citations?user=KpeykKsAAAAJ&hl=en">paleoclimate scientist</a> who studies temperatures of the past, I see where this claim comes from, but I cringe at the inexact headlines. While this claim may well be correct, there are no detailed temperature records extending back 100,000 years, so we don’t know for sure.</p>
<p>Here’s what we can confidently say about when Earth was last this hot.</p>
<h2>This is a new climate state</h2>
<p>Scientists concluded a few years ago that Earth had entered a new climate state not seen in more than 100,000 years. As fellow climate scientist <a href="https://scholar.google.com/citations?user=j8_CgoEAAAAJ&hl=en">Nick McKay</a> and I recently <a href="https://doi.org/10.5194/cp-18-911-2022">discussed in a scientific journal article</a>, that conclusion was part of <a href="https://www.cambridge.org/core/books/climate-change-2021-the-physical-science-basis/technical-summary/C7CCEAD271B10F328C6E50C03A0F4F02">a climate assessment report</a> published by the Intergovernmental Panel on Climate Change (IPCC) in 2021.</p>
<p>Earth was already more than 1 degree Celsius (1.8 Fahrenheit) warmer than preindustrial times, and the levels of greenhouse gases in the atmosphere were high enough to assure temperatures would stay elevated for a long time.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/538649/original/file-20230721-21-as2db8.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A time series chart shows a peak around 125,000 years ago and points to today's interglacial, showing temperatures close to the 1C warming level." src="https://images.theconversation.com/files/538649/original/file-20230721-21-as2db8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/538649/original/file-20230721-21-as2db8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=256&fit=crop&dpr=1 600w, https://images.theconversation.com/files/538649/original/file-20230721-21-as2db8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=256&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/538649/original/file-20230721-21-as2db8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=256&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/538649/original/file-20230721-21-as2db8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=321&fit=crop&dpr=1 754w, https://images.theconversation.com/files/538649/original/file-20230721-21-as2db8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=321&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/538649/original/file-20230721-21-as2db8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=321&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Earth’s average temperature has exceeded 1 degree Celsius (1.8 F) above the preindustrial baseline. This new climate state will very likely persist for centuries as the warmest period in more than 100,000 years. The chart shows different reconstructions of temperature over time, with measured temperatures since 1850 and a projection to 2300 based on an intermediate emissions scenario.</span>
<span class="attribution"><a class="source" href="https://cp.copernicus.org/articles/18/911/2022/">D.S. Kaufman and N.P. McKay, 2022, and published datasets</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Even under the most optimistic scenarios of the future – in which humans stop burning fossil fuels and reduce other greenhouse gas emissions – average global temperature will very likely remain at least 1 C above preindustrial temperatures, and possibly much higher, for multiple centuries.</p>
<p>This new climate state, characterized by a multi-century global warming level of 1 C and higher, can be reliably compared with temperature reconstructions from the very distant past.</p>
<h2>How we estimate past temperature</h2>
<p>To reconstruct temperatures from times before thermometers, paleoclimate scientists rely on information stored in a <a href="https://www.usgs.gov/programs/climate-research-and-development-program/science/paleoclimate-research">variety of natural archives</a>.</p>
<p>The most widespread archive going back many thousands of years is at the bottom of <a href="https://www.earth.ox.ac.uk/2017/01/using-lake-sediments-to-understand-past-climate/">lakes</a> and <a href="https://www.icm.csic.es/en/news/what-do-marine-sediments-tell-us-about-earths-climate">oceans</a>, where an assortment of <a href="https://www.icm.csic.es/en/news/what-do-marine-sediments-tell-us-about-earths-climate">biological, chemical and physical evidence</a> offers clues to the past. These materials build up continuously over time and can be analyzed by extracting a sediment core from the lake bed or ocean floor.</p>
<figure class="align-center ">
<img alt="Two female scientists aboard a boat examine a sediment core, with the layers clearly visible." src="https://images.theconversation.com/files/538741/original/file-20230721-22261-8jb0lp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/538741/original/file-20230721-22261-8jb0lp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/538741/original/file-20230721-22261-8jb0lp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/538741/original/file-20230721-22261-8jb0lp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/538741/original/file-20230721-22261-8jb0lp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/538741/original/file-20230721-22261-8jb0lp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/538741/original/file-20230721-22261-8jb0lp.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">University of Arizona scientist Ellie Broadman holds a sediment core from the bottom of a lake on Alaska’s Kenai Peninsula.</span>
<span class="attribution"><a class="source" href="https://theconversation.com/was-earth-already-heating-up-or-did-global-warming-reverse-a-long-term-cooling-trend-197788">Emily Stone</a></span>
</figcaption>
</figure>
<p>These <a href="https://theconversation.com/was-earth-already-heating-up-or-did-global-warming-reverse-a-long-term-cooling-trend-197788">sediment-based records</a> are rich sources of information that have enabled paleoclimate scientists to reconstruct past global temperatures, but they have important limitations.</p>
<p>For one, bottom currents and burrowing organisms can mix the sediment, blurring any short-term temperature spikes. For another, the timeline for each record is not known precisely, so when multiple records are averaged together to estimate past global temperature, fine-scale fluctuations can be canceled out.</p>
<p>Because of this, paleoclimate scientists are reluctant to compare the long-term record of past temperature with short-term extremes.</p>
<h2>Looking back tens of thousands of years</h2>
<p>Earth’s average global temperature has fluctuated between glacial and interglacial conditions in cycles lasting around 100,000 years, driven largely by slow and predictable <a href="https://climate.nasa.gov/news/2948/milankovitch-orbital-cycles-and-their-role-in-earths-climate/">changes in Earth’s orbit</a> with attendant changes in greenhouse gas concentrations in the atmosphere. We are currently in an interglacial period that began around 12,000 years ago as ice sheets retreated and greenhouse gases rose.</p>
<p>Looking at that 12,000-year interglacial period, global temperature averaged over multiple centuries might have <a href="https://www.nature.com/articles/s41597-020-0530-7">peaked roughly around 6,000 years ago</a>, but probably did not exceed the 1 C global warming level at that point, according to the <a href="https://www.cambridge.org/core/books/climate-change-2021-the-physical-science-basis/changing-state-of-the-climate-system/8B8FB442BA38A2C314ADD4136A9FE2E8">IPCC report</a>. <a href="https://www.nature.com/articles/s41586-021-03984-4">Another study</a> found that global average temperatures continued to increase across the interglacial period. This is a <a href="https://theconversation.com/was-earth-already-heating-up-or-did-global-warming-reverse-a-long-term-cooling-trend-197788">topic of active research</a>.</p>
<p>That means we have to look farther back to find a time that might have been as warm as today.</p>
<p>The last glacial episode lasted nearly 100,000 years. There is no evidence that long-term global temperatures reached the preindustrial baseline anytime during that period.</p>
<p>If we look even farther back, to the previous interglacial period, which peaked around 125,000 years ago, we do find evidence of warmer temperatures. The evidence suggests the long-term average temperature was <a href="https://www.cambridge.org/core/books/climate-change-2021-the-physical-science-basis/changing-state-of-the-climate-system/8B8FB442BA38A2C314ADD4136A9FE2E8">probably no more than 1.5 C (2.7 F)</a> above preindustrial levels – not much more than the current global warming level.</p>
<h2>Now what?</h2>
<p>Without rapid and sustained reductions in greenhouse gas emissions, the Earth is currently on course to reach temperatures of <a href="https://www.cambridge.org/core/books/climate-change-2021-the-physical-science-basis/summary-for-policymakers/CBBF8E93AC3A66A16D29C14D0815A45A">roughly 3 C (5.4 F)</a> above preindustrial levels by the end of the century, and possibly quite a bit higher.</p>
<p>At that point, we would need to <a href="https://www.pnas.org/doi/10.1073/pnas.1809600115">look back millions</a> of years to find a climate state with temperatures as hot. That would take us back to the <a href="https://www.nps.gov/subjects/geology/time-scale.htm">previous geologic epoch</a>, the Pliocene, when the Earth’s climate was a distant relative of the one that sustained the rise of agriculture and civilization.</p><img src="https://counter.theconversation.com/content/210126/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Darrell Kaufman receives funding from the US National Science Foundation.</span></em></p>Long before thermometers, nature left its own temperature records. A climate scientist explains how ongoing global warming compares with ancient temperatures.Darrell Kaufman, Professor of Earth and Environmental Sciences, Northern Arizona UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2087402023-07-13T12:38:15Z2023-07-13T12:38:15ZWeather forecast accuracy is crucial in a heat wave – 1 degree can mean the difference between life and death<figure><img src="https://images.theconversation.com/files/536937/original/file-20230711-26-jekcvf.jpg?ixlib=rb-1.1.0&rect=0%2C44%2C6000%2C3943&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Extreme heat can put lives at risk, making accurate forecasts essential for people working outdoors.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/exhausted-construction-worker-at-construction-site-royalty-free-image/1334826526">FG Trade/E+ via Getty Images</a></span></figcaption></figure><p>Weather forecasts have gotten quite good over the years, but their temperatures aren’t always spot on – and the result when they underplay extremes can be lethal. <a href="https://doi.org/10.3386/w31361">Even a 1-degree difference</a> in a forecast’s accuracy can be the difference between life and death, our research shows. </p>
<p>As <a href="https://scholar.google.com/citations?user=614D6AEAAAAJ&hl=en">economists</a>, <a href="https://scholar.google.com/citations?user=9VrtHcIAAAAJ&hl=en">we have</a> <a href="https://scholar.google.com/citations?user=o7NswrkAAAAJ&hl=en">studied</a> how people use forecasts to manage weather risks. In a new working paper for the National Bureau of Economic Research, we looked at how human survival <a href="https://doi.org/10.3386/w31361">depends on the accuracy of temperature forecasts</a>, particularly during heat waves like <a href="https://abcnews.go.com/US/37-million-americans-alert-dangerous-heat/story?id=100959311">large parts of the U.S.</a> have been experiencing in recent days.</p>
<p>We found that when the forecasts underplayed the risk, even small forecast errors led to more deaths.</p>
<p>Our results also show that improving forecasts pays off. They suggest that making forecasts 50% more accurate would save 2,200 lives per year across the country and would have a net value that’s nearly <a href="https://www.everycrsreport.com/files/2022-06-17_IF11914_d3e26afb6fbd9006c54580150fc833d6f1614231.pdf">twice the annual budget</a> of the National Weather Service.</p>
<h2>Forecasts that are too mild lead to more deaths</h2>
<p>In the U.S. alone, the National Oceanic and Atmospheric Administration issues <a href="https://www.noaa.gov/sites/default/files/2021-06/NOAABlueBook2022_final.pdf">1.5 million forecasts per year</a> and collects around 76 billion weather observations that help it and private companies make better forecasts.</p>
<p>We examined data on <a href="https://www.cdc.gov/">every day’s deaths</a>, weather and National Weather Service forecast in every U.S county from 2005 to 2017 to analyze the impact of those forecasts on human survival. </p>
<p>We then compared deaths in each county over the week following a day with accurate forecasts to deaths in the same county over the week following a day with inaccurate forecasts but the same weather. Because weather conditions were the same, any differences in mortality could be attributed to how people’s reactions to forecasts affected their chance of dying in that weather.</p>
<figure class="align-center ">
<img alt="Cars drive under a sign reading: Extreme heat. Save Power 4-9PM. Stay Cool" src="https://images.theconversation.com/files/536939/original/file-20230711-29-ur6l4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536939/original/file-20230711-29-ur6l4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536939/original/file-20230711-29-ur6l4r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536939/original/file-20230711-29-ur6l4r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536939/original/file-20230711-29-ur6l4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536939/original/file-20230711-29-ur6l4r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536939/original/file-20230711-29-ur6l4r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Vehicles on the 110 Freeway pass warning signs on Sept. 2, 2022, during a heat wave with temperatures as high as 112 degrees Fahrenheit (44 Celsius) in the Los Angeles suburbs.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/vehicles-drive-past-a-sign-on-the-110-freeway-warning-of-news-photo/1242895722?adppopup=true">Patrick T. Fallon/AFP via Getty Images</a></span>
</figcaption>
</figure>
<p>We found similar results when the forecast was wrong on hot days with temperatures above 86 degrees Fahrenheit (30 Celsius) and on cold days with temperatures below freezing. Both summer days that were hotter than forecast and winter days that were colder <a href="https://www.nber.org/papers/w31361">had more deaths</a>. Forecasts that went the other way and overestimated the summer heat or winter cold had little impact. </p>
<p>That doesn’t mean forecasters should exaggerate their forecasts, however. If people find that their forecasts are consistently off by a degree or two, they might change how they use forecasts or come to trust them less, leaving people at even higher risk.</p>
<h2>People are paying attention</h2>
<p>People do pay attention to forecasts and adjust their activities.</p>
<p>The <a href="https://www.bls.gov/tus/overview.htm">American Time Use Survey</a>, conducted continuously for the U.S. Bureau of Labor Statistics, shows what Americans across the country are doing on any given day. We found that on days when the forecast called for temperatures to be milder than they turned out to be – either cooler on a hot day or warmer on a cold day – people in the survey spent more time on leisure and less in home or work settings.</p>
<p><a href="https://www.eia.gov/">Electricity use</a> also varies in sync with forecasts, suggesting that people’s use of air conditioning does not just respond to the weather outside but also depends on how they planned for the weather outside.</p>
<figure class="align-center ">
<img alt="A man holds something over his head to shield the sun from his forehead. Other people walking across the bridge on a bright, sunny day have umbrellas and hats." src="https://images.theconversation.com/files/536940/original/file-20230711-23-mdhw2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536940/original/file-20230711-23-mdhw2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536940/original/file-20230711-23-mdhw2x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536940/original/file-20230711-23-mdhw2x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536940/original/file-20230711-23-mdhw2x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536940/original/file-20230711-23-mdhw2x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536940/original/file-20230711-23-mdhw2x.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 man shields his head from the Sun as he walks across New York’s Brooklyn Bridge on a hot summer day in 2018.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/man-shields-his-head-from-the-sun-as-he-walks-across-the-news-photo/987271692">Drew Angerer/Getty Images</a></span>
</figcaption>
</figure>
<p>However, forecasts are not used equally across society. Deaths among racial minorities are less sensitive to forecast errors, we found. That could be due in part to having less flexibility to act on forecasts, or not having access to forecasts. We will dig into this difference in future work, as the answer determines how the National Weather Service can best reach everyone.</p>
<h2>The value of better forecasts</h2>
<p>It’s clear that people use forecasts to make decisions that can matter for life and death – <a href="https://www.texasmonthly.com/travel/texas-hiking-heat-deaths-big-bend-palo-duro/">when to go hiking</a>, for example, or whether to encourage an elderly neighbor to <a href="https://theconversation.com/saving-lives-from-extreme-heat-lessons-from-the-deadly-2021-pacific-northwest-heat-wave-206737">go to a cooling center</a>.</p>
<p>So, what is the value of accurate forecasts?</p>
<p>We combined our theoretical model with <a href="https://www.epa.gov/environmental-economics/mortality-risk-valuation">federal cost-benefit estimates</a> of how people value improvements in their chances of survival. From those, we estimated people’s willingness to pay for better forecasts. That calculation accounts for the risk of dying from extreme weather and for the costs of using forecasts to reduce their risk of dying, such as the costs of altering work and play schedules or using electricity.</p>
<p>The result shows that 50% more accurate forecasts are <a href="https://doi.org/10.3386/w31361">worth at least US$2.1 billion per year</a> based on the mortality benefits alone. In comparison, the 2022 <a href="https://www.everycrsreport.com/files/2022-06-17_IF11914_d3e26afb6fbd9006c54580150fc833d6f1614231.pdf">budget of the National Weather Service</a> was less than $1.3 billion.</p>
<p>Weather forecasts have gotten steadily better over the past decades. About 68% of the next-day temperature forecasts now have an error of less than 1.8 degrees. Our results suggest investing in improved forecast accuracy would probably be worth the cost. </p>
<p>Past improvements have come from better models, better observations and better computers. Future improvements could come from similar channels or from applying recent innovations in <a href="https://theconversation.com/ai-and-machine-learning-are-improving-weather-forecasts-but-they-wont-replace-human-experts-182498">machine learning</a> and <a href="https://www.nature.com/articles/d41586-023-02084-9">artificial intelligence</a> to weather prediction and communication.</p>
<p>Climate change will <a href="https://nca2018.globalchange.gov/">increase the frequency of extremely hot days</a>, which are <a href="https://climate.nasa.gov/explore/ask-nasa-climate/3151/too-hot-to-handle-how-climate-change-may-make-some-places-too-hot-to-live/">especially important for human health</a> and survival to forecast accurately. Climate change will make the weather weirder, but weird weather can do less harm when we can see it coming.</p><img src="https://counter.theconversation.com/content/208740/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Derek Lemoine receives funding from Global Research Institute, is a Research Associate at the National Bureau of Economic Research, and is an Associate Fellow at the Centre for Economic Policy Research.</span></em></p><p class="fine-print"><em><span>Jeff Shrader receives funding from the National Science Foundation. </span></em></p><p class="fine-print"><em><span>Laura Bakkensen 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>Three economists looked at years of temperature and death data and calculated the costs when forecasts miss the mark.Derek Lemoine, Associate Professor of Economics, University of ArizonaJeffrey Shrader, Assistant Professor of International and Public Affairs, Columbia UniversityLaura Bakkensen, Associate Professor of Economics and Policy, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2094762023-07-11T12:30:09Z2023-07-11T12:30:09ZHow climate change intensifies the water cycle, fueling extreme rainfall and flooding – the Northeast deluge was just the latest<figure><img src="https://images.theconversation.com/files/536673/original/file-20230710-23-sbqqq8.jpg?ixlib=rb-1.1.0&rect=60%2C84%2C7981%2C5268&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">People were trapped in stores as floodwater swept through Highland Falls, N.Y., on July 9, 2023.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/NortheastFlooding/dca30eef58f149d493b8770a86c59d4c/photo">AP Photo/John Minchillo</a></span></figcaption></figure><p>Powerful storm systems that hit the U.S. Northeast starting July 9, 2023, dumped <a href="https://twitter.com/cory_kowitz/status/1678276566135246849">close to 10 inches of rain</a> on New York’s Lower Hudson Valley in less than a day and sent mountain rivers spilling over their banks and <a href="https://weather.com/news/news/2023-07-11-vermont-montpelier-ludlow-new-york-flooding">into towns across Vermont</a>. Vermont <a href="https://www.mynbc5.com/article/gov-scott-issues-state-of-emergency-in-anticipation-of-flash-flooding-sunday-and-monday/44485743">Gov. Phil Scott said</a> he hadn’t seen rainfall like it since <a href="https://www.burlingtonfreepress.com/story/life/2021/08/27/hurricane-irene-vt-tropical-storm-phish-concert-10-years-later-storm-preparedness-winooski-river/5599530001/">Hurricane Irene devastated the region</a> in 2011. </p>
<p>Extreme water disasters like this have disrupted lives in countries around the world in the past few years, from the Alps and <a href="https://www.science.org/content/article/europe-s-deadly-floods-leave-scientists-stunned">Western Europe</a> to <a href="https://disasterphilanthropy.org/disasters/2022-pakistan-floods/">Pakistan</a>, <a href="https://www.cnn.com/2022/06/22/india/bangladesh-india-floods-death-toll-intl-hnk/index.html">India</a> and <a href="https://www.bbc.com/news/world-australia-61991112">Australia</a>, along with <a href="https://theconversation.com/looking-back-on-americas-summer-of-heat-floods-and-climate-change-welcome-to-the-new-abnormal-190636">several U.S. states in 2022</a> and <a href="https://theconversation.com/historic-flooding-in-fort-lauderdale-was-a-sign-of-things-to-come-a-look-at-who-is-most-at-risk-and-how-to-prepare-204101">2023</a>.</p>
<p>The role of climate change is becoming increasingly evident in these types of deluges.</p>
<figure class="align-center ">
<img alt="Extreme rainfall flooded streets along the Hudson River, which is in the background. Water still pours down a hillside." src="https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536675/original/file-20230710-29-wanwql.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Cars were stranded in floodwater on the campus of the United States Military Academy at West Point, N.Y., on July 10, 2023.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/NortheastFlooding/e39624eb3cca4e1d849e0b74679ca4c6/photo">U.S. Military Academy via AP</a></span>
</figcaption>
</figure>
<p>Studies by scientists around the world show that the water cycle has been intensifying and will continue to intensify as the planet warms. An <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">international climate assessment</a> I co-authored in 2021 for the Intergovernmental Panel on Climate Change reviewed the research and laid out the details.</p>
<p>It documented an increase in both wet extremes, including more intense rainfall over most regions, and dry extremes, including drying in the Mediterranean, southwestern Australia, southwestern South America, South Africa and western North America. It also shows that both wet and dry extremes will continue to increase with future warming.</p>
<h2>Why is the water cycle intensifying?</h2>
<p>Water cycles through the environment, moving between the atmosphere, ocean, land and reservoirs of frozen water. It might fall as rain or snow, seep into the ground, run into a waterway, join the ocean, freeze or evaporate back into the atmosphere. In recent decades, there has been an <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">overall increase in the rates</a> of precipitation and evaporation.</p>
<p>A number of factors are intensifying the water cycle, but one of the most important is that warming temperatures raise the upper limit on the amount of moisture in the air. That increases the potential for more rain.</p>
<p><iframe id="zBAAz" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/zBAAz/5/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>This aspect of climate change is confirmed across <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">all of our lines of evidence</a>. It is expected from basic physics, projected by computer models, and it already shows up in the observational data as a general increase of rainfall intensity with warming temperatures.</p>
<p>Understanding this and other changes in the water cycle is important for more than preparing for disasters. Water is an essential resource for all ecosystems and human societies, and particularly agriculture.</p>
<h2>What does this mean for the future?</h2>
<p>An intensifying water cycle means that both wet and dry extremes and the general variability of the water cycle will increase, although not uniformly around the globe.</p>
<p>Rainfall intensity is <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">expected to increase for most land areas</a>, but the largest increases in dryness are expected in the Mediterranean, southwestern South America and western North America.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Maps showing precipitation projections and warming projections at 1.5 and 3 degrees Celsius." src="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Annual average precipitation is projected to increase in many areas as the planet warms, particularly in the higher latitudes.</span>
<span class="attribution"><a class="source" href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">IPCC Sixth Assessment Report</a></span>
</figcaption>
</figure>
<p>Globally, daily extreme precipitation events will likely intensify by about <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">7% for every 1 degree Celsius</a> (1.8 degrees Fahrenheit) that global temperatures rise.</p>
<p>Many other important aspects of the water cycle <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">will also change</a> in addition to extremes as global temperatures increase, the report shows, including reductions in mountain glaciers, decreasing duration of seasonal snow cover, earlier snowmelt and contrasting changes in monsoon rains across different regions, which will impact the water resources of billions of people.</p>
<h2>What can be done?</h2>
<p>One common theme across these aspects of the water cycle is that <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">higher greenhouse gas emissions lead to bigger impacts</a>.</p>
<p>The IPCC does not make policy recommendations, but the results show what the implications of different choices are likely to be.</p>
<p>One thing the <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">scientific evidence in the report</a> clearly tells world leaders is that limiting global warming to the international target of 1.5 C (2.7 F) will require immediate, rapid and large-scale reductions in greenhouse gas emissions.</p>
<p>As the evidence shows, every fraction of a degree matters.</p>
<p><em>This updates an <a href="https://theconversation.com/climate-change-is-intensifying-the-water-cycle-bringing-more-powerful-storms-and-flooding-heres-what-the-science-shows-187951">article originally published</a> July 29, 2022, with flash flooding in the Northeast.</em></p><img src="https://counter.theconversation.com/content/209476/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mathew Barlow received travel funding from the US government to attend three IPCC lead author meetings.</span></em></p>Parts of New York’s Hudson Valley were hit with 10 inches of rain, and the mountains of Vermont – where runoff can quickly turn deadly – saw some its worst flooding since Hurricane Irene.Mathew Barlow, Professor of Climate Science, UMass LowellLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2071892023-06-29T12:17:28Z2023-06-29T12:17:28ZThink being a NASCAR driver isn’t as physically demanding as other sports? Think again<figure><img src="https://images.theconversation.com/files/534663/original/file-20230628-29-pxt28c.jpg?ixlib=rb-1.1.0&rect=13%2C17%2C2982%2C2056&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Race car drivers compete in full-body safety gear while sitting in a piping hot car, which puts tremendous strain on the heart.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/driver-michael-gallegos-climbs-behind-the-wheel-during-the-news-photo/77354033?adppopup=true">Grant Halverson/Getty Images for NASCAR</a></span></figcaption></figure><p>Imagine an NBA game played outdoors. In August. In Phoenix. Tip-off is at noon. There are no timeouts. There is no halftime. There are no substitutions. And players must wear snowsuits, gloves, and ski masks. </p>
<p>Sounds ridiculous, right? </p>
<p>Yet race car drivers routinely compete under similar conditions.</p>
<p>On July 1, 2023, for the first time in over 60 years, NASCAR, the nation’s premier stock car series, will hold a race on the streets of a U.S. city at the <a href="https://www.nascarchicago.com/racing/">Grant Park 220 in Chicago</a>.</p>
<p>The fans who attend are sure to appreciate the sound, speed and spectacle. But how many truly grasp the physical and mental strain placed on the drivers?</p>
<p>Our research team from the University of Florida and Michigan State University is collaborating with NASCAR to better understand the stressors drivers experience on the track.</p>
<p>We’ve learned that professional drivers need extraordinary physical and mental stamina to compete in major racing series such as NASCAR, IndyCar and Formula One. Our data shows the metabolic demands of <a href="https://doi.org/10.1249/MSS.0000000000002070">auto racing and basketball are similar</a>. But unlike other athletes, race car drivers compete in full-body safety gear while sitting in a piping hot car for hours at a time.</p>
<h2>Not your mom’s minivan</h2>
<p>Race car drivers face unique challenges that require strength, endurance and hand-eye coordination.</p>
<p>First, the physical effort of driving a race car is much greater than that of driving your family car. </p>
<p><a href="https://www.roadandtrack.com/motorsports/news/a18270/you-think-driving-an-indy-car-is-easy/">Turning and braking require more force</a> due to the high speeds and the unique engineering of race cars. Drivers control the vehicle <a href="https://www.formula1.com/en/latest/video.2022-italian-grand-prix-williams-mechanics-help-exhausted-nyck-de-vries-out-of-the-car-after-his-points-scoring-f1-debut.1743691636627328562.html">by constantly engaging</a> the muscles of the arms, upper body and legs.</p>
<p>“There’s tremendous kick-back through the steering wheel,” IndyCar driver Dario Franchitti <a href="https://www.roadandtrack.com/motorsports/news/a18270/you-think-driving-an-indy-car-is-easy/">said in a 2012 interview</a>, “and there’s no power steering, so every movement of the wheel requires a lot of energy.”</p>
<p>After being hooked up to sensors to track the stresses and strains he endured a race, Franchitti learned he needed to generate 35 pounds of force just to steer, and 135 pounds of force to brake.</p>
<p>“Imagine a string tied to your hand where you have to pull that 35 pounds up or down constantly,” he added.</p>
<p>Also, fast turns and abrupt braking create accelerative forces, <a href="https://www.geotab.com/blog/what-is-g-force/">known as G-forces</a>. Like a jet fighter pilot in a dogfight, intense G-forces make it hard for racers to maintain their posture and promote muscle fatigue. It can even become <a href="https://us.motorsport.com/f1/news/magnussen-says-his-neck-just-broke-in-q3-in-jeddah/9364564/">impossible to hold their heads up</a>. </p>
<p>For these reasons, drivers undergo rigorous training to <a href="https://www.doi.org/10.1249/MSS.0000000000001961">strengthen key muscle groups</a> in the neck, upper body and legs while working to improve their cardiovascular fitness. </p>
<p>Heat is also a major challenge for driver athletes. Like any exercise, the work of driving a race car causes the body to generate metabolic heat. In most sports, athletes wear lightweight clothes that promote cooling by convection and sweat evaporation. </p>
<p>Not so in auto racing. Driver body <a href="https://doi.org/10.1016/j.jtherbio.2014.06.001">heat is trapped by the safety gear</a> worn during competition to protect against fire in case of a crash. The gear includes long fireproof undershirt and underpants, full-body fire suit, socks and driving shoes, gloves, a fireproof balaclava, and a full-face helmet with closed eye shield.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/6W6OswDJZJ8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Formula One driver Nigel Mansell faints at the 1984 Dallas Grand Prix, which was held on a day where temperatures exceeded 100 degrees Fahrenheit (38 Celsius).</span></figcaption>
</figure>
<h2>Bodies pushed to the limit</h2>
<p>To make matters worse, drivers compete in what’s essentially a moving oven. </p>
<p>A massive amount of heat is generated by the race car engine, exhaust, brakes and tires. These sources heat the cockpit and the driver, <a href="https://doi.org/10.1249/MSS.0000000000001997">especially in cars with roofs</a> like stock cars. In summer, cockpit temperatures can exceed 135 degrees Fahrenheit (57 Celsius), leading to profuse sweating, dehydration and <a href="https://f1i.com/images/350956-mansells-dallas-gp-push-and-coast.html">even heatstroke</a>. </p>
<p>Most race cars lack air conditioning. Instead, <a href="https://www.hendrickmotorsports.com/news/articles/100361/how-drivers-stay-cool-in-the-car-during-summer-months">technologies used to combat the heat</a> include hoses that bring fresh air into driver helmets and cool-shirts worn by drivers. <a href="https://www.formulasantander.com/how-formula-1-drivers-stay-hydrated-during-the-race/">In-car drink systems</a> can also provide fluids for re-hydration.</p>
<p>Drivers and other endurance athletes metabolize oxygen to power their muscles and regulate body temperature. Comparing data across sports, my colleague and I found that metabolic demands of auto racing are <a href="https://doi.org/10.1249/MSS.0000000000002070">similar to basketball, soccer or boxing</a>.</p>
<p>Delivering more oxygen to the driver’s body puts stress on the heart. Drivers often <a href="https://doi.org/10.3357/asem.1483.2008">maintain near-maximal heart rates</a> while racing for hours at a time. </p>
<p>Beyond the heat, other aspects of racing also put demands on the heart. </p>
<p>First, there is speed. The <a href="https://journals.lww.com/acsm-msse/Fulltext/2002/12000/Physiological_responses_to_high_speed,_open_wheel.33.aspx">faster a race car is driven</a> on a given track, the higher the driver’s heart rate due to greater physical and mental effort. Configuration of the race track is also important. Compared to oval tracks, heart rates are <a href="https://journals.lww.com/acsm-msse/Fulltext/2002/12000/Physiological_responses_to_high_speed,_open_wheel.33.aspx">higher on road courses and street races</a>. This reflects the extra work required for hard braking and sharp turns.</p>
<figure class="align-center ">
<img alt="Fans watch from balconies as cars zip along a city street." src="https://images.theconversation.com/files/534666/original/file-20230628-29-f5h5gz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534666/original/file-20230628-29-f5h5gz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534666/original/file-20230628-29-f5h5gz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534666/original/file-20230628-29-f5h5gz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534666/original/file-20230628-29-f5h5gz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534666/original/file-20230628-29-f5h5gz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534666/original/file-20230628-29-f5h5gz.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">Street courses like the Monaco Grand Prix add extra strain on drivers due to the prevalence of sharp turns.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/daniel-ricciardo-of-australia-driving-the-aston-martin-red-news-photo/962946726?adppopup=true">Dan Istitene/Getty Images</a></span>
</figcaption>
</figure>
<p>The <a href="https://doi.org/10.1080/02640414.2014.977940">mental stress of competition</a>, compounded by the imminent risk of serious injury, can make the heart beat like a jackhammer. Weather can also play a role. This is especially true during the hot days of summer when the heart works harder to regulate driver body temperature. Even the race car contributes: Beyond the hot cabin environment, the car creates vibrations that also <a href="https://doi.org/10.1152/jappl.1966.21.6.1725">stimulate the heart to beat faster</a>.</p>
<p>The race in Chicago will feature all of these challenges, putting extreme stress on drivers. Drivers will be racing closed-cockpit cars wheel-to-wheel through the twists and turns of an unfamiliar street course in the heat of midsummer. These athletes must endure all of these challenges for two hours or longer, while racing 220 miles (354 kilometers) at speeds exceeding 100 mph (161 kph). </p>
<p>While the outcome is unpredictable, the drivers will be pushing their bodies – in addition to their cars – to their limits.</p><img src="https://counter.theconversation.com/content/207189/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Reid receives funding from NASCAR to measure the physiological stresses experienced by race car drivers. NASCAR will have access to these findings, which are expected to be published in a peer-reviewed journal.</span></em></p>Imagine an NBA game played outdoors in August, with no substitutions and players wearing snowsuits, gloves and ski masks. Race car drivers routinely compete under similar conditions.Michael Reid, Professor of Applied Physiology and Kinesiology, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2013802023-06-15T02:07:48Z2023-06-15T02:07:48ZBig hair? Bald? How much difference your hair really makes to keep you cool or warm<figure><img src="https://images.theconversation.com/files/525825/original/file-20230512-21-gwsojg.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1000%2C666&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/close-photo-beautiful-she-her-wear-1776598856">Shutterstock</a></span></figcaption></figure><p>We have <a href="https://theconversation.com/health-check-why-does-womens-hair-thin-out-39126">millions</a> of hair follicles on our body, including around 100,000 on our scalp. </p>
<p>This might sound like a lot of hair, yet humans are described as “hairless”. We have evolved to be the only mammals with a relatively hairless body, but still with scalp hair.</p>
<p>So how does your hair affect your body temperature when it’s hot or cold? </p>
<p>Compared with other animals, our hair does not have as much influence on keeping us warm or cool as you might think. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-why-do-some-people-feel-the-cold-more-than-others-37805">Health Check: why do some people feel the cold more than others?</a>
</strong>
</em>
</p>
<hr>
<h2>Essential to our survival</h2>
<p>Our brain function and body’s metabolism depend on an optimal temperature of around 37°C. Thermoregulation maintains this body temperature, even when we are exposed to a hotter or colder external temperature.</p>
<p>For non-human mammals, body hair or fur plays a role in protecting against environmental cold or heat. </p>
<p>For instance, a heavy fur coat helps keep a polar bear <a href="https://polarbearsinternational.org/polar-bears-changing-arctic/polar-bear-facts/adaptions-characteristics/">warm</a> in the cold. But fur also keeps an animal cool in the heat because it can <a href="https://www.jstor.org/stable/25064866">absorb or reflect</a> radiant heat. </p>
<p>Scientists think this is why humans have kept hair on our heads. Our heads are exposed to the most heat from the sun, and scalp hair keeps our heads cool. </p>
<p>Research published just last week <a href="https://www.pnas.org/doi/10.1073/pnas.2301760120">suggests</a> curly hair provides the best heat protection. That’s because curly hair’s thicker layer of insulation reduces the amount of sun that reaches the scalp.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Four people arm in arm walking along dirt road" src="https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/528515/original/file-20230526-29-hlgs3o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Curly hair may provide the best protection.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/friends-walking-travel-young-people-nature-2212936811">Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-humid-is-it-3-things-to-keep-you-cool-in-a-hot-and-sticky-summer-and-3-things-that-wont-176365">How humid is it? 3 things to keep you cool in a hot and sticky summer (and 3 things that won't)</a>
</strong>
</em>
</p>
<hr>
<h2>But hair is not the only factor</h2>
<p>When humans moved from living in the jungle to the savannah, they needed to walk and run long distances in the sun. This meant they needed a way to handle the increased body temperature that comes with physical activity in the heat. </p>
<p>Sweating is the best way to lose heat and cool down, but the presence of hair reduces sweating and heat loss from the skin.</p>
<p>So humans evolved to <a href="https://www.pnas.org/doi/10.1073/pnas.1113915108">lose body hair</a> to be better adapted to exercising in the heat. Fewer hair follicles in our skin made room for more sweat glands. This made our skin optimal for sweat evaporation – and the <a href="https://theconversation.com/want-to-keep-cool-on-hot-summer-days-heres-how-34489">heat loss</a> that goes with it – to keep us cool.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-art-of-balding-a-brief-history-of-hairless-men-199531">The art of balding: a brief history of hairless men</a>
</strong>
</em>
</p>
<hr>
<h2>So what’s best in the heat?</h2>
<p>You might think removing body hair or having a bald head is best for sweating and keeping cool when exercising in the heat. However, it’s not that simple.</p>
<p>Removing head hair would increase the <a href="https://www.pnas.org/doi/10.1073/pnas.2301760120">amount of sun</a> that reaches your scalp. This means you would need to <a href="https://pubmed.ncbi.nlm.nih.gov/20683812/">sweat more</a> during exercise in the sun to reduce an increase in body temperature, but not by much.</p>
<p>In fact, it’s the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4667044/#:%7E:text=The%20body%20hair%20is%20advantageous,heat%20removal%20during%20heat%20stress.">least hairy</a>
areas of our body that have the highest sweat rates during exercise. These are our forehead, neck, feet and hands.</p>
<p>So the best way to keep cool in the heat is to keep these areas uncovered (but still use sunscreen). Removing body hair will not have a large impact on your overall sweat rate.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Bald man combing head" src="https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525826/original/file-20230512-22-p8iehb.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">Going bald or thinking of shaving your head? It won’t much affect your overall sweat rate.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/nostalgic-man-comb-his-bald-head-180040100">Shutterstock</a></span>
</figcaption>
</figure>
<h2>How about when it’s cold?</h2>
<p>Our body hair and head hair theoretically have a role in keeping us warm, but the effects are minimal.</p>
<p>When we are cold, the muscles of the hair follicles on the body contract to cause the hairs to stand straight. This is an attempt to trap heat close to the body and we see this as goosebumps. However, because our body hair is so thin, this does not have a big effect in keeping us warm.</p>
<p>Our head hair can prevent some heat loss from the head, but again this is limited. </p>
<p>When it’s cold, heat can still be lost through the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4667044/#:%7E:text=The%20body%20hair%20is%20advantageous,heat%20removal%20during%20heat%20stress.">skin of the head</a> regardless of your hairstyle. </p>
<p>The scalp also has only a very thin layer of fat compared to the rest of our skin, so our head has less insulation to protect against the cold. </p>
<p>A warm hat or beanie is the only way to prevent too much heat lost from the head.</p>
<h2>In a nutshell</h2>
<p>Our head and body hair, or lack of it, does have a small role in how you maintain your body temperature. </p>
<p>But overall, your hairstyle does not influence whether you feel warm or cool.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ive-always-wondered-why-did-mammals-go-the-fur-route-rather-than-developing-feathers-103905">I've Always Wondered: why did mammals go the fur route, rather than developing feathers?</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/201380/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Theresa Larkin 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>Keeping warm in winter and cool in summer is down to more than the length of your hair.Theresa Larkin, Associate professor of Medical Sciences, University of WollongongLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1992742023-02-23T13:42:14Z2023-02-23T13:42:14ZAfrica’s first heat officer is based in Freetown – 5 things that should be on her agenda<figure><img src="https://images.theconversation.com/files/511378/original/file-20230221-22-2abbei.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">GettyImages</span></span></figcaption></figure><p>Eugenia Kargbo has an unusual job: she is the city of Freetown’s <a href="https://www.nytimes.com/2023/01/06/world/africa/eugenia-kargbo-chief-heat-officer-africa.html">chief heat officer</a>. Her role in Sierra Leone’s capital is the <a href="https://www.bloomberg.com/news/features/2022-01-21/how-africa-s-first-heat-officer-confronts-climate-change">first of its kind in Africa</a>. She has been tasked with raising public awareness about extreme heat, improving responses to heat waves, and collecting, analysing and visualising heat impact data for the city, which is home to <a href="https://populationstat.com/sierra-leone/freetown">1.2 million people</a>. </p>
<p>Freetown is increasingly threatened by dangerous temperatures. In 2017, the Intergovernmental Panel on Climate Change <a href="https://chinadialogueocean.net/en/governance/19162-sea-level-rise-sierra-leone-sinking-islands/">ranked Sierra Leone third</a>, after Bangladesh and Guinea Bissau, on its list of countries most vulnerable to climate change. </p>
<p>The risks are concentrated in its capital and largest city, Freetown, where some <a href="https://www.mayorsmigrationcouncil.org/gcf-res/freetown-sierra-leone">35%</a> of the population live in 74 informal settlements like Kroo Bay, often in disaster-prone areas like the seafront or hillsides. Houses are densely built and typically temporary structures made of “heat traping” materials. Services that supports cooling, such as water and electricity, are usually inadequate. </p>
<p>As an <a href="https://www.acu.ac.uk/get-involved/commonwealth-climate-research-cohort/theme-cities/dr-olumuyiwa-adegun/">architect</a> whose work includes <a href="https://theconversation.com/growing-plants-on-buildings-can-reduce-heat-and-produce-healthy-food-in-african-cities-191190">researching ways to reduce heat in African cities</a>, I think the creation of an Heat Officer position is a good move. The world’s cities are almost all getting hotter – and, as the Intergovernmental Panel on Climate Change <a href="https://www.ipcc.ch/report/ar6/wg2/">has warned</a>, temperatures will only keep rising. </p>
<p>But, while this is a global challenge, African cities are unique. The significant proportion of urban dwellers who are poor and those whose living conditions do not provide adequate shelter from the elements make the African context unique and deserving special attention. </p>
<p>With these realities in mind, here are five things I’d suggest should be on the agenda of both Kargbo and any other heat officer appointed elsewhere on the continent in future. </p>
<h2>1. Take a diverse approach to urban greening</h2>
<p>Nature-based approaches are a great way to address increasing temperatures linked to climate change. <a href="https://researchoutput.csu.edu.au/en/publications/african-urbanism-the-geography-of-urban-greenery">Scholars have established</a> positive links between green infrastructure, temperature moderation and even health outcomes in African cities as well as elsewhere in the world.</p>
<p>This has informed a growing number of tree-planting initiatives and the development of urban parks. But it is important that municipalities move beyond only these kinds of spaces. African cities are becoming densely populated; that means less space will be available for greening initiatives on land. </p>
<p>Vertical systems of building (for example on walls, roofs, columns) and urban infrastructure (for example on bridges, road furniture) should be explored to make up for the lack of space on the ground.</p>
<p>In the last few years, <a href="https://www.frontiersin.org/articles/10.3389/fbuil.2022.874751/full">I have led the design and development of experimental vertical gardens</a> in low-income areas of Nigeria and Tanzania. <a href="https://academic.oup.com/jue/article/8/1/juac016/6726544">We have shown </a> that these vertical gardens reduce wall temperature of residential buildings by as much as 5°C in Dar es Salaam. The gardens have other benefits like providing fresh vegetables for household consumption. Similar ways of growing vegetation vertically have been seen elsewhere in the world, including in <a href="https://www.theguardian.com/cities/2018/oct/30/mexico-city-via-verde-vertical-gardens-pollution-climate-change">Mexico City</a>.</p>
<h2>2. Strengthen the link between heat and health</h2>
<p>Exposure to extreme heat usually comes with health problems – and can even kill people, <a href="https://www.frontiersin.org/articles/10.3389/fbuil.2022.874751/full">as I</a> and many other scholars <a href="https://pubmed.ncbi.nlm.nih.gov/34846569/">have documented</a>. It exacerbates underlying health conditions. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/heat-stress-is-rising-in-southern-africa-climate-experts-show-where-and-when-its-worst-198455">Heat stress is rising in southern Africa – climate experts show where and when it’s worst</a>
</strong>
</em>
</p>
<hr>
<p>One area of concern when it comes to the heat-health nexus in African countries is that <a href="https://pubmed.ncbi.nlm.nih.gov/32584659/">mosquito numbers increase in higher temperatures</a>. This means malaria and other diseases transmitted by mosquitoes might become <a href="https://www.sciencedirect.com/science/article/pii/S2542519621001327">significant problems</a> for Freetown and other African cities. </p>
<p>These health problems are further complicated by the fact that many city dwellers across the continent <a href="https://academic.oup.com/heapol/article/27/suppl_1/i46/603713">can’t access adequate and affordable health care</a>. Community health initiatives within cities and efforts to ramp up health services in qualitative and quantitative terms must be integral to heat adaptation plans and actions. </p>
<h2>3. Focus on early warning and improved awareness</h2>
<p>It is far better to be proactive than reactive. Heat vulnerability patterns within Freetown and other African cities must be studied and used to make sense of weather predictions in order to inform warning systems. </p>
<p>In the warning systems, for example, an alert level can be triggered when the weather forecast shows three or more consecutive days with daytime maximum temperature and humidity above a threshold of, say, 30°C. Other levels of alerts can correspond with higher temperatures. This sort of system has been <a href="https://www.toronto.ca/community-people/health-wellness-care/health-programs-advice/hot-weather/about-torontos-heat-relief-strategy/">implemented</a> in Toronto, Canada, with good outcomes. <a href="https://link.springer.com/article/10.17269/s41997-022-00665-1">A recent study</a> of urban areas in Ontario (the province where Toronto is located) shows that early warnings may have meant fewer heat-related illnesses severe enough to warrant hospital or clinic visits. </p>
<h2>4. Encourage the transfer of knowledge</h2>
<p>Cities can adapt to heat faster when they share knowledge and experiences. Some scholars <a href="https://en.x-mol.com/paper/article/1481026728131448832">argue</a> that inter-city collaboration and knowledge-sharing can enhance municipalities’ resilience and improve urban residents’ skills to deal with heat-related issues.</p>
<p>Kargbo’s work will generate many lessons that can be shared with other African cities; she, too, will learn from other cities’ successes and failures</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/growing-more-plants-and-trees-can-cut-down-the-heat-in-nigerian-cities-82185">Growing more plants and trees can cut down the heat in Nigerian cities</a>
</strong>
</em>
</p>
<hr>
<p>. </p>
<h2>5. Let locals lead</h2>
<p>While there is plenty to learn from more developed countries outside Africa, it is important to also draw from local indigenous knowledge and practices. An examination of knowledge and awareness about climate-related and environmental problems in African traditional society <a href="https://pubag.nal.usda.gov/catalog/6017059">shows</a> there is much to be learned from indigenous systems.</p>
<p>Top-down approaches are not enough. They must be complemented by bottom-up approaches in the planning, funding, execution and assessment of heat adaptation initiatives. </p>
<p>Inclusion is also important because it shifts power to those who are most affected by heat – people living in low-income and informal areas <a href="https://www.sciencedirect.com/science/article/pii/S2589004221012177">are disproportionately affected</a>. Involving them enhances the impacts of initiatives and interventions.</p><img src="https://counter.theconversation.com/content/199274/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Olumuyiwa Adegun previously received funding from African Academy of Sciences; DAAD ClimapAfrica Program; Commonwealth Futures Climate Research Cohort Programme</span></em></p>Freetown, the capital city of Sierra Leone, has a chief heat officer, the first in Africa. She has her work cut out for her.Olumuyiwa Adegun, Senior Lecturer, Department of Architecture, Federal University of Technology, AkureLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1990852023-02-10T01:50:05Z2023-02-10T01:50:05ZIs my medicine making me feel hotter this summer? 5 reasons why<figure><img src="https://images.theconversation.com/files/508796/original/file-20230208-24-lf74uh.jpg?ixlib=rb-1.1.0&rect=2%2C1%2C995%2C664&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/overheated-woman-sitting-on-couch-waving-1707953323">Shutterstock</a></span></figcaption></figure><p>If you’re really feeling the heat this summer, it might be down to more than the temperature outside.</p>
<p>Some types of medicines can increase your core body temperature or make you feel hotter than you really are. Some can affect your body’s ability to cool down.</p>
<p>Here’s what you need to know about heat intolerance and medicines.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-to-cope-with-extreme-heat-days-without-racking-up-the-aircon-bills-128857">How to cope with extreme heat days without racking up the aircon bills</a>
</strong>
</em>
</p>
<hr>
<h2>What is heat intolerance?</h2>
<p>Some people simply dislike the feeling of feeling hot, while others feel hot at temperatures most people find comfortable. Both are examples of
<a href="https://www.medicalnewstoday.com/articles/325232#symptoms">heat intolerance</a>.</p>
<p>Typical symptoms during warm weather include excessive sweating (or not sweating enough), exhaustion and fatigue, nausea, vomiting or dizziness, and changes in mood.</p>
<p>A number of factors can cause heat intolerance.</p>
<p>This includes the disorder <a href="https://my.clevelandclinic.org/health/diseases/6004-dysautonomia">dysautonomia</a>, which affects people’s autonomic nervous system – the part of the body that regulates the automatic functions of the body, including our response to heat. </p>
<p>Conditions such as diabetes, alcohol misuse, <a href="https://theconversation.com/what-causes-parkinsons-disease-what-we-know-dont-know-and-suspect-57579">Parkinson’s disease</a>, the autoimmune disease <a href="https://theconversation.com/explainer-what-is-guillain-barre-syndrome-and-is-it-caused-by-the-zika-virus-53884">Guillain-Barré syndrome</a> and <a href="https://theconversation.com/explainer-what-are-mitochondria-and-how-did-we-come-to-have-them-83106">mitochondrial disease</a> can cause dysautonomia. People in old age, those with some neurological conditions, or people less physically fit may also have it.</p>
<p>But importantly, medications can also contribute to heat intolerance.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/5-reasons-to-check-on-your-elderly-neighbour-during-a-heatwave-196218">5 reasons to check on your elderly neighbour during a heatwave</a>
</strong>
</em>
</p>
<hr>
<h2>1. Your body temperature rises</h2>
<p>Some medicines directly increase your body temperature, which then increases the risk of heat intolerance. </p>
<p>These include <a href="https://bpspubs.onlinelibrary.wiley.com/doi/epdf/10.1111/bph.15465">stimulant medications</a> to treat ADHD (attention deficit hyperactivity disorder), such as methylphenidate, dexamfetamine and lisdexamfetamine.</p>
<p><a href="https://www.healthdirect.gov.au/antipsychotic-medications">Antipsychotic medications</a> (such as clozapine, olanzapine and quetiapine) used to treat mental health conditions, such as schizophrenia and bipolar disorder, are other examples. </p>
<p>These ADHD and antipsychotic medicines raise your temperature by acting on the hypothalamus, the region of the brain essential for cooling.</p>
<p>The drug levothyroxine, used to treat an under-active thyroid, also increases your body temperature, this time by <a href="https://www.ncbi.nlm.nih.gov/books/NBK500006/">increasing your metabolism</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Medical illustration of hypothalamus region of brain" src="https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508840/original/file-20230208-28-ki6965.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">Some medicines raise your body temperature directly by acting on the hypothalamus region of the brain.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-rendered-medically-accurate-illustration-hypothalamus-1292650669">SciePro/Shutterstock</a></span>
</figcaption>
</figure>
<h2>2. Your blood flow is affected</h2>
<p>Other medicines constrict (tighten) blood vessels, decreasing blood flow to the skin, and so prevent heat from escaping this way. This means your body can’t regulate its temperature as well in the heat. </p>
<p>Examples include <a href="https://www.healthdirect.gov.au/beta-blockers">beta-blockers</a> (such as metoprolol, atenolol and propranolol). These medications are used to treat conditions such as high blood pressure, angina (a type of chest pain), tachycardia (fast heart rate), heart failure, and to prevent migraines. </p>
<p><a href="https://www.nhs.uk/conditions/decongestants/">Decongestants</a> for blocked noses (for example, pseudoephedrine and phenylephrine), triptans for migraines (such as sumatriptan and zolmitriptan) and the ADHD medications mentioned earlier can also act to decrease blood flow to the skin.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/forget-nose-spray-good-sex-clears-a-stuffy-nose-just-as-effectively-and-is-a-lot-more-fun-167901">Forget nose spray, good sex clears a stuffy nose just as effectively — and is a lot more fun</a>
</strong>
</em>
</p>
<hr>
<h2>3. You can get dehydrated</h2>
<p>Other medicines can cause dehydration, which then makes you more susceptible to heat intolerance. The best examples are <a href="https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/diuretics/art-20048129">diuretics</a> such as furosemide, hydrochlorothiazide, acetazolamide and aldosterone.</p>
<p>These are used to control high blood pressure and heart failure by forcing your kidneys to remove more fluid from your body. </p>
<p>Laxatives, such as senna extract and bisacodyl, also remove water from your body and so have a similar effect.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-how-do-i-tell-if-im-dehydrated-107437">Health Check: how do I tell if I'm dehydrated?</a>
</strong>
</em>
</p>
<hr>
<h2>4. You can sweat less</h2>
<p>Other medicines have a drying effect. This can be needed for medicines to do their job (for instance, to dry up a runny nose). For others, it is an unwanted side effect. </p>
<p>This drying reduces the amount you sweat, making it harder to lose heat and regulate your core temperature. A number of medicines have these effects, including:</p>
<ul>
<li>some antihistamines (such as promethazine, doxylamine and diphenhydramine)</li>
<li>certain antidepressants (such as amitriptyline, clomipramine and dothiepin)</li>
<li>medicines used to treat <a href="https://www.healthdirect.gov.au/urinary-incontinence#:%7E:text=Urinary%20incontinence%2C%20or%20poor%20bladder%20control%2C%20is%20very%20common%20in,to%20cure%20or%20improve%20it.">urinary incontinence</a> (for example, oxybutynin and solifenacin) </li>
<li>nausea medicine (prochlorperazine)</li>
<li>medicines for stomach cramps and spasms (for instance, hyoscine) </li>
<li>the antipsychoptics chlorpromazine, olanzapine, quetiapine and clozapine.</li>
</ul>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-do-men-really-sweat-more-than-women-73903">Health Check: do men really sweat more than women?</a>
</strong>
</em>
</p>
<hr>
<h2>5. You don’t feel thirsty</h2>
<p>Finally, some medicines, such as the antipsychotics haloperidol and droperidol, can aggravate heat intolerance by reducing your ability to feel thirsty. </p>
<p>If you don’t feel thirsty, you drink less and are therefore at risk of dehydration and feeling hot.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Woman staring at glass of water on counter" src="https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508849/original/file-20230208-31-oak7ni.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">People taking some medications just don’t feel thirsty.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/upset-young-woman-looking-through-glass-754782025">Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-how-can-extreme-heat-lead-to-death-91480">Health Check: how can extreme heat lead to death?</a>
</strong>
</em>
</p>
<hr>
<h2>What can you do about it?</h2>
<p>If you are feeling hot this summer and think your medicine may be contributing, it’s very important you keep taking your medicine.</p>
<p>Speak to your pharmacist or doctor about your symptoms. They will offer advice and discuss alternatives.</p><img src="https://counter.theconversation.com/content/199085/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Associate Professor Wheate in the past has received funding from the ACT Cancer Council, Tenovus Scotland, Medical Research Scotland, Scottish Crucible, and the Scottish Universities Life Sciences Alliance. He is a Fellow of the Royal Australian Chemical Institute, a member of the Australasian Pharmaceutical Science Association, and a member of the Australian Institute of Company Directors. Nial is the chief scientific officer of Vairea Skincare LLC and a Standards Australia panel member for sunscreen agents.</span></em></p><p class="fine-print"><em><span>Jessica Pace 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>If you think your medicine may be contributing to overheating, it’s very important you keep taking your medicine. Discuss your symptoms with your pharmacist or doctor.Nial Wheate, Associate Professor of the Sydney Pharmacy School, University of SydneyJessica Pace, Associate Lecturer, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1891742022-11-08T14:30:00Z2022-11-08T14:30:00ZBirds evolve different body temperatures in different climates – new study of 53 African species<figure><img src="https://images.theconversation.com/files/481099/original/file-20220825-14-tw4ry1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Red-billed quelea adult breeding male</span> <span class="attribution"><span class="source">Linn Currie/Shutterstock</span></span></figcaption></figure><p>During the northern hemisphere summer of 2022, yet another round of extreme heat waves <a href="https://edition.cnn.com/2022/08/25/europe/record-heat-climate-analysis-summer-2035-intl-scli/index.html">roasted</a> Eurasia, North America and northern Africa – a stark reminder that these conditions are becoming the new normal. </p>
<p>These events can have a devastating impact on wildlife. For instance, reports of large-scale deaths of birds have become regular in recent years, as we’ve seen in <a href="https://link.springer.com/article/10.1007/s00300-021-02982-6">Patagonia</a>, <a href="https://academic.oup.com/condor/article/124/1/duab052/6497508?login=true">Argentina</a> and <a href="https://www.theguardian.com/world/2022/jun/16/spain-heatwave-baby-swifts-die-leaving-nest">Spain</a>.</p>
<p>These events underscore the need to understand the ability of birds (and other animals) to tolerate extreme heat. This information will be essential for predicting where and when future mortality events could occur. It can also tell us which species will be most affected.</p>
<p>Intriguingly, when we conducted a <a href="https://www.pnas.org/doi/10.1073/pnas.2116645119#con1">study</a> to measure how much heat 53 bird species in southern Africa could stand, we found that species vary greatly in the way they handle heat. </p>
<p>Most significantly, how hot a bird’s body temperature could get – what we call “maximum tolerable body temperature” – differed in unexpected ways among bird species from different climatic regions. This suggests that birds from different climates will handle extreme heat differently.</p>
<p>This is an important finding. Previous <a href="https://ia803200.us.archive.org/9/items/biostor-7666/biostor-7666.pdf">research</a> assumed that the body temperature response to extreme air temperatures for birds was similar between species. Predictions on how vulnerable birds are to climate change have been modelled with this thinking in mind. </p>
<p>Our study shows that the reality is more complex. Birds may have evolved depending on where they lived, to have variation in traits like body temperature and their ability to handle heat. </p>
<p>Assuming that birds all handle heat in the same way could result in predictions that don’t reflect how vulnerable they truly are to global warming. To improve the accuracy of such predictions, the body temperature limits of specific species need to be incorporated.</p>
<h2>Body temperature regulation in the heat</h2>
<p>Our <a href="https://www.pnas.org/doi/10.1073/pnas.2116645119#con1">study</a> examined 53 bird species from hot arid, cool mountainous or warm humid coastal regions of southern Africa. </p>
<p>We hypothesised that birds from different climatic areas differed in body temperature responses to extreme air temperatures. We tested this hypothesis by measuring the birds’ body temperature, metabolic rate and evaporative water loss at increasing air temperatures. (Water loss primarily happens when a bird pants, allowing it to cool down.)</p>
<p>We were particularly interested in the birds’ maximum body temperature. We measured this just before birds displayed symptoms such as loss of co-ordination and uncontrolled increases in body temperature. Both of those symptoms are associated with the onset of severe hyperthermia, or overheating. </p>
<p>We found that desert birds comfortably handled air temperatures exceeding 50°C, without a dramatic increase in their body temperature. They maintained body temperatures below approximately 44.5°C.</p>
<p>In contrast, birds from warmer, humid regions tolerated air temperatures in the upper 40s before showing signs of severe hyperthermia. Their body temperatures increased on average by almost six degrees above normal levels of 38-41°C. </p>
<p>Generally, large fluctuations in a bird’s body temperature during extreme heat exposure suggests that the bird isn’t able to maintain (or thermoregulate) optimal body temperatures.</p>
<p>However one species, the red-billed quelea, which occurs across much of sub-Saharan Africa, could cope with a body temperature increase to an astounding 48°C without any ill effect. This was previously thought physiologically impossible among birds. </p>
<h2>Evolution of heat tolerance</h2>
<p>Why did birds evolve tolerance of such high body temperatures? </p>
<p>The answer, we think, is that birds from more humid areas have adapted to rely less on evaporative cooling during hot weather.</p>
<p>Evaporative cooling is when a bird loses heat by panting through its mouth or via other pathways. It is the only way a bird can offload heat when the temperature of its immediate surroundings is higher than its body temperature. So being able to tolerate a high body temperature allows a bird to survive in a humid area, where it can’t lose much heat by panting.</p>
<p>Essentially, birds which have evolved in humid climates survive extremely hot weather by tolerating hyperthermia. In contrast, desert birds use highly efficient evaporative cooling to avoid hyperthermia.</p>
<p>This suggests that being exposed to different climatic conditions has driven the evolution of differences in body temperature and heat tolerance among birds from different climates. </p>
<h2>Protecting birds from heat</h2>
<p>The findings of our study are highly relevant for understanding the risks posed by extreme heat waves to birds and other wildlife. For instance, our findings confirm previous suspicions that songbirds, which make up <a href="https://www.pnas.org/doi/10.1073/pnas.1813206116">over half</a> of all bird species on Earth, are particularly vulnerable to heatwaves.</p>
<p>Developing strategies to mitigate the effects of these events on birds and other wildlife is crucial, as extreme heat events are becoming more regular and widespread across southern Africa. They pose increasing risks to the region’s remarkable biodiversity.</p>
<p>These risks were dramatically illustrated in northern KwaZulu-Natal, South Africa, on 8 November 2020, when air temperatures in the Pongola area soared to 45°C by mid-afternoon. This caused huge numbers of birds to <a href="https://mg.co.za/environment/2021-04-23-south-africa-passes-grim-milestone-after-extreme-heat-kills-off-birds-bats/">succumb</a>. Approximately 90% of the bird carcasses found by field rangers in the nearby Phongolo Nature Reserve in the aftermath of the heat were those of songbirds.</p>
<p>Management interventions in protected areas may reduce the likelihood of future mortality events. Maintaining shady vegetation, for instance, provides cool places where birds can escape the worst of the heat. Free-standing water sources will also increase the likelihood that birds are able to defend body temperatures below lethal limits.</p>
<p>Ultimately, however, the only way to prevent large-scale losses of avian biodiversity – on account of rapid global warming – is the rapid decarbonisation of economies and a global transition to renewable energy sources.</p><img src="https://counter.theconversation.com/content/189174/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marc Trevor Freeman receives funding from National Research Foundation. </span></em></p><p class="fine-print"><em><span>Andrew McKechnie receives funding from the National Research Foundation. He holds the South African Research Chair in Conservation Physiology, hosted by the South African National Biodiversity Institute and co-hosted by the University of Pretoria.</span></em></p>Birds species vary greatly in the way they handle heat – an important finding for predicting vulnerability to global warming.Marc Trevor Freeman, Hot Birds Research Project lab manager and PhD candidate, University of PretoriaAndrew McKechnie, Professor of Zoology and South African Research Chair-holder, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1881222022-08-22T17:16:04Z2022-08-22T17:16:04ZNo longer freezing: Working from home can make workplaces more comfortable<figure><img src="https://images.theconversation.com/files/478985/original/file-20220812-16-iws5c1.jpg?ixlib=rb-1.1.0&rect=17%2C0%2C5734%2C3828&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Thermal discomfort is just another reason employees may prefer to continue teleworking.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/no-longer-freezing--working-from-home-can-make-workplaces-more-comfortable" width="100%" height="400"></iframe>
<p>Working from home during the pandemic presented a wide array of challenges and benefits for those who were able to do so. For some, a benefit was workplace comfort. </p>
<p>While the conversation on gender differences when it comes to thermal comfort in the workplace is not new — men tend to report being more comfortable than women — <a href="https://www.cobee2022.org/assets/doc/COBEE2022_Program_V1.pdf">our research</a> on teleworkers’ behaviours during the pandemic revealed that women were more comfortable in their home offices because they could control the temperature, add or remove layers. </p>
<p>Specifically, our results and <a href="https://doi.org/10.1038/s41598-021-03121-1">previous research</a> suggest that workplaces that do not provide personalized thermostat settings or require any formal attire don’t promote equitable thermal comfort conditions.</p>
<h2>Survey of teleworkers</h2>
<p>Our research team at the <a href="https://carleton.ca/hbilab/">Human Building Interaction Laboratory at Carleton University</a> surveyed teleworkers (many of whom relocated to home offices) during the COVID-19 pandemic by conducting in-depth interviews. </p>
<p>We sought to uncover how teleworking impacted workers’ behaviours at home compared to their behaviours in traditional office spaces. </p>
<p>What we found strongly suggests that teleworkers experienced many benefits, including increased productivity, less mental exhaustion and greater thermal comfort.</p>
<h2>Relaxed formal attire requirements</h2>
<p>Our data indicates that improved thermal comfort at home is because of personal control over the thermostat and greater flexibility over what to wear during the workday. </p>
<p>In <a href="https://www.cobee2022.org/assets/doc/COBEE2022_Program_V1.pdf">our study</a>, most teleworkers’ primary action to stay comfortable was to add or remove clothing layers when they felt too hot or cold, unless they had a child. When teleworkers’ had a child, they kept the thermostat set to a temperature that was comfortable for their children. </p>
<p>“I am more comfortable now [at home] because it’s warmer and the office, it was colder,” said one of our interviewees.</p>
<figure class="align-center ">
<img alt="A thermostat on a wall" src="https://images.theconversation.com/files/478982/original/file-20220812-1219-d55cq3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/478982/original/file-20220812-1219-d55cq3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/478982/original/file-20220812-1219-d55cq3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/478982/original/file-20220812-1219-d55cq3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/478982/original/file-20220812-1219-d55cq3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/478982/original/file-20220812-1219-d55cq3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/478982/original/file-20220812-1219-d55cq3.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">Thermostat settings were originally designed based on men’s formal office attire.</span>
<span class="attribution"><span class="source">(Moja Msanii/Unsplash)</span></span>
</figcaption>
</figure>
<p>In traditional office settings, employees typically cannot control the thermostat or temperature to suit their needs, which can lead to discomfort. </p>
<p>The situation can be even more challenging for women in settings where relatively formal attire is required. This is because office thermostat settings <a href="https://doi.org/10.1038/nclimate2741">were originally designed based on men’s formal office attire</a>. </p>
<p>“I remember feeling cold all the time over there [office] […] definitely, that was something that doesn’t happen anymore because it’s my own home, and I’m comfortable with temperatures here,” said an interviewee.</p>
<p>Teleworking brought more relaxed attire requirements to employees because, well, there often weren’t any. Both men and women during video conferencing said they only wore formal clothes on the portion of their bodies that was visible to others via the camera.</p>
<h2>Equity in the workplace</h2>
<p>While equity in the workplace has many different facets, such as salaries, <a href="https://www.sageglass.com/en/visionary-insights/comfort-workplace-equity-issue">providing comfortable working conditions for all is one of the primary subcategories of workplace equity</a>. </p>
<p>Our results, along with <a href="https://doi.org/10.1038/s41598-021-03121-1">many others</a>, show that this basic tenet of workplace <a href="https://doi.org/10.1038/s41598-021-03121-1">equity is not achieved in many workplaces when it comes to thermal comfort</a>. </p>
<p>There remains a need to take action and improve conditions in traditional workspaces by giving employees more ways to control the temperature and their comfort. Some solutions may be providing them with flexible or less formal clothing options, or coming up with <a href="https://v2.wellcertified.com/en/v/thermal%20comfort">other ways of improving thermal comfort like desk fans, openable windows and chairs with built-in heaters</a>. Perhaps it’s also time to revisit the ideal office thermostat settings. </p>
<p>Thermal discomfort is just another reason employees may prefer to continue teleworking.</p>
<figure class="align-center ">
<img alt="A man buttons his suit in front of a staircase" src="https://images.theconversation.com/files/478987/original/file-20220812-18-ehc0cw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/478987/original/file-20220812-18-ehc0cw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/478987/original/file-20220812-18-ehc0cw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/478987/original/file-20220812-18-ehc0cw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/478987/original/file-20220812-18-ehc0cw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/478987/original/file-20220812-18-ehc0cw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/478987/original/file-20220812-18-ehc0cw.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">Employers should revisit formal dress codes and consider personalized thermostat settings.</span>
<span class="attribution"><span class="source">(Hunters Race/Unsplash)</span></span>
</figcaption>
</figure>
<h2>Workplace attire</h2>
<p>Business researchers Katherine Karl and Joy Peluchette <a href="https://doi.org/10.1002/hrdq.1208">found that workplace attire was linked to</a> productivity, as well as perceived authoritativeness, trustworthiness, friendliness, creativity and competency of employees. In other words, a company’s goals are directly linked to how employees will be required to dress. </p>
<p>For instance, banks might need their employees to convey a sense of trustworthiness and so require their customer-facing employees to wear more formal clothes, whereas organizations in creative fields might allow their employees to choose their attire more freely. </p>
<p>Our research suggests that employers should revisit formal dress codes and consider personalized thermostat settings. By applying such strategies, organizations can move toward improved workplace equity and benefit from <a href="https://www.nytimes.com/2019/05/22/health/women-temperature-tests.html">increased productivity and performance</a>.</p><img src="https://counter.theconversation.com/content/188122/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Employers can foster equity in the workplace by relaxing current dress codes or providing employees with individual thermostat control and other means to improve their comfort.Farzam Sepanta, PhD Candidate, Building Engineering, Carleton UniversityLaura Arpan, Theodore Clevenger Professor of Communication, FAMU-FSU College of EngineeringLiam O'Brien, Professor in Architectural Conservation and Sustainability Engineering, Carleton UniversityMarianne Touchie, Associate Professor, Department of Civil and Mineral Engineering, University of TorontoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1886942022-08-22T12:26:39Z2022-08-22T12:26:39ZDoes turning the air conditioning off when you’re not home actually save energy? Three engineers run the numbers<figure><img src="https://images.theconversation.com/files/479979/original/file-20220818-164-78ogjl.jpg?ixlib=rb-1.1.0&rect=125%2C440%2C4534%2C3054&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Is it better to cool your house all day, or adjust the A/C setting on your way out the door?</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/father-carrying-son-on-shoulders-adjusting-royalty-free-image/668763443">Westend61 via Getty Images</a></span></figcaption></figure><p>Hot summer days can mean high electricity bills. People want to stay comfortable without wasting energy and money. Maybe your household has fought over the best strategy for cooling your space. Which is more efficient: running the air conditioning all summer long without break, or turning it off during the day when you’re not there to enjoy it? </p>
<p>We are a <a href="https://scholar.google.com/citations?user=dXCbQqMAAAAJ&hl=en&oi=ao">team of architectural</a> <a href="https://scholar.google.com/citations?user=TAOTdN4AAAAJ&hl=en&oi=ao">and building systems</a> <a href="https://scholar.google.com/citations?user=AdHh9wwAAAAJ&hl=en">engineers</a> who used energy models that simulate heat transfer and A/C system performance to tackle this perennial question: Will you need to remove more heat from your home by continuously removing heat throughout the day or removing excess heat only at the end of the day?</p>
<p>The answer boils down to how energy intensive it is to remove heat from your home. It’s influenced by many factors such as how well your house is insulated, the size and type of your air conditioner and outdoor temperature and humidity. </p>
<p>According to our unpublished calculations, letting your home heat up while you’re out at work and cooling it when you get home can use less energy than keeping it consistently cool – but it depends.</p>
<h2>Blast A/C all day, even when you’re away?</h2>
<p>First, think about how heat accumulates in the first place. It flows into your home when the building has less stored heat than outside. If the amount of heat flowing into your home is given by a rate of “1 unit per hour,” your A/C will always have 1 unit of heat to remove every hour. If you turn off your A/C and let the heat accumulate, you could have up to eight hours’ worth of heat at the end of the day.</p>
<p>It’s often less than that, though – homes have a limit to how much heat they can store. And the amount of heat that enters your home depends on how hot the building was to begin with. For example, if your home can only store 5 units of thermal energy before coming to an equilibrium with the outdoor air temperature, then at the end of the day you will only ever have to remove 5 units of heat at most.</p>
<p>Additionally, as your home heats up, the process of heat transfer slows down; eventually it reaches zero heat transfer at equilibrium, when the temperature inside is the same as the temperature outside. Your A/C also cools less effectively in extreme heat, so keeping it off during the hottest parts of the day can increase overall efficiency of the system. These effects mean there’s no one straightforward answer to whether you should blast the A/C all day or wait until you get back home in the evening.</p>
<h2>Energy used by different A/C strategies</h2>
<p>Consider a test case of a small home with typical insulation in two warm climates: dry (Arizona) and humid (Georgia). Using <a href="https://www.nrel.gov/buildings/beopt.html">energy modeling software</a> created by the U.S. National Renewable Energy Laboratory for analyzing energy use in residential buildings, we looked at multiple test cases for energy use in this hypothetical 1,200 square-foot (110 square-meter) home.</p>
<p>We considered three temperature strategy scenarios. One has the indoor temperature set to a constant 76 degrees Fahrenheit (24.4 degrees Celsius). A second lets the temperature float up to 89 F (31.6 C) during an eight-hour workday – a “setback.” The last uses a temperature setback to 89 F (31.6 C) for a short four-hour workday. </p>
<p>Within these three scenarios, we looked at three different A/C technologies: a single stage <a href="https://www.energy.gov/energysaver/central-air-conditioning">central A/C</a>, a <a href="https://www.energy.gov/energysaver/air-source-heat-pumps">central air source heat pump (ASHP)</a> and <a href="https://www.energy.gov/energysaver/ductless-mini-split-heat-pumps">minisplit heat pump units</a>. Central A/C units are typical of current residential buildings, while heat pumps are gaining popularity due to their improved efficiency. Central ASHPs are easily used in one-to-one replacements of central A/C units; minisplits are more efficient than central A/C but costly to set up.</p>
<p>We wanted to see how energy use from A/C varied across these cases. We knew that regardless of the HVAC technology used, the A/C system would surge when the thermostat setpoint returned to 76 F (24.4 C) and also for all three cases in the late afternoon when outdoor air temperatures are usually the highest. In the setback cases, we programmed the A/C to start cooling the space before the resident is back, ensuring thermal comfort by the time they get home.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/479976/original/file-20220818-27-qstjim.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Six line graphs that show how the temperature in the house and the energy used vary with the outdoor heat." src="https://images.theconversation.com/files/479976/original/file-20220818-27-qstjim.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479976/original/file-20220818-27-qstjim.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=472&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479976/original/file-20220818-27-qstjim.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=472&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479976/original/file-20220818-27-qstjim.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=472&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479976/original/file-20220818-27-qstjim.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=593&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479976/original/file-20220818-27-qstjim.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=593&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479976/original/file-20220818-27-qstjim.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=593&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Energy models can show how much energy a house will use under particular conditions – like Phoenix’s hot, dry summer weather. The researchers ran the numbers on three different HVAC technologies and three different temperature-setting strategies.</span>
<span class="attribution"><span class="source">Pigott/Scheib/Baker/CU Boulder</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/479978/original/file-20220818-10466-krvwf2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Six line graphs that show how the temperature in the house and the energy used vary with the outdoor heat." src="https://images.theconversation.com/files/479978/original/file-20220818-10466-krvwf2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479978/original/file-20220818-10466-krvwf2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=472&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479978/original/file-20220818-10466-krvwf2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=472&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479978/original/file-20220818-10466-krvwf2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=472&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479978/original/file-20220818-10466-krvwf2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=593&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479978/original/file-20220818-10466-krvwf2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=593&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479978/original/file-20220818-10466-krvwf2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=593&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 researchers used the same three different HVAC technologies and three temperature-setting strategies, but this time for a house in hot and humid Atlanta.</span>
<span class="attribution"><span class="source">Pigott/Scheib/Baker/CU Boulder</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>What we found was that even when the A/C temporarily spikes to recover from the higher indoor temperatures, the overall energy consumption in the setback cases is still less than when maintaining a constant temperature throughout the day. On an annual scale with a conventional central A/C, this could result in energy savings of up to 11%.</p>
<p>However, the energy savings may decrease if the home is better insulated, the A/C is more efficient or the climate has less dramatic temperature swings.</p>
<p><iframe id="tM9v0" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/tM9v0/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p><iframe id="Wppk7" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/Wppk7/7/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>The central air source heat pump and minisplit heat pump are more efficient overall but yield less savings from temperature setbacks. An eight-hour setback on weekdays provides savings regardless of the system type, while the benefits gleaned from a four-hour setback are less straightforward.</p><img src="https://counter.theconversation.com/content/188694/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Aisling Pigott receives funding from the Department of Energy. </span></em></p><p class="fine-print"><em><span>Jennifer Scheib receives funding from the Department of Energy. </span></em></p><p class="fine-print"><em><span>Kyri Baker receives funding from the Department of Energy, the Alfred P. Sloan Foundation, and the National Science Foundation.</span></em></p>Energy modeling software provides insight into whether letting your A/C relax while you’re gone all day will save you energy – and money.Aisling Pigott, Ph.D. Student in Architectural Engineering, University of Colorado BoulderJennifer Scheib, Assistant Teaching Professor of Building Systems Engineering, University of Colorado BoulderKyri Baker, Assistant Professor of Building Systems Engineering, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1876682022-08-02T12:58:13Z2022-08-02T12:58:13ZHot and getting hotter – 5 essential reads on high temps and human bodies<figure><img src="https://images.theconversation.com/files/476758/original/file-20220729-13732-9ef431.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5419%2C3585&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The way heat and humidity affect people depends on factors like the weather that's typical where they are.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/boy-pouring-water-over-head-outdoors-royalty-free-image/56323439">Hans Huber/Westend61 via Getty Images</a></span></figcaption></figure><p>Launching the <a href="https://cpo.noaa.gov/Interagency-Programs/NIHHIS/About-NIHHIS#:%7E:text=NIHHIS%20is%20an%20integrated%20system,capacity%2C%20communication%2C%20and%20societal%20understanding">National Integrated Heat Health Information System (NIHHIS)</a> and the <a href="https://www.heat.gov/">heat.gov</a> site on July 26, 2022, the Biden administration cited heat waves and the warming climate as serious health threats. As the new initiative promises a “science informed response” to hotter conditions, five stories from The Conversation’s archive explain what researchers know about heat and health.</p>
<h2>1. It’s the humidity</h2>
<p><a href="https://theconversation.com/how-dangerous-heat-waves-can-kill-121727">Heat waves can be deadly</a> in a variety of ways, wrote <a href="https://scholar.google.com/citations?user=fNSdMfEAAAAJ&hl=en&oi=ao">William Calvin</a>, who teaches physiology and neuroscience at the University of Washington.</p>
<p>“Heat waves can kill via the dehydration caused by heavy sweating; the altered sodium and potassium concentrations in the blood confuse both heart and nerve cells, and so breathing or heartbeat may suddenly stop,” he wrote.</p>
<p>Calvin explained that human bodies have not evolved to handle extreme heat with humidity. “Normally, sweat evaporates off your skin and you cool down. But with high humidity, the air is already saturated with water vapor, and so evaporative cooling stops. However, you keep sweating anyway, threatening dehydration.”</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-dangerous-heat-waves-can-kill-121727">How dangerous heat waves can kill</a>
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</em>
</p>
<hr>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/476609/original/file-20220728-25-30dl7d.jpg?ixlib=rb-1.1.0&rect=0%2C29%2C4946%2C3578&q=45&auto=format&w=1000&fit=clip"><img alt="Photo shows roughly half of a furrowed, fair-skinned forehead with dark hair at the temple and many drops of sweat on the skin." src="https://images.theconversation.com/files/476609/original/file-20220728-25-30dl7d.jpg?ixlib=rb-1.1.0&rect=0%2C29%2C4946%2C3578&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/476609/original/file-20220728-25-30dl7d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=437&fit=crop&dpr=1 600w, https://images.theconversation.com/files/476609/original/file-20220728-25-30dl7d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=437&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/476609/original/file-20220728-25-30dl7d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=437&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/476609/original/file-20220728-25-30dl7d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=550&fit=crop&dpr=1 754w, https://images.theconversation.com/files/476609/original/file-20220728-25-30dl7d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=550&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/476609/original/file-20220728-25-30dl7d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=550&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sweating is one way the body stays cool. In heat stroke, sweating stops, leaving the body in danger of fatally overheating.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-mans-wrinkled-forehead-royalty-free-image/200390293-001">Veronique Beranger/The Image Bank via Getty Images</a></span>
</figcaption>
</figure>
<h2>2. Lower tolerance for higher temps</h2>
<p>“That combination of temperature and humidity whereby the person’s core temperature starts to rise is called the ‘critical environmental limit,’” wrote a group of Penn State University scholars researching the health effects of heat: <a href="https://scholar.google.com/citations?hl=en&user=zsXN72cAAAAJ">W. Larry Kenney</a>, <a href="https://scholar.google.com/citations?hl=en&user=xuBw4jQAAAAJ">Daniel Vecellio</a>, <a href="https://scholar.google.com/citations?hl=en&user=KIiHyBgAAAAJ">Rachel Cottle</a> and <a href="https://scholar.google.com/citations?hl=en&user=h05wc-kAAAAJ">S. Tony Wolf</a>.</p>
<p>In a rare lab test of the human body’s heat tolerance, the researchers found that the <a href="https://theconversation.com/how-hot-is-too-hot-for-the-human-body-our-lab-found-heat-humidity-gets-dangerous-faster-than-many-people-realize-185593">limit is lower than previously thought</a>. When the air temperature is around 100 degrees Fahrenheit (38 Celsius), people can begin to feel ill effects at just 60% humidity – a higher temperature and lower humidity than researchers determined in 2010.</p>
<p>“Above those limits, core temperature rises continuously and risk of heat-related illnesses with prolonged exposures is increased,” they wrote. “The results of these tests show an even greater cause for concern.”</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-hot-is-too-hot-for-the-human-body-our-lab-found-heat-humidity-gets-dangerous-faster-than-many-people-realize-185593">How hot is too hot for the human body? Our lab found heat + humidity gets dangerous faster than many people realize</a>
</strong>
</em>
</p>
<hr>
<h2>3. Age matters</h2>
<p>Extremely hot whether is particularly dangerous for those over 70, according to family physician <a href="https://scholar.google.com/citations?user=6YGkTgMAAAAJ&hl=en&oi=ao">Dr. Gabriel Neal</a>, who teaches at the Texas A&M Health Science Center College of Medicine. </p>
<p>In his article on <a href="https://theconversation.com/heat-stroke-a-doctor-offers-tips-to-stay-safe-as-temperatures-soar-120626">avoiding heat stroke</a>, Neal described factors making older adults vulnerable to heat-related illnesses. </p>
<p>“As people age, our bodies’ ability to cool declines, and the elderly often take medication that further impairs this ability,” Neal wrote. “In addition, the elderly may not be aware of the dangerous heat wave and may not have working air conditioning in their home, nor have anyone to check on them.” </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/heat-stroke-a-doctor-offers-tips-to-stay-safe-as-temperatures-soar-120626">Heat stroke: A doctor offers tips to stay safe as temperatures soar</a>
</strong>
</em>
</p>
<hr>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/476604/original/file-20220728-26986-kw8qzx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Four clear glasses of water with ice floating in them sitting on a wooden surface" src="https://images.theconversation.com/files/476604/original/file-20220728-26986-kw8qzx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/476604/original/file-20220728-26986-kw8qzx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/476604/original/file-20220728-26986-kw8qzx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/476604/original/file-20220728-26986-kw8qzx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/476604/original/file-20220728-26986-kw8qzx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/476604/original/file-20220728-26986-kw8qzx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/476604/original/file-20220728-26986-kw8qzx.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">Hydration is key to staying well in the heat.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/drinking-glasses-on-wooden-table-royalty-free-image/558302225">Nawarit Rittiyotee/ EyeEm via Getty Images</a></span>
</figcaption>
</figure>
<h2>4. Wet or dry, hot is hot</h2>
<p><a href="https://theconversation.com/knowing-how-heat-and-humidity-affect-your-body-can-help-you-stay-safe-during-heat-waves-163700">It’s the heat and the humidity</a>, wrote Mississippi State University exercise physiologist <a href="https://theconversation.com/profiles/johneric-w-smith-644514">JohnEric Smith</a>.</p>
<p>“Hot desert climates are stressful due to extreme temperatures, while humid subtropical climates are stressful because the body has trouble removing heat when sweat doesn’t evaporate readily,” he wrote.</p>
<p>Smith added that how heat and humidity affect people depends on factors like the weather that’s typical where they are, and the cooling systems in local homes and buildings.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/knowing-how-heat-and-humidity-affect-your-body-can-help-you-stay-safe-during-heat-waves-163700">Knowing how heat and humidity affect your body can help you stay safe during heat waves</a>
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</em>
</p>
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<h2>5. Warming up food</h2>
<p>Tufts University epidemiologist <a href="https://scholar.google.com/citations?hl=en&user=TeQarhcAAAAJ">Elena Naumova</a> warns that keeping food safe to eat is becoming <a href="https://theconversation.com/climate-change-is-putting-food-safety-at-risk-more-often-a%5B%E2%80%A6%5D-picnics-and-parties-blackouts-are-a-growing-problem-185685">more challenging in a warming climate</a>.
“That’s because warm, wet weather conditions stimulate bacterial growth,” she wrote.</p>
<p>Naumova named several climate-related factors in spreading foodborne illnesses. “One growing problem is that heat waves, wildfires and severe storms are increasingly triggering power outages, which in turn affect food storage and food handling practices in stores, production and distribution sites and homes,” she wrote.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-is-putting-food-safety-at-risk-more-often-and-not-just-at-picnics-and-parties-blackouts-are-a-growing-problem-185685">Climate change is putting food safety at risk more often, and not just at picnics and parties – blackouts are a growing problem</a>
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</em>
</p>
<hr>
<p><em>Editor’s note: This story is a roundup of articles from The Conversation’s archives.</em></p><img src="https://counter.theconversation.com/content/187668/count.gif" alt="The Conversation" width="1" height="1" />
After the announcement of President Biden’s heat initiative, The Conversation revisits stories on high summer temperatures and human health.Leah Samuel, Health + Equity EditorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1879512022-07-29T15:23:32Z2022-07-29T15:23:32ZClimate change is intensifying the water cycle, bringing more powerful storms and flooding – here’s what the science shows<figure><img src="https://images.theconversation.com/files/476720/original/file-20220729-5473-5b7s35.jpg?ixlib=rb-1.1.0&rect=0%2C106%2C3284%2C2137&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">At least 9 inches of rain across eastern Kentucky became floodwater that swept through neighborhoods in July 2022.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/aerial-view-of-homes-submerged-under-flood-waters-from-the-news-photo/1242170051">Leandro Lozada/AFP via Getty Images</a></span></figcaption></figure><p>Powerful storm systems triggered flash flooding across the U.S. in late July, killing <a href="https://twitter.com/GovAndyBeshear/status/1554221064506544131">more than three dozen people</a> in eastern Kentucky as floodwater engulfed homes and set off mudslides. Record rainfall also inundated <a href="https://www.stltoday.com/news/local/metro/cleanup-begins-in-waterlogged-st-louis-region-as-rain-persists/article_32985632-7ec4-5fd4-9dcb-bc87e32c9fb3.html">St. Louis neighborhoods</a>, and another <a href="https://twitter.com/mickakers/status/1552881732348628992">deluge in Nevada flooded the</a> <a href="https://www.reviewjournal.com/local/weather/downtown-las-vegas-sees-flooding-in-late-night-july-storm-2614211/">Las Vegas strip</a>.</p>
<p>The impact of climate change on extreme water-related events like this is becoming increasingly evident. The storms in the U.S. followed extreme flooding this summer in <a href="https://www.cnn.com/2022/06/22/india/bangladesh-india-floods-death-toll-intl-hnk/index.html">India</a> and <a href="https://www.bbc.com/news/world-australia-61991112">Australia</a> and last year in <a href="https://www.science.org/content/article/europe-s-deadly-floods-leave-scientists-stunned">Western Europe</a>.</p>
<p>Studies by scientists around the world show that the water cycle has been intensifying and will continue to intensify as the planet warms. An <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">international climate assessment</a> I coauthored in 2021 for the Intergovernmental Panel on Climate Change lays out the details.</p>
<p>It documented an increase in both wet extremes, including more intense rainfall over most regions, and dry extremes, including drying in the Mediterranean, southwestern Australia, southwestern South America, South Africa and western North America. It also shows that both wet and dry extremes will continue to increase with future warming.</p>
<h2>Why is the water cycle intensifying?</h2>
<p>Water cycles through the environment, moving between the atmosphere, ocean, land and reservoirs of frozen water. It might fall as rain or snow, seep into the ground, run into a waterway, join the ocean, freeze or evaporate back into the atmosphere. Plants also take up water from the ground and <a href="https://www.usgs.gov/special-topics/water-science-school/science/evapotranspiration-and-water-cycle">release it through transpiration</a> from their leaves. In recent decades, there has been an overall increase in the rates of precipitation and evaporation.</p>
<p>A number of factors are intensifying the water cycle, but one of the most important is that warming temperatures raise the upper limit on the amount of moisture in the air. That increases the potential for more rain.</p>
<p><iframe id="GynkN" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/GynkN/8/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>This aspect of climate change is confirmed across <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">all of our lines of evidence</a> discussed in the IPCC report. It is expected from basic physics, projected by computer models, and it already shows up in the observational data as a general increase of rainfall intensity with warming temperatures.</p>
<p>Understanding this and other changes in the water cycle is important for more than preparing for disasters. Water is an essential resource for all ecosystems and human societies, and particularly agriculture.</p>
<h2>What does this mean for the future?</h2>
<p>An intensifying water cycle means that both wet and dry extremes and the general variability of the water cycle will increase, although not uniformly around the globe.</p>
<p>Rainfall intensity is <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">expected to increase for most land areas</a>, but the largest increases in dryness are expected in the Mediterranean, southwestern South America and western North America.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Maps showing precipitation projections and warming projections at 1.5 and 3 degrees Celsius." src="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415093/original/file-20210808-21-ifu4n0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Annual average precipitation is projected to increase in many areas as the planet warms, particularly in the higher latitudes.</span>
<span class="attribution"><a class="source" href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">IPCC Sixth Assessment Report</a></span>
</figcaption>
</figure>
<p>Globally, daily extreme precipitation events will likely intensify by about <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">7% for every 1 degree Celsius</a> (1.8 degrees Fahrenheit) that global temperatures rise.</p>
<p>Many other important aspects of the water cycle will also change in addition to extremes as global temperatures increase, the report shows, including reductions in mountain glaciers, decreasing duration of seasonal snow cover, earlier snowmelt and contrasting changes in monsoon rains across different regions, which will impact the water resources of billions of people.</p>
<h2>What can be done?</h2>
<p>One common theme across these aspects of the water cycle is that <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">higher greenhouse gas emissions lead to bigger impacts</a>.</p>
<p>The IPCC does not make policy recommendations. Instead, it provides the scientific information needed to carefully evaluate policy choices. The results show what the implications of different choices are likely to be.</p>
<p>One thing the <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">scientific evidence in the report</a> clearly tells world leaders is that limiting global warming to the Paris Agreement target of 1.5 C (2.7 F) will require immediate, rapid and large-scale reductions in greenhouse gas emissions.</p>
<p>Regardless of any specific target, it is clear that the severity of climate change impacts are closely linked to greenhouse gas emissions: Reducing emissions will reduce impacts. Every fraction of a degree matters.</p>
<p><em>This article was updated Aug. 1, 2022, with the Kentucky death toll rising.</em></p><img src="https://counter.theconversation.com/content/187951/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mathew Barlow received travel funding from the US government to attend three IPCC lead author meetings.</span></em></p>Extreme downpours caught people off guard from Las Vegas to Kentucky in July 2022.Mathew Barlow, Professor of Climate Science, UMass LowellLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1869582022-07-15T15:46:17Z2022-07-15T15:46:17ZToo hot to sleep? Nights are warming faster than days as Earth heats up<p>Sleeping at the height of summer can sometimes feel impossible. And with gruelling heatwaves <a href="https://www.theccc.org.uk/2018/07/24/climate-change-means-more-action-is-needed-to-address-risk-of-uk-heatwaves-and-water-shortages/">becoming more common</a>, the nights can be sweltering, with no cooling breeze to relieve the discomfort. At least you can trust your senses – nights really are getting hotter. </p>
<p>Weather stations usually record the day’s minimum temperature at or a little after dawn. At a few sites in the UK, records extend back 150 years or more. Allowing for minor changes in instruments and methods over the years, scientists have found that night-time temperatures have risen considerably since Victorian times. In most of the records examined, night-time temperatures are actually rising at a faster rate than daytime temperatures. Why is this?</p>
<p>Recent milder winters in the UK have had fewer very cold nights. The coldest nights tend to be colder relative to the norm than the coldest winter days. Their loss has pushed up the average night-time minimum temperature disproportionately faster than the average daytime maximum temperature.</p>
<figure class="align-center ">
<img alt="A woman sits on a bed in front of an electrical fan." src="https://images.theconversation.com/files/474303/original/file-20220715-16-v47a7m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/474303/original/file-20220715-16-v47a7m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474303/original/file-20220715-16-v47a7m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474303/original/file-20220715-16-v47a7m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474303/original/file-20220715-16-v47a7m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=491&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474303/original/file-20220715-16-v47a7m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=491&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474303/original/file-20220715-16-v47a7m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=491&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A good night’s sleep can be especially elusive if you live in a city.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/exhausted-woman-suffering-suring-heatwave-she-1798696621">Stokkete/Shutterstock</a></span>
</figcaption>
</figure>
<p>UK summers are also seeing more frequent hot weather as a result of climate change. Extreme daytime and night-time temperatures in the UK during heatwaves have risen by a similar amount, about 2°C in 150 years. </p>
<p>But even a brief hot spell allows warm nights to persist after daytime temperatures have returned closer to the norm, particularly in cities, leading to more hot nights than days overall. That’s because concrete and asphalt absorb and release daytime heat more slowly overnight compared with outlying rural areas, resulting in even higher night-time temperatures for city dwellers. This is known as the urban heat island effect.</p>
<p>There are even suggestions that condensation trails left by aircraft have boosted night-time temperatures by reducing how much heat can escape the surface layers of the atmosphere to space, although the <a href="https://e360.yale.edu/features/how-airplane-contrails-are-helping-make-the-planet-warmer#:%7E:text=Red%2Deye%20flights%20are%20a,differences%20by%203%20degrees%20C">evidence is somewhat mixed</a>.</p>
<h2>Warm nights double in 50 years</h2>
<p>Records from two of the longest-running weather stations in the UK, <a href="https://www.geog.ox.ac.uk/research/climate/rms/">the Radcliffe Observatory</a> in Oxford (where records go back to 1814) and <a href="https://durhamweather.webspace.durham.ac.uk/">the Durham University Observatory</a> (which opened in 1841), reveal a lot about how night-time temperatures have changed. </p>
<p>Between 1911 and 1920, the warmest night of the year averaged 16.6°C at Oxford. The average over the last ten years was 18.8°C, a rise of more than 2°C. Warm nights – those in which temperatures remain above 15°C – now average 20 per year in Oxford, more than twice the norm as recently as the 1970s, despite two hot summers in that decade (1975 and <a href="https://theconversation.com/what-was-hot-before-1976-a-trip-down-british-weathers-memory-lane-99899">the notorious 1976</a>). Central London has probably twice as many warm nights in a year as Oxford.</p>
<p>Since 1814, and at the time of writing, only ten nights have remained above 20°C at Oxford (so-called tropical nights). Half of those have occurred within just the last 25 years, including the highest of all: 21.2°C, in July 2016. Even this might well be surpassed soon. Oxford’s urban area has grown since 1814, of course, but the weather station site has changed little since the 1830s, and the increase in mean temperature owing to the urban heat island effect is probably <a href="https://oxford.universitypressscholarship.com/view/10.1093/oso/9780198834632.001.0001/oso-9780198834632-chapter-3">only about 0.2°C</a> since record keeping began.</p>
<p>Compared with the east and south-east of England, heatwaves are shorter and less intense in the north and north-east of England, and hot nights are less frequent as a result. Records from the Durham University Observatory confirm that nights hotter than 15°C are much less likely in north-east England, averaging only six or seven a year over the last decade, or one-third of Oxford’s frequency. But even here, the number of warm nights has increased fourfold since the 1970s. The warmest night of the year in Durham has risen from an average of 14.6°C a century ago to 16.9°C in the most recent ten-year period, a 2°C rise – very similar to Oxford.</p>
<figure class="align-center ">
<img alt="A white box on stilts with a tube protruding from the roof." src="https://images.theconversation.com/files/474356/original/file-20220715-16-m5tskb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/474356/original/file-20220715-16-m5tskb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=421&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474356/original/file-20220715-16-m5tskb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=421&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474356/original/file-20220715-16-m5tskb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=421&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474356/original/file-20220715-16-m5tskb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=529&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474356/original/file-20220715-16-m5tskb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=529&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474356/original/file-20220715-16-m5tskb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=529&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A weather station at the Durham University Observatory.</span>
<span class="attribution"><span class="source">Stephen Burt</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Fortunately, nights above 20°C are as yet unknown in the long Durham record, but the hottest night (18.4°C), recorded there on July 12 2022, was only half a degree Celsius below the all-time record: 18.9°C, also set in July 2016. That may also be surpassed in the very near future. Also, on July 12, 2022, Sheffield’s night-time minimum temperature reached 20.5°C, its highest in 140 years of record keeping. </p>
<p>Even in the Republic of Ireland, famed for its equable climate, a hot spell in July 2021 resulted in the first tropical night for 20 years, when the minimum temperature at <a href="https://www.met.ie/weather-forecast/valentia-weather-station-kerry">Valentia Observatory</a> in the far south-west of Kerry hovered around 20.5°C. Such warm nights are very rare in Ireland – only six previous occurrences are known.</p>
<p>Heatwaves are getting more frequent and more intense, particularly in the south and east of England. <a href="https://www.nature.com/articles/s41467-020-16834-0">An analysis</a> by the Met Office suggested that temperatures of 40°C, more than a degree above the current UK national record (38.7°C, set in Cambridge in July 2019) are likely to occur every few years by 2100.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-40-c-summer-temperatures-could-be-common-in-uk-by-2100-141479">Climate change: 40°C summer temperatures could be common in UK by 2100</a>
</strong>
</em>
</p>
<hr>
<p>As daytime extremes continue to rise, night-time temperatures will also creep up. The highest minimum temperature (hottest night) on record for the UK currently stands at 23.9°C, at Brighton, East Sussex, during the August 1990 heatwave. There are a handful of other locations, including central London, where 23°C has also been recorded overnight. </p>
<p>By the turn of the century, and possibly well before then, without very large reductions in fossil fuel burning, night-time temperatures will not fall below 25°C in some places during hot weather. At present, a daytime temperature of 25°C is the definition of a hot <em>day</em>. We must cut carbon emissions – or future summers will be long, hot and sleepless.</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/186958/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephen Burt 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 strongest signal of our changing climate flares while most of us are asleep.Stephen Burt, Visiting Fellow in Meteorology, University of ReadingLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1763652022-02-16T01:09:01Z2022-02-16T01:09:01ZHow humid is it? 3 things to keep you cool in a hot and sticky summer (and 3 things that won’t)<figure><img src="https://images.theconversation.com/files/445592/original/file-20220210-24693-kz2jtl.jpg?ixlib=rb-1.1.0&rect=1%2C0%2C997%2C663&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/portrait-woman-front-fan-suffering-heat-1745759825">Shutterstock</a></span></figcaption></figure><p><a href="http://www.bom.gov.au/climate/updates/articles/a020.shtml">La Niña</a> has resulted in <a href="https://www.smh.com.au/environment/weather/sydney-smashes-january-humidity-records-as-la-nina-nears-its-peak-20220118-p59p3m.html">a humid summer</a> for much of eastern Australia.</p>
<p>This climate pattern typically causes warm, humid air to rise from the western Pacific Ocean, ultimately leading to greater cloud formation, increased rainfall, and higher humidity along Australia’s eastern seaboard and tropical north.</p>
<p>So what’s the best way to cope with what’s left of a hot and humid La Niña summer?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/back-so-soon-la-nina-heres-why-were-copping-two-soggy-summers-in-a-row-173684">Back so soon, La Niña? Here's why we're copping two soggy summers in a row</a>
</strong>
</em>
</p>
<hr>
<h2>In praise of sweat (and evaporation)</h2>
<p>Sweating (and the heat loss that goes with it) is by far the most effective way our bodies use to cool us down. But it’s not sweating <em>alone</em> that does the trick. It’s the evaporation of sweat that is key.</p>
<p>For every gram of sweat you evaporate, a little over <a href="https://journals.physiology.org/doi/abs/10.1152/jappl.1972.32.4.456">2.4 kilojoules</a> of heat energy is taken with it.</p>
<p>That’s a bit difficult to visualise. So let’s think of it in terms of boiling water.</p>
<p>Evaporating roughly 140 grams of sweat results in enough energy (heat) “loss” to bring a litre of 20°C water to boiling point (at sea level).</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1487831263931088897"}"></div></p>
<p>We were treated to some interesting facts during this year’s notoriously sweaty Australian Open tennis tournament.</p>
<p>Champion player Rafael Nadal was reported to have evaporated <a href="https://www.theguardian.com/sport/2022/jan/28/tug-tuck-wipe-repeat-nadals-rituals-help-defy-his-breaking-body">over 4 kilograms of sweat</a> during his <a href="https://ausopen.com/match/2022-denis-shapovalov-vs-rafael-nadal-ms502">4 hour 8 minute quarter-final win</a> over Denis Shapovalov.</p>
<p>That’s the equivalent of brewing a 250 millilitre cup of tea via the energy of his own sweat-liberated-heat – every 2.2 minutes of the match.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-how-to-exercise-safely-in-the-heat-37286">Health Check: how to exercise safely in the heat</a>
</strong>
</em>
</p>
<hr>
<h2>So how is this all related to humidity?</h2>
<p>Sweat evaporation is dictated primarily by the wetness of the skin, and the absolute humidity of the air. <a href="https://www.weather.gov/lmk/humidity">Absolute humidity</a> is a function of the amount of water vapour in the air. </p>
<p>This is not to be confused with <a href="http://www.bom.gov.au/watl/humidity/">relative humidity</a> which is the term usually used in weather reports. This tells us how much water vapour the air is holding (as a percentage) relative to how much it could possibly hold, which goes up with temperature.</p>
<p>The bigger the difference between the wetness of the skin and the absolute humidity, the more readily sweat evaporates.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-i-sweat-so-much-131135">Why do I sweat so much?</a>
</strong>
</em>
</p>
<hr>
<p>In arid climates, such as central Australia, where the absolute humidity is low, sweat evaporates so rapidly you can barely feel it on your skin.</p>
<p>Whereas in humid conditions, such as in northern Australia and more recently much of eastern Australia, sweat evaporation is hindered. </p>
<p>This is why on humid days we think we’re much sweatier, when in reality we may not be sweating that much more than any other warm day. It’s just more sweat is staying on our skin (rather than evaporating), forming patches on our clothes and making us feel sticky.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Man sweating in blue shirt" src="https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/445856/original/file-20220211-238-8kkvvj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Hot and sticky with all this humidity?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-hyperhidrosis-sweating-very-badly-under-767078800">Shutterstock</a></span>
</figcaption>
</figure>
<h2>What can we do about it?</h2>
<p>These three simple strategies will actually keep you cool on a humid day (without aircon):</p>
<p><strong>1. Use a fan</strong></p>
<p>Use a fan to <a href="https://jamanetwork.com/journals/jama/article-abstract/2110959">increase air flow</a> and accelerate sweat evaporation. These tend to work <a href="https://www.sciencedirect.com/science/article/pii/S2542519621001364">to at least 39°C</a>.</p>
<p>Misting fans <a href="https://www.sciencedirect.com/science/article/pii/S1440244021001092?casa_token=VfKIET08fTEAAAAA:2n8OqjI1xPzZB-ASMkeyIhrZplzkjItRSooTTT1OdrewatuuDbDiDzwYDiRCBYO5anHUyvBnKg">also work</a> well as water settles on the skin and subsequently evaporates, taking body heat with it. Alternatively, you can spray your skin with water and <a href="https://www.sciencedirect.com/science/article/pii/S0048969720347094">sit in front of a fan</a>.</p>
<p><strong>2. Use ‘ice towels’</strong></p>
<p>Wrap <a href="https://journals.lww.com/acsm-msse/fulltext/2017/05000/In_Play_Cooling_Interventions_for_Simulated.16.aspx">crushed ice in a damp towel</a> and wrap it around your neck. Professional tennis players regularly do this to keep cool. This circumvents the need for evaporation by taking heat straight from the body via conduction.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1476878329516937218"}"></div></p>
<p><strong>3. Wet your clothes</strong> </p>
<p>Soaking your t-shirt with water and putting it back on <a href="https://journals.physiology.org/doi/full/10.1152/japplphysiol.00786.2019">reduces the increase in core temperature</a> the same way as the evaporation of sweat. But it has the added bonus of not dehydrating the body. Alternatively, directly wetting the skin with a spray or wet sponge provides <a href="https://jamanetwork.com/journals/jama/article-abstract/2752456">the same benefit</a>.</p>
<h2>What won’t work</h2>
<p>Here are three strategies commonly recommended for beating the heat that won’t always work.</p>
<p><strong>1. Evaporative cooling</strong></p>
<p><a href="https://www.choice.com.au/home-and-living/cooling/air-conditioners/articles/evaporative-cooler-vs-air-conditioner">Evaporative coolers</a> work by passing hot air across a wet membrane to cool it. These work really well on hot, dry days. But on humid days, the air can hold less extra water, so evaporation is reduced and therefore, air is cooled far less.</p>
<p><strong>2. Drinking chilled drinks</strong></p>
<p>Although cold drinks may feel like they cool you down, it is mainly in your mind. Your body warms up the cold fluids or ice. At the same time, this triggers a <a href="https://journals.physiology.org/doi/full/10.1152/japplphysiol.01059.2013">reduction in sweating</a>, which reduces the amount of heat you lose via evaporation. One cancels out the other.</p>
<p>This results in the <a href="https://link.springer.com/article/10.1007/s40279-017-0842-8?platform=hootsuite_1&error=cookies_not_supported&code=890690fa-dc5b-493a-8ad7-9ccef673e811">same body temperature</a> irrespective of how cold (or hot) the drink is.</p>
<p>We’re not suggesting abandoning drinks altogether. In fact, you do need to replenish water that you sweat, to avoid dehydration. But don’t expect cold drinks to perform any better than warm ones. Just drink fluid at the temperature you find most palatable.</p>
<p>Similarly, eating cold food, such as ice cream or other frozen or chilled snacks, does not result in any net cooling effect. By all means, eat them if they make you feel better, but don’t expect them to actually cool you down.</p>
<p><strong>3. Sunscreen</strong></p>
<p>While it is very important to protect you skin from UV, there is no evidence wearing sunscreen makes any difference to how hot you get or how hot you feel.</p><img src="https://counter.theconversation.com/content/176365/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ollie Jay receives funding from National Health and Medical Research Council (NHMRC), Wellcome Trust (UK), MS Research Australia, NSW Dept of Industry and Environment, Tennis Australia, Cricket Australia, National Rugby League (NRL). He also serves as a consultant on research projects for the National Institutes of Health and US Dept of Defence. He served on Board of Trustees for the American College of Sports Medicine (ACSM) from 2018-21</span></em></p><p class="fine-print"><em><span>Connor Graham 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>On a hot and humid day, the fan is your friend. But ice cream won’t make the difference you think it will.Connor Graham, Research Fellow, Thermal Ergonomics Laboratory, University of SydneyOllie Jay, Professor of Heat & Health; Director of Heat & Health Research Incubator; Director of Thermal Ergonomics Laboratory, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1739042021-12-16T06:36:01Z2021-12-16T06:36:01ZHurricane-force wind gusts in Colorado, dust storms in Kansas, tornadoes in Iowa in December – here’s what fueled a day of extreme storms<figure><img src="https://images.theconversation.com/files/437954/original/file-20211216-23-w5ytwd.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1559%2C1059&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A satellite view on the night of Dec. 15, 2021, at the same time tornadoes were reported in Iowa.</span> <span class="attribution"><a class="source" href="https://www.star.nesdis.noaa.gov/GOES/conus.php?sat=G16">NOAA</a></span></figcaption></figure><p><em>Extremely powerful winds swept across a large part of the U.S. on Dec. 15, 2021, <a href="https://twitter.com/NWSSPC/status/1471333229537873924">hitting several states with hurricane-force gusts</a>. Record temperatures helped generate <a href="https://www.desmoinesregister.com/story/weather/2021/12/15/iowa-high-wind-tornado-map-weather-damage-power-outage-updates/8901263002/">tornadoes in Iowa</a>, winds spread <a href="https://twitter.com/NWSWichita/status/1471248332886470657">grass fires</a> and <a href="https://twitter.com/KWCH12/status/1471203794641997826">dust clouds</a> in Kansas, and wind damage was reported from <a href="https://www.thedenverchannel.com/weather/weather-news/see-the-highest-wind-gusts-recorded-during-colorados-wednesday-wind-storm">Colorado</a> through the Midwest. The National Weather Service described it as a “historical weather day” with a “<a href="https://twitter.com/NWS/status/1471117913767743495">never-before-seen storm outlook</a>.” A meteorologist with the service later <a href="https://www.radioiowa.com/2021/12/17/wednesdays-storm-is-derecho-part-two-for-iowa/">said it qualified as a “serial derecho”</a> – the powerful storm had winds over 80 mph but more spread out than the intense <a href="https://theconversation.com/what-is-a-derecho-an-atmospheric-scientist-explains-these-rare-but-dangerous-storm-systems-140319">derecho that hit Iowa in 2020</a>. At least <a href="https://apnews.com/article/tornadoes-iowa-nebraska-storms-kansas-ee9378aae1cb74911e0f9842a01ccaa1">five people died</a> in the storm, the Associated Press reported.</em></p>
<p><em>We asked <a href="https://ge-at.iastate.edu/directory/william-gallus/">atmospheric scientist William Gallus</a>, whose office at Iowa State University was at the heart of the storms, to explain what caused the extreme weather and why it was so unusual.</em></p>
<h2>What happened in the atmosphere to trigger such extreme weather over such a wide area?</h2>
<p>We were seeing very strong winds because of a very powerful disturbance in the <a href="https://www.weather.gov/jetstream/jet">jet stream</a>. That disturbance helped to create a very intense <a href="https://scijinks.gov/high-and-low-pressure-systems/">low-pressure system</a>, which creates strong winds and storms. But the low pressure wasn’t what made this event unusual.</p>
<p>It was unprecedented because an incredible amount of warm air got <a href="https://twitter.com/BMcNoldy/status/1471151049016688640/photo/1">pulled up from the south</a> ahead of the storm.</p>
<p>Here in Iowa, <a href="https://twitter.com/NWSWPC/status/1471307948945285123">temperatures were the hottest</a> they’ve ever been in December, with <a href="https://twitter.com/JerryWVTM13/status/1471221081000267783">temperatures in the mid 70s</a> on Dec. 15, and a very unusual amount of humidity came up with those temperatures. That’s why we were seeing <a href="https://twitter.com/NWSDesMoines/status/1471268524849078280">tornado warnings</a> <a href="https://twitter.com/NWSDesMoines/status/1471265167610572800">across the region</a> – and reports of <a href="https://www.desmoinesregister.com/story/weather/2021/12/15/iowa-high-wind-tornado-map-weather-damage-power-outage-updates/8901263002/">tornado damage</a>. </p>
<p>Tornadoes are <a href="https://twitter.com/capitalweather/status/1471281957569011713">extremely rare in Iowa in December</a>. Minnesota, which had never had a tornado in December, also had tornado warnings and <a href="https://twitter.com/NWSTwinCities/status/1471319877390508036">a possible sighting</a>.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1471258306903687169"}"></div></p>
<p>The wind speeds with this particular system were about as strong as we’ve seen. But it was all of the other weather parameters coming together in December that put this storm system off the scale.</p>
<p>With the warm moist air, we also had thunderstorms, and thunderstorms tend to make the winds even stronger. If you went up 1,000 feet in the sky, you would find it’s much <a href="https://news.stanford.edu/news/2009/june24/high-altitude-winds-062309.html">windier up there</a>. When you have thunderstorms, the rain helps create a current of wind that goes downward, which we call a downdraft. If you have this downdraft, it tends to carry the really strong winds down to the ground. Thunderstorms in the conditions we were seeing could bring winds that could easily get over 80 mph.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-is-a-derecho-an-atmospheric-scientist-explains-these-rare-but-dangerous-storm-systems-140319">What is a derecho? An atmospheric scientist explains these rare but dangerous storm systems</a>
</strong>
</em>
</p>
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<h2>Colorado saw wind gusts over 100 mph. What happened there?</h2>
<p>In Colorado, the mountains also help accelerate the wind. </p>
<p>The winds have to rise over the Rocky Mountains. If you get a <a href="https://www.weather.gov/media/lzk/inversion101.pdf">temperature inversion</a>, where the temperature actually starts to go up rather than down as you get higher in the atmosphere just above the top of the mountains, it can act like a lid that traps the momentum of the wind going over the mountains. The wind can’t really spread out, so instead it rushes downward once you’re on the east side of the mountains.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1471158494787108866"}"></div></p>
<p>With anything going downward, gravity accelerates it, just like if you drop a ball from the top of a skyscraper. The <a href="https://manoa.hawaii.edu/exploringourfluidearth/physical/atmospheric-effects/wind-formation">same thing happens to these winds</a>. As they flow down the east face of the Rockies, they accelerate. </p>
<p>When you’re on the leeward side of a mountain range, like Denver and Boulder, winds in those areas can <a href="https://twitter.com/NWSWPC/status/1471226860499525635">get really strong</a> as they’re descending.</p>
<h2>What role does the jet stream play in a storm like this?</h2>
<p>When we get a low-pressure system, it’s because of wiggles that are happening in the <a href="https://www.weather.gov/jetstream/jet">jet steam</a>. We call them troughs in meteorology.</p>
<figure class="align-right ">
<img alt="Image of the jet stream, looking like a wave" src="https://images.theconversation.com/files/437930/original/file-20211216-25-u8aefo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/437930/original/file-20211216-25-u8aefo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/437930/original/file-20211216-25-u8aefo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/437930/original/file-20211216-25-u8aefo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/437930/original/file-20211216-25-u8aefo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/437930/original/file-20211216-25-u8aefo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/437930/original/file-20211216-25-u8aefo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An visualization of the jet stream.</span>
<span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/3864">Trent L. Schindler/NASA Scientific Visualization Studio</a></span>
</figcaption>
</figure>
<p>If you look at a map showing the jet stream, the jet stream <a href="https://svs.gsfc.nasa.gov/3864">looks like a roller coaster</a> – it oscillates up and down, from north to south. Any time you’re out ahead of one of these troughs, where the jet stream bends down toward the south and then back toward the north, the air must rise out ahead of it, and this results in a low-pressure system. The winds that blow around it can become very strong. </p>
<p>In this case, there was an especially sharp trough in the jet stream, almost in a “V” shape, that intensified the effect. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/o203JXAnSA0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">What is the jet stream?</span></figcaption>
</figure>
<h2>Is there a connection between this storm and the deadly tornadoes that hit Kentucky and other states on Dec. 10-11?</h2>
<p>It’s hard to say if there was one trigger somewhere on the planet that managed to create these two different ripples in the jet stream.</p>
<p>What’s interesting is that there is <a href="https://www.climate.gov/news-features/blogs/enso/december-2021-la-ni%C3%B1a-update-visual-aids">La Niña going on in the Pacific Ocean</a>. When we have La Niña conditions, we often find that the far northern part of the United States ends up colder than normal and the south ends up warmer, so you have this bigger contrast in temperatures than normal and it often leads to a stronger jet stream.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/tornadoes-and-climate-change-what-a-warming-world-means-for-deadly-twisters-and-the-type-of-storms-that-spawn-them-173645">Tornadoes and climate change: What a warming world means for deadly twisters and the type of storms that spawn them</a>
</strong>
</em>
</p>
<hr>
<p>[<em>Over 140,000 readers rely on The Conversation’s newsletters to understand the world.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-140ksignup">Sign up today</a>.]</p>
<p><em>This article was updated with a National Weather Service meteorologist describing the storm as a “serial derecho.”</em></p><img src="https://counter.theconversation.com/content/173904/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William Gallus 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>Forecasters described it as a ‘historical weather day.’ An atmospheric scientist who was at the heart of the storms explains what happened.William Gallus, Professor of Atmospheric Science, Iowa State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1714082021-11-11T14:41:57Z2021-11-11T14:41:57ZCurious Kids: Why does cold air go down and hot air go up?<figure><img src="https://images.theconversation.com/files/430738/original/file-20211108-9897-12uhqlo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The land surface heats up during the day because of solar radiation coming in from the sun.</span> <span class="attribution"><span class="source">Ed Connor/Shutterstock</span></span></figcaption></figure><p><em>Curious Kids is <a href="https://theconversation.com/africa/topics/curious-kids-36782">a series</a> for children in which we ask experts to answer questions from kids.</em></p>
<p><strong>Does cold air go down because the earth’s core is made out of magma and does hot air go up because it’s cold out in space – and does the circle repeat? (Neo, 10, Boksburg, South Africa)</strong></p>
<p>Thank you, Neo, for this great question! You’ve clearly got a very analytical mind, and would make an excellent <a href="https://academickids.com/encyclopedia/index.php/Atmospheric_physics">atmospheric physicist</a> – that’s a researcher who looks at the physical processes happening in our atmosphere – one day. </p>
<p>The rising of hot air and sinking of cool air is important for almost every aspect of our day to day weather and our long term climate. It affects which way the wind blows and how fast it blows. It also affects whether we are likely to have rain, and the type of rainfall. Over larger areas of the earth, and over longer time periods, it even influences our seasons. So this is a really important question, and one which climatologists like myself work on in many aspects of our jobs.</p>
<p>I want to start by describing what’s happening in the earth’s core, then tell you a little bit about the temperature of space. Once I’ve done that, I’ll explain the real reasons hot air rises and cold air sinks.</p>
<h2>The Earth’s core and outer space</h2>
<p>If you were to cut a slice out of the earth, you would see four clear layers. The crust is the thin outer layer – much like an orange skin. The crust is hard, made up of solid rock. It’s the part of the earth that we walk on. Below that is a thicker layer called the mantle; it’s a <a href="https://coolscienceexperimentshq.com/viscosity-of-a-liquid-experiment/">viscous</a> layer of molten (melted) rock. Below that is the outer core, and right at the centre of the earth the inner core. These are very hot layers of molten rock and metal.</p>
<p>And you are quite right –- the earth’s core is <a href="https://www.nationalgeographic.org/encyclopedia/core/">very, very hot</a>. The inner core, made up of iron, is approximately 6,000°C. Even the upper mantle, just below the crust, has an average temperature of 2,000°C. That’s 100 times hotter than most daytime temperatures during spring in South Africa.</p>
<p>But the temperatures at the top of the crust are controlled far more by the sun than by the temperature of the centre of the earth. We’ll come back to that shortly.</p>
<p>Now, let’s talk about the temperature of space.</p>
<p>The earth is surrounded by an atmosphere – a layer of gases that we breathe in and out, and that control our temperatures by absorbing some of the heat, and reflecting the rest. Beyond the atmosphere is what is called “outer space”.</p>
<p>The temperature of outer space just outside the earth’s atmosphere is <a href="https://sciencing.com/temperatures-outer-space-around-earth-20254.html">about 10.17°C</a>. Outer space is heated directly by the sun. The areas in the sun are as warm as 120°C, while areas shaded by the earth are as cold as -100°C. Again, you’re right: this is a lot cooler than the earth’s inner core.</p>
<p>It’s correct that the earth’s core is very hot and space is much cooler. But that’s not the reason hot air rises and cool air sinks. </p>
<h2>Thermodynamics</h2>
<p>To come to the real reason, let’s turn to a field of science called <a href="https://www.britannica.com/science/thermodynamics">thermodynamics</a>. This is the branch of physics which studies heat and energy. Thermodynamics allows us to understand exactly what’s happening to individual bubbles of air. Did you know that the air around us is made of millions and millions of tiny air bubbles that sit very closely together?</p>
<p>Heating of the air can occur via conduction or convection – transferring heat to these air bubbles, and sharing it between them. The land surface heats up during the day because of solar radiation coming in from the sun. This incoming solar radiation is absorbed by the earth, warming it up. It is then released from the earth as long wave radiation, and heats up the air above the ground.</p>
<p>Those air bubbles then move around and bump into each other, sharing their heat between themselves.</p>
<p>When the ground heats up an air bubble above it, that air bubble expands – much like our feet swell up when they’re very hot in our shoes. As the air bubble heats up, the weight of that bubble is spread over a bigger area and so it becomes less dense.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/vSXTBnnx4OA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This is how density works.</span></figcaption>
</figure>
<p>As these air bubbles become less dense, they rise because they weigh less than what’s next to them. This is the same when you let go of a helium balloon and it floats away: the helium gas in the balloon is less dense than the air in our atmosphere (which is made up of a large amount of much heavier nitrogen). </p>
<p>The opposite happens when air cools down. The air bubbles contract, their weight takes up much less space and so they become more dense, and sink. This can happen if the air particles move away from the source of heat; they might have risen very high, or moved to an area over a cool lake or over some shade.</p>
<p>So, there’s no link between the earth’s core, space’s temperature and the behaviour of cold air versus hot air. But you definitely think like a scientist, Neo, because you are interested in how one thing influences another. Maybe one day you’ll study thermodynamics, too!</p><img src="https://counter.theconversation.com/content/171408/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Fitchett receives funding from the DSI-NRF Centre of Excellence (GENUS). </span></em></p>This is a really important question, and one which climatologists work on in many aspects of their jobs.Jennifer Fitchett, Associate Professor of Physical Geography, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1713272021-11-10T14:43:18Z2021-11-10T14:43:18ZExtreme heat hurts human health. Its effects must be mitigated – urgently<figure><img src="https://images.theconversation.com/files/430752/original/file-20211108-19-1tn54mx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Higher temperatures cause drought, and can lead to food insecurity
</span> <span class="attribution"><span class="source">Guido Dingemans, De Eindredactie/GettyImages</span></span></figcaption></figure><p>The African continent is heating up more, and faster, than other regions in the world according to the recently released <a href="https://www.uneca.org/stories/state-of-climate-in-africa-report-2020">State of Climate in Africa Report</a>. By 2030, the report says up to 118 million extremely poor people will be subject to the devastating impacts of drought and intense heat.</p>
<p>Many of the temperatures presently being recorded in Africa, and those projected in the next decade, are <a href="https://doi.org/10.1038/s41558-018-0145-6">already close</a> to the limits of human survival, or “liveability”. </p>
<p>The general limit of heat we should live in is 35°C wet-bulb temperature, which is a measure of both air temperature and humidity. Beyond this, the body struggles to cool itself.</p>
<p>In northern Mali, for example, many communities <a href="https://www.cifor.org/knowledge/publication/3524/">have to make do</a> with a rainy season of just three months, from July to September. For the rest of the year, temperatures approach 50°C. The consequences have been catastrophic, impacting health and agriculture and livestock activities. Younger generations have no option but to leave as they cannot survive in these conditions.</p>
<p>Extreme heat is a serious health hazard. It can have very negative health effects on the human body. The body responds to <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01208-3/fulltext">heat stress by</a> redistributing blood flow to the skin and producing sweat, thus cooling the body. These blood flow changes increase the demand on the heart, making it work harder. Additional sweat production can also lead to dehydration, reducing blood volume which strains the heart further and also causes damage to organs such as the kidney.</p>
<p>Despite this, extreme heat has drawn less attention than other climate risks, such as flooding and drought. </p>
<p>The 26th UN Climate Change Conference of the Parties (COP26) provides an opportunity to focus in more detail on the health effects of extreme heat in African countries and elsewhere. Particular attention should be paid to how vulnerable groups like women, newborn children and poorer people can be helped to deal with or mitigate against these effects.</p>
<h2>How heatwaves affect people</h2>
<p>There are various ways in which rising temperatures will affect people. </p>
<p>Heatwaves – generally considered to be several days of excessively hot weather, which may be accompanied by high humidity – <a href="https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(20)30274-6/fulltext">worsen</a> the risk of death from heatstroke. This happens when the body is unable to control its temperature which then rises rapidly to 40°C or more causing internal organ damage. </p>
<p>It also means more people with certain ailments – such as kidney or respiratory diseases – are at a higher risk of dying.</p>
<p>As temperatures rise, there’ll be an <a href="https://www.thelancet.com/journals/lanplh/article/PIIS2542-51962100132-7/fulltext">increased spread</a> of infectious diseases, such as malaria and dengue fever. This is because more areas will become suitable for vectors, like mosquitoes that carry malaria.</p>
<p>Increased heat will also result in more drought which will result in crop failure and livestock deaths. This will lead to under- and malnutrition, especially in children, with higher rates of stunting or worse a result. Projections using temperature changes in sub-Saharan Africa <a href="https://pubmed.ncbi.nlm.nih.gov/33139856/">suggest</a> considerable increases in malnutrition. For instance, it’s expected that by 2100 there’ll be an increase in prevalence of wasting in western Africa by 37%, and 25% for central and eastern Africa. </p>
<p>More heat also means <a href="https://icpac.medium.com/wildfires-in-eastern-africa-will-climate-change-increase-the-intensity-of-wildfires-573ba35a5e10">more wildfires</a>. Wildfires affect humans in several ways including burns, pollutants from smoke and psychological trauma. Increased vulnerability to wildfires is <a href="https://icpac.medium.com/wildfires-in-eastern-africa-will-climate-change-increase-the-intensity-of-wildfires-573ba35a5e10">expected</a> in East Africa due to a combination of temperature change and unsustainable land management practices, such as clearing and setting fire to land to plant crops.</p>
<h2>Most at risk</h2>
<p>It is important to understand which groups are most at risk from the negative effects of extreme heat. </p>
<p><a href="https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(20)30274-6/fulltext">A review</a> of climate change and health literature earlier this year found a greater mortality risk from heatwaves for children, especially infants. Children are more at risk as they have smaller surface to body ratios than adults (increasing dehydration and heat stress risk) and they are still growing with underdeveloped systems, such as respiratory and immune systems.</p>
<p>Older people are more vulnerable to heat stress because their bodies are less able to adapt to changes in body temperature and they may have chronic medical conditions.</p>
<p>Extreme heat is also a high risk factor for pregnant women and their babies. A summary of evidence on the obstetric risks of heat reported many associated adverse effects <a href="https://www.bmj.com/content/371/bmj.m3811.long">including</a> maternal hypertension <a href="https://obgyn.onlinelibrary.wiley.com/doi/full/10.1002/ijgo.13958">and</a> placental abruption (the separation of the placenta from the uterus which can cause pregnancy complications), stillbirths, preterm birth, and low birth weight. Some of these complications could be because extreme heat causes dehydration and may lead to contractions and fainting. Exposure to extreme heat in a woman’s first trimester may also cause foetal heart and neural tube defects.</p>
<p>Finally, heat is expected to have worse outcomes for more vulnerable members of society. </p>
<p>A <a href="https://www.tandfonline.com/doi/full/10.1080/16549716.2021.1908064">review</a> of the effects of climate change – in low- and middle-income countries found that residents of informal urban settlements are particularly at risk. That’s because of vulnerabilities like limited access to healthcare, poor sanitation and overcrowding. A <a href="https://www.sciencedirect.com/science/article/abs/pii/S0048969720348841?via%3Dihub">case study</a> of informal settlements in Dar es Salaam, Tanzania, reinforces the review’s findings: it shows that higher temperatures pose a significant risk to health – for instance because tin roofs exacerbate heat stress – even if the city doesn’t reach extreme temperatures.</p>
<p>As for those living in rural areas, such as pastoralists, aside from the stress extreme heat puts on their bodies, pastoralists will be vulnerable to drought and food insecurity. </p>
<h2>Moving forward</h2>
<p>These are not problems for the future. As the examples above and many others highlight, Africa is already feeling the reality of heat stress. All the projections suggest it will only get worse, yet nearly all heat-related adverse health outcomes and deaths are preventable. </p>
<p>But the continent has limited research capacity to examine these challenges and inform policy. Most of the research has focused on current impacts and that risks will continue to increase with additional climate change. Moving beyond this to identify solutions that are effective in the African context is an essential step.</p>
<p>There’s <a href="http://www.mdpi.com/2071-1050/13/9/5312">low scientific growth</a> in publications output and a large evidence gap both in understanding heat stress and relevant interventions to adapt to these changing environmental circumstances. </p>
<p>The research that needs to be done includes vulnerability assessments, urban heat island evaluation and studies that focus on heat adaptation measures that might prevent the worst effects of extreme heat.</p>
<p>In addition to more research, the continent needs immediate financial and technological assistance to adapt to the warming environment and to support research. </p>
<p>Heat risks are complex. They require strong research foundations and integrated planning, for example across health systems and urban planning. Early warning systems are also needed that actively involve communities to avoid or mitigate at least some adverse effects.</p>
<p>It is imperative that people from different disciplinary backgrounds work on climate and health issues together, coordinate, and develop new ideas together. One example is the new network – <a href="https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.enbel-project.eu%2Fevents-page%2Fchance-a-new-network-for-climate-and-health-in-africa&data=04%7C01%7CAbdu.Mohiddin%40aku.edu%7Cacbe54b343f94fe4726c08d99916dbc1%7Ca5d4252a02f94e6096f09733baae4919%7C0%7C0%7C637709145716788230%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=VWDh8MSO5qIxtQ34DTNHgCSqnfZeGcnj7Lj%2F2IYkNpE%3D&reserved=0">CHANCE (Climate-Health Africa Network for Collaboration and Engagement)</a> – which is funded by the European Commission EU’s Horizon 2020 programme. It aims to facilitate interactions and create greater coherence between these, sometimes, siloed communities of practice. </p>
<p>It’s imperative that all of this happens fast. People are already living with the effects of a warming environment, with devastating effects. </p>
<p>_Caroline Gichuki, an emerging researcher in the field of climate change and health, helped in the writing of this article. _</p><img src="https://counter.theconversation.com/content/171327/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Jack receives funding from NERC, EU Commission, and the NIH</span></em></p><p class="fine-print"><em><span>Evans Kituyi consults for UNEP and GIZ.</span></em></p><p class="fine-print"><em><span>Kristie Ebi receives funding from the World Health Organization and the US National Institutes of Health.</span></em></p><p class="fine-print"><em><span>Matthew Chersich receives funding from the EU, NIH and Belmont Forum </span></em></p><p class="fine-print"><em><span>Stanley Luchters receives funding from the Belmont Forum, European Commission and the US NIH.</span></em></p><p class="fine-print"><em><span>Abdu Mohiddin does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Many of the temperatures presently being recorded in Africa, and those projected in the next decade, are already close to the limits of human survival, or “liveability”.Abdu Mohiddin, Assistant Professor, Aga Khan University Christopher Jack, Researcher, University of Cape TownEvans Kituyi, Associate, Institute for Climate Change & Adaptation, University of NairobiKristie Ebi, Professor of Global Health and Environmental and Occupational Health Sciences, University of WashingtonMatthew Chersich, Professor, University of the WitwatersrandStanley Luchters, Professor, Aga Khan University HospitalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1705562021-11-01T18:38:23Z2021-11-01T18:38:23ZThe science everyone needs to know about climate change, in 6 charts<figure><img src="https://images.theconversation.com/files/428635/original/file-20211026-23-1ky80w7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientific instruments in space today can monitor hurricane strength, sea level rise, ice sheet loss and much more.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/gsfc/48698288003">Christina Koch/NASA</a></span></figcaption></figure><p><em><a href="https://theconversation.com/las-nociones-cientificas-sobre-el-cambio-climatico-que-todos-deberiamos-conocer-en-seis-graficos-171149">Leer en español</a></em></p>
<p>With the United Nations’ climate conference in Scotland turning a spotlight on climate change policies and the impact of global warming, it’s useful to understand what the science shows.</p>
<p>I’m an <a href="https://cires.colorado.edu/research/research-groups/elizabeth-weatherhead-group">atmospheric scientist</a> who has worked on global climate science and assessments for most of my career. Here are six things you should know, in charts.</p>
<h2>What’s driving climate change</h2>
<p>The primary focus of the negotiations is on carbon dioxide, a greenhouse gas that is released when fossil fuels – coal, oil and natural gas – are burned, as well as by forest fires, land use changes and natural sources.</p>
<p>The Industrial Revolution of the late 1800s started an enormous increase in the burning of fossil fuels. It powered homes, industries and opened up the planet to travel. That same century, scientists <a href="https://theconversation.com/scientists-understood-physics-of-climate-change-in-the-1800s-thanks-to-a-woman-named-eunice-foote-164687">identified carbon dioxide’s potential</a> to <a href="https://www.rsc.org/images/Arrhenius1896_tcm18-173546.pdf">increase global temperatures</a>, which at the time was considered a possible benefit to the planet. Systematic measurements started in the mid-1900s and have shown a steady increase in carbon dioxide, with <a href="https://www.ipcc.ch/assessment-report/ar6/">the majority of it directly traceable</a> to the combustion of fossil fuels.</p>
<p><iframe id="kkVw7" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/kkVw7/23/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Once in the atmosphere, carbon dioxide tends to stay there for a very long time. A portion of the carbon dioxide released through human activities is taken up by plants, and some is absorbed directly into the ocean, but <a href="https://public.wmo.int/en/media/press-release/greenhouse-gas-bulletin-another-year-another-record">roughly half</a> of all carbon dioxide emitted by human activities today stays in the atmosphere — and it <a href="https://tos.org/oceanography/article/an-accounting-of-the-observed-increase-in-oceanic-and-atmospheric-co2-and-a">likely will remain there for hundreds of years</a>, influencing the climate globally.</p>
<p>During the <a href="https://www.iea.org/articles/global-energy-review-co2-emissions-in-2020">first year of the pandemic in 2020</a>, when fewer people were driving and some industries briefly stopped, carbon dioxide emissions from fuels fell by roughly 6%. But it <a href="https://essd.copernicus.org/articles/12/3269/2020/">didn’t stop the rise in the concentration of carbon dioxide</a> because the amount released into the atmosphere by human activities far exceeded what nature could absorb.</p>
<p>If civilization stopped its carbon dioxide-emitting activities today, it would <a href="https://tos.org/oceanography/article/an-accounting-of-the-observed-increase-in-oceanic-and-atmospheric-co2-and-a">still take many hundreds of years</a> for the concentration of carbon dioxide in the atmosphere to fall enough naturally to bring the planet’s carbon cycle back into balance because of carbon dioxide’s long life in the atmosphere.</p>
<p><iframe id="dE1UL" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/dE1UL/8/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>How we know greenhouse gases can change the climate</h2>
<p>Multiple lines of scientific evidence point to the increase in greenhouse emissions over the past century and a half as a driver of long-term climate change around the world. For example:</p>
<ul>
<li><p>Laboratory measurements <a href="https://www.rsc.org/images/Arrhenius1896_tcm18-173546.pdf">since the 1800s</a> have repeatedly verified and quantified the absorptive properties of carbon dioxide that allow it to trap heat in the atmosphere.</p></li>
<li><p><a href="https://esd.copernicus.org/articles/12/545/2021/esd-12-545-2021-discussion.html">Simple models</a> based on the warming impact of carbon dioxide in the atmosphere <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017MS001038">match historical changes in temperature</a>.</p></li>
<li><p>Complex climate models, recently acknowledged in <a href="https://theconversation.com/winners-of-2021-nobel-prize-in-physics-built-mathematics-of-climate-modeling-making-predictions-of-global-warming-and-modern-weather-forecasting-possible-169329">the Nobel Prize for Physics</a>, not only indicate a warming of the Earth due to increases in carbon dioxide but also <a href="https://gmd.copernicus.org/articles/9/3461/2016/">offer details of the areas of greatest warming</a>.</p></li>
</ul>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/429261/original/file-20211029-26-whwkeu.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/429261/original/file-20211029-26-whwkeu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/429261/original/file-20211029-26-whwkeu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=353&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429261/original/file-20211029-26-whwkeu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=353&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429261/original/file-20211029-26-whwkeu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=353&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429261/original/file-20211029-26-whwkeu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=444&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429261/original/file-20211029-26-whwkeu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=444&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429261/original/file-20211029-26-whwkeu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=444&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When carbon dioxide levels have been high in the past, evidence shows temperatures have also been high.</span>
<span class="attribution"><a class="source" href="https://link.springer.com/chapter/10.1007/978-3-319-46939-3_1">Based on Salawitch et al., 2017, updated with data to the end of 2020</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<ul>
<li><p>Long-term records from <a href="https://doi.org/10.1038/s41586-018-0172-5">ice cores</a>, <a href="https://www.nytimes.com/2019/04/30/science/tree-rings-climate.html">tree rings</a> and <a href="https://www.aims.gov.au/docs/research/climate-change/climate-history/climate-history.html">corals</a> show that when carbon dioxide levels have been high, temperatures have also been high.</p></li>
<li><p>Our neighboring planets also offer evidence. Venus’ atmosphere is thick with carbon dioxide, and it is the <a href="https://doi.org/10.1029/95JE03862">hottest planet</a> in our solar system as a result, even though Mercury is closer to the sun. </p></li>
</ul>
<h2>Temperatures are rising on every continent</h2>
<p>The rising temperatures are evident in records from every continent and over the oceans.</p>
<p>The temperatures aren’t rising at the same rate everywhere, however. A variety of factors affect local temperatures, including land use that influences how much solar energy is absorbed or reflected, local heating sources like <a href="https://scied.ucar.edu/learning-zone/climate-change-impacts/urban-heat-islands">urban heat islands</a>, and pollution.</p>
<p>The Arctic, for example, is warming about <a href="https://www.nilu.com/2021/05/amap-increase-in-arctic-temperature-is-three-times-higher-than-the-global-average/">three times faster than the global average</a> in part because as the planet warms, snow and ice melt makes the surface more likely to absorb, rather than reflect, the sun’s radiation. Snow cover and sea ice recede even more rapidly as a result. </p>
<p><iframe id="yV1Al" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/yV1Al/12/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>What climate change is doing to the planet</h2>
<p>Earth’s climate system is interconnected and complex, and even small temperature changes can have large impacts – for instance, with snow cover and sea levels.</p>
<p>Changes are already happening. Studies show that rising temperatures are <a href="https://www.ipcc.ch/assessment-report/ar6/">already affecting</a> precipitation, glaciers, weather patterns, tropical cyclone activity and severe storms. A number of studies show that the <a href="https://www.epa.gov/climate-indicators/climate-change-indicators-heat-waves">increases in frequency</a>, severity and duration of heat waves, for example, <a href="https://www.science.org/doi/10.1126/science.1098704">affect ecosystems, human lives</a>, commerce and agriculture.</p>
<p>Historical records of ocean water level have shown mostly consistent increases over the past 150 years as glacier ice melts and rising temperatures expand ocean water, with some local deviations due to sinking or rising land.</p>
<p><iframe id="AYpRq" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/AYpRq/6/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>While extreme events are often due to complex sets of causes, some are exacerbated by climate change. Just as coastal flooding can be made worse by rising ocean levels, heat waves are more damaging with higher baseline temperatures.</p>
<p>Climate scientists work hard to estimate future changes as a result of increased carbon dioxide and other expected changes, such as world population. It’s clear that temperatures will increase and precipitation will change. The exact magnitude of change depends on many interacting factors. </p>
<figure class="align-center ">
<img alt="Models of future temperature and precipitation in map form" src="https://images.theconversation.com/files/429867/original/file-20211103-21-1omk71v.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/429867/original/file-20211103-21-1omk71v.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=721&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429867/original/file-20211103-21-1omk71v.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=721&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429867/original/file-20211103-21-1omk71v.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=721&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429867/original/file-20211103-21-1omk71v.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=906&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429867/original/file-20211103-21-1omk71v.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=906&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429867/original/file-20211103-21-1omk71v.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=906&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Based on SSP3-7.0, a high-emissions scenario.</span>
<span class="attribution"><a class="source" href="https://esd.copernicus.org/articles/12/253/2021/">Claudia Tebaldi, et al., 2021</a></span>
</figcaption>
</figure>
<h2>A few reasons for hope</h2>
<p>On a hopeful note, scientific research is improving our understanding of climate and the complex Earth system, identifying the most vulnerable areas and guiding efforts to reduce the drivers of climate change. Work on renewable energy and alternative energy sources, as well as ways to capture carbon from industries or from the air, are producing more options for a better prepared society. </p>
<p>At the same time, people are learning about how they can reduce their own impact, with the growing understanding that a globally coordinated effort is required to have a significant impact. <a href="https://www.bts.gov/data-spotlight/electric-vehicle-use-grows">Electric vehicles, as well as solar and wind power, are growing</a> at previously unthinkable rates. More people are showing a <a href="https://theconversation.com/pews-new-global-survey-of-climate-change-attitudes-finds-promising-trends-but-deep-divides-167847">willingness to adopt new strategies</a> to use energy more efficiently, consume more sustainably and choose renewable energy. </p>
<p>Scientists increasingly recognize that shifting away from fossil fuels has <a href="https://www.sciencedirect.com/science/article/abs/pii/S0269749107002849">additional benefits</a>, including <a href="https://books.google.com/books?hl=en&lr=&id=YmNnDwAAQBAJ&oi=fnd&pg=PP4&dq=World+Health+Organization,+2018,+Health,+environment+and+climate+change:+report+by+the+Director-General&ots=zQRnV6VGzD&sig=hsqdBTGjE45iZB-ECYP4HNlIQWc">improved air quality</a> for human health and ecosystems.</p>
<figure class="align-right ">
<img alt="COP26: the world’s biggest climate talks" src="https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.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>This story is part of The Conversation’s coverage of COP26, the Glasgow climate conference, by experts from around the world.</strong>
<br><em>Amid a rising tide of climate news and stories, The Conversation is here to clear the air and make sure you get information you can trust. <a href="https://theconversation.com/us/cop26">Read more of our U.S.</a> and <a href="https://page.theconversation.com/cop26-glasgow-2021-climate-change-summit/">global coverage</a>.</em></p><img src="https://counter.theconversation.com/content/170556/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Betsy Weatherhead 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>Take a closer look at what’s driving climate change and how scientists know CO2 is involved, in a series of charts examining the evidence in different ways.Betsy Weatherhead, Senior Scientist, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1692272021-10-05T12:04:36Z2021-10-05T12:04:36ZNobel prize: how chilli peppers helped researchers uncover how humans feel pain<p>Think about how often we sense touch or temperature. Perhaps its the warmth we feel when we hold a coffee cup, or the comfort we feel when hugging a loved one – these sensations are integral to our everyday lives and how we interact with our world. These sensations are all part of our somatosensory system, which is responsible for many different sensations – including temperature, touch, body position and movement, pain and itch. Some might say that the combined effects of our somatosensory system are the very essence of what it is to connect to the world around us, and to experience it. </p>
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<p>But until the late 1990s, little was known about how the body actually senses temperature and pressure. This is why the <a href="https://www.nobelprize.org/prizes/medicine/2021/summary/">2021 Nobel prize in physiology or medicine</a> was jointly awarded to David Julius and Ardem Patapoutian, whose independent research uncovered the receptors which allow us to sense touch and temperature.</p>
<p>The discoveries made by Julius and Patapoutian help solve questions many people have been asking for years – showing us how these stimuli are converted into nerve signals at a molecular level. These discoveries may also have important implications for developing treatments for a variety of different conditions, including chronic pain, in the future. </p>
<h2>A bit of spice</h2>
<p>Both researchers began working on this topic in the 1990s, but were looking at it in different ways. Julius and his colleagues at the University of California were looking at a rather unconventional compound known as capsaicin, which is the chemical which causes the burning sensation we feel when we touch or eat chilli peppers. While researchers already knew capsaicin activated nerve cells that caused sensations of pain, Julius sought to uncover which sensors in the nerve endings actually respond to the heat from this compound.</p>
<p>Using lab-grown neurons – humans nerve cells – Julius and his team created a library of millions of DNA strands that corresponded to genes in the sensory neurons that react to pain, heat and touch. This eventually led them to identify a single gene that was responsible for <a href="https://pubmed.ncbi.nlm.nih.gov/9349813/">making cells sensitive</a> to capsaicin. The gene allows cells to build a protein called TRPV1 which led to these receptors perceiving the <a href="https://pubmed.ncbi.nlm.nih.gov/9768840/">heat from capsaicin as painful</a>.</p>
<p>This was the first of many more temperature-sensing receptors Julius and his lab discovered. Using menthol, Julius identified TRPM8, a receptor shown to be <a href="https://www.nature.com/articles/nature719">activated by cold</a>. He also used the chemical found in wasabi to identify TRPA1, which is triggered by pain. Julius’s TRPV1 discovery was a breakthrough which allowed further research into how temperature induces electrical signals in the nervous system.</p>
<p>Patapoutian, from the Scripps Research institute in California, uncovered the mechanisms which underpin our sense of touch. Patapoutian’s research first began when he and his team identified a type of cell that gave off an electrical signal when it was poked with a micropipette. But to understand more about these pressure-sensitive cells, Patapoutian and his team first needed to identify which receptor was responsible. </p>
<p>They started with 72 candidate genes, inactivating them one by one until they found that the single gene responsible for creating the protein which responds pressure on cell membranes – <a href="https://pubmed.ncbi.nlm.nih.gov/20813920/">known as Piezo1</a>. This discovery then led them to find a second gene, <a href="https://pubmed.ncbi.nlm.nih.gov/25471886/">called Piezo2</a>, which functions similarly.</p>
<p>This decades-long search now means researchers understand the mechanisms underpinning our <a href="https://pubmed.ncbi.nlm.nih.gov/26551544/">sense of touch</a>. Piezo1 and Piezo2 both work to initiate an electrical signal that travels between cells and to the brain when our skin or internal organs are touched or feel pressure. </p>
<h2>The importance of these senses</h2>
<p>Mammals are the only organisms that have the ability to generate and maintain our internal body temperature. If our blood temperature falls below 27°C we’re in critical condition. It’s essential for survival to be able to sense temperature changes in our environment in order to maintain our core body temperature. It tells us that we should put a coat on if it’s cold outside, or not to touch a hot stove door so we don’t get hurt. </p>
<p>Julius’s discovery of the temperature sensitive receptors in our nerves means we now know how changes in our environment’s temperature is detected. Discovering both the receptors that detect heat – TRPV1 – and cold – TRPM8 – now means we may have targets for drugs to treat inflammation, itch, pain and cold allodynia (increased sensitivity to cold temperatures). </p>
<p>Our sense of touch is also extremely important to us for a number of reasons – not least of which because it allows us to enjoy a hug. Being able to detect a mechanical stimulus – the sense we call touch – is important to every tissue and cell in our body. It means that the body can monitor blood flow, a full stomach, or when our bladder is full. </p>
<p>Patapoutian’s research means that we now understand which receptors allow us to sense touch, which could have many implications for future treatments. Researchers are already targeting the proteins Patapoutian discovered for the treatment of pain conditions.</p><img src="https://counter.theconversation.com/content/169227/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Francis McGlone 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>These discoveries could help us treat a variety of conditions in the future – including chronic pain.Francis McGlone, Professor in Neuroscience, Liverpool John Moores UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1637002021-07-08T12:36:51Z2021-07-08T12:36:51ZKnowing how heat and humidity affect your body can help you stay safe during heat waves<figure><img src="https://images.theconversation.com/files/410012/original/file-20210706-25-13zbvfw.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5593%2C3124&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Record-breaking triple-digit heat in Olympia, Wash., on June 28, 2021.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/PacificNorthwestHeatWave/52ee9fd2284b4ac3ab5a0f441da4a08f/photo">AP Photo/Ted S. Warren</a></span></figcaption></figure><p>Less than a month into North America’s official summer, heat waves are blistering much of the West. California and the Southwest are facing <a href="https://www.washingtonpost.com/weather/2021/07/06/california-west-heat-wave/">excessive heat watches</a> for the second time, after a <a href="https://www.climate.gov/news-features/event-tracker/record-breaking-june-2021-heatwave-impacts-us-west">mid-June heat wave</a> pushed temperatures above 100 F (38 C). </p>
<p>And in late June an intense heat dome settled over the <a href="https://www.climate.gov/news-features/event-tracker/astounding-heat-obliterates-all-time-records-across-pacific-northwest">Pacific Northwest</a> for four days, setting all-time temperature records in Oregon, Washington and British Columbia. The effects were most evident in Lytton, British Columbia, which reported a temperature of <a href="https://www.washingtonpost.com/weather/2021/06/27/heat-records-pacific-northwest/">121 F (49.5 C) on June 29</a>, far above its average high for the date of 76 F (24.4 C). A day later, the town was <a href="https://www.cnn.com/2021/07/01/americas/canada-town-evacuation-extreme-heat/index.html">engulfed by a wildfire</a>.</p>
<p>As an <a href="https://scholar.google.com/citations?user=wqDX7PUAAAAJ&hl=en">exercise physiologist</a>, I know that the human body is an amazing machine. But like all machines, it functions effectively and safely only under certain conditions. </p>
<p>People frequently debate whether wet heat in places like Florida or dry heat in desert locations like Nevada is worse. The answer is that either setting can be dangerous. Hot desert climates are stressful due to extreme temperatures, while humid subtropical climates are stressful because the body has trouble removing heat when sweat doesn’t evaporate readily. As recent events have shown, hot is hot.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1412139233565843456"}"></div></p>
<h2>The influence of humidity</h2>
<p>North America has a wide range of climates, but when people talk about heat, they often compare the Southwest and the Southeast. Some communities in the Southwest’s hot desert climates, such as Las Vegas, have average summer high temperatures over 100 F (38 C), with <a href="https://www.ncdc.noaa.gov/ghcn/comparative-climatic-data">relative humidity</a> typically around 20%. This means the air is holding about one-fifth of the maximum amount of moisture it can hold at that temperature and pressure. </p>
<p>In contrast, Southeast locations like Orlando, Florida, typically have average temperatures around 90 F (32.2 C), with humidity regularly approaching 80%. Looking only at temperature, the desert clearly is hotter on average. </p>
<p>However, it’s also important to consider how heat affects the body. Weather reports often do this using the <a href="https://www.weather.gov/ama/heatindex">heat index</a>, which calculates how the human body perceives conditions factoring in humidity as well as heat. </p>
<p>Sweating is your body’s primary way of cooling you off. When sweat evaporates away from your skin, it <a href="https://www.weather.gov/oun/safety-summer-heathumidity">takes heat with it</a>. But when humidity is high, the air already holds a lot of moisture, so the sweat remains on your skin. As it saturates clothing and drips from the body, it can remove only a small amount of heat compared with the cooling that comes with the evaporation of sweat. </p>
<p>As a result, when we account for humidity, the heat exposures people experience in Las Vegas and Orlando are very similar. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/410019/original/file-20210706-17-ozucpq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Table showing hazardous heat/humidity combinations." src="https://images.theconversation.com/files/410019/original/file-20210706-17-ozucpq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/410019/original/file-20210706-17-ozucpq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=351&fit=crop&dpr=1 600w, https://images.theconversation.com/files/410019/original/file-20210706-17-ozucpq.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=351&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/410019/original/file-20210706-17-ozucpq.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=351&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/410019/original/file-20210706-17-ozucpq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=441&fit=crop&dpr=1 754w, https://images.theconversation.com/files/410019/original/file-20210706-17-ozucpq.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=441&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/410019/original/file-20210706-17-ozucpq.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=441&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 National Weather Service’s Heat Index shows the risk of activity based on heat plus humidity.</span>
<span class="attribution"><a class="source" href="https://dps.mn.gov/divisions/hsem/weather-awareness-preparedness/Pages/severe-weather-heat.aspx">NOAA</a></span>
</figcaption>
</figure>
<h2>Adapting people and places to heat stress</h2>
<p>As people go through their daily lives, their bodies work continuously to maintain a temperature close to a normal level of about 98.6 F (37 C). In regions that regularly experience high heat stress, such as the Southeast and Southwest, most buildings and homes now have air conditioning, which helps people maintain healthy temperatures.</p>
<p>But in areas where heat is unusual, such as the Pacific Northwest, many buildings and residences <a href="https://www.seattletimes.com/seattle-news/health/with-more-heat-waves-expected-in-the-future-seattles-long-term-care-facilities-weigh-the-need-for-air-conditioning/">lack cooling</a>. As a result, people are exposed to higher heat for longer periods of time during events like the region’s late June heat wave than they would be in regions where hot weather is the norm.</p>
<p>Just as buildings and residences in areas chronically exposed to heat are equipped with ceiling fans and air conditioning, bodies that are regularly exposed to heat can <a href="https://www.cdc.gov/niosh/mining/userfiles/works/pdfs/2017-124.pdf">acclimatize</a>, or adapt and improve their ability to cool. This starts to occur with the first heat exposure – for example, the beginning of fall sports practices in August – but take weeks of regular exposure to reach maximal levels. </p>
<p>One of the first things our bodies do in adapting to heat is to <a href="http://dx.doi.org/10.1111/sms.12408">produce more plasma</a> – the watery portion of blood. This enables our circulatory systems to move heat to the skin more effectively so that sweating can remove it from the body.</p>
<p>We also begin sweating earlier than people who are not acclimatized to heat, and our <a href="https://doi.org/10.3390/nu13061807">maximal sweat rate increases</a>. These adaptations improve our bodies’ ability to dissipate heat to the environment. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/410017/original/file-20210706-23-1ljbuxh.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Workplace flyer with tips for acclimatizing to heat." src="https://images.theconversation.com/files/410017/original/file-20210706-23-1ljbuxh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/410017/original/file-20210706-23-1ljbuxh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1285&fit=crop&dpr=1 600w, https://images.theconversation.com/files/410017/original/file-20210706-23-1ljbuxh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1285&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/410017/original/file-20210706-23-1ljbuxh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1285&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/410017/original/file-20210706-23-1ljbuxh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1615&fit=crop&dpr=1 754w, https://images.theconversation.com/files/410017/original/file-20210706-23-1ljbuxh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1615&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/410017/original/file-20210706-23-1ljbuxh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1615&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Outdoor workers should build up to a full day in the heat to allow their bodies to acclimatize to it.</span>
<span class="attribution"><a class="source" href="https://www.cdc.gov/niosh/topics/heatstress/pdf/NIOSH_HeatStressInfographic_print-508.pdf">CDC</a></span>
</figcaption>
</figure>
<p>Behavior changes are another way of adapting to heat stress. Since midday is typically the hottest part of the day, it makes sense to avoid physical work and exercise then. When people are active, their bodies break down nutrients – carbohydrates, fats and protein – into energy. This powers movement and also generates metabolic heat, which adds to the body’s heat stress.</p>
<p>Taking advantage of shade is another important strategy. Heat radiating from the Sun adds to the stress produced by warm air temperatures. Staying in the shade can significantly reduce the external heat load on <a href="https://blogs.cdc.gov/niosh-science-blog/2021/05/07/heat-stress-2021/">people who have to be outdoors during hot spells</a>.</p>
<p>Many of the <a href="https://doi.org/10.1136/bmj.n1696">hundreds of deaths and hospitalizations</a> that experts have attributed to the recent heat dome in the Northwest probably reflect that buildings there were less equipped to keep people cool than in hotter regions, and residents were less acclimatized to heat.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/Q2RQjtucG3M?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">2020 was Phoenix’s hottest year on record, with 53 days reaching at least 110 F.</span></figcaption>
</figure>
<h2>The old and young are most vulnerable</h2>
<p>A healthy adult body can acclimatize to heat, but older people and children are less able to adjust. As people age, their cardiovascular systems change in ways that cause them to <a href="https://www.physio-pedia.com/Cardiovascular_Considerations_in_the_Older_Patient">pump blood less effectively</a>. This reduces the body’s ability to move heat to the skin to be transferred to the environment. </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><a href="http://dx.doi.org/10.1080/02640414.2015.1055291">Children</a> and <a href="https://www.nih.gov/news-events/news-releases/heat-related-health-dangers-older-adults-soar-during-summer">older adults</a> may also have less active sweat responses, which can reduce their potential to cool off through sweating. </p>
<p>Humans can tolerate most areas of the Earth, but extreme heat requires extra steps. If there’s a heat wave in your local forecast, seek out shade and begin to acclimatize by increasing your activity gradually when things get too hot. Drink more fluids to account for <a href="https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/water/art-20044256">increased fluid loss from sweat</a>, while also making sure <a href="https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/water/art-20044256">not to overhydrate</a>. And avoid outdoor activity during the hottest hours of the day if possible. </p>
<p>Whether heat waves are humid or dry, they are health threats that everyone should take seriously.</p><img src="https://counter.theconversation.com/content/163700/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>JohnEric W. Smith 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>Which is worse, dry heat or wet heat? Both, says an exercise physiologist.JohnEric W. Smith, Associate Professor of Exercise Physiology, Mississippi State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1591342021-05-28T02:01:25Z2021-05-28T02:01:25ZCurious Kids: if our bodies are happy at 37°C, why do we feel so unhappy when it’s too hot outside?<figure><img src="https://images.theconversation.com/files/402790/original/file-20210526-17-1rc9z1l.jpg?ixlib=rb-1.1.0&rect=1%2C4%2C997%2C660&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/boy-splash-water-hot-summer-day-212230843">from www.shutterstock.com</a></span></figcaption></figure><blockquote>
<p>How come the inside of your body is happy at 37 degrees but when the outside temperature is 37 degrees your body is very unhappy? — Patrick, aged 8. </p>
</blockquote>
<p>Great question, Patrick!</p>
<p>You’re right. Most people’s bodies are happiest when their inside temperature sits around a nice <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946399/">36.5-37.5°C</a>. These temperatures allow your body to work the best.</p>
<p>But your body temperature does go through small changes. It can be a bit lower when you’re <a href="https://jphysiolanthropol.biomedcentral.com/articles/10.1186/1880-6805-31-14">asleep</a>. It can also change during the day when you feel hungry, tired or cold. And when you’re sick, your <a href="https://youtu.be/BxgEoLmOACo">temperature can rise</a>. That’s when you might have a <a href="https://youtu.be/jRvxnpfCDSo">fever</a>.</p>
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<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-our-top-eyelashes-longer-than-our-bottom-eyelashes-132585">Curious Kids: why are our top eyelashes longer than our bottom eyelashes?</a>
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<h2>A happy body</h2>
<p>It’s really important to keep your body temperature at around 37°C otherwise you can overheat and get quite <a href="https://www.sciencedirect.com/science/article/pii/S1566070216300017">sick</a>.</p>
<p>To do this, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4854186/">muscles</a>, such as the ones in your arms and legs, tighten (or contract). This process generates, or “makes”, heat. Your blood then <a href="https://physoc.onlinelibrary.wiley.com/doi/10.1113/jphysiol.2002.035089">carries</a> this heat around your body.</p>
<p>But to stop your inside temperature getting too high, for example when you’re exercising on a hot day, your body needs to lose some of that heat.</p>
<figure class="align-center ">
<img alt="A young girl running in the park." src="https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402258/original/file-20210524-23-uw1q7o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Running generates a lot of heat, which our body needs to get rid of to the air around us.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Warm blood travels through <a href="https://www.ncbi.nlm.nih.gov/books/NBK507838/">blood vessels</a> close to your skin. This heat is then “lost” to the air around you.</p>
<p>If that’s not enough to cool you down, your body will also start sweating. This speeds up how you lose heat through your skin.</p>
<p>You usually feel the most comfortable when it’s around <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5961609/">18-24°C</a>. This seems to be a nice temperature that allows any extra heat to escape into the air. But it’s also not so cold that you <a href="https://open.oregonstate.education/aandp/chapter/24-6-energy-and-heat-balance/">need to move around</a> to keep warm.</p>
<h2>Phew, it’s stinking hot!</h2>
<p>Things that get in the way of losing heat through the skin can make you feel hot, such as wearing a woolly jumper in summer.</p>
<p>But you can also feel uncomfortable on a hot and humid day. That’s because the warm outside temperature makes it hard for you to lose heat from your skin to the air around you (because the air is already quite warm). And without a breeze, it’s even harder for the heat to be carried away.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-scabs-form-151586">Curious Kids: how do scabs form?</a>
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</em>
</p>
<hr>
<h2>How to keep cool</h2>
<p>If it’s very hot or humid, your body may find it hard to lose extra heat. So to keep cool on these days:</p>
<ul>
<li><p>drink water often. This not only keeps your body happy, it gives you extra liquid to turn into sweat. Sweating helps you lose heat</p></li>
<li><p>avoid direct sunlight, and try to keep to the shade or places with a cool breeze</p></li>
<li><p>wear thin clothing and natural fibres, which can allow a clear flow of air</p></li>
<li><p>wear light-coloured clothing, as this can keep you cooler than darker colours</p></li>
<li><p>avoid running, jumping or riding your bike in the middle of the day</p></li>
<li><p>on hot days, jump in a pool, or try to escape the heat by putting on the air-conditioning inside</p></li>
<li><p>sit in front of a fan. This breeze carries heat away from your skin and into the air around you, cooling you down quickly.</p></li>
</ul>
<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 curiouskids@theconversation.edu.au</em></p><img src="https://counter.theconversation.com/content/159134/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When the weather outside is very hot, it can make us feel really unhappy. Here’s why.Christian Moro, Associate Professor of Science & Medicine, Bond UniversityCharlotte Phelps, PhD Student, Bond UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1596842021-05-07T12:43:31Z2021-05-07T12:43:31ZWarming is clearly visible in new US ‘climate normal’ datasets<figure><img src="https://images.theconversation.com/files/399032/original/file-20210505-21-9lx20u.jpg?ixlib=rb-1.1.0&rect=41%2C0%2C6827%2C4582&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sunrise in Stone Harbor, New Jersey.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/summer-sunrise-royalty-free-image/1171419055">Robert D. Barnes via Getty Images</a></span></figcaption></figure><p>Anyone who listens to weather reports has heard meteorologists comment that yesterday’s temperature was 3 degrees above normal, or last month was much drier than normal. But what does “normal” mean in this context – and in a world in which the climate is changing? </p>
<p>The <a href="https://www.noaa.gov/">National Oceanic and Atmospheric Administration</a> has released updated “climate normals” – datasets that the agency produces every 10 years to give forecasters and the public baseline measurements of average temperature, rainfall and other conditions across the U.S. As the state climatologist and assistant state climatologist for Colorado, we work with this information all the time. Here’s what climate normals are, how they’ve changed, and how you can best make sense of them.</p>
<h2>What are the new normals?</h2>
<p>NOAA’s <a href="https://www.ncei.noaa.gov/news/noaa-delivers-new-us-climate-normals">National Centers for Environmental Information</a> released the new set of normals, covering 1991-2020, on May 4, 2021. Climatologists have been performing calculations on data from long-term observing stations around the country for a wide range of parameters, including high and low temperature, precipitation and snowfall. </p>
<p>The data also includes more detailed statistics, like the normal number of days below freezing or those with more than an inch of snowfall. NOAA puts data from individual stations onto a grid to enable the creation of useful maps for the entire country, even in places with relatively few observing stations. This provides a wealth of information for anyone interested in the climate of a specific area. </p>
<h2>Why are normals updated?</h2>
<p>The <a href="https://www.wmo.int/datastat/wmodata_en.html">World Meteorological Organization</a> sets international standards for climatological normals, defined as a 30-year periods that are regularly updated. The idea is to have global consistency for analysis. The 30-year normals also create a benchmark that represents recent climate conditions and serves as a reference for assessing current conditions. </p>
<p>Climate change highlights the need for regularly updating these normals. For the past 10 years, weather professionals have used the 1981-2010 climate normals as our reference. But we’ve <a href="https://www.climate.gov/news-features/understanding-climate/climate-change-and-1991-2020-us-climate-normals">observed above-average temperatures much more frequently</a> than below-average temperatures from 1991-2020 for much of the U.S. Updating the normals is a way to calibrate to our most recently observed climate. </p>
<p>And as the climate continues to change, the further away in time we get from the “normal” period, the less representative that period will become. Using a very long period of time, or not regularly updating the period, could lead to including observations that would be extremely unlikely in our climate today. </p>
<p>On the other hand, there are situations in which it makes sense to consider periods longer than 30 years – for example, to understand long-term changes to the climate or to monitor extremes.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/398197/original/file-20210430-13-ekujn8.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Most of the U.S. had more months in 1991-2020 that were warmer than the 1981-2010 average than months that were colder." src="https://images.theconversation.com/files/398197/original/file-20210430-13-ekujn8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/398197/original/file-20210430-13-ekujn8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/398197/original/file-20210430-13-ekujn8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/398197/original/file-20210430-13-ekujn8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/398197/original/file-20210430-13-ekujn8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=532&fit=crop&dpr=1 754w, https://images.theconversation.com/files/398197/original/file-20210430-13-ekujn8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=532&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/398197/original/file-20210430-13-ekujn8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=532&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Difference in the number of months that had above-normal vs. below-normal temperature by county for the period 1991-2020, with respect to the 1981-2010 normals. Areas in red and brown had far more months that were were warmer than normal.</span>
<span class="attribution"><span class="source">Becky Bolinger</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>The concept of ‘normal’ in weather and climate</h2>
<p>An old saying, <a href="https://quoteinvestigator.com/2012/06/24/climate-vs-weather/">often attributed to Mark Twain</a>, asserts that “climate is what you expect, and weather is what you get.” Calculations of normal climate conditions for particular locations show how this works.</p>
<p>For example, data from the long-term weather and climate observing station in Fort Collins, Colorado, where we work, shows that precipitation in summer (June, July and August) over the 30 years from 1991 to 2020 varied significantly from year to year. The lowest summer rainfall was 1.48 inches in 2002 and the highest was 14.79 inches in 1997. Most years, it’s somewhere between 3 and 5 inches.</p>
<p>But few years match the average value, just shy of 5 inches. So even though we call this the “normal” amount of rainfall, in most years the total is higher or lower – sometimes by quite a bit. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/398195/original/file-20210430-16-17n2m8a.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Average summer precipitation in Fort Collins, Colorado, can vary by a factor of 10 from year to year." src="https://images.theconversation.com/files/398195/original/file-20210430-16-17n2m8a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/398195/original/file-20210430-16-17n2m8a.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=471&fit=crop&dpr=1 600w, https://images.theconversation.com/files/398195/original/file-20210430-16-17n2m8a.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=471&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/398195/original/file-20210430-16-17n2m8a.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=471&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/398195/original/file-20210430-16-17n2m8a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=592&fit=crop&dpr=1 754w, https://images.theconversation.com/files/398195/original/file-20210430-16-17n2m8a.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=592&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/398195/original/file-20210430-16-17n2m8a.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=592&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Summer precipitation at Fort Collins, Colorado, for the years 1991-2020. The black circle indicates the 30-year average precipitation of 4.97 inches.</span>
<span class="attribution"><span class="source">Russ Schumacher and Becky Bolinger</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Looking at summer temperatures from the same station, let’s compare the previous 30-year period, 1981-2010, with the most recent 30-year period, 1991-2020. The data shows a shift toward higher temperatures between the two time periods. The normal summer temperature increased by nearly 1 degree, from 69.6 to 70.4 F. This “new normal” for the past 30 years reflects climate warming that has occurred both locally and globally. </p>
<figure>
<img src="https://cdn.theconversation.com/static_files/files/1562/test_transition.gif?1620247860">
<figcaption><span class="caption">Comparing the 1981-2010 and 1991-2020 normals for Fort Collins, Colorado, shows how summers there are warming. The black circle indicates the average value for each time period. Credit: Russ Schumacher and Becky Bolinger.</span></figcaption>
</figure>
<h2>What the new normals show</h2>
<p>The key change that’s reflected in shifting from the 1981-2010 normals to the new 1991-2020 set is dropping the 1980s and adding the 2010s. The climate has been warming, so the new normals show <a href="https://www.climate.gov/news-features/understanding-climate/climate-change-and-1991-2020-us-climate-normals">higher temperatures for most regions and most months of the year</a>. </p>
<p>Across the continental U.S., the temperature rose by about 0.5 F on average from the 1981-2010 to 1991-2020 period. The new average is 1.2 F warmer than that of the 20th century. A couple of exceptions are cooling observed in the spring over the Northern Great Plains and cooling over the Southeast and Mid-Atlantic in November. December shows the greatest amount of warming. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/398472/original/file-20210503-13-zktu9e.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Average temperatures were higher across most of the U.S. in 1991-2020 than in 1981-2010." src="https://images.theconversation.com/files/398472/original/file-20210503-13-zktu9e.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/398472/original/file-20210503-13-zktu9e.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=423&fit=crop&dpr=1 600w, https://images.theconversation.com/files/398472/original/file-20210503-13-zktu9e.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=423&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/398472/original/file-20210503-13-zktu9e.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=423&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/398472/original/file-20210503-13-zktu9e.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=532&fit=crop&dpr=1 754w, https://images.theconversation.com/files/398472/original/file-20210503-13-zktu9e.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=532&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/398472/original/file-20210503-13-zktu9e.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=532&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Difference between 1991-2020 average and 1981-2010 average temperatures for each month, with annual change in the bottom panel. Oranges and reds show where the new normals are warmer; blues and purples show where the new normals are cooler.</span>
<span class="attribution"><span class="source">Russ Schumacher and Becky Bolinger, data from NOAA</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Precipitation is more variable than temperature from year to year and decade to decade. As a result, the changes in normal precipitation represent a mix of effects from long-term climate change and natural variations. </p>
<p>Overall, the 2010s were very wet in much of the central and eastern U.S. and dry in the west, and the normals reflect that. Average annual rainfall in Houston increased by over an inch, to 55.6 inches per year, while at Phoenix, Arizona, it dropped from an already dry 8.02 inches to a parched 7.22 inches per year. </p>
<p>On a monthly basis, some of the most notable patterns to emerge are widespread drying in November, particularly over the Gulf states and along the Pacific Coast, and a wetter pattern over the eastern half of the country in April. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/398474/original/file-20210503-23-1wrjapr.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Most of the Central and Eastern U.S. was wetter in 1991-2020 than in 1981-2010, while most Western states were drier." src="https://images.theconversation.com/files/398474/original/file-20210503-23-1wrjapr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/398474/original/file-20210503-23-1wrjapr.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=428&fit=crop&dpr=1 600w, https://images.theconversation.com/files/398474/original/file-20210503-23-1wrjapr.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=428&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/398474/original/file-20210503-23-1wrjapr.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=428&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/398474/original/file-20210503-23-1wrjapr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=538&fit=crop&dpr=1 754w, https://images.theconversation.com/files/398474/original/file-20210503-23-1wrjapr.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=538&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/398474/original/file-20210503-23-1wrjapr.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=538&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Difference between 1991-2020 average and 1981-2010 average precipitation for each month, with the annual change in the bottom panel. Browns shading shows where the new normals are drier; green shading shows where the new normals are wetter.</span>
<span class="attribution"><span class="source">Russ Schumacher and Becky Bolinger, data from NOAA</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Shifting to new climate normals can have counterintuitive effects. For example, in the next few years there may be a better chance that you’ll see what are now described as cooler-than-normal temperatures in a given day or month. Using Fort Collins again as an example, before the update, a summer average temperature of 70 F would have been slightly warmer than normal. Now that same summer would go down as being slightly cooler than normal, even though it would still be warmer than around 100 of the 127 years in the history of that location. </p>
<p>Meteorologists and climatologists are already starting to incorporate these new normals into our work. But when you hear the term “normal,” keep in mind that it reflects a 30-year snapshot and represents a different reality today than it did 30, 60 or 100 years ago. </p>
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<p class="fine-print"><em><span>Russ Schumacher receives funding from the National Oceanic and Atmospheric Administration and the Colorado Agricultural Experiment Station for research on and monitoring of Colorado's weather and climate.</span></em></p><p class="fine-print"><em><span>Becky Bolinger receives funding from the National Oceanic and Atmospheric Administration and the Colorado Agricultural Experiment Station to monitor the climate of Colorado.</span></em></p>The US is shifting to a new set of climate ‘normals’ – data sets averaged over the past 30 years. But normal is a relative concept in a time of climate change.Russ Schumacher, Associate Professor of Atmospheric Science and Colorado State Climatologist, Colorado State UniversityBecky Bolinger, Assistant State Climatologist and Research Scientist in Atmospheric Science, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.