tag:theconversation.com,2011:/institutions/california-institute-of-technology-1463/articlesCalifornia Institute of Technology2024-01-03T13:43:07Ztag:theconversation.com,2011:article/2189012024-01-03T13:43:07Z2024-01-03T13:43:07ZCoast redwood trees are enduring, adaptable marvels in a warming world<figure><img src="https://images.theconversation.com/files/566348/original/file-20231218-29-3j3gwj.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5000%2C3742&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Looking up toward redwoods' crowns in Redwood Regional Park, Oakland, Calif.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/view-up-the-trunks-of-large-redwood-trees-in-a-grove-at-news-photo/1368056629">Gado/Getty Images</a></span></figcaption></figure><p>Coast redwoods – enormous, spectacular trees, some reaching nearly 400 feet, the tallest plants on the planet – thrive mostly in a narrow strip of land in the <a href="https://www.nps.gov/articles/000/coast-redwood.htm">Pacific Northwest of the United States</a>. Most of them grow from southern Oregon down into northern California, snugged up against the rugged Pacific coast. </p>
<p>They have grown by slowly responding to moisture and rich alluvial soil over millennia, combined with a genetic payload that pushes them to the upper limits of tree height. They are at risk – down to perhaps 70,000 individuals, falling from at least a half-million trees before humans arrived – but that’s not a new story, for we are all at risk. </p>
<p>Redwoods, like all trees, are engineered marvels. People don’t tend to think of natural things as “structures,” leaving that term to stand in for buildings, bridges and dams. But although trees were not built by humans, they didn’t just happen. They have come into their own through the inexorably turning wheels of natural selection and evolution, responding to environmental pressures, genetic drift and mutation. </p>
<p>They even have <a href="https://theconversation.com/redwood-trees-have-two-types-of-leaves-scientists-find-a-trait-that-could-help-them-survive-in-a-changing-climate-179812">two kinds of leaves</a> that help the trees adapt to both wet and dry conditions. They are born to change, just as humans are born to change.</p>
<p>Evolution is usually a very slow process, although sometimes it’s <a href="https://doi.org/10.1111/mec.15583">surprisingly quick</a>. New, intense pressures of a warming and changing climate are speeding things up. </p>
<p>I teach environmental humanities and history courses at Caltech and work as a <a href="https://scholar.google.com/citations?user=gXSGq_4AAAAJ&hl=en">senior curator</a> at <a href="https://huntington.org">The Huntington</a> – a research institution in nearby San Marino. It includes one of the world’s most renowned botanical gardens, comprising more than 130 acres and visited by over a million people annually. </p>
<p>Researchers and horticulturists at the botanical gardens are thinking about trees, and how to integrate them into larger landscapes, in new ways. Our approach to climate change resilience, our increased reliance on technologies like geographic information systems, and our new engagements with local communities all continue to shape our attitudes about trees. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/vsHrBTUHYJE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The nonprofit Archangel Tree Archive in Michigan is cloning iconic old-growth tree species, including redwoods and giant sequoias, to create a genetic archive and provide new trees for planting.</span></figcaption>
</figure>
<h2>Redwood communities</h2>
<p>There are differences as well as similarities between human-made edifices and trees. A structure or building typically is a sort of island unto itself, separate from its neighbors; in contrast, the coast redwood is an ecosystem with enormously broad consequences for other life forms.</p>
<p>Life is folded in and among the redwoods, below and within and about them. The trees are integrators, bringing together many life forms. Some of these life forms rely on the tree; others on occupants in and around the tree. </p>
<p>The coast redwood hosts so many different ecological interactions that it’s faintly ridiculous. Consider <a href="https://californiaherps.com/salamanders/pages/a.vagrans.html"><em>Aneides vagrans</em>, the wandering salamander</a>, which usually spends its entire life high in the canopy, but sometimes must jump out to escape predators. Without wings or gliding, it falls for as long as two full minutes, only to land perfectly unharmed on the ground.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/tbLFbyjVLYY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">High-speed video shows that ground-dwelling salamanders seem helpless during freefall in a vertical wind tunnel, while arboreal salamanders maneuver confidently. This suggests that the tree-dwellers have adapted to routine falls, and perhaps use falling as a way to quickly move around in tree canopies.</span></figcaption>
</figure>
<p>It took scientists dropping these creatures into a wind tunnel and <a href="http://dx.doi.org/10.1016/j.cub.2022.04.033">filming them with high-speed cameras</a> to understand why they didn’t end up as a wet splat on the forest floor. As it turns out, the salamander’s body shape does the work, with a torso that’s just sufficiently flattened, and large feet with long toes, that create just enough drag and balance for a soft landing.</p>
<p>Redwoods are so large that one reportedly was found to house a <a href="https://www.srs.fs.usda.gov/pubs/misc/ag_654/volume_1/picea/sitchensis.htm">Sitka spruce (<em>Picea sitchensis</em>)</a>, 8 feet tall, <a href="https://www.newyorker.com/magazine/2005/02/14/climbing-the-redwoods">growing far off the ground</a> within the larger tree. Redwoods also have served for millennia as nesting habitat for huge <a href="https://www.allaboutbirds.org/guide/California_Condor/overview#">California condors (<em>Gymnogyps californianus</em>)</a>, whose wingspan is nearly 10 feet. A big bird needs a big home. </p>
<p>There’s also a place for the tiny, living side by side with all of the largeness tucked in the complex, secret interstices of these trees. Nestled into extensive <a href="https://www.savetheredwoods.org/blog/fern-mats-create-entire-ecosystems-high-in-the-redwood-canopy/">mats of ferns</a> that grow high up in redwood canopies, researchers find <a href="https://www.savetheredwoods.org/wp-content/uploads/pdf_camann.pdf">aquatic crustaceans called copepods</a> that normally would live in larger bodies of water. No one knows how they got into the trees, but the fern mats trap enormous quantities of moisture from rain and fog, creating wetlands in the sky. </p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/CHJCb4xjSHM/?utm_source=ig_web_copy_link","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<h2>Enduring but not static</h2>
<p>Even species as enduring as coast redwoods are <a href="https://www.nps.gov/articles/000/coast-redwoods-v-climate-change.htm">affected by climate change</a>. Diminished moisture stresses the trees, making them grow with less vigor. New fire dangers put them at risk, and more frequent floods erode the big trees’ footing. But redwoods also are adapting.</p>
<p>A 2018 survey of nine large redwood trees found a total of 137 species of lichen growing on the trees, including several that were new to science. One was <a href="https://doi.org/10.3897/mycokeys.30.22271"><em>Xylopsora canopeorum</em></a>, whose specific name celebrates the canopy where it was discovered. </p>
<p>This lichen seems to be unique to the warmer and drier forests in California’s Sonoma and Santa Cruz counties, in the southern part of coast redwoods’ range. This is an exciting finding, for it provides evidence that new forms of life – ecosystem partners – may be evolving in sync with trees that are also evolving in the face of climate change. </p>
<p>Scientists are finding more new organic redwood partners every year. Since these trees are so networked and interconnected, the sum is greater than its parts and isn’t easy to quantify. </p>
<p>As I write in my forthcoming book, “<a href="https://www.simonandschuster.com/books/Twelve-Trees/Daniel-Lewis/9781982164058">Twelve Trees: The Deep Roots of Our Future</a>,” there’s something congregational about the redwoods in their groves, like “a group of worshippers, petitioners standing solemnly, upright before an even higher power than themselves: the calculus of wind, rain, sun, oxygen, carbon dioxide, and time.” Experiencing them stimulates one’s senses with scent, sight and sound, along with a tincture of the most essential ingredient of all – memory. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566355/original/file-20231218-29-c631u4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A dirt trail runs past redwoods toward a fogged-in vista." src="https://images.theconversation.com/files/566355/original/file-20231218-29-c631u4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566355/original/file-20231218-29-c631u4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566355/original/file-20231218-29-c631u4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566355/original/file-20231218-29-c631u4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566355/original/file-20231218-29-c631u4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566355/original/file-20231218-29-c631u4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566355/original/file-20231218-29-c631u4.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">Fog moves into the Purisima Creek Redwoods Open Space Preserve south of San Francisco. Redwoods obtain a large share of their water supply from fog.</span>
<span class="attribution"><a class="source" href="https://flic.kr/p/UbmKk4">Justin Dolske/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>New territory</h2>
<p>A pair of redwoods grow just outside my office at the Huntington, which is some 700 miles south of the coast redwood’s usual range. I’ve resisted giving names to this duo, although many giant redwoods have monikers like Adventure, Brutus, Nugget, Paradox and Atlas – most named by the scientists who first quantified their extreme heights.</p>
<p>The redwoods outside my window are perhaps 100 feet tall – puny by comparison to their northern brethren. But they are healthy, and will continue to be shaped by their immediate environments. They’ve traveled far to get to here, planted more than a half-century ago by an earlier generation of horticulturalists, and they’re thriving in their new home. We should all be so lucky.</p><img src="https://counter.theconversation.com/content/218901/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Lewis 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>Redwoods grow in networks that house unique communities of plants and animals high in the air. They offer life lessons about adapting over time.Daniel Lewis, Lecturer in History, California Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2024282023-04-12T12:10:59Z2023-04-12T12:10:59ZIn the turbulent Drake Passage, scientists find a rare window where carbon sinks quickly into the deep ocean<figure><img src="https://images.theconversation.com/files/520309/original/file-20230411-18-wrggfk.jpg?ixlib=rb-1.1.0&rect=274%2C263%2C3123%2C2296&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Drake Passage, seen from Antarctica, is one of the most turbulent ocean regions on Earth.</span> <span class="attribution"><span class="source">Lilian Dove</span></span></figcaption></figure><p>Looking out across the Southern Ocean near Antarctica, I can see whales and seabirds diving in and out of the water as they feed on sea life in the lower levels of the food web. At the base of this food web are tiny phytoplankton – algae that grow at the ocean surface, taking up carbon from the atmosphere through photosynthesis, just as plants on land do.</p>
<p>Because of their small size, phytoplankton are at the mercy of the ocean’s swirling motions. They are also so abundant that the green swirls are often visible from space. </p>
<p>Typically, phytoplankton remain near the surface of the ocean. Some may slowly sink to depth because of gravity. But in the turbulent Drake Passage, a 520-mile-wide (850 km) bottleneck between Antarctica and South America, something unusual is happening, and it has an impact on how the ocean takes carbon dioxide – the main driver of global warming – out of the atmosphere.</p>
<figure class="align-center ">
<img alt="A satellite image shows green swirls off the South American coast." src="https://images.theconversation.com/files/520127/original/file-20230411-24-4z7ae3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520127/original/file-20230411-24-4z7ae3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=511&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520127/original/file-20230411-24-4z7ae3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=511&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520127/original/file-20230411-24-4z7ae3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=511&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520127/original/file-20230411-24-4z7ae3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=643&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520127/original/file-20230411-24-4z7ae3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=643&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520127/original/file-20230411-24-4z7ae3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=643&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A satellite image captures a green phytoplankton bloom off the coast of Argentina. The Drake Passage is at the country’s southern end.</span>
<span class="attribution"><a class="source" href="https://oceancolor.gsfc.nasa.gov/gallery/612/">NASA Aqua/MODIS</a></span>
</figcaption>
</figure>
<h2>The Drake Passage</h2>
<p>The Drake Passage is notorious for its violent seas, with waves that can top 40 feet (12 meters) and <a href="https://doi.org/10.1038/s43247-022-00644-x">powerful converging currents</a>, some flowing as fast as <a href="https://doi.org/10.1002/2016GL070319">150 million cubic meters per second</a>. Cold water from the Southern Ocean and warmer water from the north collide here, spinning off <a href="https://doi.org/10.1175/JPO-D-18-0150.1">powerful and energetic eddies</a>.</p>
<p>New scientific research I am involved in <a href="https://scholar.google.com/citations?user=AlCIFFYAAAAJ&hl=en">as an oceanographer</a> now shows how the Drake Passage and a few other specific areas of the Southern Ocean play an outsize role in how the oceans lock up carbon from the atmosphere.</p>
<figure class="align-center ">
<img alt="A map shows the underwater ridges and continental shelves." src="https://images.theconversation.com/files/520123/original/file-20230411-22-3zv2hv.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520123/original/file-20230411-22-3zv2hv.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=559&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520123/original/file-20230411-22-3zv2hv.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=559&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520123/original/file-20230411-22-3zv2hv.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=559&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520123/original/file-20230411-22-3zv2hv.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=702&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520123/original/file-20230411-22-3zv2hv.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=702&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520123/original/file-20230411-22-3zv2hv.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=702&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A topographic map of the Drake Passage between South America and Antarctica.</span>
<span class="attribution"><a class="source" href="https://www.ncei.noaa.gov/products/etopo-global-relief-model.">NCEI/NOAA</a></span>
</figcaption>
</figure>
<p>That process is crucial for our understanding of the climate. The global ocean is a massive reservoir of carbon, holding over <a href="https://science.nasa.gov/earth-science/oceanography/ocean-earth-system/ocean-carbon-cycle">50 times as much carbon</a> as the atmosphere. However, it is only when water carrying carbon <a href="https://doi.org/10.1029/2020GB006790">gets to the deep ocean</a> that carbon can be stored for long periods – up to centuries or millennia.</p>
<p>Photosynthetic phytoplankton are at the heart of that exchange. And in the Drake Passage, my colleagues and I have found that undersea mountains are stirring things up.</p>
<h2>The role of ocean layers</h2>
<p>The ocean can be visualized as having layers. With constant surface waves and winds, the upper layer is always stirring around, mixing waters. It’s like mixing milk into your morning coffee. This stirring <a href="https://doi.org/10.1038/s41467-020-18203-3">mixes in solar heat and gases</a>, such as carbon dioxide, taken up from the atmosphere.</p>
<p>Water density generally increases as the waters get deeper and colder and saltier. That forms density layers that are typically flat. Since water prefers to keep its density constant, it mostly moves horizontally and doesn’t easily move between the surface and deep ocean.</p>
<figure class="align-center ">
<img alt="A graphic shows the typical ocean density layers, with phytoplankton in the upper layers." src="https://images.theconversation.com/files/520160/original/file-20230411-24-1kv12p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520160/original/file-20230411-24-1kv12p.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=485&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520160/original/file-20230411-24-1kv12p.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=485&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520160/original/file-20230411-24-1kv12p.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=485&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520160/original/file-20230411-24-1kv12p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=610&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520160/original/file-20230411-24-1kv12p.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=610&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520160/original/file-20230411-24-1kv12p.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=610&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In most of the ocean, water stays within a density layer and doesn’t mix with colder, saltier water.</span>
<span class="attribution"><span class="source">Lilian Dove</span></span>
</figcaption>
</figure>
<p>Yet despite this physical barrier, water testing shows that carbon dioxide produced by human activities is making its way into the deep ocean. One way is through chemistry: Carbon dioxide dissolves in water, creating carbonic acid. Living creatures in the ocean are another.</p>
<h2>A view into the Drake Passage</h2>
<p>Oceanographers have long pointed to the north Atlantic Ocean and the Southern Ocean as places <a href="https://www.jstor.org/stable/24862019">where surface waters are moved to depth</a>, taking large volumes of carbon with them. However, recent work has shown that this process may actually be dominated by only a few areas – <a href="https://doi.org/10.1029/2022GL102550">including the Drake Passage</a>.</p>
<p>Despite its being one of the most famous stretches of the ocean, scientists have only recently been able to observe this window in action.</p>
<p>The main flow of the Drake Passage is created by the effect of strong westerly winds across the Southern Ocean. Scientists have found that the westerly winds create a slope in the water density, with dense waters shallower closer to Antarctica, where colder melt water caps the surface, but sloping deeper into the ocean farther north toward South America.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/520164/original/file-20230411-26-mi0289.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Side-by-side graphics show (1) the typical ocean density layers and (2) the sloped density layers in the Drake Passage." src="https://images.theconversation.com/files/520164/original/file-20230411-26-mi0289.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520164/original/file-20230411-26-mi0289.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520164/original/file-20230411-26-mi0289.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520164/original/file-20230411-26-mi0289.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520164/original/file-20230411-26-mi0289.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520164/original/file-20230411-26-mi0289.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520164/original/file-20230411-26-mi0289.png?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">Unlike in most of the ocean, density layers in the Drake Passage slope downward, allowing phytoplankton to mix downward as well as sideways.</span>
<span class="attribution"><span class="source">Lilian Dove</span></span>
</figcaption>
</figure>
<p>With advances in <a href="https://doi.org/10.1029/2022GL102550">autonomous underwater robots</a> and computer modeling, we have been able to show how the flow of the Southern Ocean interacts with an underwater mountain in the Drake Passage. This underwater interaction <a href="https://doi.org/10.1029/2021GL097574">mixes up the ocean</a>, enhancing that coffeelike stirring process.</p>
<p>The stirring along the sloped density levels provides a pathway for water from the upper layer of the ocean to move into the depths. And phytoplankton at the surface ocean are carried along with this stirring, moving to depth much faster than they would by gravitational sinking alone.</p>
<p>In a less energetic region, these phytoplankton would die and respire their carbon back to the atmosphere or slowly sink. However, at the Drake Passage, phytoplankton can be swept to depth before this happens, meaning the carbon they’ve taken up from the atmosphere is sequestered in the deep ocean. Carbon dissolved and stored in the deep ocean may also vent out in these locations. </p>
<figure class="align-center ">
<img alt="Three people bundled up in winter gear work on a large seagoing drone." src="https://images.theconversation.com/files/520122/original/file-20230411-18-thnam3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520122/original/file-20230411-18-thnam3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520122/original/file-20230411-18-thnam3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520122/original/file-20230411-18-thnam3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520122/original/file-20230411-18-thnam3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520122/original/file-20230411-18-thnam3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520122/original/file-20230411-18-thnam3.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">Author Lilian Dove, at right, works with oceanographer Isa Rosso and marine technician Richard Thompson to prepare an oceangoing autonomous vehicle to take measurements in the Southern Ocean.</span>
<span class="attribution"><span class="source">Linnah Neidel</span></span>
</figcaption>
</figure>
<p>Scientists have estimated that the deepest ocean waters directly interact with the atmosphere through only about <a href="https://doi.org/10.1038/308621a0">5% of the ocean’s surface area</a>. This is one of those special places.</p>
<p>Investigating the Drake Passage and other oceanographic windows allows science to home in on better understanding climate change and the workings of our blue planet.</p><img src="https://counter.theconversation.com/content/202428/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lilian Dove receives funding from the National Science Foundation and Resnick Sustainability Institute.</span></em></p>Working with underwater robots, scientists show how deep sea mountains and fast currents between Antarctica and South America play a crucial role in stabilizing the climate.Lilian (Lily) Dove, Ph.D. Candidate in Oceanography, California Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1855092022-08-10T20:11:46Z2022-08-10T20:11:46ZIce shelves hold back Antarctica’s glaciers from adding to sea levels – but they’re crumbling<figure><img src="https://images.theconversation.com/files/477964/original/file-20220807-83452-8qekbh.png?ixlib=rb-1.1.0&rect=0%2C3%2C1331%2C882&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Esmee van Wijk</span>, <span class="license">Author provided</span></span></figcaption></figure><p>As Antarctica’s slow rivers of ice hit the sea, they float, forming ice shelves. These shelves extend the glaciers into the ocean until they calve into icebergs. </p>
<p>But they also play a crucial role in maintaining the world as we know it, by acting as a brake on how fast the glaciers can flow into the ocean. If they weren’t there, the glaciers would flow faster into the sea and melt, causing sea levels to rise.<br>
Unfortunately, Antarctica’s ice shelves are not what they were. In research <a href="https://www.nature.com/articles/s41586-022-05037-w">published today in <em>Nature</em></a>, we show these ice shelves have significantly reduced in area over the last 25 years due to more and more icebergs breaking off. Overall, the net loss of ice is about 6,000 billion tonnes since 1997. </p>
<p>Previous estimates of ice shelf loss come from satellite measurements, which captured ice shelves gradually thinning in recent years. We tracked how much extra ice had been lost as icebergs calve away from the retreating edge of the continent. We found Antarctica’s ice shelves have lost twice as much mass as previous studies suggested. </p>
<p>Ice shelves are now weaker than at any time since at least the 1990s. This has led Antarctica’s glaciers to begin adding more water to the oceans, and more quickly. To date, much of the concern about the cryosphere – the world’s frozen parts – has focused on the fast-melting Arctic sea ice. But as climate change intensifies, Antarctica will begin melting in earnest, contributing more to sea level rise. </p>
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<a href="https://images.theconversation.com/files/477962/original/file-20220807-75820-gwa1qd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="east antarctic glacier" src="https://images.theconversation.com/files/477962/original/file-20220807-75820-gwa1qd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/477962/original/file-20220807-75820-gwa1qd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/477962/original/file-20220807-75820-gwa1qd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/477962/original/file-20220807-75820-gwa1qd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/477962/original/file-20220807-75820-gwa1qd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/477962/original/file-20220807-75820-gwa1qd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/477962/original/file-20220807-75820-gwa1qd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sørsdal Glacier in East Antarctica, where meltwater lakes have been appearing.</span>
<span class="attribution"><span class="source">Sarah Thompson</span>, <span class="license">Author provided</span></span>
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</figure>
<h2>What we measured</h2>
<p>We built numerical models to figure out what ice shelf thinning and loss of area mean for the ability of ice shelves to resist new ice being pushed in from upstream glaciers. </p>
<p>Our work shows the drop in ice shelf area has led to more ice flowing into the sea since 2007, as calving has weakened ice shelves and allowed some of the world’s largest glaciers to accelerate. </p>
<p>We found the Pine Island Glacier and the so-called <a href="https://theconversation.com/ice-world-antarcticas-riskiest-glacier-is-under-assault-from-below-and-losing-its-grip-178828">“Doomsday” Thwaites Glacier</a> – which could destabilise the entire West Antarctic ice sheet if it melts – are highly sensitive to calving, and are already increasing their contribution to sea level rise as their protective ice shelves crumbled. </p>
<p>Iceberg calving is a natural process. In any climate, we expect to see massive flat-top icebergs periodically break off and float away. So while no single calving event should be taken as <a href="https://www.theguardian.com/science/2017/jun/23/melting-and-cracking-is-antarctica-falling-apart-climate-change">cause for alarm</a>, the long term trend is concerning. We found a majority of Antarctica’s ice shelves have lost mass since the late 1990s.</p>
<p>Why are Antarctic ice shelves shrinking? There’s no single answer. Some ice shelves such as the Wilkins Ice Shelf have already seen catastrophic disintegration, while others are retreating slowly and some are even advancing. But overall, these ice shelves are shrinking. </p>
<p>We know one cause of <a href="https://www.pnas.org/doi/10.1073/pnas.1415137112">ice shelf retreat</a> is the thinning of ice shelves, which is largely caused by relatively warm seawater <a href="https://theconversation.com/troubling-new-research-shows-warm-waters-rushing-towards-the-worlds-biggest-ice-sheet-in-antarctica-187483">eroding the base</a> of these shelves. </p>
<p>We also know iceberg calving increases whenever Antarctica’s protective <a href="https://www.nature.com/articles/s41586-018-0212-1">ring of sea ice weakens</a>. This year, Antarctica saw the lowest sea ice extent <a href="https://www.nature.com/articles/d41586-022-00550-4">ever recorded</a> since measurements began in the 1970s. We’ve also seen entire ice shelves collapse when warmer air temperatures create surface meltwater that <a href="https://www.nature.com/articles/s41586-020-2627-8">can cut through</a> hundreds of metres of ice shelf. </p>
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Read more:
<a href="https://theconversation.com/warmer-summers-threaten-antarcticas-giant-ice-shelves-because-of-the-lakes-they-create-180989">Warmer summers threaten Antarctica’s giant ice shelves because of the lakes they create</a>
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<h2>Four giant ice shelves are still in good shape</h2>
<p>Antarctica’s four largest ice shelves are the Ross, Ronne, Filchner, and Amery. These vast floating sheets of ice tend to calve off giant icebergs once every few decades. </p>
<p>All four are on track for major calving events in the next 10 to 15 years, and none would normally be cause for alarm. The problem is calving will come on top of steady ice shelf loss. When the major ice shelves do calve off huge icebergs, they will leave the Antarctic Ice Sheet smaller than we’ve ever seen it. </p>
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<figcaption>
<span class="caption">Enormous tabular icebergs like this one are often formed by calving from ice shelves. This iceberg near the coast of West Antarctica is seen from a window of a NASA Operation IceBridge airplane in 2016.</span>
<span class="attribution"><span class="source">Getty</span></span>
</figcaption>
</figure>
<p>But while we’re not yet seeing any abnormal behaviour in these four major ice shelves, the overlooked losses from all the smaller ice shelves fringing the continent are adding up. Earlier this year, one smaller ice shelf <a href="https://earthobservatory.nasa.gov/images/149640/ice-shelf-collapse-in-east-antarctica">collapsed entirely</a>. </p>
<p>The most troubling changes of the past few decades are less photogenic than sudden ice shelf collapse. Bit-by-bit, West Antarctica’s Thwaites ice shelf has retreated. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-a-near-perfect-rectangular-iceberg-formed-105655">How a near-perfect rectangular iceberg formed</a>
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</p>
<hr>
<p>Each calving event has left the ice shelf weaker and allowed the Thwaites Glacier behind it – the size of the state of Victoria – to flow faster into the ocean. While the Thwaites ice shelf is relatively small, it is vital. Until now, it has acted like a plug. If it keeps retreating, it could potentially destabilise the entire West Antarctic ice sheet and unlock several metres of sea level rise.</p>
<h2>Climate change is the big picture</h2>
<p>Our warming atmosphere and ocean are the root cause. Given the long lag time between greenhouse gases trapping heat and actual warming, it stands to reason that what we’re seeing in Antarctica right now is at least partly a response to warming gases dumped into the atmosphere <a href="http://dx.doi.org/10.1088/1748-9326/9/12/124002">decades or even a century ago</a>. That means we’re already locked into more ice shelf retreat, as emissions have continued rising. </p>
<p>Antarctica holds around 30 million cubic kilometres of ice, a truly enormous figure. That represents around 90% of the world’s surface fresh water. If it all melted, seas would rise almost 60 metres. Humanity’s decisions will shape what Antarctica will look like in decades to come, and how much ice will remain.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/ice-world-antarcticas-riskiest-glacier-is-under-assault-from-below-and-losing-its-grip-178828">Ice world: Antarctica's riskiest glacier is under assault from below and losing its grip</a>
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<img src="https://counter.theconversation.com/content/185509/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexander Fraser receives funding from the Australian Antarctic Program Partnership and the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Chad Greene receives funding from NASA. </span></em></p>Antarctica’s ice shelves have helped insulate it from dangerous levels of ice loss. But this is changing.Alexander Fraser, Senior Researcher in Antarctic Remote Sensing, University of TasmaniaChad Greene, Scientist at NASA's Jet Propulsion Laboratory, California Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1876072022-08-04T12:22:28Z2022-08-04T12:22:28ZIlluminating the brain one neuron and synapse at a time – 5 essential reads about how researchers are using new tools to map its structure and function<figure><img src="https://images.theconversation.com/files/475765/original/file-20220725-30588-3lzyhd.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1960%2C1527&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The U.S. BRAIN Initiative seeks to elucidate the connection between brain structure and function.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/computer-artwork-of-human-brain-profile-royalty-free-illustration/85757401">Science Photo Library - PASIEKA/Brand X Pictures via Getty Images</a></span></figcaption></figure><p>Scientists know both a lot and very little about the brain. With <a href="https://doi.org/10.48550/arXiv.1906.01703">billions of neurons and trillions of connections</a> among them, and the experimental limitations of examining the seat of consciousness and bodily function, studying the human brain is a technical, theoretical and ethical challenge. And one of the biggest challenges is perhaps one of the most fundamental – seeing what it looks like in action.</p>
<p>The U.S. <a href="https://braininitiative.nih.gov">Brain Research Through Advancing Innovative Neurotechnologies (BRAIN) Initiative</a> is a collaboration among the National Institutes of Health, Defense Advanced Research Projects Agency, National Science Foundation, Food and Drug Administration and Intelligence Advanced Research Projects Activity and others. Since its inception in 2013, <a href="https://braininitiative.nih.gov">its goal</a> has been to develop and use new technologies to examine how each neuron and neural circuit comes together to “record, process, utilize, store, and retrieve vast quantities of information, all at the speed of thought.”</p>
<p>Just as <a href="https://theconversation.com/genomic-sequencing-heres-how-researchers-identify-omicron-and-other-covid-19-variants-172935">genomic sequencing</a> enabled the creation of a <a href="https://theconversation.com/the-human-genome-project-pieced-together-only-92-of-the-dna-now-scientists-have-finally-filled-in-the-remaining-8-176138">comprehensive map of the human genome</a>, tools that elucidate the connection between brain structure and function could help researchers answer long-standing questions about how the brain works, both in sickness and in health.</p>
<p>These five stories from our archives cover research that has been funded by or advances the goals of the BRAIN Initiative, detailing a slice of what’s next in neuroscience.</p>
<h2>1. Mapping the brain</h2>
<p>Attempts to map the structure of the brain date back to <a href="https://web.stanford.edu/class/history13/earlysciencelab/body/brainpages/brain.html">antiquity</a>, when philosophers and scholars had only the unaided eye to map anatomy to function. New <a href="https://embryo.asu.edu/pages/golgi-staining-technique">visualization techniques</a> in the 20th century led to the discovery that, just like all the other organs of the body, the brain is composed of individual cells – <a href="https://doi.org/10.1016/j.cub.2006.02.053">neurons</a>.</p>
<p>Now, <a href="https://theconversation.com/mapping-how-the-100-billion-cells-in-the-brain-all-fit-together-is-the-brave-new-world-of-neuroscience-170182">further advances in microscopy</a> that make use of artificial intelligence and genomics have allowed scientists not just to see each individual neuron in the entire brain, but also to identify the connections among them and begin to ascertain their function. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/432261/original/file-20211116-25-1vtphzf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Stitched high-resolution microscopy image of mouse brain." src="https://images.theconversation.com/files/432261/original/file-20211116-25-1vtphzf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/432261/original/file-20211116-25-1vtphzf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/432261/original/file-20211116-25-1vtphzf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/432261/original/file-20211116-25-1vtphzf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/432261/original/file-20211116-25-1vtphzf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/432261/original/file-20211116-25-1vtphzf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/432261/original/file-20211116-25-1vtphzf.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">Zooming in on this high-resolution image of a mouse brain reveals rectangular lines where individual image tiles were stitched together, each colored dot representing a specific cell type.</span>
<span class="attribution"><a class="source" href="http://kimlab.io">Yongsoo Kim</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Neuroscientist <a href="https://scholar.google.com/citations?user=WOQx1ksAAAAJ&hl=en">Yongsoo Kim</a> of Penn State likened this method to a photo mosaic, piecing together areas of the brain that haven’t been charted before. “It’s like building a Google map of the brain,” wrote Kim. “By combining millions of individual street photos, you can zoom in to see each street corner and zoom out to see an entire city.” Creating these high-resolution maps, he wrote, could help scientists develop new theories on how the brain works and lead to better treatments for brain disorders like dementia.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/mapping-how-the-100-billion-cells-in-the-brain-all-fit-together-is-the-brave-new-world-of-neuroscience-170182">Mapping how the 100 billion cells in the brain all fit together is the brave new world of neuroscience</a>
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<h2>2. Brain folds and wrinkles</h2>
<p>Another fundamental question researchers have been puzzling over is how the brain develops the bumps and grooves that riddle its surface. Until roughly the <a href="https://doi.org/10.1093%2Fcercor%2Fbhr053">second trimester</a> of fetal development, the human brain is completely smooth.</p>
<p>Scientists have proposed a number of theories on the mechanics of brain folding. One of them, <a href="https://www.jstor.org/stable/1740783">differential tangential growth</a>, posits that folds form because of a mismatch in growth rates between the outer and inner layers of the brain. To ease the forces compressing the outer layer and restore structural stability, the layers buckle and fold.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/WBWJBFRnqwY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Harvard researchers modeled how folding reduces instability caused by differential growth rates in the brain.</span></figcaption>
</figure>
<p>Biomechanical engineer <a href="https://scholar.google.com/citations?user=ukOZ0BAAAAAJ&hl=en">Mir Jalil Razavi</a> and computer scientist <a href="https://scholar.google.com/citations?user=r6DIjzUAAAAJ&hl=en">Weiying Dai</a> of Binghamton University <a href="https://theconversation.com/brain-wrinkles-and-folds-matter-researchers-are-studying-the-mechanics-of-how-they-form-170194">created models</a> to clarify this theory. They identified other factors that may also be at play, like the number of axons – the part of the neuron that transmits electrical signals – in a particular area. “Our brain models provide a potential explanation for why brains may form abnormally during development, highlighting the important role that the brain’s structure plays in its proper functioning,” they wrote.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/brain-wrinkles-and-folds-matter-researchers-are-studying-the-mechanics-of-how-they-form-170194">Brain wrinkles and folds matter – researchers are studying the mechanics of how they form</a>
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<h2>3. Where memories are stored</h2>
<p>Just like the RAM in a computer, memories take up physical space in the brain. Researchers have hypothesized that memories may be stored by <a href="https://doi.org/10.1016/0166-2236(94)90101-5">rearranging the connections, or synapses</a>, among neurons. While this theory has largely been confirmed by observing <a href="https://doi.org/10.1038/37601">changes in the electrical signals</a> neurons produce after memory formation, what triggers these changes has been unclear.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/440053/original/file-20220110-27-14nulz7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Image of magenta-colored neurons in a live fish brain, with the synapses colored in green" src="https://images.theconversation.com/files/440053/original/file-20220110-27-14nulz7.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/440053/original/file-20220110-27-14nulz7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=766&fit=crop&dpr=1 600w, https://images.theconversation.com/files/440053/original/file-20220110-27-14nulz7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=766&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/440053/original/file-20220110-27-14nulz7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=766&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/440053/original/file-20220110-27-14nulz7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=963&fit=crop&dpr=1 754w, https://images.theconversation.com/files/440053/original/file-20220110-27-14nulz7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=963&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/440053/original/file-20220110-27-14nulz7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=963&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Neurons in a live fish brain, with synapses colored green.</span>
<span class="attribution"><span class="source">Zhuowei Du and Don B. Arnold</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Biomedical engineer <a href="https://scholar.google.com/citations?user=z040dHgAAAAJ&hl=en">Don Arnold</a> of the University of Southern California and his colleagues took a mapping approach. They <a href="https://theconversation.com/where-are-memories-stored-in-the-brain-new-research-suggests-they-may-be-in-the-connections-between-your-brain-cells-174578">compared 3D maps of zebrafish synapses</a> before and after memory formation – namely, learning to associate a light with an unpleasant stimulus. They found that one brain region gained synapses while another’s were destroyed, indicating that associative memories may be a result of the formation and loss of connections among neurons.</p>
<p>These findings imply that it might one day be possible to treat conditions like PTSD by physically erasing the associative memory linking a harmless trigger with a traumatic experience. More research is needed, and there are obvious ethical considerations to address. “Nevertheless,” Arnold wrote, “it’s tempting to imagine a distant future in which synaptic surgery could remove bad memories.”</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/where-are-memories-stored-in-the-brain-new-research-suggests-they-may-be-in-the-connections-between-your-brain-cells-174578">Where are memories stored in the brain? New research suggests they may be in the connections between your brain cells</a>
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<h2>4. Seizures hijack memory pathways</h2>
<p><a href="https://www.epilepsy.com/what-is-epilepsy/understanding-seizures">Seizures</a> are sudden surges of electrical activity in the brain. People who experience temporal lobe seizures are sometimes unable to remember what happened immediately prior. This may be due to disruptions to the circuitry in the hippocampus, the part of the temporal lobe key to memory consolidation.</p>
<p>Neurology researchers <a href="https://scholar.google.com/citations?user=bjrXv58AAAAJ&hl=en&oi=ao">Anastasia Brodovskaya</a> and <a href="https://scholar.google.com/citations?user=nMb-pTcAAAAJ&hl=en">Jaideep Kapur</a> of the University of Virginia hypothesized that seizures can cause memory loss by <a href="https://theconversation.com/seizures-can-cause-memory-loss-and-brain-mapping-research-suggests-one-reason-why-172280">using the same pathways</a> the brain uses to process memories. They mapped the neurons of mice learning to navigate a maze and during induced seizures, finding that both cases activated the same brain circuits.</p>
<p>“Because they use the same brain pathways, seizures can disrupt the memory consolidation process by taking over the circuit,” they wrote. “This meant that seizures can hijack the memory pathways and cause amnesia.”</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/seizures-can-cause-memory-loss-and-brain-mapping-research-suggests-one-reason-why-172280">Seizures can cause memory loss, and brain-mapping research suggests one reason why</a>
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<h2>5. What the nose knows</h2>
<p>What the eye can’t see, the nose can for many organisms. From dogs to mosquitoes, many animals behave in ways that allow them to detect and pursue an odor long before its source comes into view.</p>
<p>Scientists <a href="https://scholar.google.com/citations?user=wn_f7y0AAAAJ&hl=en">John Crimaldi</a>, <a href="https://scholar.google.com/citations?user=JEi-fdoAAAAJ&hl=en">Brian Smith</a>, <a href="https://www.bbe.caltech.edu/people/elizabeth-j-hong">Elizabeth Hong</a> and <a href="https://scholar.google.com/citations?user=GpkJjVUAAAAJ&hl=en">Nathan Urban</a> of the <a href="https://www.odor2action.org/">Odor2Action</a> research network use technology to study olfaction, or sense of smell. They <a href="https://theconversation.com/from-odor-to-action-how-smells-are-processed-in-the-brain-and-influence-behavior-173811">trace how the shape of an odor plume</a> informs how it will be detected, how those odor molecules are translated into electrical signals in the brain, and how these electrical signals are reformatted into useful information that influence behavior.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/MyHR6a-zJM0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video from the Wachowiak Lab at the University of Utah shows the activity of the olfactory bulb in a mouse brain. Each odor the mouse is exposed to makes different combinations of neurons light up.</span></figcaption>
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<p>A better understanding of the olfactory system, they wrote, can lead to the development of <a href="https://doi.org/10.1177%2F0278364908095118">electronic noses</a> that make searching for chemical weapons and disaster victims safer for people and animals. They also believe that examining the olfactory system can help advance study of the brain. “Its relative simplicity is what allows scientists like us to study it from end to end and learn how the brain works as a whole,” they wrote.</p>
<p>While a grand unified theory of the brain still remains elusive, new tools and techniques are helping researchers excavate its hidden depths. As Crimaldi and his team put it, “An exciting future in scientific and medical development, we believe, is right under our noses.”</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/from-odor-to-action-how-smells-are-processed-in-the-brain-and-influence-behavior-173811">From odor to action – how smells are processed in the brain and influence behavior</a>
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<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/187607/count.gif" alt="The Conversation" width="1" height="1" />
From figuring out where memories are stored to how sensory information translates to behavior, new technologies are helping neuroscientists better understand how the brain works.Vivian Lam, Associate Health and Biomedicine EditorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1738112022-01-25T13:27:01Z2022-01-25T13:27:01ZFrom odor to action – how smells are processed in the brain and influence behavior<figure><img src="https://images.theconversation.com/files/441580/original/file-20220119-23-1y38fqx.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2734%2C1342&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The compact olfactory system provides a more accessible way to study the brain as a whole.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-a-dogs-nose-royalty-free-image/603137803">Esther Kok/EyeEm via Getty Images</a></span></figcaption></figure><p>A dog raises its nose in the air before chasing after a scent. A mosquito zigzags back and forth before it lands on your arm for its next meal. What these behaviors have in common is that they help these animals “see” their world through their noses.</p>
<p>While humans primarily use their vision to navigate their environment, the vast majority of organisms on Earth communicate and experience the world through <a href="https://doi.org/10.1016/j.neuron.2005.10.022">olfaction</a> – their sense of smell.</p>
<p><a href="https://scholar.google.com/citations?user=wn_f7y0AAAAJ&hl=en">We</a> <a href="https://scholar.google.com/citations?user=JEi-fdoAAAAJ&hl=en">are</a> <a href="https://www.bbe.caltech.edu/people/elizabeth-j-hong">members</a> <a href="https://scholar.google.com/citations?user=GpkJjVUAAAAJ&hl=en">of</a> <a href="https://www.odor2action.org">Odor2Action</a>, an international network of over 50 scientists and students using olfaction to study brain function in animals. Our goal is to understand a fundamental question in neuroscience: How do animal brains translate information from their environments to changes in their behaviors?</p>
<p>Here, we trace the interconnections between smells and behaviors – looking at how behavior influences odor detection, how the brain processes sensory information from smells and how this information triggers new behaviors.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/58U52lDTuvk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Visualizing what smells look like helps researchers design technologies that detect odors as well as a dog can.</span></figcaption>
</figure>
<h2>Detecting odors in the environment</h2>
<p>When the odor of a flower is released into the air, it takes the shape of a wind-borne <a href="https://doi.org/10.1007/s003480000263">cloud of molecules called a plume</a>. It encounters physical obstacles and temperature differences as it flows through space. These interactions create turbulence that splits the odor plume into thin threads that spread out as the scent moves away from its source. These filaments eventually reach an animal’s nose or an insect’s antenna.</p>
<p>Odors that are broken up into filaments present a challenge to animals using them to find food or mates or avoid threats. It becomes difficult to predict precisely where the odor is coming from. Is the source directly ahead, to the left or right, above or below?</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/jQaHbHMrqmE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video by the Crimaldi Laboratory of the University of Colorado Boulder shows an odor plume developing behind a moving source over time. The source moves up and down from the left side, and the odor flows from left to right.</span></figcaption>
</figure>
<p>To work around this, animals have evolved what are called <a href="https://doi.org/10.1007/s10827-021-00798-1">active sensing</a> behaviors that improve their ability to detect and find odors in the environment.</p>
<p>When a fly detects the smell of fruit or a mosquito detects carbon dioxide from a possible host, for example, both insects first move upwind to get closer to the odor of the food source. They then move in a meandering, back-and-forth motion called casting to find more odor threads before surging upwind again. If they lose the scent, they’ll start casting again until they find the scent. Larger animals, such as mice and dogs, also alternate between more directed movements and more exploratory searching actions. </p>
<p>Animals also move their noses and antennae to improve the chances that they’ll encounter an odor. This is why dogs raise their noses in the air to increase the amount of odor they can sniff, and why insects move their antennae to stir up and penetrate the air to make better contact with odor molecules. </p>
<p>Once information from odors tell the animal that they’re close to the source, visual searching then comes into play.</p>
<h2>Making sense of odors</h2>
<p>When an animal comes into contact with an odor plume, it detects the presence of these odor molecules through tiny proteins called <a href="https://www.nobelprize.org/prizes/medicine/2004/summary/">odorant receptors</a>. These receptors are embedded in the sensory neurons lining its nasal cavity or antennae.</p>
<p>Each sensory neuron contains only one type of odorant receptor. And each type of odorant receptor has a different shape and set of chemical properties that determine which odors can bind to and activate it. Most of these receptors recognize multiple odors, and most odors can bind to multiple different receptors. What encodes the identity of a specific odor in the brain is determined by which combination of receptors are activated, and their relative strength of activation.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/MyHR6a-zJM0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video from the Wachowiak Lab at the University of Utah shows the activity of the olfactory bulb in a mouse brain as the mouse is exposed to different odors. Different odors make different combinations of neurons in the olfactory bulb light up.</span></figcaption>
</figure>
<p>An animal like a mouse has about a <a href="https://doi.org/10.1016/j.neuron.2005.10.022">thousand types</a> of odorant receptors. Having a large number of these receptors with diverse shapes allows the system to detect and distinguish between a very large number of chemically unique odors, including ones the animal has never encountered before. Most odors in the environment are often a mix of many different types of molecules. The smell of some <a href="https://doi.org/10.1146/annurev.ecolsys.38.091206.095601">flowers</a> can be a blend of over 100 different chemical compounds.</p>
<p>Once an odor molecule binds to a receptor, sensory neurons send specific <a href="https://nba.uth.tmc.edu/neuroscience/m/s2/chapter09.html">electrical signals</a> into compartments of the brain called <a href="https://doi.org/10.3389/fncir.2014.00098">olfactory glomeruli</a>. Different odors elicit distinct patterns of electrical activity across these regions, and this generates a specific neural representation of the odor in the brain.</p>
<p>An important step toward understanding olfaction is figuring out how different classes of odors map to different patterns of electrical signals in the brain.</p>
<p>Neuroscientists hypothesize that as these signals undergo successive stages of processing deep in the brain, sensory representations of odor are <a href="https://doi.org/10.1146/annurev-neuro-071013-013941">reformatted</a> in ways that extract information most useful to survival. This could be whether the smell is coming from something nutritious, indicating a potential source of food, or it could help the animal identify whether the smell is coming from a potential competitor or predator.</p>
<p>These reformatted sensory representations form the basis for how animals perceive smell and determine what actions they take in response to this information.</p>
<h2>From odor to action</h2>
<p>Once information about a particular odor reaches the brain, it often elicits both instinctual and learned <a href="https://doi.org/10.1523/JNEUROSCI.1668-18.2018">behaviors</a>. Odors that signal danger may trigger the animal to freeze or run away, while odors from a member of the same species may trigger the animal to mark its territory or initiate courtship. </p>
<p>In many cases, animals perform these tasks with incredible <a href="https://www.pbs.org/wgbh/nova/article/dogs-sense-of-smell/">precision and effectiveness</a>. It’s still common to use search dogs to find lost people and pigs to find truffles because available technologies aren’t capable of performing as well.</p>
<p>Animals achieve this level of performance not just because they’re able to detect and identify an odor. They’re also able to integrate odor features, like how intense the odor smells, with environmental clues, like wind direction, and internal cues, like hunger. All this information comes together to generate specific sequences of behaviors such as “face into the wind and then walk forward.”</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/FLH36ML8IEU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Dogs rely on smells to provide long-distance information. Humans, on the other hand, use smells for short distances.</span></figcaption>
</figure>
<p>To understand how odor guides these behaviors, scientists measure or manipulate an animal’s brain activity as they perform specific actions. This is done using imaging, electrophysiology or <a href="https://doi.org/10.1038/nn.4091">optogenetics</a>, which selectively activates specific neurons by shining a light on them. These approaches allow researchers to understand how patterns of brain activity shift when an animal changes its behavior to chase after an odor, or how environmental and internal cues combine to produce a best guess on the location of its next meal. </p>
<h2>Leading science and technology by the nose</h2>
<p>The olfactory system offers a unique opportunity to understand how the brain processes environmental information and translates it to behavior. Compared to other areas of the brain, the olfactory circuit is simpler in structure and uses fewer stages of processing. Its relative simplicity is what allows scientists like us to study it from end to end and learn how the brain works as a whole.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A rescue worker with a service dog goes through the ruins of a residential house to search for survivors" src="https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=415&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=415&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=415&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=521&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=521&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441622/original/file-20220119-15-1atg4u1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=521&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Robots may one day be able to replace dogs in search and rescue situations.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/rescue-worker-with-a-service-dog-goes-through-the-ruins-of-news-photo/1229115883">Valery Sharifulin/TASS via Getty Images</a></span>
</figcaption>
</figure>
<p>Understanding brain function through the lens of olfaction could also pave the way for transformative developments in engineering, neuroscience and public health. Our research should accelerate the development of robots with <a href="https://doi.org/10.1177%2F0278364908095118">electronic noses</a> that can use odors to search for <a href="https://doi.org/10.1016/j.sbsr.2019.100305">chemical weapons</a>,
<a href="https://www.reuters.com/world/us/divers-try-locate-source-reported-oil-spill-gulf-coast-guard-2021-09-05/">underwater oil spills</a>
and <a href="https://doi.org/10.3390/inventions5030028">natural gas</a> leaking from pipelines in environments where it may be tedious or dangerous for humans or animals to go. Robots might also be able to search for missing people or disaster victims, something typically done with <a href="https://www.popsci.com/scientists-want-to-build-robotic-sniffer-that-outperforms-search-dogs/">trained dogs</a>.</p>
<p>An exciting future in scientific and medical development, we believe, is right under our noses.</p>
<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><img src="https://counter.theconversation.com/content/173811/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Crimaldi receives funding from the National Science Foundation, the National Institutes of Health, and the Department of Defense.</span></em></p><p class="fine-print"><em><span>Brian H Smith receives funding from the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Elizabeth Hong receives funding from the National Science Foundation, the National Institutes of Health, the Curci Research Foundation, and the Luce Foundation</span></em></p><p class="fine-print"><em><span>Nathan Urban receives funding from the National Science Foundation and the National Institutes of Health. </span></em></p>Understanding how the brain translates smells into behavior change can help advance search and rescue technology and treatments for neurological conditions.John Crimaldi, Professor of Civil, Environmental and Architectural Engineering, University of Colorado BoulderBrian H. Smith, Trustees of ASU Professor, Arizona State UniversityElizabeth Hong, Assistant Professor of Neuroscience, California Institute of TechnologyNathan Urban, Provost and Senior Vice President, Lehigh University Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1698822021-10-29T09:24:05Z2021-10-29T09:24:05ZAvec le réchauffement climatique, l’être humain va atteindre ses limites de résistance à la chaleur<p>Au cours des derniers millénaires, les différentes sociétés humaines ont pu s’appuyer sur une <a href="https://www.pnas.org/content/early/2020/04/28/1910114117">large variété de conditions climatiques</a> pour soutenir leur croissance fulgurante et leurs progrès. Mais aujourd’hui, l’éventail des conditions météorologiques que notre espèce est peu à peu amenée à rencontrer se modifie sous l’effet du réchauffement climatique.</p>
<p>Des conditions <a href="https://www.pnas.org/content/104/14/5738.short">entièrement nouvelles</a> pourraient bien apparaître dans les prochaines décennies. Même si les technologies peuvent nous aider, cette menace ne doit pas être prise à la légère, car notre premier système d’adaptation n’est pas mécanique, il est biologique : c’est notre corps – et il a ses limites.</p>
<p>Notre capacité à réguler notre température interne a joué un rôle clé dans la colonisation de la planète par les humains. Marchant sur deux jambes (ce qui réclame <a href="https://www.sciencedaily.com/releases/2007/07/070720111226.htm">moins d’énergie</a> que de se déplacer sur quatre membres), sans fourrure et dotés d’un système de refroidissement basé sur la sueur, <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/cphy.c140011">nous sommes bien conçus pour combattre la chaleur</a>. Cette dernière influe toutefois sur notre capacité à nous mouvoir et à rester en bonne santé.</p>
<p>Dans les faits, notre physiologie impose des limites <a href="https://theconversation.com/cette-chaleur-insoutenable-qui-menace-les-regions-tropicales-119943">à ce que nous pouvons supporter</a> en termes de chaleur et d’humidité.</p>
<h2>Température sèche et température humide</h2>
<p>La température habituellement indiquée lors des prévisions météorologiques correspond à la température dite <a href="https://www.insa-toulouse.fr/fr/formation/glossaire-gc-en-lsf/temperature-seche.html">« sèche » (ou « de bulbe sec »)</a>, mesurée à l’abri de l’humidité. Dès que cette température dépasse 35 °C environ, le corps a recours à l’évaporation de l’eau (principalement par la transpiration) pour dissiper la chaleur.</p>
<p>La température dite « humide » (ou « de bulbe humide ») est, elle, mesurée en prenant en compte l’effet de refroidissement dû à l’évaporation sur un thermomètre : elle est donc normalement plus basse que la température de bulbe sec.</p>
<p>Plus la différence entre la température « normale » et celle de bulbe humide est grande, plus l’air est sec et l’eau peut s’évaporer. Cela influe sur l’efficacité avec laquelle notre système de refroidissement par transpiration peut fonctionner.</p>
<p>Mais lorsque la température de bulbe humide dépasse les 35 °C, l’air est en même temps si chaud et humide que la transpiration ne peut plus faire son office : la sueur déposée sur notre peau ne s’évapore plus. Impossible dès lors de faire baisser notre température. Rester trop longtemps au-dessus de ce seuil peut entraîner la mort par surchauffe.</p>
<p>Si cette limite de 35 °C peut sembler basse, elle ne l’est pas.</p>
<p>Lorsque le Royaume-Uni a souffert d’une température sèche record de <a href="https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2019/new-official-highest-temperature-in-uk-confirmed">38,7 °C en juillet 2019</a>, la température humide à Cambridge ne dépassait pas 24 °C. Même lors de la canicule meurtrière de Karachi en 2015, la température au bulbe humide est restée inférieure à 30 °C.</p>
<p>En fait, en dehors d’un hammam, peu de gens ont connu une température humide proche de 35 °C. Ce seuil est jusqu’à présent resté largement <a href="https://www.pnas.org/content/107/21/9552">hors des standards climatiques terrestres</a> expérimentés ces derniers millénaires.</p>
<p>Mais nos <a href="https://advances.sciencemag.org/content/6/19/eaaw1838">récents travaux</a> montrent que les choses changent : cette limite des 35 °C se rapproche, laissant une marge de sécurité de plus en plus réduite dans les endroits les plus chauds et les plus humides de la planète.</p>
<h2>Dépasser les limites humaines</h2>
<p>Des études de modélisation avaient déjà indiqué que les températures humides pourraient <a href="https://www.pnas.org/content/107/21/9552">régulièrement dépasser 35 °C</a> si la planète excédait la limite de réchauffement de 2 °C fixée dans l’<a href="https://theconversation.com/cop21-ce-quil-faut-retenir-de-laccord-de-paris-52257">Accord de Paris sur le climat de 2015</a>.</p>
<p><a href="https://www.nature.com/articles/nclimate2833?source=post_page">Golfe Persique</a>, <a href="https://advances.sciencemag.org/content/3/8/e1603322.abstract">Asie du Sud</a> et <a href="https://www.nature.com/articles/s41467-018-05252-y">plaine de Chine du Nord</a> seraient alors en première ligne de cette chaleur humide mortelle.</p>
<p><a href="https://advances.sciencemag.org/content/6/19/eaaw1838">Notre analyse</a> des températures de bulbes humides entre 1979 et 2017 a confirmé ces mises en garde. Autre point important : alors que les études précédentes portaient sur des régions relativement vastes (à l’échelle des grandes zones métropolitaines), nous avons de notre côté examiné des milliers d’enregistrements de stations météorologiques partout dans le monde. Nous avons ainsi constaté qu’à une échelle plus locale, de nombreux sites se rapprochaient rapidement de la limite des 35 °C.</p>
<p>La fréquence des températures élevées en condition humide (supérieures à 31 °C par exemple) a plus que doublé dans le monde depuis 1979. Dans certains des endroits les plus chauds et les plus humides, comme la côte des Émirats arabes unis, les températures humides ont déjà dépassé 35 °C. On entre ici dans des situations que notre physiologie ne peut gérer.</p>
<p>Jusqu’à présent, dépasser les 35 °C n’aura eu que des conséquences limitées, les habitants de ces régions ayant l’habitude de supporter des conditions extrêmes – par une architecture adaptée ou en <a href="https://www.washingtonpost.com/news/capital-weather-gang/wp/2015/08/03/chart-busting-heat-and-humidity-in-iran-city-were-completely-normal-says-local/">s’abritant dans des espaces climatisés</a>.</p>
<p>Mais le recours massif au refroidissement artificiel pour faire face à une chaleur croissante pourrait avoir pour effet de <a href="https://www.iea.org/news/air-conditioning-use-emerges-as-one-of-the-key-drivers-of-global-electricity-demand-growth">surcharger la demande d’énergie</a> et de laisser une large population <a href="https://www.nature.com/articles/s41558-019-0525-6">dangereusement exposée aux pannes de courant</a>. Cette solution abandonnerait également les membres les plus vulnérables de la société et n’aiderait pas ceux qui n’ont d’autre choix que de sortir.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=458&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=458&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=458&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Records absolus de chaleur humide enregistrés dans les stations météorologiques du monde entier entre 1979 et 2017.</span>
<span class="attribution"><a class="source" href="https://advances.sciencemag.org/content/6/19/eaaw1838">Colin Raymond</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>La seule façon d’éviter une confrontation croissante avec un territoire thermique inconnu et hostile consiste à réduire nos émissions de gaz à effet de serre.</p>
<p>Le ralentissement de l’économie pendant la pandémie de Covid-19 a bien vu une réduction de <a href="https://theconversation.com/coronavirus-is-a-sliding-doors-moment-what-we-do-now-could-change-earths-trajectory-137838">4 à 7 %</a> de ces émissions en 2020, nous rapprochant du niveau de <a href="https://www.iea.org/reports/global-energy-review-2020/global-energy-and-co2-emissions-in-2020">2010</a>. Mais les concentrations de gaz à effet de serre continuent inexorablement et rapidement d’augmenter dans l’atmosphère.</p>
<p>Il nous faut dès lors tenter de nous <a href="https://www.mdpi.com/1660-4601/11/4/3473">adapter</a>, en encourageant des changements de comportement simples (comme éviter les activités en plein air pendant la journée) et en renforçant les plans d’intervention d’urgence lorsque les extrêmes de chaleur sont imminents. Ces mesures permettront de gagner du temps face à la progression <a href="https://www.nature.com/articles/srep30294">inexorable</a> de ces nouveaux profils climatiques.</p>
<p>Espérons que nos recherches puissent contribuer à mettre en lumière certains des défis liés au changement climatique et à la hausse des températures. L’émergence d’une chaleur et d’une humidité sans précédent – au-delà de ce que notre physiologie peut tolérer – n’en est qu’un échantillon.</p>
<p>Espérons également que le sentiment de vulnérabilité provoqué par l’irruption du Covid-19 renforcera les engagements mondiaux en faveur de la neutralité carbone, en reconnaissant l’intérêt de préserver les conditions qui nous sont familières… et encore supportables.</p><img src="https://counter.theconversation.com/content/169882/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Les auteurs ne travaillent pas, ne conseillent pas, ne possèdent pas de parts, ne reçoivent pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'ont déclaré aucune autre affiliation que leur organisme de recherche.</span></em></p>Réchauffement planétaire et humidité vont de pair. De quoi contrer notre meilleure défense, la transpiration, et nous faire entrer dans une période physiologiquement inédite… et dangereuse.Tom Matthews, Lecturer in Climate Science, Loughborough UniversityColin Raymond, Postdoctoral Researcher, California Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1506352020-11-23T19:03:22Z2020-11-23T19:03:22ZAncient sponges or just algae? New research overturns chemical evidence for the earliest animals<figure><img src="https://images.theconversation.com/files/370695/original/file-20201123-15-1t2gd6i.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1996%2C1125&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Ilya Bobrovskiy</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Sponges are the simplest of animals, and they may stand at the root of all complex animal life on Earth, including us humans. Scientists study the evolution of the earliest sponges, hundreds of millions of years ago, to learn about the conditions that led life to develop from single-celled amoeba-like creatures to the large, mobile and even intelligent animals that surround us today.</p>
<p>Exactly when and how animals emerged on our planet is a subject of fierce debate among scientists. While the most ancient sponge fossils ever found are around 540 million years old, some have argued that fossil molecules dating from 635 million years ago are evidence of earlier animal life.</p>
<p>However, we have now shown that these fossil molecules may actually have been produced by algae and later transformed by geological forces to resemble traces of animal fats. Our international team of scientists, from the Max Planck Institute for Biogeochemistry, the University of Bremen, the Australian National University, the University of Strasbourg, CSIRO and Caltech, have outlined our discoveries in <a href="http://www.nature.com/articles/s41559-020-01336-5">two</a> complementary <a href="http://www.nature.com/articles/s41559-020-01334-7">papers</a> published in Nature Ecology and Evolution today.</p>
<h2>Ancient fat in the limelight</h2>
<p>The oldest fossil remnants of sponges that can be recognised in ancient rocks are around 540 million years old and date to the early Cambrian period. But there are yet older fossils of animals that belong to the biota of the <a href="https://en.wikipedia.org/wiki/Ediacaran">Ediacara period</a>.</p>
<p>Among the enigmatic Ediacaran creatures that lived up to 40 million years before the “<a href="https://en.wikipedia.org/wiki/Cambrian_explosion">Cambrian explosion</a>” of complex life was an oval-shaped organism called <em>Dickinsonia</em>. It could exceed one meter in size and its segmented body is popularly depicted as something like a quilted air-mattress.</p>
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Read more:
<a href="https://theconversation.com/friday-essay-the-silence-of-ediacara-the-shadow-of-uranium-72058">Friday essay: the silence of Ediacara, the shadow of uranium</a>
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<p><a href="https://science.sciencemag.org/content/361/6408/1246">A recent study</a> detected fossil cholesterol, 558 million years old, in Dickinsonia fossils. Cholesterol is a characteristic animal fat, so this suggests that <em>Dickinsonia</em> really was a genuine animal rather than a fungus or something else.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/370758/original/file-20201123-15-3hmz02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/370758/original/file-20201123-15-3hmz02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/370758/original/file-20201123-15-3hmz02.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/370758/original/file-20201123-15-3hmz02.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/370758/original/file-20201123-15-3hmz02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/370758/original/file-20201123-15-3hmz02.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/370758/original/file-20201123-15-3hmz02.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A cast of a fossil imprint left by the ancient creature Dickinsonia.</span>
<span class="attribution"><span class="source">Ilya Bobrovskiy</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>But even older than these cholesterol traces found in body fossils are fossilised organic molecules found alone. In 2009, a team of scientists <a href="https://www.nature.com/articles/nature07673">discovered</a> molecules called sterols in 635 million-year-old sediments in Oman on the Arabian Peninsula that once was the bottom of an inland sea.</p>
<p>At the time the study was conducted, the only organisms that were known to produce similar sterols were specific sponges. Here was the long-sought earliest evidence for animals in the world. </p>
<p>What is more, the fossil “sponge sterols” were found in rocks of this age around the globe, suggesting that these animals were very abundant, possibly covering much of the ocean floor. </p>
<p>This exciting discovery suggested that the ancient fat recovered from rocks in Oman represented some of the first recognisable traces that animals left on our planet. But do ancient fat signatures alone really suffice to reconstruct early animal evolution?</p>
<h2>Geological time takes its toll</h2>
<p>Unfortunately, interpretation of fossil sterols from million-year-old rocks may not be as straightforward as comparing it to the sterols of living organisms. After an organism dies, its remains settle on the bottom of the ocean. They get buried deeper and deeper as sediment builds up, and as the temperature rises, the biological molecules begin to change. </p>
<p>To the disappointment of us scientists, most knowledge about organisms of the past gets erased by these changes. The most informative parts of the molecules are also the most fragile, and they disappear over time to leave behind a more generic, chemically rigid skeleton. </p>
<p>We wondered whether other changes might occur as well, potentially producing molecules that look like fossil sterols of modern sponges but actually have nothing to do with animals. Working in two groups, we approached this question from different ends.</p>
<figure class="align-center ">
<img alt="A sea sponge against a white background." src="https://images.theconversation.com/files/370700/original/file-20201123-17-oj2ag8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/370700/original/file-20201123-17-oj2ag8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=442&fit=crop&dpr=1 600w, https://images.theconversation.com/files/370700/original/file-20201123-17-oj2ag8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=442&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/370700/original/file-20201123-17-oj2ag8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=442&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/370700/original/file-20201123-17-oj2ag8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=555&fit=crop&dpr=1 754w, https://images.theconversation.com/files/370700/original/file-20201123-17-oj2ag8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=555&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/370700/original/file-20201123-17-oj2ag8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=555&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sponges are among the simplest and earliest animals to have evolved on Earth.</span>
<span class="attribution"><span class="source">Mareike Neumann</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Deceptive alterations</h2>
<p>One <a href="http://www.nature.com/articles/s41559-020-01336-5">study</a>, headed by Lennart van Maldegem and Benjamin Nettersheim, focused on sterol molecules preserved in sediments up to 800 million years old. It was thought that these molecules might extend the geological record of animals even deeper into Earth’s history than the famous Oman signatures. </p>
<p>In these sediments, the study uncovered a significant connection between some of the sponge-associated molecules and compounds known to be generated through geological alterations, indicating that they shared the same origin. </p>
<figure class="align-center ">
<img alt="Photo showing two small figures in the foreground in front of large rocky landscape in the Grand Canyon." src="https://images.theconversation.com/files/370697/original/file-20201123-13-rywc3v.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/370697/original/file-20201123-13-rywc3v.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=311&fit=crop&dpr=1 600w, https://images.theconversation.com/files/370697/original/file-20201123-13-rywc3v.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=311&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/370697/original/file-20201123-13-rywc3v.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=311&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/370697/original/file-20201123-13-rywc3v.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=391&fit=crop&dpr=1 754w, https://images.theconversation.com/files/370697/original/file-20201123-13-rywc3v.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=391&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/370697/original/file-20201123-13-rywc3v.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=391&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">To assess the molecular fossils in ancient environments sedimentary rock samples were collected from various Precambrian depositional basins, including the Grand Canyon, USA. Photo courtesy of Lennart van Maldegem.</span>
<span class="attribution"><span class="source">Lennart van Maldegem</span>, <span class="license">Author provided</span></span>
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</figure>
<p>To verify this hypothesis, we then carried out laboratory experiments to simulate the effect of geological heating on particular molecules produced by algae. The resulting molecular signatures were surprisingly similar to those of the ancient rocks. So the fossil fat provides interesting insights into the molecular make-up of early algae, but unfortunately does not illuminate early animal evolution.</p>
<p>The <a href="http://www.nature.com/articles/s41559-020-01334-7">second study</a>, led by Ilya Bobrovskiy, focused on green algae themselves. Today they are mainly common in ponds, rivers and tidal pools, but between 500 million and 650 million years ago they dominated oceans all over the world. </p>
<p>By heating green algal molecules in the laboratory – similar to what happens to molecules in rocks – this study showed that some of the most common sterols of green algae can be easily altered into sponge-like molecules. This indicates that also the ancient Oman signature may represent sterols that were originally produced by primitive algae and subsequently altered by geological processes. It turns out that even ancient fat can be deceptive.</p>
<h2>Oldest evidence of animals only 20 million years before the Cambrian Explosion</h2>
<p>Together, our two studies demonstrate that sponge-associated molecules in ancient rocks are not a tell-tale sign of animals. Instead, they were most likely generated by the remains of common algae exposed to geological heating. </p>
<p>These results should now finally settle the long-lasting debate surrounding the oldest molecular traces of early animals. There currently is no evidence that sponge-like animals conquered the oceans before 540 million years ago, when the first unambiguous fossils of sponges and most other groups of animals start to appear in the geological record. The earliest evidence for animals on Earth is now the 558 million-years-old <em>Dickinsonia</em> and other Ediacaran animals.</p>
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Read more:
<a href="https://theconversation.com/evolutions-big-bang-explained-and-its-slower-than-predicted-18098">Evolution's 'big bang' explained (and it's slower than predicted)</a>
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<img src="https://counter.theconversation.com/content/150635/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>Ancient fatty molecules, once believed to be traces of some of the first animals to live on Earth, may have been produced by algae instead.Lennart van Maldegem, Postdoctoral Fellow, Research School of Earth Sciences, Australian National UniversityBenjamin Nettersheim, Postdoctoral Researcher, Max Planck Institute for BiogeochemistryChristian Hallmann, Research Group Leader, Max Planck Institute for BiogeochemistryIlya Bobrovskiy, Postdoctoral Fellow, California Institute of TechnologyJochen Brocks, Professor, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1383432020-05-20T17:55:46Z2020-05-20T17:55:46ZGlobal warming now pushing heat into territory humans cannot tolerate<figure><img src="https://images.theconversation.com/files/336419/original/file-20200520-152298-17undq1.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5472%2C2711&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/full-frame-shot-close-sand-texture-1501158044">Samkhanproduction/Shutterstock</a></span></figcaption></figure><p>The explosive growth and success of human society over the past 10,000 years has been underpinned by a <a href="https://www.pnas.org/content/early/2020/04/28/1910114117">distinct range of climate conditions</a>. But the range of weather humans can encounter on Earth – the “climate envelope” – is shifting as the planet warms, and conditions <a href="https://www.pnas.org/content/104/14/5738.short">entirely new to civilisation</a> could emerge in the coming decades. Even with modern technology, this should not be taken lightly.</p>
<p>Being able to regulate our temperature has played a key role in enabling humans to dominate the planet. Walking on two legs, without fur, and with a sweat-based cooling system, <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/cphy.c140011">we’re well designed to beat the heat</a>. But hot weather already limits our ability to work and stay healthy. In fact, our physiology places bounds on the level of heat and humidity <a href="https://theconversation.com/heatwave-think-its-hot-in-europe-the-human-body-is-already-close-to-thermal-limits-elsewhere-121003">we can cope with</a>. </p>
<p>The normal temperature you see reported on weather forecasts is called the “drybulb” temperature. Once that rises above about 35°C, the body must rely on evaporating water (mainly through sweating) to dissipate heat. The “wetbulb” temperature is a measure that includes the chilling effect from evaporation on a thermometer, so it is normally much lower than the drybulb temperature. It indicates how efficiently our sweat-based cooling system can work. </p>
<p>Once the wetbulb temperature crosses about 35°C, the air is so hot and humid that not even sweating can lower your body temperature to a safe level. With continued exposure above this threshold, death by overheating can follow.</p>
<p>A 35°C limit may sound modest, but it isn’t. When the UK sweltered with a record drybulb temperature of <a href="https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2019/new-official-highest-temperature-in-uk-confirmed">38.7°C in July 2019</a>, the wetbulb temperature in Cambridge was no more than 24°C. Even in Karachi’s killer heatwave of 2015, the wetbulb temperature stayed below 30°C. In fact, outside a steam room, few people have encountered anything close to 35°C. It has mostly been <a href="https://www.pnas.org/content/107/21/9552">beyond Earth’s climate envelope</a> as human society has developed.</p>
<p>But our <a href="https://advances.sciencemag.org/content/6/19/eaaw1838">recent research</a> shows that the 35°C limit is drawing closer, leaving an ever-shrinking safety margin for the hottest and most humid places on Earth.</p>
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Read more:
<a href="https://theconversation.com/will-three-billion-people-really-live-in-temperatures-as-hot-as-the-sahara-by-2070-137776">Will three billion people really live in temperatures as hot as the Sahara by 2070?</a>
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<hr>
<h2>Heat beyond human tolerance</h2>
<p>Modelling studies had already indicated that wetbulb temperatures could <a href="https://www.pnas.org/content/107/21/9552">regularly cross 35°C</a> if the world sails past the 2°C warming limit set out in the Paris climate agreement in 2015, with <a href="https://www.nature.com/articles/nclimate2833?source=post_page">The Persian Gulf</a>, <a href="https://advances.sciencemag.org/content/3/8/e1603322.abstract">South Asia</a> and <a href="https://www.nature.com/articles/s41467-018-05252-y">North China Plain</a> on the frontline of deadly humid heat.</p>
<p>Our analysis of wetbulb temperatures from 1979-2017 did not disagree with these warnings about what may be to come. But whereas past studies had looked at relatively large regions (on the scale of major metropolitan areas), we also examined thousands of weather station records worldwide and saw that, at this more local scale, many sites were closing in much more rapidly on the 35°C limit. The frequency of punishing wetbulb temperatures (above 31°C, for example) has more than doubled worldwide since 1979, and in some of the hottest and most humid places on Earth, like the coastal United Arab Emirates, wetbulb temperatures have already flickered past 35°C. The climate envelope is pushing into territory where our physiology cannot follow.</p>
<p>The consequences of crossing 35°C, however brief, have perhaps been mainly symbolic so far, as residents of the hottest places are used to riding out extreme heat by <a href="https://www.washingtonpost.com/news/capital-weather-gang/wp/2015/08/03/chart-busting-heat-and-humidity-in-iran-city-were-completely-normal-says-local/">sheltering in air-conditioned spaces</a>. But relying on artificial cooling to cope with the growing heat would <a href="https://www.iea.org/news/air-conditioning-use-emerges-as-one-of-the-key-drivers-of-global-electricity-demand-growth">supercharge energy demand</a> and leave many people <a href="https://www.nature.com/articles/s41558-019-0525-6%22%22">dangerously exposed to power failures</a>. It would also abandon the most vulnerable members of society and doesn’t help those who have to venture outside.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=458&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=458&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336406/original/file-20200520-152302-12fi2p7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=458&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">All-time maximum humid heat records at weather stations around the world, 1979-2017.</span>
<span class="attribution"><a class="source" href="https://advances.sciencemag.org/content/6/19/eaaw1838">Colin Raymond</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The only way to avoid being carried further and more frequently into uncharted heat territory is to reduce greenhouse gas emissions to net zero. The economic slowdown during the coronavirus pandemic is expected to <a href="https://theconversation.com/coronavirus-is-a-sliding-doors-moment-what-we-do-now-could-change-earths-trajectory-137838">slash emissions by 4-7% in 2020</a>, bringing them close to where global emissions were <a href="https://www.iea.org/reports/global-energy-review-2020/global-energy-and-co2-emissions-in-2020">in 2010</a>. But concentrations of greenhouse gases are still rising rapidly in the atmosphere. We must also <a href="https://www.mdpi.com/1660-4601/11/4/3473%5D(https://www.mdpi.com/1660-4601/11/4/3473">adapt</a> where possible, by encouraging simple behavioural changes (like avoiding outdoor daytime activity) and by ramping up emergency response plans when heat extremes are imminent. Such steps will help to buy time against the <a href="https://www.nature.com/articles/srep30294">inexorable</a> forward march of the Earth’s climate envelope.</p>
<p>We hope that our research illuminates some of the challenges that may await us as global temperatures rise. The emergence of unprecedented heat and humidity – beyond what our physiology can tolerate – is just a portion of what could be in store. An even warmer and wetter world risks generating climate extremes beyond any human experience, including the potential for a whole host of “unknown unknowns”.</p>
<p>We hope that the sense of vulnerability to surprises left by COVID-19 invigorates global commitments to reaching carbon neutrality – recognising the value in preserving conditions that are somewhat familiar, rather than risking what may be waiting in a very novel climate ahead.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=140&fit=crop&dpr=1 600w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=140&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=140&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=176&fit=crop&dpr=1 754w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=176&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=176&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
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<p><em><a href="https://theconversation.com/imagine-newsletter-researchers-think-of-a-world-with-climate-action-113443?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=Imagineheader1138343">Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.</a></em></p><img src="https://counter.theconversation.com/content/138343/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>‘Wet-bulb’ temperature records show that deadly thresholds for heat and humidity are arriving faster than anticipated.Tom Matthews, Lecturer in Climate Science, Loughborough UniversityColin Raymond, Postdoctoral Researcher, California Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1368312020-04-22T18:45:02Z2020-04-22T18:45:02ZA smart second skin gets all the power it needs from sweat<p><em>The Research Brief is a short take about interesting academic work.</em></p>
<h2>The big idea</h2>
<p>Skin is the largest organ of the human body. It conveys a lot of information, including temperature, pressure, pleasure and pain. Electronic skin (e-skin) mimics the properties of biological skin. Recently developed e-skins are capable of wirelessly monitoring physiological signals. They could play a crucial role in the next generation of robotics and medical devices. </p>
<p><a href="http://www.gao.caltech.edu/">My lab at Caltech</a> is interested in studying human biology and monitoring human health by using advanced bioelectronic devices. The e-skin we have developed not only analyzes the chemical and molecular composition of human sweat, it’s <a href="http://robotics.sciencemag.org/lookup/doi/10.1126/scirobotics.aaz7946">fully powered by chemicals in sweat</a>.</p>
<h2>Why it matters</h2>
<p>Existing e-skins and wearable devices primarily focus on monitoring physiological parameters like heart rate and can’t assess health information at the molecular level. Moreover, they typically require batteries to power them, and the batteries need to be recharged frequently.</p>
<p>Despite recent efforts to harvest energy from the human body, there are no reports of self-powered e-skins that are able to perform biosensing and transmit the information via standard Bluetooth wireless communications. This comes down to the lack of power efficiency. There is a need for a self-powered device that can continuously collect molecular as well as physical information and wirelessly transmit the information to other devices.</p>
<h2>How we do this work</h2>
<p>The approach we take to harvesting energy from the human body is based on biofuel cells. Fuel cells convert chemical energy to electricity. The biofuel cells we developed for our e-skin convert the lactic acid in human sweat to electricity. In addition to the biofuel cells, the e-skin contains biosensors that can analyze metabolic information like glucose, urea and pH levels, to monitor for diabetes, ischaemia another health conditions, as well as physical information like skin temperature. The e-skin, made of soft materials and attached to a person’s skin, performs real-time biosensing, powered solely by sweat.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/329621/original/file-20200422-82699-uzmg0b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/329621/original/file-20200422-82699-uzmg0b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=403&fit=crop&dpr=1 600w, https://images.theconversation.com/files/329621/original/file-20200422-82699-uzmg0b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=403&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/329621/original/file-20200422-82699-uzmg0b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=403&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/329621/original/file-20200422-82699-uzmg0b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=506&fit=crop&dpr=1 754w, https://images.theconversation.com/files/329621/original/file-20200422-82699-uzmg0b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=506&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/329621/original/file-20200422-82699-uzmg0b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=506&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The sweat-powered biofuel cells in this electronic skin provide enough electricity to power biological sensors and transmit the information wirelessly to other devices.</span>
<span class="attribution"><span class="source">Yu et al., Sci. Robot. 5, eaaz7946 (2020)</span></span>
</figcaption>
</figure>
<p>Previously developed wearable biofuel cells <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/elan.201600019">don’t produce a lot of power</a> and aren’t very stable. We greatly improved the power output and stability of the biofuel cells by using novel nanomaterials for the cell’s two electrodes. The cathode of our biofuel cell is composed of a mesh of carbon nanotubes decorated with nanoparticles containing platinum and cobalt. The anode is a nanocomposite material that contains an enzyme that breaks down lactic acid. </p>
<p>The biofuel cells can generate a continuous, stable output as high as several milliwatts per square centimeter over multiple days in human sweat. That’s enough to power the biosensors as well as wireless communication. We demonstrated our e-skin by monitoring glucose, pH, ammonium ions and urea levels in studies using human subjects. We also used our e-skin as a human-machine interface to control the motion of a robotic arm and a prosthetic leg.</p>
<h2>What’s next</h2>
<p>We plan to further improve the power output of the biofuel cells and integrate different biosensors. The development of fully self-powered e-skin opens the door to numerous robotic and wearable health care possibilities. Wearable sensor arrays could be used for health monitoring, early disease diagnosis and potentially nutritional intervention. In addition, self-powered e-skin could be used to design and optimize next generation prosthetics.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p><img src="https://counter.theconversation.com/content/136831/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wei Gao receives funding from the National Institute of Health. </span></em></p>Lightweight, flexible materials can be used to make health-monitoring wearable devices, but powering the devices is a challenge. Using fuel cells instead of batteries could make the difference.Wei Gao, Assistant Professor of Medical Engineering, California Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1135362019-03-18T17:01:05Z2019-03-18T17:01:05ZNew evidence for a human magnetic sense that lets your brain detect the Earth’s magnetic field<figure><img src="https://images.theconversation.com/files/264258/original/file-20190317-28505-1b1zf7w.jpg?ixlib=rb-1.1.0&rect=17%2C247%2C2849%2C1818&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Do you have a magnetic compass in your head?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/moral-compass-career-path-concept-human-115938361">Lightspring/Shutterstock.com</a></span></figcaption></figure><p>Do human beings have a magnetic sense? <a href="https://www.springer.com/us/book/9783642797514">Biologists know</a> <a href="https://doi.org/10.1016/S0959-4388(00)00235-X">other animals do</a>. They think it helps creatures including bees, turtles and birds <a href="https://doi.org/10.1016/S0959-4388(02)00389-6">navigate through the world</a>.</p>
<p>Scientists have tried to investigate whether humans belong on the list of magnetically sensitive organisms. For decades, there’s been a back-and-forth between <a href="https://www.worldcat.org/title/human-navigation-and-the-sixth-sense/oclc/11022691&referer=brief_results">positive reports</a> and <a href="https://www.jstor.org/stable/1685499">failures to demonstrate</a> the trait in people, with <a href="https://www.springer.com/us/book/9781461379928">seemingly endless controversy</a>.</p>
<p>The mixed results in people may be due to the fact that virtually all past studies relied on behavioral decisions from the participants. If human beings do possess a magnetic sense, daily experience suggests that it would be very weak or deeply subconscious. Such faint impressions could easily be misinterpreted – or just plain missed – when trying to make decisions.</p>
<p>So our research group – including a <a href="https://maglab.caltech.edu/">geophysical biologist</a>, a <a href="https://neuro.caltech.edu">cognitive neuroscientist</a> and a <a href="http://www.isp.ac/index_e.html">neuroengineer</a> – took another approach. <a href="https://maglab.caltech.edu/human-magnetic-reception-laboratory/">What we found</a> arguably provides the first concrete neuroscientific <a href="https://doi.org/10.1523/ENEURO.0483-18.2019">evidence that humans do have a geomagnetic sense</a>. </p>
<h2>How does a biological geomagnetic sense work?</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=515&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=515&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=515&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=648&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=648&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264257/original/file-20190317-28479-jh5hpf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=648&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Life on Earth is exposed to the planet’s ever-present geomagnetic field that varies in intensity and direction across the planetary surface.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/illustration-physics-magnetic-field-that-extends-1165968205">Nasky/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>The Earth is surrounded by a magnetic field, generated by the movement of the planet’s liquid core. It’s why a magnetic compass points north. At Earth’s surface, this magnetic field is fairly weak, <a href="https://nationalmaglab.org/about/maglab-dictionary/tesla">about 100 times weaker</a> than that of a refrigerator magnet.</p>
<p>Over the past 50 years or so, scientists have shown that hundreds of organisms in nearly all branches of the bacterial, <a href="https://www.livescience.com/54242-protists.html">protist</a> and animal kingdoms have the ability to detect and respond to this geomagnetic field. In some animals – <a href="https://doi.org/10.1007/BF00611096">such as honey bees</a> – the geomagnetic behavioral responses are <a href="https://pdfs.semanticscholar.org/750f/ce1b8f4723b09dd2fb1324fc916c9578c77b.pdf">as strong as the responses</a> to light, odor or touch. Biologists have identified strong responses in vertebrates ranging from <a href="https://doi.org/10.1038/37057">fish</a>, <a href="http://jeb.biologists.org/content/205/24/3903.full">amphibians</a>, <a href="https://doi.org/10.1126/science.1064557">reptiles</a>, numerous birds and a diverse variety of mammals including <a href="http://jeb.biologists.org/content/120/1/1.short">whales</a>, <a href="https://doi.org/10.1038/srep09917">rodents</a>, <a href="https://doi.org/10.1371/journal.pone.0001676">bats</a>, <a href="https://doi.org/10.1073/pnas.0803650105">cows</a> and <a href="https://doi.org/10.7717/peerj.6117">dogs</a> – the last of which can be trained to find a hidden bar magnet. In all of these cases, the animals are using the geomagnetic field as components of their homing and navigation abilities, along with other cues like sight, smell and hearing.</p>
<p>Skeptics dismissed early reports of these responses, largely because there didn’t seem to be a biophysical mechanism that could translate the Earth’s weak geomagnetic field into strong neural signals. This view was dramatically changed by the <a href="https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/73/4/435/5435">discovery that living cells</a> have the <a href="https://doi.org/10.1126/science.472725">ability to</a> build nanocrystals of the <a href="https://doi.org/10.1126/science.201.4360.1026">ferromagnetic</a> <a href="http://jeb.biologists.org/content/140/1/35.short">mineral magnetite</a> – basically, tiny iron magnets. Biogenic crystals of magnetite were first seen in the teeth of one group of mollusks, later in <a href="https://doi.org/10.1126/science.170679">bacteria</a>, and then in a variety of other organisms ranging from protists and animals such as insects, fish and mammals, <a href="https://doi.org/10.1073/pnas.89.16.7683">including within tissues of the human brain</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=267&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=267&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=267&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=336&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=336&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264240/original/file-20190317-28475-1vhbs80.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=336&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chains of magnetosomes from a sockeye salmon.</span>
<span class="attribution"><span class="source">Mann, Sparks, Walker & Kirschvink, 1988</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Nevertheless, scientists haven’t considered humans to be magnetically sensitive organisms.</p>
<h2>Manipulating the magnetic field</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=596&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=596&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=596&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=749&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=749&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264038/original/file-20190314-28479-1665yfc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=749&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Schematic drawing of the human magnetoreception test chamber at Caltech.</span>
<span class="attribution"><span class="source">Modified from 'Center of attraction' by C. Bickel (Hand, 2016).</span></span>
</figcaption>
</figure>
<p>In our new study, we asked 34 participants simply to sit in our testing chamber while we directly recorded electrical activity in their brains with electroencephalography (EEG). Our modified <a href="https://science.howstuffworks.com/faraday-cage.htm">Faraday cage</a> included a set of 3-axis coils that let us create controlled magnetic fields of high uniformity via electric current we ran through its wires. Since we live in mid-latitudes of the Northern Hemisphere, the environmental magnetic field in our lab dips downwards to the north at about 60 degrees from horizontal. </p>
<p>In normal life, when someone rotates their head – say, nodding up and down or turning the head from left to right – the direction of the geomagnetic field (which remains constant in space) will shift relative to their skull. This is no surprise to the subject’s brain, as it directed the muscles to move the head in the appropriate fashion in the first place.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=513&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=513&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=513&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=645&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=645&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264239/original/file-20190317-28492-1jg4d65.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=645&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Study participants sat in the experimental chamber facing north, while the downwards-pointing field rotated clockwise (blue arrow) from northwest to northeast or counterclockwise (red arrow) from northeast to northwest.</span>
<span class="attribution"><span class="source">Magnetic Field Laboratory, Caltech</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>In our experimental chamber, we can move the magnetic field silently relative to the brain, but without the brain having initiated any signal to move the head. This is comparable to situations when your head or trunk is passively rotated by somebody else, or when you’re a passenger in a vehicle which rotates. In those cases, though, your body will still register vestibular signals about its position in space, along with the magnetic field changes – in contrast, our experimental stimulation was only a magnetic field shift. When we shifted the magnetic field in the chamber, our participants did not experience any obvious feelings.</p>
<p>The EEG data, on the other hand, revealed that certain magnetic field rotations could trigger strong and reproducible brain responses. One EEG pattern known from existing research, called alpha-ERD (event-related desynchronization), typically shows up when a person suddenly detects and processes a sensory stimulus. The brains were “concerned” with the unexpected change in the magnetic field direction, and this triggered the alpha-wave reduction. That we saw such alpha-ERD patterns in response to simple magnetic rotations is powerful evidence for human magnetoreception. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/6Y4S2eG9BJA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Video shows the dramatic, widespread drop in alpha wave amplitude (deep blue color on leftmost head) following counterclockwise rotations. No drop is observed after clockwise rotation or in the fixed condition. <i>Connie Wang, Caltech</i></span></figcaption>
</figure>
<p>Our participants’ brains only responded when the vertical component of the field was pointing downwards at about 60 degrees (while horizontally rotating), as it does naturally here in Pasadena, California. They did not respond to unnatural directions of the magnetic field – such as when it pointed upwards. We suggest the response is tuned to natural stimuli, reflecting a biological mechanism that has been shaped by natural selection.</p>
<p>Other researchers have shown that animals’ brains filter magnetic signals, only responding to those that are environmentally relevant. It makes sense to reject any magnetic signal that is too far away from the natural values because it most likely is from a magnetic anomaly - a lighting strike, or lodestone deposit in the ground, for example. One early report on birds showed that robins stop using the geomagnetic field if the strength is more than about <a href="https://doi.org/10.1126/science.176.4030.62">25 percent different from what they were used to</a>. It’s possible this tendency might be why previous researchers had trouble identifying this magnetic sense – if they <a href="https://doi.org/10.1016/S1388-2457(02)00186-4">cranked up the strength of the magnetic field</a> to “help” subjects detect it, they might have instead ensured that subjects’ brains ignored it.</p>
<p>Moreover, our series of experiments show that the receptor mechanism – the biological magnetometer in human beings – is not electrical induction, and can tell north from south. This latter feature rules out completely the so-called <a href="https://doi.org/10.1146/annurev-biophys-032116-094545">“quantum compass” or “cryptochrome”</a> mechanism which is popular these days in the animal literature on magnetoreception. Our results are consistent only with functional magnetoreceptor cells based on the <a href="https://doi.org/10.1016/0303-2647(81)90060-5">biological magnetite hypothesis</a>. Note that a magnetite-based system <a href="https://doi.org/10.1098/rsif.2009.0491.focus">can also explain</a> <a href="https://doi.org/10.1098/rsif.2009.0435.focus">all of the behavioral effects in birds</a> that promoted the rise of the quantum compass hypothesis.</p>
<h2>Brains register magnetic shifts, subconsciously</h2>
<p>Our participants were all unaware of the magnetic field shifts and their brain responses. They felt that nothing had happened during the whole experiment – they’d just sat alone in dark silence for an hour. Underneath, though, their brains revealed a wide range of differences. Some brains showed almost no reaction, while other brains had alpha waves that shrank to half their normal size after a magnetic field shift.</p>
<p>It remains to be seen what these hidden reactions might mean for human behavioral capabilities. Do the weak and strong brain responses reflect some kind of individual differences in navigational ability? Can those with weaker brain responses benefit from some kind of training? Can those with strong brain responses be trained to actually feel the magnetic field? </p>
<p>A human response to Earth-strength magnetic fields might seem surprising. But given the evidence for magnetic sensation in our animal ancestors, it might be more surprising if humans had completely lost every last piece of the system. Thus far, we’ve found evidence that people have working magnetic sensors sending signals to the brain – a previously unknown sensory ability in the subconscious human mind. The full extent of our magnetic inheritance remains to be discovered.</p><img src="https://counter.theconversation.com/content/113536/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shinsuke Shimojo received funding from Human Frontier Science Program (HFSP), Japanese Science and Technology Agency (JST), and currently receives funding from DARPA. </span></em></p><p class="fine-print"><em><span>Daw-An Wu receives funding from DARPA. </span></em></p><p class="fine-print"><em><span>Joseph Kirschvink receives funding from the RadioBio program of DARPA, and previous support for this work was from the Human Frontiers Science Program (HFSP).</span></em></p>Your brain’s sensory talents go way beyond those traditional five senses. A team of geoscientists and neurobiologists explored how the human brain monitors and responds to magnetic fields.Shinsuke Shimojo, Gertrude Baltimore Professor of Experimental Psychology, California Institute of TechnologyDaw-An Wu, California Institute of TechnologyJoseph Kirschvink, Nico and Marilyn Van Wingen Professor of Geobiology, California Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1047262018-10-11T18:01:59Z2018-10-11T18:01:59ZSolving the mystery of the wimpy supernova<figure><img src="https://images.theconversation.com/files/240118/original/file-20181010-72106-2xf7ih.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The bubbly cloud, called Puppis A, is an irregular shock wave, generated by a supernova that would have been witnessed on Earth 3,700 years ago. </span> <span class="attribution"><a class="source" href="https://www.nasa.gov/jpl/spitzer/chandra/pia18468">NASA</a></span></figcaption></figure><p>A spectacular supernova explosion, more than a billion times brighter than our sun, marked the birth of a neutron star orbiting its hot and dense companion. Now these two dense remnants are destined to spiral into each other in about a billion years, eventually merging and yielding some of the heaviest known elements in the universe. </p>
<p>The explosion occurred in a galaxy similar to our own Milky Way, nearly 920 million light years away. A small telescope at Palomar observatory in California detected the first photons from the supernova – named “iPTF 14gqr” – just hours after the explosion, when it was more than 10 times hotter than the surface of our sun. As the brightness of the supernova evolved during the next two weeks, an international team of astronomers used the data to trace the origin of the explosion to a massive star with a radius 500 times that of the sun. </p>
<p>But it wasn’t just the giant size of the star that made this discovery particularly noteworthy. What was unusual was that the star also seemed to be the lightest of all known exploding giant stars. This massive star had been robbed of nearly all of its mass, perhaps by a dense orbiting partner. When it exploded, it left behind a newborn neutron star that continued to orbit its companion. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/240145/original/file-20181010-72127-17e668b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/240145/original/file-20181010-72127-17e668b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/240145/original/file-20181010-72127-17e668b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=264&fit=crop&dpr=1 600w, https://images.theconversation.com/files/240145/original/file-20181010-72127-17e668b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=264&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/240145/original/file-20181010-72127-17e668b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=264&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/240145/original/file-20181010-72127-17e668b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=332&fit=crop&dpr=1 754w, https://images.theconversation.com/files/240145/original/file-20181010-72127-17e668b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=332&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/240145/original/file-20181010-72127-17e668b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=332&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 three panels represent moments before, during, and after the faint supernova iPTF14gqr, visible in the middle panel, appeared in the outskirts of a spiral galaxy located 920 million light years away. The massive star that died in the supernova left behind a neutron star in a very tight binary system. These dense stellar remnants will ultimately spiral into each other and merge in a spectacular explosion, giving off gravitational and electromagnetic waves.</span>
<span class="attribution"><span class="source">SDSS/Caltech/Keck</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Understanding the formation of binary star systems in which two super dense stars orbit each other has always been a puzzle. These fleeting supernovae that yield these dense binary star systems are both rare and difficult to find, because they quickly appear and disappear in the sky – about five times faster than a typical supernova. </p>
<p>This <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aas8693">first observation of a “ultra-stripped” supernova</a>, which my colleagues and I detail in a new study, not only provides insights into the formation of these systems but also reveals the final stages in the lives of these unique massive stars that have been plundered of all of their mass before they die.</p>
<h2>Solving a longstanding mystery</h2>
<p>Stars born with more than eight times the mass of the sun quickly run out of fuel and succumb to gravity at the end of their lives – collapsing in on themselves and exploding in a supernova. When this happens, all of the star’s outer layers – a few times the mass of the sun – are scattered.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/240258/original/file-20181011-154586-v7n676.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/240258/original/file-20181011-154586-v7n676.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/240258/original/file-20181011-154586-v7n676.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/240258/original/file-20181011-154586-v7n676.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/240258/original/file-20181011-154586-v7n676.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/240258/original/file-20181011-154586-v7n676.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/240258/original/file-20181011-154586-v7n676.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/240258/original/file-20181011-154586-v7n676.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A binary star system is composed of two stars orbiting each other. Here the larger blue star is absorbing the other smaller secondary star.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/binary-star-system-composed-two-stars-68305255?src=L7RPZAG6A1sN5xbscHp_uw-1-8">Catmando / Shutterstock.com</a></span>
</figcaption>
</figure>
<p>When I started working with my advisor, <a href="http://www.astro.caltech.edu/%7Emansi/">Mansi Kasliwal</a>, as a new graduate student, I decided to study supernovae that quickly fade in brightness. Mining the database of events discovered by iPTF, I came across iPTF 14gqr, a quickly fading supernova that was discovered more than a year before but whose true physical nature remained mysterious. </p>
<p>The data were puzzling because our preliminary models suggested this supernova was caused by the death of a giant massive star, yet the explosion in itself was quite wimpy. It ejected only a fifth of the mass of the sun, while its energy was only a tenth of a typical supernova. Where was all the missing matter and energy?</p>
<p>The clues indicated that the exploding star must have been stripped of nearly all of its original mass before the explosion. But what could have stolen so much matter from this giant star? Perhaps an unseen binary companion? </p>
<p>I started reading up about rare binary star scenarios, when I first came across the idea of “ultra-stripped supernovae.” </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/7qRz2NvPFH4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">As two massive stars orbiting each other, the more massive star explodes first, leaving a rapidly spinning neutron star behind. This neutron star steals most of the material from its neighbor until the second star explodes in an ‘ultra-stripped’ supernova. What is left behind is a binary neutron star system.</span></figcaption>
</figure>
<h2>Ultra-stripped supernovae</h2>
<p>When a massive star has a dense and nearby binary companion star, the intense gravitational pull of the companion can rob its unsuspecting neighbor of nearly all its mass before it explodes – hence the term “ultra-stripped.” </p>
<p>The ultra-stripped supernova leaves behind a neutron star, a rapidly spinning dense stellar corpse containing a bit more than the mass of the sun crammed into a region the size of downtown Los Angeles. This neutron star is trapped in a tight orbit around its companion. The companion is possibly another neutron star, or even a white dwarf or a black hole that was formed from a massive star that died several million years before its companion.</p>
<p>Such binary systems have been an important field of astrophyiscal investigation for several decades. We have directly observed many such systems in our own galaxy with optical and radio telescopes. The first indirect detection of gravitational waves came from observations of a <a href="https://doi.org/10.1086/159690">double neutron star system</a>. More recently, <a href="http://doi.org/10.1117/12.2281024">the first merger of a double neutron star system</a> was detected both by advanced <a href="https://www.ligo.caltech.edu">LIGO </a>and in electromagnetic waves in 2017, giving astronomers unique insights into the workings of gravity and the origin of heavy elements in the universe. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/y8VDwGi0r0E?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Two dense neutron stars orbiting each other as they gradually spiral in and merge. The merger produces a ‘kilonova’ explosion, which was directly detected for the first time in 2017.</span></figcaption>
</figure>
<p>Yet, it has long remained a mystery how binary stars form. We know that neutron stars are formed in supernova explosions. But, in order to get binary neutron stars, you need a binary of two massive stars to begin. However, it requires a precise balance of forces to make sure that the binary neutron stars remain stable enough to survive the two violent explosions that create the system.</p>
<p>Several lines of indirect evidence suggest they are formed in a very rare class of weak ultra-stripped supernova explosions. But these faint explosions had so far escaped direct detection. This first observational evidence for an ultra-stripped supernova opens up an opportunity for understanding the formation of tight neutron star binary systems.</p>
<h2>Scanning the heavens for infant explosions</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/240278/original/file-20181011-154561-1e3vmth.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/240278/original/file-20181011-154561-1e3vmth.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/240278/original/file-20181011-154561-1e3vmth.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/240278/original/file-20181011-154561-1e3vmth.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/240278/original/file-20181011-154561-1e3vmth.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/240278/original/file-20181011-154561-1e3vmth.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/240278/original/file-20181011-154561-1e3vmth.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The iPTF used the 48-inch Samuel Oschin telescope at Palomar observatory.</span>
<span class="attribution"><a class="source" href="https://www.ptf.caltech.edu/system/avm_image_sqls/binaries/44/jpg_original/IMG_5704.jpg?1433985944">Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Our supernova was spotted during the intermediate <a href="https://www.ptf.caltech.edu/iptf">Palomar Transient Factory</a> (iPTF) survey. The automated iPTF survey used a large camera mounted on a 1-meter-sized telescope to take photos of the sky every night and scan for “new stars.” A search priority was hunting for infant supernovae and pinpointing the origin. </p>
<p>Whenever a new star is found, the survey robot immediately alerts on duty astronomers located in a completely different time zone to follow up. This strategy together with a global network of telescopes allowed us to catch several exploding stars in action and understand what they looked like just before they exploded. In fact, finding a rare ultra-stripped supernova moments after the explosion was a lucky coincidence!</p>
<p>This single event has provided us with the first insight into the mass and energy released in such explosions, the life cycle of massive stars, and the formation of binary stars. Yet, there is a lot more to be learned from a larger sample of these events. </p>
<p>With the <a href="https://www.ztf.caltech.edu">Zwicky Transient Facilty</a>– the successor of iPTF that can scan the skies 10 times faster – and a global network of telescopes called <a href="http://growth.caltech.edu">GROWTH</a>, we hope to witness more ultra-stripped explosions, beginning a new episode in our understanding of these unique star systems.</p><img src="https://counter.theconversation.com/content/104726/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kishalay De 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>A massive star, with a radius 500 times that of our sun, exploded. But the supernova fizzled – it was weak and dim. Figuring out what went wrong led to insights about how rare binary star systems form.Kishalay De, Graduate student of Astronomy, California Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/952072018-06-13T17:21:48Z2018-06-13T17:21:48ZShort-term changes in Antarctica’s ice shelves are key to predicting their long-term fate<figure><img src="https://images.theconversation.com/files/222991/original/file-20180613-32347-12ej8ho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The northeast edge of the Venable Ice Shelf, near Antarctica's Allison Peninsula.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/H84yYt">NASA/John Sonntag</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Antarctica’s ice sheet contains enough ice to raise global sea levels by around 180 feet if it all melted. But dramatic, eye-catching changes to Antarctica’s floating ice shelves, such as calving icebergs, are often highlighted in the news without a sense of long-term context or a clear connection to what is causing the changes. </p>
<p>Antarctica is <a href="https://theconversation.com/cold-and-calculating-what-the-two-different-types-of-ice-do-to-sea-levels-59996">losing land ice</a> at an accelerating rate, and current observations suggest it will become the <a href="https://www.nasa.gov/feature/goddard/2018/new-study-finds-sea-level-rise-accelerating">largest contributor to sea level rise</a> by the middle of this century. Understanding variations in the height of Antarctic ice shelves – the floating edges of the continent’s ice sheet – can tell us how and why Antarctica is changing, and what that could mean for future sea levels.</p>
<p>We study <a href="https://scholar.google.com/citations?user=JI_DpHwAAAAJ&hl=en">changes</a> in <a href="https://scholar.google.com/citations?user=J4DvU4oAAAAJ&hl=en">Antarctic</a> <a href="https://scholar.google.com/citations?user=ybHJBncAAAAJ&hl=en">ice</a> shelves, along with our colleague <a href="https://www.esr.org/staff/laurence-padman/">Laurie Padman</a> at <a href="https://www.esr.org/">Earth & Space Research</a>, a nonprofit institute in Seattle. One of us, <a href="https://scholar.google.com/citations?user=5prTIdoAAAAJ&hl=en">Helen Amanda Fricker</a>, contributed to two articles in a <a href="https://www.nature.com/collections/jwwltflrpn">special issue of the journal Nature</a> that brings together current understanding of the state of Antarctica. Here’s what we see happening.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/222802/original/file-20180612-112614-1nf8oyd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/222802/original/file-20180612-112614-1nf8oyd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/222802/original/file-20180612-112614-1nf8oyd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=501&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222802/original/file-20180612-112614-1nf8oyd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=501&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222802/original/file-20180612-112614-1nf8oyd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=501&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222802/original/file-20180612-112614-1nf8oyd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=629&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222802/original/file-20180612-112614-1nf8oyd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=629&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222802/original/file-20180612-112614-1nf8oyd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=629&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Antarctica’s major geographical features, including the West and East Antarctic ice sheets, the Antarctic Peninsula and some of the larger ice shelves around the continent’s edges.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Antarctica_major_geographical_features.jpg">NASA</a></span>
</figcaption>
</figure>
<h2>Ice shelves hold back the grounded ice</h2>
<p>Antarctic ice shelves provide mechanical support to hold back the flow of ice from the continent to the ocean, regulating the pace of mass loss from the enormous ice sheet. Scientists call this process “buttressing,” since it works in the same way that an <a href="https://www.britannica.com/technology/buttress-architecture">architectural buttress</a> prevents a building from collapsing. </p>
<p>Reducing the mass of an ice shelf does not contribute directly to sea level rise, since this ice is already floating on the ocean, but it promotes faster discharge of grounded ice, which increases sea level. To understand how Antarctic mass loss varies, we need to understand how ice shelves grow and shrink.</p>
<p>Ice shelves gain mass mainly through ice flowing from the continent and local snowfall on their surfaces. They lose mass primarily through melting by the ocean and by iceberg calving. </p>
<p>Antarctica has more than 300 ice shelves, and the net change in their mass is a delicate balance between gains and losses. Determining this balance requires understanding how ice, ocean, and atmosphere interact to drive changes around Antarctica. Climate change will alter the overall balance between gains and losses, and will determine the <a href="http://dx.doi.org/10.1038/s41586-018-0173-4">future of Antarctica’s ice loss</a>.</p>
<h2>The critical role of satellites</h2>
<p>Antarctica’s small ice shelves are roughly the area of small cities, and its largest is the size of Spain. The total ice-shelf area is around 1.5 million square kilometers (580,000 square miles), about as large as Mongolia. The only viable way to routinely monitor changes in their mass is with satellites. </p>
<p>Since the launch of <a href="https://landsat.usgs.gov/landsat-missions-timeline">Landsat 1</a> in 1972, satellite data have taught us a lot about the ice sheet, including its large-scale structure, surface properties and flow rates. A <a href="http://dx.doi.org/10.1038/s41586-018-0179-y">recent synthesis</a> combined 150 independent estimates of ice-sheet mass loss from satellite data and atmospheric models to show that the ice sheet is losing more mass to the ocean with every passing year. The largest changes have occurred in places where ice shelves have either thinned or collapsed.</p>
<p>Single satellite missions typically only last five to 10 years, but we can stitch together data from consecutive missions to increase the length of the record. This helps us separate long-term trends from natural climate variability and unravel processes that drive changes around the margins of Antarctica.</p>
<p>The European Space Agency (ESA) has launched four ice-observing satellites since 1992, carrying radar altimeters to precisely determine the distance between the satellite and the Earth’s surface beneath it. These data have now provided a continuous time series of variations in ice-shelf surface height since the early 1990s. Combining measured increases and decreases in surface height with the latest generation of climate models to infer how the atmosphere has changed, we can estimate the amount of mass an ice shelf can lose to the ocean.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/aSRxJVGlx7U?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Work by researchers at Scripps Institution of Oceanography reveals that strong El Niño events can cause significant ice loss in some Antarctic ice shelves.</span></figcaption>
</figure>
<h2>El Niño and La Niña affect ice shelves</h2>
<p>The Pacific Ocean sector of the Antarctic Ice Sheet is experiencing exceptionally high mass loss. This sector contains the rapidly changing Thwaites Glacier, which is the focus of a <a href="http://www.bbc.com/news/science-environment-43936372">new major research initiative</a> between the U.S. National Science Foundation and the United Kingdom’s National Environmental Research Council. </p>
<p>The 23-year altimeter record revealed <a href="https://doi.org/10.1038/s41561-017-0033-0">long-term mass loss in the Pacific sector ice shelves</a>. Further analysis of these data showed that in addition, the <a href="https://oceanservice.noaa.gov/facts/ninonina.html">El Niño/Southern Oscillation (ENSO)</a> – a periodic variation in sea surface temperatures and pressure over the tropical eastern Pacific Ocean – caused additional height change fluctuations. </p>
<p>Strong El Niño events, which typically bring warmer ocean waters and increase precipitation, increase snowfall over these ice shelves. But they also increase ocean-driven melting, removing ice from the ice-shelf base. Since snow is less dense than solid ice, mass lost through melting exceeds that added by snowfall. The result is that total ice-shelf mass, and hence its buttressing capability, actually decreases during El Niño events even though the height of the ice shelf may increase. </p>
<p>The opposite occurs during La Niñas, the counter to El Niño, where tropical ocean waters cool. Scientists expect that total precipitation and the <a href="https://doi.org/10.1038/nclimate2100">frequency of extreme ENSO events will increase as Earth’s atmosphere warms</a>, which implies that yearly fluctuations of ice shelf thickness and mass will also increase.</p>
<h2>Atmospheric conditions affect the Antarctic Peninsula</h2>
<p>A region further north in Antarctica, the Antarctic Peninsula, has experienced <a href="https://nsidc.org/news/newsroom/larsen_B/2002.html">startling changes over the past three decades</a>. Here several ice shelves have catastrophically collapsed due to warming in the atmosphere. Scientists see this as a canary in the coal mine: Similar warming events could drive the collapse of more southern ice shelves, which can play a larger role in future sea level rise. </p>
<p>Extensive press coverage of the 2017 calving of a <a href="https://www.youtube.com/watch?v=8Aw0kHAnY28">Delaware-sized iceberg</a> from Larsen C Ice Shelf has aggravated such concerns. However, in a recent study we showed that the height of the remaining Antarctic Peninsula ice shelves across the region has <a href="https://doi.org/10.1002/2017GL076652">increased since 2009</a>. Using atmospheric models backed up by field observations, we connected this height recovery to a regional cooling that persisted for several years and reduced summertime surface melting. The large calving event was likely a normal mass loss process, similar to a <a href="https://www.tandfonline.com/doi/abs/10.1080/01431169508954407">larger event in 1986</a>. There is so far no clear indication that Larsen C is on the brink of collapse.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/222800/original/file-20180612-112599-s3do2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/222800/original/file-20180612-112599-s3do2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/222800/original/file-20180612-112599-s3do2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=264&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222800/original/file-20180612-112599-s3do2q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=264&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222800/original/file-20180612-112599-s3do2q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=264&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222800/original/file-20180612-112599-s3do2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=332&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222800/original/file-20180612-112599-s3do2q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=332&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222800/original/file-20180612-112599-s3do2q.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=332&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Height changes observed over Larsen C Ice Shelf from Four European Space Agency satellites, one NASA satellite and an extensive airborne survey from NASA’s Operation IceBridge.</span>
<span class="attribution"><span class="source">Helen Fricker</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The role of the atmosphere is only part of this story. After removing the effect of higher air temperatures, we found that the ocean continued to melt the ice shelves’ bases at a rate that tipped the scales toward net mass loss. In fact, we found that the atmosphere recently played a stabilizing role while the ocean exerts a continuing destabilizing influence, highlighting the complex interplay between the atmosphere, ice and ocean around Antarctica.</p>
<h2>New satellites will provide more insight</h2>
<p>With existing data, scientists can begin to decode the intricacies of ice-shelf evolution to improve our understanding of what is influencing ice-shelf mass changes and stability. </p>
<p>Satellites have shown that the ice shelves are shrinking overall due to increased ocean-induced melting. In addition to the overall trend, signals corresponding to atmospheric and oceanic processes are becoming apparent, such as influences from El Niño and La Niña cycles in the tropics and local atmospheric changes. </p>
<p>As the satellite record lengthens with the launch of new polar-orbiting satellites like NASA’s <a href="https://icesat-2.gsfc.nasa.gov/">ICESat-2</a> in September 2018 and <a href="https://nisar.jpl.nasa.gov/">NISAR</a> in 2020, scientists expect to reach the point where we can confidently include these processes in models of ice-sheet response to climate changes, which will improve projections of future sea level rise.</p><img src="https://counter.theconversation.com/content/95207/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Helen Amanda Fricker receives funding from NASA and NSF.</span></em></p><p class="fine-print"><em><span>Fernando Paolo receives funding from NASA. </span></em></p><p class="fine-print"><em><span>Matthew Siegfried receives funding from NSF and NASA. </span></em></p><p class="fine-print"><em><span>Susheel Adusumilli receives funding from NASA. </span></em></p>Last summer one of Antarctica’s floating ice shelves calved an iceberg the size of Delaware – but scientists say other less dramatic changes reveal more about how and why Antarctica is changing.Helen Amanda Fricker, Professor, Scripps Institution of Oceanography, University of California, San DiegoFernando Paolo, Postdoctoral Scholar, Jet Propulsion Laboratory, California Institute of TechnologyMatthew Siegfried, Postdoctoral Fellow, Stanford University, Stanford UniversitySusheel Adusumilli, Graduate Student Researcher, University of California, San DiegoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/462202015-08-20T04:31:37Z2015-08-20T04:31:37ZWhy applying a gender lens is key to addressing Africa’s challenges<figure><img src="https://images.theconversation.com/files/92401/original/image-20150819-10832-cv9643.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Women should have access to high-level policy positions so that their input and voices are heard. </span> <span class="attribution"><span class="source">shutterstock</span></span></figcaption></figure><p>A report on the <a href="http://www.cdc.gov/vhf/ebola/about.html">Ebola outbreak</a> in <a href="http://answersafrica.com/west-african-countries-list.html">West Africa</a> in early 2015 caught my attention.</p>
<p>Being sensitive to gender issues, I was amazed that I had missed the gender dimension of this public health crisis. An alert from a global group that <a href="http://interagencystandingcommittee.org/node/2109">co-ordinates humanitarian action</a> put the crisis in context:</p>
<blockquote>
<p>… cultural and traditional practices in West Africa have the potential to greatly increase the exposure of women to the risk of Ebola (including women’s role as professional health workers, as care-givers in the household and in the preparation of dead bodies for burial).</p>
<p>This showed that, irrespective of the male/female ratio of xd cases, any strategies to stem the epidemic require a gender nuanced approach that addresses the differing needs, interests and vulner abilities of the women, men, boys and girls in the affected countries.</p>
</blockquote>
<p>This example reminds one that no matter how gender aware one is, there must be systematic approaches to raising issues of a gender dimension, such as in <a href="http://www.scidev.net/global/gender/practical-guide/gender-science-reporting-women-men.html">reporting</a>. This is also true in research and innovation, policy-making and implementation. </p>
<p>The right questions must be asked and close attention paid to the realities. In agriculture, do men and women in southern Africa cultivate the same crops, enjoy the same roles in farming, and have access to credit, markets, extension workers and research support?</p>
<p>In medicine, are the differences of women and men in genetics, physiology and the way that diseases present or spread taken into account? This could be in research, treatment and in training biomedical researchers and health care providers. Is data from research collected, analysed and reported in sex disaggregated ways?</p>
<p>Are the roles of women and men the same when viewed in terms of water and natural resources management and use, health decision making, energy use, protecting biodiversity, food security and nutrition?</p>
<p>When the answer is no, separate gender assessments are needed, and likely different policies as well.</p>
<p>There is an <a href="http://genderedinnovations.stanford.edu/">active base</a> of scholars considering issues of gender assessment in science, engineering health and medicine and environment. But the extent to which such studies influence government decision-making is not clear. </p>
<p>For example, women play a critical role in agriculture and food security in sub-Saharan Africa. Although gender differences in agriculture have been <a href="http://siteresources.worldbank.org/INTGENAGRLIVSOUBOOK/Resources/CompleteBook.pdf">well documented</a>, many agricultural policies and strategies have limited provision for gender-based approaches in their implementation. This has been recognised by the <a href="http://summits.au.int/en/25thsummit/events/second-african-union-high-level-panel-gender-equality-women-s-empowerment">African Union’s</a> high-level panel on gender equality and women’s empowerment. </p>
<h2>What does it mean to apply a gender lens?</h2>
<p>Meaningful scorecards to collect or report data must be maintained so that one can assess how much women and men benefit from policies and actions taken. </p>
<p>Some countries – for example India and Austria – have moved to gender budgeting. The European Commission already collects and publishes disaggregated <a href="http://www.science-metrix.com/en/publications/reports/she-figures-2015-leaflet">data</a>. Having this information helps decision-making and shows where interventions may be required. </p>
<p>Applying a gender lens means focusing on the science, technology and innovation dimensions. They intersect and interact with the gender dimension of particular goals. It also means considering how innovations and inventions are created. Are they appropriately designed to serve the needs of the women or men who would use them? An example would be designing seat belts that can work effectively and safely for pregnant women. </p>
<p>In keeping with this philosophy, the US National Institutes of Health (NIH), for example, has recently taken a major step in relation to research after 15 years of lobbying by gender organisations. Its 2017 <a href="http://www.nih.gov/news/health/sep2014/od-23.htm">grant applications</a> will make consideration of “sex as a biological variable that must be addressed in the research strategy section” of proposals for funding affecting animal studies that inform clinical research. </p>
<p>The NIH believes that this would encourage researchers to study females and males, and become a catalyst for considering sex as a fundamental variable in research. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/92402/original/image-20150819-10879-1lnvpny.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/92402/original/image-20150819-10879-1lnvpny.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=385&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92402/original/image-20150819-10879-1lnvpny.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=385&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92402/original/image-20150819-10879-1lnvpny.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=385&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92402/original/image-20150819-10879-1lnvpny.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=484&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92402/original/image-20150819-10879-1lnvpny.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=484&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92402/original/image-20150819-10879-1lnvpny.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=484&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Applying a gender lens in times of crisis, such as the ebola outbreak, should not be ignored.</span>
<span class="attribution"><span class="source">Reuters</span></span>
</figcaption>
</figure>
<p>The NIH said there was a current over-reliance on male subjects in preclinical research. This often obscures key findings related to gender that could guide later human studies. Such a progressive approach, which gender lobbyists have campaigned for, will result in greater awareness of the need to study both sexes, according to the NIH. </p>
<p>Today, women are as likely as men to receive PhDs in the life sciences. There is also parity among those completing medical schools. But their presence alone does not push the research agenda.</p>
<p>The intersection of gender, science, technology and innovation within the development landscape has been explored <a href="http://www.un.org/en/ecosoc/newfunct/pdf13/sti_unesco.pdf">within the UN structure</a> for decades. </p>
<p>In 2011, the United Nations Conference on Trade and Development published a <a href="http://unctad.org/en/Docs/dtlstict2011d5_en.pdf">document</a> laying out overarching concepts along with specific examples of implementing a gender dimension in <a href="http://unctad.org/en/Docs/dtlstict2011d5_en.pdf">development initiatives</a>.</p>
<p>Much of the current efforts in supporting the work of the United Nations Commission on Science & Technology for Development has turned its focus from the Millennium Development Goals to the Sustainable Development Goals. While developing a global roadmap for reducing poverty and promoting equality, it is now more accepted that the links between gender, science, technology and innovation have a prominent role to play. </p>
<p>This is a powerful and positive development. But these efforts continue to fall short because gender is ignored or compartmentalised rather than interwoven throughout. It is not clear if this is due to lack of knowledge or lack of political will.</p>
<p>In supporting this work globally, the Gender Advisory Board has partnered with GenderInSITE. While there is scholarly work to be done, the policy strategies cannot be ignored. Therefore, it is critical that women have access to high-level policy positions so that their inputs and voices are heard.</p><img src="https://counter.theconversation.com/content/46220/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shirley Malcom 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>Despite ongoing efforts, achieving gender equality struggles because it is ignored or compartmentalised rather than interwoven throughout.Shirley Malcom, Head of Education and Human Resources Programs at American Association for the Advancement of Science (AAAS); Trustee, California Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/290602014-07-11T05:14:46Z2014-07-11T05:14:46ZBrain scans could be used to predict financial bubbles<figure><img src="https://images.theconversation.com/files/53557/original/hx53p5qt-1405008740.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Experimenting with bubbles.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/indigoskies/6300407679/sizes/l/in/photolist-aAKeGB-886rvQ-SG7Pk-xkVMe-579Ekx-57DHKZ-69GF9Z-7SXf3y-62c92d-57QoFW-5s7aiM-5nD2z3-57Qffh-9sAGrL-7Tb472-5sRcRY-7NsbFR-9nE5Mj-aqR3xg-5keeS7-9wocFa-67wxPD-ax5kZB-5HFPPa-4c7gBw-5y3Msw-6bfEMx-56Nyo1-adZCzo-9uQ7t1-5zRqZc-5Zhm46-4rBUES-f5e8h8-5vxVyF-569SS9-7fyBqL-dEs1XP-3eu4RS-51sAnY-odHUC-7LNzrf-7LJCtR-7LNuRC-7LJxiF-7LJxXZ-7LJyHH-7LNxgm-f7iqBW-ahGKoA/">Flickr/Indigo Skies Photography</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Some shares have new owners <a href="http://www.nytimes.com/2009/07/24/business/24trading.html?_r=5&adxnnl=1&ref=businessl&adxnnlx=1404997277-6YyZRX2ab50Dz1+NwIfJfQ">every second</a>. Today much of the buying and selling is done by computers, but some still rely on human intuition – the gut feeling of the experienced trader.</p>
<p>“Nobody can predict the market, but traders are expected to,” Richard Taffler, professor of finance at the University of Warwick said. “This creates anxiety.” So emotions must play an important role in driving financial markets. Understanding <a href="https://theconversation.com/neuroscience-may-help-us-understand-financial-bubbles-18382">what happens in the brains of traders</a> as prices move up and down could possibly tell us something about the markets future developments.</p>
<p>In a study published in the <a href="http://link/">Proceedings of the National Academy of Sciences</a>, Alec Smith at the California Institute of Technology and his colleagues conducted group-behaviour experiments. For each of the 16 rounds, they had between 11 and 23 students, who played a game that simulated a market situation. For every round of the game, Smith monitored the brain activity of three of the participants with functional magnetic resonance imaging (fMRI), which highlights parts of the brain based upon increase or decrease in activity of that region.</p>
<p>The market game starts with an asset at an arbitrary value. As the market develops over time the asset price increases. The experiment is setup such that a market bubble always forms, and then it bursts causing the asset to return to the initial value in a very short time.</p>
<p>Smith and his colleagues found that activity in a brain region called the “nucleus accumbens” (NA) correlates the market price – so if the price goes up, NA gets more active. “This brain region was previously associated with emotions, fear and pleasure,” Smith said. “It makes sense we find this region active.” </p>
<p>In the next step the researchers compared the participants who, at the end of the market game, turned out to be high or low earners to relate the brain activity to a specific trading outcome.</p>
<p>The difference is that low earners buy around peak price, while high earners sell their shares around peak price. The researchers suspected the cause for this behaviour may lie in the “anterior insular cortex”, located behind the forehead. The insular cortex is active during bodily discomfort – when you feel pain, anxiety or disgust. The anterior region is also activated by financial risk. </p>
<p>Smith found that around the time when prices are about to hit the peak (that is, a bubble is starting to form), which is also the point where decisions of high and low earners start to diverge, insular activity increases in high earners, but shows no change in low earners.</p>
<p>The upshot is, if you could measure the brain activity underlying certain emotions of an active and successful trader in a critical market situation, you could predict how prices may change. “We think that irrational exuberance is likely to play part in price bubbles”, Smith said, explaining why they focused on the brain region involved in a lot of emotional processing. </p>
<p>Richard Taffler, professor of finance from the University of Warwick, isn’t sure that such predictions are possible. “It is not clear how we get from undergraduate students, in a confined laboratory environment, without a real potential of loss to a real world market situation,” he said.</p>
<p>Alec insists the behavioural game is not too much of an abstraction from reality and we can use it learn about the principles of price bubbles. Instead, Taffler proposes that we should observe and learn from behaviour and price development in real-world market bubbles to capture the complexity of the market. </p>
<p>“It is not clear that you can use the traditional scientific approach to analyse social behaviour”, Taffler said.</p>
<p>On the other hand, the experimental setup does not only give insight into market research, they could help understand other cases in which human groups badly judge the value of actions or events. The next step is probably not to connect every Wall Street trader to an fMRI. This study is only a proof of principle. And anyway, fMRI scanners are too expensive, even for bankers’ deep pockets.</p><img src="https://counter.theconversation.com/content/29060/count.gif" alt="The Conversation" width="1" height="1" />
Some shares have new owners every second. Today much of the buying and selling is done by computers, but some still rely on human intuition – the gut feeling of the experienced trader. “Nobody can predict…Sylvia Tippmann, Assistant Editor Science + DataLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/267292014-05-15T14:45:14Z2014-05-15T14:45:14ZJellyfish are the most energy efficient swimmers, new metric confirms<figure><img src="https://images.theconversation.com/files/48536/original/5f72rzp5-1400101456.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Elegant and efficient.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/andrewmorrell/373291552">andrewmorrell</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Even though a blue whale is much heavier than a tuna, the mammal consumes less energy per unit weight than the fish when they travel the same distance. For years, these <a href="http://www.sciencemag.org/content/177/4045/222.extract">sort of comparisons</a> have dominated our understanding of the energy efficiency of animal movement, which is important for designing vehicles inspired by nature, such as underwater drones.</p>
<p>But Neelesh Patankar, professor of mechanical engineering at Northwestern University, believes that this measure has only limited benefit. Instead, with his colleagues, he has come up with a new measure that allows comparison of animals as small as bees or zebrafish with animals as large as albatrosses or blue whales.</p>
<p>The new measure has two implications. First, among those that have typical swimming and flying actions, which includes most fish and all birds, each animal is as energy efficient as it can be. This means that, given their size and shape, each animal is able to spend the least amount of energy to move the most distance. Second, this measure confirms a previous finding that jellyfish are unusually energy efficient, beating all the thousands of fish and birds Patankar studied.</p>
<p>“Put another way, a whale and a tuna are equally energy efficient,” Patankar said. “Except jellyfish, which have an unusual action that makes them more efficient.”</p>
<h2>A new measure</h2>
<p>To understand why jellyfish are special, we need to first answer the question why we need a new measure for energy efficiency. Patankar offers an analogy: if there are two cars that are of equal weight, would you expect them to have the same mileage? Just as in cars, animals’ motion will vary based on factors other than their weight. </p>
<p>John Dabiri, professor of aeronautics and bioengineering at California Institute of Technology, said, “It is not immediately obvious how to compare the swimming efficiency of a bacterium and a blue whale, for example, but Patankar and colleagues have developed one.”</p>
<p>To make the comparison, Patankar borrowed from a well-known concept in physics called the Reynolds number, which explains the relationship between two forces that act on any body that is moving through a fluid. The first is viscous force, which is, crudely put, the push you feel when you put your hand out of a moving vehicle. The second is inertial forces, which is the tendency of a moving object to keep moving (or that of a stationary object to remain stationary). </p>
<p>Depending on the size of a body and the speed at which it travels, the body faces either a low Reynolds number, where the forces acting on a body are mostly viscous forces, or a high Reynolds number, where inertial forces dominate. This creates a natural difference in how much energy is spent countering these forces.</p>
<p>Reynolds number was developed to look at the aerodynamics of stiff bodies, such as aeroplanes and ships. But Patankar reckoned he could use it to help compare animals of different sizes. He gathered data from thousands of birds and fish to come up with a metric called the energy-consumption coefficient, which he has described in the <a href="http://dx.doi.org/10.1073/pnas.1310544111">Proceedings of the National Academy of Sciences</a>. Using it, he found that all the animals he looked at (except jellyfish) are as energy-efficient as they can be.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/48531/original/wmdq3pgz-1400100283.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/48531/original/wmdq3pgz-1400100283.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=527&fit=crop&dpr=1 600w, https://images.theconversation.com/files/48531/original/wmdq3pgz-1400100283.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=527&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/48531/original/wmdq3pgz-1400100283.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=527&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/48531/original/wmdq3pgz-1400100283.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=662&fit=crop&dpr=1 754w, https://images.theconversation.com/files/48531/original/wmdq3pgz-1400100283.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=662&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/48531/original/wmdq3pgz-1400100283.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=662&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Note that Y-axis is for energy-consumption coefficient, not for energy efficiency.</span>
<span class="attribution"><span class="source">Rahul Bale</span></span>
</figcaption>
</figure>
<p>“The idea that animals are tuned for energy-efficient locomotion is not surprising, but the authors have devised a fresh approach to the issue of how to compare the efficiencies of different animals,” Dabiri said.</p>
<p>Patankar finds, as he had hoped, that small animals find themselves in low Reynolds number situations, and large animals find themselves in high Reynolds number situations. This means they expend energies differently, which is what Patankar’s coefficient represents. Using the coefficient, one can compare the energy efficiency of bodies weighing few grams to many tonnes.</p>
<p>The coefficient also indicates that animals that fly are less energy-efficient than those that swim. This, Patankar thinks, must be because those in flight have to expend more energy to counteract gravity than those in water.</p>
<h2>Jelly’s secrets</h2>
<p>While working on the energy-consumption coefficient, he came across <a href="http://dx.doi.org/10.1073/pnas.1306983110">recent work</a> done by Dabiri and his colleagues which showed that the unique contract-and-relax action of jellyfish allowed it to recapture some of the energy it spends on motion. This means a jellyfish can travel a lot more distance for the same amount of energy spent by other animals adjusted for its weight and size.</p>
<p>When Patankar used Dabiri’s data and plotted it on his energy-consumption coefficient chart, he found that the only animals that were more energy efficient than he had predicted were jellyfish. </p>
<p>“We found that each swimming or flying animal can spend all the energy it has at its disposal. However, our coefficient is a fair way to conclusively show that indeed jellyfish are more efficient,” Patankar said.</p>
<p>Dabiri is already working on exploiting jellyfish propulsion. However, he thinks that, apart from providing a new metric to compare different types of animals on the energy-efficiency scale, Patankar’s measure could be a used for evaluating the performance of aerial and underwater drones that are being developed, especially those with designs that are inspired by flying and swimming animals.</p><img src="https://counter.theconversation.com/content/26729/count.gif" alt="The Conversation" width="1" height="1" />
Even though a blue whale is much heavier than a tuna, the mammal consumes less energy per unit weight than the fish when they travel the same distance. For years, these sort of comparisons have dominated…Akshat Rathi, Former Science and Data Editor, The ConversationLicensed as Creative Commons – attribution, no derivatives.