tag:theconversation.com,2011:/africa/topics/tropical-cyclones-10454/articles
Tropical cyclones – The Conversation
2024-01-09T19:17:25Z
tag:theconversation.com,2011:article/220672
2024-01-09T19:17:25Z
2024-01-09T19:17:25Z
A heatwave in Antarctica totally blew the minds of scientists. They set out to decipher it – and here are the results
<figure><img src="https://images.theconversation.com/files/568365/original/file-20240109-23-ijfvqy.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C3941%2C970&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source"> DM Bergstrom</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Climate scientists don’t like surprises. It means our deep understanding of how the climate works isn’t quite as complete as we need. But unfortunately, as climate change worsens, surprises and unprecedented events keep happening.</p>
<p>In March 2022, Antarctica experienced an extraordinary heatwave. Large swathes of East Antarctica experienced temperatures up to 40°C (72°F) above normal, shattering temperature records. It was the <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL104910">most intense</a> heatwave ever recorded anywhere in the world.</p>
<p>So shocking and rare was the event, it blew the minds of the Antarctic climate science community. A major global research project was launched to unravel the reasons behind it and the damage it caused. A team of 54 researchers, including me, delved into the intricacies of the phenomenon. The team was led by Swiss climatologist Jonathan Wille, and involved experts from 14 countries. The collaboration resulted in two <a href="https://journals.ametsoc.org/view/journals/clim/37/3/JCLI-D-23-0175.1.xml#:%7E:text=At%20the%20peak%20of%20the,possible%20under%20future%20climate%20projections.">groundbreaking papers</a> published today.</p>
<p>The results are alarming. But they provide scientists a deeper understanding of the links between the tropics and Antarctica – and give the global community a chance to prepare for what a warmer world may bring.</p>
<h2>Head-hurting complexity</h2>
<p>The papers tell a complex story that began half a world away from Antarctica. Under <a href="http://www.bom.gov.au/climate/updates/articles/a020.shtml">La Niña conditions</a>, tropical heat near Indonesia poured into the skies above the Indian Ocean. At the same time, repeated weather troughs pulsing eastwards were generating from southern Africa. These factors combined into a late, Indian Ocean tropical cyclone season.</p>
<p>Between late February and late March 2022, 12 tropical storms had brewed. Five storms revved up to become tropical cyclones, and heat and moisture from some of these cyclones mashed together. A meandering jet stream picked up this air and swiftly transported it vast distances across the planet to Antarctica.</p>
<p>Below Australia, this jet stream also contributed to blocking the eastward passage of a high pressure system. When the tropical air collided with this so-called “blocking high”, it caused the most intense atmospheric river ever observed over East Antarctica. This propelled the tropical heat and moisture southward into the heart of the Antarctic continent. </p>
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Read more:
<a href="https://theconversation.com/like-rivers-in-the-sky-the-weather-system-bringing-floods-to-queensland-will-become-more-likely-under-climate-change-176711">Like rivers in the sky: the weather system bringing floods to Queensland will become more likely under climate change</a>
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<h2>Luck was on Antarctica’s side</h2>
<p>The event caused the vulnerable Conger Ice Shelf to <a href="https://theconversation.com/conger-ice-shelf-has-collapsed-what-you-need-to-know-according-to-experts-180077">finally collapse</a>. But the impacts were otherwise not as bad as they could have been. That’s because the heatwave struck in March, the month when Antarctica transitions to its dark, extremely cold winter. If a future heatwave arrives in summer – which is more likely under climate change – the results could be catastrophic.</p>
<p>Despite the heatwave, most inland temperatures stayed below zero. The spike included a new all-time temperature high of -9.4°C (15.1°F) on March 18 near Antarctica’s Concordia Research Station. To understand the immensity of this, consider that the previous March maximum temperature at this location was -27.6°C (-17.68°F). At the heatwave’s peak, 3.3 million square kilometres in East Antarctica – an area about the size of India – was affected by the heatwave.</p>
<p>The impacts included widespread rain and surface melt along coastal areas. But inland, the tropical moisture fell as snow – lots and lots of snow. Interestingly, the weight of the snow offset ice loss in Antarctica for the year. This delivered a temporary reprieve from Antarctica’s contribution to global sea-level rise.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568364/original/file-20240109-25-o9q0sw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An ice shelf before (left) and after (right) a collapse." src="https://images.theconversation.com/files/568364/original/file-20240109-25-o9q0sw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568364/original/file-20240109-25-o9q0sw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568364/original/file-20240109-25-o9q0sw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568364/original/file-20240109-25-o9q0sw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568364/original/file-20240109-25-o9q0sw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=478&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568364/original/file-20240109-25-o9q0sw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=478&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568364/original/file-20240109-25-o9q0sw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=478&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">These images, acquired by the Copernicus Sentinel-2 satellites on January 30 2022 (left) and March 21 2022 (right), show the Conger ice shelf before and after the collapse, which was triggered by a shocking heatwave.</span>
<span class="attribution"><a class="source" href="https://www.copernicus.eu/en/media/image-day-gallery/collapse-conger-ice-shelf">European Union, Copernicus Sentinel-2 satellite imagery</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Learning from the results</h2>
<p>So what are the lessons here? Let’s begin with the nice bit. The study was made possible by international collaboration across Antarctica’s scientific community, including the open sharing of datasets. This collaboration is a touchstone of the Antarctic Treaty. It serves as a testament to the significance of peaceful international cooperation and should be celebrated. </p>
<p>Less heartwarmingly, the extraordinary heatwave shows how compounding weather events in the tropics can affect the vast Antarctic ice sheet. The heatwave further reduced the extent of sea ice, which was already at record lows. This loss of sea ice was exacerbated this <a href="https://theconversation.com/devastatingly-low-antarctic-sea-ice-may-be-the-new-abnormal-study-warns-212376">year</a> resulting in the lowest summer and winter sea ice ever recorded. It shows how disturbances in one year can compound in later years.</p>
<p>The event also demonstrated how tropical heat can trigger the collapse of unstable ice shelves. Floating ice shelves don’t contribute to global sea-level rise, but they acts as dams to the <a href="https://theconversation.com/antarctic-tipping-points-the-irreversible-changes-to-come-if-we-fail-to-keep-warming-below-2-207410">ice sheets behind them</a>, which do contribute.</p>
<p>This research calculated that such temperature anomalies occur in Antarctica about once a century, but concluded that under climate change, they will occur more frequently. </p>
<p>The findings enable the global community to improve its planning for various scenarios. For example, if a heatwave of similar magnitude hit in summer, how much ice melt would there be? If an atmospheric river hit the <a href="https://theconversation.com/antarcticas-doomsday-glacier-how-its-collapse-could-trigger-global-floods-and-swallow-islands-173940">Doomsday glacier</a> in the West Antarctic, what rate of sea level rise would that trigger? And how can governments across the world <a href="https://theconversation.com/who-moves-and-who-pays-managed-retreat-is-hard-but-lessons-from-the-past-can-guide-us-196038">prepare coastal communities</a> for sea level rise greater than currently calculated?</p>
<p>This research contributes another piece to the complex jigsaw puzzle of climate change. And reminds us all, that delays to action on climate change will raise the price we pay.</p>
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Read more:
<a href="https://theconversation.com/record-smashing-heatwaves-are-hitting-antarctica-and-the-arctic-simultaneously-heres-whats-driving-them-and-how-theyll-impact-wildlife-179659">Record-smashing heatwaves are hitting Antarctica and the Arctic simultaneously. Here’s what’s driving them, and how they’ll impact wildlife</a>
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<p><em>This article has been amended to correct an error in converting a 40°C temperature difference from Celsius to Fahrenheit.</em></p><img src="https://counter.theconversation.com/content/220672/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dana M Bergstrom past position was at the Australian Antarctic Division. She is affiliated with the Pure Antarctic Foundation, a groups of scientists and artists interesting in communication science and knowledge to the broader community.</span></em></p>
A heatwave in 2022 redefined scientific expectations of the Antarctic climate. Now the global community must prepare for what a warmer world may bring.
Dana M Bergstrom, Honorary Senior Fellow, University of Wollongong
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/206920
2023-06-20T18:25:21Z
2023-06-20T18:25:21Z
Hurricanes push heat deeper into the ocean than scientists realized, boosting long-term ocean warming, new research shows
<figure><img src="https://images.theconversation.com/files/532027/original/file-20230614-23-paym8a.png?ixlib=rb-1.1.0&rect=1182%2C376%2C2629%2C1747&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Satellite data illustrates the heat signature of Hurricane Maria above warm surface water in 2017.</span> <span class="attribution"><a class="source" href="https://climate.nasa.gov/explore/ask-nasa-climate/3181/a-force-of-nature-hurricanes-in-a-changing-climate/">NASA</a></span></figcaption></figure><p>When a hurricane hits land, the destruction can be visible for years or even decades. Less obvious, but also powerful, is the effect hurricanes have on the oceans. </p>
<p>In a <a href="https://doi.org/10.1073/pnas.2301664120">recent study</a>, we show through real-time measurements that hurricanes don’t just churn water at the surface. They can also push heat deep into the ocean in ways that can lock it up for years and ultimately affect regions far from the storm.</p>
<p>Heat is the key component of this story. It has long been known that hurricanes <a href="https://www.whoi.edu/know-your-ocean/did-you-know/how-does-the-ocean-affect-storms/">gain their energy from warm sea surface temperatures</a>. This heat helps <a href="https://youtu.be/wPDoIrGUrEc">moist air near the ocean surface rise</a> like a hot air balloon and form clouds taller than Mount Everest. This is why hurricanes generally form in tropical regions.</p>
<p>What we discovered is that hurricanes ultimately help warm the ocean, too, by enhancing its ability to absorb and store heat. And that can have far-reaching consequences.</p>
<figure class="align-center ">
<img alt="Schematic showing the formation of a hurricane, which gains its energy from warm ocean surface water." src="https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=262&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=262&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=262&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=329&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=329&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=329&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">How hurricanes draw energy from the ocean’s heat.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Hurricane-en.svg">Kelvin Ma via Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>When hurricanes mix heat into the ocean, that heat doesn’t just resurface in the same place. We showed how underwater waves produced by the storm can push the heat <a href="https://doi.org/10.1073/pnas.2301664120">roughly four times deeper</a> than mixing alone, sending it to a depth where the heat is trapped far from the surface. From there, deep sea currents can transport it thousands of miles. A hurricane that travels across the western Pacific Ocean and hits the Philippines could end up supplying warm water that heats up the coast of Ecuador years later.</p>
<h2>At sea, looking for typhoons</h2>
<p>For two months in the fall of 2018, we lived aboard the research vessel Thomas G. Thompson to record how the Philippine Sea responded to changing weather patterns. As <a href="https://scholar.google.com/citations?user=c9pivSIAAAAJ&hl=en">ocean</a> <a href="https://scholar.google.com/citations?user=kAGkuGgAAAAJ&hl=en">scientists</a>, we study turbulent mixing in the ocean and hurricanes and other tropical storms that generate this turbulence.</p>
<p>Skies were clear and winds were calm during the first half of our experiment. But in the second half, three major typhoons – as hurricanes are known in this part of the world – stirred up the ocean. </p>
<figure class="align-right ">
<img alt="A photo of an instrument being lowered into the ocean. It's a long thin line with sensors attached." src="https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Microstructure profilers are used to measure ocean turbulence. This one is designed and built by the Ocean Mixing Group at Oregon State University.</span>
<span class="attribution"><span class="source">Sally Warner</span></span>
</figcaption>
</figure>
<p>That shift allowed us to directly compare the ocean’s motions with and without the influence of the storms. In particular, we were interested in learning how turbulence below the ocean surface was helping transfer heat down into the deep ocean.</p>
<p>We measure ocean turbulence with an instrument called a microstructure profiler, which free-falls nearly 1,000 feet (300 meters) and uses a probe similar to a phonograph needle to measure turbulent motions of the water. </p>
<h2>What happens when a hurricane comes through</h2>
<p>Imagine the tropical ocean before a hurricane passes over it. At the surface is a layer of warm water, warmer than 80 degrees Fahrenheit (27 degrees Celsius), that is heated by the sun and extends roughly 160 feet (50 meters) below the surface. Below it are layers of colder water. </p>
<p>The <a href="https://youtu.be/H5-ZW8sH9ws">temperature difference</a> between the layers keeps the waters separated and virtually unable to affect each other. You can think of it like the division between the oil and vinegar in an unshaken bottle of salad dressing.</p>
<p>As a hurricane passes over the tropical ocean, its strong winds help stir the boundaries between the water layers, much like someone shaking the bottle of salad dressing. In the process, cold deep water is mixed up from below and warm surface water is mixed downward. This causes surface temperatures to cool, allowing the ocean to absorb heat more efficiently than usual in the days after a hurricane.</p>
<p>For over two decades, scientists <a href="https://news.mit.edu/2010/hurricane-thermostate-0304">have debated</a> whether the warm waters that are mixed downward by hurricanes could heat ocean currents and thereby shape global climate patterns. At the heart of this question was whether hurricanes could pump heat deep enough so that it stays in the ocean for years.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Schematic with five stages showing the ocean's warm surface layer mixing during a hurricane, heat continuing to be pushed down after the hurricane passes and remaining there for months." src="https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=206&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=206&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=206&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=258&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=258&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=258&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">These illustrations show what happens to ocean heat before, during, after and many months after a hurricane passes over the ocean.</span>
<span class="attribution"><span class="source">Sally Warner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>By analyzing subsurface ocean measurements taken before and after three hurricanes, we found that underwater waves transport heat roughly four times deeper into the ocean than direct mixing during the hurricane. These waves, which are generated by the hurricane itself, transport the heat deep enough that it cannot be easily released back into the atmosphere.</p>
<h2>Implications of heat in the deep ocean</h2>
<p>Once this heat is picked up by large-scale ocean currents, it can be transported to distant parts of the ocean. </p>
<p>The heat injected by the typhoons we studied in the Philippine Sea may have flowed to the coasts of Ecuador or California, following current patterns that carry water from west to east across the equatorial Pacific. </p>
<p>At this point, the heat may be mixed back up to the surface by a combination of <a href="https://doi.org/10.1007/s10236-005-0115-1">shoaling currents</a>, <a href="https://oceanservice.noaa.gov/facts/upwelling.html">upwelling</a> and <a href="https://doi.org/10.1038/nature12363">turbulent mixing</a>. Once the heat is close to the surface again, it can warm the local climate and affect ecosystems. </p>
<p>For instance, coral reefs are particularly sensitive to extended periods of heat stress. El Niño events are the typical culprit behind <a href="https://doi.org/10.1016/B978-044451388-5/50020-5">coral bleaching in Ecuador</a>, but the excess heat from the hurricanes that we observed may contribute to stressed reefs and bleached coral far from where the storms appeared.</p>
<figure class="align-center ">
<img alt="Schools of striped tropical fish swim through a coral reef." src="https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=382&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=382&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=382&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=480&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=480&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=480&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Coral reefs are essential habitat for fish and other sea life, but they are threatened by rising ocean temperatures.</span>
<span class="attribution"><a class="source" href="https://www.noaa.gov/education/resource-collections/marine-life/coral-reef-ecosystems">James Watt via NOAA</a></span>
</figcaption>
</figure>
<p>It is also possible that the excess heat from hurricanes stays within the ocean for decades or more without returning to the surface. This would actually have a mitigating impact on climate change. </p>
<p>As hurricanes redistribute heat from the ocean surface to greater depths, they can help to slow down warming of the Earth’s atmosphere by keeping the heat sequestered in the ocean. </p>
<p>Scientists have long thought of hurricanes as extreme events fueled by ocean heat and shaped by the Earth’s climate. <a href="https://doi.org/10.1073/pnas.2301664120">Our findings</a>, published in the Proceedings of the National Academy of Sciences, add a new dimension to this problem by showing that the interactions go both ways — hurricanes themselves have the ability to heat up the ocean and shape the Earth’s climate.</p><img src="https://counter.theconversation.com/content/206920/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Noel Gutiérrez Brizuela receives funding from the Mexican Council for Science and Technology (CONACYT). </span></em></p><p class="fine-print"><em><span>Sally Warner has received funding from the National Science Foundation and the Office of Naval Research.</span></em></p>
Currents can carry that deep ocean heat hundreds of miles to surface again at distant shores.
Noel Gutiérrez Brizuela, Ph.D. Candidate in Physical Oceanography, University of California, San Diego
Sally Warner, Associate Professor of Climate Science, Brandeis University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/203835
2023-04-14T05:05:41Z
2023-04-14T05:05:41Z
Cyclone Ilsa just broke an Australian wind speed record. An expert explains why the science behind this is so complex
<figure><img src="https://images.theconversation.com/files/520985/original/file-20230414-16-vx1p2h.jpg?ixlib=rb-1.1.0&rect=0%2C241%2C4031%2C2444&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An anemometer.</span> <span class="attribution"><span class="source">Wattanasit Chunopas/Shutterstock</span></span></figcaption></figure><p>Tropical cyclone Ilsa has been downgraded to a category-three cyclone <a href="http://www.bom.gov.au/cgi-bin/wrap_fwo.pl?IDW24100.html">as it moves southeast through Western Australia</a>. The storm first made landfall as a category-five cyclone, passing near Port Hedland around midnight.</p>
<p>Ilsa smashed into the largely uninhabited Pilbara region (the country’s most <a href="http://www.bom.gov.au/cyclone/climatology/wa.shtml">cyclone-prone region</a>) at record-breaking speeds. It has delivered Australia’s highest ten-minute sustained wind speed record at landfall: about <a href="https://twitter.com/BOM_WA/status/1646513163763089412">218 kilometres per hour</a>. The previous record of 194km per hour came from tropical cyclone George in 2007. </p>
<p>So, does this new speed make Ilsa a particularly menacing disaster? The science of reporting on cyclone wind speeds is highly complex – and it can be easy to misconstrue the figures without some context. </p>
<h2>Record-breaking sustained wind speeds</h2>
<p>As Ilsa continues to move inland, it looks likely the storm will be further downgraded before it passes into the Northern Territory – and potentially over Alice Springs – later today and tomorrow. </p>
<p>Ilsa made landfall about 100km north of Port Hedland, which hosts <a href="https://www.tradewindsnews.com/bulkers/port-hedland-iron-ore-export-capacity-to-be-raised-25-to-660m-tonnes/2-1-1166793?zephr_sso_ott=BVpwYn">the world’s largest export site for iron ore</a>. But a red alert prompted most vessels to be moved farther west in advance, so it only caused minor destruction. </p>
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<a href="https://images.theconversation.com/files/520984/original/file-20230414-20-xz4v7x.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/520984/original/file-20230414-20-xz4v7x.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520984/original/file-20230414-20-xz4v7x.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520984/original/file-20230414-20-xz4v7x.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520984/original/file-20230414-20-xz4v7x.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520984/original/file-20230414-20-xz4v7x.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520984/original/file-20230414-20-xz4v7x.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520984/original/file-20230414-20-xz4v7x.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">This Bureau of Meteorology satellite image shows Ilsa at 10:30am AEST, on Thursday.</span>
<span class="attribution"><span class="source">BoM</span></span>
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</figure>
<p>Analysis by James Knight at Aon’s Reinsurance Solutions expects in general it will cause only minor damage due to the remoteness of where it has hit. </p>
<p>Apart from the ten-minute sustained record mentioned above, Ilsa had a one-minute sustained record of 240km per hour, and a three-second sustained record of 295km per hour. </p>
<p>It’s usually the latter, more intense gusts, that cause the most damage in tropical cyclone events. When it comes to making potential damage assessment for insurance purposes, firms will often model damage associated with a three-second sustained wind speed.</p>
<p>But there are several challenges that come with recording and making predictions about cyclone wind speeds.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/cyclone-freddy-was-the-most-energetic-storm-on-record-is-it-a-harbinger-of-things-to-come-201771">Cyclone Freddy was the most energetic storm on record. Is it a harbinger of things to come?</a>
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</em>
</p>
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<h2>How are tropical cyclone winds recorded?</h2>
<p>The Bureau of Meteorology maintains a <a href="http://www.bom.gov.au/climate/how/newproducts/IDChw.shtml">national wind recording database</a>, which uses instruments called anemometers. These measure wind speeds at locations across the country, and are often placed in flat areas, such as near airports.</p>
<p>Their specific placement is very important, because wind can change form as it moves over and through certain types of terrain. </p>
<p>Generally, when we report wind speed we’re referring to atmospheric wind gust, or wind speeds at least ten metres off the ground, which we also call “open terrain” wind speed. </p>
<p>However, wind passing closer to the ground, where the topography varies, will often be higher than winds passing directly above. Wind will speed up, for instance, if it’s squeezed between two hills. </p>
<p>We know from post-cyclone damage surveys that wind speeds can vary significantly from one side of a hill to another. So aspect and slope are very important.</p>
<p>As far as disaster modelling goes, this is no small issue as it can skew recordings. It’s quite possible there would have been wind gusts from Ilsa that exceeded what has been reported so far. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1646513163763089412"}"></div></p>
<p>Australia lacks a sufficiently dense network of anemometers set up for long-term testing. If we want to gain insight into the frequency and intensity of extreme cyclone wind speeds over time, we’ll need a national quality-controlled network that has better spatial coverage.</p>
<p>The equipment we have, although it’s designed to withstand extreme conditions, can get knocked around and thrown offline – introducing data gaps in the time series.</p>
<p>Accurate and consistent data points are crucial if we want to record and predict the kinds of extreme winds we might experience during future tropical cyclones. And while the efforts of independent storm chasers and university groups do go some way, taking measurements from different sources can introduce a lot of uncertainty in the overall process. </p>
<h2>Cyclone intensity will increase</h2>
<p>Since 1975, there <a href="https://en.wikipedia.org/wiki/List_of_Category_5_Australian_region_severe_tropical_cyclones">have been 48</a> category-five tropical cyclones to hit Australia – an average of about one per year. While Ilsa sets a new record for the strongest sustained wind gust at landfall, category-five tropical cyclones have been occurring with some regularity overall.</p>
<p>It’s worth mentioning Ilsa formed pretty late in the cyclone season. Although the Bureau of Meteorology says cyclones can form any time of the year, its very rare for this to happen outside of April. </p>
<p>Historical trends and climate change projections suggest the number of landfalling cyclones in our region will decrease over time. This has been consistent with real-world data, and puts Australia at odds with other regions of the world, where cyclone frequency is increasing.</p>
<p>However, most climate models also predict a greater proportion of these cyclones will be of a higher strength. The current scientific consensus is we’ll experience these events less often, but when we do, they will be more intense.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/anatomy-of-monster-storm-how-cyclone-ilsa-is-shaping-up-to-devastate-the-wa-coast-203678">Anatomy of monster storm: how Cyclone Ilsa is shaping up to devastate the WA coast</a>
</strong>
</em>
</p>
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<img src="https://counter.theconversation.com/content/203835/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas Mortlock works for Aon Reinsurance Solutions.</span></em></p>
Do record-breaking wind speeds mean a particularly catastrophic storm? Not always – and it can be tricky to get precise measurements.
Thomas Mortlock, Adjunct Fellow, UNSW Sydney
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/201771
2023-03-17T02:25:27Z
2023-03-17T02:25:27Z
Cyclone Freddy was the most energetic storm on record. Is it a harbinger of things to come?
<figure><img src="https://images.theconversation.com/files/515972/original/file-20230317-2475-i50sjb.jpeg?ixlib=rb-1.1.0&rect=129%2C0%2C1408%2C726&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NOAA / AP</span></span></figcaption></figure><p>On February 4, a storm off the north-west coast of Australia was named Cyclone Freddy. It rapidly strengthened and headed west across the Indian Ocean, eventually causing devastation in eastern Africa. Hundreds of people died, tens of thousands more were displaced, national energy grids were crippled, flash flooding was widespread and <a href="https://reliefweb.int/report/mozambique/southern-africa-tropical-cyclone-freddy-flash-update-no-7-14-march-2023">socioeconomic impacts have been severe</a>.</p>
<p>At its peak on February 21, Freddy had wind gusts of up to 270 km/h, making it a category 5 storm, the highest category on the <a href="https://www.nhc.noaa.gov/aboutsshws.php">Saffir-Simpson scale</a> used to measure cyclone intensity. The following day, Freddy was upgraded further to a “very intense tropical cyclone”, which is science-speak for “off the chart”.</p>
<p>Freddy was the <a href="https://www.reuters.com/world/africa/why-is-cyclone-freddy-record-breaking-storm-2023-03-14/">most energetic storm on record</a>. It also went through the most cycles of weakening and re-intensifying, and may have been the longest-lived cyclone in history.</p>
<p>So was this megastorm a one-off event, or a harbinger of the global warming–fuelled cyclones of the future? And, either way, what does it tell us about preparing for what lies ahead?</p>
<h2>A remarkable journey</h2>
<p>Australia has experienced cyclones in the past with comparable strengths to Freddy. According to the Bureau of Meteorology, <a href="https://en.wikipedia.org/wiki/List_of_Category_5_Australian_region_severe_tropical_cyclones#:%7E:text=Within%20the%20basin%20a%20Category,Australian%20tropical%20cyclone%20intensity%20scale.">48 category-5 tropical cyclones have formed in the Australian region since 1975</a>. That’s about one a year, although most do not cross the coast, or weaken by the time they do.</p>
<p>Cyclone Mahina, which hit Queensland in 1899, is widely considered Australia’s strongest recorded tropical cyclone. Further back in the palaeoclimate record, we find <a href="https://www.nature.com/articles/35097055">evidence of stronger events still</a>.</p>
<p>What was truly remarkable about Freddy was its journey. Freddy was a named tropical cyclone for 39 consecutive days and travelled more than 8,000 kilometres across the entire South Indian Ocean. </p>
<p>It may have been the longest-lasting tropical cyclone on record (this is currently being confirmed by the World Meteorological Organization). The <a href="https://www.myjoyonline.com/wmo-to-set-up-expert-committee-to-determine-possibility-of-tropical-cyclone-freddy-becoming-longest-lasting-on-record/">31-day Hurricane John</a> set the previous record in 1994. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map of the Indian Ocean showing Cyclone Freddy's path." src="https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=466&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=466&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=466&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Over 39 days in February and March 2023, Cyclone Freddy travelled more than 8,000 kilometres from the Timor Sea to the east coast of Africa.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Cyclone_Freddy#/media/File:Freddy_2023_path.png">Meow / Wikimedia / NASA / NRL / NOAA</a></span>
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<p>Freddy appears to have had an accumulated cyclone energy (the index used to measure the energy released by a tropical cyclone over its lifetime) <a href="https://public.wmo.int/en/media/news/tropical-cyclone-freddy-may-set-new-record">equivalent to an average full North Atlantic hurricane season</a>.</p>
<h2>Was Cyclone Freddy driven by climate change?</h2>
<p>It’s no easy task to join the dots between climate change and any given extreme weather event, such as a cyclone or heatwave. </p>
<p>A relatively new area of study called “<a href="https://www.worldweatherattribution.org/">climate attribution science</a>” attempts to do it by determining how much more likely a given event was in today’s climate compared to the past climate.</p>
<p>The main idea in attribution science is to model extreme weather events under present-day climate conditions, and then do it again when the model is run with no human-made greenhouse gases in the atmosphere. This process is repeated many times to try to understand the likelihood of a weather event occurring with and without human-driven warming.</p>
<p>To date, these studies have had most success with large-scale, slow-moving extreme weather events – like the <a href="https://www.pnas.org/doi/10.1073/pnas.2112087118">February 2019 European heatwave</a>. The jury is still out on how well we can do this for tropical cyclones.</p>
<p>So we can’t yet say what role climate change may have played in making a cyclone like Freddy more likely, but the science is moving fast.</p>
<h2>The future of cyclones: fewer, slower, stronger</h2>
<p>Cyclone behaviour is already changing, and our climate models project it will change more in the future. </p>
<p>In many parts of the world, the number of cyclones making landfall is on the rise. In Australia, however, this number is decreasing – and most climate models indicate <a href="https://www.nature.com/articles/s41558-022-01388-4">this decrease will likely continue</a> under a warming climate. This is related to the weakening of Pacific atmospheric circulation, which is less favourable for the formation of tropical cyclones.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/research-shows-tropical-cyclones-have-decreased-alongside-human-caused-global-warming-but-dont-celebrate-yet-185706">Research shows tropical cyclones have decreased alongside human-caused global warming – but don't celebrate yet</a>
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</em>
</p>
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<p>This is good news for Australia, although other changes in projected cyclone behaviour may give us less cause for optimism.</p>
<p>While the total number of cyclones may decrease, research indicates those that do make landfall <a href="https://nespclimate.com.au/wp-content/uploads/2019/11/A4_4pp_brochure_NESP_ESCC_Tropical_Cyclones_FINAL_Nov11_2019_WEB.pdf">may be stronger</a>. Other research indicates cyclones may be <a href="https://www.nature.com/articles/s41586-018-0158-3">moving more slowly</a> and also <a href="https://www.nature.com/articles/s41561-021-00859-1">roaming farther from the equator</a>. The amount of rain any one cyclone can hold will also <a href="https://www.nature.com/articles/s41467-021-25685-2">likely increase</a> in a warming atmosphere.</p>
<p>All these changes would increase cyclone risk on the east coast of Australia. However, these projections are uncertain. The only discernible trend so far is a reduction in overall cyclone frequency.</p>
<h2>The influence of La Nina</h2>
<p>Australia is famously a land of droughts and flooding rains. Regardless of underlying trends, large swings in climate conditions are common from year to year.</p>
<p>In Australia, most cyclone (and flood) impacts occur during La Nina periods: <a href="https://aoninsights.com.au/say-goodbye-to-the-big-wet-and-excessive-losses/">over 60% of cyclone losses and 75% of insured flood losses</a>. </p>
<p>The La Nina period that has just ended meant the waters of the tropical East Indian Ocean were warmer than usual. This extra heat may have sustained Freddy in its trans-oceanic journey. </p>
<p>Similarly, a <a href="https://www.reuters.com/world/asia-pacific/new-zealands-southern-waters-experiencing-marine-heatwave-2023-01-16/#:%7E:text=The%20marine%20heatwave%20comes%20as,the%20heatwave%2C%20said%20de%20Souza.">marine heatwave</a> in the Southwest Pacific contributed to the lifetime and amount of rain produced by ex-tropical cyclone Gabrielle in New Zealand in February.</p>
<h2>Building for the future</h2>
<p>Cyclone impacts are traditionally hit-and-miss affairs in Australia. We can get a category 5 cyclone screaming through north-western WA and only a few cattle really know about it.</p>
<p>However, as population increases, the number of people in harm’s way also potentially increases. No matter how cyclones may change in the future, we need to ensure resilience is a core feature in building future housing stock.</p>
<p>In Australia, it is encouraging to see more government emphasis on reducing disaster risk (rather then just cleaning up afterwards), through frameworks such as the <a href="https://nema.gov.au/disaster-ready-fund">Disaster Ready Fund</a>.</p>
<p>Elsewhere, we should throw our support behind resilience programs in the Global South like those in countries hit by Freddy, where vulnerabilities remain high.</p><img src="https://counter.theconversation.com/content/201771/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas Mortlock works for Aon Reinsurance Solutions</span></em></p>
The record-breaking Cyclone Freddy was a wake-up call to prepare for the storms of the future.
Thomas Mortlock, Adjunct Fellow, UNSW Sydney
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/200371
2023-02-21T11:56:45Z
2023-02-21T11:56:45Z
Cyclones in southern Africa: five essential reads
<figure><img src="https://images.theconversation.com/files/511392/original/file-20230221-18-r3odu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The fishing village of Mahebourg, Mauritius, is among the places in the path of cyclone Freddy.
</span> <span class="attribution"><span class="source">Laura Morosoli/AFP via Getty Images</span></span></figcaption></figure><p><em>Tropical cyclone Freddy was, on 21 February 2023, bearing down on Mauritius and Madagascar. Mauritius grounded flights and, news agency Reuters <a href="https://www.dailymaverick.co.za/article/2023-02-20-mauritius-halts-flights-madagascar-braces-for-floods-as-cyclone-freddy-nears/">reported</a>, emergency teams in four regions of Madagascar were braced for “heavy rains, floods and landslides”.</em></p>
<p><em>A day earlier the Mauritius Meteorological Services <a href="http://metservice.intnet.mu/current-cyclone.php">issued</a> a Class 3 cyclone warning, saying estimated gusts in the centre of Cyclone Freddy could reach around 280 kilometres an hour.</em></p>
<p><em>Both island nations are located in the Indian Ocean and are no strangers to tropical cyclones. But, as the global climate shifts, such storms will become ever more common, endangering millions of people in Madagascar, Mauritius and other countries in the southern African region like Mozambique and Malawi.</em> </p>
<p><em>The Conversation Africa has published a number of articles explaining the science of tropical cyclones and the role climate change is playing in their increasing frequency and force. Here are five essential reads.</em></p>
<hr>
<h2>Warming oceans</h2>
<p>Tropical cyclones are huge. They can span more than 1,000km in diameter and they draw their energy from the ocean heat – ocean surface temperatures of at least 26⁰C are required for tropical cyclones to form. Over the past 30 years, as the world’s oceans have become warmer, the locations of where tropical cyclones form and intensify have been shifting.</p>
<p>Climate scientists Micheal Pillay and Jennifer Fitchett unpacked these shifts.</p>
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<p>
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<strong>
Read more:
<a href="https://theconversation.com/tropical-cyclones-in-the-south-west-indian-ocean-new-insights-125579">Tropical cyclones in the South West Indian Ocean: new insights</a>
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</em>
</p>
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<h2>Devastation</h2>
<p>The most damaging tropical cyclones of the past few years were tropical cyclones Idai and Kenneth, which hit Mozambique especially hard in March and April of 2019. Idai alone killed more than 1,500 people in Mozambique, Malawi and Zimbabwe. In an article first published in 2019 soon after the devastation and updated in 2022 as more powerful storms battered Mozambique, Professor Fitchett explained why tropical cyclones from the Indian Ocean were becoming ever more powerful.</p>
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<p>
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<strong>
Read more:
<a href="https://theconversation.com/why-the-indian-ocean-is-spawning-strong-and-deadly-tropical-cyclones-116559">Why the Indian Ocean is spawning strong and deadly tropical cyclones</a>
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</em>
</p>
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<h2>Countries must pull together</h2>
<p>In the wake of tropical storms Idai and Kenneth, researcher Chris Changwe Nshimbi argued that the Southern African Development Community had once again proved that it wasn’t ready to deal with environmental disasters as a collective. He traced the reasons for these shortcomings and suggested ways forward – more critical than ever as tropical storms and other climate-related crises hammer southern Africa.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/southern-african-countries-wont-manage-disasters-unless-they-work-together-114541">Southern African countries won't manage disasters unless they work together</a>
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</em>
</p>
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<h2>More to come</h2>
<p>Nshimbi is right: there is far more to come. Professor Fitchett – who has dedicated much of her research to the phenomenon – explained what drives extreme weather events.</p>
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<p>
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<strong>
Read more:
<a href="https://theconversation.com/southern-africa-must-brace-itself-for-more-tropical-cyclones-in-future-103641">Southern Africa must brace itself for more tropical cyclones in future</a>
</strong>
</em>
</p>
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<h2>The bigger picture</h2>
<p>Tropical cyclones are only one part of the African continent’s climate crisis. Meteorologist Victor Ongoma explained what climate change experts were predicting for the continent and how different regions would be affected.</p>
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<p>
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<strong>
Read more:
<a href="https://theconversation.com/insights-for-african-countries-from-the-latest-climate-change-projections-165944">Insights for African countries from the latest climate change projections</a>
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</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/200371/count.gif" alt="The Conversation" width="1" height="1" />
Tropical cyclones are becoming more frequent in the Indian Ocean. Here’s why and what that means.
Natasha Joseph, Commissioning Editor
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/196470
2023-02-07T13:34:48Z
2023-02-07T13:34:48Z
Hurricane Harvey more than doubled the acidity of Texas’ Galveston Bay, threatening oyster reefs
<figure><img src="https://images.theconversation.com/files/507440/original/file-20230131-4643-5mjeyj.jpg?ixlib=rb-1.1.0&rect=48%2C0%2C5400%2C3564&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Seabirds forage on an oyster shell island on the Texas Gulf Coast.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/an-american-oystercatcher-haematopus-palliatus-foraging-on-news-photo/1449679985">Jon G. Fuller/VW Pics/ Universal Images Group via Getty Images</a></span></figcaption></figure><p>Most people associate hurricanes with high winds, intense rain and rapid flooding on land. But these storms can also change the chemistry of coastal waters. Such shifts are less visible than damage on land, but they can have dire consequences for marine life and coastal ocean ecosystems. </p>
<p>We are oceanographers who study the <a href="https://scholar.google.com/citations?user=u7D6sQgAAAAJ&hl=en">effects of ocean acidification</a>, including on <a href="https://scholar.google.com/citations?user=MOYxO9MAAAAJ&hl=en">organisms like oysters and corals</a>. In a <a href="https://doi.org/10.1038/s43247-022-00608-1">recent study</a>, we examined how stormwater runoff from Hurricane Harvey in 2017 affected the water chemistry of Galveston Bay and the health of the bay’s oyster reefs. We wanted to understand how extreme rainfall and runoff from hurricanes influenced acidification of bay waters, and how long these changes could last. </p>
<p>Our findings were startling. Hurricane Harvey, which generated massive rainfall in the Houston metropolitan area, delivered a huge pulse of fresh water into Galveston Bay. As a result, the bay was two to four times more acidic than normal for at least three weeks after the storm.</p>
<p>This made bay water corrosive enough to damage oyster shells in the estuary. Because oyster growth and recovery rely on many factors, it is hard to tie specific changes to acidification. However, increased acidification certainly would have made it harder for oyster reefs damaged by Hurricane Harvey to recover. And while our study focused on Galveston Bay, we suspect that similar processes may be occurring in other coastal areas.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507436/original/file-20230131-5037-8ovozq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Satellite photo of Houston and the gulf coast immediately after Harvey." src="https://images.theconversation.com/files/507436/original/file-20230131-5037-8ovozq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507436/original/file-20230131-5037-8ovozq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507436/original/file-20230131-5037-8ovozq.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507436/original/file-20230131-5037-8ovozq.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507436/original/file-20230131-5037-8ovozq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507436/original/file-20230131-5037-8ovozq.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507436/original/file-20230131-5037-8ovozq.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This satellite image, taken six days after Harvey made landfall, shows Galveston Bay and other rivers and bays around Houston filled with brown sediment-laden floodwaters.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/90866/texas-waters-run-brown-after-harvey">NASA Earth Observatory</a></span>
</figcaption>
</figure>
<h2>Vast quantities of water</h2>
<p>Scientists predict that climate change will make hurricanes stronger and <a href="https://climate.nasa.gov/news/3184/a-force-of-nature-hurricanes-in-a-changing-climate/">increase the amount of rain they produce</a> over the next several decades. Changes in ocean chemistry, caused by runoff from these storms, are becoming an increasing threat to many marine ecosystems, especially coastal reefs built by oysters and corals. </p>
<p><a href="https://oceanservice.noaa.gov/facts/estuary.html">Coastal estuaries</a> like Galveston Bay, where rivers meet the sea, are some of the most productive ecosystems in the world. Galveston Bay is the largest bay on the Texas coast and one of the largest in the U.S.; it covers about 600 square miles, roughly half the size of Rhode Island. Its extensive oyster reefs provide <a href="https://doi.org/10.1016/j.scitotenv.2021.145132">about 9% of the national oyster harvest</a>. </p>
<p><a href="https://www.climate.gov/news-features/event-tracker/reviewing-hurricane-harveys-catastrophic-rain-and-flooding">Hurricane Harvey</a>, the wettest tropical cyclone in U.S. history, made landfall on the Texas coast as a Category 4 hurricane on Aug. 26, 2017. Harvey stalled at the coast for four days, sitting over both land and ocean. </p>
<p>Maintaining contact with warm Gulf of Mexico waters fueled the storm with both energy and rainfall, allowing it to persist and drop extreme amounts of rain directly onto Houston and surrounding areas – <a href="https://theconversation.com/what-made-the-rain-in-hurricane-harvey-so-extreme-83137">up to 50 inches in four days</a>. All of that rain and floodwater had to go somewhere, and much of it flowed into Galveston Bay. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/YzQGgyrxXiI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">These videos show the scale of flooding across Houston from Hurricane Harvey.</span></figcaption>
</figure>
<h2>Climate change and ocean acidification</h2>
<p>The ocean acidification issues that we study are a <a href="https://theconversation.com/global-warmings-evil-twin-ocean-acidification-19017">well-known effect related to climate change</a>. Human activities, mainly burning fossil fuel, emit carbon dioxide into the atmosphere. The ocean absorbs about one-third of these emissions, which alters ocean chemistry, making seawater more acidic. </p>
<p>Acidification can <a href="https://www.epa.gov/ocean-acidification/effects-ocean-and-coastal-acidification-marine-life">harm many forms of marine life</a>. It is especially dangerous for animals that build their shells and skeletons out of calcium carbonate, such as oysters and corals. As seawater becomes more acidic, it makes these structures harder to build and easier to erode. </p>
<p>Oysters fuse together as they grow, creating large rocklike underwater reefs that <a href="https://www.youtube.com/watch?v=PbFQ5EndLso">protect shorelines from wave erosion</a>. These reefs <a href="https://www.fisheries.noaa.gov/national/habitat-conservation/oyster-reef-habitat">provide habitat</a> for other creatures, such as barnacles, anemones and mussels, which in turn serve as food sources for many fish species. </p>
<p>Rising atmospheric CO₂ levels are acidifying oceans worldwide. As our study shows, local events like tropical cyclones can add to global acidification. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"661924520496922624"}"></div></p>
<h2>Stormwater from Harvey caused extreme coastal acidification</h2>
<p>The main cause of the unprecedented acidification that occurred after Hurricane Harvey was the excessive amount of rainfall and runoff that entered Galveston Bay. To help manage large-scale flooding in the Houston area, the city released large volumes of water from reservoirs for more than two months after Harvey. These releases extended the time during which stormwater entered Galveston Bay and increased its acidity. </p>
<p>Scientists use the pH scale to measure how acidic or basic (alkaline) water is. A pH value of 7 is neutral; higher values are basic, and lower values are acidic. The pH scale is logarithmic, so a decrease of one full unit – say, from 8 to 7 – represents a tenfold increase in acidity. </p>
<p>Rainwater is more acidic than either river water or seawater, which pick up minerals from soil that are slightly basic and can balance out absorbed carbon dioxide from the atmosphere. Rainwater’s pH is around 5.6, compared with <a href="https://datastream.org/en/guide/ph">between 6.5 and 8.2 for rivers</a> and <a href="https://www.noaa.gov/education/resource-collections/ocean-coasts/ocean-acidification">about 8.1 for seawater</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/508452/original/file-20230206-25-fdap84.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Th pH scale with values for common substances." src="https://images.theconversation.com/files/508452/original/file-20230206-25-fdap84.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508452/original/file-20230206-25-fdap84.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=240&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508452/original/file-20230206-25-fdap84.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=240&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508452/original/file-20230206-25-fdap84.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=240&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508452/original/file-20230206-25-fdap84.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=302&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508452/original/file-20230206-25-fdap84.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=302&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508452/original/file-20230206-25-fdap84.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=302&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 pH scale shows how acidic or basic substances are.</span>
<span class="attribution"><a class="source" href="https://www.epa.gov/acidrain/what-acid-rain">USEPA</a></span>
</figcaption>
</figure>
<p>Galveston Bay contains a mix of fresh water from rivers and salty seawater from the Gulf of Mexico – oysters’ preferred habitat. We collected water samples in the bay two weeks after Harvey and found that the bay was made up almost entirely of river water and rainwater from the storm. </p>
<p>Since rainwater, river water and seawater all have different chemistries, we were able to calculate that rainwater made up almost 50% of the water in the bay. This means that acidic rainwater from Harvey replaced the basic seawater within the bay after the storm. The average bay water pH had dropped from 8 to 7.6, a 2.5-fold increase in acidity. Some zones had pH even as low as 7.4 – four times more acidic than normal. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507432/original/file-20230131-24-p6tcnw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Bar charts showing combinations of seawater, river water and rainwater in Galveston Bay before and after Hurricane Harvey." src="https://images.theconversation.com/files/507432/original/file-20230131-24-p6tcnw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507432/original/file-20230131-24-p6tcnw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=466&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507432/original/file-20230131-24-p6tcnw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=466&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507432/original/file-20230131-24-p6tcnw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=466&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507432/original/file-20230131-24-p6tcnw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=586&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507432/original/file-20230131-24-p6tcnw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=586&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507432/original/file-20230131-24-p6tcnw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=586&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">These charts show how rainfall and runoff from Hurricane Harvey altered the composition of Galveston Bay after the storm made landfall on August 25, 2017.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1038/s43247-022-00608-1">Tacey Hicks, modified from Hicks et al., 2022</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>This extreme acidification lasted for more than three weeks. Bay waters became corrosive not only to more sensitive larval and juvenile oyster shells, but to adult oyster shells as well. <a href="https://doi.org/10.1002/jgrc.20378">Scientists had predicted</a> that increasing CO₂ could cause this scale of coastal acidification but did not expect to see it until around the year 2100. </p>
<p>The fresh water from Harvey also caused a <a href="https://doi.org/10.1016/j.scitotenv.2021.145132">severe oyster die-off</a> in the bay because oysters need slightly salty water to survive. Harvey struck in the middle of oyster spawning season, and acidification may have slowed reef recovery by making it harder for young oysters to form new shells. Officials at the <a href="https://tpwd.texas.gov/">Texas Parks and Wildlife Department</a> have told us that four years later, in late 2021, some Galveston Bay oyster reefs still showed <a href="https://doi.org/10.1038/s43247-022-00608-1">very low additions of new oysters</a>. </p>
<h2>Other coastal areas at risk</h2>
<p>Only a few studies, including ours, have analyzed how tropical cyclones affect coastal acidification. In our view, however, it is highly possible that other storms have caused the kind of extreme acidification that we detected in the wake of Harvey. </p>
<p>We reviewed the 10 wettest <a href="https://www.wpc.ncep.noaa.gov/tropical/rain/tcmaxima.html">tropical cyclones in the U.S. since 1900</a> and found that nine, including Harvey, caused large amounts of rain and flooding in coastal areas with bay or estuary ecosystems. Other storms didn’t produce as much rainfall as Harvey, but some of the affected bays were much smaller than Galveston Bay, so less rain would have been needed to replace seawater in the bay and cause a similar level of acidification to what Harvey produced.</p>
<p>We think that this likely has already occurred in other places struck by hurricanes but went unrecorded because scientists weren’t able to measure acidification before and after the storms. As climate change continues to make tropical cyclones larger and wetter, we see storm-induced acidification as a significant threat to coastal ecosystems.</p><img src="https://counter.theconversation.com/content/196470/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tacey Hicks received funding from Texas Sea Grant to support the publication of this study. Tacey Hicks is currently affiliated with the National Oceanic and Atmospheric Administration and Texas Sea Grant as part of the John A Knauss Marine Policy Fellowship. </span></em></p><p class="fine-print"><em><span>Kathryn Shamberger receives funding from the National Science Foundation, US Department of Energy, and US Environmental Protection Agency.</span></em></p>
Climate change is making oceans more acidic globally. Now, scientists are finding that large storms can send pulses of acidic water into bays and estuaries, further stressing fish and shellfish.
Tacey Hicks, PhD Candidate in Oceanography, Texas A&M University
Kathryn Shamberger, Associate Professor of Oceanography, Texas A&M University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/194891
2022-11-29T20:41:33Z
2022-11-29T20:41:33Z
Even weak tropical cyclones have grown more intense worldwide – we tracked 30 years of them using currents
<figure><img src="https://images.theconversation.com/files/497777/original/file-20221128-18-nq66tz.jpg?ixlib=rb-1.1.0&rect=0%2C395%2C2256%2C1482&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hurricane Nicole was a Category 1 storm, but it caused extensive damage to Florida in 2022.</span> <span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/150586/nicole-approaches-florida">Lauren Dauphin/NASA Earth Observatory</a></span></figcaption></figure><p>Tropical cyclones have been growing stronger worldwide over the past 30 years, and not just the big ones that you hear about. <a href="https://doi.org/10.1038/s41586-022-05326-4">Our new research</a> finds that weak tropical cyclones have gotten at least <a href="https://theconversation.com/hurricane-hunters-flew-through-ians-powerful-winds-to-forecast-intensity-heres-what-happens-when-the-plane-plunges-into-the-eyewall-of-a-storm-187234">15% more intense</a> in ocean basins where they occur around the world.</p>
<p>That means storms that might have caused minimal damage a few decades ago are growing more dangerous <a href="https://climate.nasa.gov/news/3184/a-force-of-nature-hurricanes-in-a-changing-climate/">as the planet warms</a>.</p>
<p>Warmer oceans provide more energy for storms to intensify, and theory and climate models point to <a href="https://doi.org/10.1073/pnas.1920849117">powerful storms growing stronger</a>, but intensity isn’t easy to document. We found a way to measure intensity by using the ocean currents beneath the storms – with the help of thousands of floating beachball-sized labs called drifters that beam back measurements from around the world.</p>
<h2>Why it’s been tough to measure intensity</h2>
<p>Tropical cyclones are large storms with rotating winds and clouds that form over warm ocean water. They are known as tropical storms or hurricanes in the Atlantic and typhoons in the Northwest Pacific.</p>
<p>A tropical cyclone’s intensity is one of the most important factors for determining the damage the storm is likely to cause. However, it’s <a href="https://severeweather.wmo.int/TCFW/RAIV_Workshop2016/08_DvorakTechnique_JackBeven.pdf">difficult to accurately estimate</a> intensity from satellite observations alone.</p>
<p>Intensity is often based on maximum sustained surface wind speed at about 33 feet (10 meters) above the surface over a period of one, two or 10 minutes, depending on the meteorological agency doing the measuring. During a hurricane, that region of the storm is nearly impossible to reach.</p>
<p>For some storms, NOAA meteorologists will fly specialized aircraft into the cyclone and <a href="https://theconversation.com/hurricane-hunters-flew-through-ians-powerful-winds-to-forecast-intensity-heres-what-happens-when-the-plane-plunges-into-the-eyewall-of-a-storm-187234">drop measuring devices</a> to gather detailed intensity data as the devices fall. But there are many more storms that don’t get measured that way, particularly in more remote basins.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/497771/original/file-20221128-20372-qsm0vt.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map with dots for locations of drifters as of Nov. 28, 2022. The dots are all over the oceans." src="https://images.theconversation.com/files/497771/original/file-20221128-20372-qsm0vt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497771/original/file-20221128-20372-qsm0vt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497771/original/file-20221128-20372-qsm0vt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497771/original/file-20221128-20372-qsm0vt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497771/original/file-20221128-20372-qsm0vt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497771/original/file-20221128-20372-qsm0vt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497771/original/file-20221128-20372-qsm0vt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Over 1,100 drifters are currently operating around the world. The U.S. (blue dots) operates over 430 of them. France (orange) has about 200. Each typically lasts about a year.</span>
<span class="attribution"><a class="source" href="https://www.aoml.noaa.gov/phod/gdp/interactive/drifter_array.html">NOAA</a></span>
</figcaption>
</figure>
<p><a href="https://doi.org/10.1038/s41586-022-05326-4">Our study</a>, published in the journal Nature in November 2022, describes <a href="https://theconversation.com/hurricane-hunters-flew-through-ians-powerful-winds-to-forecast-intensity-heres-what-happens-when-the-plane-plunges-into-the-eyewall-of-a-storm-187234">a new method</a> to infer tropical cyclone intensity from ocean currents, which are already being measured by an army of drifters.</p>
<h2>How drifters work</h2>
<p>A <a href="https://www.adp.noaa.gov/teachers/letsdissectadrifter/">drifter is a floating ball</a> with sensors and batteries inside and an attached “drogue” that looks like a windsock trailing under the water beneath it to help stabilize it. The drifter moves with the currents and regularly transmits data to a satellite, including water temperature and location. The location data can be used to measure the speed of currents.</p>
<figure class="align-center ">
<img alt="A sphere about the size of a volleyball with what looks like a windsock attached." src="https://images.theconversation.com/files/497769/original/file-20221128-14-tuwek8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497769/original/file-20221128-14-tuwek8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=482&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497769/original/file-20221128-14-tuwek8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=482&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497769/original/file-20221128-14-tuwek8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=482&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497769/original/file-20221128-14-tuwek8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=606&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497769/original/file-20221128-14-tuwek8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=606&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497769/original/file-20221128-14-tuwek8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=606&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Examples of NOAA’s drifters and the drogue that helps stabilize them.</span>
<span class="attribution"><a class="source" href="https://www.climate.gov/news-features/climate-tech/doing-their-part-drifter-buoys-provide-ground-truth-climate-data">NOAA</a></span>
</figcaption>
</figure>
<p>Since NOAA launched its <a href="https://www.aoml.noaa.gov/phod/gdp/faq.php#GDP">Global Drifter Program</a> in 1979, more than 25,000 drifters have been deployed in global oceans. Those devices have provided about 36 million records over time. Of those records, more than 85,000 are associated with weak tropical cyclones – those that are tropical storms or Category 1 hurricanes or typhoons – and about 5,800 that are associated with stronger tropical cyclones.</p>
<p>That isn’t enough data to analyze strong cyclones globally, but we can find trends in the intensity of the weak tropical cyclones.</p>
<p>Here’s how: Winds transfer momentum into the surface ocean water through frictional force, driving water currents. The relationship between wind speed and ocean current, <a href="https://scied.ucar.edu/learning-zone/earth-system/how-ocean-moves-ekman-transport">known as Ekman theory</a>, provides a theoretical foundation for our method of deriving wind speeds from the drifter-measured ocean currents.</p>
<figure>
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<figcaption><span class="caption">Explaining Vagn Walfrid Ekman’s theory of currents.</span></figcaption>
</figure>
<p>Our derived wind speeds are consistent with wind speeds directly measured by nearby buoy arrays, justifying the new method to estimate tropical cyclone intensity from drifter measurements.</p>
<h2>Evidence beneath the storms</h2>
<p>In <a href="https://theconversation.com/hurricane-hunters-flew-through-ians-powerful-winds-to-forecast-intensity-heres-what-happens-when-the-plane-plunges-into-the-eyewall-of-a-storm-187234">analyzing those records</a>, we found that the ocean currents induced by weak tropical cyclones became stronger globally during the 1991-2020 period. We calculated that the increase in ocean currents corresponds to a 15% to 21% increase in the intensity of weak tropical cyclones, and that intensification occurred in all ocean basins.</p>
<p>In the Northwest Pacific, an area including China, Korea and Japan, a relatively large amount of available drifter data also shows a consistent upward trend in the intensity of strong tropical cyclones.</p>
<p>We also found evidence of increasing intensity in the changes in water temperatures measured by satellites. When a tropical cyclone travels through the ocean, it <a href="https://oceantoday.noaa.gov/fuelforthestorm/">draws energy from the warm surface water</a> and churns the water layers below, leaving a footprint of <a href="https://doi.org/10.1029/2020GL091676">colder water in its wake</a>. Stronger tropical cyclones bring more cold water from the subsurface to the surface ocean, leading to a stronger cooling in the ocean surface.</p>
<p>It’s important to remember that even weak tropical cyclones can have devastating impacts. <a href="https://www.bbc.com/news/world-asia-61089853">Tropical Storm Megi</a>, called Agaton in the Philippines, triggered landslides and was blamed for <a href="https://www.reuters.com/world/asia-pacific/philippine-president-marcos-inspects-landslide-hit-province-death-toll-110-2022-11-01/">214 deaths in the Philippines</a> in April 2022. Early estimates suggest Hurricane Nicole caused <a href="https://apnews.com/article/hurricanes-storms-florida-oceans-business-1ab108ae1ab2648b07626344c7f6ee32">over $500 million</a> in damage <a href="https://theconversation.com/dreaming-of-beachfront-real-estate-much-of-floridas-coast-is-at-risk-of-storm-erosion-that-can-cause-homes-to-collapse-as-daytona-just-saw-194492">in Volusia County</a> alone when it hit Florida as a Category 1 storm in November 2022.</p>
<p>The 2022 Atlantic hurricane season officially ended on Nov. 30 with <a href="https://www.nhc.noaa.gov/archive/2022/">14 named storms and eight hurricanes</a>. It isn’t clear how rising global temperatures will effect the number of tropical cyclones that form, but our findings suggest that coastal communities need to be better prepared for increased intensity in those that do form and a concurrent <a href="https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level">rise in sea level</a> in the future.</p><img src="https://counter.theconversation.com/content/194891/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Research shows storms that might have caused minimal damage a few decades ago are becoming stronger and more destructive as the planet warms.
Wei Mei, Assistant Professor of Earth, Marine and Environmental Sciences, University of North Carolina at Chapel Hill
Shang-Ping Xie, Roger Revelle Professor of Climate Science, Scripps Institution of Oceanography, University of California, San Diego
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/162341
2021-07-29T13:15:39Z
2021-07-29T13:15:39Z
5 ways climate-driven ocean change can threaten human health
<figure><img src="https://images.theconversation.com/files/413603/original/file-20210728-21-3aqzwz.jpg?ixlib=rb-1.1.0&rect=13%2C58%2C2982%2C1913&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ocean waters are now warmer, more acidic and hold less oxygen. They're also stressed from overfishing and pollution. </span> <span class="attribution"><span class="source">THE CANADIAN PRESS/Andrew Vaughan</span></span></figcaption></figure><p>Humans have a deep and complex <a href="https://oceanpanel.org/sites/default/files/2020-10/Human%20Relationship%20with%20the%20Ocean%20Full%20Paper.pdf">relationship with the sea</a>. It <a href="https://doi.org/10.1016/j.worlddev.2015.11.007">provides food</a> and <a href="https://fishbase.ca/Nutrients/NutrientSearch.php">essential nutrients</a>, <a href="https://dx.doi.org/10.4062%2Fbiomolther.2016.181">medicine</a> and <a href="https://doi.org/10.1016/S0308-597X(02)00045-3">renewable energy</a>. <a href="https://doi.org/10.1016/j.healthplace.2019.102212">People swim</a>, <a href="https://doi.org/10.1177%2F1049732314549477">surf</a> and <a href="https://doi.org/10.3390/ijerph17197238">scuba dive</a> in this “<a href="http://dx.doi.org/10.1016/j.marpolbul.2009.04.019">blue gym</a>.” It’s even an important part of therapeutic recreation, like <a href="https://doi.org/10.1080/07303084.2014.884424">surf therapy</a> for <a href="https://www.nytimes.com/2019/08/08/well/mind/catching-waves-for-well-being.html">war veterans and children with autism</a>.</p>
<p><a href="https://doi.org/10.1016/j.marpol.2009.08.006">Economies are also bound to the ocean</a>. Fishing, tourism, marine transportation and shipping bring jobs, income and food security, while serving culture and other <a href="https://www.who.int/health-topics/social-determinants-of-health#tab=tab_1">social determinants of health</a>.</p>
<p>From our <a href="https://www.facebook.com/Littoral.Ulaval/photos/a.1954500618111079/3066356660258797/">ancestors to our children</a>, diverse human cultures, livelihoods and ways of life flow to, and from, the sea. But rising greenhouse gas emissions are changing the ocean and putting our health at risk.</p>
<p><a href="https://www.ipcc.ch/site/assets/uploads/sites/3/2019/11/03_SROCC_SPM_FINAL.pdf">Ocean waters are now warmer, more acidic and hold less oxygen</a>. Ocean ecosystems, already <a href="http://www.fao.org/state-of-fisheries-aquaculture">stressed from overfishing</a> <a href="https://www.nationalgeographic.com/environment/article/critical-issues-marine-pollution">and pollution</a>, face <a href="https://doi.org/10.1038/ncomms8615">escalating risks of further degradation</a>. With melting sea ice, rising sea levels and growing extreme weather events, <a href="https://doi.org/10.1139/facets-2020-0035">human health and well-being now face many threats</a>, most aimed at <a href="https://www.un.org/esa/sustdev/natlinfo/indicators/methodology_sheets/oceans_seas_coasts/pop_coastal_areas.pdf">coastal populations</a>.</p>
<h2>1. Hydrologic disasters</h2>
<p>Marked by their swift and destructive power, <a href="https://www.ipcc.ch/report/managing-the-risks-of-extreme-events-and-disasters-to-advance-climate-change-adaptation/">natural disasters</a> are becoming more extreme and more frequent with climate change. </p>
<p>For example, <a href="https://oceanservice.noaa.gov/facts/cyclone.html">tropical cyclones</a> (like hurricanes and typhoons), <a href="https://doi.org/10.1371/currents.dis.2664354a5571512063ed29d25ffbce74">which have killed about 1.33 million people</a> since the beginning of the 20th century, <a href="https://doi.org/10.5281/zenodo.4570334">are getting more intense with warming ocean waters</a>. The number of <a href="https://time.com/4946730/hurricane-categories/">Category 4 and 5 hurricanes</a> has <a href="https://doi.org/10.1007/s00382-013-1713-0">increased 25 to 30 per cent for each degree Celsius of human-induced global warming</a> since the mid 1970s.</p>
<p><a href="https://www.who.int/health-topics/floods#tab=tab_1">Storm surges, flooding</a> and physical trauma cause most fatalities and injuries. But in the wake of disaster, environmental and social conditions also threaten public health. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/hurricane-damage-harms-the-most-vulnerable-reveals-inequality-and-social-divides-159678">Hurricane damage harms the most vulnerable, reveals inequality and social divides</a>
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</em>
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<p>Stagnant water and damaged wastewater systems can expose people to <a href="https://doi.org/10.1080/10937404.2019.1654422">toxins, bacteria and viruses</a>. Interruptions to <a href="https://doi.org/10.1017/dmp.2016.3">health care</a> and negative impacts on housing, employment and other social determinants of health subject people to <a href="https://doi.org/10.5670/oceanog.2006.62">distressing conditions</a> (such as crowded shelters and diplacement) beyond the <a href="https://doi.org/10.1017/S0144686X1600115X">trauma of the event</a>.</p>
<p>This can worsen <a href="https://doi.org/10.1093/epirev/mxi011">a broad spectrum of public health issues</a> — from <a href="https://doi.org/10.1016/j.emc.2018.07.002">infectious diseases</a> (like <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4438646/">cholera</a>, <a href="https://doi.org/10.3201/eid1707.101050">leptospirosis</a> and <a href="https://doi.org/10.1371/journal.pone.0131423">diarrheal diseases</a>) to <a href="https://www.who.int/news-room/fact-sheets/detail/noncommunicable-diseases">non-communicable diseases</a> (such as <a href="https://doi.org/10.1097/EDE.0000000000001337">cardiovascular</a> and <a href="https://doi.org/10.1017/dmp.2020.424">respiratory</a> conditions) to <a href="https://www.ncei.noaa.gov/news/hurricanes-take-heavy-toll-mental-health-survivors">adverse mental health</a>.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/another-grim-climate-report-on-oceans-what-will-it-take-to-address-the-compounding-problems-123894">Another grim climate report on oceans – what will it take to address the compounding problems?</a>
</strong>
</em>
</p>
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<p><a href="https://doi.org/10.1038/s41467-021-21777-1">An increase in hospitalizations</a> has been documented among <a href="https://doi.org/10.1289/EHP6976">disaster-affected populations</a> weeks, months and years later. </p>
<p>A well-studied example is Hurricane Katrina, which caused over 1,800 deaths in August 2005 <a href="https://doi.org/10.1097/DMP.0b013e31818aaf55">from drowning, injury and physical trauma</a>, but also led to <a href="https://doi.org/10.3390/ijerph16010074">an abrupt increase in heart conditions</a> and <a href="https://doi.org/10.1111/j.1939-0025.2010.01027.x">serious mental illness</a>. A decade later, <a href="https://doi.org/10.1016/j.socscimed.2019.112610">persistent mental</a> and <a href="https://doi.org/10.1017/dmp.2018.22">cardiovascular health issues</a> are among the reminders of the storm.</p>
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<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>This story is part of <a href="https://theconversation.com/uk/topics/oceans-21-96784">Oceans 21</a></em></strong>
<br><em>Our series on the global ocean opened with <a href="https://oceans21.netlify.app/">five in-depth profiles</a>. Look out for new articles on the state of our oceans in the lead up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.</em></p>
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<h2>2. Migration and displacement</h2>
<p><a href="https://www.ipcc.ch/srocc/chapter/chapter-4-sea-level-rise-and-implications-for-low-lying-islands-coasts-and-communities/">With the rise of global sea level</a>, <a href="https://doi.org/10.1038/s41598-017-01362-7">coastal flooding</a> is becoming more common and severe. Another <a href="https://doi.org/10.1038/s41598-020-67736-6">250,000 square kilometres of coastal land is projected to flood</a> by the end of the century, exposing tens of millions more people to risks. </p>
<p>Advancing ocean waters, erosion and thawing permafrost can make some <a href="https://www.ilo.org/dyn/migpractice/docs/261/Pacific.pdf">coastal settlements hard or impossible to live in</a>. <a href="https://www.oceanfdn.org/sites/default/files/forced%20migration%20alaskan%20community.pdf">The Yup'ik</a> village of <a href="https://www.nationalgeographic.com/science/article/climate-change-finally-caught-up-to-this-alaska-village">Newtok</a> (Niugtaq), for example, began the first phase of a planned relocation in 2019, after coastal storms and thawing permafrost began destroying the village. </p>
<figure class="align-center ">
<img alt="A single-storey house falling off a snow-covered shoreline into the ocean." src="https://images.theconversation.com/files/413607/original/file-20210728-15-1y7bdms.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/413607/original/file-20210728-15-1y7bdms.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=388&fit=crop&dpr=1 600w, https://images.theconversation.com/files/413607/original/file-20210728-15-1y7bdms.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=388&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/413607/original/file-20210728-15-1y7bdms.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=388&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/413607/original/file-20210728-15-1y7bdms.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=488&fit=crop&dpr=1 754w, https://images.theconversation.com/files/413607/original/file-20210728-15-1y7bdms.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=488&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/413607/original/file-20210728-15-1y7bdms.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=488&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An abandoned house sits on a beach after a storm in Shishmaref, Alaska, in 2005. Residents voted to relocate in 2016 due to the severe coastal erosion.</span>
<span class="attribution"><span class="source">(AP Photo/Diana Haecker)</span></span>
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</figure>
<p>While the newly relocated <a href="https://www.kyuk.org/post/after-moving-new-village-mertarvik-residents-say-they-are-healthier">residents have reported feeling healthier</a>, even proactive responses can lead to <a href="https://www.alaskapublic.org/2020/07/29/mertarviks-lack-of-a-commercial-airport-may-have-already-cost-lives/">new risks</a> to <a href="https://doi.org/10.1007/s10584-019-02382-0">health and well-being</a>. Relocations can lead to <a href="https://doi.org/10.1089/eco.2018.0021">distress and trauma</a> when residents have a strong attachment to a place. </p>
<p>The <a href="https://doi.org/10.1186/s12916-017-0981-7">health dimensions of climate-related migrations</a>, especially among those who <a href="https://theconversation.com/how-many-people-will-migrate-due-to-rising-sea-levels-why-our-best-guesses-arent-good-enough-145776">stay or are left behind</a>, have not received enough attention in research and policy. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climigration-when-communities-must-move-because-of-climate-change-122529">'Climigration': when communities must move because of climate change</a>
</strong>
</em>
</p>
<hr>
<h2>3. Sea ice decline</h2>
<p>Over the past 40 years, Arctic sea ice has become smaller and thinner. <a href="https://climate.nasa.gov/vital-signs/arctic-sea-ice/">Its overall extent</a> has declined about 13 per cent per decade, and its <a href="https://doi.org/10.1029/2009GL039035">thickness has decreased</a> by at least 1.75 meters. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/413384/original/file-20210727-14-6b1ps1.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graph showing the downward trend in Arctic sea ice extent" src="https://images.theconversation.com/files/413384/original/file-20210727-14-6b1ps1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/413384/original/file-20210727-14-6b1ps1.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=285&fit=crop&dpr=1 600w, https://images.theconversation.com/files/413384/original/file-20210727-14-6b1ps1.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=285&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/413384/original/file-20210727-14-6b1ps1.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=285&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/413384/original/file-20210727-14-6b1ps1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=358&fit=crop&dpr=1 754w, https://images.theconversation.com/files/413384/original/file-20210727-14-6b1ps1.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=358&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/413384/original/file-20210727-14-6b1ps1.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=358&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Arctic sea ice reaches its minimum each September. September Arctic sea ice is now declining at a rate of 13.1 per cent per decade, relative to the 1981 to 2010 average.</span>
<span class="attribution"><a class="source" href="https://climate.nasa.gov/vital-signs/arctic-sea-ice/">(NSIDC/NASA)</a></span>
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</figure>
<p>Sea ice is a <a href="https://doi.org/10.1098/rsbl.2016.0198">defining feature of life in the Arctic</a>. It provides a platform for <a href="https://doi.org/10.1002/9781118778371.ch25">travel and harvesting activities</a>, and shapes ecological processes that are at the foundation of local <a href="https://www.nirb.ca/publications/strategic%20environmental%20assessment/190125-17SN034-QIA%20Report%20Re%20Marine%20Based%20Harvesting-IEDE.pdf">cultures, economies, knowledge and food systems</a>. </p>
<p>The sea ice decline makes navigation <a href="https://sikuatlas.ca/index.html?module=module.sikuatlas.sea_ice">more dangerous and less predictable</a>. It can <a href="https://doi.org/10.1007/s10113-008-0060-x">change the timing and location of harvests, increase harvesting costs and reduce how much is harvested</a>. </p>
<p>This can lead to <a href="https://www.jstor.org/stable/41758937">less food and money</a>, more <a href="https://doi.org/10.1017/S1368980020000117">anxiety about food access</a> and <a href="https://doi.org/10.1017/S1368980020002402">greater reliance on less healthy imported foods</a>, negatively affecting <a href="https://www.itk.ca/wp-content/uploads/2021/07/ITK_Food-Security-Strategy-Report_English_PDF-Version.pdf">food security</a> and mental health.</p>
<h2>4. Seafood decline</h2>
<p>Seafood is a key source of protein and essential nutrients, especially where they’re in short supply from other <a href="https://doi.org/10.3390/ijerph17238818">locally accessible foods</a>. </p>
<p>But climate change is already <a href="https://doi.org/10.1111/j.1365-2486.2009.01995.x">driving species towards the North and South Poles.</a>. This may lead to <a href="https://doi.org/10.1038/534317a">serious declines in seafood catches by 2050</a> and negatively affect millions globally, with the most severe impacts in developing countries and among <a href="https://doi.org/10.1371/journal.pone.0166681">coastal Indigenous Peoples</a>. </p>
<figure class="align-center ">
<img alt="A red and gold salmon swimming" src="https://images.theconversation.com/files/413614/original/file-20210728-17-1xna163.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/413614/original/file-20210728-17-1xna163.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=379&fit=crop&dpr=1 600w, https://images.theconversation.com/files/413614/original/file-20210728-17-1xna163.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=379&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/413614/original/file-20210728-17-1xna163.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=379&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/413614/original/file-20210728-17-1xna163.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=476&fit=crop&dpr=1 754w, https://images.theconversation.com/files/413614/original/file-20210728-17-1xna163.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=476&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/413614/original/file-20210728-17-1xna163.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=476&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Warmer water temperatures are making salmon more susceptible to predators, parasites and disease — and they’re shrinking in size.</span>
<span class="attribution"><span class="source">THE CANADIAN PRESS/Jonathan Hayward</span></span>
</figcaption>
</figure>
<p>Projected <a href="https://doi.org/10.1371/journal.pone.0145285">declines of salmon and herring catches in British Columbia</a>, for instance, may lead to inadequate intakes of several vitamins, minerals and fatty acids <a href="https://doi.org/10.1371/journal.pone.0211473">for coastal First Nations</a>. When diets shift to processed foods, high in calories and sodium, the <a href="https://doi.org/10.1111/j.1753-4887.2011.00456.x">risk of developing Type 2 diabetes and cardiovascular disease increase</a>. </p>
<h2>5. Hazards in ocean waters, air and seafood</h2>
<p><a href="http://doi.org/10.5334/aogh.2831">The ocean is polluted</a> with mercury, industrial chemicals, pharmaceuticals, microplastics — and more. It also harbours many naturally occurring micro-organisms, like <a href="https://dx.doi.org/10.1128%2FMMBR.68.3.403-431.2004">flesh-eating bacteria and cholera</a>, and <a href="https://doi.org/10.1289/ehp.00108s1133">toxins</a>. </p>
<p>These can become dangerous to human health when ocean chemistry and temperature, and other marine ecosystem dynamics, are altered, which can lead to <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5016795/pdf/nihms-681151.pdf">shellfish poisoning</a>, <a href="https://theconversation.com/climate-change-and-overfishing-are-boosting-toxic-mercury-levels-in-fish-122748">mercury exposure and poisoning</a> and other illnesses. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-and-overfishing-are-boosting-toxic-mercury-levels-in-fish-122748">Climate change and overfishing are boosting toxic mercury levels in fish</a>
</strong>
</em>
</p>
<hr>
<p>Climate change will <a href="https://doi.org/10.1111/gcb.13667">alter the distribution and severity of pollutants</a>. For example, <a href="https://doi.org/10.1016/j.tim.2016.09.008">infections from some strains of vibrio bacteria</a> may become more <a href="https://www.contagionlive.com/view/cluster-of-v-vulnificus-pops-up-in-previously-nonendemic-area">frequent and widespread</a> with warming waters. Even <a href="https://doi.org/10.1038/s41586-019-1468-9">rising methylmercury concentrations in tuna</a> have been linked to increasing sea water temperature.</p>
<h2>Navigating forward</h2>
<p>Despite the many connections between <a href="https://doi.org/10.1016/j.oneear.2020.05.013">ocean health</a> and human health, <a href="https://www.doi.org/10.1002/pan3.10038">global ocean governance</a> has rarely considered the latter. Policies like the U.S. <a href="https://uscode.house.gov/view.xhtml?path=/prelim@title33/chapter44&edition=prelim">Oceans and Human Health Act</a>, and related <a href="https://doi.org/doi:10.1186/1476-069X-7-S2-S1">research and training centres</a>, can bolster the collaboration and co-ordination needed across diverse agencies, sectors and disciplines to support healthy oceans and people. </p>
<p>This interdisciplinary infrastructure and capacity is needed to develop the information (like <a href="https://doi.org/10.3389/fmars.2021.631732">early warning systems</a>), policies, plans and management systems to mitigate and respond to emerging public health threats from the ocean. We must broaden the framing of ocean change <a href="https://bcgreencare.ca/climate-change-and-role-of-HA">from an “environmental issue” to one that includes human health</a> and <a href="https://www.oceanpanel.org/sites/default/files/2020-04/towards-ocean-equity.pdf">social equity</a>. </p>
<p>As the world turns to the ocean for “<a href="https://www.worldbank.org/en/news/infographic/2017/06/06/blue-economy">blue economies</a>,” “<a href="https://thewalrus.ca/blue-space-is-the-new-green-space/">blue spaces</a>,” “<a href="https://doi.org/10.1093/heapro/day103">blue health care</a>” and “<a href="http://dx.doi.org/10.2139/ssrn.3854678">blue prescriptions</a>,” it’s important to remember the ocean as a site of historic and enduring oppression, <a href="https://doi.org/10.1080/02614367.2019.1640774">exclusion</a>, <a href="https://ore.exeter.ac.uk/repository/bitstream/handle/10871/39233/Hydrophilia_Bell%20et%20al_accepted_CH10_2019.pdf?sequence=2">racism</a> and other violations of <a href="https://e360.yale.edu/features/lawless-ocean-the-link-between-human-rights-abuses-and-overfishing">human rights</a>. </p>
<p>For the health of the ocean and its peoples, <a href="https://oceannexus.uw.edu/our-community/un-decade-of-ocean-science-for-sustainable-development/">the ocean needs to become more equitable</a> — and that means reconciling and healing the histories and relationships of cultures, values and knowledge systems that all share the sea.</p><img src="https://counter.theconversation.com/content/162341/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tiff-Annie Kenny receives funding from the Canadian Institute of Health Research, ArcticNet, Sentinelle Nord (Apogee Canada) and Genome Canada.
</span></em></p><p class="fine-print"><em><span>Mélanie Lemire receives funding from Indigenous Services Canada, Health Canada, Crown-Indigenous Relations and Northern Affairs Canada (CIRNAC), Sentinelle Nord (Apogee Canada), Meopar, Genome Canada and Canadian Institute for Heath Research</span></em></p><p class="fine-print"><em><span>Malaya Bishop 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>
As the climate changes, the ocean is also changing. And that’s putting our health at risk.
Tiff-Annie Kenny, Adjunct professor, Faculté de médecine, Université Laval
Malaya Bishop, Research Assistant, Department of Biology - Food Security, Climate Change, and Indigenous Health, L’Université d’Ottawa/University of Ottawa
Mélanie Lemire, Associate professor, Department of Social and Preventive Medicine, Université Laval
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/158769
2021-04-12T02:39:03Z
2021-04-12T02:39:03Z
Cyclone Seroja just demolished parts of WA – and our warming world will bring more of the same
<figure><img src="https://images.theconversation.com/files/394399/original/file-20210412-21-d4o1li.jpg?ixlib=rb-1.1.0&rect=0%2C31%2C3000%2C1962&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Bureau of Meteorology</span></span></figcaption></figure><p>Tropical Cyclone Seroja <a href="https://www.abc.net.au/news/2021-04-12/cyclone-seroja-wreaks-havoc-wa-one-mile-jetty-destroyed/100062020">battered</a> parts of Western Australia’s coast on Sunday night, badly damaging buildings and leaving thousands of people without power. While the full extent of the damage caused by the Category 3 system is not yet known, the event was unusual.</p>
<p>I specialise in reconstructing long-term natural records of extreme events, and my historic and prehistoric data show cyclones of this intensity rarely travel as far south as this one did. In fact, it has happened only 26 times in the past 5,000 years. </p>
<p>Severe wind gusts hit the towns of Geraldton and Kalbarri – towns <a href="https://www.smh.com.au/national/red-alert-issued-as-tropical-cyclone-seroja-threat-looms-off-western-australia-20210411-p57i9e.html">not built</a> to withstand such conditions.</p>
<p>Unfortunately, climate change is likely to mean disasters such as Cyclone Seroja will become more intense, and will be seen further south in Australia more often. In this regard, Seroja may be a timely wake-up call. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1381222119783034881"}"></div></p>
<h2>Seroja: bucking the cyclone trend</h2>
<p>Cyclone Seroja initially piqued interest because as it developed off WA, it interacted with another tropical low, Cyclone Odette. This <a href="https://www.theguardian.com/australia-news/2021/apr/09/rare-clash-of-cyclones-off-western-australia-excites-weather-enthusiasts-across-the-globe">rare phenomenon</a> is known as the Fujiwhara Effect.</p>
<p>Cyclone Seroja hit the WA coast between the towns of Kalbarri and Gregory at about 8pm local time on Sunday. According to the Bureau of Meteorology it produced wind gusts up to 170 km/hour. </p>
<p>Seroja then moved inland north of Geraldton, weakening to a category 2 system with wind gusts up to 120 km/hour. It then tracked further east and has since been downgraded to a tropical low.</p>
<p>The cyclone’s southward track was historically unusual. For Geraldton, it was the <a href="https://twitter.com/BOM_WA/status/1381307724386996224">first</a> Category 2 cyclone impact since 1956. Cyclones that make landfall so far south on the WA coast are usually less intense, for several reasons. </p>
<p>First, intense cyclones draw their energy from warm sea surface temperatures. These temperatures typically become cooler the further south of the tropics you go, depleting a cyclone of its power.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1381243299277668353"}"></div></p>
<p>Second, cyclones need relatively low speed winds in the middle to upper troposphere – the part of the atmosphere closest to Earth, where the weather occurs. Higher-speed winds there cause the cyclone to tilt and weaken. In the Australian region, these higher wind speeds are more likely the further south a cyclone travels. </p>
<p>Third, most cyclones make landfall in the northern half of WA where the coast protrudes far into the Indian Ocean. Cyclones here typically form in the Timor Sea and move southward or south-west away from WA before curving southeast, towards the landmass. </p>
<p>For a cyclone to cross the coast south of about Carnarvon, it must travel a considerable distance towards the south-west into the Indian Ocean. This was the case with Seroja – winds steered it away from the WA coast before they weakened, allowing the cyclone to curve back towards land.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1381233745613627393"}"></div></p>
<h2>Reading the ridges</h2>
<p>My colleagues and I have devised <a href="https://www.sciencedirect.com/science/article/pii/S0277379110004324?casa_token=dYx5_aZfT80AAAAA:lymI1KwsVKaDlSLVKZmfpZCvzjpnciUThvJPSIDaVaf0WRoOBHYl_TEM0pD1V8BFhCOwRiYqBPc">a method</a> to estimate how often and where cyclones make landfall in Australia.</p>
<p>As cyclones approach the coast, they generate storm surge – abnormal sea level rise – and large waves. The surge and waves pick up sand and shells from the beaches and transport them inland, sometimes for several hundred metres. </p>
<p>These materials are deposited into ridges which stand many metres above sea level. By examining these ridges and geologically dating the materials within them, we can determine how often and intense the cyclones have been over thousands of years. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/our-new-model-shows-australia-can-expect-11-tropical-cyclones-this-season-146318">Our new model shows Australia can expect 11 tropical cyclones this season</a>
</strong>
</em>
</p>
<hr>
<p>At Shark Bay, just north of where Seroja hit the coast, a series of 26 ridges form a “ridge plain” made entirely of one species of a marine cockle shell (Fragum eragatum). The sand at beaches near the plain are also made entirely of this shell.</p>
<p>The <a href="https://www.sciencedirect.com/science/article/pii/S0277379110004324?casa_token=dYx5_aZfT80AAAAA:lymI1KwsVKaDlSLVKZmfpZCvzjpnciUThvJPSIDaVaf0WRoOBHYl_TEM0pD1V8BFhCOwRiYqBPc">ridge record shows</a> over the past 5,000 years, cyclones of Seroja’s intensity, or higher, have crossed the coast in this region about every 190 years – so about 26 times. Some 14 of these cyclones were more intense than Seroja.</p>
<p>The record shows no Category 5 cyclones have made landfall here over this time. The ridge record prevents us from knowing the frequency of less intense storms. But Bureau of Meteorology cyclone <a href="http://www.bom.gov.au/cyclone/tropical-cyclone-knowledge-centre/history/tracks/">records</a> since the early 1970s shows only a few crossed the coast in this region, and all appear weaker than Seroja.</p>
<figure class="align-center ">
<img alt="Emergency services crews in the WA town of Geraldton, preparing ahead of the arrival of Tropical Cyclone Seroja" src="https://images.theconversation.com/files/394382/original/file-20210411-15-ybb7ib.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/394382/original/file-20210411-15-ybb7ib.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/394382/original/file-20210411-15-ybb7ib.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/394382/original/file-20210411-15-ybb7ib.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/394382/original/file-20210411-15-ybb7ib.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=458&fit=crop&dpr=1 754w, https://images.theconversation.com/files/394382/original/file-20210411-15-ybb7ib.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=458&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/394382/original/file-20210411-15-ybb7ib.jpg?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">
<figcaption>
<span class="caption">Emergency services crews in the WA town of Geraldton, preparing ahead of the arrival of Tropical Cyclone Seroja - an event rarely seen this far south.</span>
<span class="attribution"><span class="source">Department of Fire and Emergency Services WA</span></span>
</figcaption>
</figure>
<h2>Cyclones under climate change</h2>
<p>So why does all this matter? Cyclones can kill and injure people, damage homes and infrastructure, cause power and communication outages, contaminate water supplies and more. Often, the most disadvantaged populations are worst affected. It’s important to understand past and future cyclone behaviour, so communities can prepare.</p>
<p>Climate change is expected to alter cyclone patterns. The overall number of tropical cyclones in the Australian region is expected to decrease. But their intensity will <a href="http://www.bom.gov.au/cyclone/climatology/trends.shtml">likely increase</a>, bringing stronger wind and heavier rain. And they may form <a href="https://www.pnas.org/content/115/45/11543.short">further south</a> as the Earth warms and the tropical zone <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020JD033158">expands</a> poleward. </p>
<p>This may mean cyclones of Seroja’s intensity are likely to become frequent, and communities further south on the WA coast may become more prone to cyclone damage. This has big implications for coastal planning, engineering and disaster management planning. </p>
<p>In particular, it may mean homes further south must be built to cope with stronger winds. Storm surge may also worsen, inundating low-lying coastal land.</p>
<p>Global climate models are developing all the time. As they improve, we will gain a more certain picture of how tropical cyclones will change as the planet warms. But for now, Seroja may be a sign of things to come. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/wetlands-have-saved-australia-27-billion-in-storm-damage-over-the-past-five-decades-153638">Wetlands have saved Australia $27 billion in storm damage over the past five decades</a>
</strong>
</em>
</p>
<hr>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/qTV8Qft6Nco?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p><em>This article is part of Conversation series on the nexus between disaster, disadvantage and resilience. It is supported by a philanthropic grant from the Paul Ramsay foundation. Read the rest of the stories <a href="https://theconversation.com/au/topics/disaster-and-resilience-series-97537">here</a>.</em></p><img src="https://counter.theconversation.com/content/158769/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Nott receives funding from the Australian Research Council. </span></em></p>
Climate change is likely to mean disasters such as Cyclone Seroja will become more intense, and be seen further south in Australia more often.
Jonathan Nott, Professor of Physical Geography, James Cook University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/153638
2021-01-21T18:49:47Z
2021-01-21T18:49:47Z
Wetlands have saved Australia $27 billion in storm damage over the past five decades
<figure><img src="https://images.theconversation.com/files/379865/original/file-20210121-21-13liy5h.jpg?ixlib=rb-1.1.0&rect=0%2C11%2C2460%2C1624&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Australia is in the midst of tropical cyclone season. As we write, a <a href="https://www.abc.net.au/news/2021-01-20/cyclone-lucas-wa-warning-tourists-urged-to-leave/13075018">cyclone is forming</a> off Western Australia’s Pilbara coast, and earlier in the week Queenslanders were bracing for a cyclone in the state’s <a href="https://www.abc.net.au/news/2021-01-18/qld-tropical-cyclone-kimi-category-one-cairns-townsville/13066832">far north</a> (which thankfully, didn’t hit).</p>
<p>Australia has always experienced cyclones. But here and around the world, climate change means the cyclone threat <a href="https://www.pnas.org/content/117/22/11975">is growing</a> – and so too is the potential damage bill. Disadvantaged populations are often most at risk.</p>
<p>Our <a href="https://www.sciencedirect.com/science/article/pii/S2212041620301479">recent research</a> shows 54 cyclones struck Australia in the 50 years between 1967 and 2016, causing about A$3 billion in damage. We found the damages would have totalled approximately A$30 billion, if not for coastal wetlands.</p>
<p>Wetlands such as mangroves, swamps, lakes and lagoons bear the brunt of much storm damage to coast, helping protect us and our infrastructure. But over the past 300 years, <a href="https://www.publish.csiro.au/mf/mf14173">85% of the world’s wetland area</a> has been destroyed. It’s clear we must urgently preserve the precious little wetland area we have left.</p>
<figure class="align-center ">
<img alt="A wetland close to coastal development." src="https://images.theconversation.com/files/379869/original/file-20210121-21-140jgb6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379869/original/file-20210121-21-140jgb6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379869/original/file-20210121-21-140jgb6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379869/original/file-20210121-21-140jgb6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379869/original/file-20210121-21-140jgb6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379869/original/file-20210121-21-140jgb6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379869/original/file-20210121-21-140jgb6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Wetland areas provide important protection from cyclones.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>A critical buffer</h2>
<p>National disasters cost Australia as much as <a href="http://australianbusinessroundtable.com.au/assets/reports/media-release-nov-11.pdf">A$18 billion each year</a> on average. About one-quarter of this is <a href="https://www.sciencedirect.com/science/article/abs/pii/S221242091630440X">due to</a> cyclone damage. </p>
<p>Wetlands can mitigate cyclone and hurricane damage, by absorbing storm surges and slowing winds. For example in August 2020, Hurricane Laura hit the United States’ midwest. Massive damage was predicted, including a 6.5-metre storm surge extending 65 kilometres inland. </p>
<p>However the surge was one metre at most – largely because the storm drove straight into a <a href="https://www.theguardian.com/us-news/2020/oct/02/weatherwatch-hurricane-laura-storm-surge-that-went-astray">massive wetland that absorbed most of the predicted flood</a>.</p>
<p>In Australia, wetlands are lost through intentional infilling or drainage for mosquito control, or to create land for infrastructure and agriculture. They’re also lost due to pollution and upstream changes to water flows.</p>
<figure class="align-center ">
<img alt="Caley Valley Wetlands, next to Adani's Abbot Point coal terminal." src="https://images.theconversation.com/files/379868/original/file-20210121-19-ezoabd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379868/original/file-20210121-19-ezoabd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379868/original/file-20210121-19-ezoabd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379868/original/file-20210121-19-ezoabd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379868/original/file-20210121-19-ezoabd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379868/original/file-20210121-19-ezoabd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379868/original/file-20210121-19-ezoabd.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">Australia’s wetlands are at risk. Pictured is the Caley Valley Wetlands, next to Adani’s Abbot Point coal terminal. Adani was fined for releasing polluted water into the wetland.</span>
<span class="attribution"><span class="source">Gary Farr/ACF</span></span>
</figcaption>
</figure>
<h2>Putting a price on cyclone protection</h2>
<p>Our research set out to determine the financial value of the storm protection provided by Australia’s wetlands.</p>
<p>We examined the 54 cyclones that struck Australia in the five decades to 2016. We gathered data including:</p>
<ul>
<li>physical damage wrought in each storm swath (or storm path)</li>
<li>gross domestic product (GDP) in the storm’s path </li>
<li>maximum windspeed during each storm, which helps predict damage</li>
<li>total area of wetlands in each swath. </li>
</ul>
<p>Using a powerful type of statistics called Bayesian analysis, we estimated the extent to which GDP, windspeed and wetland area affected total damage. This allowed us to estimate damage caused in the absence of wetlands.</p>
<p>We found for every hectare of wetland, about A$4,200 per year in cyclone damage was avoided. This means the A$3 billion in cyclone damage over the past 50 years would have totalled approximately A$30 billion, if not for coastal wetlands.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/restoring-a-gem-in-the-murray-darling-basin-the-success-story-of-the-winton-wetlands-140337">Restoring a gem in the Murray-Darling Basin: the success story of the Winton Wetlands</a>
</strong>
</em>
</p>
<hr>
<p>Importantly, the percentage of damage averted falls rapidly as wetland area decreases. And the protection afforded by a single hectare of wetland increases drastically if there are fewer other wetlands in the path of the storm. This makes protecting remaining wetland even more critical.</p>
<p>If the average cyclone path in Australia were to contain around 30,000 hectares of wetlands, it would avert about 90% of potential storm damage. If the wetland area dropped to 3,000 hectares, only about 30% of damage would be averted.</p>
<p>Climate change is making cyclones worse. By 2050, Australia’s annual damage bill could be as <a href="https://www.sciencedirect.com/science/article/pii/S2212041620301479">high as A$39 billion</a>, assuming current levels of wetlands are maintained.</p>
<p>Seawalls and other artificial structures can be built along the coast to protect from storms. However, research in China has found wetlands are more cost-effective and efficient than man-made structures at <a href="https://www.sciencedirect.com/science/article/pii/S0048969718347648">preventing cyclone damage</a>.</p>
<p>Unlike man-made structures, wetlands maintain themselves. Their only “cost” is the opportunity cost of not being able to use the land for something else.</p>
<figure class="align-center ">
<img alt="People inspect cyclone damage" src="https://images.theconversation.com/files/379870/original/file-20210121-21-j4mz5e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379870/original/file-20210121-21-j4mz5e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379870/original/file-20210121-21-j4mz5e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379870/original/file-20210121-21-j4mz5e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379870/original/file-20210121-21-j4mz5e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379870/original/file-20210121-21-j4mz5e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379870/original/file-20210121-21-j4mz5e.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">Wetlands can help prevent cyclone damage, such as this wrought in Queensland during Cyclone Debbie in 2017.</span>
<span class="attribution"><span class="source">Dan Peled/AAP</span></span>
</figcaption>
</figure>
<h2>Keeping wetlands safe</h2>
<p>According to recent analysis by the authors, which is currently under peer review, global wetlands provide US$447 billion (A$657 billion) worth of protection from storms each year.</p>
<p>Of course, wetlands provide benefits beyond storm protection. They store carbon, regulate our climate and control flooding. They also absorb waste including pollutants and carbon, provide animal habitat and places for human recreation. </p>
<p>Wetlands are an incredibly important resource. It’s critical we protect them from development and keep them healthy, so they can continue to provide vital services.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/our-new-model-shows-australia-can-expect-11-tropical-cyclones-this-season-146318">Our new model shows Australia can expect 11 tropical cyclones this season</a>
</strong>
</em>
</p>
<hr>
<p><em>This story is part of a series The Conversation is running on the nexus between disaster, disadvantage and resilience. It is supported by a philanthropic grant from the Paul Ramsay foundation. You can read the rest of the stories <a href="https://theconversation.com/au/topics/disaster-and-resilience-series-97537">here</a>.</em></p><img src="https://counter.theconversation.com/content/153638/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>
Wetlands bear the brunt of much storm damage to the coast. But over the past 300 years, 85% of the world’s wetland area has been destroyed.
Obadiah Mulder, PhD Candidate in Computational Biology, USC Dornsife College of Letters, Arts and Sciences
Ida Kubiszewski, Associate Professor, Crawford School of Public Policy, Australian National University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/146804
2020-09-24T12:25:41Z
2020-09-24T12:25:41Z
What makes hurricanes stall, and why is that so hard to forecast?
<figure><img src="https://images.theconversation.com/files/359672/original/file-20200923-18-1wfbxlv.jpg?ixlib=rb-1.1.0&rect=3%2C3%2C2560%2C1703&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When Hurricane Dorian, seen here from the International Space Station, stalled over the Bahamas in September 2019, its winds, rain and storm surge devastated the islands.</span> <span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/145559/a-devastating-stall-by-hurricane-dorian">NASA</a></span></figcaption></figure><p>A lot can go wrong when hurricanes stall. Their destructive winds last longer. The storm surge can stay high. And the rain keeps falling.</p>
<p>During Hurricane Sally, Naval Air Station Pensacola reported <a href="https://www.pnj.com/story/news/2020/09/16/hurricane-sally-dumps-18-inches-rain-pensacola-landfall-nears/5814251002/">more than 24 inches</a> of rain as the storm’s forward movement slowed to walking speed along the coast. We saw similar effects when the decaying <a href="https://www.nhc.noaa.gov/data/tcr/AL092017_Harvey.pdf">Hurricane Harvey sat over Houston</a> for four days in 2017 and dropped up to 60 inches of rain in some areas – that’s 5 feet! Hurricane <a href="https://www.nhc.noaa.gov/archive/2019/al05/al052019.public.037.shtml?">Dorian slowed to 1 mile per hour</a> in 2019 as its winds and rain battered the Bahamas for two days.</p>
<p><a href="https://www.wpc.ncep.noaa.gov/tropical/qpf/Beta_ero.gif">Post-Tropical Storm Beta</a> in 2020 was another stalling storm, flooding streets in Houston as it slowly crept up the Texas coast and eventually moved into Louisiana. </p>
<p>Research shows that stalling <a href="https://www.nature.com/articles/s41612-019-0074-8">has become more common</a> for tropical cyclones in the North Atlantic since the mid-20th century and that their average forward speed has also slowed.</p>
<p>So, why does this happen? Here are answers to some questions I hear as a meteorologist about how storm systems move and why they sometimes slow to a crawl.</p>
<h2>Why do some storms move fast and others slow?</h2>
<p>Hurricanes are steered by the winds around them. We call this the atmospheric flow. If those winds are moving fast, they’ll move the storm fast. You can picture it as a <a href="https://www.npr.org/2019/09/04/757394753/is-climate-change-contributing-to-slower-moving-hurricanes">leaf floating on a stream</a>. If the stream moves slower, the leaf moves slower. When the flow turns, the leaf turns.</p>
<p>What the atmospheric flow is doing in a given location on a day-to-day basis can be pretty variable. How quickly a given storm will move depends on such things as whether a high-pressure ridge is nearby, or if there is low pressure where air flows counterclockwise. And steering currents can weaken if a storm is caught between different kinds of flow. </p>
<p>One factor that affects flow in the Atlantic is a high pressure system called <a href="https://svs.gsfc.nasa.gov/10069">the Bermuda high</a>. Many hurricanes that form east of the Lesser Antilles get steered by the Bermuda high. </p>
<h2>What does climate change have to do with it?</h2>
<p>The Arctic has been warming about twice as fast as the mid-latitudes, where most of the U.S. is located. That’s reducing the temperature distribution, or gradient, between the Arctic and the mid-latitudes. And that can <a href="https://www.nature.com/articles/s41467-018-05256-8">affect the steering currents</a>, such as those associated with the Bermuda high.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-s7zOubwXmc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>On average, the forward <a href="https://www.nature.com/articles/s41612-019-0074-8">speed of hurricanes has been slowing down</a>. Simulations of tropical storm behavior have <a href="https://www.sciencedaily.com/releases/2020/04/200422151312.htm">suggested that this slowing will continue</a> as average global temperatures warm, particularly in the mid-latitudes.</p>
<p>A warmer atmosphere also means storms can tap into more moisture. As temperature increases, it’s easier for water to evaporate into vapor. Imagine setting your laundry out to dry on a hot day versus a cool day. Your laundry will dry faster if it’s hot out because the liquid water can become vapor more easily. Your laundry also feels cool when water evaporates from it because evaporation is a cooling process. In a hurricane, the opposite happens – water vapor reverts to liquid as cloud droplets, which means energy gets released, and that energy powers the storm.</p>
<p>If a storm slows, and if it has access to more moisture, it can dump more rain and produce a greater storm surge due to the slow motion.</p>
<h2>Why are slow-moving storms so dangerous?</h2>
<p>When a hurricane approaches land, there are multiple possible effects: the wind from the hurricane itself, the rainfall the hurricane produces and the <a href="https://theconversation.com/what-is-a-hurricane-storm-surge-and-why-is-it-so-dangerous-145369">storm surge</a> that’s pushed by the hurricane.</p>
<p>Inland, excessive rain can cause low-lying areas to fill with water and also leads to river and stream flooding. Slow-moving storms mean longer periods of heavy rain near the coast, so the inland flooding that heads downstream can meet the storm surge moving upstream, which is terrifying. </p>
<p>North Carolina saw that in 2018 when <a href="https://www.weather.gov/mhx/Florence2018#:%7E:text=The%20historic%20legacy%20of%20Hurricane,catastrophic%20and%20life%2Dthreatening%20flooding.">Hurricane Florence</a> pushed a 10-foot storm surge into the Neuse River while dumping more than 20 inches of rain across a large part of the state.</p>
<h2>Why is it so hard to forecast a slow mover?</h2>
<p>To forecast a storm, we look at what we call “dynamical guidance” – computer models that simulate the atmosphere and make a prediction based on our knowledge of physics. Forecasters put in variables such as the current wind, temperature and pressure, and the computer uses that starting point to simulate what the weather could be hours or days into the future.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p>But our initial picture of the atmosphere is not perfect, and the computer can work only with what we give it. Each computer model is also a little different. They’re all based in the laws of physics, but the assumptions they make and how they take in data can vary from model to model.</p>
<p>When a storm is moving slowly, what could be a small difference in the initial atmospheric picture can result in big differences over the next few days. Why? When steering currents are weak, like 5 mph, a speed difference of 2 mph in the initial flow has a bigger impact than when the currents are strong, so it’s easier for the models to produce forecasts that end up looking different from what eventually happens.</p><img src="https://counter.theconversation.com/content/146804/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kimberly Wood receives funding from the National Science Foundation.</span></em></p>
Hurricane stalling has become common over the past half-century, and their average forward speed has also slowed.
Kimberly Wood, Assistant Professor of Meteorology, Mississippi State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/146506
2020-09-18T17:29:24Z
2020-09-18T17:29:24Z
The 2020 Atlantic hurricane season is so intense, it just ran out of storm names
<figure><img src="https://images.theconversation.com/files/358858/original/file-20200918-16-xszf74.jpg?ixlib=rb-1.1.0&rect=0%2C3%2C2574%2C1817&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hurricanes Marco and Laura swept through the Gulf of Mexico just two days apart in August 2020.</span> <span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/147164/us-gulf-coast-braces-for-marco-and-laura">Joshua Stevens/NASA Earth Observatory</a></span></figcaption></figure><p>Here’s how active this year’s Atlantic hurricane season has been: When <a href="https://www.nhc.noaa.gov/#Wilfred">Tropical Storm Wilfred</a> formed on Sept. 18, the National Hurricane Center exhausted its list of storm names for only the second time since <a href="https://www.nhc.noaa.gov/aboutnames_history.shtml">naming began in 1950</a>. Within hours, two more storm had formed – now known as <a href="https://www.nhc.noaa.gov/archive/2020/al24/al242020.public.001.shtml?">Alpha</a> and <a href="https://www.nhc.noaa.gov/text/refresh/MIATCPAT2+shtml/182052.shtml">Beta</a>.</p>
<p>Even more surprising is that we reached the 23rd tropical storm of the year, Beta, <a href="http://arashi.geosci.msstate.edu/2020/AtlanticTCformation.html">more than a month earlier</a> than in 2005, the only other year on record with so many named storms. </p>
<p>The 2020 Atlantic hurricane season is far from over. With the new storms, forecasters shifted from the alphabetical list of people’s names to letters of the Greek alphabet. The 2005 season had six Greek-letter storms, ending with Zeta.</p>
<p>So, why is the Atlantic so active this year? <a href="http://arashi.geosci.msstate.edu/">Meteorologists like myself</a> have been following a few important differences, including many tropical storms forming closer to the U.S. coast.</p>
<h2>What’s causing so many tropical cyclones?</h2>
<p>When a disturbance – a large blob of convective clouds, or thunderstorms – exists over the Atlantic Ocean, certain atmospheric conditions will help it grow into a tropical cyclone.</p>
<p>Warm water and lots of moisture help disturbances gain strength. Low vertical wind shear, meaning the wind speeds and directions don’t change much as you get higher in the atmosphere, is important since this shear can prevent convection from growing. And instability enables parcels of air to rise upward and keep going to build thunderstorms.</p>
<p>This year, sea surface temperatures have been above average across much of the Atlantic Ocean and wind shear has been below average. That means it’s been more conducive than usual to the formation of tropical cyclones.</p>
<p>La Niña probably also has something to do with it. La Niña is El Niño’s opposite – it happens when sea surface temperatures in the eastern and central Pacific are below average. That cooling affects weather patterns across the U.S. and elsewhere, including weakening wind shear in the Atlantic basin. NOAA determined in early September that we had <a href="https://www.noaa.gov/news/la-nina-develops-during-peak-hurricane-season">entered a La Niña climate pattern</a>. That pattern has been building up for weeks, so these trending conditions could have contributed to how favorable the Atlantic has been to tropical cyclones this year.</p>
<figure class="align-center ">
<img alt="Satellite image of five tropical storms." src="https://images.theconversation.com/files/358872/original/file-20200918-20-twy3hw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358872/original/file-20200918-20-twy3hw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=442&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358872/original/file-20200918-20-twy3hw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=442&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358872/original/file-20200918-20-twy3hw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=442&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358872/original/file-20200918-20-twy3hw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=555&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358872/original/file-20200918-20-twy3hw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=555&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358872/original/file-20200918-20-twy3hw.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">The storms Paulette, Rene, Sally, Teddy and Vicky were all active in the Atlantic on Sept. 14, 2020.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Paulette,_Rene,_Sally,_Teddy_and_Vicky_2020-09-14_1550Z.jpg">NOAA</a></span>
</figcaption>
</figure>
<h2>An unusual twist off the US coast</h2>
<p>Four hurricanes have hit the U.S. coast this year – <a href="https://www.nhc.noaa.gov/archive/2020/HANNA_graphics.php">Hanna</a>, <a href="https://www.nhc.noaa.gov/archive/2020/ISAIAS_graphics.php">Isaias</a>, <a href="https://theconversation.com/a-burning-chemical-plant-may-be-just-the-tip-of-hurricane-lauras-damage-in-this-area-of-oil-fields-and-industry-145217">Laura</a> and <a href="https://www.nhc.noaa.gov/archive/2020/SALLY.shtml">Sally</a>, which is <a href="https://doi.org/10.1175/BAMS-D-17-0184.1">more than usual</a> by this point in the hurricane season. But we also have observed many short-lived tropical storms that had less impact.</p>
<p>When a tropical cyclone develops from a disturbance that forms over Africa, it has a lot of ocean ahead of it with room to get organized and gain strength. </p>
<p>But this year, many storms have formed farther north, closer to the U.S. coast.</p>
<p>Most came from disturbances that didn’t look too promising – until they moved over the Gulf Stream. The Gulf Stream is a <a href="https://scijinks.gov/gulf-stream/">large ocean current</a> that carries warm water from the Gulf of Mexico, up the East Coast and into the North Atlantic. Tropical cyclones typically need sea surface temperatures <a href="https://earthobservatory.nasa.gov/images/146991/gearing-up-for-an-active-2020-hurricane-season">over 80 degrees Fahrenheit</a> to form, and the warm water along the Gulf Stream can help disturbances spin up into tropical cyclones.</p>
<p>Because these tropical storms were already fairly far north, however, they didn’t have much time to gain strength. Meteorologists haven’t yet studied why so many storms formed this way this season, but it’s possible that it’s due to both warmer-than-normal Atlantic Ocean waters and the position of the Gulf Stream.</p>
<p><iframe id="J7uED" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/J7uED/10/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>Lots of firsts as the season breaks records</h2>
<p>One of the biggest surprises this year has been how consistently we have been breaking records for <a href="http://arashi.geosci.msstate.edu/2020/AtlanticTCformation.html">earliest named storm for their rank</a>. For example, <a href="https://www.nhc.noaa.gov/archive/2020/EDOUARD_graphics.php">Edouard</a> became the earliest fifth named storm on July 6, beating 2005’s <a href="https://www.wpc.ncep.noaa.gov/tropical/rain/emily2005.html">Emily</a> by a week. <a href="https://www.nhc.noaa.gov/archive/2020/FAY_graphics.php">Fay</a> was the earliest sixth named storm, showing up almost two weeks earlier than <a href="https://www.nhc.noaa.gov/data/tcr/index.php?season=2005&basin=atl">Franklin</a> did in 2005. </p>
<p>Wilfred was the earliest to run out the list of designated storm names. In 2005, Hurricane Wilma formed on Oct. 17, but it ended up being the year’s 22nd named storm chronologically, not the 21st like Wilfred, because an unnamed subtropical storm formed on Oct. 4. The National Hurricane Center discovered this unnamed storm during a post-season analysis. </p>
<p>In all, the 2005 season had 28 qualifying storms. The <a href="https://public.wmo.int/en/our-mandate/focus-areas/natural-hazards-and-disaster-risk-reduction/tropical-cyclones/Naming">list of Atlantic tropical cyclone names</a> skips letters where easy-to-distinguish names are harder to find, like Q and Z, then moves to the Greek alphabet. Could we run out of Greek letters before hurricane season ends on Nov. 30? I don’t think anyone’s ready to consider that.</p>
<p><em>This article has been updated with Tropical Storm Beta forming.</em></p>
<p>[<em>Get our best science, health and technology stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-best">Sign up for The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/146506/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kimberly Wood receives funding from the National Science Foundation.</span></em></p>
It’s only happened twice since naming started in 1950, and there’s an unusual twist to where many of the storms formed this year.
Kimberly Wood, Assistant Professor of Meteorology, Mississippi State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/142657
2020-07-21T19:49:09Z
2020-07-21T19:49:09Z
Storm warning: a new long-range tropical cyclone outlook is set to reduce disaster risk for Pacific Island communities
<figure><img src="https://images.theconversation.com/files/348492/original/file-20200720-63094-c833s9.jpg?ixlib=rb-1.1.0&rect=44%2C40%2C2950%2C1549&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Photobank.kiev.ua/Shutterstock</span></span></figcaption></figure><p>Tropical cyclones are among the most destructive weather systems on Earth, and the Southwest Pacific region is <a href="https://www.worldbank.org/en/results/2012/04/01/pacific-islands-disaster-risk-reduction-and-financing-in-the-pacific">very exposed and vulnerable</a> to these extreme events.</p>
<p>Our latest research, <a href="https://www.nature.com/articles/s41598-020-67646-7">published today</a> in Scientific Reports, presents a new way of predicting the number of tropical cyclones up to four months ahead of the cyclone season, with outlooks tailored for individual island nations and territories. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/syr5Ohdzvj4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A new model predicts tropical cyclone counts up to four months in advance.</span></figcaption>
</figure>
<p>Tropical cyclones produce extreme winds, large waves and storm surges, intense rainfall and flooding — and account for almost <a href="http://documents1.worldbank.org/curated/en/840931468086057665/pdf/351940Natural1Hazards1report.pdf">three in four natural disasters</a> across the Southwest Pacific region.</p>
<p>Currently, Southwest Pacific forecasting agencies release a regional tropical cyclone outlook in October, one month ahead of the official start of the cyclone season in November. Our new model offers a long-range warning, issued monthly from July, to give local authorities more time to prepare. </p>
<p>Most importantly, this improvement on existing extreme weather warning systems may save more lives and mitigate damage by providing information up to four months ahead of the cyclone season. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/348503/original/file-20200721-18366-1e9rp13.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/348503/original/file-20200721-18366-1e9rp13.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/348503/original/file-20200721-18366-1e9rp13.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/348503/original/file-20200721-18366-1e9rp13.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/348503/original/file-20200721-18366-1e9rp13.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/348503/original/file-20200721-18366-1e9rp13.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/348503/original/file-20200721-18366-1e9rp13.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This map shows the expected number of tropical cyclones for the 2020/21 Southwest Pacific cyclone season (November to April).</span>
<span class="attribution"><span class="source">www.tcoutlook.com/latest-outlook</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Tropical cyclones and climate variability</h2>
<p>An average of <a href="https://www.nature.com/articles/s41598-020-67646-7">11 tropical cyclones</a> form in the Southwest Pacific region each season. Since 1950, tropical cyclones have <a href="https://www.emdat.be/">claimed the lives of nearly 1500</a> and have <a href="https://www.emdat.be/">affected more than 3 million people</a>. </p>
<p>In 2016, Cyclone Winston, a record-breaking severe category 5 event, was the <a href="https://journals.ametsoc.org/bams/article/98/8/Si/216075/State-of-the-Climate-in-2016">strongest cyclone</a> to make landfall across Fiji. It killed 44 people, injured 130 and seriously damaged around 40,000 homes. Damages totalled US$1.4 billion — making it the <a href="https://www.sbs.com.au/news/a-year-after-cyclone-winston-fiji-calls-for-global-action-on-climate-change">costliest cyclone</a> in Southwest Pacific history. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/winston-strikes-fiji-your-guide-to-cyclone-science-55134">Winston strikes Fiji: your guide to cyclone science</a>
</strong>
</em>
</p>
<hr>
<p>Tropical cyclones are erratic in their severity and the path they travel. Every cyclone season is different. Exactly where and when a tropical cyclone forms is driven by complex interactions between the ocean and the atmosphere, including the <a href="https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.5070">El Niño-Southern Oscillation</a>, <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.5406">sea surface temperatures</a> in the Indian Ocean, and many <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.4007">other climate influences</a>. </p>
<p>Capturing changes in all of these climate influences simultaneously is key to producing more accurate tropical cyclone outlooks. Our new tool, the Long-Range Tropical Cyclone Outlook for the Southwest Pacific (<a href="https://tcoutlook.com/">TCO-SP</a>), will assist forecasters and help local authorities to prepare for the coming season’s cyclone activity. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/348504/original/file-20200721-92332-t7hrsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/348504/original/file-20200721-92332-t7hrsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/348504/original/file-20200721-92332-t7hrsv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/348504/original/file-20200721-92332-t7hrsv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/348504/original/file-20200721-92332-t7hrsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/348504/original/file-20200721-92332-t7hrsv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/348504/original/file-20200721-92332-t7hrsv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This map shows the probability of below or above-average tropical cyclones for the 2020/21 Southwest Pacific cyclone season.</span>
<span class="attribution"><span class="source">www.tcoutlook.com/latest-outlook</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>According to the latest <a href="http://www.bom.gov.au/climate/ahead/about/model/access.shtml">long-range sea surface temperature outlook</a>, there is a <a href="http://www.bom.gov.au/climate/model-summary/#tabs=Bureau-model">79% chance that La Niña conditions</a> could develop before the start of the 2020-21 Southwest Pacific cyclone season. La Niña conditions typically mean the risk of <a href="https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.5070">tropical cyclone activity</a> is elevated for island nations in the western part of the region (New Caledonia, Solomon Islands and Vanuatu) and reduced for nations in the east (French Polynesia and the Cook Islands). But there are exceptions, particularly when certain climate influences like the <a href="https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.5406">Indian Ocean Dipole</a> occur with La Niña events.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/indias-cyclone-fani-recovery-offers-the-world-lessons-in-disaster-preparedness-116870">India's cyclone Fani recovery offers the world lessons in disaster preparedness</a>
</strong>
</em>
</p>
<hr>
<h2>Improving existing tropical cyclone guidance</h2>
<p>Current guidance on tropical cyclones in the Southwest Pacific region is produced by the <a href="https://niwa.co.nz/climate/southwest-pacific-tropical-cyclone-outlook">National Institute of Water and Atmospheric Research</a>, the <a href="http://www.bom.gov.au/climate/cyclones/south-pacific/#tabs=Further-information">Australian Bureau of Meteorology</a> and the <a href="https://www.met.gov.fj/index.php?page=tcseasonpro">Fiji Meteorological Service</a>. Each of these organisations uses a different method and considers different indices to capture ocean-atmosphere variability associated with the El Niño-Southern Oscillation. </p>
<p>Our research adds to the existing methods used by those agencies, but also considers other climate drivers known to influence tropical cyclone activity. In total, 12 separate outlooks are produced for individual nations and territories including Fiji, Solomon Islands, New Caledonia, Vanuatu, Papua New Guinea and Tonga. </p>
<p>Other locations are grouped into sub-regional models, and we also provide outlooks for New Zealand because of the important <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.3753">impacts there from ex-tropical cyclones</a>.</p>
<p>Our long-range outlook is a statistical model, trained on historical relationships between ocean-atmosphere processes and the number of tropical cyclones per season. For each target location, hundreds of unique model combinations are tested. The one that performs best in capturing historical tropical cyclone counts is selected to make the prediction for the coming season. </p>
<p>At the start of each monthly outlook, the model retrains itself, taking the most recent changes in ocean temperature and atmospheric variability and attributes of tropical cyclones from the previous season into account. </p>
<p>Both deterministic (tropical cyclone numbers) and probabilistic (the chance of below, normal or above average tropical cyclone activity) outlooks are updated every month between July and January and are <a href="https://tcoutlook.com/">freely available</a>.</p><img src="https://counter.theconversation.com/content/142657/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Anthony Kiem receives funding from the the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Andrew Lorrey and Andrew Magee 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>
Tropical cyclones account for almost four in five natural disasters across Pacific Island nations. But a new forecasting tool now gives up to four months warning for the upcoming cyclone season.
Andrew Magee, Postdoctoral Researcher, University of Newcastle
Andrew Lorrey, Principal Scientist & Programme Leader of Climate Observations and Processes, National Institute of Water and Atmospheric Research
Anthony Kiem, Associate Professor – Hydroclimatology, University of Newcastle
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/139903
2020-06-05T12:14:27Z
2020-06-05T12:14:27Z
Bangladesh has saved thousands of lives from a devastating cyclone – here’s how
<figure><img src="https://images.theconversation.com/files/339590/original/file-20200603-130907-15debo0.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Charipara village is flooded by the sea as Cyclone Amphan destroyed embankments in Kalapara Upazila in Patuakhali District, Bangladesh. Date: 3 June 2020.</span> <span class="attribution"><span class="source">Md. Johirul Islam</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The Atlantic and Caribbean hurricane season has just begun, with the world worried about the prospect of providing humanitarian relief <a href="http://nautil.us/blog/a-warning-from-history-about-simultaneous-disasters">in the context of a pandemic and lockdowns</a>. But Bangladesh recently experienced one of the most powerful Bay of Bengal cyclones <a href="https://www.emerald.com/insight/content/doi/10.1108/OXAN-ES252695/full/html">on record</a> and saved thousands of lives through <a href="https://theconversation.com/advanced-cyclone-forecasting-is-leading-to-early-action-and-its-saving-thousands-of-lives-139699">forecasting, warning, and evacuation</a>.</p>
<p><a href="https://www.who.int/bulletin/volumes/90/2/11-088302/en/">This is in stark contrast</a> to the November 1970 cyclone, which killed around 500,000 people in Bangladesh (then East Pakistan), making it one of the deadliest known storms in human history. Around <a href="https://doi.org/10.1017/S1049023X00030351">11,000 died</a> in a 1985 cyclone, and one in 1991 <a href="https://doi.org/10.1017/S1049023X00030351">killed 140,000</a>. More recent strikes, such as <a href="https://reliefweb.int/report/bangladesh/cyclone-sidr-bangladesh-damage-loss-and-needs-assessment-disaster-recovery-and">Cyclone Sidr in 2007</a> and <a href="https://reliefweb.int/sites/reliefweb.int/files/resources/EFECBC75EEE6F6DEC12575CF00284D1C-map.pdf">Cyclone Alia in 2009</a>, had over 3,400 deaths and about 190 deaths respectively.</p>
<p>All these far exceeded the recent Cyclone Amphan’s total of <a href="https://www.humanitarianresponse.info/sites/www.humanitarianresponse.info/files/documents/files/cyclone_amphan_joint_needs_assessment_final_draft_31_may.pdf">26 deaths</a> so far. Understanding the generally declining death toll offers lessons on how the rest of the world could prepare better for such events. Part of it is <a href="https://theconversation.com/advanced-cyclone-forecasting-is-leading-to-early-action-and-its-saving-thousands-of-lives-139699">forecasting, warning, and evacuation</a>.</p>
<p>But another part is local action, which <a href="https://www.ucl.ac.uk/risk-disaster-reduction/people/bayes-ahmed">we research</a>. Much of this science is <a href="http://ijmed.org/articles/770/">participatory</a>, directed by the people who are <a href="https://doi.org/10.1108/DPM-12-2017-0318">vulnerable</a> in order to balance and meld local and external ideas and approaches.</p>
<h2>From vulnerability to resilience</h2>
<p>Cyclone Amphan made landfall in Bangladesh on May 20 2020. It <a href="https://www.icimod.org/article/mapping-floods-in-bangladesh-caused-by-cyclone-amphan-to-support-humanitarian-response/">inundated over 4,000 sq km of land</a> and destroyed homes, polders (low-lying areas of land surrounded by dikes or levees), embankments, roads, electricity poles, mobile phone towers, bridges and culverts, with the exact costs still being tallied. Many agricultural fields and fish farms were overwhelmed by the saltwater storm surge. </p>
<p>The low death toll can be largely attributed to Bangladesh’s long-term efforts to reduce vulnerabilities, including at the local level, which is always <a href="https://doi.org/10.1016/j.pdisas.2019.100008">the key in preventing disasters</a>. In 1970, the country had only 42 cyclone shelters, whereas now <a href="http://www.warpo.gov.bd/">over 12,000</a> functionally active cyclone shelters dot the coastline, serving nearly 5 million people. </p>
<p>A diverse system of warning messages tailored to local needs keeps people informed about evacuation, ranging from social media to people on bicycles with megaphones. Training in school means that the announcements are trusted and the population knows how to react and why.</p>
<p>Bangladesh has invested in constructing numerous <a href="https://doi.org/10.1080/02508060.2015.1025196">polders</a> to reduce the force of storm surges, although water retention has sometimes damaged <a href="https://doi.org/10.2166/wp.2013.172">agriculture and infrastructure</a>. Local leaders, organisations, and authorities collaborate to implement tidal river management and nature-based approaches such as <a href="https://doi.org/10.1371/journal.pone.0214079">mangroves</a>. This helps to deal with storm surge and rainfall, as well as reduced freshwater due to <a href="https://doi.org/10.1111/1752-1688.12775">India’s Farakka Barrage</a>, built across the Ganges River to keep the water in India since the 1970s.</p>
<p><a href="https://www.mdpi.com/2071-1050/8/8/805/htm">We assessed one local programme</a> funded and supported by the British and Swedish Red Cross for implementation by the Bangladesh Red Crescent. This “Vulnerability to Resilience” programme ran between 2013 and 2016 in the coastal villages of Pashurbunia and Nowapara in Kalapara Upazila in Patuakhali district.</p>
<p>This was the first time that people there had been involved in such resilience-building work. They installed flood-resistant tubewells, raised latrines above expected flood levels, trained for improved hygiene and first aid, distributed safety equipment, improved local early warning and evacuation systems, and were trained as local volunteers to continue these activities.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/340098/original/file-20200605-176542-1kgtzfx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/340098/original/file-20200605-176542-1kgtzfx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=407&fit=crop&dpr=1 600w, https://images.theconversation.com/files/340098/original/file-20200605-176542-1kgtzfx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=407&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/340098/original/file-20200605-176542-1kgtzfx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=407&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/340098/original/file-20200605-176542-1kgtzfx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=511&fit=crop&dpr=1 754w, https://images.theconversation.com/files/340098/original/file-20200605-176542-1kgtzfx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=511&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/340098/original/file-20200605-176542-1kgtzfx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=511&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Cyclone Amphan affected areas in Shyamnagar Upazila, Satkhira District, Bangladesh.</span>
<span class="attribution"><span class="source">© Taifur Rahman, HMBD Foundation, Bangladesh</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Diverse and alternative livelihood opportunities were also promoted. Household-level businesses and shops were encouraged, alongside local markets for the products. </p>
<p>This included people growing and selling garden vegetables and rice, producing crafts through quilting and sewing, rearing cattle for milk and beef, and investing in ducks, chickens, and aquaculture for fish. If any one of these livelihoods is interrupted or ruined, then people would still have options for earning income.</p>
<p>These initiatives are clearly not about cyclones only and move far beyond forecasting, warning, and evacuation. They improve livelihoods, living conditions, community interaction, health, and safety irrespective of a storm. <a href="https://www.mdpi.com/2071-1050/8/8/805/htm">Our calculations</a> immediately after the programme demonstrated that every dollar invested in the programme produced a quick payback of almost five times that amount through enhanced income and local activities.</p>
<h2>Local success</h2>
<p>The real test, though, remains what happens during a hazard. Three weeks after the programme ended, Cyclone Roanu ripped through the south coast of Bangladesh on May 21, 2016. Pashurbunia and Nowapara reported successful warning and evacuation, no casualties, livelihoods with limited interruption, and a water supply and latrines that functioned afterwards.</p>
<p>Similar success is now repeated with Amphan. Despite the cyclone’s devastation, the people are alive and are returning home to rebuild. In Pashurbunia and Nowapara, seven kilometres of polder length were destroyed while the villages and agricultural lands were inundated. </p>
<p>The local population is repairing the damaged polders, houses, and latrines while restoring the drinking water supply and resuming their livelihoods. This is mainly through self-help, without much external assistance so far. It is not easy, but much better than before.</p>
<p>It required nearly 50 years from the 1970 calamity to achieve this state of disaster risk reduction and readiness. Plenty of work remains since Bangladesh faces many other hazards, including <a href="https://www.routledge.com/Climate-Change-Impacts-and-Womens-Livelihood-Vulnerability-in-Developing/Momtaz-Asaduzzaman/p/book/9781138616103">human-caused climate change</a>, sea-level rise, <a href="https://doi.org/10.1016/j.pdisas.2019.100019">earthquakes</a>, and <a href="https://doi.org/10.1007/s10346-014-0521-x">landslides</a>. The country is also coping with one of the largest current refugee crises following <a href="https://www.icj-cij.org/en/case/178">genocide against the Rohingya</a>.</p>
<p>Any cyclone could change the fatality trend. But Bangladesh’s efforts to date, from the national to the local level, show what any location experiencing tropical cyclones could and should do.</p><img src="https://counter.theconversation.com/content/139903/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ilan Kelman receives funding from research councils in the UK and Norway, as well as the Wellcome Trust and internal UCL funding. He is also Professor II at the University of Agder in Norway and co-directs the non-profit organisation Risk RED (Risk Reduction Education for Disasters). The British Red Cross based in London funded the original work in Pashurbunia and Nowapara.</span></em></p><p class="fine-print"><em><span>Bayes Ahmed receives funding from the Royal Society and the British Academy. </span></em></p>
Cyclone Amphan was one of the worst cyclones to hit Bangladesh in modern times. But thanks to local action, many lives were saved.
Ilan Kelman, Professor of Disasters and Health, UCL
Bayes Ahmed, Lecturer in Risk and Disaster Science, UCL
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/139699
2020-06-01T15:34:31Z
2020-06-01T15:34:31Z
Advanced cyclone forecasting is leading to early action – and it’s saving thousands of lives
<p>On May 18, a massive tropical cyclone with sustained winds of nearly 150 miles per hour was barrelling across the Bay of Bengal towards the low-lying coasts of East India and Bangladesh. This supercyclonic storm Amphan (from the Thai word meaning “sky” and pronounced “um-pun”) was the biggest in the Bay of Bengal since the 1999 Odisha cyclone, which <a href="https://qz.com/india/279192/how-india-went-from-15000-cyclone-deaths-in-1999-to-just-38-last-year/">killed 15,000 people</a>. </p>
<p>A few days earlier, when it was just a plain old storm, Amphan had <a href="http://www.ft.lk/news/Rains-wreak-havoc-claim-two-lives/56-700487">swept through Sri Lanka</a>, killing several people in heavy rain, floods and winds. It would go on to cause scores of deaths, make thousands homeless, and cause billions of dollars’ worth of damage. Yet it could have been much worse were it not for the latest computer forecasting and the right interventions by the relevant governments and international agencies. </p>
<p>Although the storm weakened slightly before it hit the coastline of West Bengal, it still overcame much of the network of embankments designed to prevent flooding. Coastal defences were rendered completely incapable of holding back the sea, with reports that sea levels were lifted by 2 metres or more on high tides and a <a href="https://www.reuters.com/article/us-asia-storm-india/cyclone-kills-14-in-india-bangladesh-leaving-trail-of-destruction-idUSKBN22W0MT">massive storm surge</a>. It caused flooding through coastal settlements and several miles inland, washing away bridges and roads.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/338569/original/file-20200529-96695-ak8age.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/338569/original/file-20200529-96695-ak8age.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/338569/original/file-20200529-96695-ak8age.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/338569/original/file-20200529-96695-ak8age.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/338569/original/file-20200529-96695-ak8age.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/338569/original/file-20200529-96695-ak8age.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/338569/original/file-20200529-96695-ak8age.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/338569/original/file-20200529-96695-ak8age.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">Strong winds destroyed this bus in Kolkata.</span>
<span class="attribution"><span class="source">Roop_Dey / shutterstock</span></span>
</figcaption>
</figure>
<p>Anyone who has ever been caught in such a storm will testify to this overwhelming force of nature. Winds travelling at 100mph will pick up huge objects and fling them around like toys. If you’re hit, you stand as much chance as if you were struck by a speeding train. During Amphan, buildings toppled in Kolkata, horrifically crushing people inside. Others were electrocuted, as shredded power cables <a href="https://timesofindia.indiatimes.com/city/kolkata/electrocuted-bodies-float-up-in-waterlogged-streets/articleshow/75878701.cms">turn wet surfaces into electric chairs</a>. Even a week later in the city, water and electricity supplies were not restored, raising risks of disease at a time when pandemics are already on everyone’s minds.</p>
<p>This part of the world is used to heavy rain, but hit with monsoon-like rainfall in the wrong season, farmers in Bangladesh were caught unaware as floods caused by the sheer weight of rainfall rushed through their fields. The water gouged away productive soil and ruined crops. By way of comparison, had that amount of rain had fallen over the Thames basin, parts of Oxford, Reading and London would have been underwater within hours.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/338555/original/file-20200529-96723-wl5101.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/338555/original/file-20200529-96723-wl5101.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/338555/original/file-20200529-96723-wl5101.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/338555/original/file-20200529-96723-wl5101.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/338555/original/file-20200529-96723-wl5101.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/338555/original/file-20200529-96723-wl5101.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=466&fit=crop&dpr=1 754w, https://images.theconversation.com/files/338555/original/file-20200529-96723-wl5101.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=466&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/338555/original/file-20200529-96723-wl5101.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=466&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Amphan weakened from a category 5 cyclone (red) to a ‘mere’ cat 2 (pale yellow) as it reached the coast.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Amphan_2020_track.png">Meow / data: NASA / NOAA</a></span>
</figcaption>
</figure>
<p>This was a natural disaster by any measure. Yet many people escaped the worst effects of Amphan because of some heroically accurate weather and flood forecasting. </p>
<p>On 12 May, before the low pressure conditions that were the germ of the cyclone had even formed, and a full eight days before landfall, <a href="https://confluence.ecmwf.int/display/TIGGE">global multi-model weather forecasts</a>, run on supercomputers at weather centres across the world showed with good accuracy that <a href="https://twitter.com/webberweather/status/1260027539545718786">something major was about to happen</a>. Conditions were right for a cyclone to form, pick up energy from the warm ocean, and track towards India and Bangladesh. Three days before landfall, the forecasts had become so clear that the Indian and Bangladeshi state meteorological departments were able to issue clear warnings. Amphan was the first cyclone of the North Indian storm season, and was a good test of how ready we are.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1262685131967361024"}"></div></p>
<p>A good forecast is only the starting point, however. A well-conducted action plan is the key to saving lives. This is where the anticipatory response by national governments and humanitarian agencies has been particularly impressive. After the warning from the Indian and Bangladeshi meteorologists, <a href="https://www.hindustantimes.com/india-news/as-cyclone-amphan-nears-4-2mn-evacuated-in-coastal-regions-of-india-b-desh/story-bpZ14tH5LNaaDNckvZknDK.html">more than 4 million people</a> were evacuated from coastal areas, even as authorities also coped with the pressure of COVID-19. Evacuation centres had reduced capacity and many temporary shelters had to be put in place at short notice; yet the job was done.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1263375237279711232"}"></div></p>
<p>There is still lots of work to be done in order to understand what will happen with tropical cyclones as the climate changes. Their formation is based on a complex series of things, including ocean temperatures and currents, and the strength and direction of winds. These are fiendishly complex physical processes, and are all influenced in different ways as the planet heats up. How all these different elements interact determines how strong the winds get, how high the storm surge is, how much rainfall they pick up, where they go, how quickly or slowly they move over land, and where and how fast rain falls out, creating intense deluges.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1263375230078119936"}"></div></p>
<p>This is complex science. Other climate change impacts are easier to predict – for example, we know that in a warmer world, we are more likely to see <a href="https://theconversation.com/global-warming-now-pushing-heat-into-territory-humans-cannot-tolerate-138343">dangerous heatwaves</a>. Some studies have suggested that a warmer world will mean we see fewer tropical cyclones in total, but <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/wcc.371">bigger and more damaging events when they do occur</a>, as a warmer ocean and atmosphere can carry more energy for destructive storms to form.</p>
<p>Of course, climate change impacts more than just one type of weather. In this part of Asia, extreme heatwaves are perhaps a less violent, but more deadly phenomenon – and summer is on its way. The <a href="https://t.co/FKsIEHc0fZ?amp=1">joint threats of COVID-19 and heatwaves</a> are going to be particularly tricky. Add to that the coming monsoon season, threats of droughts and other extreme weather, and it’s clear that the earlier people can be warned and take action to protect themselves, the better.</p><img src="https://counter.theconversation.com/content/139699/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hannah Cloke advises the Environment Agency and the European Centre for Medium-range Weather Forecasts on flood risk, flood forecasting and early warning. She works with local flood groups and advises local and national government and humanitarian agencies on flood emergencies. Her flood research is funded by the Natural Environment Research Council and the European Commission's Horizon 2020 programme.</span></em></p>
Massive cyclone that hit India and Bangladesh could have been so much worse.
Hannah Cloke, Professor of Hydrology, University of Reading
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/126515
2019-12-03T18:35:29Z
2019-12-03T18:35:29Z
Homes can be better prepared for cyclones. But first we must convince the owners
<p>Most Australians know cyclones can cause serious damage to housing. Insurance premiums in cyclone-prone regions are <a href="https://www.accc.gov.au/system/files/Northern%20Australia%20Insurance%20Inquiry%20-%20First%20interim%20report%202018.PDF">among the highest in the country</a>. Unfortunately, things are likely to get worse before they get better.</p>
<p>Some predict as many as <a href="https://www.abc.net.au/news/2019-03-13/climate-data-reveals-australias-worst-affected-regions/10892710">10% of houses in Australia may become “uninsurable” by 2100</a>. However, the good news is home owners can do many things to reduce cyclone risk. Even better, this will <a href="https://ajem.infoservices.com.au/items/AJEM-31-04-12">help reduce their insurance premiums</a>.</p>
<p>The start of <a href="http://www.bom.gov.au/climate/cyclones/australia/">cyclone season</a> should remind many Australians to start preparing. Home owners are usually told to trim their trees and prepare their <a href="https://www.qld.gov.au/emergency/dealing-disasters/prepare-for-disasters/emergency-kit">emergency kits</a>. While these activities can help keep people safe during and after a cyclone, it’s just as important to improve resilience for the long term. Consider adding cyclone shutters, upgrading older roofs, etc.</p>
<p>Unfortunately, it often takes a disaster to motivate change. Following Cyclone Tracy, which devastated Darwin in 1974, Australia developed a much stronger building code. As a result, all houses built in cyclone-prone regions after 1982 have cyclone-ready roofs. This has <a href="https://www.jcu.edu.au/__data/assets/pdf_file/0009/321993/Technical-Report-57-Tropical-Cyclone-Yasi-Structural-damage-to-buildings.pdf">reduced damage</a> to these newer houses in cyclones.</p>
<p>But many houses still do not have cyclone-ready roofs – <a href="https://researchonline.jcu.edu.au/45863/1/JCU%201%20-%20FINAL%20for%20publication%20150715.pdf">up to 60% in Queensland</a>. In addition, <a href="https://www.jcu.edu.au/__data/assets/pdf_file/0009/321993/Technical-Report-57-Tropical-Cyclone-Yasi-Structural-damage-to-buildings.pdf">post-cyclone damage surveys have shown</a> all houses – not just older ones – are vulnerable to broken windows and damage when water gets inside (e.g. wind-driven rain).</p>
<p>Thankfully, a range of other structural upgrades can reduce this damage. For example, cyclone shutters protect windows from being smashed by flying debris. However, the <a href="https://www.suncorpgroup.com.au/uploads/JCU-Cyclone-Mitigation-Survey-Report-final.pdf">uptake of voluntary structural upgrades like cyclone shutters has been low</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/303385/original/file-20191125-74584-c0h6db.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/303385/original/file-20191125-74584-c0h6db.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/303385/original/file-20191125-74584-c0h6db.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=374&fit=crop&dpr=1 600w, https://images.theconversation.com/files/303385/original/file-20191125-74584-c0h6db.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=374&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/303385/original/file-20191125-74584-c0h6db.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=374&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/303385/original/file-20191125-74584-c0h6db.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=470&fit=crop&dpr=1 754w, https://images.theconversation.com/files/303385/original/file-20191125-74584-c0h6db.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=470&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/303385/original/file-20191125-74584-c0h6db.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=470&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cyclone shutters would have protected this window from being smashed by flying debris when Tropical Cyclone Marcia hit Yeppoon.</span>
<span class="attribution"><a class="source" href="https://www.researchgate.net/publication/299487064_Modelling_cyclone_loss_mitigation_using_claims_analysis">Image courtesy of Smith, Henderson & Terza (2015)</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our research recently examined how Queensland home owners think about these measures and how to get more people to implement them. The main findings (see full reports <a href="https://www.suncorpgroup.com.au/uploads/JCU-Cyclone-Mitigation-Survey-Report-final.pdf">part 1</a> and <a href="https://www.suncorpgroup.com.au/uploads/JCU-North-Queenslanders-Perceptions-of-Cyclone-Risk.pdf">part 2</a>) suggest a need to improve both messaging and policy.</p>
<h2>How can we improve messaging?</h2>
<p><strong>1. Think and talk about cyclones more often</strong></p>
<p>One way to encourage preparedness is to get people to think and talk about cyclones more often – not just once a year when the cyclone season starts.</p>
<p>Installing structural upgrades takes time. It is too late to upgrade a roof when a cyclone is approaching.</p>
<p><strong>2. Provide location-specific wind-speed information</strong></p>
<p>Cyclone wind speeds differ greatly depending on distance from the eye of the storm. So while the same cyclone may affect people living in different towns, not everyone will experience the same wind speed.</p>
<p>For example, while people in Townsville experienced Cyclone Yasi (a category 5 cyclone), the wind speed in Townsville was equivalent to a category 2 cyclone. But this information was not easily accessible. This may explain why 74% of the people we surveyed recalled that wind speeds from Cyclone Yasi were at least one category higher than what they experienced in their location.</p>
<p>We should, instead, provide people with location-specific information about cyclones. This will allow people to make more informed decisions about their own level of risk.</p>
<p><strong>3. Show structural upgrades are effective</strong></p>
<p>Acknowledging cyclones as a threat is one thing, but home owners need to be convinced that structural upgrades are useful. Without experiencing a broken window, for example, it is difficult to imagine why cyclone shutters would be useful.</p>
<p>We need to show people structural upgrades reduce damage and keep them safe. A video, like the one below, is one way of showing this.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/YuipPwAsCpc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A demonstration of the force of a cyclone’s winds.</span></figcaption>
</figure>
<h2>What can better policy achieve?</h2>
<p>Improved messaging is only one side of the story. Although measures to reduce cyclone damage are <a href="https://www.suncorp.com.au/content/dam/suncorp/insurance/suncorp-insurance/documents/home-and-contents/protect-the-north/suncorp-attachment-4-urbis-cyclone-mitigation-report.pdf">cost effective overall</a>, many home owners see structural upgrades as too expensive. For example, a <a href="https://www.suncorpgroup.com.au/uploads/JCU-Cyclone-Testing-Station-Phase-2-Report.pdf">full roof upgrade can cost around A$30,000</a>.</p>
<p>Our research found owners are more likely to install structural upgrades if they consider it a worthwhile investment. Subsidising the price of these upgrades is one way to help with the upfront costs.</p>
<p>The Queensland government’s recent <a href="https://www.qld.gov.au/housing/buying-owning-home/financial-help-concessions/household-resilience-program">Household Resilience Program</a> was one example of a policy that promoted structural upgrades. Under this program, lower-income homeowners could receive grants of up to A$11,250. It was so popular that it created market competition among builders, which lowered the price of roof upgrades.</p>
<p>Many Queensland insurance companies also offer reduced premiums for structural upgrades. But home owners must still pay the upfront costs. Regardless of the incentive program, insurance companies need to make it clear to customers that they value structural mitigation.</p>
<p>Like most campaigns to change behaviour, promoting structural upgrades will require both policy and messaging changes. If we want to reduce damage in the North, we need to think about cyclones as a long-term threat and remember that preparation starts before the cyclone season begins.</p><img src="https://counter.theconversation.com/content/126515/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Smith receives funding from the Queensland government and Suncorp for the research discussed in this article. </span></em></p><p class="fine-print"><em><span>Mitchell Scovell 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>
Most homes are not as cyclone-ready as they could be. It seems lower insurance premiums aren’t enough of an incentive for owners to upgrade their homes, but a new study points to some solutions.
Mitchell Scovell, PhD candidate, James Cook University
Daniel Smith, Research Fellow, James Cook University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/125139
2019-10-14T00:10:15Z
2019-10-14T00:10:15Z
Australia could see fewer cyclones, but more heat and fire risk in coming months
<p>Northern Australia is likely to see fewer cyclones than usual this season, but hot, dry weather will increase the risk of fire and heatwaves across eastern and southern Australia.</p>
<p>The Bureau of Meteorology today released its forecast for the <a href="http://www.bom.gov.au/climate/cyclones/australia/">tropical cyclone season</a>, which officially runs from November 1 to April 30.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/its-only-october-so-whats-with-all-these-bushfires-new-research-explains-it-124091">It's only October, so what's with all these bushfires? New research explains it</a>
</strong>
</em>
</p>
<hr>
<p>Also published today is the October to April <a href="http://www.bom.gov.au/climate/cyclones/australia/">Severe Weather Outlook</a>, which examines the risk of other weather extremes like flooding, heatwaves and bushfires. </p>
<h2>Warmer oceans means more cyclones</h2>
<p>On average, 11 tropical cyclones form each season in the Australian region. Around four of those cross the coast. The total number each season is roughly related to how much cooler or warmer than average the tropical oceans near Australia are during the cyclone season.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/296793/original/file-20191013-135525-1gmzgl8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296793/original/file-20191013-135525-1gmzgl8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=191&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296793/original/file-20191013-135525-1gmzgl8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=191&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296793/original/file-20191013-135525-1gmzgl8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=191&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296793/original/file-20191013-135525-1gmzgl8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=240&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296793/original/file-20191013-135525-1gmzgl8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=240&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296793/original/file-20191013-135525-1gmzgl8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=240&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Map showing the average number of tropical cyclones through the Australian region and surrounding waters in ENSO-neutral years, using all years of data from the 1969-70 to 2017-18 tropical cyclone season.</span>
</figcaption>
</figure>
<p>One of the biggest drivers of change in ocean temperatures is the El Niño–Southern Oscillation, or ENSO. During La Niña phases of ENSO, the warmest waters in the equatorial Pacific build up in the western Pacific and to the north of Australia. That region then becomes the focus for more cloud, rainfall and tropical cyclones.</p>
<p>But during El Niño, the warmest water shifts towards the central Pacific and away from northern Australia. This decreases the likelihood of cyclones in our region.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-el-nino-and-la-nina-27719">Explainer: El Niño and La Niña</a>
</strong>
</em>
</p>
<hr>
<p>And when ENSO is neutral, there is little push towards above or below average numbers of cyclones.</p>
<p>Temperatures in the tropical Pacific Ocean have been ENSO-neutral since April and are likely to stay <a href="http://www.bom.gov.au/climate/model-summary/archive/20190912.archive.shtml">neutral until at least February 2020</a>. However, some tropical patterns are El Niño-like, including higher-than-average air pressure at Darwin. This may be related to the current <a href="http://www.bom.gov.au/climate/enso/wrap-up/archive/20191001.archive.shtml">record-strong positive Indian Ocean Dipole</a> – another of Australia’s major climate drivers – and the cooler waters surrounding northern Australia.</p>
<p>The neutral ENSO phase alongside higher-than-average air pressure over northern Australia means we expect fewer-than-average tropical cyclones in the Australian region this season. The bureau’s Tropical Cyclone Season Outlook model predicts a 65% chance of fewer-than-average cyclones.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/rW6wEjxmZ_M?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>At least one tropical cyclone has crossed the Australian coast every season since reliable records began in the 1970s, so people across northern Australia need to be prepared every year. In ENSO-neutral cyclone seasons, this first cyclone crossing typically occurs in late December.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/el-nino-has-rapidly-become-stronger-and-stranger-according-to-coral-records-115560">El Niño has rapidly become stronger and stranger, according to coral records</a>
</strong>
</em>
</p>
<hr>
<h2>Other severe weather</h2>
<p>While cyclones are one of the key concerns during the coming months, the summer months also bring the threat of several other forms of severe weather, including bushfires, heatwaves and flooding rain.</p>
<p>With dry soils inland, and hence little moisture available to cool the air, and a forecast for <a href="http://www.bom.gov.au/climate/ahead/outlooks/archive/20191010-outlook.shtml">clear skies and warmer days</a>, there is an increased chance that heat will build up over central Australia during the spring and summer months. This increases the chance of heatwaves across eastern and southern Australia when that hot air is drawn towards the coast by passing weather systems.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/296794/original/file-20191013-135501-2yw917.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/296794/original/file-20191013-135501-2yw917.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296794/original/file-20191013-135501-2yw917.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=437&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296794/original/file-20191013-135501-2yw917.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=437&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296794/original/file-20191013-135501-2yw917.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=437&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296794/original/file-20191013-135501-2yw917.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=550&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296794/original/file-20191013-135501-2yw917.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=550&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296794/original/file-20191013-135501-2yw917.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=550&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Australian seasonal bushfire outlook, as of August 2019. Vast areas of Australia, particularly the east coast, have an above-normal fire potential this season.</span>
<span class="attribution"><span class="source">Bushfire and Natural Hazards CRC/Australasian Fire and Emergency Service Authorities Council</span></span>
</figcaption>
</figure>
<p>Likewise, the dry landscape and the chance of extreme heat also raise the risk of more bushfires throughout similar parts of Australia, especially on windy days. And with fewer natural firebreaks such as full rivers and streams, even greater care is needed in some areas.</p>
<p>Widespread floods are less likely this season. This is because of forecast below-average rainfall and also because dry soils mean the first rains will soak into the ground rather than run across the landscape.</p>
<p>However, as we saw in <a href="http://www.bom.gov.au/climate/current/statements/scs69.pdf">northern Queensland in January and February this year</a>, when up to 2 metres of rainfall fell in less than 10 days, localised flooding can occur in any wet season if a tropical low parks itself in one location for any length of time.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/catastrophic-queensland-floods-killed-600-000-cattle-and-devastated-native-species-120753">Catastrophic Queensland floods killed 600,000 cattle and devastated native species</a>
</strong>
</em>
</p>
<hr>
<p>Most of all, it’s always important to follow advice from emergency services on what to do before, during and after severe weather. <a href="http://www.bom.gov.au/knowyourweather/">Know your weather, know your risk and be prepared</a>. You can stay up to date with the latest forecast and warnings on the bureau’s website and <a href="https://e.bom.gov.au/link/id/zzzz53bb31db150fb433/page.html?prompt=1">subscribe</a> to receive climate information emails.</p><img src="https://counter.theconversation.com/content/125139/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>
Southern and eastern Australia need to prepare for heatwaves and increased fire risk this summer, as forecasts predict hot, dry weather.
Jonathan Pollock, Climatologist, Australian Bureau of Meteorology
Andrew B. Watkins, Head of Long-range Forecasts, Australian Bureau of Meteorology
Catherine Ganter, Senior Climatologist, Australian Bureau of Meteorology
Paul Gregory, BOM, Australian Bureau of Meteorology
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/119657
2019-09-04T10:26:14Z
2019-09-04T10:26:14Z
Why forecasting floods should be a global collaborative effort
<figure><img src="https://images.theconversation.com/files/286742/original/file-20190802-117893-1h4ik38.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Flooded houses in Buzi, Mozambique after tropical cyclone Idai struck.</span> <span class="attribution"><span class="source">INGC (Mozambique) & FATHUM</span></span></figcaption></figure><p>The number of people exposed to the risk of floods is rising. More and expanding human settlements are being built in flood-prone areas, <a href="https://blogs.agu.org/geospace/2014/11/13/satellite-nightlight-images-show-flood-exposure-increasing-worldwide/">especially in Africa, Asia and South America</a>. This is undoubtedly linked to the dramatic increase in death tolls and economic damages from floods <a href="https://blogs.agu.org/geospace/2010/10/15/population-floods-africa/">experienced in Africa over the past decades</a>. </p>
<p>The largest flood events in Africa often cross countries’ borders. They overwhelm national and local authorities’ capacities. This makes early warning and response challenging, as was seen during tropical cyclones Idai and Kenneth in early 2019.</p>
<p><a href="https://theconversation.com/tropical-cyclone-idai-the-storm-that-knew-no-boundaries-113931">Cyclone Idai</a> struck central Mozambique in March 2019. It also caused floods in Zimbabwe and Malawi. Around 1000 people died and hundreds of thousands were left homeless across the three countries. Six weeks later, <a href="https://www.theguardian.com/world/2019/apr/25/cyclone-kenneth-mozambique-hit-by-strongest-storm-ever">Cyclone Kenneth</a> devastated northern Mozambique. It brought extreme winds and flooding to the country, which was still reeling from Cyclone Idai. Dozens more people were killed. There was widespread destruction.</p>
<p>These cyclones, and the devastation they wrought, show how important it is to integrate local information and resources with global scale forecasts and support. </p>
<p>My colleagues and I from the University of Reading saw this first-hand during cyclones Idai and Kenneth. Together with the <a href="https://www.ecmwf.int/">European Centre for Medium-Range Weather Forecasts</a> and the University of Bristol, we provided real-time emergency flood hazard and exposure bulletins to the <a href="https://www.gov.uk/government/organisations/department-for-international-development">UK’s Department for International Development (DFID)</a>. This ministerial department leads the UK’s work to end extreme poverty and tackle global challenges to support people <a href="https://www.gov.uk/guidance/where-we-work">in developing countries across Africa, Asia and the Middle East</a>. A number of other partners were involved, both from the affected countries and the rest of the world.</p>
<p>We harnessed our resources and access to global data, feeding this to local partners. Our regular flood bulletins contained interpretation of flood forecasts and satellite images from the <a href="https://emergency.copernicus.eu/">Copernicus Emergency Management Service</a>. Humanitarian response partners were able to identify where and when flooding would occur and recede. They could also work out when access would improve, as well as where future humanitarian need could emerge. This helped them to better plan their response and to target those most in need. </p>
<p>This shows how crucial it is to pair local capacity with a growing international community of disaster managers, humanitarians and scientists. All countries would benefit from a better integration of these services on a global scale.</p>
<h2>Data, science and advice</h2>
<p>There are already a number of international initiatives that show how this work can be done.</p>
<p>One example is the <a href="https://gfp.jrc.ec.europa.eu/">Global Flood Partnership</a>. This cooperation framework between scientific organisations and flood disaster managers worldwide allows for the development of effective tools for better predicting and managing flood risk. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1123539000197812224"}"></div></p>
<p>Another example is the <a href="https://www.forecast-based-financing.org/">Forecast-based Financing</a> mechanism developed by the Red Cross Red Crescent Movement. This is used to kick-start and fund humanitarian activities before disasters such as floods have even occurred. It is supported by scientific evidence on the accuracy of hydro-meteorological forecasting systems. </p>
<p>One research project supporting Forecast-based Financing is the <a href="http://blogs.reading.ac.uk/fathum">FATHUM project</a> (Forecasts for Anticipatory Humanitarian Action). It’s led by the University of Reading and funded by DFID and the Natural Environment Research Council under the <a href="https://nerc.ukri.org/research/funded/programmes/shear/">Science for Humanitarian Emergencies & Resilience (SHEAR) programme</a>. The project’s international team includes partners in different sub-Saharan countries. </p>
<p>We work together on decision-making from flood forecasting systems to support humanitarian and local preparedness actions. This project includes strengthening forecasting and research capacities in higher education institutions in Uganda, South Africa and Mozambique, for example <a href="http://blogs.reading.ac.uk/fathum/news/">through research placements</a>.</p>
<p>We saw just how valuable such global partnerships can be in the immediate aftermath of cyclones Idai and Kenneth. The governments of Mozambique, Malawi, and Zimbabwe mobilised their available resources for early response in the affected areas. The international community, meanwhile, sent humanitarian aid.</p>
<p>During Idai, my colleagues and I worked with DFID in close collaboration with the <a href="https://www.ecmwf.int/">European Centre for Medium-Range Weather Forecasts</a> and the <a href="http://www.bristol.ac.uk/geography/">University of Bristol</a>. Our briefings included interpreting flood forecasts from the <a href="http://www.globalfloods.eu/">Copernicus Emergency Management Service Global Flood Awareness System (GloFAS)</a> and the <a href="https://www.bristol.ac.uk/news/2019/april/flood-risk.html">University of Bristol’s flood hazard maps</a>. This allowed us to identify where and when flooding may occur. We were also able to pinpoint where and how many people might be affected.</p>
<p>These efforts were bolstered by partners on the ground in Mozambique. They shared local data on the state of river flooding and on the dams’ situation. This contributed to the production and validation of some of the information in our bulletins. </p>
<p>The briefings were shared with international and local humanitarian partners and Mozambique’s disaster management authorities. They were able to use these bulletins alongside local forecasts and warnings. They now had data to identify high-risk areas and decide where to set up emergency shelters, provide food and clean water.</p>
<p>Our work around Idai was highly appreciated by humanitarian response partners on the ground. UN humanitarian actors stated that <a href="https://www.ecmwf.int/en/newsletter/160/news/ecmwf-works-universities-support-response-tropical-cyclone-idai">“the reports produced were tremendously helpful”</a>. So both DFID and the United Nations Office for the Coordination of Humanitarian Affairs asked the team to start producing bulletins ahead of Cyclone Kenneth. Armed with our forecasts and information, those on the ground put together an assessment team and put some emergency measures in place. These included contingency stock, hygiene kits for water treatment, and tarpaulins.</p>
<h2>The importance of transnational cooperation</h2>
<p>It is important to keep building relationships between national forecasting and disaster management services and international organisations and scientists. This will help to improve flood preparedness and early actions. And that is especially important for large-scale floods that cross borders.</p>
<p>Intergovernmental meteorological organisations, such as the European Centre for Medium-Range Weather Forecasts and the World Meteorological Organisation, are a good example of where such wide transnational cooperation has produced better services. </p>
<p>The weather forecasts produced and disseminated by these international centres have been improved significantly, especially in recent years. That’s happened thanks to the integration of local observations and satellite measurements into global forecasting systems. These are shared with national meteorological agencies worldwide. </p>
<p>Such collaboration is urgently needed, alongside other investments such as resilient planning of human settlements outside flood-prone areas. Working together on a global scale will likely save many more lives during future floods.</p><img src="https://counter.theconversation.com/content/119657/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrea Ficchì receives funding from the UK's Natural Environment Research Council and Department for International Development (grant number NE/P000525/1). He is affiliated with the University of Reading (Water@Reading group) and is a visiting scientist at the European Centre for Medium-Range Weather Forecasts (ECMWF).</span></em></p>
Tropical cyclones Idai and Kenneth have shown how important it is to integrate local information and resources with global scale forecasts and support.
Andrea Ficchì, Postdoctoral Researcher in Hydrology, University of Reading
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/121003
2019-07-25T14:31:35Z
2019-07-25T14:31:35Z
Heatwave: think it’s hot in Europe? The human body is already close to thermal limits elsewhere
<figure><img src="https://images.theconversation.com/files/285711/original/file-20190725-136774-1lfr4qj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Average global temperature from 2013 to 2017, as compared to 1951–1980 baseline.</span> <span class="attribution"><a class="source" href="https://climate.nasa.gov/news/2671/long-term-warming-trend-continued-in-2017-nasa-noaa/">NASA’s Scientific Visualization Studio</a></span></figcaption></figure><p>I am a scientist who researches climate hazards. This week I have published research on the potential for a <a href="https://www.nature.com/articles/s41558-019-0525-6">catastrophic cyclone-heatwave combo</a> in the global south. Yet over the past few days I have been approached by various media outlets to talk not about that hazard, but about the unfolding UK heatwave and climate change. It is always satisfying to respond to public interest around weather extremes, but there is a danger that key messages about extreme heat globally are not receiving enough airtime.</p>
<p>It is by now very <a href="https://www.nature.com/articles/nclimate2468">well established</a> that hot extremes are more likely in the changed climate we are living in. Yet there is a seemingly unquenchable thirst for this story to be retold every time the UK sweats. Narratives around such acute, local events detract from critical messages about the global challenges from extreme heat.</p>
<p>Make no mistake, maximum temperatures of 35°C or more are hot by UK standards, but such conditions are familiar to around <a href="https://journals.sagepub.com/doi/abs/10.1177/0309133318776490">80% of the world’s population</a>. The headline-grabbing <a href="https://www.theguardian.com/world/2019/jun/28/france-on-red-alert-as-heatwave-forecast-to-reach-record-45c">46°C recently experienced by Britain’s neighbours in France</a> is indeed unusual, but still falls short of the <a href="https://www.theguardian.com/world/2019/jun/17/india-heatwave-rain-brings-respite-for-some-but-death-toll-rises">50°C recorded in India earlier this summer</a>, and is somewhat temperate relative to the <a href="https://public.wmo.int/en/media/press-release/wmo-verifies-3rd-and-4th-hottest-temperature-recorded-earth">54°C confirmed for both Pakistan (in 2017) and Kuwait (in 2016)</a>. People in these hotter climates are better at coping with high temperatures, yet such heat <a href="https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-16-0145.1">still kills</a>.</p>
<p>Deadly heatwaves are, of course, no stranger to Europeans. The infamous 2003 event claimed as many as <a href="https://www.sciencedirect.com/science/article/pii/S1631069107003770?via%3Dihub">70,000 lives</a>, and 2010 saw more than <a href="https://science.sciencemag.org/content/332/6026/220.full">50,000 fatalities</a> in western Russia. Fortunately, lessons were learned and authorities are now <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/801539/Heatwave_plan_for_England_2019.pdf">much better prepared</a> when heat-health alerts are issued.</p>
<p>But spare a thought for less fortunate communities who are routinely experiencing extraordinary temperatures. In places like <a href="https://advances.sciencemag.org/content/3/8/e1603322.full">South Asia</a> and the <a href="https://www.nature.com/articles/nclimate2833?platform=oscar&draft=journal">Persian Gulf</a>, the human body, despite all its <a href="https://www.ncbi.nlm.nih.gov/pubmed/26184272">remarkable thermal efficiencies</a>, is often operating close to its limits.</p>
<p>And yes, there is a limit.</p>
<p>When the air temperature exceeds 35°C, the body relies on the evaporation of water – mainly through sweating – to keep core temperature at a safe level. This system works until the “wetbulb” temperature reaches 35°C. The wetbulb temperature includes the cooling effect of water evaporating from the thermometer, and so is normally much lower than the normal (“drybulb”) temperature reported in weather forecasts.</p>
<p>Once this wetbulb temperature threshold is crossed, the air is so full of water vapour that sweat no longer evaporates. Without the means to dissipate heat, our core temperature rises, irrespective of how much water we drink, how much shade we seek, or how much rest we take. Without respite, death follows – soonest for the very young, elderly or those with pre-existing medical conditions.</p>
<p>Wetbulb temperatures of 35°C have not yet been widely reported, but there is some evidence that they are <a href="https://journals.sagepub.com/doi/abs/10.1177/0309133318776490">starting to occur</a> in Southwest Asia. Climate change then offers the prospect that some of the most densely populated regions on Earth could pass this threshold by the end of the century, with the <a href="https://www.nature.com/articles/nclimate2833?platform=oscar&draft=journal">Persian Gulf</a>, <a href="https://advances.sciencemag.org/content/3/8/e1603322.full">South Asia</a>, and most recently the <a href="https://www.nature.com/articles/s41467-018-05252-y">North China Plain</a> on the front line. These regions are, together, home to billions of people.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/285714/original/file-20190725-136768-gwsoam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/285714/original/file-20190725-136768-gwsoam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/285714/original/file-20190725-136768-gwsoam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/285714/original/file-20190725-136768-gwsoam.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/285714/original/file-20190725-136768-gwsoam.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/285714/original/file-20190725-136768-gwsoam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/285714/original/file-20190725-136768-gwsoam.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/285714/original/file-20190725-136768-gwsoam.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">Beijing, on the northern edge of the North China Plain, set a new temperature record in 2018.</span>
<span class="attribution"><span class="source">maoyunping / shutterstock</span></span>
</figcaption>
</figure>
<p>As the climate warms in places like the UK, people can take sensible precautions against heat – slowing down, drinking more water, and seeking cool refuges. Air conditioning is one of the last lines of defence but comes with its own problems such as very high energy demands. By 2050, cooling systems are expected to increase electricity demand by an amount equivalent to the present capacity of the <a href="https://www.iea.org/newsroom/news/2018/may/air-conditioning-use-emerges-as-one-of-the-key-drivers-of-global-electricity-dema.html">US, EU, and Japan combined</a>.</p>
<p>Provided that electricity supplies can be maintained, living in chronically heat-stressed climates of the future may be viable. But with such dependence on this life-support system, a sustained power outage could be catastrophic. </p>
<h2>Deadly combination</h2>
<p>So what would happen if we combined massive blackouts with extreme heat? Two colleagues and I recently investigated the possibility of such a “grey swan” event – foreseeable but not yet fully experienced – in a global study of storms and heat, published in the journal <a href="https://www.nature.com/articles/s41558-019-0525-6">Nature Climate Change</a>.</p>
<p>We looked at tropical cyclones, which have already caused the <a href="https://rhg.com/research/puerto-rico-hurricane-maria-worlds-second-largest-blackout/">biggest blackouts on Earth</a>, with the months-long power failure in Puerto Rico after Hurricane Maria among the most serious. We found that as the climate warms it becomes ever more likely that these powerful cyclones would be followed by dangerous heat, and that such compound hazards would be expected every year if global warming reaches 4°C. During the emergency response to a tropical cyclone, keeping people cool would have to be as much a priority as providing clean drinking water.</p>
<p>The UK is moving into new territory when it comes to managing extreme heat. But the places that are already heat stressed will see the <a href="https://www.pnas.org/content/114/15/3861">largest absolute increases in humid-heat</a> with the <a href="https://iopscience.iop.org/article/10.1088/1748-9326/10/8/084013/pdf">smallest safety margin before reaching physical limits</a>, and they are often <a href="https://iopscience.iop.org/article/10.1088/1748-9326/11/5/055007">least-equipped to adapt to the hazard</a>. It is therefore hardly surprising that extreme heat <a href="https://www.nature.com/articles/nclimate2103">drives migration</a>. Such mass displacement makes extreme heat a worldwide issue. Little Britain will feel the consequence of conditions far away from its temperate shores.</p>
<p>The challenges ahead are stark. Adaptation has its limits. We must therefore maintain our global perspective on heat and pursue a global response, slashing greenhouse gas emissions to keep to the Paris warming limits. In this way, we have the greatest chance of averting deadly heat – home and abroad.</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">
<figcaption>
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</figure>
<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=Imagineheader1121003">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/121003/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tom Matthews 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>
Already heat-stressed countries will see the largest absolute increases in humid-heat and have the least ability to adapt.
Tom Matthews, Lecturer in Climate Science, Loughborough University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/118697
2019-06-12T13:44:25Z
2019-06-12T13:44:25Z
Pasha 23: Tropical cyclones are on the rise in southern Africa
<figure><img src="https://images.theconversation.com/files/279103/original/file-20190612-32351-uvmwbe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">shutterstock</span> </figcaption></figure><p>Southern Africa has seen a rise in tropical cyclones recently. The most recent examples were Cyclones Kenneth and Idai that hit Mozambique and surrounds. </p>
<p>In the latest episode of Pasha Dr Jennifer Fitchett, a senior lecturer in physical geography at the University of the Witwatersrand in South Africa, explained why this is happening. </p>
<p>This episode also looked at naming cyclones and how they are measured. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/tropical-cyclone-idai-the-storm-that-knew-no-boundaries-113931">Tropical cyclone Idai: The storm that knew no boundaries</a>
</strong>
</em>
</p>
<hr>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-the-indian-ocean-is-spawning-strong-and-deadly-tropical-cyclones-116559">Why the Indian Ocean is spawning strong and deadly tropical cyclones</a>
</strong>
</em>
</p>
<hr>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/southern-africa-must-brace-itself-for-more-tropical-cyclones-in-future-103641">Southern Africa must brace itself for more tropical cyclones in future</a>
</strong>
</em>
</p>
<hr>
<p><strong>Photo:</strong>
By lavizzara
Cyclone Idai heading towards Mozambique and Zimbabwe in 2019 - Elements of this image furnished by NASA. <a href="https://www.shutterstock.com/image-photo/cyclone-idai-heading-towards-mozambique-zimbabwe-1343576279?src=b9ccTuSSAWN0ZZGM2SNb-A-1-0">Shutterstock</a></p>
<p><strong>Music</strong>
“Happy African Village” by John Bartmann found on <a href="http://freemusicarchive.org/music/John_Bartmann/Public_Domain_Soundtrack_Music_Album_One/happy-african-village">FreeMusicArchive.org</a> licensed under <a href="https://creativecommons.org/publicdomain/zero/1.0/">CC0 1</a>.</p><img src="https://counter.theconversation.com/content/118697/count.gif" alt="The Conversation" width="1" height="1" />
Warmer oceans are contributing to more frequent tropical cyclones.
Ozayr Patel, Digital Editor
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/113246
2019-03-20T23:14:53Z
2019-03-20T23:14:53Z
Hurricanes to deliver a bigger punch to coasts
<figure><img src="https://images.theconversation.com/files/264915/original/file-20190320-93063-1fvolzf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Flood waters cover large tracts of land in Mozambique after cyclone Idai made landfall. Rapidly rising floodwaters have cut off thousands of families from aid organizations. </span> <span class="attribution"><span class="source">(World Food Programme via AP)</span></span></figcaption></figure><p>When tropical cyclone Idai made landfall near Beira, Mozambique on March 14, a spokesperson for the UN World Meteorological Organization called it possibly the <a href="https://www.theguardian.com/world/2019/mar/19/cyclone-idai-worst-weather-disaster-to-hit-southern-hemisphere-mozambique-malawi">the worst weather-related disaster to hit the southern hemisphere</a>. </p>
<p>This <a href="https://public.wmo.int/en/media/news/tropical-cyclone-idai-hits-mozambique">massive and horrifying</a> storm caused catastrophic flooding and widespread destruction of buildings and roads in Mozambique, Zimbabwe and Malawi. Mozambique’s President Filipe Nyusi feared the <a href="https://www.bbc.com/news/world-africa-47609676">death toll might rise to more than 1,000</a> people.</p>
<p>Cyclones, also known as hurricanes or typhoons, are intense wind storms that can take thousands of lives and cause billions of dollars in damage. They generate <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016JC011706">large ocean waves</a> and raise water levels by creating a <a href="https://ascelibrary.org/doi/full/10.1061/%28ASCE%29WW.1943-5460.0000260">storm surge</a>. The combined effects cause coastal erosion, flooding and damage to anything in its path.</p>
<p>Although other storms have hit this African coast in the past, the <a href="https://www.nesdis.noaa.gov/content/tropical-cyclone-idai-mozambique-channel">storm track for cyclone Idai is fairly rare</a>. Warmer-than-usual sea-surface temperatures were directly linked to the <a href="https://link.springer.com/article/10.1007/s00703-006-0251-2">unusually high number of five storms</a> near Madagascar and Mozambique in 2000, including <a href="https://journals.ametsoc.org/doi/10.1175/1520-0434%282004%29019%3C0789%3ATCEAIU%3E2.0.CO%3B2">tropical cyclone Eline</a>. Warmer ocean temperatures could also be behind the intensity of cyclone Idai, as the <a href="https://www.ospo.noaa.gov/Products/ocean/sst/anomaly/index.html">temperature of the Indian Ocean is 2 C to 3 C above</a> the long-term average.</p>
<p><a href="https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/joc.3932">Climate change and ocean warming</a> may be linked to the increasing intensity of storms making landfall and to the development of strong hurricanes reaching places not affected in recent history. These regions may not be prepared with the coastal infrastructure to withstand the extreme forces of these storms. </p>
<h2>The role of climate change</h2>
<p>Scientists are working to improve their forecasts for <a href="https://www.nhc.noaa.gov/">hurricane winds</a> and <a href="https://polar.ncep.noaa.gov/waves/">waves</a>, and research on <a href="https://journals.ametsoc.org/doi/full/10.1175/BAMS-D-13-00242.1">ocean and atmosphere interactions</a> is boosting our understanding of the relationship between climate and the formation of hurricanes. Still, there is considerable uncertainty in predicting trends in extreme weather conditions 100 years into the future. Some computer simulations suggest possible changes in these storms due to climate change.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/264686/original/file-20190319-60959-13dd1nm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/264686/original/file-20190319-60959-13dd1nm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264686/original/file-20190319-60959-13dd1nm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264686/original/file-20190319-60959-13dd1nm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264686/original/file-20190319-60959-13dd1nm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264686/original/file-20190319-60959-13dd1nm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264686/original/file-20190319-60959-13dd1nm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tropical cyclone Idai rapidly strengthened to a category 3 storm in the warm waters between Mozambique and Madagascar.</span>
<span class="attribution"><span class="source">(NOAA)</span></span>
</figcaption>
</figure>
<p>For example, scientists have computed detailed simulations of hurricane-type storms for future climate-warming scenarios and revealed that in some cases the <a href="https://journals.ametsoc.org/doi/full/10.1175/JCLI-D-14-00686.1">hurricane season could be longer</a>. The <a href="https://www.nature.com/articles/ngeo779">intensity of storms could also increase</a> so that there are more major hurricanes (categories 4 and 5 on the <a href="https://www.nhc.noaa.gov/aboutsshws.php">Saffir-Simpson scale</a>) with winds reaching speeds greater than 209 km/h. </p>
<p>Since these storms are fuelled by ocean heat, warmer ocean conditions will influence their intensity and longevity. This may enable them to travel farther over ocean water at higher latitudes, and farther across the continent after they make landfall. </p>
<p>With global sea level rise expected to continue to accelerate through the 21st century, the impacts of <a href="https://www.nature.com/articles/nature12855">coastal flooding from tropical cyclones</a> is also expected to worsen.</p>
<h2>Atlantic hurricanes</h2>
<p>On the Atlantic coast of North America, the hurricane season starts in June and runs to November. We have very recent reminders that these storms can be catastrophic. <a href="https://ieeexplore.ieee.org/abstract/document/8604824">Hurricane Maria</a>, which struck Puerto Rico in 2017, caused infrastructure <a href="https://coast.noaa.gov/states/fast-facts/hurricane-costs.html">damage of US$90 billion</a> and may have <a href="https://www.nejm.org/doi/full/10.1056/NEJMsa1803972">killed more than 4,600 people</a>. </p>
<p>Urban areas can take weeks or months to recover from the flooding caused by the storm surge, which can be compounded by heavy rainfall. When the category 4 <a href="https://www.nature.com/articles/s41586-018-0676-z">hurricane Harvey</a> hit Houston in 2017, it caused <a href="https://coast.noaa.gov/states/fast-facts/hurricane-costs.html">US$125 billion</a> in damage, mostly due to flooding in the metropolitan area. </p>
<p>Hurricanes that reach places that historically have not been affected have major and long-lasting impacts. An example is hurricane Sandy in 2012, the largest storm on record in the Atlantic Ocean. This storm made a westward turn that is <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/grl.50395">very different from typical</a> tropical hurricane tracks. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/264899/original/file-20190320-93028-19n3dej.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/264899/original/file-20190320-93028-19n3dej.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=392&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264899/original/file-20190320-93028-19n3dej.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=392&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264899/original/file-20190320-93028-19n3dej.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=392&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264899/original/file-20190320-93028-19n3dej.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=493&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264899/original/file-20190320-93028-19n3dej.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=493&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264899/original/file-20190320-93028-19n3dej.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=493&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Homes in Ortley Beach, N.J. destroyed by Superstorm Sandy.</span>
<span class="attribution"><span class="source">(AP Photo/Mike Groll, File)</span></span>
</figcaption>
</figure>
<p>Its waves and storm surge <a href="https://www.sciencedirect.com/science/article/pii/S0378383917302090">pounded the coasts of New Jersey and New York</a>, with a huge impact <a href="https://www.sciencedirect.com/science/article/pii/S0278434318300396">washing over coastal dunes</a>, <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2016GL071991">eroding beaches</a> and causing <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016WR019102">flooding in New York City</a>. </p>
<p>It also had a major economic impact, costing <a href="https://coast.noaa.gov/states/fast-facts/hurricane-costs.html">US$71 billion</a> with long-term effects on the <a href="https://www.sciencedirect.com/science/article/pii/S0169555X17303136">coastal environment</a> and lasting <a href="https://www.cambridge.org/core/journals/disaster-medicine-and-public-health-preparedness/article/longterm-recovery-from-hurricane-sandy-evidence-from-a-survey-in-new-york-city/D8F5511E84DF1C7ACFBC3D649388F81A">socioeconomic</a> impacts in a densely populated area.</p>
<h2>Damage to coasts</h2>
<p>Hurricanes can cause severe erosion and breach islands, creating new pathways for water flow between the ocean and back-barrier estuaries. As these storms impact land, they can also create a <a href="https://www.weather.gov/safety/hurricane">dangerous multi-hazard environment</a> of fast-moving air, water and debris. </p>
<p>Urban coastal areas are under a major threat, since coastal structures may not have been designed for the waves and surges that these storms generate. Hurricane Katrina, the mega-disaster that took more than <a href="https://www.nhc.noaa.gov/dcmi.shtml">1,200 lives</a> and cost <a href="https://coast.noaa.gov/states/fast-facts/hurricane-costs.html">US$161 billion</a> in 2005,
taught engineers the hard way that <a href="https://ascelibrary.org/doi/full/10.1061/%28ASCE%290733-950X%282007%29133%3A6%28463%29">hurricanes can cause unanticipated loads</a> on bridges, buildings and coastal structures.</p>
<p>The amount of damage a hurricane creates depends on the intensity and characteristics of the storm, combined with the physical and social setting of the coastal area that it hits. Cities face a high risk of hurricane-related disasters, since they contain higher populations and more infrastructure. This can lead to widespread and catastrophic impacts, such as the massive storm surge and flooding generated by <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014GL060689">typhoon Haiyan</a>, which lead to <a href="https://journals.ametsoc.org/doi/full/10.1175/BAMS-D-14-00245.1">more than 6,000 deaths</a> in the Philippines in 2013. </p>
<h2>Future Impacts</h2>
<p>Regardless of changes to the climatic conditions that cause hurricanes to form and intensify, the fact is that these storms already occur frequently. Each year, <a href="http://science.sciencemag.org/content/309/5742/1844/tab-pdf">80 to 100 tropical storms occur globally. Of these, 40 to 50 are hurricanes, with 10 to 15 classified as major hurricanes</a>. </p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/264902/original/file-20190320-93060-1kgsws5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/264902/original/file-20190320-93060-1kgsws5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=780&fit=crop&dpr=1 600w, https://images.theconversation.com/files/264902/original/file-20190320-93060-1kgsws5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=780&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/264902/original/file-20190320-93060-1kgsws5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=780&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/264902/original/file-20190320-93060-1kgsws5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=980&fit=crop&dpr=1 754w, https://images.theconversation.com/files/264902/original/file-20190320-93060-1kgsws5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=980&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/264902/original/file-20190320-93060-1kgsws5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=980&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Hurricane Isabel made landfall on North Carolina’s Outer Banks on Sept. 18, 2003. Its effects were felt as far as western New England and into the eastern Great Lakes.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Climate change projections suggest the <a href="http://science.sciencemag.org/content/327/5964/454">number of intense hurricanes will rise</a>. Ocean warming will enable these storms to travel farther, and we may see greater hurricane impacts on coasts in the future. </p>
<p>This could include more storm strikes to northern coasts in places like Atlantic Canada, where <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2007JC004500">hurricane Juan made landfall</a> in 2003.</p>
<p>We may also see more hurricanes reaching large inland lakes such as the Great Lakes, affecting major cities like Toronto and Chicago. Rare events, such as <a href="https://www.sciencedirect.com/science/article/pii/S0048969718305874">hurricane Ophelia that hit Ireland</a> in 2017, may become more common. </p>
<p>When we build houses, roads and bridges and increase population density in low-lying coastal areas, we walk a fine line if these coastal regions are not prepared for the ferocity of extreme storms in the future.</p><img src="https://counter.theconversation.com/content/113246/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ryan P. Mulligan receives funding from the Natural Sciences and Engineering Research Council of Canada (NSERC).</span></em></p>
Climate change is making hurricanes more destructive, and may have boosted the intensity of cyclone Idai that hit Mozambique, Zambia and Malawi.
Ryan P. Mulligan, Associate Professor in Civil Engineering, Queen's University, Ontario
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/103641
2018-11-27T07:55:56Z
2018-11-27T07:55:56Z
Southern Africa must brace itself for more tropical cyclones in future
<figure><img src="https://images.theconversation.com/files/246813/original/file-20181122-182071-18g6w0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Heavy rains driven by a cyclone in Sana’a, Yemen.</span> <span class="attribution"><span class="source">EPA-EFE/YAHYA ARHAB</span></span></figcaption></figure><p>Most powerful tropical cyclones – the word is used interchangeably with “hurricanes” – originate in the North Atlantic Ocean, where they’re fuelled by the warm Gulf Stream. The South Indian Ocean experiences proportionately fewer tropical cyclones. The southern African coastline benefits from protection from Madagascar, meaning that tropical cyclones are rarer in Mozambique than in the US and the Caribbean. Those that do hit the region tend to be quite low in intensity on the <a href="https://www.nhc.noaa.gov/aboutsshws.php">Saffir Simpson scale</a>.</p>
<p>This scale is used to rank tropical cyclones on the basis of a storm’s wind speed and pressure: low intensity storms rank as a “1” on the scale, while “5” represents the most intense and damaging tropical cyclones. Category 1 storms are smaller in diameter (50-100km) and have a minimum wind speed of 119km/h, while category 5 storms have wind speeds of 252km/h or more and can span up to 500km in diameter. There’s <a href="https://weather.com/storms/hurricane/news/category-6-hurricane-saffir-simpson-wind-scale/">ongoing debate</a> about whether a category “6” should be added to the scale. </p>
<p>As my <a href="https://doi.org/10.17159/sajs.2018/4426">research</a> shows, the trend in the South Indian Ocean is shifting. Category 5 tropical cyclones didn’t exist in this ocean before 1994. They were recorded for the North Atlantic, North Pacific and South Pacific Oceans throughout most of the 20th century. But since 1994, category 5 storms in the South Indian Ocean have become more frequent.</p>
<p>Based on the progressive trend over the past three decades, their frequency is likely to keep increasing.</p>
<p>This is happening because sea surface temperatures are rising. Tropical cyclones require a minimum sea surface temperature of 26°C to form. These temperatures are being recorded more often and over a larger area of the ocean now than in the past. That’s because the air temperatures that heat up the sea surface are rising due to <a href="http://www.ipcc.ch/report/sr15/">greenhouse gas emissions</a>. </p>
<p>Southern African governments must respond proactively to this new threat.</p>
<h2>Digging into data</h2>
<p>I established all this by studying a <a href="https://www.ncdc.noaa.gov/ibtracs/">global historical database</a> of tropical cyclones that’s maintained by the National Oceanographic and Atmospheric Administration.</p>
<p>The research used records from a number of sources. These include ship and harbour records for the 1800s and early 1900s, aeroplane reconnaissance records for the mid-1900s and data derived from satellites from the 1970s onwards. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/247218/original/file-20181126-140534-14jbqu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/247218/original/file-20181126-140534-14jbqu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=785&fit=crop&dpr=1 600w, https://images.theconversation.com/files/247218/original/file-20181126-140534-14jbqu2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=785&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/247218/original/file-20181126-140534-14jbqu2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=785&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/247218/original/file-20181126-140534-14jbqu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=986&fit=crop&dpr=1 754w, https://images.theconversation.com/files/247218/original/file-20181126-140534-14jbqu2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=986&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/247218/original/file-20181126-140534-14jbqu2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=986&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tropical Cyclone Guillaume, northeast of Mauritius and La Reunion, Indian Ocean.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The first recorded category 5 tropical cyclone in the South Indian Ocean captured in this record is for the year 1994 – 70 years after the first category 5 storm in the North Atlantic Ocean. </p>
<p>I found that in the last 30 years, there’s been a progressive rise in the number of high category tropical storms. For the South Indian Ocean, my study found that sea surface temperatures of 29°C are driving the intensification of storms to category 5 severity. And these very warm ocean temperatures are now being recorded over a much larger area, increasing the probability of these high intensity storms. </p>
<p>These category 5 storms have also shifted pole-wards in their location of origin and landfall over this 30 year period. This means that storms which previously existed in the equatorial waters of the central South Indian Ocean, far from any landmasses, are now increasingly occurring in the southern tropical region. That poses a threat to the northern half of Madagascar, Mozambique and the islands of Reunion and Mauritius. </p>
<h2>A struggling region</h2>
<p>The last time a category 5 storm hit southern Africa was in April 2016, when tropical cyclone Fantala moved through the southwest Indian Ocean passing north of Madagascar and making landfall on the <a href="http://www.seychellesnewsagency.com/articles/5006/Tropical+cyclone+Fantala+hits+Seychelles+island+of+Farquhar%3B+infrastructure+damaged">Island of Farquhar</a> in the Seychelles. </p>
<p>Remarkably, despite being strongest storm ever to have occurred in the South Indian Ocean, a relatively low $4.5 million in damages was <a href="http://www.seychellesnewsagency.com/articles/5175/.+million+in+damages+from+cyclone+that+hit+remote+Seychellois+island%2C+World+Bank+says">recorded</a> and no deaths were <a href="http://documents.worldbank.org/curated/en/802481498125766383/text/116521-WP-Seychelles-Fantala-Final-Publish-Version-PUBLIC.txt">registered</a>. </p>
<p>This is in stark contrast to the last category 5 storm that made landfall on Madagascar – tropical cyclone <a href="https://www.sciencedaily.com/terms/cyclone_gafilo.htm">Gafilo</a>, in March 2004. The storm – which sustained tropical cyclone intensity wind speeds for six days – left at least 250 dead, the sinking of a ferry and left 300,000 people homeless. </p>
<p>Unfortunately, southern Africa struggles to cope with the effects of even category 1 tropical cyclones. This suggests that governments are ill equipped to deal with the more powerful category 5 variety.</p>
<p>But there are things that can be done to proactively deal with this new climatic reality. For instance, coastal buildings, roads and bridges need to be built to withstand the high wind speeds, heavy rainfall and possible storm surges to prevent costly damage to infrastructure. </p>
<p>Better forecasting systems need to be put in place so that cities and towns can effectively evacuate before a storm makes landfall to prevent loss of human life. Spatial planning needs to consider this heightened threat, and where possible, discourage development along high risk coastlines.</p><img src="https://counter.theconversation.com/content/103641/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Fitchett receives funding from the Society of South African Geographers' Centennial Award for Emerging Career Researchers.</span></em></p>
The frequency of intense tropical cyclones is increasing in the South Indian Ocean, a region that previously didn’t have these.
Jennifer Fitchett, Associate Professor of Physical Geography, University of the Witwatersrand
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/104309
2018-10-07T18:53:59Z
2018-10-07T18:53:59Z
Trust Me, I’m An Expert: Cyclone season approacheth, but this year there’s a twist
<p>Australia has just had its driest September on record, and the second driest month ever: the only drier month was April 1902. </p>
<p>The Bureau of Meteorology’s tropical cyclone outlook is out today. It’s predicting a weaker-than-normal tropical cyclone season this year but if one hits – and it’s likely one will – it’ll bring water to rain-starved soil that will soak it up and reduce the flooding risk. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/lessons-not-learned-darwins-paying-the-price-after-cyclone-marcus-93862">Lessons not learned: Darwin's paying the price after Cyclone Marcus</a>
</strong>
</em>
</p>
<hr>
<p>Wes Mountain speaks to forecaster Andrew Watkins, who explains how the forecast works, why a cyclone could help some farms, and how to keep safe this cyclone season. </p>
<p>We’ve never gone through a tropical cyclone season without at least one hitting our coast, but Australia’s past may no longer be a reliable guide to our future. </p>
<p>In her book <a href="https://www.mup.com.au/books/sunburnt-country-paperback-softback">Sunburnt Country: the history and future of climate change in Australia</a>, scientist Joelle Gergis maps Australia’s climate over thousands of years. While we’ve always been a land of extremes, rapid warming since 1950 is starting to alter our weather patterns.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australias-2017-environment-scorecard-like-a-broken-record-high-temperatures-further-stress-our-ecosystems-94114">Australia's 2017 environment scorecard: like a broken record, high temperatures further stress our ecosystems</a>
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</em>
</p>
<hr>
<p>Dr Gergis told Madeleine De Gabriele about creating the most comprehensive history of Australia’s climate ever, and why she still has hope for the future. </p>
<p><br></p>
<hr>
<p><strong>Credits</strong></p>
<p>Free Music Archive: Podington Bear, <a href="https://freemusicarchive.org/music/Podington_Bear/">Clouds, Rain, Sun</a></p>
<p>ABC: <a href="http://www.abc.net.au/news/2018-08-25/morrison-talks-drought-relief-on-first-day-as-pm/10164624">Morrison talks drought relief on first day as PM</a></p>
<p>Free Music Archive: <a href="http://freemusicarchive.org/music/Blue_Dot_Sessions/Cholate/El_Tajo">Blue Dot Sessions - El Tajo</a></p>
<p>Free Music Archive: <a href="http://freemusicarchive.org/music/Blue_Dot_Sessions/Cholate/Arizona_Moon">Blue Dot Sessions - Arizona Moon</a></p><img src="https://counter.theconversation.com/content/104309/count.gif" alt="The Conversation" width="1" height="1" />
Australia must come to terms with some fundamental shifts in our weather patterns. This month, Andrew Watkins from the BOM and climate scientist Joelle Gergis explore what's in store.
Madeleine De Gabriele, Deputy Editor: Energy + Environment
Wes Mountain, Social Media + Visual Storytelling Editor
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/103359
2018-09-17T14:00:39Z
2018-09-17T14:00:39Z
Rogue hurricanes that head northwards may be new normal
<p>Shortly after Hurricane Helene formed off the coast of West Africa on September 7, it did something unusual. Instead of following most hurricanes westward across the Atlantic, Helene turned north towards the UK and Ireland. Now downgraded to an “ex-hurricane”, Storm Helene is nonetheless expected to bring <a href="https://www.metoffice.gov.uk/public/weather/warnings#?date=2018-09-17">strong winds</a> across much of England and Wales when it hits on September 17.</p>
<p>Something similar happened in October 2017 when <a href="https://theconversation.com/why-ex-hurricane-ophelia-took-a-wrong-turn-towards-ireland-and-britain-and-carried-all-that-dust-85851">ex-Hurricane Ophelia</a> turned north and hit the British Isles, causing three deaths and more than 200,000 homes to lose power. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/236656/original/file-20180917-158219-rhnm3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/236656/original/file-20180917-158219-rhnm3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/236656/original/file-20180917-158219-rhnm3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=541&fit=crop&dpr=1 600w, https://images.theconversation.com/files/236656/original/file-20180917-158219-rhnm3j.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=541&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/236656/original/file-20180917-158219-rhnm3j.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=541&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/236656/original/file-20180917-158219-rhnm3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=680&fit=crop&dpr=1 754w, https://images.theconversation.com/files/236656/original/file-20180917-158219-rhnm3j.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=680&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/236656/original/file-20180917-158219-rhnm3j.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=680&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Helene goes rogue.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Helene_2018_track.png">Master0Garfield / NASA / NHC</a></span>
</figcaption>
</figure>
<p>At the time, Ophelia seemed like a very unusual storm due to the direct course it took across the Atlantic. However, two storms of this type in two years naturally raise the question of whether this is the new normal. As the ocean and atmosphere continue to warm, can people in Britain and Ireland expect more rogue, autumnal hurricanes?</p>
<h2>Storm origins</h2>
<p>Broadly speaking, storms generated in the Atlantic fall into two categories. Normally, the storms responsible for poor autumn and winter weather over the British Isles are mid-latitude cyclones. These storms are largely fuelled by the atmospheric instability where cold and warm air masses meet. Many will be familiar with such features in the form of fronts shown in television forecasts. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/236677/original/file-20180917-158219-19odxw2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/236677/original/file-20180917-158219-19odxw2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/236677/original/file-20180917-158219-19odxw2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=515&fit=crop&dpr=1 600w, https://images.theconversation.com/files/236677/original/file-20180917-158219-19odxw2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=515&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/236677/original/file-20180917-158219-19odxw2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=515&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/236677/original/file-20180917-158219-19odxw2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=647&fit=crop&dpr=1 754w, https://images.theconversation.com/files/236677/original/file-20180917-158219-19odxw2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=647&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/236677/original/file-20180917-158219-19odxw2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=647&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 instability associated with fronts provide mid-latitude cyclones with energy.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/imaginary-weather-chart-europe-isobars-197059748?src=kOtWkMh8Xk3XrzwKA_B0TQ-1-1">Frank Fiedler / shutterstock</a></span>
</figcaption>
</figure>
<p>In contrast, tropical cyclones, including hurricanes, derive most of their energy from the warm ocean waters over which they form. The change of state from water vapour to cloud droplets releases latent heat (energy) and produces deep convective clouds (thunderstorms). When conditions are favourable, a strong low pressure feature develops and helps to transport more fuel (in the form of moist air) into the storm.</p>
<p>It is not unusual for tropical cyclones to develop into mid-latitude cyclones (this happens several times a year). In the Atlantic, the transition usually occurs when tropical cyclones have tracked west and gradually curved north into the mid-latitude storm track. However, the direct nature of the route taken by Ophelia and now Helene marks them out as unusual.</p>
<p>So, do Ophelia and now Helene suggest a change in Atlantic storm behaviour? To understand this we need to think about how climate change will impact storms both in tropical and temperate regions.</p>
<h2>Physical mechanisms</h2>
<p>There is now a very clear trend of <a href="http://www.globalchange.gov/browse/indicators/indicator-sea-surface-temperatures">increasing sea surface temperatures</a>, and it might be expected that warmer seas would lead to more frequent or more powerful tropical cyclones. However, <a href="https://www.gfdl.noaa.gov/global-warming-and-hurricanes/">it isn’t yet clear</a> if that is the case for Atlantic hurricanes.</p>
<p>What is likely is that warming seas will enable tropical storms to form further north, potentially meaning more will reach the polar front and transition into mid-latitude cyclones. It is also possible that tropical storms originating further north could be more influenced by the subtropical jet stream and be prematurely steered northeast towards Europe (as in the cases of Ophelia and Helene).</p>
<p>However, it is unclear what effect climate change might have on the location and strength of the polar front and therefore the mid-latitude storm track. This is due to <a href="https://www.nature.com/articles/ngeo2783">the sometimes opposing effects of climate change in models</a>, such as the either poleward or equatorward shift of the Atlantic storm track. This kind of uncertainty makes it hard to estimate future storm behaviour, especially given weather systems are chaotic and linear changes to things like temperature or pressure do not produce linear effects.</p>
<p>What is more certain is that rising sea levels will mean storm surges (abnormally high sea water levels that accompany powerful storms) will have to be less extreme before causing coastal inundation. It is also the case that with temperatures increasing, the atmosphere will be able to <a href="http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch14/clausius.php">hold more water vapour</a>, leading to hurricanes and mid-latitude cyclones that produce heavier rain and make flash flooding more frequent.</p>
<p>Scientists still don’t know exactly how a changing climate will affect the weather. But we do know that the increasing occurrence of rare, extreme weather is detectable and we should expect more of it in the future. As yet, whether or not European hurricanes such as Ophelia and Helene will become more common is unknown. However, it is a further reminder of what an extraordinary year 2018 has been for global weather.</p><img src="https://counter.theconversation.com/content/103359/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexander Roberts receives funding from the Natural Environment Research Council (NERC). </span></em></p>
An ‘ex-hurricane’ will hit the UK and Ireland for the second consecutive year.
Alexander Roberts, Researcher, Institute for Climate and Atmospheric Science (ICAS), University of Leeds
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/102827
2018-09-12T10:35:35Z
2018-09-12T10:35:35Z
How meteorologists predict the next big hurricane
<p>Hurricanes can cause immense damage due to the winds, waves and rain, not to mention the chaos as the general population prepares for severe weather. </p>
<p>The latter is getting more relevant, as the monetary damage from disasters <a href="https://www.ncdc.noaa.gov/billions/time-series">is trending up</a>. The growing coastal <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4367969/">population and infrastructure</a>, as well as <a href="https://nca2014.globalchange.gov/highlights/report-findings/extreme-weather">rising sea level</a>, likely contribute to this increase in costs of damage. </p>
<p>This makes it all the more imperative to get early and accurate forecasts out to the public, something researchers like us are actively contributing to.</p>
<h2>Making predictions</h2>
<p>Hurricane forecasts <a href="https://research.noaa.gov/sites/oar/Documents/NOAA%20Research%20Matters/ResearchHighlights-WeatherTsunamiForecasts.pdf">have traditionally focused</a> on predicting a storm’s track and intensity. The track and size of the storm determine which areas may be hit. To do so, forecasters use models – essentially software programs, often run on large computers.</p>
<p>Unfortunately, no single forecast model is consistently better than other models at making these predictions. Sometimes these forecasts show dramatically different paths, diverging by hundreds of miles. Other times, the models are in close agreement. <a href="https://fivethirtyeight.com/features/forecasts-have-done-a-good-job-predicting-irmas-shifting-path/">In some cases</a>, even when models are in close agreement, the small differences in track have very large differences in storm surge, winds and other factors that impact damage and evacuations. </p>
<p>What’s more, several empirical factors in the forecast models are either determined under laboratory conditions or in isolated field experiments. That means that they may not necessarily fully represent the current weather event.</p>
<p>So, forecasters use a collection of models to determine a likely range of tracks and intensities. Such models include the <a href="https://www.ncdc.noaa.gov/data-access/model-data/model-datasets/global-forcast-system-gfs">NOAA’s Global Forecast System</a> and European Centre for Medium-Range Weather Forecasts global models.</p>
<p>The <a href="https://www.tallahassee.com/story/news/hurricane/2018/06/04/forecasting-model-created-florida-state-critical-tool-national-hurricane-center/661956002/">FSU Superensemble</a> was developed by a group at our university, led by meteorologist T.N. Krishnamurti, in the early 2000s. The Superensemble combines output from a collection of models, giving more weight to the models that showed better predicted past weather events, such as Atlantic tropical cyclone events. </p>
<p>A forecaster’s collection of models can be made larger by tweaking the models and slightly changing the starting conditions. These perturbations attempt to account for uncertainty. Meteorologists cannot know the exact state of the atmosphere and the ocean at the time of the start of the model. For example, tropical cyclones are not observed well enough to have sufficient detail about winds and rain. For another example, the sea surface temperature is cooled by the passage of a storm, and if the area remains cloud-covered these cooler waters are much less likely to be observed by satellite.</p>
<h2>Limited improvement</h2>
<p>Over the past decade, track forecasts have steadily <a href="https://doi.org/10.1175/BAMS-D-12-00071.1">improved</a>. A plethora of observations – from satellites, buoys and aircraft flown into the developing storm – allow scientists to better understand the environment around a storm, and in turn improve their models. Some models have improved by as much as <a href="https://doi.org/10.1175/BAMS-D-12-00071.1">40 percent for some storms</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/235832/original/file-20180911-144455-1bdbyv9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/235832/original/file-20180911-144455-1bdbyv9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/235832/original/file-20180911-144455-1bdbyv9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=706&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235832/original/file-20180911-144455-1bdbyv9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=706&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235832/original/file-20180911-144455-1bdbyv9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=706&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235832/original/file-20180911-144455-1bdbyv9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=888&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235832/original/file-20180911-144455-1bdbyv9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=888&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235832/original/file-20180911-144455-1bdbyv9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=888&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 buoy collecting weather data.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:NOAA-NDBC-discus-buoy.jpg">U.S. National Oceanic and Atmospheric Administration</a></span>
</figcaption>
</figure>
<p>However, forecasts of intensity have <a href="https://www.wunderground.com/cat6/nhc-track-forecasts-best-ever-2017-no-improvement-intensity-forecasts">improved little over the last several decades</a>. </p>
<p>That’s partly because of the metric chosen to describe the intensity of a tropical cyclone. Intensity is often described in terms of peak wind speed at a height of 10 meters above the surface. To measure it, operational forecasters at the National Hurricane Center in Miami look at the maximum, one-minute average wind speed observed at any given point in the tropical cyclone.</p>
<p>However, it’s extremely difficult for a model to estimate the maximum wind speed of a tropical cyclone at any given future time. Models are inexact in their descriptions of the entire state of the atmosphere and ocean at the start time of the model. Small-scale features of tropical cyclones – like sharp gradients in rainfall, surface winds and wave heights within and outside of the tropical cyclones – <a href="https://doi.org/10.1175/JAS-D-16-0026.1">are not as reliably captured in the forecast models</a>. </p>
<p>Both atmospheric and ocean characteristics can influence storm intensity. Scientists now think that <a href="http://www.aoml.noaa.gov/phod/trinanes/HHP/">better information about the ocean</a> could offer the the greatest gains in forecast accuracy. Of specific interest is the energy stored in the upper ocean and how this varies with ocean features such as eddies. Current observations are not sufficiently effective at placing ocean eddies in the correct location, nor are they effective in <a href="https://doi.org/10.1175/MWR-D-14-00285.1">capturing the size of these eddies</a>. For conditions where the atmosphere doesn’t severely limit hurricane growth, this oceanic information should be very valuable. </p>
<p>Meanwhile, forecasters are pursuing alternative and complementary metrics, like <a href="http://dx.doi.org/10.1175/WAF-D-14-00149.1">the size of tropical cyclones</a>.</p>
<p><em>This is an updated version of an article originally published on Sept. 12, 2018.</em></p><img src="https://counter.theconversation.com/content/102827/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Bourassa has received support from NASA and NOAA.</span></em></p><p class="fine-print"><em><span>Vasu Misra receives funding from NOAA, NSF, NASA</span></em></p>
How do experts know when and where the next big hurricane is going to hit? A look at the complicated science of forecasting.
Mark Bourassa, Professor of Meteorology, Florida State University
Vasu Misra, Associate Professor of Meteorology, Florida State University
Licensed as Creative Commons – attribution, no derivatives.