tag:theconversation.com,2011:/id/topics/tropical-cyclone-7914/articlestropical cyclone – The Conversation2024-03-12T19:15:29Ztag:theconversation.com,2011:article/2250882024-03-12T19:15:29Z2024-03-12T19:15:29ZPacific Islanders have long drawn wisdom from the Earth, the sky and the waves. Research shows the science is behind them<p>One afternoon last year, we sat in a village hall in Fiji chatting to residents about traditional ways of forecasting tropical cyclones. One man mentioned a black-winged storm bird known as “manumanunicagi” that glides above the land only when a cyclone is forming out to sea. As the conversation continued, residents named at least 11 bird species, the odd behaviour of which signalled imminent changes in the weather. </p>
<p>As we were leaving later that evening, an elder took us aside. He was pleased we had taken their beliefs seriously and said many older Pacific people won’t talk about traditional knowledge for fear of ridicule.</p>
<p>This reflects the dominance of science-based understandings in adapting to climate change and its threats to ways of life. Our <a href="https://wires.onlinelibrary.wiley.com/doi/10.1002/wcc.882">new research</a> suggests this attitude should change. </p>
<p>We reviewed evidence on traditional knowledge in the Pacific for coping with climate change, and found much of it was scientifically plausible. This indicates such knowledge should play a significant role in sustaining Pacific Island communities in future.</p>
<h2>A proven, robust system</h2>
<p>Our research was co-authored with 26 others, most Pacific Islanders with long-standing research interests in traditional knowledge.</p>
<p>People have inhabited the Pacific Islands for 3,000 years or <a href="https://www.routledge.com/Archaeology-of-Pacific-Oceania-Inhabiting-a-Sea-of-Islands/Carson/p/book/9781032486376">more</a> and have experienced many climate-driven challenges to their livelihoods and survival. They have coped not by luck but by design – through robust systems of traditional knowledge built by diverse groups of people over time.</p>
<p>The main short-term climate-related threats to island livelihoods in the Pacific are tropical cyclones which can damage food crops, pollute fresh water and destroy infrastructure. Prolonged droughts – common during El Niño events in the southwest Pacific – <a href="https://doi.org/10.1007/s10584-021-03112-1">also cause</a> widespread damage.</p>
<p>Traditional knowledge in the Pacific explains the causes and manifestations of natural phenomena, and identifies the best ways to respond. It is commonly communicated orally between generations. </p>
<p>Here, we describe such knowledge relating to animals, plants, water and sky – and show how these beliefs make scientific sense.</p>
<p>It’s important to note, however, that traditional knowledge has its own intrinsic value. Scientific explanations are not required to validate it.</p>
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Read more:
<a href="https://theconversation.com/secrets-in-the-canopy-scientists-discover-8-striking-new-bee-species-in-the-pacific-222599">Secrets in the canopy: scientists discover 8 striking new bee species in the Pacific</a>
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<h2>Reading the ocean and sky</h2>
<p>Residents of Fiji’s Druadrua Island interpret breaking waves to predict a cyclone as long as one month before it hits. In Vanuatu’s Torres Islands, 13 phrases exist to describe the state of the tide, including anomalies that <a href="https://doi.org/10.1002/j.1834-4461.2004.tb02856.x">herald uncommon events</a>.</p>
<p>These observations make scientific sense. Distant storms can drive ocean swells onto coasts long before the winds and rain arrive, changing the usual patterns of waves.</p>
<p>In Samoa, <a href="https://journals.sagepub.com/doi/abs/10.1177/25148486211047739">ten types of wind</a> are recognised in traditional lore. Winds that blow from the east (matā ‘upolu) indicate the imminent arrival of heavy rain, possibly a tropical cyclone. The south wind (tuā'oloa) is most feared. It will cease to blow, it is said, only when its appetite for death is <a href="https://link.springer.com/article/10.1007/s10584-009-9722-z">sated</a>.</p>
<p>Many Pacific Island communities believe a cloudless, dark blue sky signals the arrival of a tropical cyclone. Other signs include unusually rapid cloud movements and the appearance of “short rainbows”. </p>
<p>These beliefs are supported by science. Rainbows are sometimes “shortened” or partly obscured by a distant rain shower. And Western science has <a href="https://link.springer.com/book/10.1007/978-0-387-71543-8">long recognised</a> changes in clouds and winds can signal the development of cyclones.</p>
<p>In Vanuatu, a halo around a moon signals <a href="https://doi.org/10.1175/wcas-d-13-00053.1">imminent rainfall</a>. Again, this belief is scientifically sound. According to Western science, high thin cirrus clouds signal nearby storms. The clouds contain ice crystals through which moonlight is filtered, creating a halo effect.</p>
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Read more:
<a href="https://theconversation.com/teaching-our-children-from-books-not-the-sea-how-climate-change-is-eroding-human-rights-in-vanuatu-192016">'Teaching our children from books, not the sea': how climate change is eroding human rights in Vanuatu</a>
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<h2>The wisdom of animals and plants</h2>
<p>As mentioned above, birds are are said to herald weather changes across the Pacific.</p>
<p>In Tonga, when the frigate bird flies across the land – unusual behaviour for an ocean species – it signals a tropical cyclone is developing. This traditional knowledge is captured in the logo of the <a href="https://met.gov.to">Tonga Meteorological Service</a>. Birds are similarly interpreted in <a href="https://doi.org/10.1080/17477891.2015.1046156">Fiji</a> and <a href="https://doi.org/10.1177/25148486211047739">northern Vanuatu</a>.</p>
<p>This belief stacks up scientifically. One <a href="https://doi.org/10.1016/j.cub.2014.10.079">study</a> in North America, for example, showed golden-winged warblers dodged tornadoes by detecting shifts in infrasound. Another <a href="https://doi.org/10.1038/s41598-019-41481-x">study</a>, which included data on frigate birds in the Pacific, found seabirds appeared to circumvent cyclones, probably by sensing wind strength and direction.</p>
<figure class="align-right ">
<img alt="plantain tree in field" src="https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=799&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=799&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=799&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581159/original/file-20240312-18-84kk3r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">When the central shoot of the plantain is curled, people know a cyclone is developing.</span>
<span class="attribution"><span class="source">Patrick Nunn</span></span>
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<p>Traditional knowledge about insect behaviour in the Pacific Islands is also used to predict wet weather.</p>
<p>Bees, wasps and hornets usually build nests in tree branches. When nests are built close to the ground, Pacific Islanders know the forthcoming wet season will be wetter than normal, probably due to more tropical cyclones. This type of nest-building may <a href="https://doi.org/10.1080/17477891.2015.1046156">prompt</a> residents to make appropriate preparations such as storing food.</p>
<p>Studies suggest insect behaviour can predict changes in weather. For example, <a href="https://doi.org/10.1016/j.crvi.2009.10.007">a study</a> of wasp nesting in French Guiana found their ability to quickly move nests to more sheltered locations may help them survive wet years.</p>
<p>Across the Pacific, common signs of impending wet weather are found in the <a href="https://doi.org/10.1007/s10113-020-01613-w">behaviours</a> of <a href="https://doi.org/10.5751/ES-08100-210207">some plants</a>. The central shoot of the plantain, for example, will be conspicuously curled instead of straight.</p>
<p>This can be <a href="https://doi.org/10.1093/jxb/eru327">explained</a> scientifically by a process in which plant leaves close to protect their reproductive organs from extreme weather.</p>
<h2>Planning for a warmer future</h2>
<p>Since colonisation imposed Western worldviews around the world, traditional knowledge has been sidelined. This is true of the Pacific Islands, where in some places, traditional knowledge is all but <a href="https://theconversation.com/teaching-our-children-from-books-not-the-sea-how-climate-change-is-eroding-human-rights-in-vanuatu-192016">forgotten</a>. </p>
<p>But both Western and traditional knowledges have their pros and cons. Science-based knowledge, for example, is generic and often can’t realistically be applied <a href="https://theconversation.com/pacific-islands-must-stop-relying-on-foreign-aid-to-adapt-to-climate-change-because-the-money-wont-last-132095">at local scales</a>. </p>
<p>As climate change impacts worsen, optimal planning for island peoples should combine both approaches. This will require open-mindedness and a respect for diverse sources of knowledge.</p><img src="https://counter.theconversation.com/content/225088/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Patrick D. Nunn receives funding from the Department of Foreign Affairs and Trade (DFAT) via the Australia Pacific Climate Partnership (APCP), the Australian Research Council, and the Asia-Pacific Network for Global Change Research.</span></em></p><p class="fine-print"><em><span>Roselyn Kumar receives funding from the Department of Foreign Affairs and Trade (DFAT) via the Australia Pacific Climate Partnership (APCP)</span></em></p>We reviewed evidence on traditional knowledge in the Pacific for coping with climate change, and found much of it was scientifically plausible.Patrick D. Nunn, Professor of Geography, School of Law and Society, University of the Sunshine CoastRoselyn Kumar, Adjunct Research Fellow in Geography and Social Sciences, University of the Sunshine CoastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2217372024-01-24T03:26:11Z2024-01-24T03:26:11ZAs another cyclone heads for Queensland, we must be ready for the new threat: torrential rain and floods<figure><img src="https://images.theconversation.com/files/571073/original/file-20240124-15-lfd1t.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3999%2C2999&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>We’ve long known cyclones are <a href="https://media.bom.gov.au/social/blog/46/a-look-inside-the-structure-of-a-tropical-cyclone/">heat engines</a>, fuelled by hot water. They also pump heat from the hot tropics into <a href="https://www.noaa.gov/jetstream/tropical/tropical-cyclone-introduction">cooler areas</a>. But they’re starting to behave differently. As the world heats up, the atmosphere can hold more moisture. When cyclones form, they can transfer significantly more water from oceans to land. </p>
<p>We saw this in December. Most of the damage done by Cyclone Jasper when it hit far north Queensland wasn’t from the intense winds. It was when the Category 2 storm stalled over Cape York, dumping huge amounts of rain – over 2 metres in some areas – and triggering devastating floods. </p>
<p>It’s likely to happen again this week, as a slow-moving tropical low heads for northern Queensland, carrying huge volumes of water and <a href="https://www.9news.com.au/national/cyclone-kirrily-updates-system-likely-to-bring-heavy-rain-and-destructive-winds-to-north-queensland/1df6528e-3028-40bc-8c32-868ba005488f">threatening new floods</a>. Authorities are warning people to prepare – not just on the coast but well inland. </p>
<p>The storm – likely to be named Cyclone Kirrily – will be the second to make landfall this season. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/571074/original/file-20240124-17-olrpe6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map of queensland" src="https://images.theconversation.com/files/571074/original/file-20240124-17-olrpe6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/571074/original/file-20240124-17-olrpe6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=540&fit=crop&dpr=1 600w, https://images.theconversation.com/files/571074/original/file-20240124-17-olrpe6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=540&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/571074/original/file-20240124-17-olrpe6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=540&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/571074/original/file-20240124-17-olrpe6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=678&fit=crop&dpr=1 754w, https://images.theconversation.com/files/571074/original/file-20240124-17-olrpe6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=678&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/571074/original/file-20240124-17-olrpe6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=678&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">Rain from Cyclone Kirrily is likely to stretch well inland. This map shows the rainfall forecast for Friday January 26th.</span>
<span class="attribution"><span class="source">Bureau of Meteorology</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<h2>Cyclone Kirrily: Prepare for floods as well as winds</h2>
<p>The tropical storm has taken a long time to intensify and is moving very slowly. While it hasn’t yet reached cyclone status, it is expected to make landfall as a <a href="https://www.abc.net.au/news/2024-01-24/tropical-cyclone-kirrily-category-two-queensland-bom/103378666">Category 2 storm</a>.</p>
<p>What it is carrying, though, is water – enough to dump up to a metre of rain in some places, and a long way into central and western Queensland. </p>
<p>If you live in northern Australia, you’ll know about <a href="https://www.getready.qld.gov.au/getting-ready/cyclones">being prepared</a> for cyclones. When a warning arrives, people pack away or tie down loose objects, trim tree branches and fill up the bathtub in case water supplies are disrupted. </p>
<p>But often, we’re focused just on the damaging winds – when water can often do more damage. </p>
<p>If you live close to the sea, the storm surge – flooding from the sea – is often underestimated as a threat.</p>
<p>But the new major threat is terrestrial flooding. We are already starting to see <a href="https://www.nature.com/articles/s41558-022-01344-2">significantly more rainfall</a> linked to cyclones. Warmer air holds more moisture, and the world is steadily heating up. </p>
<p>This summer, sea surface temperatures have been unusually high off the east coast, all the way from Cape York down to Tasmania. Normally, in El Niño, we would expect lower sea surface temperatures and higher air temperatures. But this El Niño isn’t behaving as we’d normally expect. That’s one reason the east coast has had so much summer rain. </p>
<p>Normally, 75% of Australia’s cyclones hit the northwest of Western Australia, due to the high sea surface temperatures and the way the coast is oriented. But this year, the northwest region is sweltering in heatwaves – but no cyclones have yet made landfall. </p>
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Read more:
<a href="https://theconversation.com/north-queenslands-record-breaking-floods-are-a-frightening-portent-of-whats-to-come-under-climate-change-220039">North Queensland's record-breaking floods are a frightening portent of what's to come under climate change</a>
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<h2>The future has fewer cyclones, but more intense</h2>
<p>Climate change is expected to change tropical cyclone patterns. The overall number is expected to decrease, but their intensity will likely <a href="http://www.bom.gov.au/cyclone/climatology/trends.shtml">increase</a>, bringing stronger wind and heavier rain.</p>
<p>My colleagues and I have found the change is already happening. The low levels of storm activity on the mid west and northeast coasts of Australia <a href="https://www.nature.com/articles/nature12882#:%7E:text=There%20has%20been%20significantly%20less,22.42%2C%20P%20%3C%200.001">are unprecedented</a> over the past 550 to 1,500 years. </p>
<p><a href="https://www.nature.com/articles/nature07234">More intense</a> tropical cyclones are expected because higher sea-surface temperatures will make the atmosphere more warm and moist. Cyclones thrive in such conditions.</p>
<p>But the general frequency of tropical cyclones is expected to <a href="https://www.climatecouncil.org.au/uploads/3cf983377b8043ff1ecf15709eebf298.pdf">reduce</a> under climate change in most ocean basins, including the Indian Ocean.</p>
<p>Tropical cyclones usually form when there’s a large difference between temperatures at Earth’s surface and the upper atmosphere. As the climate warms, this temperature difference is <a href="https://www.ipcc.ch/report/managing-the-risks-of-extreme-events-and-disasters-to-advance-climate-change-adaptation/">likely to narrow</a>.</p>
<p>As the heat in the oceans intensifies, cyclones will be able to form further down the east coast. Cyclones have hit Brisbane and even northern New South Wales in the past. These tropical storms form over warm water – between 26.5 and 30°C. The water along Kirrily’s track is at the higher end – around 30°C. Warm water produces warm, moist air, which is the energy-dense feedstock of cyclones. </p>
<h2>What should we do to prepare?</h2>
<p>In states such as Queensland, emergency response is a finely honed art. We’re excellent at dealing with the emergency when it’s happening and the immediate aftermath. </p>
<p>But we’ve still got a long way to go in mitigation. Houses are still being built in the path of flooding rivers or where they can be hit by storm surge. </p>
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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>
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<img src="https://counter.theconversation.com/content/221737/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Nott does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The new threat from cyclones can come from behind you – flooding from more intense rainfall.Jonathan Nott, Professor of Physical Geography, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2074932023-06-12T22:37:26Z2023-06-12T22:37:26ZEl Niño combined with global warming means big changes for New Zealand’s weather<figure><img src="https://images.theconversation.com/files/531272/original/file-20230612-84194-6x3bxx.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6720%2C4466&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Getty Images</span></span></figcaption></figure><p>El Niño is officially here, according to the US National Oceanic and Atmospheric Administration, and with it comes a change from the La Niña weather patterns New Zealand has experienced for the past three years.</p>
<p>In particular, a switch from prevailing northeasterlies to southwesterlies means New Zealand is one of the few countries where cooler conditions are felt during El Niño. But what “flavour” will this El Niño be?</p>
<p>Time will tell, but El Niño has been looming for some time. Evidence of its imminent arrival could be seen last year in subsurface ocean temperatures, with a buildup of warm water in the Coral Sea and western tropical Pacific.</p>
<p>Moreover, it was overdue. When La Niña finally gave up the ghost in March this year, global sea surface temperatures were suddenly the highest on record (Figure 1 below), as the tropical Pacific abruptly began to warm. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/531270/original/file-20230612-29-braw6w.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/531270/original/file-20230612-29-braw6w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531270/original/file-20230612-29-braw6w.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=342&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531270/original/file-20230612-29-braw6w.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=342&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531270/original/file-20230612-29-braw6w.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=342&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531270/original/file-20230612-29-braw6w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=430&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531270/original/file-20230612-29-braw6w.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=430&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531270/original/file-20230612-29-braw6w.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=430&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">Figure 1. Global mean sea surface temperatures (with other calendar years in grey), showing 2023’s record highs.</span>
<span class="attribution"><a class="source" href="https://climatereanalyzer.org/clim/sst_daily/">University of Maine</a>, <span class="license">Author provided</span></span>
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<p>Meanwhile, record high sea surface temperatures in the extratropical North and South Pacific were partly a signature from La Niña and partly a sign of global warming. The resulting “atmospheric rivers” delivered torrential rains to California in the north and New Zealand in the south.</p>
<p>These sea surface temperature changes can be readily seen by comparing variations from mean temperatures for December 2022 versus May 2023 (Figure 2 below). We can see a startling transformation throughout the central tropical Pacific, with a coastal El Niño off Peru and Ecuador strongly evident. </p>
<p>Modest cooling in the eastern North Pacific is associated with the train of storms that barrelled into the West Coast of the US and in northwest Australia from Cyclone Ilsa.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/531271/original/file-20230612-151713-wk6u4j.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/531271/original/file-20230612-151713-wk6u4j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531271/original/file-20230612-151713-wk6u4j.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=643&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531271/original/file-20230612-151713-wk6u4j.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=643&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531271/original/file-20230612-151713-wk6u4j.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=643&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531271/original/file-20230612-151713-wk6u4j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=808&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531271/original/file-20230612-151713-wk6u4j.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=808&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531271/original/file-20230612-151713-wk6u4j.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=808&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fig 2. Sea surface temperature changes (measured by departure from the mean), comparing December 2022 and May 2023.</span>
<span class="attribution"><a class="source" href="https://www.climate.gov/maps-data/data-snapshots/data-source/sst-global-monthly-difference-average">National Oceanic and Atmospheric Administration</a>, <span class="license">Author provided</span></span>
</figcaption>
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<h2>El Niño and New Zealand</h2>
<p>The weather in the tropics is seldom average, however. It tends to fluctuate more like a roller coaster. In the atmosphere, this is referred to as the Southern Oscillation. The combined atmosphere and ocean phenomenon is often referred to as the El Niño-Southern Oscillation (ENSO). </p>
<p>The bottom of the roller coaster is the cold phase: a basin-wide cooling of the tropical Pacific, named La Niña, while the top of the roller coaster is El Niño, which occurs every three to seven years or so. The most intense phase of each event typically lasts half a year.</p>
<p>But El Niños can be very strong, and hence highly anomalous. La Niñas, by comparison, are usually moderate in strength and occur more often. </p>
<p>El Niños tend to peak in December, although their biggest atmospheric impacts may not be until February. The last major El Niño was in 2016-17, while a weak El Niño occurred in 2019-20. </p>
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Read more:
<a href="https://theconversation.com/el-nino-is-back-thats-good-news-or-bad-news-depending-on-where-you-live-205974">El Niño is back – that's good news or bad news, depending on where you live</a>
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<h2>Coupled oceans and atmosphere</h2>
<p>In the tropical Pacific Ocean, the atmosphere and ocean are strongly coupled. Surface winds drive surface ocean currents, and largely determine the sea surface temperature distribution, the differential sea levels, and the <a href="https://doi.org/10.1175/JCLI-D-18-0607.1">heat content of the upper ocean</a>. In turn, the sea surface temperatures determine the winds. </p>
<p>Cool waters limit atmospheric convection and storm activity, while high sea surface temperatures attract convection, clusters of thunderstorms, and tropical cyclones (off the equator, where Earth’s rotation comes into play). </p>
<p>Heat that was stored up in the tropical western Pacific during La Niña is moved around and into the atmosphere during El Niño, mainly through evaporation. This cools the ocean and moistens the atmosphere. </p>
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Read more:
<a href="https://theconversation.com/2023-hurricane-forecast-get-ready-for-a-busy-pacific-storm-season-quieter-atlantic-than-recent-years-thanks-to-el-nino-204526">2023 hurricane forecast: Get ready for a busy Pacific storm season, quieter Atlantic than recent years thanks to El Niño</a>
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<p>This alters where the main rainfall occurs. In turn, it changes the latent heating of the atmosphere that sets up “<a href="https://www.climate.gov/news-features/blogs/what-are-teleconnections-connecting-earths-climate-patterns-global-information">teleconnections</a>” (links between weather phenomena in different parts of the globe) and major changes in the jet streams and extratropical storm tracks in both hemispheres – including across New Zealand, especially in winter. </p>
<p>Because most action occurs over the tropical Pacific Ocean, more settled weather and dry spells often occur over land. </p>
<p>The warmest years in terms of global mean surface temperature are the latter stages of El Niño events. 2016 is the world’s warmest year on record, in part because of the very strong El Niño event. But 2023 could beat that record – and odds are that 2024 will beat it by a lot. </p>
<p>So far, there is little evidence that climate change has altered ENSO events themselves. But all impacts of El Niño are exacerbated by global warming, including extremes of the hydrological cycle involving floods and droughts, which are already common with ENSO. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1667351422592241669"}"></div></p>
<h2>Impacts of El Niño</h2>
<p>Of course, major events related to El Niño have serious social and economic impacts, too. Droughts, floods, heatwaves and other changes can severely disrupt agriculture, fisheries, health, energy demand and air quality (mainly from wildfires).</p>
<p><a href="https://doi.org/10.1126/science.adf2983">Research shows</a> El Niño “persistently reduces country-level economic growth”, with damage now estimated in the trillions of US dollars.</p>
<p>Globally, El Niño is the <a href="https://doi.org/10.1002/9781119548164.ch2">largest cause of droughts</a>; they are more intense, set in quicker and increase the risk of wildfires, especially in Australia, Indonesia and Brazil. In the weak 2019-20 El Niño, smoke from fires in eastern Australia affected the southern hemisphere to the extent that it blocked the sun and may have <a href="https://doi.org/10.1126/sciadv.adg1213">exacerbated</a> the subsequent La Niña conditions. </p>
<p>Meanwhile, torrential rains are heavier, with greater risk of flooding, especially in Peru and Ecuador. Very wet conditions can also (though not always) occur in California and the southeast US. </p>
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Read more:
<a href="https://theconversation.com/new-study-helps-solve-a-30-year-old-puzzle-how-is-climate-change-affecting-el-nino-and-la-nina-205128">New study helps solve a 30-year-old puzzle: how is climate change affecting El Niño and La Niña?</a>
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<h2>Another ‘super’ El Niño?</h2>
<p>New Zealand had its <a href="https://www.rnz.co.nz/news/national/482221/2022-confirmed-as-country-s-warmest-year-on-record">highest annual mean surface temperature</a> on record in 2022. In the past year the preponderance of northeasterlies due to La Niña has seen an unprecedented number of tropical and subtropical storms bombarding the country. </p>
<p>The record rain event in Auckland on January 27, and Cyclone Gabrielle just three weeks later, were just two among many such events. </p>
<p>By contrast, New Zealand tends to experience stronger and more frequent winds from the southwest in winter and from the west in summer during El Niño. This can encourage dryness in eastern areas and more rain on the West Coast, with generally cooler conditions overall.</p>
<p>But <a href="https://doi.org/10.1002/9781119548164.ch2">El Niño varies</a>, and there have been three “super” El Niños: 1982-83, 1997-98 and 2015-16. It remains to be seen whether the latest will join them. But together with the augmenting effects of global warming, any El Niño can be very disruptive. We need to be vigilant.</p><img src="https://counter.theconversation.com/content/207493/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kevin Trenberth 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>2016 was the world’s warmest year on record, due in part to a very strong El Niño event. But 2023 (and 2024) could beat that record – what should we expect?Kevin Trenberth, Distinguished Scholar, NCAR; Affiliate Faculty, University of Auckland, Waipapa Taumata RauLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2036782023-04-13T03:17:57Z2023-04-13T03:17:57ZAnatomy of monster storm: how Cyclone Ilsa is shaping up to devastate the WA coast<figure><img src="https://images.theconversation.com/files/520672/original/file-20230413-2318-vmd96d.jpeg?ixlib=rb-1.1.0&rect=19%2C0%2C673%2C626&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">BoM</span></span></figcaption></figure><p>Residents along Western Australia’s northwest coast are bracing for Tropical Cyclone Ilsa, which is <a href="https://edition.cnn.com/2023/04/12/australia/cyclone-ilsa-western-australia-intl-hnk/index.html">expected</a> to be one of the most destructive storms to strike the region in more than a decade.</p>
<p>The Bureau of Meteorology <a href="https://www.abc.net.au/news/2023-04-13/wa-cyclone-ilsa-upgraded-category-5-pilbara-kimberley-/102219020">says</a> Cyclone Ilsa will intensify into a category-five storm when it hits the WA coast between Port Hedland and Bidyadanga Thursday night or Friday morning.</p>
<p>Tropical cyclones are huge low-pressure systems that form in tropical waters. They can bring extreme winds, heavy rain and damaging waves, destroying infrastructure and the environment and causing injury and death.</p>
<p>Let’s take a look at how Cyclone Ilsa developed, and what we can expect from cyclones in this region in future.</p>
<h2>Why did Cyclone Ilsa intensify?</h2>
<p>Tropical Cyclone Ilsa is the first system of category-four or higher to cross Australian shores since <a href="http://www.bom.gov.au/cyclone/history/Trevor.shtml">Cyclone Trevor</a> crossed the coast of the Gulf of Carpentaria in 2019.</p>
<p>Ilsa formed off the Northern Territory coast before tracking southwest towards Western Australia’s Kimberley region. It developed quickly on Tuesday into a category-two system, which <a href="http://www.bom.gov.au/cyclone/tropical-cyclone-knowledge-centre/understanding/tc-info/">involves</a> wind gusts between 125 km/h and 164 km/h.</p>
<p>The cyclone on Thursday intensified to a category-five storm, which involves winds gusts above 279 km/h. This was due to two main factors: high sea-surface temperatures and favourable conditions in the upper atmosphere. </p>
<p>Tropical cyclones require sea-surface temperatures <a href="http://www.bom.gov.au/cyclone/tropical-cyclone-knowledge-centre/understanding/tc-info/">above 27°C</a>. This provides warm, moist air that generates a massive amount of energy and fuels the cyclone.</p>
<p>Upper atmospheric conditions influence wind speed. Air is drawn in toward the centre of a tropical cyclone. In the Southern Hemisphere, the air spirals upwards in a clockwise direction then moves outwards to the upper troposphere, away from the storm. This air is known as “outflow”.</p>
<p>Cyclone Ilsa’s path led it into a region where the upper level wind was relatively light, which enhanced outflow. </p>
<p>As air moved outwards, more wind or “inflow” was drawn toward the centre of the system from the sea surface, bringing warmth and moisture. This enabled Cyclone Ilsa to rapidly intensify. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1645699026501906438"}"></div></p>
<h2>Australia’s cyclone capital</h2>
<p>Northwest WA is Australia’s most cyclone-prone region. Records since 1970 show <a href="http://www.bom.gov.au/cyclone/climatology/wa.shtml">about 75%</a> of severe cylones to make landfall in Australia occur in this region.</p>
<p>But why? It comes down to two things: the high sea surface temperatures in this part of the Indian Ocean, and the orientation of the coast. </p>
<p>Tropical cyclones tend to <a href="https://www.britannica.com/science/tropical-cyclone/Location-and-patterns-of-tropical-cyclones">move polewards</a> and, in the Southern Hemisphere, often curve southeast. The coast of northwest WA is oriented northeast/southwest, and so perfectly aligned to intercept these cyclones.</p>
<p>Several intense tropical cyclones have developed in the warm waters off northwest WA in recent years. However, the number to reach land in this region has been lower than average. That’s because mid- to higher-level atmospheric winds that steer tropical cyclones have directed many of them <a href="http://www.bom.gov.au/cyclone/tropical-cyclone-knowledge-centre/history/past-tropical-cyclones/">away</a> from the WA coast. </p>
<figure class="align-center ">
<img alt="satellite image of cyclone off WA" src="https://images.theconversation.com/files/520678/original/file-20230413-28-d238j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/520678/original/file-20230413-28-d238j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/520678/original/file-20230413-28-d238j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/520678/original/file-20230413-28-d238j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/520678/original/file-20230413-28-d238j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/520678/original/file-20230413-28-d238j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/520678/original/file-20230413-28-d238j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">In the Southern Hemisphere, tropical cyclones often curve southeast.</span>
<span class="attribution"><span class="source">BoM</span></span>
</figcaption>
</figure>
<h2>What about climate change?</h2>
<p>Climate change is expected to change tropical cyclone patterns. The overall number is expected to decrease, but their intensity will likely <a href="http://www.bom.gov.au/cyclone/climatology/trends.shtml">increase</a>, bringing stronger wind and heavier rain. </p>
<p><a href="https://www.nature.com/articles/nature07234">More intense</a> tropical cyclones are expected because higher sea-surface temperatures will make the atmosphere more warm and moist. Cyclones thrive in such conditions.</p>
<p>But the general frequency of tropical cyclones is expected to <a href="https://www.climatecouncil.org.au/uploads/3cf983377b8043ff1ecf15709eebf298.pdf">reduce</a> under climate change in most ocean basins, including the Indian Ocean. </p>
<p>Tropical cyclones usually form when there’s a large difference between temperatures at Earth’s surface and the upper atmosphere. As the climate warms, this temperature difference is <a href="https://www.ipcc.ch/report/managing-the-risks-of-extreme-events-and-disasters-to-advance-climate-change-adaptation/">likely to narrow</a>.</p>
<p>Research last year <a href="https://theconversation.com/research-shows-tropical-cyclones-have-decreased-alongside-human-caused-global-warming-but-dont-celebrate-yet-185706">showed</a> the annual number of tropical cyclones forming globally decreased by about 13% during the 20th century compared to the 19th. </p>
<p>The activity of tropical cyclones in any one ocean basin over a year is measured by what’s known as the “Accumulated Cyclone Energy” or <a href="https://www.cpc.ncep.noaa.gov/products/outlooks/hurricane2003/August/background_information.html">ACE</a> Index.</p>
<p>The index is calculated by measuring the cyclone’s wind speed every six hours squaring it, then adding these values together.</p>
<p><a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021GL095774">A study</a> has shown the index values for cyclone activity in the Southern Indian Ocean have decreased significantly since 1990.</p>
<p>I specialise in reconstructing long-term natural records of extreme events. <a href="https://www.nature.com/articles/nature12882">Research</a> by myself and colleagues has shown tropical cyclone activity along the WA coast is at its lowest level since approximately 500 CE – about 1,500 years ago.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/cyclone-seroja-just-demolished-parts-of-wa-and-our-warming-world-will-bring-more-of-the-same-158769">Cyclone Seroja just demolished parts of WA – and our warming world will bring more of the same</a>
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<h2>We’re not off the hook</h2>
<p>Tropical cyclones maintain energy over warm water, and lose energy once they move over land or cooler oceans.</p>
<p>Cyclone Ilsa is expected to weaken overnight on Friday as it moves east into the Northern Territory.</p>
<p>Climate change will lead to fewer tropical cyclones overall. But those that do occur will be more intense and damaging. So unfortunately, WA can expect regular cyclone impacts even as the climate warms.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/tropical-cyclone-frequency-falls-to-centuries-low-in-australia-but-will-the-lull-last-20814">Tropical cyclone frequency falls to centuries-low in Australia – but will the lull last?</a>
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<img src="https://counter.theconversation.com/content/203678/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Nott 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>Cyclone Ilsa has intensified off the Western Australian coast and is now classed as a category-five system. How did this happen?Jonathan Nott, Professor of Physical Geography, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1857062022-06-27T19:51:02Z2022-06-27T19:51:02ZResearch shows tropical cyclones have decreased alongside human-caused global warming – but don’t celebrate yet<figure><img src="https://images.theconversation.com/files/470720/original/file-20220624-21-prz1gx.jpg?ixlib=rb-1.1.0&rect=0%2C50%2C5615%2C3682&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>The annual number of tropical cyclones forming globally decreased by about 13% during the 20th century compared to the 19th, according to research <a href="https://www.nature.com/articles/s41558-022-01388-4">published today</a> in Nature Climate Change.</p>
<p>Tropical cyclones are massive low-pressure systems that form in tropical waters when the underlying environmental conditions are right. These conditions include (but aren’t limited to) sea surface temperature, and variables such as vertical wind shear, which refers to changes in wind speed and direction with altitude.</p>
<p><a href="http://www.bom.gov.au/cyclone/tropical-cyclone-knowledge-centre/history/past-tropical-cyclones/">Tropical cyclones</a> can cause a lot of damage. They often bring extreme rainfall, intense winds and coastal hazards including erosion, destructive waves, storm surges and estuary flooding.</p>
<p>The Intergovernmental Panel on Climate Change’s latest <a href="https://www.ipcc.ch/report/ar6/wg1/">report</a> detailed how human emissions have warmed tropical oceans above pre-industrial levels, with most warming happening since around the middle of the 20th century. Such changes in sea surface temperature are expected to intensify storms.</p>
<p>At the same time, global warming over the 20th century led to a weakening of the underlying atmospheric conditions that affect tropical cyclone formation. And our research now provides evidence for a decrease in the frequency of tropical cyclones coinciding with a rise in human-induced global warming.</p>
<h2>Reckoning with a limited satellite record</h2>
<p>To figure out whether cyclone frequency has increased or decreased over time, we need a reliable record of cyclones. But establishing this historical context is challenging. </p>
<p>Before the introduction of geostationary weather satellites in the 1960s (which stay stationary in respect to the rotating Earth), records were prone to discontinuity and sampling issues.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/470718/original/file-20220624-22-cfq05j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Black and white image of beach hit by big winds" src="https://images.theconversation.com/files/470718/original/file-20220624-22-cfq05j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/470718/original/file-20220624-22-cfq05j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=239&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470718/original/file-20220624-22-cfq05j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=239&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470718/original/file-20220624-22-cfq05j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=239&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470718/original/file-20220624-22-cfq05j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=301&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470718/original/file-20220624-22-cfq05j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=301&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470718/original/file-20220624-22-cfq05j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=301&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">Beaches at Bowen, Queensland, were photographed while being hit by a cyclone in 1903.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/5/58/StateLibQld_2_203408_Beach_at_Bowen_after_a_cyclone%2C_1903.jpg">Wikimedia</a></span>
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<p>And although observations improved during the satellite era, changes in satellite technologies and monitoring throughout the first few decades imply global records only became consistently reliable around the 1990s.</p>
<p>So we have a relatively short post-satellite tropical cyclone record. And longer-term weather trends based on a short record can be obscured by natural climate variability. This has led to conflicting assessments of tropical cyclone trends.</p>
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Read more:
<a href="https://theconversation.com/homes-can-be-better-prepared-for-cyclones-but-first-we-must-convince-the-owners-126515">Homes can be better prepared for cyclones. But first we must convince the owners</a>
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<h2>Declining global and regional trends</h2>
<p>To work around the limits of the tropical cyclone record, our team used the Twentieth Century Reanalysis <a href="https://psl.noaa.gov/data/20thC_Rean/">dataset</a> to reconstruct cyclone numbers to as far back as 1850. This reanalysis project uses detailed metrics to paint a picture of global atmospheric weather conditions since before the use of satellites.</p>
<p>Drawing on a link to the observed weakening of two major atmospheric circulations in the tropics – the Walker and Hadley circulations – our reconstructed record reveals a decrease in the annual number of tropical cyclones since 1850, at both a global and regional scale. </p>
<p>Specifically, the number of storms each year went down by about 13% in the 20th century, compared to the period between 1850 and 1900. </p>
<p>For most tropical cyclone basins (regions where they occur more regularly), including Australia, the decline has accelerated since the 1950s. Importantly, this is when human-induced warming also accelerated.</p>
<p>The only exception to the trend is the North Atlantic basin, where the number of tropical cyclones has increased in recent decades. This may be because the basin is recovering from a decline in numbers during the late 20th century due to <a href="https://www.nature.com/scitable/knowledge/library/aerosols-and-their-relation-to-global-climate-102215345/">aerosol</a> impacts.</p>
<p>But despite this, the annual number of tropical cyclones here is still lower than in pre-industrial times.</p>
<h2>It’s a good thing, right?</h2>
<p>While our research didn’t look at cyclone activity in the 21st century, our findings complement other <a href="https://journals.ametsoc.org/view/journals/bams/101/3/bams-d-18-0194.1.xml">studies</a>, which have predicted tropical cyclone frequency will decrease due to global warming.</p>
<p>It may initially seem like good news fewer cyclones are forming now compared to the second half of the 19th century. But it should be noted <em>frequency</em> is only one aspect of risk associated with tropical cyclones.</p>
<p>The geographical distribution of tropical cyclones is shifting. And they’ve been getting <a href="https://www.pnas.org/doi/full/10.1073/pnas.1922500117">more</a> <a href="https://www.pnas.org/doi/full/10.1073/pnas.1920849117">intense</a> in recent decades. In some parts of the world they’re moving closer to coastal areas with growing populations and developments.</p>
<p>These changes – coupled with increasing rain associated with tropical cyclones, and a trend towards hurricanes lasting longer after <a href="https://www.nature.com/articles/s41586-020-2867-7">making landfall</a> – could point to a future where cyclones cause unprecedented damage in tropical regions.</p>
<p>Then again, these other factors weren’t assessed in our study. So we can’t currently make any certain statements regarding future risk. </p>
<p>Moving forward, we hope improvements in climate modelling and data will help us identify how human-induced climate change has affected other metrics, such as cyclone intensity and landfalling activity.</p>
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Read more:
<a href="https://theconversation.com/factcheck-is-global-warming-intensifying-cyclones-in-the-pacific-38984">FactCheck: is global warming intensifying cyclones in the Pacific?</a>
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<img src="https://counter.theconversation.com/content/185706/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Savin Chand receives funding from the Australian Bureau of Meteorology and CSIRO through the Earth Systems and Climate Change Hub of the Australian Government’s National Environmental Science Program (NESP). </span></em></p>A reconstructed record of cyclone activity going as far back as 1850 has revealed interesting trends, both around Australia and globally.Savin Chand, Senior Lecturer, Applied Mathematics and Statistics, Federation University AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1729022021-12-06T15:35:01Z2021-12-06T15:35:01ZFloods are going to get worse: we need to start preparing for them now<figure><img src="https://images.theconversation.com/files/435311/original/file-20211202-17-1nipyqj.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C1235%2C825&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Floods across the world this year cost hundreds of lives and millions of pounds in damages. </span> <span class="attribution"><a class="source" href="https://www.freeimageslive.co.uk/free_stock_image/tunnelfloodedjpg">Brian Norcross/FreeImagesLive</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>For many, 2021 was the <a href="https://theecologist.org/2021/oct/11/year-flood">year of the flood</a>. From Canada to India, and across western Europe and Australia, this year’s deluges have led to hundreds of deaths, enormous financial costs and immeasurable suffering.</p>
<p>Research by <a href="https://discovery.ucl.ac.uk/id/eprint/10086364/">myself</a> and <a href="https://hazards.colorado.edu/gilbert-f-white">others</a> on flood risk around the world shows how changing our perspective on floods can help us avoid disasters. No matter how much rain falls, flood disasters happen because of decisions that put people and places in harm’s way – and they can be averted.</p>
<p>For example, the southern part of the province of <a href="https://theconversation.com/how-an-atmospheric-river-drenched-british-columbia-and-led-to-floods-and-mudslides-172021">British Columbia</a> in Canada has a <a href="https://www.env.gov.bc.ca/wsd/public_safety/flood/pdfs_word/floods_landslides_south1.pdf">lengthy history</a> of floods and landslides. <a href="https://www.nytimes.com/2021/11/29/world/canada/british-columbia-floods-storm.html">Deluges in November</a> killed at least four people, washed away highways and forced towns to evacuate. </p>
<p>The excessive rain that caused this was most likely <a href="https://theconversation.com/global-evidence-links-rise-in-extreme-precipitation-to-human-driven-climate-change-163715">exacerbated</a> by human-driven climate change, but its effects were made far worse by widespread deforestation, as well as the building of infrastructure on floodplains and even in a drained lake.</p>
<p>The 2018 <a href="https://theconversation.com/india-must-stop-deforesting-its-mountains-if-it-wants-to-fight-floods-122669">floods in Kerala</a>, in southern India, were also linked to deforestation and poor city planning, with increasing urban development a contributor to the <a href="https://www.bbc.co.uk/newsround/58924672">floods</a> in the region this year.</p>
<p>And in western Europe, many places hit by rising water in July 2021 – such as the town of <a href="https://www.alamy.com/altena-germany-15th-july-2021-flooded-streets-in-altena-after-heavy-rainfall-altena-in-the-sauerland-region-was-temporarily-inaccessible-after-landslides-and-flooding-credit-markus-klmperdpaalamy-live-news-image435008802.html">Altena</a> in Germany – were known to be at <a href="https://www.tandfonline.com/doi/abs/10.1080/02626669809492119">high flood risk</a> thanks to floods over past decades and centuries. Despite a flood alert system <a href="https://theconversation.com/europes-catastrophic-flooding-was-forecast-well-in-advance-what-went-so-wrong-164818">forecasting</a> heavy rain days in advance, this information was never translated into action.</p>
<figure class="align-center ">
<img alt="A rainbow above flooded land" src="https://images.theconversation.com/files/435316/original/file-20211202-20750-dfnjq3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435316/original/file-20211202-20750-dfnjq3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=447&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435316/original/file-20211202-20750-dfnjq3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=447&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435316/original/file-20211202-20750-dfnjq3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=447&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435316/original/file-20211202-20750-dfnjq3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=562&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435316/original/file-20211202-20750-dfnjq3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=562&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435316/original/file-20211202-20750-dfnjq3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=562&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Flooding in Germany caused huge amounts of damage.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Rainbow_at_flooded_Rhine,_Geisenheim.jpg">Gerda Arendt/Wikimedia</a></span>
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<p>Each of these tragic situations, however, could have been prevented from becoming a disaster by taking simple measures to reduce risk before storms strike: measures like planning buildings on safer, higher land, improving forest and river management, reducing poverty and providing relevant safety education.</p>
<h2>How to reduce risk</h2>
<p>In 1970, a <a href="http://www.ilankelman.org/disasterdeaths/sommeretal.1971.pdf">cyclone</a> tore through Bangladesh, causing hundreds of thousands of deaths. Another <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2393441/">cyclone</a> in 1991 killed over 100,000 people. But in subsequent decades concerted <a href="https://theconversation.com/bangladesh-has-saved-thousands-of-lives-from-a-devastating-cyclone-heres-how-139903">efforts</a> by governments and local leaders focused on risk awareness, <a href="https://www.nature.com/articles/nclimate2431">livelihood resilience</a> and evacuation procedures – these measures reduced the death toll across the country to just dozens when cyclones struck in 2020 and 2021.</p>
<p>Similar work saved thousands during hurricanes in Texas. In 1900, a <a href="https://texashistory.unt.edu/ark:/67531/metapth1220942/">hurricane</a> passing through the city of Galveston left at least 6,000 bodies in its wake. But more recently, Tropical Storm Allison in 2001, Hurricane Rita in 2005, Hurricane Ike in 2008 and Hurricane Harvey in 2017 each led to a much smaller loss of life.</p>
<p>For Rita, <a href="https://www.cambridge.org/core/journals/disaster-medicine-and-public-health-preparedness/article/abs/reflection-on-lessons-learned-an-analysis-of-the-adverse-outcomes-observed-during-the-hurricane-rita-evacuation/573A0EAE07C980BA0A97D4953174A33F">over 80%</a> of Texas’ 119 fatalities were attributed to poorly managed evacuation procedures. Similarly, despite record rainfall during Harvey, the hurricane’s <a href="https://theconversation.com/dont-blame-climate-change-for-the-hurricane-harvey-disaster-blame-society-83163">destruction</a> was largely the result of Texans covering floodable areas with buildings, without preparing citizens for what to do when floods hit.</p>
<h2>Dealing with water</h2>
<p>As climate change worsens, it’s <a href="https://journals.ametsoc.org/view/journals/bams/101/3/bams-d-18-0194.1.xml">projected</a> that tropical cyclones – and the floods they cause – will become less frequent but more intense. The consequences of future storms depend on our actions now. If fewer storms mean that our preparation for them becomes slapdash, then disasters will be worse.</p>
<figure class="align-center ">
<img alt="A motorway submerged in water" src="https://images.theconversation.com/files/435321/original/file-20211202-20099-vaoep7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435321/original/file-20211202-20099-vaoep7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435321/original/file-20211202-20099-vaoep7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435321/original/file-20211202-20099-vaoep7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435321/original/file-20211202-20099-vaoep7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435321/original/file-20211202-20099-vaoep7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435321/original/file-20211202-20099-vaoep7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">During Hurricane Katrina, thousands of people in New Orleans had to be rescued.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/smiteme/221291142">SmiteMe/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>We can see this <a href="https://www.tandfonline.com/doi/abs/10.3763/ehaz.1999.0109">phenomenon</a> at work when people build flood-related structures like <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1752-1688.1995.tb04025.x">dikes, levees and dams</a>. Since they create a barrier between water and floodable areas, people often assume that those areas are safe to build on and that they don’t need to worry about flood risk. Indeed, the structures get rid of many smaller floods. But when large floods <a href="https://rmets.onlinelibrary.wiley.com/doi/10.1002/j.1477-8696.2001.tb06507.x">inevitably occur</a> and a river or ocean reclaims its territories, devastation is equally inevitable.</p>
<p>The history of New Orleans offers a classic example. Around half of the city currently lies below sea level, and records of <a href="https://www.weather.gov/lix/ms_flood_history">city flooding</a> from the Mississippi River date back over a quarter of a millennium. Plus, New Orleans has always been prone to storms, facing Hurricane Betsy in 1965 and Hurricane Camille in 1969.</p>
<p>In July 2004, the <a href="https://www.govinfo.gov/content/pkg/CHRG-109shrg26749/html/CHRG-109shrg26749.htm">Hurricane Pam</a> training exercise for emergency officials demonstrated how ill-prepared the city was for a direct hurricane hit: especially when it came to hospital evacuation, search-and-rescue efforts, debris removal and temporary shelters. Tragically, this scenario was recreated in real life when <a href="https://theconversation.com/i-lived-through-hurricane-katrina-and-helped-design-the-rebuild-floods-will-always-come-but-we-can-build-better-to-prepare-153452">Hurricane Katrina</a> tore through the city in 2005. Levees breached, evacuation and sheltering systems were chaotic, and <a href="https://link.springer.com/chapter/10.1057/9781137486004_20">people drowned</a> while on the phone awaiting rescue.</p>
<p>Flood-prone cities are often “protected” by flood “defences”, which have served mainly to encourage housing and business development on floodable land such as in <a href="https://global.oup.com/academic/product/disaster-by-choice-9780198841340?cc=us&lang=en&">London and Singapore</a>. Both cities sit upstream from vast defences which reduce the numbers of small floods, allowing construction of huge financial centres on floodplains.</p>
<p>But when, not if, a flood exceeds a defence’s capabilities, the lack of preparation will be apparent in the ensuing disaster. Warning systems, which are highly capable of issuing accurate flood alerts, exist – but as in this year’s floods in Germany, these won’t be effective without preparing populations for evacuation.</p>
<p>Rather than constructing dams, the Canadian city of <a href="https://global.oup.com/academic/product/disaster-by-choice-9780198841340?cc=us&lang=en&">Toronto</a> opted to move buildings out of floodplains after <a href="https://en.wikipedia.org/wiki/Effects_of_Hurricane_Hazel_in_Canada">Hurricane Hazel</a> slashed a path through the city in 1954, killing at least 81 people.</p>
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<img alt="A slab with words of memorial" src="https://images.theconversation.com/files/435318/original/file-20211202-20750-1iw87nm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435318/original/file-20211202-20750-1iw87nm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=434&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435318/original/file-20211202-20750-1iw87nm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=434&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435318/original/file-20211202-20750-1iw87nm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=434&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435318/original/file-20211202-20750-1iw87nm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=545&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435318/original/file-20211202-20750-1iw87nm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=545&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435318/original/file-20211202-20750-1iw87nm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=545&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">On a Toronto riverpath stands a memorial to those affected by Hurricane Hazel.</span>
<span class="attribution"><span class="source">Ilan Kelman</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Instead of rebuilding flood-ravaged residential streets, Toronto turned them into nature reserves to keep buildings out and water in. City planners then integrated the reserves into the expanding city by creating walking and cycling pathways alongside them. Now, these have become recreational and commuting routes, environmental education sites and a haven for wildlife.</p>
<p>When Hurricanes Isabel in 2003 and <a href="https://toronto.citynews.ca/topic/hurricane-sandy-hits-toronto/">Sandy</a> in 2012 again transformed Toronto’s watercourses into raging torrents, its floodplains were bare of buildings. Fallen trees littered mud-slicked paths, transportation and power was disrupted. But there was only one fatality. Let’s use this knowledge and wisdom to prepare other towns and cities for handling future floods.</p><img src="https://counter.theconversation.com/content/172902/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 from 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).</span></em></p>Global floods in 2021 showed the danger of poor emergency preparedness - and the importance of planning ahead.Ilan Kelman, Professor of Disasters and Health, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1587692021-04-12T02:39:03Z2021-04-12T02:39:03ZCyclone 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>
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<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>
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<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>
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<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>
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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>
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<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>
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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>
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<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 UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1463182020-09-22T20:05:48Z2020-09-22T20:05:48ZOur new model shows Australia can expect 11 tropical cyclones this season<p>Tropical cyclones are considered one of the most <a href="http://www.ga.gov.au/webtemp/image_cache/GA10821.pdf">devastating weather events in Australia</a>. But they’re erratic — where, when and how many tropical cyclones form each year is <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/wcc.602">highly variable</a>, which makes them difficult to predict.</p>
<p>In our <a href="https://journals.ametsoc.org/jamc/article/doi/10.1175/JAMC-D-20-0131.1">new research</a> published today, we created a statistical model that predicts the number of tropical cyclones up to four months before the start of the tropical cyclone season from November to April. </p>
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Read more:
<a href="https://theconversation.com/storm-warning-a-new-long-range-tropical-cyclone-outlook-is-set-to-reduce-disaster-risk-for-pacific-island-communities-142657">Storm warning: a new long-range tropical cyclone outlook is set to reduce disaster risk for Pacific Island communities</a>
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<p>The model, the <a href="https://tcoutlook.com/australia/">Long-Range Tropical Cyclone Outlook for Australia (TCO-AU)</a>, indicates normal to above normal tropical cyclone activity with 11 cyclones expected in total, Australia-wide. Though not all make landfall. </p>
<p>This is above Australia’s average of <a href="http://www.ga.gov.au/webtemp/image_cache/GA10821.pdf">ten tropical cyclones per season</a>, thanks to a climate phenomenon brewing in the Pacific that brings <a href="https://www.abc.net.au/news/2018-12-14/what-you-need-to-know-about-cyclones/10579026">conditions favourable for tropical cyclone activity</a> closer to Australia. </p>
<h2>La Niña and tropical cyclones</h2>
<p>As we’ve seen most recently with Tropical Storm <a href="https://www.bbc.com/news/world-us-canada-54183485">Sally in the US</a>, tropical cyclones can cause <a href="https://www.tandfonline.com/doi/full/10.1080/17477891.2019.1609406">massive damage</a> over vast areas. This includes extreme and damaging winds, <a href="https://www.abc.net.au/news/2018-02-20/broome-smashes-annual-rainfall-record-after-less-than-two-months/9462962">intense rainfall and flooding</a>, <a href="https://www.abc.net.au/news/2017-01-09/what-is-storm-surge-and-how-can-you-prepare/8123274">storm surges</a>, large waves and <a href="https://www.abc.net.au/news/2020-02-12/tropical-cyclone-uesi-bring-dangerous-conditions-nsw-coast/11955628">coastal erosion</a>. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1306798116763508736"}"></div></p>
<p>Australian tropical cyclone behaviour is largely driven by the <a href="https://theconversation.com/explainer-el-nino-and-la-nina-27719">El Niño-Southern Oscillation (ENSO)</a> — a global <a href="https://www.climate.gov/news-features/featured-images/global-impacts-el-ni%C3%B1o-and-la-ni%C3%B1a">climate phenomenon</a> that changes ocean and atmospheric circulation. </p>
<p>“La Niña” is one phase of ENSO. It’s <a href="https://www.abc.net.au/news/2018-12-14/what-you-need-to-know-about-cyclones/10579026">typically associated with</a> higher than normal tropical cyclone numbers in the Australian region. And the Bureau of Meteorology’s <a href="http://www.bom.gov.au/climate/ahead/about/model/access.shtml">weather and climate model</a> indicates there’s a <a href="http://www.bom.gov.au/climate/model-summary/#tabs=Bureau-model">95% chance a La Niña will be established by October</a> this year. </p>
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Read more:
<a href="https://theconversation.com/explainer-el-nino-and-la-nina-27719">Explainer: El Niño and La Niña</a>
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<p>Around <a href="http://www.ga.gov.au/webtemp/image_cache/GA10821.pdf">ten tropical cyclones</a> occur in the Australian region every season, and about four of those usually make landfall. </p>
<p>Historically, La Niña has resulted in <a href="http://www.bom.gov.au/climate/updates/articles/a020.shtml">double the number of landfalling tropical cyclones</a> in Australia, compared to <a href="http://www.bom.gov.au/climate/about/australian-climate-influences.shtml?bookmark=elnino">El Niño</a> phases. An “El Niño” event is associated with warmer and drier conditions for eastern Australia.</p>
<p>During La Niña events, the first tropical cyclone to make landfall also tends to occur <a href="http://www.bom.gov.au/climate/updates/articles/a020.shtml">earlier in the season</a>. In fact, in Queensland, the only tropical cyclone seasons with multiple severe tropical cyclone landfalls have been <a href="https://link.springer.com/article/10.1007/s00382-010-0883-2">during La Niña events</a>.</p>
<p>Severe <a href="http://www.bom.gov.au/cyclone/history/yasi.shtml">Tropical Cyclone Yasi</a>, one of the most intense tropical cyclones to have hit Queensland, occurred during a La Niña in 2011. So did the infamous Severe <a href="http://www.bom.gov.au/cyclone/history/tracy.shtml">Tropical Cyclone Tracy</a>, which made landfall around Darwin in 1974, <a href="https://knowledge.aidr.org.au/resources/cyclone-cyclone-tracy-darwin/">killing 71 people</a> and leaving more than 80% of all buildings destroyed or damaged. </p>
<p>While naturally occurring climate drivers, such as La Niña, influence the characteristics of tropical cyclone activity, climate change is also expected to cause changes to <a href="https://www.iag.com.au/sites/default/files/Documents/Climate%20action/Severe-weather-in-a-changing-climate-2nd-Edition.pdf">future tropical cyclone risk</a>, including frequency and intensity. </p>
<h2>Australian tropical cyclone outlooks</h2>
<p>Tropical cyclone outlooks provide important information about how many tropical cyclones may pass within the Australian region and subregions, before the start of the cyclone season. Decision-makers, government, industry and people living in tropical cyclone regions use them to prepare for the coming cyclone season. </p>
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Read more:
<a href="https://theconversation.com/ive-always-wondered-how-do-cyclones-get-their-names-116885">I've always wondered: how do cyclones get their names?</a>
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<p>The Australian Bureau of Meteorology has led the way in producing <a href="http://www.bom.gov.au/climate/cyclones/australia/#tabs=Outlook">tropical cyclone outlooks for Australia</a>, usually a couple of weeks before the official start of the tropical cyclone season. </p>
<p>But with monthly guidance up to four months before the start of the season, our new model, <a href="https://tcoutlook.com/australia/">TCO-AU</a>, is unmatched in lead time. It considers the most recent changes in ENSO and other climate drivers to predict how many tropical cyclones may occur in Australia and its sub-regions. </p>
<p>As a statistical model, <a href="https://tcoutlook.com/australia/">TCO-AU</a> is trained on historical relationships between ocean-atmosphere processes and the number of tropical cyclones per season. </p>
<p>For each region, hundreds of potential model combinations are tested, and the one that performs best in predicting historical tropical cyclone counts is selected to make the prediction for the coming season.</p>
<h2>So what can we expect this season?</h2>
<p>September’s TCO-AU guidance suggests <a href="https://tcoutlook.com/australia/latest-outlook/">normal to above normal risk</a> for Australia for the coming tropical cyclone season (November 2020 – April 2021). </p>
<p>With an <a href="http://www.bom.gov.au/climate/enso/index.shtml#tabs=Pacific-Ocean">emerging La Niña</a> and <a href="http://www.bom.gov.au/climate/enso/#tabs=Indian-Ocean&indian=Sea-surface">warmer than normal</a> sea surface temperatures in the eastern Indian Ocean, 11 <a href="https://theconversation.com/ive-always-wondered-how-do-cyclones-get-their-names-116885">tropical cyclones</a> are expected for Australia. There’s a 47% chance of 12 or more cyclones, and a probable range of between nine and 15.</p>
<p>For the Australian sub-regions, TCO-AU suggests the following:</p>
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<li><p><strong>above normal activity</strong> is expected for the <strong>Eastern region</strong> (eastern Australia) with four cyclones expected. Probable range between three and six cyclones; with a 55% chance of four or more cyclones</p></li>
<li><p><strong>normal activity</strong> is expected for the <strong>Western region</strong> (west/northwest Western Australia) with six cyclones expected. Probable range between five and eight cyclones; 39% chance of seven or more cyclones</p></li>
<li><p><strong>below normal activity</strong> is expected for the <strong>Northern region</strong> (northwest Queensland and Northern Territory) with three cyclones expected. Probable range between two and five cyclones; 37% chance of four cyclones or more</p></li>
<li><p><strong>below normal activity</strong> is also expected for the <strong>Northwestern region</strong> (northwest Western Australia) with four cyclones expected. Probable range between three and six cyclones; 45% chance of five cyclones or more.</p></li>
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<span class="attribution"><a class="source" href="https://www.tcoutlook.com">TCO-SP – Long-range Tropical Cyclone Outlook for the Southwest Pacific/The Conversation</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>Guidance from <a href="https://tcoutlook.com/australia/">TCO-AU</a> does not and should not replace advice provided by the Australian Bureau of Meteorology. Instead, it should be used to provide a complementary perspective to regional outlooks and provide a “heads-up” in the months leading up to the start of and within the cyclone season.</p>
<p>Regardless of what’s expected for the coming cyclone season, people living in tropical cyclone regions should always <a href="https://www.abc.net.au/emergency/plan-for-emergency-cyclone/12412044">prepare for the cyclone season</a> and follow the advice provided by emergency services. </p>
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Read more:
<a href="https://theconversation.com/advanced-cyclone-forecasting-is-leading-to-early-action-and-its-saving-thousands-of-lives-139699">Advanced cyclone forecasting is leading to early action – and it's saving thousands of lives</a>
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<img src="https://counter.theconversation.com/content/146318/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Anthony Kiem receives funding from Australian Research Council (ARC). </span></em></p><p class="fine-print"><em><span>Andrew Magee 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>A new statistical model predicts the number of tropical cyclones up to four months before the start of the season from November to April.Andrew Magee, Postdoctoral Researcher, University of NewcastleAnthony Kiem, Associate Professor – Hydroclimatology, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1255792019-10-31T14:46:20Z2019-10-31T14:46:20ZTropical cyclones in the South West Indian Ocean: new insights<figure><img src="https://images.theconversation.com/files/298901/original/file-20191028-114011-1u58m42.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The aftermath of tropical cyclone Idai, which made landfall near Beira, Mozambique earlier this year.</span> <span class="attribution"><span class="source">flickr/ Climate Centre</span></span></figcaption></figure><p>Tropical cyclones – massive storms that can span over 1,000km in diameter – get their energy from the ocean heat. There’s <a href="https://doi.org/10.1175/JCLI-D-16-0737.1">widespread agreement</a> that ocean surface temperatures of at least 26⁰C are required for tropical cyclones to form. </p>
<p>Changes in weather patterns and in the earth’s <a href="https://doi.org/10.1038/ngeo779">climate</a> affect the <a href="https://doi.org/10.5670/oceanog.2018.227">temperature</a> of the sea, in ways that have been extensively <a href="https://doi.org/10.1007/s00382-013-1713-0">researched</a> and <a href="https://doi.org/10.1038/nclimate2646">debated</a>. </p>
<p>As the oceans warm, the locations of where tropical cyclones form and intensify (reach their highest windspeeds) have been <a href="http://dx.doi.org/10.1007/s00382-017-3636-7">shifting</a> over the past 30 years. Their area of occurrence has been moving towards the poles at a rate of about 50 km to 60 km each decade. The warm temperatures needed for tropical cyclones to form are now being found in what used to be cooler ocean regions. </p>
<p>Before the 1980s, southern hemisphere tropical cyclones formed and moved over <a href="http://dx.doi.org/10.4314/wiojms.v8i1.56672">regions between 5° and 20°</a> south of the equator. This tropical region was where ocean waters were warmest.</p>
<p>We conducted <a href="https://www.int-res.com/abstracts/cr/v79/n1/p23-37/">research</a> to find out whether this poleward shift was also present at a smaller spatial scale such as in the South West Indian Ocean, from the East African coastline to 100° east of this.</p>
<p>The <a href="https://doi.org/10.1371/currents.dis.2664354a5571512063ed29d25ffbce74">countries most affected</a> by tropical cyclones in this ocean are the islands of Madagascar, Mauritius and La Reunion. Also affected is Mozambique, which has a coastline, and Zimbabwe, which is landlocked.</p>
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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>
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<p>In future South Africa, which has an extensive eastern coastline and borders on Mozambique as well as Zimbabwe, could also be at risk if the storms begin to occur further south.</p>
<p>Most countries in southern Africa don’t have the resources to adapt to major disasters. This makes it all the more important to try to determine when and where tropical cyclones are more likely to make landfall. </p>
<p>Our research found that it’s possible for storms to affect regions that are considered outside the usual zones of storm activity. Climate variables such as wind fields and sea surface temperature all influence the location and path of storms. </p>
<h2>The research</h2>
<p>The research focused on storms that made their landfall south of the tropic of Capricorn, which is 23.5° south of the equator. This is south of the usual tropical cyclone formation zones. </p>
<p>We used data from the <a href="https://www.ncdc.noaa.gov/ibtracs/">National Ocean and Atmospheric Association</a>. This data tracks the location, maximum windspeed and pressure of these storms every six hours over their lifetime. Over the study period (1960-2015) 29 storms had occurred south of the Tropic of Capricorn. The data allowed us to see the path each one took before it made landfall.</p>
<p>We also looked at sea surface temperatures to capture any impacts warmer oceans were having on the storms.</p>
<p>Our study has confirmed that the Southwest Indian Ocean does experience tropical cyclones outside of the tropics. We were unable to find a statistically significant trend of cyclones moving further south within this discrete dataset. But what the data showed was that there was a cyclical tendency. Some decades (1970-1979 and 1990-2010) experienced storms further south in the South West Indian Ocean than others (1960-1969 and 1980-1989). These abnormally southward occurring storms also increased in intensity over time. Their greater windspeeds made them more dangerous. This phenomenon has also been observed in <a href="https://doi.org/10.1038/ngeo779">global trends</a>. </p>
<p>We also looked at the relationship between different track types (the direction the storm moved in) and variability in the climate, such as the El Niño Southern Oscillation. This variability is defined by changes in normal temperatures, winds and pressure. We found that when El Niño occurred, there was a greater tendency for storms to recurve – that is, change direction by taking a semi-circular route instead of a straight or diagonal line. </p>
<p>We found that recurving tracks also accounted for the majority of the landfalls south of the Tropic of Capricorn. Notable storms are tropical cyclones <a href="https://reliefweb.int/disaster/2004-0103">Gafilo in 2004</a> and <a href="https://www.iol.co.za/news/africa/cyclone-ernest-kills-three-in-madagascar-232531">Ernest in 2005</a>, which hit Madagascar’s southernmost regions.</p>
<p>The large-scale wind fields and the area of ocean warmer than 26°C were shown to influence the storms’ path.</p>
<h2>Going forward</h2>
<p>Our research suggests that countries around the <a href="http://dx.doi.org/10.17159/sajs.2018/4426">South West Indian Ocean</a> need to prepare for the possibility of more tropical cyclones reaching their shores. Being unprepared puts them at greater risk. As the storm locations increase in variability, it becomes more difficult to adapt.</p>
<p>Countries such as <a href="https://doi.org/10.1175/WAF-D-18-0021.1">Japan</a> and the <a href="https://doi.org/10.1007/s00382-018-4446-2">United States</a> continue to improve their short-term forecasts in order to warn people and help them evacuate in time. Southern hemisphere countries need to do the same and start creating plans of action for the future – even if they don’t need them immediately.</p><img src="https://counter.theconversation.com/content/125579/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Micheal Teron received funding from the National Reseach Foundation. </span></em></p><p class="fine-print"><em><span>Jennifer Fitchett receives funding from the DST-NRF Centre of Excellence for Palaeoscience. </span></em></p>As storm directions change, countries that are outside the usual tropical storm zones need to ready themselves.Micheal Pillay, PhD Candidate, climate change science, Nagasaki UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1161782019-04-30T06:52:32Z2019-04-30T06:52:32ZClimate change forced these Fijian communities to move – and with 80 more at risk, here’s what they learned<figure><img src="https://images.theconversation.com/files/271696/original/file-20190430-136787-bz9zdf.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1597%2C898&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Many houses were flattened after Tropical Cyclone Evan, leading to the partial relocation of the Fijian viillage Denimanu. </span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/dfataustralianaid/10690416874/in/photolist-hhFbuj-hhFt3F-hhEVsf-hhFrDs-hhEGBM-hhGUbT-hhFWYu-hhGriC-EkvnGt-EkNy9r-EkNwUc-K3LaWD-FRKhFm-EkwuM8-APRGtv-AtbHxE-22UTqEu-22CfcUa-FRL2Bw-23ZDZsF-23ZDWHT-FRKmFW-FRKpxN-FRJFUC-23WL5rW-EkvKeB-22Cgaaa-EkNu6r-K4451r-22Cfa9R-EkNk6T-22CxG1r-EkwsX6-22VafkQ-23ZWxEz-23ZWz7c-EkNvWk-K4463X-23X4ypf-EkNj4c-22CxGnP-22CxHhe-22CxAfP-22CfxUR-23ZDVBK-22CxEA2-23X4Abb-23ZDNY4-22CxyRM-23ZWjL8">Rowena Harbridge/AusAID</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The original Fijian village of Vunidogoloa is abandoned. Houses, now dilapidated, remain overgrown with vegetation. Remnants of an old seawall built to protect the village is a stark reminder of what climate change can do to a community’s home.</p>
<p>Vunidogoloa is one of four Fijian communities that have been forced to relocate from the effects of climate change. And more than 80 communities have been earmarked by the <a href="https://unfccc.int/resource/docs/natc/fjinc2.pdf">Fiji government</a> for potential future relocation. </p>
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Read more:
<a href="https://theconversation.com/for-pacific-island-nations-rising-sea-levels-are-a-bigger-security-concern-than-rising-chinese-influence-102403">For Pacific Island nations, rising sea levels are a bigger security concern than rising Chinese influence</a>
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<p>Low lying coastal communities like these are especially vulnerable to threats of sea-level rise, inundation of tides, increased intensity of storm surges and coastal erosion. Extreme, sudden weather events such as cyclones can also force communities to move, particularly in the tropics.</p>
<p>But relocating communities involves much more than simply rebuilding houses in a safer location. </p>
<p>It involves providing the right conditions for people to rebuild the lives they knew, such as equitable access to resources and services, social capital and community infrastructure.</p>
<p><a href="https://www.mdpi.com/2076-0760/8/5/133/htm#B55-socsci-08-00133">Our research</a> documents the experiences and outcomes of relocation for two of these Fijian communities – Vunidogoloa and Denimanu.</p>
<h2>The relocated villages</h2>
<p>My colleagues and I visited Vunidogoloa and Denimanu, villages in Fiji’s Northern Islands, at the end of 2017 and spoke to village leaders and community members to learn how they felt about the relocation process.</p>
<p>All 153 residents of Vunidogoloa and roughly half of the 170 people in Denimanu moved away from their climate ravaged homes.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/271401/original/file-20190429-194609-6bjvvi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/271401/original/file-20190429-194609-6bjvvi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=471&fit=crop&dpr=1 600w, https://images.theconversation.com/files/271401/original/file-20190429-194609-6bjvvi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=471&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/271401/original/file-20190429-194609-6bjvvi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=471&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/271401/original/file-20190429-194609-6bjvvi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=592&fit=crop&dpr=1 754w, https://images.theconversation.com/files/271401/original/file-20190429-194609-6bjvvi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=592&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/271401/original/file-20190429-194609-6bjvvi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=592&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Map of Fiji showing the two case study sites.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>Flooding in Vunidogoloa</h2>
<p>Vunidogoloa is a classic example of the slow creep of climate change. For a number of decades the residents have fought coastal flooding, salt-water intrusion and shoreline erosion. The village leaders approached the Fijian government, asking to be relocated to safer ground. </p>
<p>The relocation was originally set for 2012 but, after delays, the entire village moved roughly 1.5 kilometres inland two years later. This is often recognised as the <a href="https://www.aljazeera.com/indepth/features/fiji-villages-move-due-climate-change-180213155519717.html">first ever</a> village in Fiji to relocate from climate change. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/271402/original/file-20190429-194627-102tl4i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/271402/original/file-20190429-194627-102tl4i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/271402/original/file-20190429-194627-102tl4i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=418&fit=crop&dpr=1 600w, https://images.theconversation.com/files/271402/original/file-20190429-194627-102tl4i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=418&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/271402/original/file-20190429-194627-102tl4i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=418&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/271402/original/file-20190429-194627-102tl4i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=525&fit=crop&dpr=1 754w, https://images.theconversation.com/files/271402/original/file-20190429-194627-102tl4i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=525&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/271402/original/file-20190429-194627-102tl4i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=525&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The new village relocation site of Vunidogoloa.</span>
</figcaption>
</figure>
<h2>Cyclone in Denimanu</h2>
<p>In contrast to Vunidogoloa, Denimanu experienced sudden onset effects of climate change. </p>
<p>While the village had been experiencing encroaching shorelines for years, it was <a href="http://coraltriangle.blogs.panda.org/seareefs/yadua-island-and-cyclone-evan">Tropical Cyclone Evan</a>, which hit in 2012 destroying 19 houses closest to the shoreline, that prompted relocation. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/sidelining-god-why-secular-climate-projects-in-the-pacific-islands-are-failing-77623">Sidelining God: why secular climate projects in the Pacific Islands are failing</a>
</strong>
</em>
</p>
<hr>
<p>These homes were rebuilt roughly 500 metres from the original site on a hill slope. With the remaining houses still standing on the original site, the village was only partially moved.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/271403/original/file-20190429-194603-xbu9op.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/271403/original/file-20190429-194603-xbu9op.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/271403/original/file-20190429-194603-xbu9op.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=249&fit=crop&dpr=1 600w, https://images.theconversation.com/files/271403/original/file-20190429-194603-xbu9op.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=249&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/271403/original/file-20190429-194603-xbu9op.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=249&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/271403/original/file-20190429-194603-xbu9op.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=313&fit=crop&dpr=1 754w, https://images.theconversation.com/files/271403/original/file-20190429-194603-xbu9op.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=313&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/271403/original/file-20190429-194603-xbu9op.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=313&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The new village relocation site of Denimanu.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>Was relocation a success?</h2>
<p>The relocation was a success in Vunidogoloa, and residents said they now feel much safer from climate change hazards. One villager told us:</p>
<blockquote>
<p>We were so fearful because of the tides living at the old site. We were happy to move away from that fear. </p>
</blockquote>
<p>But in Denimanu, where the relocated villagers live on a slope, fears of coastal threats have now been replaced by a fear of potential landslides. This is especially concerning as the village’s primary school was <a href="https://www.researchgate.net/figure/The-landslide-that-occurred-behind-Denimanu-in-March-2017-necessitating-the-abandonment_fig3_325241045">recently destroyed</a> by a nearby landslide. </p>
<p>A relocated Denimanu local said: </p>
<blockquote>
<p>We were delighted with the move to the new houses, but we were still worried about the landslide because the houses were on the hill and we know this place.</p>
</blockquote>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/271404/original/file-20190429-194603-17l1e8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/271404/original/file-20190429-194603-17l1e8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/271404/original/file-20190429-194603-17l1e8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/271404/original/file-20190429-194603-17l1e8v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/271404/original/file-20190429-194603-17l1e8v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/271404/original/file-20190429-194603-17l1e8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/271404/original/file-20190429-194603-17l1e8v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/271404/original/file-20190429-194603-17l1e8v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The landslide that destroyed the primary school in Denimanu village.</span>
</figcaption>
</figure>
<p>Ultimately, residents in both villages were happy with many aspects of the relocation process. </p>
<p>For example, they were provided solar power, rainwater tanks, and household facilities that weren’t available in the original villages. Vunidogoloa also received pineapple plants, cattle, and fish ponds, which have helped reestablish their livelihoods. </p>
<p>But it’s not all good news. While new housing was built for the community, they were built to a poor standard, with leaking through the doors and walls, especially in periods of high rainfall. Fiji is located in the tropics, so these infrastructure problems are likely to get worse.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/dont-give-up-on-pacific-island-nations-yet-83300">Don't give up on Pacific Island nations yet</a>
</strong>
</em>
</p>
<hr>
<p>And moving the Vunidogoloa villagers away from the ocean might damage their livelihoods, as fishing is one of their dominant sources of food. The ocean also provides an important spiritual connection for local people.</p>
<p>The impacts of climate change are set to rise, especially if global action to halt greenhouse gas emissions stagnates. More vulnerable communities will need to move away from their current homes. </p>
<p>While relocating communities to safer, less exposed areas is one option to help people manage climate hazards, it’s not a viable solution for all those affected. </p>
<p>Our research shows relocation must be done in a manner that accounts for the rebuilding of local livelihoods, with sustainable adaptation solutions that put local priorities at the centre of this process. </p>
<p>And we need them before more coastal villages are impacted by both slow and sudden onset climate impacts, putting more people in danger.</p><img src="https://counter.theconversation.com/content/116178/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karen Elizabeth McNamara receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Patrick D. Nunn receives funding from the Australian Research Council, the Asia-Pacific Network for Global Change, and the Canadian Social Science and Humanities Research Council.</span></em></p><p class="fine-print"><em><span>Annah Piggott-McKellar 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>Relocating communities to safer, less exposed areas can help people manage climate hazards, but it’s not a viable solution for everyone.Annah Piggott-McKellar, PhD Candidate, The University of QueenslandKaren E McNamara, Senior lecturer, The University of QueenslandPatrick D. Nunn, Professor of Geography, School of Social Sciences, University of the Sunshine CoastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1139312019-03-20T14:11:47Z2019-03-20T14:11:47ZTropical cyclone Idai: The storm that knew no boundaries<figure><img src="https://images.theconversation.com/files/264845/original/file-20190320-93054-1vezzf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">People leaving their homes in the flooded section of Praia Nova, Beira, Mozambique in the wake of tropical cyclone Idai.</span> <span class="attribution"><span class="source">Denis Onyodi/ IFRC handout</span></span></figcaption></figure><p>Tropical cyclone Idai has made <a href="https://www.economist.com/middle-east-and-africa/2019/03/19/tropical-cyclone-idai-may-have-killed-more-than-1000-in-mozambique">headlines</a> across southern Africa throughout the month of March. Lingering in the Mozambique Channel at tropical cyclone intensity for six days, the storm made landfall in Beira, Mozambique in the middle of the month, then tracked in a westerly direction until its dissipation. </p>
<p>The greatest impact of the storm was experienced on landfall. It caused flooding, excessive wind-speed and storm surge damage in the central region of Mozambique. Adjacent countries of <a href="https://theconversation.com/why-malawi-is-failing-to-protect-people-from-floods-and-what-needs-to-be-done-113794">Malawi</a> and <a href="https://www.iol.co.za/news/africa/cycloneidai-death-toll-in-zimbabwe-soars-to-150-about-2000-missing-19974637">Zimbabwe</a> experienced severe rainfall, flooding and damage from the high wind speed. <a href="https://www.accuweather.com/en/weather-news/tropical-storm-likely-to-form-near-madagascar-by-end-of-the-weekend/70007641">Madagascar</a> also experienced bouts of high rainfall during the storm’s pathway to Beira. </p>
<p>The flooding has left hundreds of thousands of people <a href="https://www.afp.com/en/news/717/mozambique-zimbabwe-cyclone-deaths-exceed-300-un-boosts-aid-doc-1er9m712">homeless and displaced</a> across the region while the death toll has continued to rise in the week following landfall. The effects of the cyclone were felt as far south as South Africa and introduced <a href="https://city-press.news24.com/News/eskom-blames-cyclone-idai-for-sas-power-outages-20190317">rolling blackouts</a> due to damaged transmission lines that supply the country with 1100 MW of power from Cahora Bassa in northern Mozambique.</p>
<p>Historically, <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.3932">nine storms</a> that had reached tropical cyclone intensity made landfall on Mozambique. A larger number of weaker tropical systems, including tropical storms and depressions affect the region, with a total landfall of all tropical systems of 1.1 per annum. </p>
<p>The <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.3932">most severe </a>tropical cyclone to make landfall in Mozambique was tropical cyclone Eline in February 2000. It had a category 4 intensity on landfall and resulted in 150 deaths, 1000 casualties from flooding, 300 000 people displaced and four ships sunk.</p>
<p>The storms off Africa’s east coast are weaker than their northern hemisphere counterparts. Category 4 and 5 tropical cyclones make landfall at a near-annual rate in the North Atlantic and North Pacific. </p>
<h2>Why the wide impact</h2>
<p>Why have so many countries been affected?</p>
<p>Tropical cyclones are large storm systems. Immediately surrounding the eye of the storm – a region of calm weather, no wind and no rain – are spirals of storm clouds that span a minimum radius of ~100km. These cloud bands represent the thunder storm conditions, with the rain and winds typical of a tropical cyclone.</p>
<p>A ~100km radius is typical of category 1 tropical cyclones, the lowest intensity ones. As the storms intensify to categories 2, 3, 4 and 5, the <a href="https://journals.ametsoc.org/doi/10.1175/MWR-D-10-05062.1">size</a> increases significantly. This means that a high intensity storm, such as tropical cyclone Idai, has a range of impact significantly larger than the storm track that it follows.</p>
<p>In recent years concerns have been growing about the impact of climate change on cyclones. <a href="https://www.nature.com/articles/nature07234">Research</a> has shown that changes to the world’s temperature, as well as ocean warming, are responsible for an increase in the severity of tropical cyclones. This has recently been <a href="http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532018000600018">researched</a> for the South Indian Ocean. As the ocean is warming, the region which experiences temperatures conducive to tropical cyclone formation is expanding and temperatures in the tropical regions are becoming warm enough for cyclone intensification. Category 5 tropical cyclones, which have been experienced in the North Atlantic for almost a century, started to occur in the South Indian Ocean since 1994, and have occurred increasingly frequently since then.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/rising-sea-temperatures-are-shaping-tropical-storms-in-southern-africa-73139">Rising sea temperatures are shaping tropical storms in southern Africa</a>
</strong>
</em>
</p>
<hr>
<p>This means that as climate change continues and intensifies, so too do these storms. This will mean a greater frequency of not only severe damage from storms, but damage over a larger region. In addition to the impact of warming on the storm intensity, climate warming has also been found to <a href="https://www.nature.com/articles/s41598-017-08533-6">increase the expanse</a> of the storms within any given intensity.</p>
<h2>Cyclone Idai</h2>
<p>So how intense was tropical cyclone Idai? </p>
<p>Storm track records, which include the geographic location of the storm at set time intervals, the wind speed and the atmospheric pressure, are documented by a number of regional climatological organisations. This data is synthesised by the National Oceanographic and Atmospheric Association, providing a useful resource for scientists to explore storm behaviour. </p>
<p>Tropical cyclones are classified on the basis of their wind speed and central pressure. The weakest storms to be classified as tropical cyclones – category 1 – have a minimum sustained wind speed of 119km/hr. At category 3 the storms have a minimum wind speed of 178 km/h. As the category increases, so too does the potential for damage. Category 1 storms are <a href="http://hydromet.gov.bz/tropical-weather/saffir-simpson-scale">classified</a> as resulting in dangerous winds that cause some damage, whereas category 3 storms are expected to cause devastating damage.</p>
<p>The history of tropical cyclone Idai is documented in these records. The cyclone reached <a href="http://www.atms.unca.edu/ibtracs/ibtracs_v04r00/index.php?name=v04r00-2019068S17040#intensity">category 3</a> intensity between 03:00-06:00 on the 11th March 2019, while positioned at its most easterly extent of the storm track. By 03:00 on the 12th March the storm had dissipated to category 2 intensity, and it fluctuated between intensities of categories 2 and 3 over the 36 hours that followed. </p>
<p>From noon on the 13th March the storm maintained a category 3 intensity which persisted until landfall on the 14th.</p>
<h2>What needs to be done</h2>
<p>Storms that affect many countries present particular challenges. They clearly have no regard for political boundaries. The fact that they affect lots of countries presents challenges in both preparing for storm events in a proactive way and responding to prevent loss of life and livelihood. This requires countries to communicate effectively with one another, to provide coherent messages about the forecasting of the storm track and potential damage, and to facilitate effective evacuations. </p>
<p>This storm provides a grim prospect of the future of tropical cyclones in a region under continued threat from climate change. Effective adaptation to minimise storm damage is essential in preparing the region for an increase in the severity of these storms. Disaster risk management plans are also very important to minimise the loss of life.</p><img src="https://counter.theconversation.com/content/113931/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Fitchett receives funding from the DST-NRF Centre of Excellence for Palaeoscience. </span></em></p>The recent storms provide a grim reminder of the prospect of future tropical cyclones in a region under continued threat from climate change.Jennifer Fitchett, Senior Lecturer in Physical Geography, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1101292019-01-22T10:19:05Z2019-01-22T10:19:05Z“Weather” and “climate” are used interchangeably. They shouldn’t be<figure><img src="https://images.theconversation.com/files/254693/original/file-20190121-100292-16ov6qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Heavy snow in Washington, DC, is an example of "weather" - not "climate".</span> <span class="attribution"><span class="source">ERIK S. LESSER/EPA-EFE</span></span></figcaption></figure><p>As January 2019 entered its third week, huge swathes of the US are blanketed with snow, and <a href="https://edition.cnn.com/2019/01/19/us/weekend-winter-storm-wxc/index.html">winter storm warnings</a> were in place across several states. US President Donald Trump, who has made it clear that <a href="https://www.bbc.com/news/world-us-canada-46351940">he believes</a> climate change is an overblown hoax, took to Twitter to suggest that “a little of that good old fashioned Global Warming” would be welcome.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1086971499725160448"}"></div></p>
<p>Trump has fallen into the same trap that many people around the world do: conflating “climate” and “weather”. The US’s current snow storms and cold snap are an example of weather - they will persist for a couple of days to a few weeks at maximum, but will eventually stop and make way for clear skies and inevitably a warm summer for much of the US. </p>
<p>This confusion is common. So, what is the difference between “weather” and “climate”? </p>
<p>At a very simple level, “weather” refers to day-to-day conditions of the atmosphere - the maximum temperature, the amount of cloud cover, the speed and direction of wind and any precipitation that might occur. “Climate” describes the average atmospheric conditions over many years - the average annual rainfall, the predominant wind direction, or the season in which rain is likely to occur. The World Meteorological Organisation <a href="https://library.wmo.int/doc_num.php?explnum_id=4166">states</a> that calculating a “climate” record requires a minimum of 30 years of data.</p>
<p>But does that mean the rain, sun, wind, hot days and cold nights over the last 29 years is just “weather”? Not really.</p>
<p>Clothing provides a useful analogy in understanding this.</p>
<h2>Your weather wardrobe</h2>
<p>Weather, in this analogy, can be considered by the clothes that we choose to wear on a given day. I’m writing from South Africa, where January and February are the peak of summer. At this time of year, South Africans are likely to wear shorts, t-shirts, sundresses, sandals or flip-flops and perhaps a sunhat. We are very unlikely to wear a warm winter coat, boots, a scarf or a beanie today. </p>
<p>However, in South Africa’s wintertime those clothes would be a good choice – paired with warm trousers, a long-sleeved shirt and in mid-July perhaps even some thermals. </p>
<p>If it is a bit cooler tomorrow, with a chance of rain, we may wear closed shoes and a thin jersey. If it is even hotter we may head to the beach or the swimming pool, in which case our clothing choice for the day would involve a swimming costume and towel. So, what we wear changes day-to-day.</p>
<p>Climate, on the other hand, can be understood as the contents of our wardrobe. This consists of a variety of clothing: both that which suits summer weather and those items which are best worn in winter. Our wardrobe, then, represents all the weather conditions one is likely to face throughout the year, for every year that we live in a particular place.</p>
<p>Place is important. The wardrobe of someone living in Johannesburg, South Africa, is very different to the collection of clothes owned by a resident of Helsinki, Finland. South Africans certainly don’t need thermal clothing for sub -20°C temperatures, and Finns have little use for sundresses and shorts (unless, of course, people are heading off on holiday). </p>
<p>The same is true of weather and climate. The conditions experienced at one location necessarily different to those experienced at differing distance to the poles.</p>
<h2>Improved understanding</h2>
<p>What does this knowledge mean for our understanding of climate projections and climate forecasts? </p>
<p>A forecast is what you will see on the televised weather report each night, or on your phone’s weather app. It will tell you the minimum and maximum temperatures likely to occur, and the chance of rainfall. It will also include any alerts for extreme events likely to occur in the next 24 to 72 hours. The weather forecast is helping you choose what to wear.</p>
<p>Climate projections, whether derived from regional and global climate models or from statistical trend analysis of fluctuations over past decades, tell us about the anticipated climate in the next few decades to 100 years. These are letting us know, well in advance, that we may need to think about changing the contents of our wardrobe. We perhaps should invest in fewer thermals and thick coats, and more sundresses and shorts. </p>
<p>We might need to buy a more hardy umbrella or raincoat for more frequent use, or perhaps a water tank for our backyard depending on where we live. But, we do not need to spend the contents of our most recent salary on a whole new wardrobe and throw out everything we have overnight – just slowly, over years to decades, plan and adapt.</p><img src="https://counter.theconversation.com/content/110129/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 Geographer's Centenary Award for Emerging Career Researchers, and funding from the DST-NRF Centre of Excellence for Palaeoscience</span></em></p>At a very simple level, “weather” refers to day-to-day conditions. “Climate” describes the average over many years.Jennifer Fitchett, Senior Lecturer in Physical Geography, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/731392017-02-16T13:43:35Z2017-02-16T13:43:35ZRising sea temperatures are shaping tropical storms in southern Africa<figure><img src="https://images.theconversation.com/files/157095/original/image-20170216-12975-11oytuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some of the destruction in Inhambane, Mozambique after tropical storm Dineo made landfall.</span> <span class="attribution"><span class="source">Steven Clarey/Twitter</span></span></figcaption></figure><p>A tropical storm – named <a href="http://citizen.co.za/news/news-national/1427761/severe-tropical-storm-heading-to-sa-warns-weather-service/">Dineo</a> – has swept in from the Indian Ocean, causing extensive flooding as it hit landfall in Mozambique. More damage is threatened as it swings south and west.</p>
<p>Tropical storms are classified once clouds have reached an organised cyclonic formation and wind speeds <a href="http://www.hko.gov.hk/informtc/class.htm">have exceeded 60km/h</a>. The storm can be upgraded to tropical cyclone status if these exceed 120km/h. Tropical cyclones are classified on the basis of strength and are measured according to the <a href="http://www.nhc.noaa.gov/aboutsshws.php">Saffir Simpson scale</a>. This was <a href="http://novalynx.com/store/pc/Saffir-Interview-d51.htm">developed in 1965</a> by civil engineer Herbert Saffir and climatologist Robert Simpson to classify tropical cyclone damage.</p>
<p>Regions bordering the East, West and South Pacific are influenced by considerably more tropical cyclones each year <a href="http://onlinelibrary.wiley.com/doi/10.1002/joc.3932/epdf">than southern Africa</a>. An average of between five and 15 tropical cyclones make landfall on islands and continents in those regions each year. The southern African sub-continent, meanwhile, experiences one every few years. This is partly because most of the South Indian Ocean tropical cyclones make landfall on Madagascar and never reach <a href="http://onlinelibrary.wiley.com/doi/10.1002/joc.4204/full">the main continent</a>. </p>
<p>Studies over the past half century in southern Africa show that there’s been a southward shift in tropical cyclones in the region, and in particular the location of their landfall. <a href="http://onlinelibrary.wiley.com/doi/10.1002/joc.3932/epdf">One study looked</a> at the records of tropical cyclones in South East Africa going back 66 years. Another investigated 19th century <a href="http://onlinelibrary.wiley.com/doi/10.1002/joc.4204/full">tropical cyclone landfalls in Madagascar</a>. </p>
<p>Tropical storm Dineo provides another piece of evidence of this trend. The question is: what’s behind the shift?</p>
<p>The shift southwards, the position of the storm’s formation, and the later landfall are all because of increasing sea surface temperatures associated with <a href="http://onlinelibrary.wiley.com/doi/10.1002/joc.3932/epdf">global scale warming</a>. Tropical storms require sustained sea surface temperatures that are <a href="http://www.aoml.noaa.gov/hrd/tcfaq/A16.html">higher than 26.5°C</a>. The Indian Ocean’s sea surface temperatures have increased by <a href="http://onlinelibrary.wiley.com/doi/10.1029/2012GL052975/full">0.3°C since 1960</a>, taking them over the tipping point of 26.5°C level sea surface temperatures. This has led to storms forming where it was previously too cold for this to happen.</p>
<h2>Naming conventions</h2>
<p>Why has the storm been called Dineo? A storm of this nature is given a name once it becomes classified as a tropical storm. Tropical storms are named alphabetically for each ocean basin from the beginning of each year from a list of names pre-decided at meetings of the <a href="https://public.wmo.int/en/About-us/FAQs/faqs-tropical-cyclones/tropical-cyclone-naming">World Meteorological Organization</a> with submissions from countries in the region. The names are common first names of people from the region in question. Initially these submissions could only include female names. Male names have also been allowed since 1978. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"831896599198568448"}"></div></p>
<p>The name Dineo was submitted by Botswana. Other names on the alphabetical list were selected from countries including Lesotho and Tanzania. Fourth in the alphabet, Dineo was the fourth storm in the South Indian Ocean that reached tropical storm status. If the list of names is exhausted, Greek letters are used <a href="http://www.nhc.noaa.gov/aboutnames_history.shtml">for subsequent storms</a>. Many named tropical storms and tropical cyclones do not reach the coastlines of islands or continents, and so one doesn’t hear about them in the news.</p>
<p>In 2005, the North Atlantic basin experienced so many tropical storms that experts worried they might have to start with <a href="http://www.livescience.com/9351-hurricane-center-run-names.html">the Greek alphabet</a>.</p>
<h2>Damage, and damage limitation</h2>
<p>Dineo may not reach tropical cyclone status but its effects are still likely to be disastrous. The last tropical storm to make landfall this far south on the continent was <a href="http://link.springer.com/article/10.1007/s11069-015-1691-0">tropical cylone Dando in 2012</a>. Dando caused widespread, prolonged flooding in Mozambique. It also destroyed homes and national infrastructure. Five people were killed and thousands displaced. </p>
<p>The effects were worst along the coastlines, where the storm conditions were paired <a href="http://link.springer.com/article/10.1007/s11069-015-1691-0">with storm surges</a> which resulted in extreme waves crashing onto the shoreline. </p>
<p>In South Africa, the storm resulted in severe flooding in <a href="http://www.tandfonline.com/doi/abs/10.1080/0035919X.2016.1167788">the Limpopo province</a>. Roads and bridges were destroyed, interrupting water and electricity supply, and leaving months of rehabilitation work to be done. </p>
<p>The tourism sector was severely affected, as were many of <a href="http://www.tandfonline.com/doi/abs/10.1080/0035919X.2016.1167788">the region’s</a> other economic centres.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/157093/original/image-20170216-12946-2rzb18.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/157093/original/image-20170216-12946-2rzb18.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/157093/original/image-20170216-12946-2rzb18.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/157093/original/image-20170216-12946-2rzb18.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/157093/original/image-20170216-12946-2rzb18.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/157093/original/image-20170216-12946-2rzb18.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/157093/original/image-20170216-12946-2rzb18.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/157093/original/image-20170216-12946-2rzb18.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tropical cyclone tracks.</span>
<span class="attribution"><span class="source">International Journal of Climatology</span></span>
</figcaption>
</figure>
<p>Tropical storm Dineo has already calmed down. It lost a lot of energy as it made landfall on Mozambique’s coastline, and will continue to weaken as it moves further east. Tropical cyclones and tropical storms gain energy through the evaporation of water over the sea. Without this energy source they quickly downgrade to tropical depression status.</p>
<p>The development of such storms and the destruction they cause shows the need for proactive strategies to mitigate their effect. These should be in place to manage the damage done by extreme winds and flooding. </p>
<p>Strategies to deal with this problem include improved sea barriers to limit the impact of storm surges, improvement of road and bridge infrastructure to withstand storm conditions, and evacuation plans to prevent the loss of human life. But there aren’t many examples of countries taking effective steps to deal with tropical storms.</p><img src="https://counter.theconversation.com/content/73139/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Fitchett 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>In southern Africa there’s been a southward shift in the occurrence of tropical cyclones in the region. This is due to sea temperatures increasing as a result of global warming.Jennifer Fitchett, Lecturer in Physical Geography, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/557302016-03-09T11:13:40Z2016-03-09T11:13:40ZShipwreck records and tree rings unveil Caribbean hurricane history – and clues to the future<figure><img src="https://images.theconversation.com/files/114147/original/image-20160307-31289-d5bb6r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Researchers compared the shipwreck history to tree ring data from slash pines to piece together the hurricane history over past centuries.</span> <span class="attribution"><span class="source">Grant Harley</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The U.S. is currently in a decade-long hurricane “drought”: no major hurricanes of category 3 or higher have made landfall in the U.S. since Hurricane Wilma hit Florida in 2005. With <a href="http://journals.ametsoc.org/doi/abs/10.1175/BAMS-85-5-697">damage costs for U.S. hurricanes</a> from 1970 to 2002 estimated at US$57 billion (in 2015 dollars), this landfall drought is fortuitous for coastal communities and insurance companies alike. </p>
<p>The 10-year hurricane pause is the <a href="http://onlinelibrary.wiley.com/doi/10.1002/2015GL063652/epdf">longest since 1851</a>, the period for which reliable hurricane records are available through the National Hurricane Center’s Hurricane Database <a href="http://www.aoml.noaa.gov/hrd/hurdat/Data_Storm.html">(HURDAT)</a>. The current lull emphasizes how fickle hurricane systems can be, which complicates accurate hurricane predictions under human-caused climate change. </p>
<p><em>Valerie Trouet talked about this research on the <a href="http://academicminute.org/">Academic Minute</a></em>.</p>
<p><audio preload="metadata" controls="controls" data-duration="150" data-image="" data-title="Shipwrecks, Tree Rings and Hurricanes" data-size="2400783" data-source="The Academic Minute for July 21, 2016" data-source-url="http://www.theacademicminute.org" data-license="" data-license-url="">
<source src="https://cdn.theconversation.com/audio/452/07-21-16-arizona-shipwrecks-tree-rings-and-hurricanes.mp3" type="audio/mpeg">
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<div class="audio-player-caption">
Shipwrecks, Tree Rings and Hurricanes.
<span class="attribution"><a class="source" rel="nofollow" href="http://www.theacademicminute.org">The Academic Minute for July 21, 2016</a><span class="download"><span>2.29 MB</span> <a target="_blank" href="https://cdn.theconversation.com/audio/452/07-21-16-arizona-shipwrecks-tree-rings-and-hurricanes.mp3">(download)</a></span></span>
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<p>Is there a way to use the record of past hurricanes to better predict the future?</p>
<p>Climate models for the future <a href="http://www.nature.com/ngeo/journal/v3/n3/abs/ngeo779.html">generally agree</a> that globally, tropical cyclones will become more intense but less frequent in the 21st century. Projections on the regional level, however, vary greatly and have large uncertainties. </p>
<p>For the North Atlantic Basin, the <a href="http://www.nature.com/nclimate/journal/v2/n8/abs/nclimate1530.html">main uncertainties</a> are due to the chaotic nature of the climate system and to our limited understanding of how tropical cyclones – known as hurricanes in the U.S. – respond to changes in how much energy is in the atmosphere. Such changes in the so-called energy budget – the amount of energy that enters the atmosphere and how much is lost to space – can be caused by greenhouse gas emissions, but also by changes in the strength of the sun’s radiation.</p>
<p>In a recently published <a href="http://www.pnas.org/content/early/2016/03/02/1519566113">study</a>, we combined documentary shipwreck data and tree-ring data to extend the tropical cyclone record for the Caribbean back over the last 500 years. These two new proxies and the extended Caribbean tropical cyclone record allow us to look at past big swings in the atmosphere’s energy budget and how tropical cyclones have responded to them. </p>
<p>By providing insight into hurricane dynamics of the past, we aim to give climate scientists better tools for predicting how climate change will affect hurricane intensity and frequency with more regional accuracy.</p>
<h2>Poring over shipwreck records and tree rings</h2>
<p>All three of us are tree-ring scientists. We use the rings in trees and wood to study the climate, the forests and human societies of the past. All three of us remember exactly the moment and the place when the idea for this research project emerged: it was on the last night of the second <a href="https://ameridendro.ltrr.arizona.edu/conferenceDisplay.py?confId=0">Ameridendro</a> conference, held in Tucson, Arizona, in May 2013, and we were sharing conversation and a beer on the patio of <a href="http://hotelcongress.com/">Hotel Congress</a>. </p>
<p>Grant mentioned a set of tree-ring samples that he collected from approximately 250-year old slash pine trees on the Florida Keys.</p>
<p>When hurricanes pass near to the Keys, strong winds and storm surges cause these pines to grow less and to form narrow growth rings. The pine trees are intolerant of salt (storm surge), and strong winds cause branches and needles to break off trees, which results in narrow growth rings for a few years after a storm.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/114150/original/image-20160307-31272-5kt8ol.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/114150/original/image-20160307-31272-5kt8ol.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=209&fit=crop&dpr=1 600w, https://images.theconversation.com/files/114150/original/image-20160307-31272-5kt8ol.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=209&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/114150/original/image-20160307-31272-5kt8ol.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=209&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/114150/original/image-20160307-31272-5kt8ol.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=262&fit=crop&dpr=1 754w, https://images.theconversation.com/files/114150/original/image-20160307-31272-5kt8ol.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=262&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/114150/original/image-20160307-31272-5kt8ol.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=262&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">South Florida slash pine section from Big Pine Key, Florida Keys, U.S. Growth of the tree is from right to left. ‘Bands’ of narrow growth years can be detected throughout the section and represent the growth suppression caused by hurricane disturbance (strong winds, storm surge).</span>
<span class="attribution"><span class="source">Grant Harley</span></span>
</figcaption>
</figure>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/114162/original/image-20160307-31289-7j63d3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/114162/original/image-20160307-31289-7j63d3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=902&fit=crop&dpr=1 600w, https://images.theconversation.com/files/114162/original/image-20160307-31289-7j63d3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=902&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/114162/original/image-20160307-31289-7j63d3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=902&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/114162/original/image-20160307-31289-7j63d3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1134&fit=crop&dpr=1 754w, https://images.theconversation.com/files/114162/original/image-20160307-31289-7j63d3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1134&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/114162/original/image-20160307-31289-7j63d3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1134&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Old, remnant stumps and logs from South Florida slash pines were cut with chainsaws to extend the hurricane suppression chronology back to the early 1700s, Big Pine Key, Florida Keys, U.S.</span>
<span class="attribution"><span class="source">Grant Harley, John Sakulich</span></span>
</figcaption>
</figure>
<p>Marta told us stories of the <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1095-9270.2012.00361.x/abstract?userIsAuthenticated=false&deniedAccessCustomisedMessage=">dendro-archeological work </a> she’s done on shipwrecks: by tree-ring dating the wood recovered from shipwrecks, information can be inferred about the provenance of the wood, timber procurement for shipbuilding, past forest management practices, and woodworking techniques. She also mentioned a shipwreck database that contained comprehensive information about the when, where and why of past shipwrecks.</p>
<p>All three of us remember the exact moment, because our minds collided and an exhilarating idea arose: could we combine the shipwreck record with the Florida Keys tree-ring record to recreate past tropical cyclone activity?</p>
<p>The first thing we did was to filter the shipwreck database, narrowing in on the Spaniards since they were the first to make the transatlantic voyage in 1492 and thus provided the longest available shipwreck record. We extracted data on Spanish ships that wrecked in the Caribbean during the hurricane season from July through November. We recorded only shipwrecks that were documented to be caused by storms or by unknown causes, not by wars, pirates, fires or poor navigation. </p>
<p>This resulted in a 330-year (from 1495 to 1825) record that showed how many of the 657 Spanish shipwrecks occurred each year. When we compared this shipwreck record to the Florida Keys tree-ring record, we found an astonishing result that allowed us to reconstruct the cyclone record of past centuries.</p>
<p>From Grant’s work, we knew that the Florida Keys trees responded to tropical cyclones since 1851 with bands of narrow rings. </p>
<p>When comparing the two sets of data – the tree-ring and shipwreck records – we discovered that the trees had these narrow rings during years when many ships wrecked in the Caribbean. We thus discovered a way to reconstruct Caribbean tropical cyclones back to 1495.</p>
<h2>A 60-year lull in Caribbean tropical cyclones</h2>
<p>Our next discovery jumped out at us when we plotted the combined data over time of the shipwreck and the tree-ring records. We noticed a very distinct low in the number of shipwrecks from 1645 to 1715, a period known to paleoclimatologists as the <a href="http://solarscience.msfc.nasa.gov/SunspotCycle.shtml">Maunder Minimum</a>. </p>
<p>Sunspot activity – and thus solar irradiance, or the amount of solar energy that reached the Earth – during the Maunder Minimum was at its lowest over documented history, resulting in a period of cool temperatures in the Northern Hemisphere. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/114148/original/image-20160307-31272-7akct4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/114148/original/image-20160307-31272-7akct4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=373&fit=crop&dpr=1 600w, https://images.theconversation.com/files/114148/original/image-20160307-31272-7akct4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=373&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/114148/original/image-20160307-31272-7akct4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=373&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/114148/original/image-20160307-31272-7akct4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=469&fit=crop&dpr=1 754w, https://images.theconversation.com/files/114148/original/image-20160307-31272-7akct4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=469&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/114148/original/image-20160307-31272-7akct4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=469&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Reduced Caribbean tropical cyclone activity during the Maunder Minimum. a) Decadal-scale shipwreck and instrumental (HURDAT) time series sums and tree-growth suppression averages; b) number of years per decade with more than 1 or 4 shipwrecks; c) spectral solar irradiance (Lean, 2000).</span>
</figcaption>
</figure>
<p>By using shipwreck rates as a proxy for past tropical cyclone activity – something that has not been done before – we found that the cool temperatures of the Maunder Minimum coincided with a tropical cyclone drought. But why?</p>
<p>The mechanism that explains the link between the lull in shipwrecks, tropical cyclones and sunspots during the Maunder Minimum involves sea surface temperatures. With cool global temperatures come cool sea surface temperatures. <a href="http://www.nature.com/nature/journal/v436/n7051/abs/nature03906.html">Sea surface temperatures</a> are an important driver of tropical cyclones. We know from 20th-century data that with cooler sea surface temperatures, there are fewer tropical cyclones. In short: cooler sea surface temperatures during the Maunder Minimum (due to less solar irradiance) resulted in fewer tropical cyclones and fewer shipwrecks.</p>
<p>We also found that global climate dynamical patterns, such as the El Nino-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO), likely converged during the Maunder Minimum to enhance the link between the lows in solar irradiance and in tropical cyclones.</p>
<p><a href="http://science.sciencemag.org/content/293/5529/474.short">We know from 20th-century data</a> that these climate patterns play an important role in Caribbean tropical cyclones, with fewer cyclones occurring during positive “El Niño” phases and negative NAO phases. For instance, the continued hurricane drought in 2015 has been attributed to this year’s strong El Niño. </p>
<h2>Caribbean tropical cyclones under a warming future</h2>
<p>Our study provides information on how Caribbean tropical cyclones respond on decadal time scales to changes in the atmosphere’s energy budget. </p>
<p>When looking at model projections for the 21st century, these decadal time scales are of crucial importance. Most of the <a href="http://www.nature.com/nclimate/journal/v2/n8/abs/nclimate1530.html">uncertainty in the model projections</a> for the Caribbean Basin comes from our lack of understanding of how Caribbean hurricane activity responds to changes in the amount of energy in the atmosphere. Our historical record helps us improve that understanding and thus the model projections.</p>
<p>We know that with more densely populated coastal areas, sea level rise and stronger storm surges, 21st-century tropical cyclones will become increasingly destructive and costly. Our continued improvement of understanding how frequent and/or intense future tropical cyclones will be is of the utmost importance, especially with regard to the safety and livelihoods of coastal communities.</p><img src="https://counter.theconversation.com/content/55730/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Valerie Trouet receives funding from the National Science Foundation and the Department of Energy. </span></em></p><p class="fine-print"><em><span>Grant Harley receives funding from the Bureau of Ocean Energy Management.</span></em></p><p class="fine-print"><em><span>Marta Domínguez Delmás receives funding from the European Marie Skodolwska Curie Innovative Training Networks program in the frame of the ForSEAdiscovery project (PITN-2013-GA-607545). For this research, she also received funding from an Agnese N. Haury Visiting Fellowship of the University of Arizona.
Other affiliations include academic affiliation to the University of Huelva, department of History I (Spain)</span></em></p>In an attempt to better understand hurricanes, researchers recreate hundreds of years of hurricane records with Spanish shipwreck logs and tree ring data.Valerie Trouet, Associate Professor of Dendrochronology, University of ArizonaGrant Harley, Assistant Professor of Geography, The University of Southern MississippiMarta Domínguez Delmás, Research Fellow Dendrochronologist, Universidade de Santiago de CompostelaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/378352015-02-20T05:40:23Z2015-02-20T05:40:23ZThe role of social media as cyclones batter Australia<p>The heavy rains and strong winds battering parts of Australia as Tropical Cyclones Marcia and Lam unleash their power are causing a rush of comments on social media.</p>
<p>As I write this article I’m sitting in the Queensland Fire and Emergency Services headquarters, in Brisbane, as part of my PhD research. I’m able to see first-hand the role that social media can play during natural disaster events.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"568566479899271168"}"></div></p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"568578482201997312"}"></div></p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"568568422193352705"}"></div></p>
<p>More specifically, I’m observing how emergency management and other organisations can use various social media platforms to release timely and relevant information to those who need it.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"568563759599337472"}"></div></p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"568551374801260544"}"></div></p>
<p>These organisations can also use social media to gather intelligence from these platforms via geo-mapped Tweets and Instagram posts and, if necessary, respond to comments from people. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/72569/original/image-20150220-28204-9b0zbo.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/72569/original/image-20150220-28204-9b0zbo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/72569/original/image-20150220-28204-9b0zbo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=285&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72569/original/image-20150220-28204-9b0zbo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=285&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72569/original/image-20150220-28204-9b0zbo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=285&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72569/original/image-20150220-28204-9b0zbo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=359&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72569/original/image-20150220-28204-9b0zbo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=359&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72569/original/image-20150220-28204-9b0zbo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=359&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="source" href="https://www.facebook.com/QldFireandRescueService/posts/792220270858535">QFES Facebook page</a></span>
</figcaption>
</figure>
<p>During recent natural disasters, social media have played an increasingly popular role in the crisis communication ecology. <a href="http://eprints.qut.edu.au/50739/">Research has shown</a> how affected members of the public use these platforms to share up-to-date information and images on their status with friends and family.</p>
<p>TC Marcia is already impacting towns along the coast of central Queensland, including Yeppoon, Rockhampton and Gladstone today. TC Marcia is expected to bring extensive rainfall and possible flooding to the southeast corner of Queensland and as far south as northern New South Wales over the weekend.</p>
<p>On Twitter, key trending topics and hashtags include <a href="https://twitter.com/search?q=%23TCMarcia">#TCMarcia</a> and derivatives of the term (<a href="https://twitter.com/search?q=%23cyclonemarcia">#cyclonemarcia</a>, <a href="https://twitter.com/search?q=%23bigwet">#bigwet</a>). Key terms and locations relating to the event include things such as “Category 5” and “St Lawrence”.</p>
<p>In the Northern Territory the hashtag <a href="https://twitter.com/search?q=%23TClam">#TCLam</a> is trending as TC Lam moves across the region.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"568579585396375552"}"></div></p>
<p>Social media posts are useful at various stages of a disaster. In the past few days we’ve seen extensive activity from local councils on their Facebook pages. We’ve also seen activity from key disaster response agencies, including the <a href="https://www.facebook.com/QldFireandRescueService">Queensland Fire and Emergency Services</a> and the <a href="https://www.facebook.com/QueenslandPolice">Queensland Police Service</a> in preparation for the cyclone.</p>
<p>But how these agencies respond to the event using social media while it is happening and afterwards, in the recovery phase, is particularly interesting. Social media can help communities organise recovery efforts and make it easier for agencies to conduct their role.</p>
<p>People are even encouraged – only when it is safe to do so – to post photos of any cyclone damage on Twitter, including <a href="https://twitter.com/@QldFES">@QldFES</a> in the Tweet, to make it easier for emergency services to monitor. The acting commissioner of Queensland Fire and Emergency Services, Katarina Carroll, told Channel Nine that was a big help:</p>
<blockquote>
<p>It gives us a true picture of what’s happening out there so we encourage people to definitely do that. We use our own internal social media to do that and our own way of getting imagery back into the centre, but certainly it gives us a fuller and more comprehensive picture of what’s occurring out there.</p>
</blockquote>
<h2>The push and pull of information</h2>
<p>Researchers and owners and operators of social media platforms are quickly responding to the growing use of social media during natural disasters and unusual events, developing tools to more effectively push and pull information from these platforms.</p>
<p>Towards the end of last year, we wrote about the role that <a href="https://theconversation.com/is-social-media-responsible-for-your-safety-during-a-disaster-33138">social media platform owners</a> and operators play in a natural disaster. Facebook’s new platform <a href="http://newsroom.fb.com/news/2014/10/introducing-safety-check/">Safety Check</a> allows users to notify their network of their safety status during a natural disaster.</p>
<p>While this platform is of particular use to affected individuals, its benefit to disaster response agencies is, for the moment, unknown. It was <a href="http://recode.net/2014/10/15/facebook-adds-emergency-check-in-feature-for-natural-disasters/">not developed in consultation</a> with emergency management organisations, which means the data is likely inaccessible to these agencies.</p>
<p>In contrast, the launch of <a href="https://blog.twitter.com/2013/introducing-twitter-alerts">Twitter Alerts</a> in September 2013 opened up new possibilities to increase the visibility of emergency management organisations’ important messages to their followers.</p>
<p>Twitter alerts allow pre-approved law enforcement (such as the Queensland Police service, below), emergency management and government agencies to send critical information – such as warnings, evacuation instructions and safety messages – to their subscribers via a push notification or an SMS message (for those who subscribe to the latter service).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/72581/original/image-20150220-28191-160iex6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/72581/original/image-20150220-28191-160iex6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/72581/original/image-20150220-28191-160iex6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=327&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72581/original/image-20150220-28191-160iex6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=327&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72581/original/image-20150220-28191-160iex6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=327&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72581/original/image-20150220-28191-160iex6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=411&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72581/original/image-20150220-28191-160iex6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=411&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72581/original/image-20150220-28191-160iex6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=411&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">QPS Twitter Alerts.</span>
<span class="attribution"><a class="source" href="https://twitter.com/qpsmedia/alerts">Twitter/Queensland Police Service</a></span>
</figcaption>
</figure>
<p>When the service first launched <a href="https://www.qut.edu.au/about/news/news?news-id=70275">I outlined</a> some considerations for agencies wanting to use it and particular limitations of the service.</p>
<p>We’re yet to see extensive use of Twitter alerts, particularly here in Australia. However, the Queensland Police Service did release its first Twitter alert earlier this month after the service had cancelled a child abduction alert (CAA) for a child who was previously reported as missing.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"564726247775678464"}"></div></p>
<p>It’s worth noting, though, that this alert was issued to notify followers that the missing child had been located (likely to prevent the further spread of the child abduction alert), rather than when the CAA was first released.</p>
<p>It’s this type of self-directed use that makes services such as Twitter alerts, while interesting, potentially problematic. There is the possibility of inconsistent use across all users.</p>
<p>In the case of disasters, one agency may release a Twitter alert only for life-threatening events, while another agency may issue them frequently for all warnings, potentially lessening the impact of this service for some recipients.</p>
<h2>Is social media revolutionising crisis communication?</h2>
<p>There will likewise always be concerns about the spread of <a href="https://theconversation.com/how-rumours-about-the-sydney-siege-spread-on-social-media-35536">rumour and misinformation on social media</a> during an event. There are also risks for a select few who post on social media when in danger rather than call emergency services on 000.</p>
<p>Of course, any posting device’s need for power and an internet signal or network connection to get information out on social media is always a challenge, especially during severe weather events where power and network outages are common. </p>
<p>So it’s important to note that proponents of social media don’t consider it a replacement for traditional forms of communication, particularly those located in remote or isolated communities.</p>
<p>Rather, it is a useful addition to a crisis communication toolbox, which opens up possibilities for communicating in new and innovative ways. It offers potential for disaster response agencies to receive live, on-the-ground intelligence from those directly affected.</p>
<p>But users shouldn’t rely on social media as their only information source. At the end of the day, if all else fails, there’s always the trusty battery-powered radio.</p>
<hr>
<p><strong>Useful information</strong></p>
<p>For Tropical Cyclone Maria follow <a href="https://twitter.com/@QldFES">@QldFES</a>, <a href="https://twitter.com/@QPSmedia">@QPSmedia</a> and <a href="https://twitter.com/@BOM_Qld">@BOM_Qld</a> and the hashtag <a href="https://twitter.com/search?q=%23TCMarcia">#TCMarcia</a> on Twitter.</p>
<p>Sign up to receive Twitter alerts from <a href="https://twitter.com/QPSmedia/alerts">Queensland Police</a> and <a href="https://twitter.com/QldFES/alerts">Queensland Fire and Emergency Services</a>.</p>
<p>For Tropical Cyclone Lam follow <a href="https://twitter.com/@ntpolice">@ntpolice</a>, <a href="https://twitter.com/@BOM_NT">@BOM_NT</a> and the hashtag <a href="https://twitter.com/search?q=%23TClam">#TCLam</a> on Twitter.</p>
<p>If you’re in the affected area and require assistance call the SES on 132 500.</p>
<p>In a life-threatening emergency always call Triple Zero (000).</p><img src="https://counter.theconversation.com/content/37835/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emma Potter receives funding from the Australian Research Council. As part of her PhD research she is embedded with the Queensland Fire and Emergency Services, observing and participating in their use of social media.</span></em></p>Emergency services are using social media to help spread warnings as two tropical cyclones batter Australia. It can also help them with relief efforts once the worst of the severe weather has passed.Emma Potter-Hay, PhD Candidate, Queensland University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/255502014-04-14T04:40:06Z2014-04-14T04:40:06ZHow building codes save homes from cyclones, and how they don’t<figure><img src="https://images.theconversation.com/files/46317/original/v832dymw-1397445068.jpg?ixlib=rb-1.1.0&rect=32%2C16%2C2087%2C1344&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A Cooktown home which lost its roof to Cyclone Ita, although damage was less widespread than feared.</span> <span class="attribution"><span class="source">AAP Image/Dan Peled</span></span></figcaption></figure><p>During Queensland’s preparations for Severe Tropical Cyclone Ita, <a href="http://www.abc.net.au/7.30/content/2014/s3983077.htm">Queensland Premier Campbell Newman</a> advised residents who lived in older houses (those built before 1985) to evacuate their homes as they were not likely to stand up to the storm’s destructive winds.</p>
<p>In the event, the damage was <a href="http://www.brisbanetimes.com.au/queensland/cyclone-ita-worsthit-areas-could-go-weeks-without-power-20140414-36m7d.html">largely to the electricity network</a>, while Cooktown, very close to the path of the storm, <a href="http://www.smh.com.au/environment/weather/cooktown-cleans-up-after-cyclone-ita-20140412-36jzz.html">suffered less destruction than had been feared</a>.</p>
<p>But the episode still begs the question: what was so special about 1985? </p>
<p>That was the year that building regulations changed to require new houses in cyclone-prone areas to be able to withstand higher winds. But how were these regulations determined, what do they mean for modern homes, and why do regulators always seem to wait until after a severe storm before updating the codes?</p>
<h2>Updating the regulations</h2>
<p>Building codes are drawn up by the <a href="http://www.abcb.gov.au/">Australian Building Codes Board (ABCB)</a>, which cites its mission as addressing “issues of safety and health, amenity and sustainability”. </p>
<p>Its job is to set <em>minimum standards</em> for the design, construction and performance of buildings to “withstand extreme climate related natural hazard events”. It is then up to each state and territory to adopt the recommended standards.</p>
<p>After natural disasters, the ABCB examines the nature of building damage to decide whether the regulations provide enough protection. During <a href="http://www.bom.gov.au/cyclone/history/tracy.shtml">Cyclone Tracy</a> in 1974, 70% of Darwin’s houses suffered severe damage (90% in some areas), causing 65 deaths and damage worth hundreds of millions of dollars. It was obvious that existing building standards were not protecting the community.</p>
<p>As a result, the regulations were changed in the 1980s to improve the construction processes that attach the roof to the rest of the house, making homes more resistant to severe wind damage.</p>
<p>Analysis after cyclones <a href="http://www.bom.gov.au/cyclone/history/vance.shtml">Vance</a> (1999), <a href="http://www.bom.gov.au/cyclone/history/larry.shtml">Larry</a> (2006) and <a href="http://www.bom.gov.au/cyclone/history/yasi.shtml">Yasi</a> (2011) showed that the updated regulations have resulted in <a href="http://www.abcb.gov.au/en/education-events-resources/national-conference/%7E/media/Files/Download%20Documents/Marketing%20Docs/BAF/4%20David%20Henderson%20FINAL.ashx">much less building damage and consequent loss of life</a>. During Cyclone Yasi, for example, 12% of older homes suffered severe roof damage, but only 3% of newer homes.</p>
<p>Of course, this does not mean that newer homes are completely impregnable. <a href="https://www.jcu.edu.au/cts/publications/content/technical-reports/jcu-078421.pdf/view">Analysis of damage from Cyclone Yasi</a> showed some remaining “weak points”: tiled roofs, sheds, garage doors, and doors/windows. It was found that more attention needs to be paid to the design, testing, installation, use and maintenance of products, components and fixings. Revised standards have since been developed for roof tiles, garage doors and shed design. </p>
<h2>The right way to think about risk</h2>
<p>Campbell Newman’s comment about older houses was partially correct – houses built to older standards were indeed more likely to suffer damage. But his statement is perhaps also misleading. Current building standards for Far North Queensland are designed to protect structural integrity in winds up to a Category 4 cyclone. If Ita had crossed the coast and maintained its Category 5 intensity, it is possible that all of Cooktown’s houses – old and new – would have been subject to severe damage.</p>
<p>It is crucial that the community understands what hazards and risks are being addressed by building regulations, and which ones are not.</p>
<p>For example, current regulations address wind loading associated with cyclones, but take no consideration of wind-driven rain (a major cause of water damage). There are also three specific hazards that are not addressed: hail, storm surges and heatwaves. The first two present risks to property; the third contributes to heat stress, which is in turn linked to health problems and deaths.</p>
<p>When deciding whether and how to update the regulations, the ABCB considers both costs and benefits. Regulations will only change if the ABCB and its stakeholders determine that the cost of the changes (such as higher building costs) are less than the benefits (the expected savings in reduced damage). </p>
<p>As a result, the regulations establish <em>minimum</em> standards, not <em>best practice</em> standards.</p>
<h2>The community’s role</h2>
<p>Home owners and residents therefore need to be aware of these limitations in the building regulations, and be much more proactive in determining what level of risk is appropriate to their circumstances. A simple risk assessment identifies three things:</p>
<ol>
<li><p>What hazards and risks might your house/unit/building be exposed to?</p></li>
<li><p>What is the likelihood and frequency of those hazards?</p></li>
<li><p>What are the consequences if the event happens?</p></li>
</ol>
<p>Property damage is perhaps the first risk that people consider, particularly in relation to natural hazards such as cyclones, floods and bushfires. But buildings and their contents can also be damaged by heavy rain, hail, tidal surges, ground movement, and other phenomena.</p>
<p>There are also financial risks associated with not taking action, such as increased power prices and insurance premiums. These financial risks affect everyone in the community.</p>
<p>Meanwhile, people who are directly affected by property loss can also suffer resettlement costs and loss of income.</p>
<h2>What should you do?</h2>
<p>Listening to the authorities is important, but you should take responsibility for your own household risks too. One way to do it is to take out <a href="http://understandinsurance.com.au/">home insurance</a>, but you need to be aware of what risks your insurance does and does not cover, and what are your responsibilities.</p>
<p>Another way to manage your risk is to take these things into consideration when you are building, buying or renting a property. Find out how a building has been designed and constructed to manage these risks. Ask the architect, designer, builder, estate agent, landlord, body corporate or local council for documentary evidence.</p>
<p>The insurance sector could also play a more proactive role in promoting better building design, perhaps by offering lower premiums for buildings with stronger construction.</p>
<p>Consideration also needs to be given to changing the way damaged buildings are evaluated and repaired after a disaster. New Zealand has acknowledged that the <a href="http://cera.govt.nz/sites/cera.govt.nz/files/common/recovery-strategy-for-greater-christchurch.pdf">earthquake recovery process</a> provides an opportunity for creating a more resilient city, not just restoring what was lost.</p>
<p>What is needed is a more collaborative approach to withstanding risks to our buildings, our property, and even our health. The ABCB seems to be <a href="http://www.abcb.gov.au/%7E/media/Files/Download%20Documents/Major%20Initiatives/Draft%20ABCB%20Discussion%20Paper%20on%20Resilience%20to%20Extreme%20Weather%20Events.pdf">moving in this direction</a>, and it should not be expected to go it alone. </p>
<p>We all have a role to play in creating robust and resilient neighbourhoods that stand up to natural hazards. </p><img src="https://counter.theconversation.com/content/25550/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wendy Miller receives / has received funding from the Australian Research Council and the National Climate Change Adaptation Fund.
She is being sponsored by ICPS Australia to present her research findings at the Australian and New Zealand Disaster and Emergency Management Conference on the Gold Coast in May.</span></em></p>During Queensland’s preparations for Severe Tropical Cyclone Ita, Queensland Premier Campbell Newman advised residents who lived in older houses (those built before 1985) to evacuate their homes as they…Wendy Miller, Senior Research Fellow, Queensland University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/208142014-01-29T19:49:08Z2014-01-29T19:49:08ZTropical cyclone frequency falls to centuries-low in Australia – but will the lull last?<figure><img src="https://images.theconversation.com/files/40056/original/5792tjh9-1390953708.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Damaged boats smashed together at Port Hinchinbrook harbour, the day after category 5 tropical cyclone Yasi hit north Queensland. </span> <span class="attribution"><span class="source">AAP/Dave Hunt</span></span></figcaption></figure><p>The number of <a href="http://www.bom.gov.au/cyclone/about/">tropical cyclones</a> hitting Queensland and Western Australia has fallen to low levels not seen for more than 500 years, new research published in <a href="http://dx.doi.org/10.1038/nature12882">Nature</a> shows.</p>
<p>But while that’s seemingly great news for people in <a href="http://www.abc.net.au/news/topic/cyclone">cyclone-prone areas</a>, our new research into Australia’s past cyclone records also highlights a serious risk. </p>
<p>Low-lying coastal areas such as Cairns, Townsville and Mackay in north Queensland have all been developed on the unproven assumption that the cyclone activity of the past 40 years will continue unchanged into the future. </p>
<p>The concern is that our new results closely matched several recent studies that have projected <em>fewer</em> – but increasingly <em>intense</em> – tropical cyclones for Australian region due to global climate change.</p>
<p>And if those projections prove to be right, we are taking a big gamble with existing homes, roads and offices, as well as threatening proposed developments such as the <a href="http://www.abc.net.au/news/2013-08-02/green-light-for-first-stage-of-42b-cairns-casino-resort/4860456">A$4.2 billion resort casino</a> planned for low-lying coastal land near Cairns.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/39972/original/5xvqhvrm-1390880853.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/39972/original/5xvqhvrm-1390880853.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/39972/original/5xvqhvrm-1390880853.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=783&fit=crop&dpr=1 600w, https://images.theconversation.com/files/39972/original/5xvqhvrm-1390880853.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=783&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/39972/original/5xvqhvrm-1390880853.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=783&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/39972/original/5xvqhvrm-1390880853.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=984&fit=crop&dpr=1 754w, https://images.theconversation.com/files/39972/original/5xvqhvrm-1390880853.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=984&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/39972/original/5xvqhvrm-1390880853.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=984&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 Yasi hit north Queensland with devastating force in February 2011.</span>
<span class="attribution"><span class="source">NASA Goddard MODIS Rapid Response Team</span></span>
</figcaption>
</figure>
<p>There is no such thing as a risk-free development, especially when building in cyclone-prone regions. However, being properly informed and cautious about developments in such regions is in all Australians’ interests - because if we get it wrong, we all stand to pay through higher insurance premiums and largely taxpayer-funded disaster clean-ups.</p>
<h2>Limestone cave time machines</h2>
<p>Our <a href="http://dx.doi.org/10.1038/nature12882">study</a> shows that current seasonal cyclone activity is at its lowest level in Western Australia since 500 AD and since about 1400 AD in Queensland. That decline began about 40 years ago.</p>
<p>While Australia’s official cyclone records only date back to 1906, we can track cyclones further back in time using measurements of isotopes housed within limestone cave stalagmites. Those stalagmites grow upwards from the cave floor as rainwater containing dissolved limestone drips from the cave ceiling. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/40051/original/z5g2mg8s-1390952233.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/40051/original/z5g2mg8s-1390952233.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/40051/original/z5g2mg8s-1390952233.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/40051/original/z5g2mg8s-1390952233.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/40051/original/z5g2mg8s-1390952233.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/40051/original/z5g2mg8s-1390952233.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/40051/original/z5g2mg8s-1390952233.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/40051/original/z5g2mg8s-1390952233.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">Examining stalagmites in a cave in Cape Range, Western Australia.</span>
<span class="attribution"><span class="source">Jon Nott</span></span>
</figcaption>
</figure>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/40047/original/88hcwbf9-1390950642.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/40047/original/88hcwbf9-1390950642.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/40047/original/88hcwbf9-1390950642.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1641&fit=crop&dpr=1 600w, https://images.theconversation.com/files/40047/original/88hcwbf9-1390950642.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1641&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/40047/original/88hcwbf9-1390950642.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1641&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/40047/original/88hcwbf9-1390950642.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=2062&fit=crop&dpr=1 754w, https://images.theconversation.com/files/40047/original/88hcwbf9-1390950642.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=2062&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/40047/original/88hcwbf9-1390950642.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=2062&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 close up of a section of 2,000-year-old stalagmite from a cave in Chillagoe, Queensland. Layers of calcium carbonate are laid down in the wet and dry season each year, and scientists can detect tropical cyclones in these layers from very depleted levels of oxygen-18.</span>
<span class="attribution"><span class="source">Jon Nott</span></span>
</figcaption>
</figure>
<p>The isotope chemistry of tropical cyclone rainwater differs from that of monsoonal and thunderstorm rainwater. As a consequence, it is possible to analyse the chemistry of each of the stalagmite layers, which are approximately 1/10th of a millimetre thick, and generate a record of cyclones over the past 1500 to 2000 years.</p>
<p>My colleague Jordahna Haig then matched the isotope records with the Bureau of Meteorology’s cyclone record over the past 40 years and generated a Cyclone Activity Index, which plots the seasonal activity of cyclones over the past 1500 years. </p>
<p>In the short term, the recent decline in tropical cyclone activity is good news for all those who live in and visit tropical north Queensland and Western Australia. However, there are some possible dark clouds on the horizon that we would be reckless to ignore.</p>
<h2>Global trends</h2>
<p>Several recent studies published in leading journals - including these papers involving the <a href="http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00010.1">Australian Bureau of Meteorology</a>, <a href="http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00549.1">Columbia University</a>, and the <a href="http://www.pnas.org/content/early/2013/07/05/1301293110.full.pdf+html">Massachusetts Institute of Technology</a> - have all separately projected the frequency of tropical cyclones will decrease in the Australian region due to global climate change. </p>
<p>But while the <em>number</em> of cyclones is expected to decrease, the <em>intensity</em> of those cyclones that do occur is expected to increase. </p>
<p>Those previous studies have suggested we would see those changes occur towards the middle to the end of the 21st century. However, our new study suggests this decline in cyclone frequency is already occurring. </p>
<p>We cannot be sure that this current decrease in cyclone activity is due to climate change - but it is mirroring the forecasts. </p>
<p>Our results also confirm the conclusions of other studies into long-term cyclone behaviour, which show that the past 40 to 100 years of cyclone activity in Australia has been very low compared to times previous.</p>
<h2>Planning based on a lull in the storm</h2>
<p>The results of our study suggest that we may have a problem with coastal development in cyclone-prone regions, particularly in built-up parts of Queensland. </p>
<p>For many years, Western Australia <a href="http://www.tesag.jcu.edu.au/staff/jnott/abstracts/Washed%20Away%20EPLJ%20%20proof.pdf">had a more cautious approach</a> on where coastal development was allowed, not allowing development any closer to the coast than where marine inundation occurs in a category 5 cyclone. However, this policy has now changed and is now more in line with Queensland coastal policy.</p>
<p>In northern Queensland, state and local government policies on minimum habitable floor levels for building within storm surge zones are only based on the history of cyclones over the last 40 years, and 100 years at best. </p>
<p>This period is unrepresentative of the natural variability of cyclones. So relying on this narrow window of time means that we are making risky assumptions about where it is safe to build homes, tourist resorts and vital public facilities such as hospitals.</p>
<p>The question can be asked as to why government policies do not base their minimum habitable floor levels on the studies of longer-term cyclone activity and a more comprehensive view of cyclone variability. </p>
<p>The reason probably lies in the different approaches used to derive these records. </p>
<p>The studies underpinning current planning policies are usually undertaken by practitioners who use only 40 years of actual cyclone records to generate long synthetic records, stretching out over thousands of years, up to 1.5 million years. The underlying assumption is that a short 40-year window of time is a true reflection of longer-term cyclone behaviour. </p>
<p>An alternative way to come up with a more conservative, long-term view of where cyclones could strike is by using geological or geochemical records, which register actual cyclone events.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/40003/original/sd7s5zky-1390891679.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/40003/original/sd7s5zky-1390891679.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/40003/original/sd7s5zky-1390891679.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/40003/original/sd7s5zky-1390891679.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/40003/original/sd7s5zky-1390891679.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/40003/original/sd7s5zky-1390891679.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/40003/original/sd7s5zky-1390891679.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/40003/original/sd7s5zky-1390891679.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&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 Yasi’s aftermath: the shredded asphalt of Bingil Bay Rd at Mission Beach in 2011.</span>
<span class="attribution"><span class="source">Flickr/Paul Toogood</span></span>
</figcaption>
</figure>
<h2>Risky decisions</h2>
<p>Our new research findings raise significant questions about how we plan for and develop cyclone-prone areas.</p>
<p>Consider these three scenarios.</p>
<p>The first - and luckiest - scenario would be for Australia to continue to have a low frequency of cyclones as we have in the past 40 years, with no increase in intensity when cyclones do hit. That’s the best possible scenario.</p>
<p>A second scenario - based on what we can see from our geological records - would be for this current calmer period to be simply a lull in the storm. If that’s the case, then we should be planning for a return to a higher, more historically “normal” number of tropical cyclones - meaning taking a more cautious, conservative approach in the way we develop tropical areas.</p>
<p>A third scenario - based on what we can see from our geological records, plus future projections that are in line with what we’ve seen in the past - would be that Australia may continue to see fewer tropical cyclones. However, when those cyclones do occur, they are more likely to be more intense, meaning greater risks to people and property. Again, this scenario would call for a more cautious, conservative approach in the way we develop tropical areas.</p>
<p>If either scenario two or three occurs, then many northern Australian coastal developments could be impacted by storm surge and inundations in the relatively near future.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/40054/original/chb5mtj9-1390952918.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/40054/original/chb5mtj9-1390952918.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/40054/original/chb5mtj9-1390952918.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/40054/original/chb5mtj9-1390952918.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/40054/original/chb5mtj9-1390952918.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/40054/original/chb5mtj9-1390952918.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/40054/original/chb5mtj9-1390952918.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/40054/original/chb5mtj9-1390952918.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">Mission Beach in Queensland after Cyclone Yasi in 2011.</span>
<span class="attribution"><span class="source">Flickr/Michael Dawes</span></span>
</figcaption>
</figure>
<h2>Hope for the best, prepare for the worst</h2>
<p>Essentially, we are faced with a choice. Continue to hope and plan for the best, as if this current 40-year lull will continue. Or hope for the best, but prepare for the worst.</p>
<p>It is also worth debating some of the ways in which state governments are ramping up coastal development, such as the Queensland government’s recent decision to remove a <a href="https://theconversation.com/scrapping-sea-level-protection-puts-australian-homes-at-risk-21271">safeguard in state planning policy</a> to consider future sea level rise (which could worsen storm surges in a cyclone).</p>
<p>The conservative approach that I believe is worth taking, based on our research and that of others, appears to be the opposite of what is now happening. So here’s hoping that Australia will continue to enjoy a relative lull in how often we have to face tropical cyclones.</p><img src="https://counter.theconversation.com/content/20814/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>The number of tropical cyclones hitting Queensland and Western Australia has fallen to low levels not seen for more than 500 years, new research published in Nature shows. But while that’s seemingly great…Jonathan Nott, Professor of Physical Geography, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/212162014-01-12T19:04:55Z2014-01-12T19:04:55ZWhat’s cranking up the heat across south-eastern Australia?<figure><img src="https://images.theconversation.com/files/38876/original/mnhnkrgs-1389521075.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Monday's heatwave forecast - with even worse heat predicted for the south-east this week.</span> <span class="attribution"><span class="source">http://www.bom.gov.au/australia/heatwave/</span></span></figcaption></figure><p>Across south-eastern Australia this morning, people are waking up to forecasts of scorching heat for the week ahead. Players and spectators heading to the Australian Open should prepare for some baking hot days at the tennis: <a href="http://www.bom.gov.au/vic/forecasts/melbourne.shtml">35°C today</a>, rising to 41°C on Tuesday, with temperatures in the high 30s or low 40s expected to linger until the weekend. </p>
<p>Coming after a relatively mild summer weekend, many of us will be wondering why it’s got so hot, so quickly.</p>
<p>That was the question my colleagues and I asked ourselves a year ago, when we began looking at the causes of severe heat waves. In particular, we wanted to know what made the 2009 summer heat wave - which set new records for the most days above 40°C in many parts of south-eastern Australia, and which killed hundreds of people - quite so deadly. Were there any hidden culprits behind the record-breaking spell of fierce heat?</p>
<p>What <a href="http://onlinelibrary.wiley.com/doi/10.1002/2013GL058257/abstract">we discovered</a> was that a seemingly unrelated tropical cyclone off the Western Australian coast contributed to making the south-eastern Australian heat wave worse. </p>
<p>And what’s about to happen with this week’s heat is a textbook example of what we found. </p>
<h2>Watching wild weather in the west</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/37579/original/xsfmyx5k-1386826784.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/37579/original/xsfmyx5k-1386826784.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/37579/original/xsfmyx5k-1386826784.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=757&fit=crop&dpr=1 600w, https://images.theconversation.com/files/37579/original/xsfmyx5k-1386826784.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=757&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/37579/original/xsfmyx5k-1386826784.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=757&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/37579/original/xsfmyx5k-1386826784.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=951&fit=crop&dpr=1 754w, https://images.theconversation.com/files/37579/original/xsfmyx5k-1386826784.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=951&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/37579/original/xsfmyx5k-1386826784.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=951&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tropical Cyclone Dominic over the Western Australian coast, late January 2009.</span>
<span class="attribution"><span class="source">Wikimedia Commons/NASA</span></span>
</figcaption>
</figure>
<p>This week, a tropical low is forecast to intensify over northern Western Australia, and a trough will extend from north-west to south-east across the state. Whether or not a tropical cyclone develops, the effects of these low pressure systems will be felt as far away as Melbourne and Hobart.</p>
<p>Our recent research in the internationally peer-reviewed journal Geophysical Research Letters explains <a href="http://onlinelibrary.wiley.com/doi/10.1002/2013GL058257/abstract">how tropical lows and tropical cyclones affect heat waves in south-eastern Australia</a>.</p>
<p>In late January 2009, <a href="http://www.bom.gov.au/cyclone/history/dominic.shtml">Tropical Cyclone Dominic</a> hit the Western Australian coastline, causing minor structural damage and bringing down power lines in the small Pilbara town of Onslow. Flooding of a nearby river resulted in significant crop damage, and caused a train to derail near Kalgoorlie.</p>
<p>But as cyclones go, Dominic wasn’t so bad: at its peak, the cyclone only reached category 2 status, well below the most severe category 5 level.</p>
<p>Yet as our research showed, even at that level, the cyclone over in Western Australia still had powerful downstream effects for the extreme heat wave across South Australia, southern New South Wales, Victoria and Tasmania in late January and into early February 2009.</p>
<p>During this heat wave, Ambulance Victoria was swamped with a record number of emergency calls, while the <a href="http://www.news.com.au/news/morgue-out-of-room-as-heatwave-drags-on/story-fna7dq6e-1111118760321">Adelaide morgue ran out of room</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/37580/original/xqg6npxp-1386826886.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/37580/original/xqg6npxp-1386826886.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/37580/original/xqg6npxp-1386826886.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=362&fit=crop&dpr=1 600w, https://images.theconversation.com/files/37580/original/xqg6npxp-1386826886.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=362&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/37580/original/xqg6npxp-1386826886.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=362&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/37580/original/xqg6npxp-1386826886.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=455&fit=crop&dpr=1 754w, https://images.theconversation.com/files/37580/original/xqg6npxp-1386826886.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=455&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/37580/original/xqg6npxp-1386826886.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=455&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Melbourne’s iconic Nylex clock on the city’s hottest day on record: 7 February 2009, when the temperature climbed to 46.4 °C.</span>
<span class="attribution"><span class="source">Wikimedia Commons/Melburnian</span></span>
</figcaption>
</figure>
<p>Later, the Victorian Department of Health estimated that <a href="http://docs.health.vic.gov.au/docs/doc/F7EEA4050981101ACA257AD80074AE8B/$FILE/heat_health_impact_rpt_Vic2009.pdf">374 “excess deaths”</a> occurred in the week of January 26 to February 1 2009. Although it is not possible to directly attribute mortality solely to the heat wave, there was a clear spike above the normal death rate, highlighting the health risks of heat waves, particularly for elderly people.</p>
<p>So <em>how</em> did Tropical Cyclone Dominic increase the intensity of that heat wave? And how do tropical lows in Australia’s west - like the one we’re seeing again this week - affect the weather as far away as south-eastern Australia?</p>
<h2>When the pressure’s on</h2>
<p>It turns out that the <a href="http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-12-00257.1%22%22">position of the tropical cyclone</a>, rather than its size or severity, is what really makes a difference.</p>
<p>It doesn’t even need to be a full-blown cyclone; as we’re currently seeing, even a tropical low can have a big impact on south-eastern Australia’s weather.</p>
<p>Heat waves in Victoria are associated with slow-moving high pressure systems, or <a href="http://www.bom.gov.au/climate/glossary/anticyclones.shtml">anticyclones</a>. These surface highs hang around over the Tasman Sea for several days, bringing hot northerly winds from the interior of the continent.</p>
<p>During heat waves in Victoria, there is also a similar anticyclone at higher levels in the atmosphere. </p>
<p>These upper level anticyclones form when very long, planetary-scale waves in the atmosphere (known as Rossby waves) break to the south of Australia. </p>
<p>Our <a href="http://onlinelibrary.wiley.com/doi/10.1002/2013GL058257/abstract">recent research</a> showed for the first time in Australia how those upper level anticyclones have been present in all of the most severe heat waves in Victoria over the past two decades.</p>
<h2>How cyclones work</h2>
<p>The <a href="http://www.bom.gov.au/cyclone/about/">circulation around tropical cyclones</a> at low levels is cyclonic, as air spirals in a clockwise direction (in the Southern Hemisphere; it spirals the other way in the Northern Hemisphere) into the centre of the storm where the pressure is lowest. </p>
<p>At upper levels, the air flows out again from the centre, and its nature changes to anticyclonic, switching to rotate in an anti-clockwise direction.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/TzqvGIAWHOk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The UK Met Office explains how cyclones and anticyclones work (note that in the Southern Hemisphere, the air flows in the opposite direction).</span></figcaption>
</figure>
<p>This outflowing air can intensify heat waves over Victoria in two ways. The first is when the outflow “nudges” the upper level jet stream, the band of strong westerly winds that circle the globe at mid-latitudes in both hemispheres. </p>
<p>When the outflowing air from the tropical cyclone nudges the jet stream south of western Australia, the disturbance generates more waves. This results in a stronger upper level anticyclone over Victoria.</p>
<p>The second way in which the intensification can occur is a direct result of the anticyclonic properties of the outflowing air. The outflowing air can be carried by the winds directly into the upper level anticyclone over Victoria. </p>
<p>The more intense the upper level anticyclone over Victoria, the more persistent it will be. This makes it more likely that a heat wave will form as higher temperatures continue for several days. </p>
<p>You can imagine this as being a bit like putting a pebble into a stream. The larger the pebble, the harder it will be for the water to shift it, and the more likely it is that the pebble will remain in place for a while as the water flows around it. </p>
<p>The cyclone effectively makes the pebble that is the anticyclone a little bit bigger, so that it stays stationary for longer.</p>
<p>Our improved understanding of how heat waves form should help weather forecasters better predict when extreme heat waves will hit Victoria.</p>
<p>It will also help in studies of how the intensity and duration of heat waves might change in the future due to climate change.</p>
<p>But in the short-term, when the heat is on at Rod Laver Arena this week: take a look way out west - and watch out for those cyclones.</p><img src="https://counter.theconversation.com/content/21216/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tess Parker has been supported in part by the Australian Research Council Centre of Excellence for Climate System Science. </span></em></p>Across south-eastern Australia this morning, people are waking up to forecasts of scorching heat for the week ahead. Players and spectators heading to the Australian Open should prepare for some baking…Tess Parker, PhD candidate, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/201872013-11-13T01:01:35Z2013-11-13T01:01:35ZInside Typhoon Haiyan and a year of weird weather<figure><img src="https://images.theconversation.com/files/35059/original/35fnd53h-1384302079.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Typhoon Haiyan as seen from space on November 9 by NASA astronaut Karen L. Nyberg.</span> <span class="attribution"><span class="source">http://twitter.com/AstroKarenN</span></span></figcaption></figure><p>Even before <a href="https://theconversation.com/topics/typhoon-haiyan">Typhoon Haiyan</a> struck the Philippines with <a href="http://www.abc.net.au/news/specials/typhoon-haiyan-photos-before-after/">such devastating force</a>, weather watchers around the world had been tracking this year’s typhoon season with intense interest.</p>
<p>Typhoon Haiyan has been seen as significant among meteorologists for several reasons - particularly because it has been part of such a strange season. </p>
<p>The 2013 tropical cyclone season in the Northwest Pacific started quite slowly and gradually accelerated, eventually setting a few records. </p>
<p>From January to September this year, we saw 23 <a href="http://www.bom.gov.au/cyclone/about/">tropical cyclones</a> form in the Northwest Pacific. Those cyclones involve low pressure systems forming over warm tropical waters, with sustained gale force winds of 63 km/h or more.</p>
<p>Yet during that same time in the Northwest Pacific, we only saw five <a href="http://www.bom.gov.au/faq/">typhoons</a> with sustained winds of more than 118 km/h, when in an average season we would have seen around 12 typhoons by the end of September.</p>
<p>But then last month, the tropical cyclone activity accelerated, particularly when it came to the strength or intensity of the storms. </p>
<p>Seven typhoons formed in the Northwest Pacific in October; a new record for the month. </p>
<p>And then came the November impact of Haiyan, which has been a sobering exclamation mark at what is typically the end of the season.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/w6p9KbVK97w?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Newly released footage showing Typhoon Haiyan blanketing the Philippines, shot with external cameras on the International Space Station. Source: NASATelevision, YouTube.</span></figcaption>
</figure>
<h2>The rise and deadly fall of a super typhoon</h2>
<p>Haiyan was the eighth typhoon to form in the Northwest Pacific since the start of October this year. It formed near 6°N on 3 November, possibly in association with an Equatorial Rossby wave — a westward moving atmospheric wave near the equator that can trigger convergence in the lower levels of the atmosphere.</p>
<p>On November 4, Haiyan first reached tropical cyclone strength, defined as winds greater than 63 km/h, and then it continued to strengthen. </p>
<p>As a typhoon, the winds around Haiyan reached a maximum sustained wind strength of 232 km/h on November 7. </p>
<p>To date, Typhoon Haiyan is the strongest storm of the 2013 season and among the strongest on record for the Northwest Pacific. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/02lNiAdVfGU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Tracking Haiyan, with an animation of its flood potential. Source: NASAgovVideo, YouTube.</span></figcaption>
</figure>
<p>Because the system made landfall in a highly populated and vulnerable part of the world coinciding with its peak intensity, <a href="http://www.abc.net.au/news/2013-11-13/typhoon-haiyan-death-toll-likely-lower-than-feared/5087698">its impact was devastating</a> for the communities it hit.</p>
<p>The coincident peak wind speeds occurring at landfall also helped produce a significant storm surge, a phenomenon that leads to higher than normal tides and waves along coastal areas. <a href="http://www.bom.gov.au/cyclone/about/stormsurge.shtml">Storm surges</a> are the single biggest threat to life in coastal areas from these events. </p>
<p>Haiyan is likely to have produced a storm surge of around 5 to 6 metres above the normal tide level, causing significant damage and loss of life along the coastal fringe of affected areas. </p>
<p>When the slightly less intense 1970 <a href="http://www.hurricanescience.org/history/storms/1970s/greatbhola/">Bhola cyclone</a> hit Bangladesh, up to 500,000 people died, mainly because of the associated storm surge. </p>
<p>When <a href="http://www.bom.gov.au/cyclone/history/monica.shtml">Severe Tropical Cyclone Monica</a> hit western Arnhem Land in 2006 with a similar intensity and storm surge to Haiyan, there were fortunately no fatalities because the point of landfall was sparsely populated.</p>
<p>Analysis after the event will no doubt refine estimates of Typhoon Haiyan’s maximum wind speed, storm surge, and other vital statistics. </p>
<p>But there’s no doubting it will be assessed as one of the worst tropical cyclones at landfall in recorded history. It is a strong reminder to us all that continued improvements in forecasting accuracy, warning response, and community resilience will help save lives on the ground.</p><img src="https://counter.theconversation.com/content/20187/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The Bureau of Meteorology provides Australians with environmental intelligence for their safety, sustainability, well-being and prosperity. Our weather, climate and water services include observations, alerts, warnings and forecasts for extreme events. Joel Lisonbee and Todd Smith do not consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and have no relevant affiliations.</span></em></p><p class="fine-print"><em><span>Todd Smith 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>Even before Typhoon Haiyan struck the Philippines with such devastating force, weather watchers around the world had been tracking this year’s typhoon season with intense interest. Typhoon Haiyan has been…Joel Lisonbee, Climatologist for the Bureau of Meteorology at the Northern Territory Climate Services Centre in Darwin, Australian Bureau of MeteorologyTodd Smith, Manager of Weather Services, Northern Territory, Australian Bureau of MeteorologyLicensed as Creative Commons – attribution, no derivatives.