tag:theconversation.com,2011:/africa/topics/lightning-4163/articles
Lightning – The Conversation
2024-02-27T19:06:16Z
tag:theconversation.com,2011:article/224151
2024-02-27T19:06:16Z
2024-02-27T19:06:16Z
Where does lightning strike? New maps pinpoint 36.8 million yearly ground strike points in unprecedented detail
<figure><img src="https://images.theconversation.com/files/578115/original/file-20240226-30-8qy4my.jpg?ixlib=rb-1.1.0&rect=0%2C18%2C5559%2C3511&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lightning strikes near St. George, Utah.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/curtain-of-lightning-over-city-royalty-free-image/186538582">jerbarber/iStock/Getty Images Plus</a></span></figcaption></figure><p>It’s been a warm day, maybe even a little humid, and the tall clouds in the distance remind you of cauliflower. You hear a sharp crack, like the sound of a batter hitting a home run, or a low rumble reminiscent of a truck driving down the highway. A distant thunderstorm, alive with lightning, is making itself known.</p>
<p>Lightning flashes in thunderstorms <a href="https://indd.adobe.com/view/ddf9619e-36e0-46b4-981d-3458b2532b98">at least 60 times per second</a> somewhere around the planet, sometimes even <a href="https://www.vaisala.com/en/blog/2023-03/revising-record-record-lightning-north-pole">near the North Pole</a>. </p>
<p>Each giant spark of electricity travels through the atmosphere at 200,000 miles per hour. It is hotter than the surface of the sun and delivers thousands of times more electricity than the power outlet that charges your smartphone. That’s why lightning is so dangerous.</p>
<p><a href="https://doi.org/10.1175/WCAS-D-15-0032.1">Lightning kills or injures about 250,000 people</a> around the world every year, most frequently in developing countries, where many people work outside without lightning-safe shelters nearby. In the United States, <a href="http://lightningsafetycouncil.org/LSC-LightningFatalities.html">an average of 28 people were killed by lightning every year between 2006 and 2023</a>. Each year, insurance pays about <a href="https://www.iii.org/fact-statistic/facts-statistics-lightning">US$1 billion</a> in claims for lightning damage, and around <a href="https://www.nifc.gov/fire-information/statistics/lightning-caused">4 million acres of land</a> burn in lightning-caused wildfires.</p>
<p><iframe id="4FALI" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/4FALI/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Yet, estimates of U.S. lightning strikes have varied widely, from about <a href="https://www.noaa.gov/news/new-lightning-tool-tells-striking-story">25 million a year</a>, a number meteorologists have cited since the 1990s, to <a href="https://www.cdc.gov/disasters/lightning/victimdata.html">40 million a year</a>, reported by the Centers for Disease Control and Prevention. That complicates lightning safety and protection efforts.</p>
<p>I’m a meteorologist whose research focuses on <a href="https://experts.news.wisc.edu/experts/chris-vagasky">understanding lightning behavior</a>. In a new study, my colleagues and I used six years of data from a national lightning detection network that we believe has become precise enough to offer a more accurate <a href="https://doi.org/10.1175/BAMS-D-22-0241.1">picture of lightning strikes across the U.S.</a> That knowledge is essential for improving forecasts and damage prevention.</p>
<h2>How much lightning strikes the US</h2>
<p>To get a clearer picture of how often lightning strikes, it helps to define what a lightning strike is. </p>
<p>Imagine looking out a window at a thunderstorm with cloud-to-ground lightning nearby. The lightning appears to flicker. </p>
<p>A lightning flash is all the cloud-to-ground lightning that occurs within 1 second and a 6-mile radius. Each flicker is a lightning stroke. Each stroke can hit one or more ground strike points, and there can be <a href="https://twitter.com/BBuffingtonNews/status/1126701479232823296?s=20">multiple strokes in the same channel</a>.</p>
<p>Lightning is a large electrical discharge trying to dissipate the electricity in a cloud, so if there is a lot of electricity built up, there can be a lot of lightning to get rid of it all.</p>
<p>Over six years of data from the <a href="https://doi.org/10.1175/JTECH-D-19-0215.1">National Lightning Detection Network</a>, we found that <a href="https://doi.org/10.1175/BAMS-D-22-0241.1">the U.S. averages</a> 23.4 million flashes, 55.5 million strokes and 36.8 million ground strike points each year. </p>
<h2>Where lightning strikes most often</h2>
<p>The basic ingredients for thunderstorms are warm and moist air near the ground with cooler, drier air above it and a way to lift the warm moist air. Anywhere those ingredients are present, lightning can occur. </p>
<p>This happens most frequently near the Gulf Coast, where the sea breeze helps trigger thunderstorms most days in the summer. Florida in particular is a hot spot for cloud-to-ground lightning strikes. The Miami-Fort Lauderdale area alone had over 120,000 lightning strokes in 2023.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578331/original/file-20240227-22-uf79br.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows the most activity in the Gulf Coast states, lessening moving north and westward." src="https://images.theconversation.com/files/578331/original/file-20240227-22-uf79br.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578331/original/file-20240227-22-uf79br.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=393&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578331/original/file-20240227-22-uf79br.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=393&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578331/original/file-20240227-22-uf79br.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=393&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578331/original/file-20240227-22-uf79br.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=494&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578331/original/file-20240227-22-uf79br.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=494&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578331/original/file-20240227-22-uf79br.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=494&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Frequency of lightning ground strikes per year, averaged over six years, shows the most activity along the Gulf Coast.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1175/BAMS-D-22-0241.1">Vagasky, et al, 2024</a></span>
</figcaption>
</figure>
<p>The Central and Southern U.S. aren’t quite as lightning prone, but they tend to have more thunderstorms and lightning strikes than the North and West of the country, though lightning in the West can be especially destructive <a href="https://www.nifc.gov/fire-information/statistics/lightning-caused">when it sparks wildfires</a>.</p>
<p>The cool waters of the Pacific Ocean, meanwhile, tend to mean few thunderstorms along the West Coast.</p>
<h2>Counting lightning strikes</h2>
<p>To be able to count how much lightning is hitting the ground and where it is doing so, you have to be able to detect it. Luckily, cloud-to-ground lightning is fairly easy to detect – in fact, you may have done it.</p>
<p>When lightning flashes, it acts like a giant radio antenna that sends electromagnetic waves – radio waves – around the world at the speed of light. If you have an AM radio station on during a thunderstorm, you may hear a lot of static.</p>
<p>The <a href="https://doi.org/10.1175/JTECH-D-19-0215.1">National Lightning Detection Network</a> uses strategically placed antennas to listen for these radio waves produced by lightning. It’s now able to locate at least 97% of the cloud-to-ground lightning that occurs across the U.S.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578369/original/file-20240227-26-hdvklo.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows the most activity in the Gulf Coast states, lessening over the Great Plains while still high in the mountains." src="https://images.theconversation.com/files/578369/original/file-20240227-26-hdvklo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578369/original/file-20240227-26-hdvklo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=393&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578369/original/file-20240227-26-hdvklo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=393&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578369/original/file-20240227-26-hdvklo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=393&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578369/original/file-20240227-26-hdvklo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=494&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578369/original/file-20240227-26-hdvklo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=494&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578369/original/file-20240227-26-hdvklo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=494&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 average number of cloud-to-ground lightning strike points per flash across the United States between 2017 and 2022.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1175/BAMS-D-22-0241.1">Vagasky, et al, 2024</a></span>
</figcaption>
</figure>
<p>The number of lightning strikes varies year to year depending on the prevailing weather patterns during the spring and summer months, when lightning is most common. There isn’t enough accurate U.S. data yet to say whether there is a trend toward more or less lightning. However, changes in lightning frequency and location can be an indicator of climate change affecting storms and precipitation, which is why the World Meteorological Organization designated lightning as an “<a href="https://gcos.wmo.int/en/essential-climate-variables/about">essential climate variable</a>.”</p>
<h2>Better data can boost safety</h2>
<p>Meteorologists and emergency management teams can use this new data and our analysis to better understand how lightning typically affects their regions. That can help them better forecast risks and prepare the public for thunderstorm hazards. Engineers are also using these results to create better <a href="https://webstore.iec.ch/preview/info_iec62305-3%7Bed2.0%7Den.pdf">lightning protection standards</a> to keep people and property safe.</p>
<p>Lightning strikes are still unpredictable. So, to stay safe, remember: When thunder roars, go indoors.</p><img src="https://counter.theconversation.com/content/224151/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Vagasky previously worked for Vaisala, owner-operator of the National Lightning Detection Network</span></em></p>
A new study shows how often lightning strikes and how it behaves, often hitting the ground with multiple strikes from the same flash.
Chris Vagasky, Meteorologist, University of Wisconsin-Madison
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/201365
2023-05-10T14:32:14Z
2023-05-10T14:32:14Z
Forest fires: North America’s boreal forests are burning a lot, but less than 150 years ago
<figure><img src="https://images.theconversation.com/files/514735/original/file-20230310-24-i3qohj.jpg?ixlib=rb-1.1.0&rect=2%2C2%2C1637%2C748&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Satellite image of a forest fire in July 2021 in northern Saskatchewan (Wapawekka Hills). The image covers an area of about 56 kilometres in width and is based on Copernicus Sentinel data.</span> <span class="attribution"><span class="source">(Pierre Markuse), CC BY 2.0</span></span></figcaption></figure><p>Unseasonably hot and dry weather conditions <a href="https://cwfis.cfs.nrcan.gc.ca/maps/fw?type=fdr&year=2023&month=5&day=5">in early May 2023</a> led to dozens of forest fires <a href="https://earthobservatory.nasa.gov/images/151313/fires-scorch-western-canada">in western Canada</a>. As of May 6, the Alberta government declared a <a href="https://edmonton.ctvnews.ca/alberta-declares-state-of-emergency-due-to-unprecedented-start-to-wildfire-season-1.6387641">state of emergency over wildfires</a>, and at the time of writing this article, <a href="https://www.cbc.ca/news/canada/edmonton/alberta-wildfires-environment-weather-extreme-1.6835352">nearly 30,000 people had to be evacuated</a>. Although it is too early to establish a precise assessment of this extreme episode, recent research allows us to place it in a broader context.</p>
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<img alt="" src="https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/524152/original/file-20230503-20-rp105s.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong>This article is part of <em>La Conversation Canada’s</em> series <a href="https://theconversation.com/ca-fr/topics/foret-boreale-138017">The boreal forest: A thousand secrets, a thousand dangers</a></strong></p>
<p><br><em>La Conversation Canada invites you to take a virtual walk in the heart of the boreal forest. In this series, our experts focus on management and sustainable development issues, natural disturbances, the ecology of terrestrial wildlife and aquatic ecosystems, northern agriculture and the cultural and economic importance of the boreal forest for Indigenous peoples. We hope you have a pleasant — and informative — walk through the forest!</em></p>
<hr>
<p>In North American boreal forests, several million hectares can go up in smoke in a single year. On the other hand, these forest fires can seem almost negligible for several consecutive years. During the past 60 years, <a href="https://doi.org/10.1139/cjfr-2018-0293">the area annually affected by forest fires has increased</a>, presumably because of climate change. Or at least that’s part of the explanation. </p>
<p>However, to better understand the long-term trends it is important to take a step back. This is the work our team of forest and fire ecology specialists recently carried out. </p>
<p><a href="https://doi.org/10.1071/WF22090">The results of our research</a> contradict the common wisdom about North American boreal forests — that they burned more in the past than they do today. But before we go into more detail about this, we feel it’s important to provide some background and context.</p>
<h2>What causes a forest fire?</h2>
<p>Scientists have been asking this question for a long time. Thanks to research carried out in the last few decades, the answer can now be summed up by three factors: vegetation, weather, and triggers.</p>
<p>Vegetation, which can be thought of as fuel, <a href="https://doi.org/10.1111/nph.12322">is a determining factor</a>. For example, large areas of dense coniferous forest are more likely to burn down than are deciduous forests with wetter undergrowth, or less dense forests. </p>
<p><a href="https://natural-resources.canada.ca/climate-change/impacts-adaptations/climate-change-impacts-forests/forest-change-indicators/fire-weather/17776">Meteorological factors also influence the flammability of fuels</a>; dry, windy conditions are highly conducive to the ignition and spread of fires. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507205/original/file-20230130-15993-d5dj3a.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Burned forest landscape in 2010 in the Radisson region (northern Quebec).</span>
<span class="attribution"><span class="source">(Guillaume Avajon)</span>, <span class="license">Fourni par l'auteur</span></span>
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<p>However, this combination of favourable conditions, itself, is not enough to generate a forest fire; there also needs to be a trigger. There are two types of triggers: lightning and humans. Although humans have been the cause of most fires started in recent decades in Canada, <a href="https://doi.org/10.1038/nclimate3329">lightning has actually been responsible for the largest area of burned forest</a>.</p>
<h2>Impacts on society</h2>
<p>When we hear about forest fires in the media, the news is usually tragic for communities. As a recent example, during the <a href="https://globalnews.ca/news/3138183/fort-mcmurray-wildfire-named-canadas-news-story-of-2016/">2016 Fort McMurray disaster</a>, some 600,000 hectares went up in smoke and over 88,000 people were evacuated. </p>
<p>Fires also have an economic impact on the forestry industry, as they consume millions of trees originally destined for mills. Moreover, fires accelerate climate change, as the burning of vegetation causes a massive release of CO2 into the atmosphere.</p>
<h2>A strong influence on ecosystems, but not necessarily negative</h2>
<p>The landscape we see a few weeks after a fire often looks apocalyptic. Forest fires leave significant traces on ecosystems and biodiversity. This is the case for certain species such as the Woodland Caribou, which depend on the presence of mature coniferous forests to survive. Fires <a href="https://doi.org/10.1016/j.gecco.2022.e02294">are therefore a threat to its survival</a>.</p>
<p>But, on the other hand, fires have always been part of forests, and are sometimes even essential to their ecological functioning. Most of the time, the burned landscape will gradually give way to vigorous young trees, which grow into a mature forest <a href="https://doi.org/10.1126/science.abf3903">in some 50 to 100 years</a>. Some tree species are even dependent on fire <a href="https://doi.org/10.1111/brv.12855">to regenerate and as a result, maintain themselves</a>. This is the case notably of <a href="https://doi.org/10.1139/x92-062">jack pine and black spruce</a>, which the forestry industry loves.</p>
<p>Many animal species are also fond of burned forests. Charred tree trunks provide food for <a href="https://doi.org/10.1071/WF08109">certain insect species</a>, such as the <a href="https://bugguide.net/node/view/573401/bgpage">black long-horned beetle</a>. Insects in turn provide abundant food for birds, like <a href="https://doi.org/10.1016/j.biocon.2009.01.022">black-backed woodpeckers</a>, which use snags (dead standing trees whose roots are still anchored to the ground) to nest.</p>
<p>In other words, fires are neither entirely good, nor entirely bad. It depends on your point of view. Additionally, as is often the case, it is also a question of balance…</p>
<h2>Reconstructing the history of fires over the last centuries</h2>
<p>Accurate records required to reconstruct the history of forest fires in Canada only go back to the 1960s. So how can we reconstruct the history of burned areas over the last few centuries? We can use the information contained in the trees themselves, and more specifically, their age. </p>
<p>In boreal forests, fire is a dominant natural disturbance. So, by determining the age of the oldest trees in a forest, provided these have not been cut down, <a href="https://doi.org/10.1078/1125-7865-00015">we can figure out the last time a forest burned</a>.</p>
<h2>A downward trend in burned areas over the past few centuries</h2>
<p>We gathered 16 studies that had independently applied the same method to different areas across North American boreal forests, from Alaska to Québec. After reanalysis of all this data in what scientists call a “meta-analysis,” <a href="https://doi.org/10.1071/WF22090%22%22">the results</a> are striking: North American boreal forests burned much more 150 years ago than they do today. In the earliest period covered by our data, between 1700 and 1850, the annual area burned was between two and more than 10 times greater than what has been observed over the past 40 years.</p>
<p>What explains this long-term downward trend? It is difficult to say based on the current state of research. Obviously, climate change is one of the suspects. The period from 1700 to 1850 was the end of what is known as the Little Ice Age, a period known for being colder, but probably also drier and, therefore, more conducive to fires. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map" src="https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=308&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=308&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=308&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=387&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=387&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507203/original/file-20230130-26-cydcyu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=387&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mapping of fires (red on map) in North American boreal forests (green area on map) since 1960. The graph on the left shows the total area burned per year in millions of hectares. Over this recent period, there is both a large variability from year to year, and also a slight upward trend. Infographic by Victor Danneyrolles based on https://cwfis.cfs.nrcan.gc.ca/ha/nfdb for Canada and https://fire.ak.blm.gov for Alaska.</span>
<span class="attribution"><span class="source">(Victor Danneyrolles)</span>, <span class="license">Fourni par l'auteur</span></span>
</figcaption>
</figure>
<p>The vegetation could also have changed and become less flammable, particularly as a result of cuts by the logging industry over the 20th century. Also during the 20th century the technological and financial means allocated to firefighting continued to increase, culminating in the 1970s with the appearance of <a href="https://simpleflying.com/canadair-cl-215-scooper-history/">water bomber aircraft</a>. Fire suppression policies could therefore have also played a role in reducing fires in some areas. </p>
<p>However, fires began to decline as early as the 19th century, long before human communities had a significant impact on the North American boreal forest environment. It seems more likely that climate change is the primary cause of the decrease in fires, superimposed by the impacts of human activity.</p>
<p>We hope new research will soon allow us to answer these questions. A better understanding of why fires have decreased or increased over the past few centuries will give us a head start in predicting what to expect from future climate change.</p><img src="https://counter.theconversation.com/content/201365/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Raphaël Chavardès has received funding from Fonds de recherche du Québec - Nature et technologie (FRQNT).</span></em></p><p class="fine-print"><em><span>Yves Bergeron has received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) and Fonds de recherche du Québec - Nature et technologie (FRQNT).</span></em></p><p class="fine-print"><em><span>Victor Danneyrolles ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>
North America’s boreal forests have been burning a lot, probably more and more over the past 60 years. Yet the long-term trend indicates that they are burning less than they were 150 years ago.
Victor Danneyrolles, Professeur-chercheur en écologie forestière, Université du Québec à Chicoutimi (UQAC)
Raphaël Chavardès, Postdoctoral fellow, Université du Québec en Abitibi-Témiscamingue (UQAT)
Yves Bergeron, Professeur écologie et aménagement forestier, Université du Québec en Abitibi-Témiscamingue (UQAT)
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/202387
2023-04-17T20:03:48Z
2023-04-17T20:03:48Z
Poorer countries must be compensated for climate damage. But how exactly do we crunch the numbers?
<figure><img src="https://images.theconversation.com/files/518641/original/file-20230331-16-w3md7w.jpg?ixlib=rb-1.1.0&rect=23%2C0%2C3970%2C2652&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Thoko Chikondi/AP</span></span></figcaption></figure><p>As the planet warms, a key concern in international climate negotiations is to compensate developing nations for the damage they suffer. But which nations should receive money? And which extreme weather events were influenced by climate change?</p>
<p>Most nations last year signed up to an <a href="https://theconversation.com/cop27-key-outcomes-progress-on-compensation-for-developing-countries-but-more-needed-on-climate-justice-and-equity-195017">agreement</a> to establish a so-called “loss and damage” fund. It <a href="https://www.unep.org/news-and-stories/story/what-you-need-know-about-cop27-loss-and-damage-fund">would provide</a> a means for developed nations – which are disproportionately responsible for greenhouse gas emissions – to <a href="https://www.climatecouncil.org.au/resources/loss-and-damage-and-climate-financing/">provide money to</a> vulnerable nations dealing with the effects of climate change.</p>
<p>Part of the fund would help developing nations recover from catastrophic extreme weather. For example, it might be used to rebuild homes and hospitals after a floods or provide food and emergency cash transfers after a cyclone.</p>
<p>Some experts have <a href="https://journals.plos.org/climate/article?id=10.1371/journal.pclm.0000013">suggested</a> the science of “event attribution” could be used to determine how the funds are distributed. Event attribution attempts to determine the causes of extreme weather events – in particular, whether human-caused climate change played a part.</p>
<p>But as our <a href="https://dx.doi.org/10.1038/s41558-023-01651-2">new paper</a> sets out, event attribution is not yet a good way to calculate compensation for nations vulnerable to climate change. An alternative strategy is needed. </p>
<h2>What is event attribution?</h2>
<p>Extreme weather events are complex and caused by multiple factors. The science of <a href="https://theconversation.com/is-climate-change-to-blame-for-extreme-weather-events-attribution-science-says-yes-for-some-heres-how-it-works-164941">extreme event attribution</a> primarily seeks to <a href="https://www.climate.gov/news-features/understanding-climate/extreme-event-attribution-climate-versus-weather-blame-game">work out</a> whether either human-caused climate change or natural variability in the climate contributed to these events.</p>
<p>For example, a recent study found the extreme rain that <a href="https://www.bbc.com/news/world-asia-64630183">triggered</a> New Zealand’s February flooding was up to <a href="https://www.carbonbrief.org/heavy-rainfall-from-new-zealands-cyclone-gabrielle-more-common-on-warmer-planet/">30% more intense</a> due to human influence on the climate system.</p>
<p>Attribution science is progressing quickly. It’s increasingly focused on extreme rain events, which in the past have been tricky to study. But it’s still not a consistent and robust way to estimate the costs and impacts of extreme events.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/cop27-one-big-breakthrough-but-ultimately-an-inadequate-response-to-the-climate-crisis-194056">COP27: one big breakthrough but ultimately an inadequate response to the climate crisis</a>
</strong>
</em>
</p>
<hr>
<h2>Why can’t we use it?</h2>
<p>Event attribution science draws on both observational weather data and climate model simulations. </p>
<p>Most commonly, two types of climate model simulations are used: those that include the effects of human-caused greenhouse gas emissions, and those that exclude them. Comparing the two types of simulations allows scientists to estimate how climate change influences the likelihood and severity of extreme events.</p>
<p>But climate models primarily simulate processes in the atmosphere and ocean. They don’t directly simulate the damage caused by an extreme weather event - such as how many people died due to a heatwave or infrastructure loss during a flood.</p>
<figure class="align-center ">
<img alt="turbulent ocean under stormy sky" src="https://images.theconversation.com/files/518644/original/file-20230331-26-4xhhkx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518644/original/file-20230331-26-4xhhkx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518644/original/file-20230331-26-4xhhkx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518644/original/file-20230331-26-4xhhkx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518644/original/file-20230331-26-4xhhkx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518644/original/file-20230331-26-4xhhkx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518644/original/file-20230331-26-4xhhkx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Climate models primarily simulate processes in the atmosphere and ocean.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>To directly simulate the effects of an extreme event, we need to know the exact extent to which weather components such as temperature and rainfall caused damage.
In <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac44c8/meta">some cases</a>, this can be determined. But it requires high-quality data, such as hospital admissions, that’s rarely available in most parts of the world.</p>
<p>Also, climate models are not good at simulating some extreme events, such as thunderstorms or extreme winds. That’s because such events are sporadic and tend to occur across small areas. This makes them harder to model than, say, a heatwave that affects a large area.</p>
<p>So if “loss and damage” funding decisions relied too much on event attribution, then a low-income nation hit by a heatwave may receive more support than a nation damaged by storms or high winds, relative to the damage caused.</p>
<p>What’s more, event attribution is not yet able to estimate how climate change causes damage associated with so-called “<a href="https://climateextremes.org.au/what-is-a-compound-event-in-weather-and-climate/">compound</a>” extreme events. </p>
<p>Compound events refer to cases where more than one extreme event occurs simultaneously in neighbouring regions, or consecutively in a single region. Examples include a drought followed by a heatwave, or sea level rise which makes damage from a tsunami even worse.</p>
<hr>
<p>
<em>
<strong>
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>
</strong>
</em>
</p>
<hr>
<h2>How do we move forward?</h2>
<p>Event attribution is not yet advanced enough to calculate “loss and damage” from climate change.</p>
<p>Instead, our paper suggests “loss and damage” funds are used alongside foreign aid spending to support recovery in low-income nations following any extreme events where human-caused climate change may have played a role.</p>
<p>We also present four major recommendations for using event attribution to estimate “loss and damage” in future. These are:</p>
<ol>
<li><p><strong>Help developing countries use event attribution techniques</strong>: to date, event attribution has <a href="https://www.carbonbrief.org/mapped-how-climate-change-affects-extreme-weather-around-the-world/">largely been conducted</a> by wealthy countries in their own regions</p></li>
<li><p><strong>Address more types of extreme events</strong>: tornadoes, hailstorms and lightning are largely beyond the capability of climate models used in event attribution because they are localised and complex. New techniques to examine these events should be attempted</p></li>
<li><p><strong>More research into the impacts and costs of extreme events</strong>: few studies have attempted to attribute the costs of extreme events to climate change. Further efforts are needed, especially in low-income nations</p></li>
<li><p><strong>Combine event attribution with other knowledge</strong>: scientists and experts in aid and policymaking must collaborate on a strategy for using event attribution information. Better understanding of the needs of policymakers and the limitations of event attribution science could lead to more useful studies.</p></li>
</ol>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-is-white-colonisation-of-the-atmosphere-its-time-to-tackle-this-entrenched-racism-185579">Climate change is white colonisation of the atmosphere. It's time to tackle this entrenched racism</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="foamy ocean crashes onto foreshore and car" src="https://images.theconversation.com/files/518646/original/file-20230331-14-hzsxo5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518646/original/file-20230331-14-hzsxo5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518646/original/file-20230331-14-hzsxo5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518646/original/file-20230331-14-hzsxo5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518646/original/file-20230331-14-hzsxo5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518646/original/file-20230331-14-hzsxo5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518646/original/file-20230331-14-hzsxo5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Event attribution is not yet advanced enough to calculate ‘loss and damage’ from climate change.</span>
<span class="attribution"><span class="source">Halden Krog/AP</span></span>
</figcaption>
</figure>
<h2>A growing burden</h2>
<p>Low-income nations have contributed relatively little to global emissions. Compensation from richer nations is vital to helping them manage the <a href="https://climatechampions.unfccc.int/cop27-presidency-announces-ambitous-climate-resilience-agenda/">growing burden</a> of climate harms. </p>
<p>But distributing these funds in a fair way is challenging. Until the field of event attribution advances, putting too much reliance on event attribution is a risky strategy. </p>
<hr>
<p><em>The authors acknowledge the contribution of Izidine Pinto to the research underpinning this article.</em></p><img src="https://counter.theconversation.com/content/202387/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew King receives funding from the National Environmental Science Program. </span></em></p><p class="fine-print"><em><span>Joyce Kimutai receives funding from Kenya's Ministry of Environment, Forestry and Climate Change</span></em></p><p class="fine-print"><em><span>Luke Harrington receives funding from New Zealand's Ministry for Business, Innovation and Employment. </span></em></p><p class="fine-print"><em><span>Michael Grose receives funding from National Environmental Science Program. </span></em></p>
Extreme weather events are complex – and working out exactly how much damage climate change caused is a tricky task.
Andrew King, Senior Lecturer in Climate Science, The University of Melbourne
Joyce Kimutai, Climate Scientist, University of Cape Town
Luke Harrington, Senior Lecturer in Climate Change, University of Waikato
Michael Grose, Climate projections scientist, CSIRO
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/197384
2023-02-01T16:00:30Z
2023-02-01T16:00:30Z
Western wildfires destroyed 246% more homes and buildings over the past decade – fire scientists explain what’s changing
<figure><img src="https://images.theconversation.com/files/507476/original/file-20230201-25-abby5u.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4456%2C2972&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The fire risk goes beyond rising temperatures and dry conditions.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/the-shady-fire-can-be-seen-on-the-hillside-behind-homes-in-news-photo/1228763017">Samuel Corum / AFP via Getty Images</a></span></figcaption></figure><p>It can be tempting to think that the recent wildfire disasters in communities across the West were unlucky, one-off events, but evidence is accumulating that points to a trend.</p>
<p>In a <a href="https://academic.oup.com/pnasnexus/article-lookup/doi/10.1093/pnasnexus/pgad005">new study</a>, we found a 246% increase in the number of homes and structures destroyed by wildfires in the contiguous Western U.S. between the past two decades, 1999-2009 and 2010-2020.</p>
<p>This trend is strongly influenced by major fires in <a href="https://www.fire.ca.gov/incidents/2017/">2017</a>, <a href="https://www.earthobservatory.nasa.gov/images/event/92344/2018-fire-season-in-the-western-united-states">2018</a> and <a href="https://theconversation.com/the-year-the-west-was-burning-how-the-2020-wildfire-season-got-so-extreme-148804">2020</a>, including destructive fires in Paradise and Santa Rosa, California, and in Colorado, Oregon and Washington. In fact, in nearly every Western state, more homes and buildings were destroyed by wildfire over the past decade than the decade before, revealing increasing vulnerability to wildfire disasters.</p>
<p>What explains the increasing home and structure loss? </p>
<p>Surprisingly, it’s not just the trend of <a href="https://doi.org/10.1126/sciadv.abc0020">burning more area</a>, or simply <a href="https://doi.org/10.1029/2020EF001795">more homes being built where fires historically burned</a>. While those trends play a role, increasing home and structure loss is outpacing both. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507478/original/file-20230201-18-uh6uyc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Streets with burned cars and nothing left of homes but ash." src="https://images.theconversation.com/files/507478/original/file-20230201-18-uh6uyc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507478/original/file-20230201-18-uh6uyc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507478/original/file-20230201-18-uh6uyc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507478/original/file-20230201-18-uh6uyc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507478/original/file-20230201-18-uh6uyc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507478/original/file-20230201-18-uh6uyc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507478/original/file-20230201-18-uh6uyc.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">Entire neighborhoods were reduced to ash when a wildfire spread into Santa Rosa, California, in 2017.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/an-aerial-view-of-homes-that-were-destroyed-by-the-tubbs-news-photo/860298164">Justin Sullivan/Getty Images</a></span>
</figcaption>
</figure>
<p>As fire scientists, we have spent decades studying the <a href="https://scholar.google.com/citations?user=6HxI4VAAAAAJ&hl=en&oi=sra">causes</a> and <a href="https://earthlab.colorado.edu/our-team/max-cook">impacts of wildfires</a>, in both <a href="https://scholar.google.com/citations?user=LyjuxcEAAAAJ&hl=en">the recent</a> and <a href="https://scholar.google.com/citations?user=Tmjced4AAAAJ&hl=en&oi=ao%22%22">more distant past</a>. It’s clear that the current <a href="https://www.fs.usda.gov/managing-land/wildfire-crisis">wildfire crisis</a> in the Western U.S. has human fingerprints all over it. In our view, now more than ever, humanity needs to understand its role.</p>
<h2>Wildfires are becoming more destructive</h2>
<p>From 1999 to 2009, an average of 1.3 structures were destroyed for every 4 square miles burned (1,000 hectares, or 10 square kilometers). This average more than doubled to 3.4 during the following decade, 2010-2020.</p>
<p>Nearly every Western state lost more structures for every square mile burned, with the exception of New Mexico and Arizona. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507398/original/file-20230131-12649-12yugh.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Charts showing rising trend of loses from fires." src="https://images.theconversation.com/files/507398/original/file-20230131-12649-12yugh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507398/original/file-20230131-12649-12yugh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=622&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507398/original/file-20230131-12649-12yugh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=622&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507398/original/file-20230131-12649-12yugh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=622&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507398/original/file-20230131-12649-12yugh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=782&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507398/original/file-20230131-12649-12yugh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=782&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507398/original/file-20230131-12649-12yugh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=782&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://academic.oup.com/pnasnexus/article-lookup/doi/10.1093/pnasnexus/pgad005">Adapted from Higuera, et al., PNAS Nexus 2023</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Humans increasingly cause destructive wildfires</h2>
<p>Given the damage from the wildfires you hear about on the news, you may be surprised to learn that <a href="https://academic.oup.com/pnasnexus/article-lookup/doi/10.1093/pnasnexus/pgad005">88% of wildfires in the West over the past two decades destroyed zero structures</a>. This is, in part, because the majority of area burned (65%) is still due to lightning-ignited wildfires, often in remote areas. </p>
<p>But among wildfires that do burn homes or other structures, humans play a disproportionate role – 76% over the past two decades were started by unplanned human-related ignitions, including backyard burning, downed power lines and campfires. The area burned from human-related ignitions rose 51% between 1999-2009 and 2010-2020.</p>
<p>This is important because wildfires started by human activities or infrastructure have <a href="https://theconversation.com/humans-ignite-almost-every-wildfire-that-threatens-homes-145997">vastly different impacts</a> and characteristics that can make them more destructive. </p>
<p>Unplanned human ignitions typically <a href="https://doi.org/10.3390/fire3030050">occur near buildings</a> and <a href="https://doi.org/10.1038/s41467-022-30030-2">tend to burn in grasses</a> that dry out easily and burn quickly. And people have built more homes and buildings in areas surrounded by flammable vegetation, with the number of structures <a href="https://academic.oup.com/pnasnexus/article-lookup/doi/10.1093/pnasnexus/pgad005">up by 40% over the past two decades across the West</a>, with every state contributing to the trend.</p>
<p>Human-caused wildfires also <a href="https://doi.org/10.1073/pnas.1617394114">expand the fire season</a> beyond the summer months when lightning is most common, and they are particularly destructive during late summer and fall when they <a href="https://doi.org/10.1029/2021GL092520">overlap with periods of high winds</a>. </p>
<p>As a result, of all the wildfires that destroy structures in the West, human-caused events typically <a href="https://academic.oup.com/pnasnexus/article-lookup/doi/10.1093/pnasnexus/pgad005">destroy over 10 times more</a> structures for every square mile burned, compared to lighting-caused events.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507514/original/file-20230201-19-uvb9zw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map showing where fires burned in 1999-2009 and 2010-2020, comparing lightning-sparked to human-ignition and the amount of structures burned from each. More structures were burned in human-started fires." src="https://images.theconversation.com/files/507514/original/file-20230201-19-uvb9zw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507514/original/file-20230201-19-uvb9zw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=667&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507514/original/file-20230201-19-uvb9zw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=667&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507514/original/file-20230201-19-uvb9zw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=667&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507514/original/file-20230201-19-uvb9zw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=838&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507514/original/file-20230201-19-uvb9zw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=838&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507514/original/file-20230201-19-uvb9zw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=838&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://academic.oup.com/pnasnexus/article-lookup/doi/10.1093/pnasnexus/pgad005">Adapted from Higuera, et al., PNAS Nexus 2023</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The December 2021 Marshall Fire that destroyed more than 1,000 homes and buildings in the suburbs near Boulder, Colorado, <a href="https://www.9news.com/article/news/local/wildfire/marshall-fire/marshall-fire-cause-investigation-ignition-points/73-18bfe8fa-b034-4879-98ab-32af0008a1ec">fit this pattern to a T</a>. Powerful winds <a href="https://theconversation.com/devastating-colorado-fires-cap-a-year-of-climate-disasters-in-2021-with-one-side-of-the-country-too-wet-the-other-dangerously-dry-173402">sent the fire</a> racing through neighborhoods and vegetation that was unusually dry for late December. </p>
<p>As human-caused <a href="https://doi.org/10.1073/pnas.1607171113">climate change</a> leaves vegetation more flammable later into each year, the consequences of accidental ignitions are magnified.</p>
<h2>Putting out all fires isn’t the answer</h2>
<p>This might make it easy to think that if we just put out all fires, we would be safer. Yet a focus on <a href="https://wildfiretoday.com/2022/03/03/bill-introduced-to-require-suppression-of-all-us-forest-service-fires/">stopping wildfires at all costs</a> is, in part, what <a href="https://theconversation.com/from-smokey-bear-to-climate-change-the-future-of-wildland-fire-management-45082">got the West into its current predicament</a>. Fire risks just accumulate for the future.</p>
<p>The amount of flammable vegetation has increased in many regions because of an absence of burning due to emphasizing fire suppression, preventing <a href="https://www.fs.usda.gov/research/treesearch/58212">Indigenous fire stewardship</a> and a fear of fire in any context, well exemplified by <a href="https://theconversation.com/smokey-the-bear-is-still-keeping-his-watchful-eye-on-americas-forests-after-75-years-on-the-job-120207">Smokey Bear</a>. Putting out every fire quickly removes the positive, <a href="https://education.nationalgeographic.org/resource/ecological-benefits-fire">beneficial effects of fires</a> in Western ecosystems, including clearing away hazardous fuels so future fires burn less intensely.</p>
<h2>How to reduce risk of destructive wildfires</h2>
<p>The good news is that people have the ability to affect change, now. Preventing wildfire disasters necessarily means minimizing unplanned human-related ignitions. And it requires more than <a href="https://smokeybear.com/">Smokey Bear’s</a> message that “only you can prevent forest fires.” Infrastructure, like downed power lines, <a href="https://www.fire.ca.gov/media/5121/campfire_cause.pdf">has caused</a> some of the deadliest wildfires in recent years. </p>
<p>Reducing wildfire risks across communities, states and regions <a href="https://www.fs.usda.gov/research/treesearch/58436">requires transformative changes</a> beyond individual actions. We need <a href="https://deloitte.wsj.com/articles/fighting-wildfires-with-innovation-01669832378?mod=Deloitte_sus_wsjsf_h1&tesla=y">innovative approaches</a> and <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac5c0c">perspectives</a> for <a href="https://theconversation.com/how-to-build-wildfire-resistant-communities-in-a-warming-world-174582">how we build</a>, provide power and <a href="https://storymaps.arcgis.com/stories/64f55848f690452da6c58e5a888ff283">manage lands</a>, as well as mechanisms that ensure changes work <a href="https://doi.org/10.1371/journal.pone.0205825">across socioeconomic levels</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507516/original/file-20230201-24-qtbg4i.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Dot chart showing how each state's area and buildings burned changed. Calfiornia, Oregon and the West overall had above average loss and above average burning. Colorado had above average loss and below average burning." src="https://images.theconversation.com/files/507516/original/file-20230201-24-qtbg4i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507516/original/file-20230201-24-qtbg4i.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=698&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507516/original/file-20230201-24-qtbg4i.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=698&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507516/original/file-20230201-24-qtbg4i.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=698&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507516/original/file-20230201-24-qtbg4i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=877&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507516/original/file-20230201-24-qtbg4i.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=877&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507516/original/file-20230201-24-qtbg4i.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=877&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://academic.oup.com/pnasnexus/article-lookup/doi/10.1093/pnasnexus/pgad005">Adapted from Higuera, et al., PNAS Nexus 2023</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Actions to reduce risk will vary, since how people live and how wildfires burn vary widely across the West. </p>
<p>States with large tracts of land with little development, like Idaho and Nevada, can accommodate widespread burning, largely from lighting ignition, with little structure loss. </p>
<p>California and Colorado, for example, require different approaches and priorities. Growing communities can <a href="https://headwaterseconomics.org/wildfire/homes-risk/building-costs-codes/%22%22">carefully plan if and how they build</a> in flammable landscapes, support <a href="https://fireadapted.org/resource/potential-operational-delineations/">wildfire management for risks and benefits</a>, and <a href="https://theconversation.com/bringing-tech-innovation-to-wildfires-4-recommendations-for-smarter-firefighting-as-megafires-menace-the-us-162178">improve firefighting efforts</a> when wildfires do threaten communities.</p>
<p><a href="https://doi.org/10.1029/2018GL080959">Climate change</a> remains the elephant in the room. Left unaddressed, warmer, drier conditions will exacerbate challenges of living with wildfires. And yet we can’t wait. Addressing climate change can be paired with <a href="https://theconversation.com/well-see-more-fire-seasons-like-2020-heres-a-strategy-for-managing-our-nations-flammable-landscapes-149323">reducing risks immediately to live more safely</a> in an increasingly flammable West.</p><img src="https://counter.theconversation.com/content/197384/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Philip Higuera receives funding from the federally funded Joint Fire Sciences Program, United States Geological Survey, and National Science Foundation.</span></em></p><p class="fine-print"><em><span>Jennifer Balch receives funding from NSF, Deloitte, JFSP, OPP, and USGS.</span></em></p><p class="fine-print"><em><span>Maxwell Cook receives funding from the federally funded Joint Fire Sciences Program and the Earth Lab at University of Colorado Boulder, and is a student member of the Ecological Society of America and the American Geophysical Union.</span></em></p><p class="fine-print"><em><span>Natasha Stavros receives funding from NSF, NASA, Southern California Edison, Deloitte, and AXA XL. She is affiliated with the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder, owns a company called WKID Solutions LLC and serves as a member on the Hazard Mitigation Enterprise Board for the Colorado State Emergency Response Program.</span></em></p>
More homes are burning in wildfires in nearly every Western state. The reason? Humans.
Philip Higuera, Professor of Fire Ecology, University of Montana
Jennifer Balch, Associate Professor of Geography and Director, Earth Lab, University of Colorado Boulder
Maxwell Cook, Ph.D. Student, Dept. of Geography, University of Colorado Boulder
Natasha Stavros, Director of the Earth Lab Analytics Hub, University of Colorado Boulder
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/198116
2023-01-20T06:14:04Z
2023-01-20T06:14:04Z
Scientists have started steering lightning with lasers – here’s how
<figure><img src="https://images.theconversation.com/files/505198/original/file-20230118-22-izbt03.jpg?ixlib=rb-1.1.0&rect=8%2C8%2C5450%2C2359&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/lightning-thunderstorm-flash-over-night-sky-1157210851">Triff/Shutterstock</a></span></figcaption></figure><p>Lightning may look beautiful but every year it kills thousands of people, does huge amounts of damage to buildings and infrastructure, and causes power outages. </p>
<p>The only protection we have is lightning rods, which were invented 300 years ago and only protect a small area. </p>
<p>The cost of damage from lightning strikes to buildings is hard to determine globally, but insurance company payouts to cover repairs to homes and businesses were roughly <a href="https://www.iii.org/press-release/cost-of-lightning-caused-claims-soared-due-to-2020s-us-wildfires-061721">US$2 billion (£1.6 billion) in 2020</a> in the US. Insurance data from the UK suggests <a href="https://www.thisismoney.co.uk/money/mortgageshome/article-3656436/Lightning-damage-claims-15-times-higher-usual-month-says-Direct-Line.html">the costs of covering lightning strikes are increasing</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/505344/original/file-20230119-25-rqinxz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505344/original/file-20230119-25-rqinxz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505344/original/file-20230119-25-rqinxz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505344/original/file-20230119-25-rqinxz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505344/original/file-20230119-25-rqinxz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505344/original/file-20230119-25-rqinxz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505344/original/file-20230119-25-rqinxz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Swiss scientists used a laser to move lightning.</span>
<span class="attribution"><a class="source" href="https://phototheque.unige.ch/unige:165525">Martin Stollberg/© TRUMPF</a></span>
</figcaption>
</figure>
<p>The problem is only likely to get worse as the climate crisis is driving a surge in wildfires worldwide, <a href="https://www.nature.com/articles/s43247-021-00233-4/figures/1">which increase lightning strikes</a>. A study from 2014 suggested the <a href="https://www.scientificamerican.com/article/lightning-may-increase-with-global-warming/">number of strikes increases by 12%</a> for every degree (celsius) of global warming.</p>
<p>Lighting rods have their uses, but scientists have been looking for a better way to control where lightning strikes, and <a href="https://www.nature.com/articles/s41566-022-01139-z">lasers</a> may be the solution, according to a new study.</p>
<h2>How they did it</h2>
<p>This latest experiment was performed near a telecommunications tower on the Säntis mountain in Switzerland that is frequently struck by lightning - roughly 100 times a year, although the tower itself is protected by a lightning rod.</p>
<p>The results from <a href="https://www.nature.com/articles/s41566-022-01139-z">the study</a> found the lightning flowed almost in a straight line near the laser pulses, but the lightning strikes were more randomly distributed when the laser was off. </p>
<p>While this study is not the first attempt to direct lightning paths it is the first to show it can be done. The scientists have attributed this to the high power laser they used, and the high altitude. At high altitudes air is less dense. This makes it easier for current to pass through, meaning that future experiments at sea level would require a more powerful laser.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/505342/original/file-20230119-12-nqh959.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505342/original/file-20230119-12-nqh959.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505342/original/file-20230119-12-nqh959.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505342/original/file-20230119-12-nqh959.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505342/original/file-20230119-12-nqh959.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505342/original/file-20230119-12-nqh959.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505342/original/file-20230119-12-nqh959.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The laser on the summit of the Säntis (2500m) was focused above a 124m high transmitter tower, equipped with a traditional lightning conductor.</span>
<span class="attribution"><a class="source" href="https://phototheque.unige.ch/unige:165526">Martin Stollberg/© TRUMPF</a></span>
</figcaption>
</figure>
<p>To understand how the scientists used light to change the path of electricity you need to understand what lightning actually is: a flow of charged particles from one
location to another. Particles in clouds are mostly electrically neutral when they form but build up <a href="https://scied.ucar.edu/learning-zone/storms/thunder-and-lightning">both positive and negative charge</a>. The cloud wants to become neutral by exchanging charge with the ground. </p>
<p>The type of lighting most people are familiar with is the jagged strikes of bright light seen between the ground and the clouds, but there are other types. Lightning can travel between clouds. It can also move from <a href="https://www.esa.int/ESA_Multimedia/Videos/2016/04/Red_sprites_and_blue_jets">clouds upwards</a>
towards the upper atmosphere. This can even produce strings of red airglow where the thinner atmosphere warms. This heat energy is then released as light. </p>
<p>As the charge in the cloud builds up it reaches incredibly high voltages (roughly equivalent to 8 million car batteries hooked up together) which rips a path through the air. The electrical current required to split the components of air apart generally is about 300 million volts per square metre. </p>
<p>The pushing force of this enormous voltage in electrically charged (ionised) air allows the charge from the cloud to flow down and discharge into the ground or nearby buildings. This current flow will follow the most electrically conductive path. </p>
<p>This is why <a href="https://www.fi.edu/history-resources/franklins-lightning-rod">lightning rods</a> are sometimes used to protect buildings from lightning. Metal is more electrically conductive than air so if you place a large rod in the ground lightning will have an easier path than going through the air. It can only protect a small area, though. </p>
<p>Many researchers think <a href="https://www.earthdata.nasa.gov/learn/sensing-our-planet/cosmic-charges">some lightning storms could be caused by cosmic rays</a> (highly energetic particles from outside the solar system). These particles pass through the atmosphere and interact with air to create an ionised path through their direction of travel. This is a theory that has researchers split on whether it affects the number of total lightning strikes around the world.</p>
<p>The scientists used a powerful laser to try and create ionised paths in a similar way to the cosmic ray theory. Firing rapid (1,000 times a second) energetic pulses with a laser heats the air and <a href="https://scitechdaily.com/record-breaking-terahertz-laser-beam-turns-air-into-glowing-plasma/">ionises it</a>, briefly becoming conductive. The lightning strike will have less resistance along this path and so will be more inclined to flow that way.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Ym1fEbm1FUs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>If this technology is perfected, it might one day help <a href="https://ec.europa.eu/research-and-innovation/en/projects/success-stories/all/laser-technology-%20protect-critical-infrastructure-lightning-strikes">protect infrastructure</a> such as airports and nuclear power plants. It could even be used in a more advanced form to protect houses using a laser a safe distance away. However, it is unlikely to be rolled out near you anytime soon, if for no other reason than the power costs.</p><img src="https://counter.theconversation.com/content/198116/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Whittaker 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>
This high voltage experiment isn’t one you’ll be able to try at home.
Ian Whittaker, Senior Lecturer in Physics, Nottingham Trent University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/195549
2022-12-01T23:33:47Z
2022-12-01T23:33:47Z
Why does lightning zigzag? At last, we have an answer to the mystery
<figure><img src="https://images.theconversation.com/files/497802/original/file-20221129-22-26r0mu.jpg?ixlib=rb-1.1.0&rect=0%2C6%2C4493%2C2977&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>Everyone has seen lightning and marvelled at its power. But despite its frequency – about 8.6 million lightning strikes occur worldwide every day – why lightning proceeds in a series of steps from the thundercloud to the earth below has remained a mystery.</p>
<p>There are a few textbooks on lightning, but none have explained how these “zigzags” (called steps) form, and how lightning can travel over kilometres. My <a href="https://iopscience.iop.org/article/10.1088/1361-6463/aca103">new research</a> provides an explanation.</p>
<p>The intense electrical fields in thunderclouds excite electrons to have enough energy to create what are known as “singlet delta oxygen molecules”. These molecules and electrons build up to create a short, highly conducting step, which lights up intensely for a millionth of a second. </p>
<p>At the end of the step, there is a pause as the build-up happens again, followed by another bright, flashing leap. The process is repeated again and again.</p>
<p>An increase in extreme weather events means lightning protection is increasingly important. Knowing how a lightning strike is initiated means we can work out how to better protect buildings, aeroplanes and people. Also, while the use of environmentally friendly composite materials in aircraft is improving fuel efficiency, these materials <a href="https://www.compositesworld.com/articles/lightning-strike-protection-strategies-for-composite-aircraft">increase the risk of lightning damage</a>, so we need to look at additional protection.</p>
<figure class="align-center ">
<img alt="storm clouds" src="https://images.theconversation.com/files/497809/original/file-20221129-20-278krv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497809/original/file-20221129-20-278krv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=286&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497809/original/file-20221129-20-278krv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=286&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497809/original/file-20221129-20-278krv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=286&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497809/original/file-20221129-20-278krv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=359&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497809/original/file-20221129-20-278krv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=359&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497809/original/file-20221129-20-278krv.jpg?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">
<figcaption>
<span class="caption">An increase in atmospheric moisture and warmth is fuelling more intense storms.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>What leads up to a lightning strike?</h2>
<p>Lightning strikes happen when thunderclouds with an electric potential of millions of volts are connected to the earth. A current of thousands of amps flows between the ground and the sky, with a temperature of tens of thousands of degrees. </p>
<p>Photographs of lightning reveal a host of details not observed by the naked eye. Usually there are four or five faint “leaders” coming from the cloud. These are branched and zigzag on an irregular path towards the earth. </p>
<p>The first of these leaders to reach the earth initiates the lightning strike. The other leaders are then extinguished.</p>
<p>Fifty years ago, high-speed photography revealed still more complexity. The leaders progress downwards from the cloud in “steps” about 50 metres long. Each step becomes bright for a millionth of a second, but then there is almost complete darkness. After a further 50 millionths of a second another step forms, at the end of the preceding step, but the previous steps remain dark. </p>
<p>Why are there such steps? What is happening in the dark periods between steps? How can the steps be electrically connected to the cloud with no visible connection?</p>
<p>The answers to these questions lie in understanding what happens when an energetic electron hits an oxygen molecule. If the electron has enough energy, it excites the molecule into the singlet delta state. This is a “metastable” state, which means it is not perfectly stable – but it usually doesn’t fall into a lower energy state for 45 minutes or so.</p>
<p>Oxygen in this singlet delta state detaches electrons (required for electricity to flow) from negative oxygen ions. These ions are then replaced almost immediately by electrons (which carry a negative charge) again attaching to oxygen molecules. When more than 1% of the oxygen in the air is in the metastable state, the air can conduct electricity. </p>
<p>So the lightning steps occur as enough of the metastable states are created to detach a significant number of electrons. During the dark part of a step, the density of metastable states and electrons is increasing. After 50 millionths of a second, the step can conduct electricity – and the electrical potential at the tip of the step increases to approximately that of the cloud, and produces a further step. </p>
<p>The excited molecules created in previous steps form a column all the way to the cloud. The whole column is then electrically conducting, with no requirement of an electric field and little emission of light.</p>
<h2>Protecting people and property</h2>
<p>The understanding of lightning formation is important for the design of protection for buildings, aircraft and also people. While it is <a href="https://www.uwa.edu.au/study/-/media/Faculties/Science/Docs/Lightning-facts.pdf">rare for lightning to hit people</a>, buildings are hit many times – especially tall and isolated ones.</p>
<p>When lightning hits a tree, sap inside the tree boils and the resulting steam creates pressure, splitting open the trunk. Similarly, when lightning hits the corner of a building, water from rain that has seeped into the concrete boils. The pressure blasts off the whole corner of the building, creating the risk of deadly collapses.</p>
<figure class="align-center ">
<img alt="A blackened tree shattered by a lightning strike" src="https://images.theconversation.com/files/497810/original/file-20221129-22-4q05yd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497810/original/file-20221129-22-4q05yd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497810/original/file-20221129-22-4q05yd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497810/original/file-20221129-22-4q05yd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497810/original/file-20221129-22-4q05yd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497810/original/file-20221129-22-4q05yd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497810/original/file-20221129-22-4q05yd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">By causing water inside structures to boil, a lightning strike can blast apart trees and buildings.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>A lightning rod invented by Benjamin Franklin in 1752 is basically a thick fencing wire attached to the top of a building and connected to the ground. It is designed to attract lightning and earth the electric charge. By directing the flow through the wire, it saves the building from being damaged.</p>
<p>These Franklin rods are required for tall buildings and churches today, but the uncertain factor is how many are needed on each structure.</p>
<p>Furthermore, hundreds of structures are not protected, including shelter sheds in parks. These structures are often made from highly conductive galvanized iron, which itself attracts lightning, and supported by wooden posts.</p>
<p>The new version of Standards Australia for lightning protection recommends such shelters be earthed.</p><img src="https://counter.theconversation.com/content/195549/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr John Lowke was a member of the Standards Australia committee that recommended the change to lightning protection standards.</span></em></p>
Lightning doesn’t travel in a straight line, with many so-called ‘leaders’ coming down from the cloud in a series of jagged steps. Until now, no one has known why.
John Lowke, Adjunct Research Professor of Physics, University of South Australia
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/188862
2022-08-17T13:54:17Z
2022-08-17T13:54:17Z
Why it’s not safe to shower during a thunderstorm
<p>The Met Office has issued several “yellow thunderstorm warnings” for the UK, highlighting the <a href="https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2022/days-of-thunder-ahead-for-some">potential for frequent lightning</a>. While your chance of getting struck by lightning is low, it’s important to know how to stay safe during a thunderstorm. Globally, about 24,000 people each year are <a href="https://www.vaisala.com/sites/default/files/documents/Annual_rates_of_lightning_fatalities_by_country.pdf">killed by lightning</a> and another 240,000 are injured.</p>
<p>Most people are familiar with basic thunderstorm safety, such as avoiding standing under trees or near a window, and not speaking on a corded phone (mobile phones are safe). But did you know you should avoid taking a shower, a bath or washing the dishes during a thunderstorm?</p>
<p>To understand why, you first need to know a bit about how thunderstorms and lightning work.</p>
<p>Two basic elements cause a thunderstorm to thrive: moisture and rising warm air, which of course go hand in hand with summertime. The high temperatures and humidity create large amounts of moist air that rises into the atmosphere, where it can form into a thunderstorm.</p>
<p>Clouds contain millions of water and ice droplets and the interaction of these is what leads to <a href="https://www.weather.gov/safety/lightning-science-electrification">lightning generation</a>. The rising water drops collide with the falling ice drops, passing them a negative charge and leaving themselves with a positive charge. In a thunderstorm, clouds act as enormous Van de Graaff generators, separating the positive and negative charges to create massive charge separations inside the clouds.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/laDmuQFmK3Y?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How a Van de Graaff generator works.</span></figcaption>
</figure>
<p>As thunderclouds move over the Earth, they generate an opposite charge in the ground, and this is what attracts a lighting strike towards the ground. The thunderstorm wants to balance its charges, and it does this by discharging between positive and negative regions. The path of this discharge is usually the one of least resistance, so things that are more conductive (like metal) are more likely to be struck during a storm. </p>
<p>The most useful advice for a thunderstorm is: when thunder roars, go indoors. However, this does not mean you are completely safe from the storm. There are some activities inside that can be almost as risky as staying outside in the storm. </p>
<h2>Path of least resistance</h2>
<p>Unless you’re sitting in a bath outside or showering in the rain, you’re incredibly unlikely to be struck by lightning. But if lightning strikes your house, the electricity would follow the path of least resistance to the ground. Things such as metal wires or water in your pipes provide a convenient conductive path for the electricity to follow to the ground. </p>
<p>The shower provides both of those things (water and metal), making it an ideal path for the electricity to take. It could turn that nice relaxing shower into something much less relaxing. The US <a href="https://www.cdc.gov/disasters/lightning/safetytips.html#:%7E:text=Stay%20away%20from%20open%20spaces,strike%20the%20tallest%20object%20around.">Centers for Disease Control and Prevention</a> strongly encourage people to avoid all water-based activities during a thunderstorm – even the washing up – to reduce your risk of a strike. </p>
<p>There are other risks to look out for during a thunderstorm. One that may not seem obvious is leaning on a concrete wall. While concrete itself isn’t that conductive, if it has been reinforced with metal beams (called “rebar”), these can provide a conductive path for the lightning. Also avoid using anything plugged into an electrical outlet (computers, TVs, washing machines, dishwashers) as all of these can provide pathways for the lightning strike to take. </p>
<p>As a rule of thumb, if you can hear thunder in the distance, then you’re close enough to the storm to have lightning reach you, even if there is no rain. Lightning strikes can happen as far as ten miles away from the parent storm. Typically, half an hour after hearing that final thunderclap is a safe time to venture back into the shower. Thunderstorms usually like to save a big one for the end, and you don’t want to end up part of the fireworks!</p><img src="https://counter.theconversation.com/content/188862/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Rawlings 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>
Lightning kills 24,000 people each year. Here’s how to stay safe during an electrical storm.
James Rawlings, Physics Lecturer, Nottingham Trent University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/186453
2022-07-06T12:18:51Z
2022-07-06T12:18:51Z
Alaska on fire: Thousands of lightning strikes and a warming climate put Alaska on pace for another historic fire season
<figure><img src="https://images.theconversation.com/files/472711/original/file-20220706-19-hjye2.jpg?ixlib=rb-1.1.0&rect=0%2C108%2C4031%2C2909&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A large tundra fire burned near St. Mary's, Alaska, on June 13, 2022.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/blmalaskafireservice/52157039455/in/album-72177720299701992/">BLM Alaska Fire Service/Incident Management Team/John Kern</a></span></figcaption></figure><p><em>Alaska is on pace for another historic wildfire year, with its fastest start to the fire season on record. By mid-June 2022, <a href="https://alaskabeacon.com/briefs/climate-change-cited-as-factor-in-early-alaska-wildfire-milestone/">over 1 million acres</a> had burned. By early July, that number was well <a href="https://akfireinfo.com/2022/07/03/alaska-surpasses-2-million-acres-burned">over 2 million</a> acres, more than twice the size of a <a href="https://fire.ak.blm.gov/content/aicc/Statistics%20Directory/Alaska%20Fire%20History%20Chart%20with%20Data.xls">typical Alaska fire season</a>.</em></p>
<p><em>We asked Rick Thoman, <a href="https://news.uaf.edu/expertsguide/rick-thoman/">a climate specialist</a> at the International Arctic Research Center in Fairbanks, why Alaska is seeing so many large, intense fires this year and how the region’s fire season is changing.</em></p>
<h2>Why is Alaska seeing so many fires this year?</h2>
<p>There isn’t one simple answer.</p>
<p>Early in the season, southwest Alaska was one of the few areas in the state with <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/ak/snow/">below normal snowpack</a>. Then we had a warm spring, and southwest Alaska dried out. An outbreak of thunderstorms there in late May and early June provided the spark. </p>
<p>Global warming has also increased the amount of fuels – the plants and trees that are available to burn. More fuel means <a href="https://www.doi.gov/wildlandfire/fuels">more intense fires</a>.</p>
<p>So, the weather factors – the warm spring, low snowpack and unusual thunderstorm activity – combined with <a href="https://www.ncei.noaa.gov/cag/statewide/time-series/50/tavg/12/12/1895-2022?base_prd=true&begbaseyear=1901&endbaseyear=2000">multidecade warming</a> that has allowed vegetation to grow in southwest Alaska, together fuel an active fire season. </p>
<figure class="align-center ">
<img alt="Chart shows 2022 starting faster than any of the other large fire years on record and on pace with the 2015 fire season." src="https://images.theconversation.com/files/473047/original/file-20220707-26-cube2k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473047/original/file-20220707-26-cube2k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473047/original/file-20220707-26-cube2k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473047/original/file-20220707-26-cube2k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473047/original/file-20220707-26-cube2k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=452&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473047/original/file-20220707-26-cube2k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=452&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473047/original/file-20220707-26-cube2k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=452&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">2022 is among Alaska’s busiest fire seasons in over 30 years of records.</span>
<span class="attribution"><a class="source" href="https://akfireinfo.com/">AICC</a></span>
</figcaption>
</figure>
<p>In Alaska’s interior, much of the area has been <a href="https://droughtmonitor.unl.edu/data/png/20220628/20220628_ak_trd.png">abnormally dry</a> since late April. So, with the lightning storms, it’s no surprise that we’re now seeing many fires in the region. The interior had <a href="https://twitter.com/AlaskaWx/status/1544000284820590594">about 18,000 strikes</a> over two days in early July. </p>
<h2>Are lightning storms like this becoming more frequent?</h2>
<p>That’s the million-dollar question.</p>
<p>It’s actually a two-part question: Are thunderstorms occurring more often now in places that used to rarely get them? I think the answer is unequivocally “yes.” Is the total number of strikes increasing? We don’t know, because the networks tracking lightning strikes today are far more sensitive than in the past.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/472624/original/file-20220705-5022-ahqp5v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472624/original/file-20220705-5022-ahqp5v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=525&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472624/original/file-20220705-5022-ahqp5v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=525&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472624/original/file-20220705-5022-ahqp5v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=525&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472624/original/file-20220705-5022-ahqp5v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=660&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472624/original/file-20220705-5022-ahqp5v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=660&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472624/original/file-20220705-5022-ahqp5v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=660&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Lightning strikes in Alaska July 2-4, 2022.</span>
<span class="attribution"><a class="source" href="https://twitter.com/AlaskaWx/status/1544000284820590594">AICC</a></span>
</figcaption>
</figure>
<p>Thunderstorms in Alaska are different from in most of the lower 48 in the sense that they tend to not be associated with weather fronts. They’re what meteorologists call <a href="https://doi.org/10.1175/BAMS-D-16-0064.1">air mass or pulse thunderstorms</a>. They’re driven by two factors: the available moisture in the lower atmosphere and the temperature difference between the lower and middle atmospheres.</p>
<p>In a warming world, <a href="https://theconversation.com/the-water-cycle-is-intensifying-as-the-climate-warms-ipcc-report-warns-that-means-more-intense-storms-and-flooding-165590">air can hold more moisture</a>, so you can get intense storms. In interior Alaska, we’re getting thunderstorms more frequently. For example, the number of days with thunderstorms <a href="https://uaf-accap.org/air-temperature/other-climate-weather-graphics/">recorded at the Fairbanks Airport</a> show a clear increase. Indigenous elders also agree that they’re seeing thunderstorms more often.</p>
<h2>You mentioned hotter fires. How are wildfires changing?</h2>
<p>Wildfire is part of the natural ecosystem in the Boreal north, but the fires we’re getting now are not the same as the fires that were burning 150 years ago.</p>
<p>More fuel, more lightning strikes, higher temperatures, lower humidity – they combine to fuel fires that burn hotter and burn deeper into the ground, so rather than just scorching the trees and burning the undergrowth, they’re consuming everything, and you’re left with this moonscape of ash.</p>
<p><a href="https://www.pnas.org/doi/10.1073/pnas.2024872118">Spruce trees</a> that <a href="https://beta.nsf.gov/news/black-spruce-trees-struggle-regenerate-amid-more-frequent-arctic-fires">rely on fire</a> to burst open their cones can’t reproduce when the fire turns those cones to ash. People who have been out in the field fighting fire for decades say they’re amazed at the amount of destruction they see now. </p>
<figure class="align-center ">
<img alt="Firefighters in tall grass silhouetted by flames in the trees beyond." src="https://images.theconversation.com/files/472686/original/file-20220706-17-z1n7gv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472686/original/file-20220706-17-z1n7gv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=779&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472686/original/file-20220706-17-z1n7gv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=779&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472686/original/file-20220706-17-z1n7gv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=779&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472686/original/file-20220706-17-z1n7gv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=979&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472686/original/file-20220706-17-z1n7gv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=979&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472686/original/file-20220706-17-z1n7gv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=979&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fire crews walk through tall vegetation as they conduct defensive burning against a large complex of fires near Lime Village, Alaska. The group of fires totaled more than 780,000 acres on July 5, 2022.</span>
<span class="attribution"><a class="source" href="https://akfireinfo.com/2022/07/05/high-humidity-and-defensive-burning-reducing-lime-complex-fire-spread/">Bryan Quimby/Alaska Incident Management Team</a></span>
</figcaption>
</figure>
<p>So while fire has been natural here for tens of thousands of years, the fire situation has changed. The frequency of million-acre fires in Alaska <a href="https://uaf-iarc.org/alaskas-changing-environment/">has doubled since before 1990</a>.</p>
<h2>What impact are these fires having on the population?</h2>
<p>The most common impact on humans is smoke.</p>
<p>Most wildfires in Alaska aren’t burning through heavily populated areas, though that does happen. When you’re burning 2 million acres, you’re burning a lot of trees, and so you’re putting a lot of smoke into the air, and it travels long distances.</p>
<p>In early July, we saw explosive <a href="https://alaskabeacon.com/briefs/alaska-wildfires-and-their-smoke-force-closures-cancelations-and-exacuations/">wildfire activity north of Lake Iliamna</a> in southwest Alaska. The winds were blowing from the southeast then, and dense smoke was transported hundreds of miles. In Nome, 400 miles away, the air quality index at the hospital <a href="https://twitter.com/AlaskaWx/status/1542899411080007681">exceeded 600 parts per million</a> for PM2.5, fine particulate matter that <a href="https://ww2.arb.ca.gov/resources/inhalable-particulate-matter-and-health">can trigger asthma</a> and harm the lungs. Anything <a href="https://www.airnow.gov/aqi/aqi-basics/">over 150 ppm is unhealthy</a>, and over 400 ppm is considered hazardous.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/472631/original/file-20220705-23-jymkxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472631/original/file-20220705-23-jymkxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472631/original/file-20220705-23-jymkxn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472631/original/file-20220705-23-jymkxn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472631/original/file-20220705-23-jymkxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472631/original/file-20220705-23-jymkxn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472631/original/file-20220705-23-jymkxn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fires burning on June 10, 2022, seen from a satellite.</span>
<span class="attribution"><span class="source">NASA Earth Observatory</span></span>
</figcaption>
</figure>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/472632/original/file-20220705-13-vslisk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472632/original/file-20220705-13-vslisk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472632/original/file-20220705-13-vslisk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472632/original/file-20220705-13-vslisk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472632/original/file-20220705-13-vslisk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472632/original/file-20220705-13-vslisk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472632/original/file-20220705-13-vslisk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A close-up view shows where people were evacuated near one of the region’s largest tundra fires on record.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/149973/alaska-ablaze">NASA Earth Observatory</a></span>
</figcaption>
</figure>
<p>There are other risks. When fires threaten rural Alaska communities, <a href="https://www.alaskapublic.org/2022/06/10/vulnerable-residents-flown-out-of-st-marys-and-pitkas-point-as-major-tundra-fire-closes-in/">as one did near St. Mary’s</a> in June 2022, evacuating can mean flying people out.</p>
<p>Worsening fire seasons also put pressure on firefighting resources everywhere. Firefighting is expensive, and Alaska counts on fire crews, planes and equipment from the lower 48 states and other countries. In the past, when Alaska had a big fire season, crews would come up from the lower 48 because their fire season was typically much later. Now, wildfire season there is all year, and there are fewer movable resources available.</p><img src="https://counter.theconversation.com/content/186453/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rick Thoman does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Fires today are hotter and more destructive, thanks in part to a warming climate.
Rick Thoman, Alaska Climate Specialist, University of Alaska Fairbanks
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/179833
2022-03-24T19:03:54Z
2022-03-24T19:03:54Z
Tasmania’s forests are burning more as climate change dries them out. Our old tools can’t fight these new fires
<p>The summer of 2021-22 will be remembered for the extraordinarily destructive flooding across eastern Australia. At the same time, however, western Tasmania was experiencing extreme drought, with some areas receiving their <a href="http://www.bom.gov.au/climate/maps/rainfall/?variable=rainfall&map=drought&period=3month&region=ta&year=2022&month=02&day=28">lowest rainfall on record</a>. </p>
<p>This drought fits an observed <a href="https://climatefutures.org.au/technical-reports/general-climate-impacts-technical-report-2/">drying trend</a> across the state, which will worsen due to climate change. This is very bad news for the ancient wilderness in the state’s World Heritage Area, where the lineage of some tree species stretch back 150 million years to the supercontinent Gondwana. </p>
<p>The drying trend has seen a <a href="https://www.mdpi.com/2571-6255/1/3/38">steady increase</a> in bushfires ignited by lightning, imperilling the survival of Tasmania’s Gondwanan legacy, and raising <a href="https://link.springer.com/chapter/10.1007/978-3-030-71330-0_6">profound fire management challenges</a>. Indeed, climate change means we’re on a learning curve, and the usual practices of managing fire are no longer necessarily fit for purpose. </p>
<p>There is increasing <a href="https://onlinelibrary.wiley.com/doi/10.1111/gcb.15539">scientific recognition</a> of the risk of the Gondanwan ecosystem collapsing from climate change driven fires. A new <a href="https://parks.tas.gov.au/Documents/D21-144017%20Draft%20TWWHA%20Fire%20Management%20Plan.pdf">draft fire management plan</a> outlines key steps to ensure these iconic forests survive for decades to come – and it must receive dedicated funding.</p>
<h2>Tasmania’s drought</h2>
<p>Western Tasmania is one of Australia’s wettest regions, where average annual rainfall can exceed 3 metres. Cool temperatures, year-round rainfall, and complex topography have created fire refugia – landscapes naturally protected from fire. This is why western Tasmania is home to a suite of so-called “living fossils”, such as Huon pines and pencil pines.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/454035/original/file-20220324-23-1ualyvr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/454035/original/file-20220324-23-1ualyvr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/454035/original/file-20220324-23-1ualyvr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/454035/original/file-20220324-23-1ualyvr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/454035/original/file-20220324-23-1ualyvr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/454035/original/file-20220324-23-1ualyvr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/454035/original/file-20220324-23-1ualyvr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/454035/original/file-20220324-23-1ualyvr.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">Pencil pine is one of Tasmania’s tree species with Gondwanan lineage.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The survival of these relic species hangs in a delicate balance. They occur in small patches surrounded by large areas of highly flammable Australian vegetation, such as eucalypts, tea-tree and, within in the World Heritage site, the ubiquitous buttongrass moorland. </p>
<p>The cool moist climate, combined with the skilful, intentional application of fire by Aboriginal people, have conserved ancient, unique trees for millennia. However, the changes in fire patterns following colonialism have caused some Gondwanan <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15031?casa_token=1rYKWG5RhpQAAAAA:dWRlQwDuGWVALqK5ymvLLvRMyM7vuJX3sQVOxOiUm4MnTQFCYTFdGxiwl0S-x9Xx16WLzAc5Mav7Yt2Y">refugia to collapse</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australia-you-have-unfinished-business-its-time-to-let-our-fire-people-care-for-this-land-135196">Australia, you have unfinished business. It's time to let our 'fire people' care for this land</a>
</strong>
</em>
</p>
<hr>
<p>Western Tasmania’s current drought is its worst in 40 years, despite the presence of <a href="https://www.abc.net.au/news/rural/2022-02-07/beekeepers-grapple-with-western-dry-spell/100799136">La Niña</a> – a natural climate phenomenon that brings cool, wet weather to parts of Australia. It has also been one Tasmania’s <a href="https://www.theguardian.com/australia-news/2022/mar/03/tasmania-records-driest-summer-in-40-years-as-la-nina-swings-the-wind-around">hottest summers</a> on record. </p>
<p>Fortunately, the past summer has seen only a few bushfires ignited by lightning. Nonetheless, one of these fires was near the <a href="https://www.abc.net.au/news/2022-02-17/fears-for-ancient-huon-pines-as-fire-sweeps-tasmanian-wilderness/100840254">last remaining stand</a> of unlogged Huon pine forest. </p>
<p>To understand the level of risk to Tasmania’s World Heritage Area, we can look to bushfires in <a href="https://www.mdpi.com/2571-6255/5/2/33">2016 and 2019</a> when massive dry lightning storms ignited fires in remote wilderness areas, threatening ecologically irreplaceable areas such as the <a href="https://parks.tas.gov.au/explore-our-parks/walls-of-jerusalem-national-park">Walls of Jerusalem</a> and <a href="https://parks.tas.gov.au/explore-our-parks/southwest-national-park/mount-anne-circuit">Mt Anne</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/454036/original/file-20220324-22-1guv34o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/454036/original/file-20220324-22-1guv34o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/454036/original/file-20220324-22-1guv34o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/454036/original/file-20220324-22-1guv34o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/454036/original/file-20220324-22-1guv34o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/454036/original/file-20220324-22-1guv34o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/454036/original/file-20220324-22-1guv34o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/454036/original/file-20220324-22-1guv34o.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">The Walls of Jerusalem is an alpine park in northwest Tasmania.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>And let’s not forget, <a href="https://www.abc.net.au/news/2020-07-27/gospers-mountain-mega-blaze-investigation/12472044?nw=0&r=HtmlFragment">the largest fire</a> in the 2019-20 bushfire crisis, which threatened many Blue Mountains towns, was ignited by a lightning strike in a remote and rugged area. </p>
<p>Likewise, the devastating <a href="https://knowledge.aidr.org.au/resources/bushfire-canberra-2003/">2003 Canberra bushfires</a> was caused by lightning strikes in Kosciuszko and Namadgi National Parks. </p>
<p>There can be no doubt effective management of Tasmania’s wilderness will provide protection for nearby towns.</p>
<h2>So what does sustainable fire management look like?</h2>
<p>It’s widely accepted among Australian fire management agencies and conservation groups that aerial firefighting is key to controlling remote bushfires. But there are significant downsides to this approach. </p>
<p>The two most important are the very high costs of using aircraft, and the environmental impacts of <a href="https://www.fire.tas.gov.au/userfiles/AFAC/AFAC_Review.pdf">firefighting chemicals</a>. Some firefighting chemicals can, for instance, change soil chemistry so it favours weed invasion.</p>
<p>Tasmania’s Wilderness World Heritage Area needs a <a href="https://eprints.utas.edu.au/28923/1/05%20Kirkpatrick.pdf">sustainable fire management</a> approach which, crucially, employs and involves Aboriginal people. This would not only benefit the environment, but also enable Aboriginal people in Tasmania to reconnect with important cultural sites. </p>
<p>A sustainable approach is one that reduces the number of large bushfires while also intentionally applies fire to ecosystems and threatened species that require regular burning. For example, the critically endangered <a href="https://birdlife.org.au/bird-profile/orange-bellied-parrot">orange bellied parrot</a> needs regularly burned buttongrass moorland as part of its habitat. </p>
<p>For this to work, we need to create carefully designed fuel breaks across the landscape – strips of land with less vegetation available to burn, which slows bushfires. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/454040/original/file-20220324-13-10n3o3b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/454040/original/file-20220324-13-10n3o3b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/454040/original/file-20220324-13-10n3o3b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/454040/original/file-20220324-13-10n3o3b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/454040/original/file-20220324-13-10n3o3b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/454040/original/file-20220324-13-10n3o3b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/454040/original/file-20220324-13-10n3o3b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/454040/original/file-20220324-13-10n3o3b.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">There are downsides to aerial firefighting, such as releasing toxic chemicals into the environment.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Naturally, such planned burning must consider biodiversity, ensuring fire sensitive plants that can’t bounce back – such as pencil pines and alpine vegetation – are protected. At the same time, we must continue to burn native plants that depend on fire to regenerate. </p>
<p>Protecting biodiversity can be achieved through carefully implementing a practice called “mosaic” burning. This is where small areas are regularly burnt to create a patchwork of habitats so wildlife has a diversity of resources and places to shelter in. </p>
<p>Ultimately, well-designed landscape management will give managers confidence to let some fires run free, rather than attempting costly aerial firefighting campaigns.
By contrast, areas with internationally important natural and cultural values should be the focus of fire protection efforts when bushfires do occur, such as the <a href="https://www.abc.net.au/news/2019-01-07/gell-river-fire-threatens-tasmanian-eucalypt-plantation/10688530">innovative use</a> of sprinklers to protect the shores of Lake Rhona.</p>
<h2>More fire in our future</h2>
<p>The above fire management approaches are outlined in the current draft <a href="https://parks.tas.gov.au/Documents/D21-144017%20Draft%20TWWHA%20Fire%20Management%20Plan.pdf">fire management plan</a> for the World Heritage Area. Realising its objectives will require dedicated, recurrent funding, without which the plan’s goals will remain aspirational. </p>
<p>What’s more, any fire management evaluation going forward must be publicly transparent to see continual improvement. It will also ensure there’s a broader community understanding of the need to make difficult decisions to adapt to climate change-driven bushfires.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/photos-from-the-field-capturing-the-grandeur-and-heartbreak-of-tasmanias-giant-trees-144743">Photos from the field: capturing the grandeur and heartbreak of Tasmania's giant trees</a>
</strong>
</em>
</p>
<hr>
<p>The 2019-20 bushfire crisis that shocked the world has been overwritten by many other subsequent crises, such as the pandemic, flooding, and geopolitical turmoil. </p>
<p>Indeed, the soggy summer in eastern Australia has no doubt engendered a widespread belief bushfires have gone away. They haven’t. The luxuriate growth from the La Niña is priming landscapes across eastern Australia to burn again.</p>
<p>We must keep focus on adapting to bushfires that are being turbo charged by climate change. With serious investment to protect Tasmania’s precious environment, the rest of Australia – and indeed other flammable wildernesses elsewhere in the world – can too learn how to sustainably manage increasingly devastating bushfires.</p><img src="https://counter.theconversation.com/content/179833/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Bowman receives funding from The Australian Research Council, the Tasmanian Government Department Department of Primary Industries, Parks, Water and Environment, the NSW Office of Heritage and Environment, Australia's Nuclear Science and Technology Organisation, and the Natural Disaster Risk Reduction Grants Program.</span></em></p><p class="fine-print"><em><span>Jenny Styger was the fire management officer for the Tasmanian Wilderness World Heritage Area, and wrote the Tasmanian Wilderness World Heritage Area Draft Fire Management Plan. </span></em></p>
Tasmania’s drying climate is seeing more bushfires ignited by lightning strikes. To protect the state’s World Heritage wilderness, we must use sustainable fire management practices.
David Bowman, Professor of Pyrogeography and Fire Science, University of Tasmania
Jenny Styger, Associate at The Fire Centre,, University of Tasmania
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/176353
2022-02-03T19:06:55Z
2022-02-03T19:06:55Z
What does lightning actually do to a tree?
<figure><img src="https://images.theconversation.com/files/444212/original/file-20220203-23-u0xjwm.jpg?ixlib=rb-1.1.0&rect=22%2C0%2C4970%2C3323&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>The <a href="https://www.abc.net.au/news/2021-06-17/tree-storm-damage-wind-event/100216056">huge storms</a> many Australians have experienced recently have damaged or toppled old trees which had withstood the vagaries of our weather for the past century or more. </p>
<p>This is what we can expect as our climate changes, with storm events more frequent, wind speeds stronger and rainfall heavier. These all contribute to trees falling or dropping large branches. </p>
<p>But there’s something you might not think of as linked to climate change. As storms intensify in our new climate, we’re likely to see more lightning strikes. And that means our tallest trees will be hit more often. </p>
<h2>Is lightning always lethal to trees?</h2>
<p>Most of us are used to the rules we were told about lightning and trees from childhood. Don’t shelter under a tree during a thunder storm. Lightning never strikes in the same place twice. </p>
<p>How do these rules apply from the perspective of a tree? Old trees are often the tallest thing around. When lightning strikes, they are more likely to be struck. You’d think a lightning strike would be game over for most trees. In fact, the effects can <a href="https://www.rbgsyd.nsw.gov.au/Stories/2017/What-happens-when-lightning-strikes-a-tree">vary enormously</a>. </p>
<hr>
<figure class="align-center ">
<img alt="Storm striking a tree in the Sydney Botanic Gardens" src="https://images.theconversation.com/files/444231/original/file-20220203-27-fq24g8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/444231/original/file-20220203-27-fq24g8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=696&fit=crop&dpr=1 600w, https://images.theconversation.com/files/444231/original/file-20220203-27-fq24g8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=696&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/444231/original/file-20220203-27-fq24g8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=696&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/444231/original/file-20220203-27-fq24g8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=875&fit=crop&dpr=1 754w, https://images.theconversation.com/files/444231/original/file-20220203-27-fq24g8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=875&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/444231/original/file-20220203-27-fq24g8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=875&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The lightning strike pictured hit a tree in Sydney’s Royal Botanic Gardens.</span>
<span class="attribution"><a class="source" href="https://twitter.com/7NewsSydney/status/943387957813063681?s=20&t=7pY0O0s5I6LeQxjYllqwWQ">Channel 7</a></span>
</figcaption>
</figure>
<hr>
<p>The damage done depends on the tree species, whether it was sheet or forked lightning, how wet it was and where the lightning hits the earth and dissipates. </p>
<p>Strikes can be up to a million volts, generating temperatures up to 20,000°C. For a tree unlucky enough to be hit by one of these events, it’s all over. The sap inside the tree instantly turns to steam, which can cause it to <a href="https://agrilife.org/treecarekit/after-the-storm/understanding-lightning-associated-tree-damage/">literally explode</a>, or lose great strips of wood and bark. It would be an excellent idea not to be under a tree when this happens. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/dry-lightning-has-set-tasmania-ablaze-and-climate-change-makes-it-more-likely-to-happen-again-111264">Dry lightning has set Tasmania ablaze, and climate change makes it more likely to happen again</a>
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<hr>
<p>Trees are not very good conductors of electricity. If the trunk of the tree is very wet from rain, the lightning will course through the water and dust on the trunk down to the earth, causing <a href="https://www.purdue.edu/hla/sites/yardandgarden/when-lightning-strikes-is-the-tree-out-2/">little damage</a> to the tree itself. You can sometimes see the sooty residue left on parts of the tree after a strike like this. You may well notice the tree will appear to be undamaged and continue to grow well. </p>
<p>Sometimes, lightning will <a href="https://www.bartlett.com/resources/lightning-protection.pdf">strike one side</a> of a tree. Such a strike often kills the tree’s living tissues in a strip running along a large branch, vertically down the trunk to the ground, or even ending a metre or two above the ground. You’ll notice the lightning scar on trees like these, as it’s very visible. The wood behind the scar often decays over time, leaving a hollow behind. Trees can often recover from strikes like this, if the scar and decay are not too great. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/444213/original/file-20220203-27-yqtena.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Tree in pieces after lightning strike" src="https://images.theconversation.com/files/444213/original/file-20220203-27-yqtena.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/444213/original/file-20220203-27-yqtena.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=468&fit=crop&dpr=1 600w, https://images.theconversation.com/files/444213/original/file-20220203-27-yqtena.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=468&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/444213/original/file-20220203-27-yqtena.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=468&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/444213/original/file-20220203-27-yqtena.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/444213/original/file-20220203-27-yqtena.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/444213/original/file-20220203-27-yqtena.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Unlucky trees can explode from a strong lightning hit.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>There is a splendid variegated elm growing at Melbourne University’s Burnley Campus which was struck by lightning almost 30 years ago. Many of us thought it would die, but it defied the odds. Over the following years, I observed the long, narrow lightning scar deepening as the wood decayed. As more years passed, its trunk broadened and the scar eventually grew over. If you go past today, you will see no evidence of wounds or scars. But you and I know a secret – its trunk is hollow but strong.</p>
<h2>Lightning can cause unexpected tree deaths well after the strike</h2>
<p>For some trees when there is a small or no lightning scar, the tree appears to be fine only to die suddenly between two and 12 months later. This may be due to the strike causing a serious disruption to the tree’s metabolism or because it’s been unable to fend off fungal disease or insect pests after being weakened by the strike.</p>
<p>If the lightning goes to the earth through the roots, there may well be no symptoms of a strike visible above ground. Underground, it can be a different story, with potentially catastrophic damage to the root system. If the whole root system is damaged, the tree can die quickly, or fail over time as the roots decay. If only some roots have been killed, the tree may decline slowly for no obvious reason.</p>
<p>Some trees do seem more susceptible to lightning than others. I’ve seen a number of pines and other conifers die after a strike, for instance, while many eucalypts and oaks recover and remain healthy. It is possible to install a lightning protection system on a tree, but they’re costly and rarely installed in Australia. </p>
<p>If you know a tree has been struck by lightning, you would be wise to keep an eye on it. Often, the serious damage is not immediately obvious and will <a href="https://americanclimbers.com/when-lightning-hits-a-tree/">only be revealed</a> in the weeks and months ahead. For some trees, the full impact only becomes clear in the following spring when they fail to recover or resume normal growth. An inspection by a qualified arborist would be a good investment. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/an-unexpected-consequence-of-climate-change-heatwaves-kill-plant-pests-and-save-our-favourite-giant-trees-148919">An unexpected consequence of climate change: heatwaves kill plant pests and save our favourite giant trees</a>
</strong>
</em>
</p>
<hr>
<p>You may well need an arborist to help with a related climate change driven threat to trees. That’s wind. In places like Victoria, trees cope with the prevailing winds from the west or north west by developing stronger root and branching systems. But now we’re seeing strong winds and severe storms coming from different directions. </p>
<p>If the wind comes from an unusual direction, a tree can be damaged or fall despite its age and past experience. The storm which pillaged Victoria’s Dandenong Ranges last year toppled many old, strong trees and led to long-lasting power outages because the winds came from a <a href="https://www.theage.com.au/national/victoria/like-hell-on-earth-the-night-the-trees-fell-from-the-sky-20210618-p5823c.html">different direction</a>. An arborist can check if your trees have been weakened by these new threats. </p>
<figure class="align-center ">
<img alt="fallen tree in dandenong ranges" src="https://images.theconversation.com/files/444226/original/file-20220203-1693-ncdk7w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/444226/original/file-20220203-1693-ncdk7w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/444226/original/file-20220203-1693-ncdk7w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/444226/original/file-20220203-1693-ncdk7w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/444226/original/file-20220203-1693-ncdk7w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/444226/original/file-20220203-1693-ncdk7w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/444226/original/file-20220203-1693-ncdk7w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Wild storms saw thousands of trees fall in the Dandenong Ranges last year.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Lightning really does strike twice</h2>
<p>When you think about the rules we were taught about lightning as children, you can see why the main one exists. You do not want to be near a tree during a thunderstorm. </p>
<p>Some rules aren’t quite accurate. The tallest and oldest tree in an area would be very likely to have been hit by lightning, and not just once but often. So yes, lightning can strike twice in the same place. </p>
<p>In fact, lightning is likely to strike in exactly the same place – the top of the tallest tree – every few years until the tree is no longer the tallest around, as other trees grow up and around it. Even for old trees, there is safety in numbers.</p><img src="https://counter.theconversation.com/content/176353/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gregory Moore 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>
Some trees explode into bits when lightning strikes. Some seem fine and die later. But others are unaffected.
Gregory Moore, Doctor of Botany, The University of Melbourne
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/170239
2021-11-03T09:25:11Z
2021-11-03T09:25:11Z
Forensic science is unlocking the mysteries of fatal lightning strikes
<figure><img src="https://images.theconversation.com/files/428469/original/file-20211026-27-1weocut.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lightning storm over Johannesburg, South Africa.</span> <span class="attribution"><span class="source">Dr Carina Schumann, Johannesburg Lightning Research Lab, University of the Witwatersrand.</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>Lightning is one of the most powerful sources of energy in the natural environment. As anyone who has spent time in Johannesburg during the South African summer will attest, there is nothing as spectacular as a Highveld thunderstorm at the end of a long, hot day: the scent of <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/rain/petrichor">petrichor</a>, torrents of cooling rain, booms of thunder and great spears of lightning across the sky.</p>
<p>These storms are awe inspiring – but also dangerous to people, animals and the built environment. <a href="https://journals.sajs.aosis.co.za/index.php/sajs/article/view/740/1074">African countries</a>, among them Zambia and Uganda, have some of the highest lightning fatality rates in the world. In South Africa, more than <a href="https://journals.lww.com/amjforensicmedicine/Abstract/2005/03000/Lightning_Fatalities_on_the_South_African.11.aspx">250 people are killed by lightning annually</a>. </p>
<p>The exact number of deaths isn’t clear, due to under reporting, but estimates from <a href="https://link.springer.com/book/10.1007/978-3-319-77563-0">28 countries</a> suggest there are up to 24,000 lightning fatalities annually worldwide.</p>
<p>Deaths can’t always be definitely attributed to lightning because, while its marks are easy to spot on the skin or in the organs, nobody was sure how to identify its marks on skeletonised remains. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/fEtI2pbtrNo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Lightning storm over Johannesburg, South Africa. Video produced by Patrick Randolph-Quinney (Northumbria University and the University of the Witwatersrand).</span></figcaption>
</figure>
<p>Our research changes this. <a href="https://doi.org/10.1016/j.fsisyn.2021.100206">Our study</a>, published in the journal Forensic Science International: Synergy, represents collaboration between specialists in forensic anthropology, histology, lightning physics, and micro-focus X-ray computed tomography from the universities of the <a href="https://www.wits.ac.za/news/latest-news/research-news/">Witwatersrand</a> in South Africa, <a href="https://www.northumbria.ac.uk/about-us/academic-departments/applied-sciences/research/">Northumbria</a> in the UK, and the <a href="https://www.necsa.co.za/">Nuclear Energy Corporation of South Africa</a>.</p>
<p>This work can help forensic teams understand whether people or animals were the victims of fatal lightning strikes, based solely on an analysis of their skeletons. This may allow an attribution of accidental death in cases where cause is not apparent, and allow experts to build a more complete picture of the true incidence of lightning fatalities.</p>
<h2>Cause and effect</h2>
<p>When a lightning death is suspected, forensic pathologists determine cause of death by looking for signs of lightning trauma in the deceased’s skin and internal organs. </p>
<p>When a body is struck, fatally or not, the immense electrical current can cause cardiac and respiratory arrest, as well as neurological damage. Ear drums may rupture; bones may fracture, and there will be severe electrical burns at entry and exit sites, particularly on the soles of the feet. Lightning can also produce unique markers in the skin, termed <a href="https://www.iflscience.com/health-and-medicine/what-does-it-look-when-person-gets-struck-lightning/">Lichtenberg figures</a>. These are branching or fern-like patterns caused by electrical damage to superficial blood vessels in the skin.</p>
<p>However, when a skeletonised body is recovered, soft tissues are absent; lightning cannot confidently be attributed as the cause of death. </p>
<p>Our research started with a simple question of cause and effect: does lightning leave recognisable traumatic traces or characteristic lesions when passing through the skeleton? If we discovered unidentified human remains in the South African bush, could we determine whether they were the victim of a fatal lightning strike?</p>
<p>We then generated artificial lightning in the laboratory applied directly to human bone samples extracted from donated bodies who had died of natural causes. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ecOSDOPc_Y4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Artificial lightning produced in the lab passing through a block of human bone. Video produced by Patrick Randolph-Quinney (Northumbria University and the University of the Witwatersrand).</span></figcaption>
</figure>
<p><a href="https://www.wits.ac.za/eie/research-groups/johannesburg-lightning-research-lab--wits/">Lightning physicists</a> set up a high-current impulse generator in our lab at the <a href="https://www.wits.ac.za/anatomicalsciences/">Wits Medical School</a> which could deliver up to 15,000 amps to the bone in a few micro seconds.</p>
<p>Generating such high impulse currents allowed us to mimic the effect of lightning passing through the skeleton. Natural lightning can often have significantly higher current levels, but this experimental setup gave us much greater control than trying to somehow place human tissue in the path of a natural lightning strike.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/428293/original/file-20211025-27-pf3epl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/428293/original/file-20211025-27-pf3epl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/428293/original/file-20211025-27-pf3epl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=301&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428293/original/file-20211025-27-pf3epl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=301&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428293/original/file-20211025-27-pf3epl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=301&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428293/original/file-20211025-27-pf3epl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=378&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428293/original/file-20211025-27-pf3epl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=378&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428293/original/file-20211025-27-pf3epl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=378&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Experimental lightning trauma in action. Left image shows bone before current is applied. Middle image is a high-speed capture of the passage of current. Right image is the bone following current passage, with effects of barotrauma showing the splitting apart of bone tissue by internal pressure wave.</span>
<span class="attribution"><span class="source">Nicholas Bacci, School of Anatomical Sciences and Hugh Hunt, Johannesburg Lightning Research Laboratory, University of the Witwatersrand.</span></span>
</figcaption>
</figure>
<h2>Imaging lightning damage</h2>
<p>Once the current was applied, we cut the bone into thin slices and imaged it using optical microscopy and micro-CT. By looking at the bone at a cellular level we saw there was a pattern of damage uniquely caused by short duration lightning current passing through its cells. </p>
<p>This damage took the form of cracks radiating out from the centre of canals in the bone, or jumping irregularly between clusters of cells. The overall pattern of damage looked very different when compared to other high energy trauma, such as that caused by burning in fire. </p>
<p>We saw the same pattern of trauma in animals killed by natural lightning. We compared the human results with bone from a <a href="https://ieeexplore.ieee.org/document/6973330">wild giraffe</a> that was known to have been struck; the pattern of damage was identical even though the micro-structure of human bone is very different from giraffe bone. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/429184/original/file-20211028-28-x5cu0y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/429184/original/file-20211028-28-x5cu0y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1304&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429184/original/file-20211028-28-x5cu0y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1304&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429184/original/file-20211028-28-x5cu0y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1304&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429184/original/file-20211028-28-x5cu0y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1638&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429184/original/file-20211028-28-x5cu0y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1638&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429184/original/file-20211028-28-x5cu0y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1638&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Patterns of micro-trauma and micro-factures caused by the passage of experimentally induced current in human bone (middle) and a known case of fatal natural lightning strike in a juvenile giraffe (bottom). A control sample of human bone (undamaged) is seen in the top panel.</span>
<span class="attribution"><span class="source">Patrick Randolph-Quinney, Forensic Science Research Group, Northumbria University and Tanya Augustine & Nicholas Bacci, School of Anatomical Sciences, University of the Witwatersrand.</span></span>
</figcaption>
</figure>
<h2>The smoking gun</h2>
<p>So, what was the specific mechanism that caused these micro-fractures to form? We think there are two options which, alone or in combination, would produce this damage. </p>
<p>Firstly, the current itself produces a high-pressure shock wave when travelling through the bone. Lightning specialists term this barotrauma: the passage of electrical energy literally blows bone cells apart. </p>
<p>Secondly, bone behaves strangely when placed in an electric field. This is termed a <a href="https://inflammregen.biomedcentral.com/articles/10.1186/s41232-018-0059-8">piezoelectric</a> effect. Collagen, the organic part of bone, is arranged as fibres or fibrils. These fibrils rearrange themselves when a current is applied, causing stress to build up in the mineralised and crystallised component of bone, in turn leading to deformation and cracking.</p>
<p>Both of these mechanisms would cause fractures to form. This unique pattern of micro-trauma was the smoking gun we were looking for. </p>
<p>Our research offers a new tool to study lightning fatality in real-world forensic cases. At a time when global climate change <a href="https://environmentjournal.online/articles/the-future-is-not-forecast-how-lightning-is-affected-by-climate-change/">may be driving increases</a> in the number and severity of thunderstorms and lightning strikes, this tool may sadly have to be called upon regularly in death investigation.</p><img src="https://counter.theconversation.com/content/170239/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas Bacci received funding from the FRC, University of the Witwatersrand and the JJJ Smieszek fellowship, School of Anatomical Sciences, University of the Witwatersrand.</span></em></p><p class="fine-print"><em><span>Tanya Augustine has received funding from the National Research Foundation, Carnegie Corporation Transformation Programme at Wits and the University of the Witwatersrand.</span></em></p><p class="fine-print"><em><span>Patrick Randolph-Quinney 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>
This tool can identify cause of death by fatal lightning strike in skeletonised remains.
Patrick Randolph-Quinney, Associate Professor of Forensic Science, Northumbria University, Newcastle
Nicholas Bacci, Lecturer, School of Anatomical Sciences, University of the Witwatersrand
Tanya Nadine Augustine, Senior Lecturer, University of the Witwatersrand
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/166222
2021-10-01T12:12:13Z
2021-10-01T12:12:13Z
Monsoons make deserts bloom in the US Southwest, but climate change is making these summer rainfalls more extreme and erratic
<figure><img src="https://images.theconversation.com/files/423923/original/file-20210929-14-jky5f7.jpg?ixlib=rb-1.1.0&rect=34%2C0%2C3888%2C2584&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lightning during a monsoon storm in southern Arizona, Saguaro National Park.</span> <span class="attribution"><a class="source" href="https://photolib.noaa.gov/Collections/National-Weather-Service/Other/emodule/627/eitem/17721">Pete Gregoire, NOAA</a></span></figcaption></figure><p>If you’ve never lived in or visited the U.S. Southwest, you might picture it as a desert that is always hot and dry. But this region experiences a monsoon in the late summer that produces thunderstorms and severe weather, much like India’s famous <a href="https://www.britannica.com/science/Indian-monsoon">summer deluges</a>.</p>
<p>And this year, it generated a lot of rain.</p>
<p>July 2021 was the wettest month since record keeping started at the Tucson, Arizona, airport in 1895, with <a href="https://www.wrh.noaa.gov/twc/monsoon/monsoon.php">8.06 inches</a> (205 millimeters) of rainfall – equivalent to 70% of what the city receives in an average year. This year’s monsoon is the third-wettest ever in Tucson, with <a href="https://www.wrh.noaa.gov/twc/monsoon/monsoon.php">12.80 inches</a> (325 millimeters) of rain.</p>
<p>It was completely the opposite in 2020: Tucson had a <a href="https://www.wrh.noaa.gov/twc/climate/monthly/2020.php">dry “non-soon”, with less than 2 inches of rain</a>. These conditions and <a href="https://www.wrh.noaa.gov/twc/climate/monthly/2020.php">record high temperatures</a> fueled Arizona’s <a href="https://www.azcentral.com/story/news/local/arizona-weather/2021/01/27/2020-was-arizonas-worst-wildfire-seasons-decade/4286395001/">largest wildfire season in a decade</a>, including the <a href="https://tucson.com/news/local/one-year-later-researchers-chart-damage-recovery-from-bighorn-fire/article_b8d9bca0-bfef-11eb-878f-2b4fa4e1ae5c.html">Bighorn Fire</a>, which decimated over 60% of the forest in the Catalina Mountains north of Tucson. </p>
<p>Our monsoon system impacts some 20 million people in the Southwest. As researchers studying <a href="https://scholar.google.com/citations?view_op=list_works&hl=en&user=bV991b0AAAAJ">water</a> and <a href="https://scholar.google.com/citations?user=ERu_i_kAAAAJ&hl=en">climate</a>, we investigate monsoon prediction, which is becoming more complicated due to climate change. Understanding monsoons is critical for educating communities about their <a href="https://storymaps.arcgis.com/stories/a3d5f96dfde449908597a691eda0ef82">benefits and risks</a>, and about how to stay safe from effects like flash flooding.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/5OzJhagG5bQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">During the North American monsoon season, the dry U.S. Southwest can suddenly turn very wet.</span></figcaption>
</figure>
<h2>From dry to wet</h2>
<p>The word <a href="https://www.wrh.noaa.gov/twc/monsoon/monsoon_whatis.php">monsoon</a> comes from the Arabic word mausim, or season. Its most traditional use is to describe the large-scale wind shift into the Indian subcontinent from the ocean that coincides with intense summer rains there. But monsoons also occur in Africa, Australia and South America, as well as in <a href="https://doi.org/10.1175/1520-0477(1997)078%3C2197:TNAM%3E2.0.CO;2">Mexico and the southwestern U.S.</a>.</p>
<p>Monsoonal circulations carry warm, moist air inland from the ocean, which causes rainfall in the summer season. In the Southwest, this pattern starts when an area of high pressure, called a monsoon ridge, builds over the mountainous areas of Mexico and moves toward the western U.S. </p>
<p>In May and June, when the center of the ridge is directly overhead, the Southwest is very hot and dry. Monsoon rains begin when the warm, moist air moves into the region on the southern side of the ridge. The monsoon in Arizona officially begins June 15 and ends Sept. 30, with most rainfall usually occurring in July and August.</p>
<p>The monsoon has been vital to southwestern ecosystems for <a href="https://doi.org/10.1038/s41561-018-0220-7">thousands of years</a>. Many species have evolved and adapted to <a href="https://www.desertmuseum.org/books/nhsd_summer.php">take advantage of monsoon rains</a>. The first storms signal milkweed plants to bloom, attracting butterflies to lay their eggs. <a href="https://www.researchgate.net/publication/325828487_Notes_on_Reproduction_of_Great_Plains_Toads_Anaxyrus_cognatus_Anura_Bufonidae_from_Southerrn_Arizona">Great Plains toads</a> and <a href="https://doi.org/10.1007/s00442-017-3969-2">red-spotted tadpoles</a> start their reproductive cycles in rain-filled puddles. Cactus fruits and <a href="https://news.arizona.edu/story/bug-bonanza-7-big-colorful-critters-try-spot-monsoon-season">insects</a> provide food for hummingbirds, white-winged doves and many other birds and animals.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/423924/original/file-20210929-16-ncozqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Flowers in a meadow under blue skies." src="https://images.theconversation.com/files/423924/original/file-20210929-16-ncozqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/423924/original/file-20210929-16-ncozqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/423924/original/file-20210929-16-ncozqx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/423924/original/file-20210929-16-ncozqx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/423924/original/file-20210929-16-ncozqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/423924/original/file-20210929-16-ncozqx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/423924/original/file-20210929-16-ncozqx.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">Wildflowers blooming near Flagstaff, Ariz., on Aug. 26, 2021, during an intense monsoon season.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/SouthwestMonsoon/9170d798fdc7456e991c413d5f2ab373/photo">AP Photo/ Felicia Fonseca</a></span>
</figcaption>
</figure>
<h2>Floods in the desert</h2>
<p>Monsoon thunderstorms occur when clouds develop over mountains during the day, producing rain in the afternoon and early evening. They create unique and severe dangers in the desert environment. </p>
<p>Flash flooding occurs when dry soil can’t quickly absorb short-lived, high-intensity downpours. Washes and arroyos – drainage channels that are dry except during heavy rainstorms – can turn into raging currents within minutes, strong enough to carry away cars and people.</p>
<p>Strong thunderstorms can generate microbursts – strong surface winds that gust near hurricane force. They may also trigger dust storms known as <a href="https://www.britannica.com/science/haboob">haboobs</a> – giant walls of dust a mile or more high that reduce visibility to near zero. </p>
<p>The dry, gusty thunderstorms that herald the beginning of the monsoon can start and spread wildfires. One of these storms ignited the infamous <a href="https://sites.google.com/site/yarnellreport/">Yarnell Hill Fire</a> in June 2013, which killed 19 firefighters. Monsoon rains on fire burn scars can trigger mud and debris flows, compounding the initial wildfire damage.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1420967415618281481"}"></div></p>
<p>The atmospheric circulation pattern in July and August 2021 was <a href="https://doi.org/10.1175/1520-0434(1995)010%3C0763:LSPAWS%3E2.0.CO;2">especially favorable for an active monsoon and severe weather</a> in the Southwest. Most of southern Arizona experienced torrential rains over multiple days and weeks. These storms caused <a href="https://twitter.com/WeatherNation/status/1415415808348639234">flash flooding</a>, <a href="https://twitter.com/WeatherNation/status/1413845467012780035">high winds</a>, <a href="https://twitter.com/lorigraceaz/status/1414045200456978433">dust storms</a>, <a href="https://twitter.com/PriscillaCasper/status/1420913070721835015">mud and debris flows</a> and <a href="https://twitter.com/AsteroidDave/status/1417700968876048389">heavy lightning</a>. Emergency responders carried out <a href="https://twitter.com/TucsonFireDept/status/1428499063771598854">almost 100 swift-water rescues in Tucson</a>. Forecasters <a href="https://climas.arizona.edu/podcast/sept-2021-southwest-climate-podcast-generational-monsoon-over">in Phoenix issued more than 100 flash flood warnings in August</a>.</p>
<p>This year’s record monsoon also brought benefits. It replenished local water supplies throughout Arizona, which is in an <a href="https://twitter.com/DroughtGov/status/1433529357943795712">intensive long-term drought</a>. In the Tucson Basin, the monsoon generated <a href="https://new.azwater.gov/sites/default/files/Tucson%20Model%20Report_No_24_v2_1.pdf">sustained flows in tributaries of the Santa Cruz River</a>, which <a href="https://www.kgun9.com/absolutely-az/understanding-monsoon-and-where-all-the-rainwater-goes">helped to recharge groundwater</a>. Water reserves <a href="https://www.abc15.com/weather/impact-earth/srp-lake-levels-up-thanks-to-wet-monsoon">rose by 5%</a> in reservoirs managed by the Salt River Project, which supplies water to more then 2 million people in central Arizona, at a time when others elsewhere in the West are <a href="https://theconversation.com/as-colorado-river-basin-states-confront-water-shortages-its-time-to-focus-on-reducing-demand-165646">dropping to record lows</a>.</p>
<p>Monsoon rains also brought the Sonoran desert back to life, including areas where the 2020 <a href="https://www.washingtonpost.com/climate-solutions/interactive/2021/saguaro-cactus-climate-change/">Bighorn fire killed thousands of Saguaros</a>. </p>
<h2>The future of the monsoon</h2>
<p>Forecasting the monsoon and how it may change is challenging. High-resolution atmospheric models that explicitly simulate individual thunderstorms, including our <a href="http://www.atmo.arizona.edu/?id=wrf&section=weather">own regional modeling system at University of Arizona</a>, have greatly improved daily weather forecasts in recent decades. But it is still virtually impossible to predict exactly when and where storms will occur on a given day.</p>
<p>It’s also essentially impossible to forecast months in advance how strong monsoon rains will be. This year, long-range forecasts <a href="https://twitter.com/NWSCPC/status/1410313699680690178">didn’t start to trend wet until mid- to late June</a>. Climate change is making monsoon rain more extreme and variable, driven by hotter summers and characterized by <a href="http://dx.doi.org/10.1007/s40641-019-00135-w">less frequent but more intense storms</a>.</p>
<p>If recent years are any indication, our region is already experiencing these effects, with <a href="https://www.climate.gov/news-features/event-tracker/record-breaking-june-2021-heatwave-impacts-us-west">record heat waves</a>, <a href="https://apnews.com/article/ca-state-wire-arizona-fires-wildfires-environment-and-nature-8dcb89fd5ded4c632155c3478d8ba3ee">larger and catastrophic wildfires</a>, and a monsoon that is basically nonexistent one year, then produces record rainfall and severe weather the next. Such shifts are exacerbating people’s exposure to weather and climate extremes in the Southwest. </p>
<p>The big concern is whether a more extreme and erratic monsoon will cause an increase in threshold points of failure – for example, flood control infrastructure that collapses from intense rainfall, or wildfires so devastating that forests can’t recover. Clearly understanding these types of risk is critical to creating a more resilient and sustainable future for the Southwest.</p>
<p>[<em>Over 110,000 readers rely on The Conversation’s newsletter to understand the world.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=100Ksignup">Sign up today</a>.]</p><img src="https://counter.theconversation.com/content/166222/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher L. Castro receives funding from the US Department of Defense's Strategic Environmental Research and Development Program.</span></em></p><p class="fine-print"><em><span>Diana Zamora-Reyes does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Monsoons are weather patterns that bring thunderstorms and heavy rains to hot, dry areas when warm, moist ocean air moves inland. They’re challenging to forecast, especially in a changing climate.
Diana Zamora-Reyes, PhD Candidate in Hydrology, University of Arizona
Christopher L. Castro, Professor of Hydrology and Atmospheric Sciences, University of Arizona
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/157343
2021-03-17T15:27:34Z
2021-03-17T15:27:34Z
Origin of life: lightning strikes may have provided missing ingredient for Earth’s first organisms
<figure><img src="https://images.theconversation.com/files/390104/original/file-20210317-15-aa21co.jpg?ixlib=rb-1.1.0&rect=28%2C22%2C1868%2C997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lightning on early Earth.</span> <span class="attribution"><span class="source"> Lucy Entwisle</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The origin of life on Earth is one of the most complex puzzles facing scientists. It involves not only identifying the numerous chemical reactions that must take place to create a replicating organism, but also finding realistic sources for the ingredients needed for each of the reactions.</p>
<p>One particular problem that has long faced scientists who study the origin of life is the source of the elusive element, phosphorus. Phosphorus is an important element for basic cell structures and functions. For example, it forms the backbone of the double helix structure of DNA and the related molecule RNA.</p>
<p>Though the element was widespread, almost all phosphorus on the early Earth – around 4 billion years ago – was trapped in minerals that were essentially insoluble and unreactive. This means the phosphorus, while present in principle, was not available to make the compounds needed for life. </p>
<p><a href="https://www.nature.com/articles/s41467-021-21849-2">In a new paper</a>, we show lightning strikes would have provided a widespread source of phosphorus. This means lightning strikes may have helped spark life on Earth, and may be continuing to help life start on other Earth-like planets.</p>
<p>One potential source of phosphorus on the early Earth is the unusual mineral schreibersite, which is found in <a href="https://www.liebertpub.com/doi/10.1089/ast.2005.5.515">small amounts in meteorites</a>. Experiments have shown that <a href="https://doi.org/10.1016/j.gca.2006.12.018">schreibersite can dissolve in water</a>, creating aqueous phosphorus which can react and form a variety of organic molecules important for life. Examples include <a href="https://www.nature.com/articles/srep17198">nucleotides</a>, the building blocks of DNA and RNA, and <a href="https://doi.org/10.1039/C6CP00836D">phosphocholine</a>, a precursor to the lipid molecules that make up the cell membrane.</p>
<p>But there’s another potential source for schreibersite. While studying a glass structure created by a lightning strike called a fulgurite, we found a substantial amount of the unusual phosphorus mineral inside the glass.</p>
<p>If lightning strikes created a large amount of schreibersite, and other reactive phosphorus minerals, then lightning could be an alternate source of the reactive phosphorus needed for life. </p>
<p>To determine if this was the case, we estimated the amount of phosphorus made available by lightning strikes from 4.5 billion years ago, when the Earth formed, to 3.5 billion years ago when we have the earliest fossil evidence of life.</p>
<figure class="align-center ">
<img alt="A fulgurite sample of glass on the ground." src="https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The fulgurite sample.</span>
<span class="attribution"><span class="source">Benjamin Hess</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Our study</h2>
<p>To do this, we needed to estimate three things: the number of fulgurites formed each year; how much phosphorus was in the rocks on early Earth; and how much of that phosphorus is turned into usable phosphorus, by the lightning strikes. </p>
<p>Fulgurites form when lightning strikes the ground, so first we needed to know how much lightning there was. To determine the amount of lightning, we looked at estimates of the amount of CO₂ in the atmosphere on early Earth and estimates of how much lightning there would be on Earth for different amounts of CO₂. The CO₂ in the atmosphere can be used to estimate global temperature, which is a key factor in controlling the frequency of thunderstorms.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/phosphorus-is-vital-for-life-on-earth-and-were-running-low-74316">Phosphorus is vital for life on Earth – and we're running low</a>
</strong>
</em>
</p>
<hr>
<p>We found that, on early Earth, there would have ranged from 100 million to 1 billion lightning strikes a year, with each strike forming one fulgurite. In total, up to 1 quintillion (one followed by 18 zeroes) fulgurites would have formed in the first billion years of Earth’s history.</p>
<p>For the second factor, we know early Earth would have likely been dominated by rocks that are similar to the basalts that make up volcanic islands like Hawaii. We used the phosphorus content in some of these <a href="https://doi.org/10.1016/S0009-2541(01)00363-1">preserved rocks</a> that are over 3.5 billion years old to determine an average phosphorus content.</p>
<p>Finally, we used our fulgurite and other published fulgurite studies to estimate of how much schreibersite, or similar forms of phosphorus, would have been made available by lightning strikes. </p>
<p>Combining all these factors we calculated lightning strikes made upwards of 10,000kg of phosphorus available for organic reactions every year.</p>
<p>Based on the best of our knowledge of early Earth, lightning probably provided as much reactive phosphorus as meteorites did around the time of the origin of life, approximately 3.5 billion years ago. Therefore, lightning strikes, along with meteorite impacts, very likely provided the phosphorus needed for the emergence of life on Earth. </p>
<h2>Life on exoplanets</h2>
<p>Our research also highlights a new source of the phosphorus needed for life to emerge on other Earth-like planets. </p>
<p>Lightning strikes are a more sustainable source of phosphorus than meteorite impacts. The abundance of large meteorites in a solar system decreases exponentially over time as the leftover material in the system collides with planets. </p>
<p>So, while meteorites provide substantial usable phosphorus for life early in a planet’s history, they decrease fairly rapidly in abundance. Lightning strikes, however, are relatively constant through time.</p>
<p>Our work helps expand the conditions in which life can form on other planets in our solar system and beyond. If any planet has an active, lightning-rich atmosphere, then the phosphorus needed for life will be available any time.</p><img src="https://counter.theconversation.com/content/157343/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
Lightning strikes may have helped spark life on Earth, and may be continuing to help life start on other Earth-like planets.
Benjamin Hess, PhD Candidate, Earth & Planetary Sciences, Yale University
Jason Harvey, Associate Professor of Geochemistry, University of Leeds
Sandra Piazolo, Professor in Structural Geology and Tectonics, University of Leeds
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/151912
2020-12-18T00:06:45Z
2020-12-18T00:06:45Z
Open data shows lightning, not arson, was the likely cause of most Victorian bushfires last summer
<figure><img src="https://images.theconversation.com/files/375681/original/file-20201217-23-x2y286.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C4920%2C3260&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Tracy Nearmy/AAP</span></span></figcaption></figure><p>As last summer’s horrific bushfires raged, so too did debate about what caused them. Despite the prolonged drought and ever worsening climate change, some people sought to blame the fires largely on arson. </p>
<p><a href="https://www.abc.net.au/news/2020-01-15/is-arson-mostly-to-blame-for-the-bushfire-crisis/11865724">Federal Coalition MPs</a> were among those pushing the arsonist claim. And on Twitter, a fierce <a href="https://www.abc.net.au/news/2020-01-08/fires-misinformation-being-spread-through-social-media/11846434">hashtag war</a> broke out: “#ClimateEmergency” vs “#ArsonEmergency”. </p>
<p>Fire authorities <a href="https://www.abc.net.au/news/2020-01-11/australias-fires-reveal-arson-not-a-major-cause/11855022">rejected</a> the arson claims, saying most fires were thought to be caused by lightning.</p>
<p>We dug into open data resources to learn more about the causes of last summer’s bushfires in Victoria, and further test the arson claim. <a href="https://github.com/TengMCing/bushfire-conversation">Our analysis</a> suggests 82% of the fires can be attributed to lightning, 14% to accidents and 1% to burning off. Only 4% can be attributed to arson.</p>
<figure class="align-center ">
<img alt="Lightning in the sky" src="https://images.theconversation.com/files/375687/original/file-20201217-21-11r8xyy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/375687/original/file-20201217-21-11r8xyy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/375687/original/file-20201217-21-11r8xyy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/375687/original/file-20201217-21-11r8xyy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/375687/original/file-20201217-21-11r8xyy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/375687/original/file-20201217-21-11r8xyy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/375687/original/file-20201217-21-11r8xyy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Lightning, not arson, caused most Victorian bushfires last summer.</span>
<span class="attribution"><span class="source">Twitter</span></span>
</figcaption>
</figure>
<h2>What we did</h2>
<p>We started with hotspots data taken from the Himawari-8 satellite, which shows heat source locations over time and space, in almost real time. We omitted hotspots unlikely to be bushfires, and used a type of data mining called “<a href="https://link.springer.com/article/10.1007/s10462-019-09736-1">spatiotemporal clustering</a>” – where time dimension is introduced to geographic data – to estimate ignition time and location.</p>
<p>We supplemented this with data from other sources: temperature, moisture, rainfall, wind, sun exposure, fuel load, as well as distance to camp sites, roads and Country Fire Authority (CFA) stations. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/bushfires-bots-and-arson-claims-australia-flung-in-the-global-disinformation-spotlight-129556">Bushfires, bots and arson claims: Australia flung in the global disinformation spotlight</a>
</strong>
</em>
</p>
<hr>
<p>Victoria’s Department of Environment, Land, Water and Planning (DELWP) holds historical data on bushfire ignition from 2000 to the 2018-19 summer. The forensic research required to determine fire cause is laborious, and remotely sensed data from satellites may be useful and more immediate. </p>
<p>By training our model on the historical data, we can more immediately predict causes of last summer’s fires detected from satellite data. (Note: even though we were analysing events in the past, we use the term “predict” because authorities have not released official data.)</p>
<p>DELWP’s data attributes 41% of fires to lightning, 17% to arson, 34% to accidents and 7% to hazard reduction or back burning which escaped containment lines (which our analysis refers to as burning off).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/374356/original/file-20201211-14-15tlwp6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/374356/original/file-20201211-14-15tlwp6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=287&fit=crop&dpr=1 600w, https://images.theconversation.com/files/374356/original/file-20201211-14-15tlwp6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=287&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/374356/original/file-20201211-14-15tlwp6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=287&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/374356/original/file-20201211-14-15tlwp6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=361&fit=crop&dpr=1 754w, https://images.theconversation.com/files/374356/original/file-20201211-14-15tlwp6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=361&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/374356/original/file-20201211-14-15tlwp6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=361&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Causes of fires from 2000-2019. Lightning is most common cause. The number of fires is increasing, and this is mostly due to accidents.</span>
<span class="attribution"><span class="source">Own work</span></span>
</figcaption>
</figure>
<p>To make predictions for the 2019-20 bushfires, we needed an accurate model for causes in the historical data. We trained the model to predict one of four causes – lightning, accident, arson, burning off – using a machine learning algorithm. </p>
<p>The model performed well on the historical data: 75% overall accuracy, 90% accurate on lightning, 78% for accidents, and 54% for arson (which was mostly confused with accident, as would make sense).</p>
<p>The most important contributors to distinguishing between lightning and arson (or accident) ignition were distance to CFA stations, roads and camp sites, and average wind speed. </p>
<p>As might be expected, smaller distances to CFA stations, roads and camp sites, and higher than average winds, meant the fire was most likely the result of arson or accident. In the case of longer distances, where bush would have been largely inaccessible to the public, lightning was predicted to be the cause. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/374358/original/file-20201211-15-1u87nv5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/374358/original/file-20201211-15-1u87nv5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=290&fit=crop&dpr=1 600w, https://images.theconversation.com/files/374358/original/file-20201211-15-1u87nv5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=290&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/374358/original/file-20201211-15-1u87nv5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=290&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/374358/original/file-20201211-15-1u87nv5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=365&fit=crop&dpr=1 754w, https://images.theconversation.com/files/374358/original/file-20201211-15-1u87nv5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=365&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/374358/original/file-20201211-15-1u87nv5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=365&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Spatial distribution of causes of fires from 2000-2019, and predictions for 2019-2020 season.</span>
<span class="attribution"><span class="source">Own work</span></span>
</figcaption>
</figure>
<h2>What we found</h2>
<p>Our model predicted that 82% of Victoria’s fires in the summer of 2019-2020 were due to lightning. Most fires were located in densely vegetated areas inaccessible by road – similar to the historical locations. (The percentage is double that in the historical data, though, probably because the satellite hotspot data can see fire ignitions in locations inaccessible to fire experts).</p>
<p>All fires in February 2020 were predicted to be due to lightning. Accident and arson were commonly predicted causes in March, and early in the season. Reassuringly, ignition due to burning off was predicted primarily in October 2019, prior to the fire restrictions. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/374360/original/file-20201211-19-1mgoqlk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/374360/original/file-20201211-19-1mgoqlk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=296&fit=crop&dpr=1 600w, https://images.theconversation.com/files/374360/original/file-20201211-19-1mgoqlk.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=296&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/374360/original/file-20201211-19-1mgoqlk.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=296&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/374360/original/file-20201211-19-1mgoqlk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=372&fit=crop&dpr=1 754w, https://images.theconversation.com/files/374360/original/file-20201211-19-1mgoqlk.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=372&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/374360/original/file-20201211-19-1mgoqlk.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=372&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Spatio-temporal distribution of cause predictions for 2019-2020 season. Reassuringly, fires due to burning off primarily occurred in October, prior to fire restrictions. February fires were all predicted to be due to lightning.</span>
<span class="attribution"><span class="source">Own work</span></span>
</figcaption>
</figure>
<h2>Quicker fire ignition information</h2>
<p>Our analysis used open-data and open-source software, and could be applied to fires elsewhere in Australia. </p>
<p>This analysis shows how we can quickly predict causes of bushfires, using satellite data combined with other information. It could reduce the work of fire forensics teams, and provide more complete fire ignition data in future.</p>
<p>The code used for the analysis can be found <a href="https://github.com/TengMCing/bushfire-conversation">here</a>. Explore the historical fire data, predictions for 2019-2020 fires, and a fire risk map for Victoria using <a href="https://ebsmonash.shinyapps.io/VICfire/">this app</a>.</p>
<hr>
<p><em>This analysis is based on thesis research by Monash University Honours student Weihao Li. She was supervised by the author, and former Principal Inventive Scientist at AT&T Labs Research, Emily Dodwell. The Australian Centre of Excellence for Mathematical and Statistical Frontiers supported Emily’s travel to Australia to start this project. The full analysis is available <a href="https://github.com/TengMCing/bushfire-conversation">here</a>.</em></p>
<p><a href="https://bushfires2020.netlify.app"><img src="https://cdn.theconversation.com/static_files/files/1103/Explore.gif?1594552012" width="100%"></a></p><img src="https://counter.theconversation.com/content/151912/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dianne Cook receives funding from the Australian Centre of Excellence for Mathematical and Statistical Frontiers. </span></em></p>
The method, using satellite data and other information, could reduce the work of fire forensics teams after bushfires.
Dianne Cook, Professor of Business Analytics, Monash University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/144904
2020-08-25T12:23:19Z
2020-08-25T12:23:19Z
Extreme wildfires can create their own dangerous weather, including fire tornadoes – here’s how
<figure><img src="https://images.theconversation.com/files/354215/original/file-20200822-20-19xko0w.jpg?ixlib=rb-1.1.0&rect=4%2C17%2C2968%2C1926&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Extreme wildfires can fuel tornadoes, creating erratic and dangerous conditions for firefighters.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/firefighting-helicopter-makes-a-water-drop-next-to-a-small-news-photo/167983094">David McNew/Getty Images</a></span></figcaption></figure><p>It might sound like a bad movie, but extreme wildfires can create their own weather – including fire tornadoes.</p>
<p>It happened in California as a heat wave helped to fuel hundreds of wildfires across the region, many of them sparked by lightning. One fiery funnel cloud on Aug. 15 was so powerful, the National Weather Service issued what’s believed to be its first <a href="http://mesonet.agron.iastate.edu/wx/afos/p.php?pil=TORREV&e=202008152135">fire tornado warning</a>.</p>
<p>So, what has to happen for a wildfire to get so extreme that it spins off tornadoes?</p>
<p>As <a href="https://scholar.google.com/citations?user=HCfUlVIAAAAJ&hl=en">professors who study</a> <a href="https://scholar.google.com/citations?user=PHyhP_AAAAAJ&hl=en">wildfires and weather</a>, we can offer some insights.</p>
<h2>How extreme fire conditions form</h2>
<p>Fires have three basic elements: heat, fuel and oxygen. </p>
<p>In a wildland fire, a heat source ignites the fire. Sometimes that ignition source is a car or power line or, as the West saw in mid-August, lightning strikes. Oxygen then reacts with dry vegetation to <a href="https://www.nps.gov/articles/wildland-fire-behavior.htm#:%7E:text=The%20Fire%20Behavior%20Triangle,and%20their%20influence%20on%20fire">produce heat, ash and gases</a>. How dry the landscape is determines whether the fire starts, how fast it burns and how hot the fire can get. It’s almost as important as wind.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1294927034473500672"}"></div></p>
<p>Fire weather conditions get extreme when high temperatures, low humidity and strong winds combine with dead and live vegetation to produce difficult-to-fight, fast-spreading wildfires.</p>
<p>That combination is exactly what the West has been seeing. A wet winter fed the growth of grasses that now cover large areas of wildland in the western U.S. Most of this grass is now dead from the summer heat. Combined with other types of vegetation, that leaves lots of <a href="https://www.mdpi.com/2571-6255/3/3/29">fuel for the wildfires</a> to burn. </p>
<p>The remnants of <a href="https://www.nhc.noaa.gov/archive/2020/ELIDA.shtml">Hurricane Elida</a> also played a role. The storm increased moisture and instability in the atmosphere, which triggered thunderstorms further north. The atmosphere over land was pretty dry by then, and even when rain formed at the base of these clouds, it mostly evaporated due to the excessive heat. This led to “dry lightning” that ignited wildfires.</p>
<h2>Wildfires can fuel thunderstorms</h2>
<p><a href="https://doi.org/10.1175/MWR-D-17-0253.1">Fires can also cause convection</a> – hot air rises, and it moves water vapor, gases and aerosols upward. </p>
<p>Wildfires with turbulent plumes can produce a “cumulus” type of cloud, known as pyrocumulus or pyrocumulonimbus. Pyrocumulus clouds are <a href="https://eo.ucar.edu/webweather/cumulus.html">similar to the cumulus clouds</a> people are used to seeing. They develop when hot air carries moisture from plants, soil and air upward, where it cools and condenses. The centers of these “pyroclouds” have strong rising air. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1294751816266047488"}"></div></p>
<p>It’s pretty common, and it’s a warning sign that firefighters could be facing erratic and dangerous conditions on the ground from the indraft of air toward the center of the blaze.</p>
<p>In some cases, the pyroclouds can reach 30,000 feet and produce lightning. There is evidence that pyrocumulus lightning may have ignited new blazes during the devastating fire storm in Australia in 2009 known as “<a href="https://doi.org/10.5194/nhess-20-1497-2020">Black Friday</a>.”</p>
<h2>Where do fire tornadoes come from?</h2>
<p>Similar to the way <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/clouds/low-level-clouds/cumulonimbus">cumulonimbus clouds</a> produce tornadoes, these pyroclouds can produce fire‐generated vortices of ash, smoke and often flames that can get destructive. </p>
<p>A vortex can form because of the intense heat of the fire in an environment with strong winds. This is similar to a strong river flow passing through a depression. The sudden change in the speed of the flow will force the flow to rotate. Similarly, the heat generated by the fire creates a low pressure, and in an environment with strong winds, this process results in the formation of a vortex.</p>
<p><a href="https://doi.org/10.1029/2018GL080667">One fire tornado</a>, or fire whirl, that developed during the deadly 2018 Carr Fire devastated parts of Redding, California, with winds clocked at over 143 miles per hour.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/7ptCSs6uyu4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>These vortices can also increase the severity of the fires themselves by sucking air rich in oxygen toward the center of the vortex. The hotter the fire, the higher the probability of stronger updrafts and stronger and larger vortices.</p>
<p>Persistent heat waves that dry out the land and vegetation have increased the potential of wildfires to be more violent and widespread.</p>
<h2>Is extreme fire weather becoming more common?</h2>
<p>Global warming has modified the Earth’s climate in ways that profoundly affect the behavior of wildfires.</p>
<p>Scientific <a href="https://www.climateassessment.ca.gov/">evidence suggests</a> that the severity of prolonged droughts and heat waves has been exacerbated not only by rising temperatures but also by changes in atmospheric circulation patterns associated with recent climate change. These changes can enhance extreme fire-weather behavior.</p>
<p>A study published Aug. 20 found that the frequency of California’s extreme fire weather days in the autumn fire season had <a href="https://doi.org/10.1088/1748-9326/ab83a7">more than doubled</a> since the early 1980s. Over that four-decade period, autumn temperatures in the state rose by about 1.8 degrees Fahrenheit and autumn precipitation decreased by about 30%.</p>
<p>Firefighters and people living in wildfire-prone areas, meanwhile, need to be prepared for more extreme wildfires in the coming years.</p><img src="https://counter.theconversation.com/content/144904/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Charles Jones receives funding from the National Science Foundation and the University of California. </span></em></p><p class="fine-print"><em><span>Leila Carvalho receives funding from the National Science Foundation.</span></em></p>
Persistent heat waves and dry lightning are part of the problem. For firefighters, the erratic behavior gets dangerous quickly.
Charles Jones, Professor of Atmospheric Science, University of California, Santa Barbara
Leila Carvalho, Professor of Meteorology and Climatology, University of California, Santa Barbara
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/119861
2019-07-11T12:55:43Z
2019-07-11T12:55:43Z
Joy Division: 40 years on from ‘Unknown Pleasures’, astronomers have revisited the pulsar from the iconic album cover
<figure><img src="https://images.theconversation.com/files/283650/original/file-20190711-173325-1oj4n2t.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6000%2C3314&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">'Unknown Pleasures' as you've never seen it before...</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-illustration-rendering-black-white-line-1308510430?src=E285f9LBp2pjGmUMJk8lMw-1-49&studio=1">Freeda/Shutterstock</a></span></figcaption></figure><p>The English rock band Joy Division released their debut studio album “Unknown Pleasures” 40 years ago. The front cover doesn’t feature any words, only a now iconic black and white data graph showing 80 wiggly lines representing a signal from a pulsar in space. To mark the anniversary of the album, we recorded a signal from the same pulsar with a radio telescope in Jodrell Bank Observatory, only 14 miles (23 km) away from Strawberry Studios where the album was recorded.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"497303154279845888"}"></div></p>
<p>Peter Saville – graphic designer and co-founder of Factory Records – designed the album cover based on a picture spotted by band member Bernard Sumner in an encyclopaedia. The picture itself can be traced to the work of the postgraduate student Harold Craft, who published the image in his PhD thesis in 1970. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/282539/original/file-20190703-126376-b9s5nm.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/282539/original/file-20190703-126376-b9s5nm.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282539/original/file-20190703-126376-b9s5nm.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282539/original/file-20190703-126376-b9s5nm.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282539/original/file-20190703-126376-b9s5nm.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282539/original/file-20190703-126376-b9s5nm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282539/original/file-20190703-126376-b9s5nm.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282539/original/file-20190703-126376-b9s5nm.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Recording of the same pulsar, exactly 40 years after the album was released.</span>
<span class="attribution"><span class="source">Jodrell Bank Centre for Astrophysics, University of Manchester</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Unknown treasures in space</h2>
<p>What we see in this enigmatic image is the signal produced by a pulsar known as B1919+21, the first pulsar ever discovered. A pulsar is formed during the violent death of a star several times more massive than our sun. These stars go out with a bang known as a “supernova explosion”, during which the core of the exploding star is compressed in an almost perfect sphere with a radius of little more than 10 km. What’s formed is called a neutron star.</p>
<p>This stellar remnant, still more massive than our sun, is so extremely dense that the atoms from the original star cannot maintain their structure – they fall apart leaving smaller particles called neutrons, which form a vast ocean beneath the star’s crust. Pulsars are rapidly spinning neutron stars that can be observed from Earth. Thanks to their rotation and a magnetic field which is a trillion times stronger than that of the Earth, the magnetic north and south poles of these super magnets shine like a lighthouse. After having travelled for many hundreds of years, flashes of radiation from B1919+21 reach the Earth every 1.34 seconds.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1140000363367546882"}"></div></p>
<p>These flashes from pulsars are especially bright at radio wavelengths, so their signals can be recorded using radio telescopes. A radio telescope works similar to a radio in your car – its antenna focuses radio waves from space onto a point where they can be detected and turned into an electric signal, which can then be converted into sound. We used the Mark II radio telescope of the <a href="http://www.jb.man.ac.uk/research/pulsar/Education/Sounds/">Jodrell Bank Observatory</a> at the University of Manchester for our recording.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/282898/original/file-20190705-51297-1fdtu7k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/282898/original/file-20190705-51297-1fdtu7k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282898/original/file-20190705-51297-1fdtu7k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282898/original/file-20190705-51297-1fdtu7k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282898/original/file-20190705-51297-1fdtu7k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282898/original/file-20190705-51297-1fdtu7k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282898/original/file-20190705-51297-1fdtu7k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Mark II telescope at the Jodrell Bank Observatory which made a 47-minute recording of B1919+21.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Mark_II_(radio_telescope)#/media/File:Jodrell_Bank_Mark_II.jpg">Mike Peel/Jodrell Bank Centre for Astrophysics, University of Manchester</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The album cover shows 80 wiggly lines which correspond to 80 flashes of radio waves from B1919+21, as the neutron star made 80 turns in 107 seconds. Unlike lighthouses on Earth, each flash is unique. Some flashes are bright – these are denoted in the image by their large spikes – and some are dim. </p>
<p>The shape of the pulses are ever changing. At first glance, they seem irregular and chaotic, but our new imaging reveals some order in the chaos. It’s the same number of pulses from the same pulsar and observed at the same frequency as the diagram from the album cover, but in the image below, a diagonal pattern of stripes emerges.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/282538/original/file-20190703-126382-wi9gtv.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/282538/original/file-20190703-126382-wi9gtv.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282538/original/file-20190703-126382-wi9gtv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=914&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282538/original/file-20190703-126382-wi9gtv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=914&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282538/original/file-20190703-126382-wi9gtv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=914&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282538/original/file-20190703-126382-wi9gtv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1148&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282538/original/file-20190703-126382-wi9gtv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1148&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282538/original/file-20190703-126382-wi9gtv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1148&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 signal of the same pulsar as featured on the album cover. The lighter the colour is, the more intense the radio waves are.</span>
<span class="attribution"><span class="source">Jodrell Bank Centre for Astrophysics, University of Manchester</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>When the original signal was recorded, it was not known why some pulsars showed this kind of pattern. We now believe that the radio waves are produced by particles which shoot away from the neutron star at nearly the speed of light. The particles are created by electric discharges between the ionised gas surrounding these objects and the surface of the star itself. So, in essence, the radio waves on the album cover and in our new imaging are caused by lightning in outer space, observed many light years away. </p>
<p>A “weather map” can help visualise the vast lightning systems which circulate the magnetic poles of pulsars. The pattern of their lightning changes continuously and the shape of the observed pulses appear somewhat erratic – but observing over a longer period allows a pattern to emerge.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/282537/original/file-20190703-126360-ag3ko1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/282537/original/file-20190703-126360-ag3ko1.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=599&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282537/original/file-20190703-126360-ag3ko1.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=599&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282537/original/file-20190703-126360-ag3ko1.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=599&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282537/original/file-20190703-126360-ag3ko1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=752&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282537/original/file-20190703-126360-ag3ko1.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=752&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282537/original/file-20190703-126360-ag3ko1.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=752&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Looking down on the magnetic pole of pulsar B1919+21 which is encircled by lightning.</span>
<span class="attribution"><span class="source">Jodrell Bank Centre for Astrophysics, University of Manchester</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Four decades after the release of the Unknown Pleasures album we now understand much better what those wiggly lines on its cover mean. But many questions remain about these enigmatic objects, which in many respects are nature’s most extreme creation. Something which remained true for all these years is that pulsar recordings push us to explore the limits of our understanding of the laws of physics.</p><img src="https://counter.theconversation.com/content/119861/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Patrick Weltevrede receives funding from the UK Science and Technology Facilities Council (STFC)</span></em></p>
When you look at the squiggly lines on Joy Division’s famous album cover, you’re seeing a record of lightning in outer space.
Patrick Weltevrede, Lecturer In Pulsar Astrophysics, University of Manchester
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/111264
2019-02-06T19:20:43Z
2019-02-06T19:20:43Z
Dry lightning has set Tasmania ablaze, and climate change makes it more likely to happen again
<p>Every year Tasmania is hit by thousands of lightning strikes, which harmlessly hit wet ground. But a huge swathe of the state is now burning as a result of “dry lightning” strikes.</p>
<p>Dry lightning occurs when a storm forms from high temperatures or along a weather front (as usual) but, unlike normal thunderstorms, the rain evaporates before it reaches the ground, so lightning strikes dry vegetation and sparks bushfires. </p>
<p>Dangerous, large fires occur when dry lightning strikes in very dry environments that are full of fuel ready to burn. Cold fronts in Tasmania, which often carry fire-extinguishing rain, have recently been dry, making these fires worse. The fronts draw in strong hot, dry northerly winds, fanning the flames. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/fires-in-tasmanias-ancient-forests-are-a-warning-for-all-of-us-53806">Fires in Tasmania's ancient forests are a warning for all of us</a>
</strong>
</em>
</p>
<hr>
<p>Research has found that as climate change creates a drier Tasmania landscape, dry lightning – and therefore these kinds of fires – are likely to increase. </p>
<h2>History and detection in Tasmania</h2>
<p>Lightning has always started fires across Tasmania. Fire scars and other paleo evidence across Tasmania show large fires are a <a href="https://www.mdpi.com/2571-6255/1/3/38">natural process</a> in some places. However, frequent large, intense fires were rare. Now such fires are being fought <a href="https://www.mdpi.com/2571-6255/1/3/38">almost every year</a>.</p>
<p>Contrary to anecdotal belief, our recent preliminary work suggests that lightning activity has not increased over recent decades. So why do fires started by lightning appear to be increasing? </p>
<p>As temperatures rise, evaporation rates are increasing, but current rainfall rates are about the same. In combination this means the Tasmanian landscape is drying. The landscape is more often primed, waiting for an ignition source such as a dry-lightning strike. In such conditions, it only takes one.</p>
<h2>When dry lighting strikes</h2>
<p>Lightning struck just such a landscape in late December 2018, starting the Gell River bushfire in southwest Tasmania. This uncontrollable fire burnt about 20,000 hectares in the first half of January and is still burning. These large fires deplete the state’s resources, fatigue our volunteer and professional fire fighters and can have <a href="http://theconversation.com/ecosystems-across-australia-are-collapsing-under-climate-change-99367">disastrous effects</a> on natural systems. </p>
<p>With no significant rain falling over Tasmania since mid-December, the island is breaking dry spell records and thousands of dry lightning events have occurred. On <a href="http://www.fire.tas.gov.au/Show?pageId=colMediaReleases#61555">January 15 alone</a> over 2,000 lightning strikes sparked more than 60 bushfires. </p>
<p>Most of these were controlled rapidly, a credit to Tasmania’s emergency responders. One of the worst-hit areas was the Tasmanian Wilderness World Heritage Area, where many bushfires continue to burn in inaccessible locations. </p>
<p>This is putting some of Tasmania’s most pristine and valuable places in danger of being lost. The state stands to lose its most remarkable old-growth forests, like Mount Anne, which is home to some of the world’s largest King Billy Pines, a species endemic to Tasmania. </p>
<h2>Increasing dry area</h2>
<p>Ongoing climate change is making dry spells longer and more frequent, increasing the fire-prone area of Tasmania. Almost the whole state is becoming vulnerable to dry lightning. </p>
<p>Some regions of the west coast of Tasmania used to have very little to no risk of bushfires as they were always damp. However, this is no longer the case, resulting in species coming under threat.</p>
<p>Unlike most of Australia’s vegetation, many of Tasmania’s alpine and subalpine species evolved in the absence of fire and therefore do not recover after being burnt. Endemic species like Pencil Pine, Huon Pine and Deciduous Beech may be wiped out by one fire.</p>
<p>So what does the future hold? Using data from <a href="http://acecrc.org.au/climate-futures-for-tasmania/">Climate Futures for Tasmania</a>, we can peek into the future. Our models indicate that climate change is highly likely to result in profound changes to the <a href="http://www.publish.csiro.au/WF/WF13126">fire climate of Tasmania</a>, especially in the west.</p>
<h2>Climate change already playing a role</h2>
<p>With a warming climate, the rain-producing low-pressure systems are moving south and many storms that used to hit Tasmania are drifting south, leaving the island drier. This, combined with increasing evaporation rates, result in rapid drying of some areas. Areas that historically rarely experienced fire will become increasingly prone to burn. The drying trend is projected to be particularly profound throughout western Tasmania. </p>
<p>By the end of the century, summer conditions are projected to last <a href="http://climatefutures.org.au/publications/climate-futures-for-tasmania/future-fire-danger/">eight weeks longer</a>. This drying means that lightning events (and therefore dry lightning) will become an ever-increasing threat and the impact of these events will become more significant. </p>
<p>Higher levels of dryness will mean when bushfires occur the potential for these to burn into the rainforest, peat soils and alpine areas will be significantly increased.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-far-away-was-that-lightning-97289">How far away was that lightning?</a>
</strong>
</em>
</p>
<hr>
<p>These changes are already happening and will get progressively worse throughout the 21st century. Climate change is no longer a threat of the future: we are experiencing it now.</p><img src="https://counter.theconversation.com/content/111264/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Love receives (or has received) funding from the: National Bushfire Mitigation Program; National Environmental Science Program; Bushfire and Natural Hazards Cooperate Research Center; Tasmania State Emergency Management Program; National Disaster Resilience Grants Program.</span></em></p><p class="fine-print"><em><span>Rebecca Harris received funding from the National Bushfire Mitigation – Tasmanian Grants Program, Bushfire and Natural Hazards Cooperative Research Center; Tasmania State Emergency Management Program; National Disaster Resilience Grants Program.</span></em></p><p class="fine-print"><em><span>Tomas Remenyi receives (or has received) funding from the: National Bushfire Mitigation Program; National Environmental Science Program; Bushfire and Natural Hazards Cooperate Research Center; Tasmania State Emergency Management Program; National Disaster Resilience Grants Program. </span></em></p><p class="fine-print"><em><span>Nick Earl-Jones 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>
Climate change is making Tasmania more vulnerable to brutal fire conditions.
Nick Earl-Jones, Postdoctoral associate, School of Earth Sciences, The University of Melbourne
Peter Love, Atmospheric Physicist, University of Tasmania
Rebecca Harris, Climate Research Fellow, University of Tasmania
Tomas Remenyi, Climate Research Fellow, Climate Futures Group, Antarctic Climate and Ecosystems CRC, University of Tasmania
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/110316
2019-01-28T13:33:37Z
2019-01-28T13:33:37Z
Curious Kids: should I be scared of lightning?
<figure><img src="https://images.theconversation.com/files/254980/original/file-20190122-100282-1y9bwkl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">LM Gray/Shutterstock</span></span></figcaption></figure><p><em>Curious Kids is a series for children in which we ask experts to answer questions from kids.</em></p>
<p><strong>Should I be scared of lightning? (Callan, 10, Johannesburg)</strong></p>
<p>Big storms can be very scary. When a storm happens dark clouds appear, heavy rain often falls, winds are gusty and unpredictable, and lightning flashes across the sky. </p>
<p>Lightning happens all over the world. But it’s <a href="https://www.sciencealert.com/nasa-map-reveals-where-lightning-occurs-most-on-the-planet">particularly common</a> near the equator, where the strongest and most energetic thunderstorms take place. Storms can lead to all sorts of potential dangers, like flooded streets or homes, fallen trees, fires, and roofs being blown off houses.</p>
<p>Lightning can also be dangerous for people. No one knows how many people are killed every year by lightning, but it could be up to tens of thousands worldwide. In South Africa, around 250 people are killed every year, mainly in rural areas where there’s little protection when storms take place.</p>
<p>So there are many reasons to be careful when there’s a big storm. But there are also ways you can protect yourself to avoid lightning. </p>
<p>Many different cultural traditions believe that lightning is caused <a href="http://lightningsafety.com/nlsi_info/myths.html">by gods or spirits</a>. Some people believe that lightning can be prevented by planting certain trees or shrubs near the house, covering mirrors, or placing car tyres on the house roof. </p>
<p>There is no scientific evidence that any of these things make you safer from lightning. </p>
<p>But there are some practical things you can do to keep safe when lightning strikes.</p>
<ul>
<li><p>If you are outside, keep on low ground and stay away from trees, poles and water. Or stay undercover in a car or building. Do not shelter under a tree;</p></li>
<li><p>If you are inside, stay away from windows, doors, metal objects and water (including taps);</p></li>
<li><p>Don’t use electrical equipment (including phones).</p></li>
</ul>
<p>It’s also useful to know what lightning is – understanding something can make it seem less scary.</p>
<h2>What is lightning?</h2>
<p>Lightning happens when air moves around in the atmosphere, forming thunderclouds. </p>
<p>Dark clouds are the first visible sign that a storm is coming. Clouds are formed when air rises upwards in the atmosphere, cooling as it goes. We know that air is moving around because we can feel it - this is wind. As air rises, moisture condenses and clouds begin to form. Storm clouds reach high in the atmosphere and are spread sideways by the wind. This is what makes the dark heavy cloud shapes you see when a storm is brewing. </p>
<p>Once the clouds have formed, the air currents keep rising. If the air is cold enough, water droplets inside the clouds can freeze into ice crystals. These are lighter than liquid drops of water, so they get pushed up to the top of the cloud. The heavier liquid water droplets fall to the bottom of the cloud.</p>
<p>Because ice crystals and water droplets have different <a href="https://www.britannica.com/science/electric-charge">electrical charges</a>, the tops and bottoms of storm clouds develop different patterns of charges as the storm cloud gets bigger. There are also differences in electrical charges between the bottom of the cloud and the land surface. If the charge difference is big enough, electrical energy suddenly flows from one place to another.</p>
<p>This flow of energy is shown as a lighting flash. A single lightning flash lasts for only around 0.0001 seconds but can reach temperatures of up to 30,000°C: five times hotter than the surface of the Sun. This huge amount of energy is why lightning can cause so much damage when it strikes.</p>
<p>You’ll also have noticed that thunder and lightning happen together. Thunder is formed when air molecules rapidly expand, forming a sound shock wave that travels through the atmosphere at the speed of sound, much faster than a plane can fly. </p>
<p>But the lightning flash travels much quicker than thunder, at the speed of light – that’s 300,000 km per second. (The top speed for cars on most highways is 120 km an hour.) The difference between the speed of light and the speed of sound can be used to estimate how far away the lightning is. </p>
<p>A good experiment is to slowly count the seconds between a lightning flash and when you hear the roll of thunder. You can then work out whether the storm is getting closer to you (if the time difference is getting shorter) or further away (if the time difference is getting longer).</p>
<p>A city like Johannesburg in South Africa has thunderstorms in the summer. But the lightning South Africans experience is still only a third of what is found in the <a href="https://journals.ametsoc.org/doi/full/10.1175/BAMS-D-14-00193.1">world’s lightning hotspot</a>: the mountains of Uganda, Rwanda and Democratic Republic of Congo.</p>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to africa-curiouskids@theconversation.com. Please tell us your name, age, and which city you live in. We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/110316/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jasper Knight 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>
There are many reasons to be careful when there’s a big storm. But there are also ways you can protect yourself to avoid lightning.
Jasper Knight, Professor of Physical Geography, University of the Witwatersrand
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/97289
2018-06-07T10:53:35Z
2018-06-07T10:53:35Z
How far away was that lightning?
<figure><img src="https://images.theconversation.com/files/221632/original/file-20180604-175445-meat87.jpg?ixlib=rb-1.1.0&rect=587%2C71%2C3455%2C2583&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">One one thousand, two one thousand....</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/vP5Im4q8Z6g">Eric Ward/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>You probably do it. It might be ingrained from when you were a kid, and now it’s almost automatic. You see the flash of lightning – and you immediately start counting the seconds till it thunders.</p>
<p>But does counting really get you a good estimate for how far away the lightning is? Is this one of those old wives’ tales, or is it actually based on science? In this case, we have physics to thank for this quick and easy – and pretty accurate – calculation.</p>
<p>So what happens when a big storm rolls in?</p>
<p>The lightning you see is the <a href="https://www.nssl.noaa.gov/education/svrwx101/lightning/">discharge of electricity</a> that travels between clouds or to the ground. The thunder you hear is the rapid expansion of the air in response to the lightning’s intense heat.</p>
<p>If you’re really close to the lightning, you will see it and hear the thunder simultaneously. But when it’s far away, you see and hear the event at different times. That’s because <a href="https://morgridge.org/blue-sky/why-is-light-faster-than-sound/">light travels much faster than sound</a>. Think of sitting in the nosebleed seats at a baseball game. You see the batter hit the ball a second before you hear the crack of the bat. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/221638/original/file-20180604-175414-15qczrv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221638/original/file-20180604-175414-15qczrv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/221638/original/file-20180604-175414-15qczrv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221638/original/file-20180604-175414-15qczrv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221638/original/file-20180604-175414-15qczrv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221638/original/file-20180604-175414-15qczrv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221638/original/file-20180604-175414-15qczrv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221638/original/file-20180604-175414-15qczrv.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">The visual part is instantaneous.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/noaaphotolib/27330291264">Pete Gregoire</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>When observing an event on Earth, you see things almost the instant they happen – the speed of light is so fast you can’t even detect the travel time. The speed of sound is much slower, which gives us time to do our calculation.</p>
<p>Let’s simplify the speed equation: <a href="https://en.wikipedia.org/wiki/Speed_of_sound">Sound travels a little over 700 miles per hour</a>, or 700 miles in 3,600 seconds. That means 7 miles traveled every 36 seconds. Make this even easier and round down to 7 miles every 35 seconds… or 1 mile every 5 seconds! Count to 5: If you hear thunder, the lightning occurred within 1 mile.</p>
<p>Now that you know how far away that lightning strike was, is it far enough to be <a href="https://www.weather.gov/safety/lightning-safety">a safe distance from the storm</a>? That’s actually a trick question. Thunder can be heard up to 25 miles away, and lightning strikes have been documented to occur as far as 25 miles from thunderstorms – known as a “<a href="https://www.nssl.noaa.gov/education/svrwx101/lightning/faq/">bolt from the blue</a>.” So if you can hear thunder, you’re close enough to be hit by lightning, and sheltering indoors or in an enclosed car is your safest bet.</p>
<p>And don’t count on the folk wisdom that lightning never strikes the same place twice to protect you. That one is just plain wrong. For example, lightning strikes the top of the <a href="https://www.livescience.com/13704-empire-state-building-lightning-strike.html">Empire State Building</a> an average of 23 times per year.</p><img src="https://counter.theconversation.com/content/97289/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Becky Bolinger receives funding from National Oceanic and Atmospheric Administration and the State of Colorado to monitor drought and climate conditions. </span></em></p>
When you see a bolt of lightning, do you immediately start counting to see how far off a storm is? An atmospheric scientist parses the practice.
Becky Bolinger, Assistant State Climatologist and Research Scientist in Atmospheric Science, Colorado State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/89102
2017-12-14T11:16:56Z
2017-12-14T11:16:56Z
Here’s how a real lightsaber would fare in a Star Wars-style lightning attack
<figure><img src="https://images.theconversation.com/files/199013/original/file-20171213-27572-pkh3rg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Watch out for that cloud, Rey!</span> <span class="attribution"><span class="source">Walt Disney Studios Motion Pictures / Lucasfilm Ltd. / Everett</span></span></figcaption></figure><p>With the latest film in the Star Wars saga hitting cinemas, it got me thinking about lightsabers – the iconic weapon of Jedi and Sith alike. Despite their name, these glowing blades would in fact be made of the stuff I research – a soup of charged particles called “plasma”. This is sometimes known as the “<a href="https://www.youtube.com/watch?v=_SoKuW1-Yf4">fourth state of matter</a>” in addition to solids, liquids and gases.</p>
<p>As I’ve <a href="https://theconversation.com/why-lightsabers-would-be-far-more-lethal-than-george-lucas-envisioned-55726">previously shown</a>, real-life lightsabers would theoretically be possible, though horrendously impractical and somewhat beyond our current technological capabilities. Essentially, glowing hot plasma could be shaped into a blade by using strong magnets in much the same way we do for current nuclear fusion reactor experiments.</p>
<p>The downside would be lightsaber battles. A fundamental plasma physics process called <a href="http://www.nasa.gov/content/goddard/science-of-magnetic-reconnection">magnetic reconnection</a> would be unavoidable when two blades got close enough to clash. The entire pattern of the magnetic field lines would change, explosively releasing all the hot plasma contained in both lightsabers. The likely result is that both you and your opponent would have body parts vaporised in a single clash.</p>
<p>Something of a disappointment. And so I wondered whether the lightsaber would be up to the task against a different form of attack from the films – lightning. The earlier films showed us that lightsabers seem to absorb or block “<a href="http://www.starwars.com/databank/force-lightning">force lightning</a>” attacks, but would the same happen for a lightsaber that obeys the laws of physics?</p>
<h2>Mysterious force</h2>
<p>Thunder and lightning have been the subject of speculation and scientific inquiry for at least 2,500 years. Ancient Greek philosopher <a href="https://en.wikipedia.org/wiki/Empedocles">Empedocles</a> thought that the sun’s rays hitting clouds caused fires which would quickly drive out air causing a noise, thunder, and a gleam, lightning. It wasn’t until some 2,000 years later that <a href="https://en.wikipedia.org/wiki/Electric_charge">the discovery of electric charges</a> started to reveal the true, but incredibly complex, nature of the phenomenon that scientists <a href="https://theconversation.com/thunderstorms-create-radioactivity-scientists-discover-87946">are still investigating to this day</a>.</p>
<p>Despite the fact that we still have a lot to learn about lightning and its many forms, there is a general consensus surrounding some of the basic concepts of how and why it occurs. The conditions in storm clouds lead to an updraft carrying light ice crystals which then collide with hail suspended in the clouds. These collisions result in static electric charges, which build up at the top and bottom of the cloud.</p>
<p>Thunder clouds are actually incredibly tall, around 10km, so the bottom of a cloud is actually closer to the ground than to the top of it. This means an electric field builds up in the air between the ground and the cloud. Normally, air, being a gas, is a pretty poor conductor of electricity – meaning currents aren’t able to flow through it. However, when the electric fields get large enough they can knock electrons off the air molecules, forming channels of plasma.</p>
<p>Plasmas, unlike gases, are great conductors of electricity – in fact, many laboratory plasmas are comparable with most metals in this regard. This is because plasmas contain loose electrons (negatively charged) and atoms that have lost electrons (positively charged). It’s the much lighter electrons which really allow electricity to flow within a plasma.</p>
<p>The flash of lightning occurs when a plasma channel connects the ground to the cloud, allowing huge currents to flow which superheat the air causing it to glow and emitting an audible shockwave or thunder. This all happens incredibly quickly though, typically lasting about 30 microseconds.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/qdEbjH-Lu4k?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>But, if lightsabers are also made of plasma, that would make them fantastic conductors of electricity, too. Just like the lightning rods on buildings, a lightsaber would provide a low resistance path for electrical currents to flow to the ground – making them far more likely to be struck by lightning than anything in the surrounding area. </p>
<p>However, the easiest way for that current to flow to the ground after it hits the plasma blade would be to travel through your body, which is a fairly good conductor too. So a wielder of a real-life lightsaber would be prone to direct lightning hits and therefore subject to severe burns, burst blood vessels and potential cardiac arrest.</p>
<p>Given that in one of the <a href="https://www.youtube.com/watch?v=W4CB5SeBGkI">latest trailers</a> Rey is shown wielding a lightsaber during a rainstorm, I’m worried she might not survive to the end of the film.</p><img src="https://counter.theconversation.com/content/89102/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Archer 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 Star Wars, ‘force lightning’ is a lethal weapon that can only be tackled with a lightsaber. But would it work in real life?
Martin Archer, Space Plasma Physicist, Queen Mary University of London
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/87946
2017-11-22T18:01:37Z
2017-11-22T18:01:37Z
Thunderstorms create radioactivity, scientists discover
<figure><img src="https://images.theconversation.com/files/195818/original/file-20171122-6072-skhc5p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Maxime Raynal/wikipedia</span></span></figcaption></figure><p>Thunder and lightning have sparked awe and fear in humans since time immemorial. In both modern and ancient cultures, these natural phenomena are often thought to be governed by some of the most important and powerful gods – <a href="http://www.sanatansociety.org/hindu_gods_and_goddesses/indra.htm#.WhVO8bSFhmA">Indra in Hinduism</a>, <a href="https://www.greekmythology.com/Olympians/Zeus/zeus.html">Zeus in Greek mythology</a> and <a href="https://www.ancient.eu/Thor/">Thor in Norse mythology</a>. </p>
<p>We know that thunderstorms can trigger a number of remarkable effects, most commonly power cuts, hailstorms and pets hiding under beds. But it turns out we still have things to learn about them. A new study, <a href="http://nature.com/articles/doi:10.1038/nature24630">published in Nature</a>, has now shown that thunderstorms can also produce radioactivity by triggering nuclear reactions in the atmosphere. </p>
<p>This may sound like the plot of a blockbuster science fiction disaster. But in reality, it’s nothing to worry about. Since the early 20th century, scientists have been aware of <a href="https://theconversation.com/explainer-how-much-radiation-is-harmful-to-health-17906">ionising radiation</a> – particles and electromagnetic waves that can damage cells – raining down into the Earth’s atmosphere from space. This radiation can react with atoms or molecules, carrying enough energy to liberate electrons from either atoms or molecules. It therefore leaves behind an “ion” with a positive electrical charge.</p>
<p>Just over a century ago, the Austrian physicist <a href="https://en.wikipedia.org/wiki/Victor_Francis_Hess">Victor Hess</a> made measurements of ionisation in a hot-air balloon five kilometres above the Earth’s surface. He noted that the ionisation rate increased rapidly with height, the opposite of what might be expected if the source of the ionising radiation was coming from the ground. Hess therefore concluded that there must be a source of radiation with very high penetrating power located above the atmosphere. He was named co-recipient of the <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1936/">Nobel Prize in Physics in 1936</a> for his discovery, later dubbed “cosmic rays”.</p>
<p>We now know that cosmic rays are made up of charged particles: primarily, electrons, atomic nuclei and protons – the latter make up the nucleus along with neutrons. Some originate from the sun, while others come from the <a href="https://theconversation.com/an-extragalactic-mystery-where-do-high-energy-cosmic-rays-come-from-6623">distant explosions of dead stars</a> in our galaxy, known as supernovas. When these cosmic rays enter the Earth’s atmosphere, they interact with atoms and molecules to produce a shower of <a href="https://theconversation.com/explainer-what-are-fundamental-particles-38339">subatomic particles</a>. Among these are neutrons, which have no electric charge.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=456&fit=crop&dpr=1 600w, https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=456&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=456&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=573&fit=crop&dpr=1 754w, https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=573&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/195848/original/file-20171122-6044-cx0uhf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=573&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A simulation of a cosmic ray shower formed when a proton hits the atmosphere about 20km above the ground.</span>
<span class="attribution"><span class="source">wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>It is these neutrons that <a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690">make radiocarbon dating possible</a>. Most carbon atoms have six protons and either six or seven neutrons in their nuclei (dubbed “isotopes <sup>12</sup>C and <sup>13</sup>C” respectively). However, neutrons produced by cosmic rays can react with atmospheric nitrogen to create <sup>14</sup>C, a heavy and unstable isotope of carbon that, over time, will “radioactively decay” (split up while emitting radiation) back into nitrogen. </p>
<p>In nature, <sup>14</sup>C is incredibly rare and makes up only about one in a trillion carbon atoms. But, apart from its weight and radioactive properties, 14C is basically identical to the more common carbon isotopes. It oxidises to form carbon dioxide and enters the food chain as plants absorb the radioactive CO<sub>2</sub>. </p>
<p>The ratio of <sup>12</sup>C to <sup>14</sup>C in a given organism will start to change when that organism dies and ceases to ingest carbon. The <sup>14</sup>C already in its system then starts to decay. It’s a slow process since <sup>14</sup>C has a radioactive half-life of 5,730 years, but it is predictable, meaning that organic samples can be dated by measuring the ratio of <sup>12</sup>C to <sup>14</sup>C still remaining.</p>
<p>In this way, cosmic rays are responsible for nuclear reactions in the Earth’s atmosphere. Until today, we thought it was the only natural channel producing radioactive elements such as <sup>14</sup>C. The word “nuclear”, so sinister when partnered with “bomb” or “waste”, simply refers to the changes that are brought about in an atomic nucleus. </p>
<h2>Chasing neutrons</h2>
<p>Almost 100 years ago, the renowned Scottish physicist and meteorologist <a href="https://en.wikipedia.org/wiki/Charles_Thomson_Rees_Wilson">Charles Wilson</a> proposed that thunderstorms could also trigger nuclear reactions in the atmosphere. Wilson, who undertook fieldwork at the isolated meteorological observatory on the summit of Ben Nevis, Britain’s highest mountain, was fascinated by thundercloud formation and atmospheric electricity. However, his suggestion predated the discovery of the neutron – one of the tell-tale products of nuclear reactions – by seven years, so his proposal could not be tested.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/195817/original/file-20171122-6020-a2u08.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">Lightning over the St Lawrence River on a stormy night in Quebec in 2010.</span>
<span class="attribution"><span class="source">Jp Marquis/wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Since Wilson’s time, there have been many studies that have claimed to have detected thunderstorm-produced neutrons, but <a href="https://www.nature.com/articles/313773a0">none have proven to be definitive</a>. Others have searched for energetic electomagnetic radiation (X-rays and gamma-rays) that accompanies the avalanche of high-energy electrons that we know is produced by lightning in thunderclouds. Calculations show that these electrons and gamma-rays can knock neutrons out of nitrogen and oxygen in the atmosphere. But although the X-ray and gamma-rays have been observed, there has never been a direct observation of the consequent nuclear reactions taking place in a thunderstorm.</p>
<p>The new study uses a different approach. Instead of searching for the elusive neutrons, the authors rely on other byproducts of the nuclear reactions. If electrons and gamma-rays cause unstable isotopes of nitrogen and oxygen to be formed by nuclear reactions following a lightning stroke, these should decay after a few minutes to form stable isotopes of carbon and nitrogen. </p>
<p>Crucially, this decay produces a particle known as a “positron”, the “<a href="https://theconversation.com/explainer-what-is-antimatter-53414">antimatter</a>” version of the electron. All particles have antimatter versions of themselves – these have the same mass but the opposite charge. When antimatter and matter come in contact, they annihilate in a flash of energy. This is the energy the researchers looked for. Using radiation detectors looking over the Sea of Japan, they observed the unambiguous gamma ray fingerprints of positron-electron annihilation taking place immediately after lightning strikes in low winter thunderclouds. This is clear evidence of nuclear reactions taking place in thunderclouds.</p>
<p>These results are important as they demonstrate a previously unknown source of isotopes in the Earth’s atmosphere. These include <sup>13</sup>C, <sup>14</sup>C and <sup>15</sup>N but future studies may also reveal others, such as isotopes of hydrogen, helium and beryllium. </p>
<p>The findings also have implications for astronomers and planetary scientists.
Other planets within our solar system have thunderstorms in their atmospheres that might contribute to the composition of their atmospheres. One of these planets is Jupiter, which is fittingly also the god of thunder in ancient Roman mythology.</p><img src="https://counter.theconversation.com/content/87946/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jim Wild receives funding from the Science and Technology Facilities Council (STFC) and the Natural Environment Research Council (NERC). He is a Fellow of the Royal Astronomical Society and a member of the American Geophysical Union. He is currently the Chairman of the STFC Astronomy Grants Panel. </span></em></p>
Scientists have finally been able to prove that thunder and lightning drive nuclear reactions.
Jim Wild, Professor of Space Physics, Lancaster University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/64152
2016-12-09T02:07:57Z
2016-12-09T02:07:57Z
Catching lightning in a fossil – and calculating how much energy a strike contains
<figure><img src="https://images.theconversation.com/files/149316/original/image-20161208-31402-vgl94l.jpg?ixlib=rb-1.1.0&rect=229%2C9%2C1634%2C1299&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Very powerful, try to avoid.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/rickywilson/2569675373">Rick Wilson</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>For most of human history, people have been terrified by lightning. <a href="http://www.sacred-texts.com/afr/fssn/fsn21.htm">Frightening bolts from above</a>, lightning was a <a href="http://lightningsafety.com/nlsi_info/myths.html">tool of the gods</a> to smite mortals for their hubris (or their unfortunate penchant for seeking shelter from storms under trees). The discovery and implementation of <a href="https://www.fi.edu/history-resources/franklins-lightning-rod">Benjamin Franklin’s lightning rod</a> tamed this once formidable, divine weapon.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/149318/original/image-20161208-31352-1m75vph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/149318/original/image-20161208-31352-1m75vph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/149318/original/image-20161208-31352-1m75vph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=897&fit=crop&dpr=1 600w, https://images.theconversation.com/files/149318/original/image-20161208-31352-1m75vph.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=897&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/149318/original/image-20161208-31352-1m75vph.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=897&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/149318/original/image-20161208-31352-1m75vph.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1127&fit=crop&dpr=1 754w, https://images.theconversation.com/files/149318/original/image-20161208-31352-1m75vph.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1127&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/149318/original/image-20161208-31352-1m75vph.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1127&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Will a lightning bolt contain enough energy to blast Marty McFly through time?</span>
</figcaption>
</figure>
<p>Nonetheless, lightning’s strength still lingers in our imagination. Hollywood considers it powerful enough to allow strangely designed cars from the early 1980s to <a href="http://www.imdb.com/title/tt0088763/">break the space-time continuum</a>. In the comic book world, it’s an ingredient in the <a href="https://en.wikipedia.org/wiki/Flash_(Barry_Allen)">formula for developing superpowers</a>. It has also been given the power to <a href="https://en.wikipedia.org/wiki/Frankenstein%27s_monster">return life to the dead</a>, though not always with the intended effect.</p>
<p>Just how much energy actually is in a lightning bolt? It may seem like this question should have been definitively answered before, but it turns out it’s difficult to answer quantitatively. In my research, we <a href="http://doi.org/10.1038/srep30586">tackled this issue in a new way</a>: We deduced how big a bolt of lightning was based on the size of rocks formed by lightning.</p>
<h2>Rough estimates</h2>
<p>Lightning is obviously powerful: One need only look at a tree that it’s splintered down the center for proof. Lightning generates temperatures hotter than the surface of the sun, <a href="http://doi.org/10.1016/0021-9169(64)90113-8">in excess of 20,000 degrees Celsius</a>, a temperature that is otherwise unrelateable to the human experience.</p>
<p>This temperature measurement provides <a href="http://doi.org/10.1029/RG022i004p00363">one way to estimate the energy of lightning</a>. It takes a certain amount of energy to heat air to a high temperature. By measuring the length of a lightning strike, multiplying it by the energy per length required to heat up the air to tens of thousands of degrees, we can calculate lightning’s energy.</p>
<p>Alternatively, we can approach the measurement of lightning energy by considering the voltage of a strike. A volt is a measurement of the amount of energy released as each pack of electrons flows from one side of an object to another – for instance, a battery. When lightning strikes, we can determine the <a href="http://doi.org/10.1109/15.249398">voltage it induces on nearby powerlines</a>; measurements range from hundreds of thousands to millions of volts. From <a href="https://en.wikipedia.org/wiki/Ohm%27s_law">Ohm’s law</a>, we can calculate the power of lightning by multiplying this by the number of electrons that move during the strike, a value known as the current. If we know the duration of this strike, we can then calculate the energy.</p>
<p>These methods have a large range of errors: not calculating the length of the lightning strike correctly, or getting the amount of gas heated per length wrong, or the temperature, or voltage, or number of electrons – all give pretty large errors for these calculations. </p>
<p>Could there be another route to calculating lightning energy that might pare down some of these errors? Florida’s unique geology provided an interesting route to answering this question.</p>
<h2>Fossilized lightning</h2>
<p>Florida tends to be a fairly boring state for a rock enthusiast. There’s sand, and there’s limestone. Not much else, and all of it is young, geologically speaking. Sometimes the sand is on top of the limestone, and sometimes it’s on the side. Sometimes the sand was deposited 15 million years ago, sometimes 5 million years ago. There’s a lot of sand. </p>
<p>Florida’s weather is a bit more interesting; it’s actually the U.S. state <a href="http://www.vaisala.com/VaisalaImages/Lightning/avg_sd_2005-2014_CONUS_2km_grid.png">most often struck by lightning</a>. A lot of times this lightning strikes the sand that covers the state. When it does so, it creates a new type of rock, called a fulgurite – a hollow tube formed as the lightning travels through the sand, vaporizing it and melting its outer edges. When the sand cools down, which happens quickly, the hollow tube is frozen in glass, recording the path the lightning traveled. By definition, a fulgurite is a metamorphic rock, changed by heat and pressure, from sand to something new.</p>
<p>Fulgurites are generally rare, unless you know where to look. Central peninsular Florida hosts several sand mines that supply the raw material for roads and cement, golf courses and playgrounds. At one site, we collected several hundred fulgurites; more than 250 lay in the field, with many more found in spoil piles, filtered out of the sand prior to its being loaded onto trucks.</p>
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<a href="https://images.theconversation.com/files/149290/original/image-20161208-31383-kx7vxr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/149290/original/image-20161208-31383-kx7vxr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/149290/original/image-20161208-31383-kx7vxr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/149290/original/image-20161208-31383-kx7vxr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/149290/original/image-20161208-31383-kx7vxr.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/149290/original/image-20161208-31383-kx7vxr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/149290/original/image-20161208-31383-kx7vxr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/149290/original/image-20161208-31383-kx7vxr.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 sand mine in Polk County, Florida, from which the fulgurites were collected.</span>
<span class="attribution"><span class="source">Matthew Pasek</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>These sites are not really any different than any place else in Florida – they aren’t some sort of lightning magnet – but the geologic setting was just right for keeping them around for a long time. These sand mines probably have about one million year’s worth of fulgurites buried inside of them. They’re easy to find – since glass isn’t something you want in commercial sand, the mine filters them out.</p>
<p>The fulgurites range in thickness from about the size of a baby’s little finger to about the size of man’s arm in thickness. The thicker ones had to be formed by much more energetic lightning bolts: a thicker fulgurite means more sand had to be vaporized. Most fulgurites we recovered were short fragments, though the longest ones found were a yard or two long.</p>
<h2>Calculating from the fulgurites</h2>
<p>It takes a specific amount of energy to vaporize sand into gas. First the sand has to be heated to around 1700°C, about the temperature of molten lava. At this temperature, the sand melts. The molten sand then has to heat to just shy of 3000°C, when it vaporizes. It takes about 15 megajoules of energy to heat and vaporize a kilogram of sand. That’s about the amount of energy the average U.S. household consumes in six hours, or the kinetic energy an average car would have if it were going 300 miles per hour.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/149300/original/image-20161208-31385-xczm6h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/149300/original/image-20161208-31385-xczm6h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/149300/original/image-20161208-31385-xczm6h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/149300/original/image-20161208-31385-xczm6h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/149300/original/image-20161208-31385-xczm6h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/149300/original/image-20161208-31385-xczm6h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/149300/original/image-20161208-31385-xczm6h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/149300/original/image-20161208-31385-xczm6h.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 largest fulgurite found during recovery at the sand mine.</span>
<span class="attribution"><span class="source">Matt Pasek</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>After measuring our fulgurites, we determined that on average, the energy required to form these rocks was at least about one megajoule per meter of fulgurite formed. We calculated the energy per meter since, again in most cases, the fulgurites we had collected were broken. </p>
<p>So based on our calculations, how close does Hollywood come, with estimates like in “Back to the Future” of 1.21 gigawatts of power in lightning? Power is energy per time, and our measurements of fulgurites suggest that megajoules of energy make rock in thousandths to millionths of seconds. So a gigawatt is actually on the low side – lightning power may be a thousand times that, reaching into the terawatts, though the average is probably tens of gigawatts.</p>
<p>That’s enough energy to power about a billion houses, albeit only for a few millionths of a second. Unfortunately, given its sporadic and unpredictable nature, no power grid will ever be able to harness lightning effectively. But with that much power, perhaps breaking the space-time continuum in a souped-up Delorean is not so unfeasible after all….</p>
<h2>An oddity in the pattern</h2>
<p>When we looked at these fulgurites in depth, something odd came out of the data. Our energy measurements followed something called a “lognormal” trend.</p>
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<p>Rather than following the bell curve we often see in the distribution of natural phenomena – like, for instance, the heights of American men – the energy curve was less equally balanced. For heights, the same number of men are two inches above average as are two inches below. But for lightning, the large lightning strikes were much larger than the average, while the smaller strikes were not so much smaller than the average. Strikes that were twice the average were as frequent as those that were half the average.</p>
<p>Now why might this be at all interesting or useful? Measuring the energy in lightning is a way of measuring potential damage: A lightning strike can vaporize rock, so what might it do to wood or electronics? Our measurements show that the biggest lightning strikes are multiples of the average lightning strikes: A big one might be 20 times as large as the average. That’s a lot for a <a href="https://en.wikipedia.org/wiki/Lightning_rod#Lightning_protection_system">lightning protection system</a> to handle. The peak energy calculated from our rock-based method may give an idea as to the maximum damage we may expect, and may eventually allow for better preparation against the worst-case scenario.</p><img src="https://counter.theconversation.com/content/64152/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Pasek receives funding from NASA Exobiology and Evolutionary Biology (Grant NNX14AN96G)</span></em></p>
Lightning strikes are powerful – but we haven’t had solid estimates of their energy until now. Researchers turned to the hollow stone tubes they create by vaporizing sand for more precise calculations.
Matthew Pasek, Associate Professor of Geosciences, University of South Florida
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/48351
2015-09-30T16:14:52Z
2015-09-30T16:14:52Z
It’s not just Facebook that goes down: the cloud isn’t as robust as we think
<figure><img src="https://images.theconversation.com/files/96819/original/image-20150930-5790-cpfs7z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Josemaria Toscano/shutterstock.com</span></span></figcaption></figure><p>The computing cloud we have created supports much of our day-to-day office and leisure activity, from office email to online shopping and sharing holiday photos. Even health, social care and government functions are moving towards digital delivery over the internet. </p>
<p>However, we should be wary that as we become more dependent on it, the cracks will show. The systems are often a patchwork of interconnected services provided by various companies and industry partnerships. A failure of one can lead to a failure in others. </p>
<p>For example, Skype recently went down for <a href="http://www.independent.co.uk/news/uk/skype-down-services-affected-across-the-globe-10510815.html">almost an entire day</a>, while Facebook was down for <a href="http://www.independent.co.uk/news/uk/skype-down-services-affected-across-the-globe-10510815.html">more than an hour</a> – the second time in a week – meaning that many sites that depend on Facebook accounts as authentication <a href="https://theconversation.com/when-facebook-goes-down-it-takes-big-chunks-of-the-internet-with-it-36873">were locked out too</a>. </p>
<p>Losing Facebook is an annoyance, but interruptions to major health and social care services or energy supply management systems can lead to real damage to the economy and people’s lives.</p>
<p>A few weeks ago Google’s data centres in Belgium (<a href="https://cloud.google.com/compute/docs/zones?hl=en">europe-west1-b</a>) lost power after the local power grid was <a href="https://status.cloud.google.com/incident/compute/15056">struck by lightning four times</a>. While most servers were protected by battery backup and redundant storage, there was still an estimated 0.000001% loss of disk space – which for Google’s huge data stores meant a few gigabytes of data. </p>
<p>The lesson is not to trust cloud providers to store and provide backups for your data. Your backups need backups too. What it also shows is our dependence on power supply system which, as long runs of conductive metal, are more prone to lightning strikes than you might imagine.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/96814/original/image-20150930-5809-ja1feo.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/96814/original/image-20150930-5809-ja1feo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/96814/original/image-20150930-5809-ja1feo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=231&fit=crop&dpr=1 600w, https://images.theconversation.com/files/96814/original/image-20150930-5809-ja1feo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=231&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/96814/original/image-20150930-5809-ja1feo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=231&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/96814/original/image-20150930-5809-ja1feo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=290&fit=crop&dpr=1 754w, https://images.theconversation.com/files/96814/original/image-20150930-5809-ja1feo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=290&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/96814/original/image-20150930-5809-ja1feo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=290&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Facebook response graph, showing outage.</span>
<span class="attribution"><span class="source">Bill Buchanan</span></span>
</figcaption>
</figure>
<h2>When the lights go out</h2>
<p>Former US secretary of defence, William Cohen, <a href="http://www.newsmax.com/Newsfront/William-Cohen-defense-chief-terrorist-attack-power-grid/2015/06/29/id/652742/">recently outlined</a> how the US power grid was vulnerable to a large-scale outage: “The possibility of a terrorist attack on the nation’s power grid — an assault that would cause coast-to-coast chaos,” he said, “is a very real one.”</p>
<p>As a former electrical engineer, I understand well the need for a safe and robust power supply, and that control systems can fail. It’s not uncommon to have alternative or redundant power supplies for important equipment. Single points of failure are accidents waiting to happen. Back-up your backup.</p>
<p>The electrical supply grid will try to provide alternative power whenever any part of it fails. The power supply system needs to be built with redundancy in case of problems, and monitoring and control systems that can respond to failures and keep the electricity supply balanced. </p>
<p>Cohen fears a major power outage could lead to civil unrest. Janet Napolitano, former Department of Homeland Security secretary, said a cyber-attack on the power grid was a case of “when,” not “if”. And former senior CIA analyst Peter Vincent Pry went so far as to say that an attack on the US electrical power supply network could “take the lives of every <a href="http://www.slate.com/articles/technology/future_tense/2015/07/emp_threats_could_an_electro_magnetic_pulse_weapon_wipe_out_the_power_grid.html">nine out of ten Americans</a>”. The damage that an electromagnetic pulse (EMP) could cause, such as from a nuclear weapon air-burst, is well known. But many now think the complex and interconnected nature of industrial control systems, known as <a href="http://www.engineersgarage.com/articles/scada-systems">SCADA</a>, could be the major risk.</p>
<p>An example of the potential problem is the <a href="http://www.scientificamerican.com/article/2003-blackout-five-years-later/">north-east US blackout on August 14 2003</a>, which affected 508 generating units at 265 separate power plants, cutting off power to 45m people in eight US states and 10m people in Ontario. It was caused by a software flaw in an alarm system in an Ohio control room which failed to warn operators about an overload, leading to domino effect of failures. It took two days to restore power.</p>
<p>As the world becomes increasingly internet-dependent, we have created a network that provides redundant routes to carry traffic from point to point, but electrical supply failures can still take out core routing systems.</p>
<h2>Control systems - the weakest link</h2>
<p>Often it’s the less obvious elements of infrastructure that are most open to attack. For example, air conditioning failures in data centres can cause overheating sufficient to melt equipment, especially the tape drives used to store vast amounts of data. This could affect anything from banking transactions worth billions, the routing of traffic around a busy city, or an emergency services call centre. </p>
<p>As we become more dependent on data and data-processing, so we are more vulnerable to their loss. Safety critical systems are built with failsafe control mechanisms, but those mechanisms can also attacked and compromised.</p>
<p>The cloud we have created and upon which we increasingly depend is not as hardy as we think. The internet itself, and the way we use it, is not as distributed as it was designed to be. We still rely too heavily on key physical locations where data and network interconnections are concentrated, creating unacceptable points of failure that could lead to a domino-effect collapse. The DNS infrastructure is a particular weak point, where just 13 root servers worldwide act as master lists for the entire web’s address book.</p>
<p>I don’t think governments have fully thought this through. Without power, without internet connectivity, there is no cloud. And without the cloud we have big problems.</p><img src="https://counter.theconversation.com/content/48351/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bill Buchanan 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>
When Facebook goes down it’s an irritation. But as the world moves its data and processing to the cloud, the potential for major loss grows ever greater.
Bill Buchanan, Head, Centre for Distributed Computing, Networks and Security, Edinburgh Napier University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/46636
2015-08-28T13:30:17Z
2015-08-28T13:30:17Z
Six amazing sights that look even better from the International Space Station
<figure><img src="https://images.theconversation.com/files/92927/original/image-20150825-15875-1pkpm9z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hurricane Arthur photographed by ESA astronaut Alexander Gerst.</span> <span class="attribution"><span class="source">ESA/NASA</span></span></figcaption></figure><p>Imagine seeing the lights of cities spreading around <a href="http://www.nasa.gov/multimedia/imagegallery/image_feature_1923.html">the Nile Delta</a> and then in less than an hour gazing down on <a href="http://www.nasa.gov/multimedia/imagegallery/image_feature_152.html">Mount Everest</a>. The astronauts on the <a href="http://www.nasa.gov/mission_pages/station/main/index.html">International Space Station</a> (ISS) are among the lucky few who will have this humbling, once-in-a-lifetime experience of seeing the beauty of Earth from space. </p>
<p>The ISS doesn’t just offer spectacular and countless views of the natural and man-made landscapes of our planet. It also immerses its residents into the Earth’s space environment and reveals how dynamic its atmosphere is, from its lower layers to its protective <a href="http://www.swpc.noaa.gov/phenomena/earths-magnetosphere">magnetic shield</a>, constantly swept by the solar wind.</p>
<p>The best views are seen from <a href="http://www.esa.int/Our_Activities/Human_Spaceflight/Views_from_Cupola">the Cupola</a>, an observation deck module attached to the ISS in 2010 and comprising seven windows. So, what are the amazing sights that you can see from the space station?</p>
<h2>1. Storms and lightning</h2>
<p>When the ISS orbits over a sea of thunderclouds, it’s not rare for astronauts to witness an impressive amount of lightning. What is unusual, however, is seeing lightning sprites, which were <a href="http://earthobservatory.nasa.gov/IOTD/view.php?id=86463">observed on August 10th</a> by astronauts aboard the space station.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">ISS astronauts spotted a sprite (the red jellyfish-like structure on the right of the image) appearing above thunder clouds on August 10, 2015.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Sprites are electrical discharges, similar to thunder lights. However, instead of occurring in the lower layer of Earth’s atmosphere, these very fast, red-coloured discharges (due to the excited nitrogen at this altitude) occur much higher up and are as such difficult to observe from the ground.</p>
<h2>2. Sunrises and sunsets</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.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">Sunset over the Indian Ocean.</span>
<span class="attribution"><span class="source">NASA/ESA/G Bacon</span></span>
</figcaption>
</figure>
<p>With the ISS orbiting the Earth every 90 minutes, astronauts can see the Sun rise and set around 16 times every 24 hours. The dramatic views from the station display a rainbow-like horizon as the Sun appears and disappears beyond the horizon.</p>
<p>The changes in colour are due to the angle of the solar rays and their scattering in the Earth’s atmosphere. If similar jaw-dropping views can be seen from Earth, seeing our mother planet lit up in the rising Sun certainly adds to the intensity of the picture.</p>
<h2>3. Stars and the Milky Way</h2>
<figure>
<iframe src="https://player.vimeo.com/video/38409143" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">Amazing sightings of distant astronomical objects as seen from the space shuttle.</span></figcaption>
</figure>
<p>From the ground, atmospheric conditions and light pollution affect our ability to see stars and other celestial bodies. As light travels through layers of hot and cold air, the bending of its rays render a flickering image of these distant objects, while atmospheric particles such as dust prevent from seeing fainter objects such as nebulae and galaxies.</p>
<p>The lack of an atmosphere at the orbiting altitude of the ISS allows the residents on the space station to see the stars, the Milky Way and other astronomical features with much greater clarity than is possible on Earth.</p>
<h2>4. Meteor showers</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The disintegration of a Perseid meteor photographed in August 2011 from the ISS.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Astronauts aboard the ISS can also witness the disintegration of meteoroids in the Earth’s atmosphere. Those small bodies are fragments detached from celestial bodies such as asteroids and comets. As they enter in the Earth’s atmosphere at great speed, the heat due to the body interaction with air rapidly destroys them. Whereas the chance of seeing them from the ground is very much weather dependent, being on the ISS guarantees the best seats to watch these shooting stars flaming across our planet’s sky.</p>
<h2>5. Auroras</h2>
<p>Also known as northern and southern lights, auroras are created when solar storms, consisting of large magnetised clouds of energetic particles launched from the sun, or strong <a href="http://www.swpc.noaa.gov/phenomena/solar-wind">solar wind</a>, interact with the Earth’s magnetic shield. Upon collision with the Earth, these solar streams energise particles within the planet’s magnetic shield.</p>
<figure>
<iframe src="https://player.vimeo.com/video/130263115" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">Time lapses showing the ISS travelling through auroras.</span></figcaption>
</figure>
<p>When they enter the upper layer of the Earth’s atmosphere, these energetic particles excite nitrogen and oxygen atoms present at these altitudes. Then when they return from their excited state, these atoms emit light of different colours indicative of the amount of energy they absorbed. This typically produces green and red, ribbon-like curtains. </p>
<h2>6. Cosmic rays</h2>
<p><a href="http://helios.gsfc.nasa.gov/gcr.html">Galactic cosmic rays</a> aren’t really a phenomenon you can see. These energetic sub-atomic particles come from intense astronomical sources such as exploding stars or black holes. If they pass into the body they can damage tissue and break DNA, causing various diseases over the course of time.</p>
<p>Most cosmic rays do not penetrate in the thick atmosphere of the Earth. Since the ISS sits outside this protected zone, its astronauts are much more likely to be struck by the particles. Astronauts regularly see <a href="http://www.sciencedirect.com/science/article/pii/S0042698905006735">flashes of light</a> when they close their eyes, which is thought to be caused by cosmic rays interacting with body parts that play role in vision, such as the optic nerve or visual centres in the brain.</p>
<p>Solar storms, which have a strong magnetic structure, act as a shield against cosmic rays. A solar storm passing by the Earth can be indirectly witnessed by astronauts aboard the ISS via a drop in the count of cosmic rays, also known as the “<a href="http://science.nasa.gov/science-news/science-at-nasa/2005/07oct_afraid/">Forbush decrease</a>”. What a sensation it must be to “feel” a storm passing by the Earth’s system.</p><img src="https://counter.theconversation.com/content/46636/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Miho Janvier 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>
Astronauts living on the ISS get to experience the wonders of the universe’s natural phenomena like no one else.
Miho Janvier, Lecturer in Mathematics, University of Dundee
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/45548
2015-08-05T04:47:59Z
2015-08-05T04:47:59Z
How satellites are helping Africa improve weather forecasts
<figure><img src="https://images.theconversation.com/files/90625/original/image-20150803-6013-15lbfk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Nowcasting is a system using satellite images to obtain real-time information before bad weather arrives. </span> <span class="attribution"><span class="source">REUTERS/Mike Hutchings</span></span></figcaption></figure><p>Weather forecasters can save lives. Based on information from weather prediction models, an advisory warning can be sent a few days before a possible severe weather event such as heavy rainfall or strong winds. Closer to the time, further warnings are issued when forecasters have more certainty.</p>
<p>To do this, weather forecasters rely on <a href="https://www.wmo.int/pages/prog/amp/pwsp/Nowcasting.htm">nowcasting</a>. This forecasting relies heavily on remote-sensing tools such as satellite or radar systems. </p>
<p>In countries where radar systems are available and well maintained the data gathered form a crucial part of real-time forecasting systems. But in developing countries radar systems are too expensive to obtain and maintain. </p>
<h2>Real time warning</h2>
<p>In many African countries, basic ground-based observation systems are not adequate to provide a real-time feed of the weather. This lack of data means that the public cannot be warned of severe weather events that could lead to loss of life and property. </p>
<p>But <a href="http://www.eumetsat.int/website/home/index.html">satellite</a> data can provide very useful information in regions where there is no or limited access to expensive observation systems. </p>
<p>Numerical weather prediction data, together with geostationary satellite data, can help nowcasting. This is why the <a href="https://www.wmo.int/pages/index_en.html">World</a> Meteorological Organisation has thrown its weight behind providing nowcasting in countries where advanced observation data is unavailable. It has launched severe weather forecasting demonstration projects to improve nowcasting in data sparse regions around the world. </p>
<h2>Blanket satellite coverage</h2>
<p>The Meteosat Second Generation <a href="http://www.eumetsat.int/website/home/Satellites/CurrentSatellites/Meteosat/index.html">satellite</a> was launched in 2002 by the European Space<a href="http://www.esa.int/About_Us/Welcome_to_ESA"> Agency</a> and the European Organisation for the Exploitation of Meteorological <a href="http://www.eumetsat.int/website/home/AboutUs/WhoWeAre/index.html">Satellites</a>. </p>
<p>This satellite provides full coverage of the African continent with a time resolution of 15 minutes. The numerous visible, infrared and water vapour channels, as well as colour (red-green-blue) combinations of these channels provide reliable data for nowcasting.</p>
<p>When the satellite was launched, an initiative to get experts in Europe to develop applications for various purposes using the 12 channels provided by the satellite also started. Eight satellite application facilities were established each with an area of focus. These include nowcasting and short range forecasting, climate monitoring, numerical weather prediction, and land surface analysis.</p>
<p>The Nowcasting Satellite Application <a href="http://www.nwcsaf.org/HD/MainNS.jsp">facility </a> uses data from the <a href="http://www.eumetsat.int/website/home/Satellites/CurrentSatellites/Meteosat/index.html">geostationary</a> satellite to provide information on clouds related to significant convective systems. By tracking rapidly developing thunderstorms it is possible to identify, monitor and track intense convective system clouds and to detect rapidly developing convective cells. </p>
<h2>Warnings saves lives</h2>
<p>The rapidly developing thunderstorms software distinguishes different phases of the thunderstorm. It does this by using the different satellite channels to determine cloud depth, vertical extent, cloud top temperature, cooling rate and possible convective activity. Using the images of the past hour, it determines direction and speed of movement. This is then estimated for the next 30 minutes. </p>
<p>With knowledge of the phase of the storm and its intended direction, a forecaster can use the information to issue a weather warning. </p>
<p>A satellite based tool, such as the thunderstorms software, should be used with other data sources such as radar systems and surface observations where possible. </p>
<p>The identification and tracking of thunderstorms is a bigger challenge in data sparse regions than in areas in which expensive and extensive ground and remote observation networks exist. Warning the public about pending severe weather events is the mandate of all operational weather services. They have the power to save lives as well as protect property. </p>
<blockquote>
<p>This article is based on an article <a href="http://dx.doi.org/10.17159/sajs.2015/20140402">published</a> in the South African Journal of Science in July 2015.</p>
</blockquote><img src="https://counter.theconversation.com/content/45548/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Estelle de Coning receives funding from WRC and works for SA Weather Service.</span></em></p>
Being able to predict the weather can save lives. Using new technology forecasters are able to provide realtime warning of bad weather ahead.
Estelle de Coning, Chief Scientist at SA Weather Service: Nowcasting and very short range forecasting and part-time lecturer at the University of Pretoria , University of Pretoria
Licensed as Creative Commons – attribution, no derivatives.