tag:theconversation.com,2011:/us/topics/global-cooling-5942/articlesGlobal cooling – The Conversation2023-08-15T06:03:17Ztag:theconversation.com,2011:article/2111082023-08-15T06:03:17Z2023-08-15T06:03:17ZResearch reveals who’s been hit hardest by global warming in their lifetime - and the answer may surprise you<p>Earth is warming and the signs of climate change are everywhere. We’ve seen it in the past few weeks as temperatures hit record highs around the world – both in the Northern Hemisphere and the <a href="https://theconversation.com/why-is-australia-having-such-a-warm-winter-a-climate-expert-explains-210693">warm Australian winter</a>.</p>
<p>Global warming is caused by humanity’s greenhouse gas emissions, which continue at <a href="https://theconversation.com/global-carbon-emissions-at-record-levels-with-no-signs-of-shrinking-new-data-shows-humanity-has-a-monumental-task-ahead-193108">near-record pace</a>. These emissions are predominantly generated by people in the world’s wealthiest regions.</p>
<p>Our world-first analysis, <a href="https://iopscience.iop.org/article/10.1088/2752-5295/aceff2">published today</a>, examines the experience of global warming over the lifetimes of people around the world: young and old, rich and poor. We sought to identify who has perceived warmer temperatures most keenly.</p>
<p>We found middle-aged people in equatorial regions have lived through the most perceptible warming in their lifetimes. But many young people in lower-income countries could experience unrecognisable changes in their local climate later in life, unless the world rapidly tackles climate change.</p>
<h2>Measuring the climate change experience</h2>
<p>We examined temperature data and population demographics information from around the world.</p>
<p>Key to our analysis was the fact that not all warming is due to human activity. Some of it is caused by natural, year-to-year variations in Earth’s climate. </p>
<p>These natural ups and downs are due to a number of factors. They include variations in the energy Earth receives from the sun, the effects of volcanic eruptions, and transfers of heat between the atmosphere and the ocean.</p>
<p>This variability is stronger in mid-to-high-latitude parts of the world (those further from the equator) than in low-latitude areas (in equatorial regions). That’s because the weather systems further away from the equator draw in hot or cold air from neighbouring areas, but equatorial areas don’t receive cold air at all.</p>
<p>That’s why, for example, the annual average temperature in New York is naturally more variable than in the city of Kinshasa (in the Democratic Republic of Congo). </p>
<p>To account for this, we applied what’s known as the “<a href="https://archive.ipcc.ch/ipccreports/tar/wg1/346.htm#:%7E:text=The%20%EF%BF%BDsignal%20to%20noise,to%20this%20natural%20variability%20noise.">signal-to-noise ratio</a>” at each location we studied. That allowed us to separate the strength of the climate change “signal” from the “noise” of natural variability. </p>
<p>Making this distinction is important. The less naturally variable the temperature, the clearer the effects of warming. So warming in Kinshasa over the past 50 years has been much more perceptible than in New York.</p>
<p>Our study examined two central questions. First, we wanted to know, for every location in the world, how clearly global warming could be perceived, relative to natural temperature variability.</p>
<p>Second, we wanted to know where this perceived change was most clear over human lifetimes. </p>
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<a href="https://images.theconversation.com/files/541474/original/file-20230807-17-ogjdti.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Annual-average temperatures at four major cities with signal-to-noise ratios shown for 20, 50 and 80 years up to 2021." src="https://images.theconversation.com/files/541474/original/file-20230807-17-ogjdti.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541474/original/file-20230807-17-ogjdti.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541474/original/file-20230807-17-ogjdti.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541474/original/file-20230807-17-ogjdti.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541474/original/file-20230807-17-ogjdti.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541474/original/file-20230807-17-ogjdti.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541474/original/file-20230807-17-ogjdti.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Annual-average temperatures at four major cities with signal-to-noise ratios shown for 20, 50 and 80 years up to 2021.</span>
<span class="attribution"><span class="source">Author provided</span></span>
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<h2>Our results</h2>
<p>So what did we find? As expected, the most perceptible warming is found in tropical regions – those near the equator. This includes developing parts of the world that constitute the Global South – such as Africa, Latin America and the Caribbean, and Asia.</p>
<p>Household incomes in the Global South are typically lower than in industrialised nations (known as the Global North). We might, then, conclude people in the poorest parts of the world have experienced the most perceptible global warming over their lifetimes. But that’s not always the case.</p>
<p>Why? Because most parts of the Global South have younger populations than wealthier regions. And some people under the age of 20, including in northern India and parts of Sub-Saharan Africa, haven’t experienced warming over their lifetimes.</p>
<p>In these places, the lack of recent warming is likely down to a few factors: natural climate variability, and the local cooling effect of particles released into the atmosphere from <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac3b7a">pollution</a> and changes in land use.</p>
<p>There’s another complication. Some populated regions of the world also experienced slight cooling in the mid-20th century, primarily driven by human-caused <a href="https://www.nature.com/articles/nature10946">aerosol emissions</a>.</p>
<p>So, many people born earlier than the 1950s have experienced less perceptible warming in their local area than those born in the 1960s and 1970s. This may seem counter-intuitive. But a cooling trend in the first few decades of one’s life means the warming experienced over an entire lifespan (from birth until today) is smaller and less detectable.</p>
<p>So what does all this mean? People in equatorial areas born in the 1960s and 1970s – now aged between about 45 and 65 – have experienced more perceptible warming than anyone else on Earth.</p>
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<h2>Rich countries must act</h2>
<p>Our findings are important, for several reasons.</p>
<p>Identifying who has experienced significant global warming in their lives may help explain <a href="https://www.nature.com/articles/nclimate2660">attitudes to tackling climate change</a>.</p>
<p>Our findings also raise significant issues of fairness and equity.</p>
<p>Humanity will continue to warm the planet until we reach global net-zero emissions. This means many young people in lower-income countries may, later in life, experience a local climate that is unrecognisable to that of their youth. </p>
<p>Of course, warming temperatures are not the only way people experience climate change. Others include sea-level rise, more intense drought and rainfall extremes. We know many of these impacts are felt most acutely by <a href="https://www.aljazeera.com/opinions/2022/5/11/climate-change-is-devastating-the-global-south">the most vulnerable populations</a>.</p>
<p>Cumulative greenhouse gas emissions are much higher in the Global North, due to economic development. To address this inequality, rich industrialised nations must take a leading role in reducing emissions to net-zero, and helping vulnerable countries adapt to climate change.</p>
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Read more:
<a href="https://theconversation.com/why-is-australia-having-such-a-warm-winter-a-climate-expert-explains-210693">Why is Australia having such a warm winter? A climate expert explains</a>
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<img src="https://counter.theconversation.com/content/211108/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>Ed Hawkins receives funding from the UK Natural Environment Research Council.</span></em></p><p class="fine-print"><em><span>Hunter Douglas receives funding from New Zealand's Ministry of Business, Innovation & Employment (MBIE). </span></em></p><p class="fine-print"><em><span>Luke Harrington receives funding from New Zealand's Ministry of Business, Innovation & Employment (MBIE) and Health Research Council. </span></em></p>Middle-aged people in equatorial regions have lived through the most perceptible warming in their lifetimes. But many others may experience unrecognisable changes in their local climate later in life.Andrew King, Senior Lecturer in Climate Science, The University of MelbourneEd Hawkins, Professor of Climate Science, University of ReadingHunter Douglas, PhD Candidate, Te Herenga Waka — Victoria University of WellingtonLuke Harrington, Senior Lecturer in Climate Change, University of WaikatoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1877812022-08-11T20:05:02Z2022-08-11T20:05:02ZBeyond net-zero: we should, if we can, cool the planet back to pre-industrial levels<figure><img src="https://images.theconversation.com/files/478432/original/file-20220810-11-eziox2.jpg?ixlib=rb-1.1.0&rect=23%2C31%2C5303%2C3514&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Marc Pell/Unsplash</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The world’s focus is sharply fixed on achieving <a href="https://climateactiontracker.org/methodology/net-zero-targets">net-zero emissions</a>, yet surprisingly little thought has been given to what comes afterwards. In our <a href="https://www.nature.com/articles/s41558-022-01446-x">new paper</a>, published today in Nature Climate Change, we discuss the big unknowns in a post net-zero world. </p>
<p>It’s vital that we understand the consequences of our choices when it comes to greenhouse gas emissions and what comes next. The pathways we choose before and after reaching global net-zero emissions might mean the difference between a planet that remains habitable and one where many parts become inhospitable. </p>
<p>At the moment, human activities have a warming effect on the planet. But achieving our climate policy goals would take humanity into the uncharted territory of being able to <em>cool</em> the planet.</p>
<p>Being able to cool the planet raises a number of questions. Principally, how fast would we want the planet to cool, and what global average temperature should we aim for?</p>
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Read more:
<a href="https://theconversation.com/global-emissions-almost-back-to-pre-pandemic-levels-after-unprecedented-drop-in-2020-new-analysis-shows-170866">Global emissions almost back to pre-pandemic levels after unprecedented drop in 2020, new analysis shows</a>
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<h2>How are our emissions changing?</h2>
<p>Our collective greenhouse gas emissions have warmed the planet <a href="https://globalwarmingindex.org/">about 1.2°C</a>, relative to pre-industrial temperatures. In fact, despite all the talk about reducing emissions, global carbon dioxide emissions are <a href="https://theconversation.com/global-emissions-almost-back-to-pre-pandemic-levels-after-unprecedented-drop-in-2020-new-analysis-shows-170866">at near-record levels</a>. </p>
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<a href="https://images.theconversation.com/files/477803/original/file-20220805-5530-kyf2wz.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/477803/original/file-20220805-5530-kyf2wz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/477803/original/file-20220805-5530-kyf2wz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=374&fit=crop&dpr=1 600w, https://images.theconversation.com/files/477803/original/file-20220805-5530-kyf2wz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=374&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/477803/original/file-20220805-5530-kyf2wz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=374&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/477803/original/file-20220805-5530-kyf2wz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=470&fit=crop&dpr=1 754w, https://images.theconversation.com/files/477803/original/file-20220805-5530-kyf2wz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=470&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/477803/original/file-20220805-5530-kyf2wz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=470&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Emissions have rebounded following the reductions seen during the pandemic-induced lockdowns. Looking back further we can see that carbon dioxide emissions have roughly quadrupled since 1960.</span>
<span class="attribution"><span class="source">Global Carbon Project</span></span>
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<p>Some countries have successfully reduced their greenhouse gas emissions in recent years, such as the United Kingdom which has <a href="https://www.carbonbrief.org/analysis-uk-is-now-halfway-to-meeting-its-net-zero-emissions-target/.">halved greenhouse gas emissions</a> relative to 1990.</p>
<p>There is also <a href="https://theconversation.com/the-new-global-methane-pledge-can-buy-time-while-the-world-drastically-reduces-fossil-fuel-use-171182">greater push</a> from major emitters such as the United States and the European Union – as well as <a href="https://theconversation.com/pacific-islands-are-back-on-the-map-and-climate-action-is-not-negotiable-for-would-be-allies-187086">countries that emit less</a> but already experience climate change impacts – to take stronger steps to limit the damage we are doing to the climate.</p>
<p>Reducing greenhouse gas emissions and reaching net-zero are humanity’s greatest challenges. As long as greenhouse gas emissions remain substantially above net-zero we will continue to warm the planet. </p>
<p>To be in line with the Paris Agreement goal of limiting global warming to well below 2°C above pre-industrial levels this century, we need to drastically reduce our emissions. </p>
<p>We also need to increase our uptake of carbon from the atmosphere through developing and implementing <a href="https://theconversation.com/on-top-of-drastic-emissions-cuts-ipcc-finds-large-scale-co-removal-from-air-will-be-essential-to-meeting-targets-180663">drawdown technology</a>. </p>
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Read more:
<a href="https://theconversation.com/on-top-of-drastic-emissions-cuts-ipcc-finds-large-scale-co-removal-from-air-will-be-essential-to-meeting-targets-180663">On top of drastic emissions cuts, IPCC finds large-scale CO₂ removal from air will be "essential" to meeting targets</a>
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<h2>What will come after net-zero?</h2>
<p>Net-zero emissions will be reached when humanity’s greenhouse gas emissions into the atmosphere are balanced by their removal from the atmosphere. We would likely need to reach global net-zero well within <a href="https://www.carbonbrief.org/analysis-do-cop26-promises-keep-global-warming-below-2c/">the next 50 years</a> to keep global warming well below 2°C. </p>
<p>If we achieve this, we could continue the process of decarbonisation to reach net-negative greenhouse gas emissions – where more of humanity’s greenhouse gas emissions are removed from the atmosphere than released into it. </p>
<p>This would need to be achieved through a combination of “negative emissions” <a href="https://theconversation.com/the-morrison-government-wants-to-suck-co-out-of-the-atmosphere-here-are-7-ways-to-do-it-144941">technologies</a>, likely including some not invented yet, and land use changes such as reforestation.</p>
<p>Continued net-negative emissions will cause the planet to cool as greenhouse gas concentrations in the atmosphere fall. This is because the greenhouse effect, where gases such as carbon dioxide absorb radiation from Earth and warm the atmosphere, would weaken.</p>
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Read more:
<a href="https://theconversation.com/the-morrison-government-wants-to-suck-co-out-of-the-atmosphere-here-are-7-ways-to-do-it-144941">The Morrison government wants to suck CO₂ out of the atmosphere. Here are 7 ways to do it</a>
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<p>Currently, there’s almost no focus from governments, or indeed scientists, on the consequences of meeting our policy goals and going beyond net-zero. But this would be a turning point as the world would begin to cool. </p>
<p>Land would cool faster than the ocean. Indeed, some people may experience substantial cooling over their lifetimes – an unfamiliar concept to grasp in our warming climate. </p>
<p>These changes would be accompanied by effects on weather extremes and impacts to weather and climate-sensitive industries. While there’s not much research on this yet, we could, for example, see shipping routes close up as ice regrows in polar regions.</p>
<p>In the long-term, the best <a href="https://arxiv.org/ftp/arxiv/papers/0804/0804.1126.pdf">target global temperature</a> for the planet might be something akin to a <a href="https://theconversation.com/what-is-a-pre-industrial-climate-and-why-does-it-matter-78601">pre-industrial climate</a>, with the human effect on Earth’s climate receding. </p>
<p>In <a href="https://www.nature.com/articles/s41558-022-01446-x">our paper</a> we call for a new set of climate model experiments that allow us to understand the range of possible future climates after net-zero.</p>
<p>Any decisions must be informed by an understanding of the consequences of different choices for a post net-zero climate. For example, competing interests between countries and industries may make global agreements more challenging in a post net-zero world. </p>
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<span class="caption">The Earth has warmed to date but after achieving net-zero emissions it will cool. We need new climate model simulations to understand this. Observed global mean surface temperature (GMST) comes from the Berkeley Earth dataset. The red, orange and blue lines illustrate possible scenarios for a post net-zero climate for which we wish to understand the implications.</span>
<span class="attribution"><span class="source">Author provided</span></span>
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<h2>Why does this matter now?</h2>
<p>Reading this article, you may feel we’re getting ahead of ourselves. After all, as highlighted, global greenhouse gas emissions remain at near-record highs.</p>
<p>A key factor that will affect the behaviour of the climate system after net-zero emissions would be the maximum level of global warming that we peak at. This is dictated by our current and near-future emissions. </p>
<p>If we fail to meet the Paris Agreement and peak global warming reaches 2°C or more, then future generations will endure the effects of higher sea levels and other possible <a href="https://www.carbonbrief.org/explainer-nine-tipping-points-that-could-be-triggered-by-climate-change/">disastrous climate changes</a> for many centuries to come. </p>
<p>Our understanding of post net-zero impacts of different peak levels of global warming is extremely limited.</p>
<p>Reducing greenhouse gas emissions through decarbonisation remains our key priority. The more we can suppress global warming by reaching net-zero emissions as early as possible, the more we limit potential disastrous effects and the need to cool the planet in a post net-zero world. </p>
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<img src="https://counter.theconversation.com/content/187781/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>Celia McMichael receives funding from the Australian Research Council, the National Health and Medical Research Council, Australian Red Cross, and the World Health Organization. </span></em></p><p class="fine-print"><em><span>Kale Sniderman receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Kathryn Bowen has received funding for climate and health research, policy advice and technical assistance from the National Health and Medical Research Council, Australian Department of Foreign Affairs and Trade, WHO, Asian Development Bank, UNDP, UNEP, USAID, GIZ, EU, Future Earth, City of Melbourne, Victorian Department of Health. She is affiliated with the Climate and Health Alliance as a member of the Advisory Board and sits on the Science Committee of the World Adaptation Science Program.</span></em></p><p class="fine-print"><em><span>Tilo Ziehn receives funding from the Australian Government under the National Environmental Science Program. </span></em></p><p class="fine-print"><em><span>Zebedee Nicholls receives funding from the European Union under the Horizon 2020 Program. He is also a co-founder of Climate Resource, which connects governments and businesses with the latest climate science.</span></em></p><p class="fine-print"><em><span>Harry McClelland and Jacqueline Peel 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>Our ability to cool the planet takes humanity into uncharted territory. In a new paper published today, researchers discuss the big unknowns in a post net-zero world.Andrew King, Senior Lecturer in Climate Science, The University of MelbourneCelia McMichael, Senior Lecturer in Geography, The University of MelbourneHarry McClelland, Lecturer in Geomicrobiology, The University of MelbourneJacqueline Peel, Director, Melbourne Climate Futures, The University of MelbourneKale Sniderman, Senior Research Fellow, The University of MelbourneKathryn Bowen, Professor - Environment, Climate and Global Health at Melbourne Climate Futures and Melbourne School of Population and Global Health, University of Melbourne, The University of MelbourneTilo Ziehn, Principal Research Scientist, CSIROZebedee Nicholls, Research Fellow at The International Institute for Applied Systems Analysis (IIASA) and Melbourne Climate Futures, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1411962020-06-22T19:05:49Z2020-06-22T19:05:49ZDid a volcanic eruption in Alaska help end the Roman republic?<figure><img src="https://images.theconversation.com/files/343206/original/file-20200622-54981-zagf3c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The death of Caesar.</span> <span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Assassination_of_Julius_Caesar#/media/File:Vincenzo_Camuccini_-_La_morte_di_Cesare.jpg">Vincenzo Camuccini/Wikipedia</a></span></figcaption></figure><p>Julius Caesar was assassinated on the Ides of March (March 15) in 44BC and a bloody civil war followed. This brought down the Roman republic and replaced it with a monarchy led by Caesar’s nephew Octavian, who in 27BC became the emperor Augustus. A group of scientists and historians suggest that a massive volcanic eruption in Alaska played a role in this transition, as well as helping to finish off Cleopatra’s Egypt. </p>
<p><a href="https://www.pnas.org/cgi/doi/10.1073/pnas.2002722117">The study</a>, led by Joseph R McConnell of the Desert Research Institute in Nevada, demonstrates how careful scientific research on ancient climate can add context to our more traditional scholarship. At the same time, the research raises challenging questions about how we integrate such data into historical narratives without oversimplifying the story.</p>
<p>Caesar’s assassination came at a time of unrest for the ancient Mediterranean. This was exacerbated by strange atmospheric phenomena, and unusually cold, wet weather that caused crop failures, food shortages, disease, and even the failure of the annual Nile flood on which Egyptian agriculture relied. In 1988, classicist Phyllis Forsyth <a href="https://doi.org/10.2307/25010878">suggested that</a> an eruption of Mount Etna in Sicily in 44BC was responsible for these problems because the aerosol particles released into the atmosphere would reflect sunlight back into space and cool the climate.</p>
<p>While McConnell’s team agreed that the Etna eruption could have caused some of these disruptions, they have now argued it was a later massive eruption of the Okmok volcano in Alaska that altered the climate and helped weaken the Roman and Egyptian states. They drew on three strands of evidence to support their claim.</p>
<p>The first came from ice samples taken from deep in the Arctic ice sheets, which trapped air as they formed over hundreds of thousands of years, providing a datable record of atmospheric conditions. These <a href="https://climate.nasa.gov/news/2616/core-questions-an-introduction-to-ice-cores/">ice cores</a> showed there was a spike in solid particles, dust and ash from a volcanic eruption early in 43BC. The researchers then showed the geochemical properties of these particles matched with samples from the Okmok volcano.</p>
<p>For evidence for the ancient climate, they then looked at tree rings and speleothems (stalactites and stalagmites) from various parts of the northern hemisphere, including China, Europe and North America. These suggested that 43BC to 34BC was the fourth coldest decade in the last 2,500 years, and 43BC and 42BC were the second and eighth coldest years.</p>
<p>Data from the research was then fed into a computer-based climate modelling system called the <a href="http://www.cesm.ucar.edu/">Community Earth System Model</a> (CESM), which produced a climate simulation. This showed that the eruption of Okmok could have caused cooling of 0.7˚C to 7.4˚C across the southern Mediterranean and northern Africa in 43-42BC, which persisted into the 30s BC. </p>
<p>This could also have led to increased summer and autumn rainfall that would have damaged crops. At the same time, drier conditions in the upper reaches of the Nile may have led to its failure to flood in 43BC and 42BC.</p>
<p>In this way, McConnell’s team make a good case for Okmok’s potential impact on temperature, rainfall and a resulting change in agricultural production in 43BC and after. But the conclusions they draw about its impact on the bigger historical picture are less certain. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/343278/original/file-20200622-55001-12l79o4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343278/original/file-20200622-55001-12l79o4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=242&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343278/original/file-20200622-55001-12l79o4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=242&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343278/original/file-20200622-55001-12l79o4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=242&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343278/original/file-20200622-55001-12l79o4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=304&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343278/original/file-20200622-55001-12l79o4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=304&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343278/original/file-20200622-55001-12l79o4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=304&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The 10-km wide caldera on Alaska’s Unmak Island formed during the 43 BCE Okmok II eruption..</span>
<span class="attribution"><span class="source">Kerry Key (Columbia University, New York, NY)</span></span>
</figcaption>
</figure>
<p>One of the major problems with scientific papers in which climate events are blamed for major historical changes is that they are not able to fit in much analysis of the historical issues themselves. These tend to be reduced to straightforward events or problems that can then be easily “explained” or “solved” by science. The realities, when we zoom in, are much more messy.</p>
<p>The transition of Rome from a republic to a monarchy – via a period of rule by the competing triumvirate of Octavian, Mark Antony and Lepidus – was a long and complex process. It involved <a href="https://www.cambridge.org/core/books/roman-power/romans-against-each-other-from-republic-to-monarchy/85B34D739964F8FC708247CF89424EEF">many people and parties</a> with different motivations and plans. The whole period poses a challenge to historians and <a href="https://global.oup.com/academic/product/the-roman-revolution-9780192803207?cc=gb&lang=en&">entire books</a> have sought to describe and explain it. </p>
<p>But this civil war was only the latest in a series of escalating conflicts in the later period of the republic, in which the behaviour of earlier figures, like Sulla, who had seized control of Rome decades earlier, became precedents for <a href="https://www.cambridge.org/core/books/rome-and-the-making-of-a-world-state-150-bce20-ce/spiral-of-violence-10480-bce/38567A53DDAAAF43D30F5AE8E7943E2F">what might be possible</a>. </p>
<p>The outcome of the war and the establishment of a monarchy was not inevitable. Rather than a narrative of crisis, decline and fall, the period can even be seen as one of <a href="https://www.cambridge.org/core/books/rome-and-the-making-of-a-world-state-150-bce20-ce/war-of-the-world-4930-bce/5E4B8CEEA17CF250A20E5A2BF46B59DA">political experimentation</a>, of state formation, of attempts to solve the problems that beset the republic.</p>
<h2>More complicated picture</h2>
<p>This period of war relied on manpower and the capacity of state apparatus to extract and redirect food and money from society. Despite ancient sources that report difficulties with this extraction, we should remember that the machinery that enabled it remained essentially in working order. Without it, armies would not have been fed and the civil wars would not have been able to happen. </p>
<p>And while the failure of the Nile floods in 43BC and 42BC would certainly have been bad, Egypt was up and running again soon after. Antony and Cleopatra were able to raise and maintain armies, fight, and were finally defeated only in 31BC in the naval battle of Actium. If people were going hungry, the conflict itself and profiteering grain dealers were perhaps more to blame than the climate (as was the case in <a href="https://www.hrw.org/sites/default/files/reports/Ethiopia919.pdf">the Ethiopian famines of the 1980s</a>).</p>
<p>The effects of Okmok’s eruption in 43BC may have been serious, as McConnell’s team argue. But it is also very clear that personal, political and military decisions – and chance – were the direct determiners of how history unfolded in Rome and Egypt. There were many points in the years after 44 BC at which things could have turned out quite differently, whatever the climate was like. </p>
<p>The military activity of the period alone would seem to show that both Rome and Egypt were quite resilient, overall, in the face of natural hazards, and as states they continued to transform in an ever-changing world.</p><img src="https://counter.theconversation.com/content/141196/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Guy D. Middleton receives funding from the European Regional Development Fund-Project “Creativity and Adaptability as Conditions of the Success of Europe in an Interrelated World” (no. CZ.02.1.01/0.0/0.0/16_019/0000734).</span></em></p>New research suggests ancient climate change shaped the fate of western civilisation.Guy Middleton, Visiting Fellow, School of History, Classics and Archaeology, Newcastle UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1255902019-10-23T13:01:48Z2019-10-23T13:01:48ZTropical ocean bacteria help pump CO2 out of the atmosphere - new study<p>What will our climate look like in 200 years? The answer to this question depends on our emissions of greenhouse gases, but also on all the complex and interlinked physical and biological processes that make up the climate system. One of these processes has a surprising source: tiny bacteria living in tropical oceans. <a href="https://www.nature.com/articles/s41467-019-12549-z">Our latest research</a> shows how important some special bacteria, called nitrogen fixers, are to the global process of pulling carbon dioxide (CO₂) out of the atmosphere.</p>
<p>The story begins with another type of single-celled microbe known as phytoplankton. Like plants, phytoplankton create their own food using sunlight and CO₂, absorbing much of the CO₂ as they grow. When they die, they sink to the deep ocean, taking the CO₂ with them.</p>
<p>The constant removal of CO₂ from the air to the surface of the water and then to the deep ocean is termed the “<a href="https://www.us-ocb.org/biological-pump/">biological pump</a>”. The stronger the collective biological pump action of phytoplankton, the less CO₂ in the atmosphere and the cooler the planet.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/298092/original/file-20191022-28133-vb48o7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/298092/original/file-20191022-28133-vb48o7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/298092/original/file-20191022-28133-vb48o7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/298092/original/file-20191022-28133-vb48o7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/298092/original/file-20191022-28133-vb48o7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/298092/original/file-20191022-28133-vb48o7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/298092/original/file-20191022-28133-vb48o7.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 cold ocean of an Ice Age drew carbon dioxide out of the atmosphere.</span>
<span class="attribution"><span class="source">Pearse J. Buchanan</span></span>
</figcaption>
</figure>
<p>The cold climate of the Earth’s ice ages was due in part to a <a href="https://www.sciencedirect.com/science/article/pii/B9780080959757006185?via%253Dihub">more vigorous biological pumping</a>. At these times, global temperatures were 5°C lower than today. Glaciers covered the Siberian, European and North American landmasses, and sea level dropped more than 100 metres. These extreme conditions were brought about by a decline in atmospheric CO₂ of about 100 parts per million.</p>
<p>We know that <a href="https://theconversation.com/carbon-dioxide-trapped-by-ice-age-oceans-raises-questions-for-future-81070">the ocean absorbed the CO₂</a>, and that the increase in drawdown came partly from a change in <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016PA003024">ocean circulation</a>. The ability of the ocean to hold CO₂ depends on how it circulates, with some modes of circulation enabling more storage than others. But this only explains between <a href="https://www.clim-past.net/12/2271/2016/">a third</a> and <a href="https://www.sciencedirect.com/science/article/pii/S0012821X17302753">two-thirds</a> of the CO₂ drawdown. The rest was due to a strengthening of the biological pump. </p>
<h2>Dust and nitrogen fixers</h2>
<p>For years, scientists have tried to explain this strengthening by looking at what happened to cold-water phytoplankton living in places such as the Southern Ocean. This ocean tends to be starved of iron, a nutrient essential for photosynthesis. The climate during the ice ages contained a lot of iron-rich dust, so there is <a href="https://www.princeton.edu/news/2014/03/21/dust-wind-drove-iron-fertilization-during-ice-age">strong evidence</a> that this stimulated the growth of cold-water phytoplankton.</p>
<p>But recent <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL064250">climate modelling</a> has shown that fertilisation of the Southern Ocean with iron didn’t lead to enough CO₂ absorption to explain the ice ages. So, along with our colleagues <a href="https://theconversation.com/profiles/steven-phipps-91100">Steven Phipps</a> and <a href="https://theconversation.com/profiles/nathan-bindoff-593745">Nathan Bindoff</a>, we investigated the role of phytoplankton that live in the warm, tropical ocean.</p>
<p>Tropical phytoplankton tend to be <a href="https://www.eurekalert.org/pub_releases/2013-04/nocs-ona041013.php">starved of nitrogen</a>, not iron. But these waters also contain a special group of bacteria that can “fix” nitrogen, turning nitrogen gas into forms that can be used by living things. The presence of nitrogen-fixing bacteria therefore fertilises warm-water phytoplankton, enabling their growth and strengthening the biological pump.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/297919/original/file-20191021-56234-17cp11t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/297919/original/file-20191021-56234-17cp11t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=405&fit=crop&dpr=1 600w, https://images.theconversation.com/files/297919/original/file-20191021-56234-17cp11t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=405&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/297919/original/file-20191021-56234-17cp11t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=405&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/297919/original/file-20191021-56234-17cp11t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=509&fit=crop&dpr=1 754w, https://images.theconversation.com/files/297919/original/file-20191021-56234-17cp11t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=509&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/297919/original/file-20191021-56234-17cp11t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=509&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A dust storm blows over the Atlantic Ocean.</span>
<span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/2137">NASA</a></span>
</figcaption>
</figure>
<p>But much like cold-water phytoplankton, nitrogen fixers also need iron. In fact, nitrogen fixation is an iron-hungry process, and colonies made up of millions of nitrogen fixers <a href="https://static-content.springer.com/esm/art%253A10.1038%252Fngeo1181/MediaObjects/41561_2011_BFngeo1181_MOESM298_ESM.wmv">work together</a> to capture and extract the iron from dust particles. Realising the potential of nitrogen fixers, we added them to an ocean climate model and found that they played a pivotal role in strengthening the biological pump when the ocean is fertilised with iron, as during the ice ages.</p>
<p>This finding reveals how the biological pump could have been strengthened everywhere, in both the Southern Ocean and the tropics. Only a global view of the biological pump can explain the full drawdown of CO₂ during the ice ages.</p>
<h2>Climate change today</h2>
<p>Given our current need to reduce the amount of CO₂ in the atmosphere, it may seem <a href="https://blog.nationalgeographic.org/2012/10/18/iron-fertilization-savior-to-climate-change-or-ocean-dumping/">tempting</a> to try fertilising the ocean with iron in order strengthen the biological pump again. Realistically, a lot more research would need to be done to determine the potential and the risks of this action. </p>
<p>But even if we don’t try to geoengineer the planet, changes in the biological pump may be coming our way. There is <a href="https://phys.org/news/2013-12-deep-sea-corals-long-term-shift-pacific.html">some evidence</a> that nitrogen fixation has been increasing since the industrial revolution, a sign of a strengthening biological pump.</p>
<p>One thing is clear, the biological pump will help determine the long-term trajectory of Earth’s climate. If (and hopefully when) we stop our emissions, the biological pump will come to the forefront as a major control of atmospheric CO₂. How it responds will either amplify or ameliorate our greenhouse problem, and so it is imperative that we continue to build our understanding.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=140&fit=crop&dpr=1 600w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=140&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=140&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=176&fit=crop&dpr=1 754w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=176&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=176&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
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<p><em><a href="https://theconversation.com/imagine-newsletter-researchers-think-of-a-world-with-climate-action-113443?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=Imagineheader1125590">Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.</a></em></p><img src="https://counter.theconversation.com/content/125590/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Pearse James Buchanan received funding from an Australian Postgraduate Fulbright award and receives funding from the Natural Environmental Research Council (NERC) in the United Kingdom.</span></em></p><p class="fine-print"><em><span>Richard Matear receives funding from CSIRO. </span></em></p><p class="fine-print"><em><span>Zanna Chase receives funding from the Australian Research Council</span></em></p>Nitrogen-fixing bacteria help tropical phytoplankton absorb carbon dioxide, creating a biological pump in the oceans.Pearse James Buchanan, Postdoctoral Researcher in Biological Oceanography, University of LiverpoolRichard Matear, Climate Prediction Group Leader, CSIROZanna Chase, Associate professor, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1105492019-01-31T12:46:48Z2019-01-31T12:46:48ZEuropean colonisation of the Americas killed 10% of world population and caused global cooling<figure><img src="https://images.theconversation.com/files/255769/original/file-20190128-108367-1t3cqmc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Wilhem Berrouet's impression of Columbus arriving in America.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/130765784@N06/42694898071/in/photolist-hndGU-hndB9-hpU9J-4tmBSb-dhNRfN-nDfUB-2JtRiY-vmUKE-8W8D7B-hndMt-vmVjj-4thz5B-4tmCiJ-vn2qy-vn2ME-4tmums-4tmuLo-wNmkZ-6qLTFN-6qLSMw-4thrs4-6r3oFM-vn36d-vmVGk-6r3mRi-6tmL2d-6thB4Z-xpatFo-4tmBC3-vmUrF-8StTDj-6qGGMe-6qLSuf-6qLSfQ-6qGHUt-283NvJg-eTD1ss">Salon de la Mappemonde/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>While Europe was in the early days of the Renaissance, there were <a href="https://www.sciencedirect.com/science/article/pii/S0277379118307261">empires in the Americas sustaining more than 60m people</a>. But the first European contact in 1492 brought diseases to the Americas which devastated the native population and the resultant collapse of farming in the Americas was so significant that it may have even cooled the global climate. </p>
<p>The number of people living in North, Central and South America when Columbus arrived is a question that researchers have been trying to answer for decades. Unlike in Europe and China, <a href="https://www.jstor.org/stable/2947274?seq=1#page_scan_tab_contents">no records on the size of indigenous societies</a> in the Americas before 1492 are preserved. To reconstruct population numbers, researchers rely on the first accounts from European eyewitnesses and, in records from after colonial rule was established, tribute payments known as “<a href="https://www.thoughtco.com/spains-american-colonies-encomienda-system-2136545">encomiendas</a>”. This taxation system was only established after European epidemics had ravaged the Americas, so it tells us nothing about the size of pre-colonial populations.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/255772/original/file-20190128-108370-bghxtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/255772/original/file-20190128-108370-bghxtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/255772/original/file-20190128-108370-bghxtl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/255772/original/file-20190128-108370-bghxtl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/255772/original/file-20190128-108370-bghxtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/255772/original/file-20190128-108370-bghxtl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/255772/original/file-20190128-108370-bghxtl.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 coast in Cuba where Columbus arrived in 1492.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/wild-cuban-coast-place-arrival-christopher-1237742905?src=CtcJoMsFJPQBwg53Ox6a-w-1-41">Authentic Travel/Shutterstock</a></span>
</figcaption>
</figure>
<p>Early accounts by European colonists are likely to have overestimated settlement sizes and population to advertise the riches of their newly discovered lands to their feudal sponsors in Europe. But by rejecting these claims and focusing on colonial records instead, <a href="https://www.thebritishacademy.ac.uk/sites/default/files/81p247.pdf">extremely low population estimates</a> were published in the early 20th century which counted the population after disease had ravaged it.</p>
<p>On the other hand, liberal assumptions on, for example, the proportion of the indigenous population that was required to pay tributes or the rates at which people had died led to extraordinarily high estimates.</p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S0277379118307261">Our new study</a> clarifies the size of pre-Columbian populations and their impact on their environment. By combining all published estimates from populations throughout the Americas, we find a probable indigenous population of 60m in 1492. For comparison, <a href="https://www.rug.nl/ggdc/historicaldevelopment/maddison/releases/maddison-project-database-2018">Europe’s population at the time was 70-88m</a> spread over less than half the area.</p>
<h2>The Great Dying</h2>
<p>The large pre-Columbian population sustained itself through farming – there is extensive archaeological evidence for slash-and-burn agriculture, <a href="https://www.smithsonianmag.com/history/farming-like-the-incas-70263217/">terraced fields</a>, <a href="https://www.joseiriartearchaeology.net/categories/research-projects/subcategories/past-human-impacts-in-amazonia/pages/raised-fields-monumental-mounds-ring-ditches">large earthen mounds</a> and home gardens. </p>
<p>By knowing how much agricultural land is required to sustain one person, population numbers can be translated from the area known to be under human land use. We found that 62m hectares of land, or about 10% of the landmass of the Americas, had been farmed or under another human use when Columbus arrived. For comparison, in Europe 23% and in China 20% of land had been used by humans at the time.</p>
<p>This changed in the decades after Europeans first set foot on the island of Hispaniola in 1492 – now Haiti and the Dominican Republic – and the mainland in 1517. Europeans brought measles, smallpox, influenza and the bubonic plague across the Atlantic, with <a href="https://www.nlm.nih.gov/nativevoices/timeline/183.html">devastating consequences for the indigenous populations</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/255774/original/file-20190128-108355-x814hd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/255774/original/file-20190128-108355-x814hd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/255774/original/file-20190128-108355-x814hd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/255774/original/file-20190128-108355-x814hd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/255774/original/file-20190128-108355-x814hd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/255774/original/file-20190128-108355-x814hd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/255774/original/file-20190128-108355-x814hd.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">Incan agricultural terraces in Peru.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/agriculture-centre-terraces-covered-by-grass-1132628009?src=eHPhYo5WW1WElwHxgtE7Kg-1-22">Alessandro Vecchi/Shutterstock</a></span>
</figcaption>
</figure>
<p>Our new data-driven best estimate is a death toll of 56m by the beginning of the 1600s – 90% of the pre-Columbian indigenous population and around 10% of the global population at the time. This makes the “Great Dying” the largest human mortality event in proportion to the global population, putting it second in absolute terms only to World War II, in which <a href="http://necrometrics.com/20c5m.htm#Second">80m people died</a> – 3% of the world’s population at the time.</p>
<p>A figure of 90% mortality in post-contact America is extraordinary and exceeds similar epidemics, including the <a href="http://www.bbc.co.uk/history/british/middle_ages/black_01.shtml">Black Death in Europe</a> – which resulted in a 30% population loss in Europe. One explanation is that multiple waves of epidemics hit indigenous immune systems that had evolved in isolation from Eurasian and African populations for 13,000 years.</p>
<p>Native Americas at that time had never been in contact with the pathogens the colonists brought, creating so-called “<a href="https://www.nlm.nih.gov/nativevoices/timeline/183.html">virgin soil</a>” epidemics. People who didn’t die from smallpox, died from the following wave of influenza. Those who survived that succumbed to measles. Warfare, famine and colonial atrocities did the rest in the Great Dying.</p>
<h2>Global consequences</h2>
<p>This human tragedy meant that there was simply not enough workers left to manage the fields and forests. Without human intervention, previously managed landscapes returned to their natural states, thereby absorbing carbon from the atmosphere. The extent of this regrowth of the natural habitat was so vast that it <a href="https://www.scientificamerican.com/article/mass-deaths-in-americas-start-new-co2-epoch/">removed enough CO₂ to cool the planet</a>.</p>
<p>The lower temperatures prompted feedbacks in the carbon cycle which eliminated even more CO₂ from the atmosphere – such as less CO₂ being released from the soil. This explains the drop in CO₂ at 1610 seen in Antarctic ice cores, solving an enigma of why the whole planet <a href="https://www.eh-resources.org/timeline-middle-ages/">cooled briefly in the 1600s</a>. During this period, severe winters and cold summers caused <a href="https://books.google.ge/books/about/Global_Crisis.html?id=gjdDP15N4FkC&redir_esc=y&hl=en">famines and rebellions from Europe to Japan</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/255759/original/file-20190128-108364-psy089.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/255759/original/file-20190128-108364-psy089.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/255759/original/file-20190128-108364-psy089.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/255759/original/file-20190128-108364-psy089.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/255759/original/file-20190128-108364-psy089.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/255759/original/file-20190128-108364-psy089.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/255759/original/file-20190128-108364-psy089.png?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">Global temperatures dipped around the same time as the Great Dying in the Americas.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/w/index.php?curid=466264">Robert A. Rohde/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The <a href="https://theconversation.com/anthropocene-began-with-species-exchange-between-old-and-new-worlds-38674">modern world</a> began with a catastrophe of near-unimaginable proportions. Yet it is the first time the Americas were linked to the rest of the world, marking the beginning of a new era.</p>
<p>We now know more about the scale of pre-European American populations and the Great Dying that erased so many of them. Human actions at that time caused a drop in atmospheric CO₂ that cooled the planet long before human civilisation was concerned with the idea of climate change. </p>
<p>Such a dramatic event would not contribute much to easing the rate of modern global warming, however. The unprecedented reforestation event in the Americas led to a reduction of 5 parts per million CO₂ from the atmosphere – only about <a href="https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide">three years’ worth of fossil fuel emissions</a> today.</p><img src="https://counter.theconversation.com/content/110549/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexander Koch receives funding from the Natural Environment Research Council Doctoral Training Partnership initiative. </span></em></p><p class="fine-print"><em><span>Chris Brierley receives funding from the Natural Environment Research Council, the Belmont Forum and the national Science Foundation (US) to study climates of the past and future. </span></em></p><p class="fine-print"><em><span>Mark Maslin is a Founding Director of Rezatec Ltd, Director of The London NERC Doctoral Training Partnership and a member of Cheltenham Science Festival Advisory Committee. He is an unpaid member of the Sopra-Steria CSR Board. He has received grant funding in the past from the NERC, EPSRC, ESRC, Royal Society, DIFD, DECC, FCO, Innovate UK, Carbon Trust, UK Space Agency, European Space Agency, Wellcome Trust, Leverhulme Trust and British Council. He has received research funding in the past from The Lancet, Laithwaites, Seventh Generation, Channel 4, JLT Re, WWF, Hermes, CAFOD and Royal Institute of Chartered Surveyors. </span></em></p><p class="fine-print"><em><span>Simon Lewis has received funding from Natural Environment Research Council, the Royal Society, the European Union, the Leverhulme Trust, the Centre for International Forestry, National Parks Agency of Gabon, Microsoft Research, the Gordon and Betty Moore Foundation, the David and Lucile Packard Foundation.</span></em></p>No records of the size of Native American populations before 1492 and the arrival of Europeans survive. A new study has found answers.Alexander Koch, PhD candidate in Physical Geography, UCLChris Brierley, Associate Professor of Geography, UCLMark Maslin, Professor of Earth System Science, UCLSimon Lewis, Professor of Global Change Science at University of Leeds and, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/810702017-09-18T23:13:55Z2017-09-18T23:13:55ZCarbon dioxide trapped by ice-age oceans raises questions for future<figure><img src="https://images.theconversation.com/files/179538/original/file-20170724-21564-1mxegcl.jpg?ixlib=rb-1.1.0&rect=352%2C12%2C1692%2C1220&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sea ice trapped atmospheric carbon dioxide in the last ice age.</span> <span class="attribution"><span class="source">Pearse Buchanan</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Over the past few decades, scientists have monitored the atmosphere and oceans using instruments, gauges and satellites. But modern climate variability remains small compared to what we can expect in the future due to human emission of carbon dioxide.</p>
<p>How can we be sure we understand how climate and carbon dioxide are linked? <a href="https://doi.org/10.1016/j.epsl.2017.05.015">Our research</a> examines the climate of past ice ages, revealing what we know – and still need to learn – about climate and carbon dioxide.</p>
<p>For the past million years or so, Earth’s climate has gone through regular ice age cycles. Ice ages were fundamentally different from warm periods. Global temperatures were about three to five degrees Celsius cooler. Large ice sheets blanketed North America and Eurasia, displacing the expansive forests found there today. Deserts expanded and moved more dust over land and seas. Sea ice covered the ocean around the poles, and ocean currents changed. </p>
<p>Ancient air bubbles trapped in the ice from Antarctica have also provided a glimpse of how the ice age atmosphere was different. <a href="http://earthguide.ucsd.edu/virtualmuseum/climatechange2/07_1.shtml">Carbon dioxide levels</a> were about one-third lower during ice ages compared to warm periods, and less than half of what our atmosphere holds today due to carbon emissions. </p>
<h2>Ocean key to low carbon dioxide</h2>
<p>Ever since scientists first discovered <a href="http://earthguide.ucsd.edu/virtualmuseum/climatechange2/07_2.shtml">carbon dioxide levels were low during ice ages</a>, they have been proposing theories to understand why. It’s widely accepted that the ocean lies at the centre of the carbon dioxide puzzle because the ocean holds about 60 times more carbon than the atmosphere. Many studies have focused on how carbon dioxide escaped from the ocean when the last ice age ended. But how did the carbon dioxide get there when the Earth cooled? </p>
<p>As climate scientists, we have long shared a fascination with the ice age carbon dioxide puzzle, and so decided to examine the fate of the ocean as the Earth moved into the last ice age, and how the ocean pulled carbon dioxide out of the atmosphere and into the deep sea. </p>
<p>The last warm period ended around 125,000 years ago, when our human ancestors were still in Africa. The planet cooled for more than 100,000 years until it reached the coldest part of the last ice age, 20,000 years ago. While the planet was cooling, carbon dioxide levels also dropped over three key periods between 125,000 and 20,000 years ago. With our research study, we hoped to understand how the ocean’s cooling behaviour was linked to drops in carbon dioxide.</p>
<h2>Fossils yield clues</h2>
<p>Direct measurements only give us information about ocean temperatures for about the last 100 years, so we turned to chemical and biological clues left by tiny fossils from the sea floor. </p>
<p>Animals called foraminifera live at the ocean surface and form shells the size of sand grains. When they die, their shells fall to the sea floor and leave behind an important record of the temperatures in which they lived. By counting the numbers of cold versus warm species, scientists can estimate past ocean temperatures. </p>
<p>We trawled the scientific literature for studies of past sea surface temperatures. In total, we found data from 136 locations around the globe, amounting to more than 40,000 estimates of temperature. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/186448/original/file-20170918-8255-1qxd96a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/186448/original/file-20170918-8255-1qxd96a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/186448/original/file-20170918-8255-1qxd96a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/186448/original/file-20170918-8255-1qxd96a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/186448/original/file-20170918-8255-1qxd96a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/186448/original/file-20170918-8255-1qxd96a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=483&fit=crop&dpr=1 754w, https://images.theconversation.com/files/186448/original/file-20170918-8255-1qxd96a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=483&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/186448/original/file-20170918-8255-1qxd96a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=483&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Foraminifera are tiny animals that live at the ocean surface.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Foraminifera_(265_36)_Various.jpg">Josef Reischig</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Our findings show that carbon took different paths into the deep sea during each step. The first drop in carbon dioxide occurred 115,000 to 100,000 years ago. During this time, both polar oceans cooled significantly and sea ice expanded dramatically around Antarctica. But we found no evidence that the large-scale circulation of the deep-sea changed during this time.</p>
<p>This is significant, because many theories explaining the carbon dioxide puzzle involve changes in deep ocean circulation. So the most likely cause for the first major drop in carbon dioxide levels was an expansion of sea ice around Antarctica. Sea ice acts as a lid on the waters of the Southern Ocean, also known as the Antarctic Ocean, and prevents them from releasing their carbon to the atmosphere.</p>
<p>The second drop in carbon dioxide levels happened around 70,000 years ago. Ocean temperatures cooled even further, this time accompanied by changes in deep ocean circulation. There is also evidence of an uptick in the ocean’s biological production at this time. Fuelled by nutrients added to the ocean from desert dust, tiny ocean plants helped to pump carbon from the surface ocean into the deep sea.</p>
<h2>How did carbon dioxide enter the oceans?</h2>
<p>We conclude that a reorganization of deep ocean circulation, triggered by ocean cooling and even more sea ice in the Southern Ocean, was responsible for trapping most of the carbon dioxide in the ocean during this time. </p>
<p>The final slide into the last ice age saw the last additional uptake of carbon dioxide by the ocean. During this time, it was “all systems go” to trap carbon in the ocean, including strong cooling of the ocean surface (which allows seawater to hold more carbon dioxide), sea ice acting as a lid, an amped-up biological cycle and sluggish deep ocean circulation acting to retain carbon. </p>
<p>We combined the individual efforts of hundreds of scientists to show, for the first time, how global ocean temperatures were linked with carbon dioxide changes as the Earth entered the last ice age. This new understanding hints at some important thresholds in the climate system. </p>
<p>It’s clear that some parts of the system - such as sea ice around Antarctica - respond rapidly when the ocean cools. Other parts, like deep ocean circulation, change very little at first, until a nudge from extra cooling pushes the system into a new state.</p>
<p>But far from solving the carbon dioxide puzzle, this work raises new questions. For example, we still don’t have a good handle on how much sea ice was changing when the ice age began. </p>
<p>It also points to gaps in existing theories. Our work shows the deep ocean circulation changed dramatically around 70,000 years ago, but we still need to understand how. Our next step is to combine our new temperature database with ice age models to put some of these theories to the test.</p><img src="https://counter.theconversation.com/content/81070/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karen Kohfeld receives funding from Canadian National Science and Engineering Research Council Discovery Grants program; NSERC Canada Research Chair Program. </span></em></p><p class="fine-print"><em><span>Zanna Chase receives funding from the Australian Research Council, Future Fellowship Programme</span></em></p>The last ice age locked atmospheric carbon dioxide into oceans, which has major implications for how the oceans and carbon dioxide may be linked in the future.Karen Kohfeld, Professor, Climate, Oceans, and Paleo-Environments, Simon Fraser UniversityZanna Chase, Associate professor, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/649842016-09-12T15:13:36Z2016-09-12T15:13:36ZWhy a volcano, Frankenstein, and the summer of 1816 are relevant to the Anthropocene<figure><img src="https://images.theconversation.com/files/137363/original/image-20160912-3793-1gc5v36.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">Creative Travel Projects / Shutterstock.com</span></span></figcaption></figure><p>The idea that we are now living in the <a href="https://theconversation.com/uk/topics/anthropocene-2770">Anthropocene</a> – a new geological epoch characterised by humanity’s influence on the planet – has gained wide currency in recent years. And now a group of experts tasked by the International Commission on Stratigraphy to assess whether human activities are leaving a strong trace in the rock record have advised that the Holocene – the epoch that has defined the last 10,000 years – should indeed be declared over.</p>
<p>To say that we are living in the Anthropocene does not mean that our impacts now define the earth system, or that we have control over it. Rather, it means that our activities play an increasingly important role within a complex set of interactions with a wide range of other forces, objects, and agencies.</p>
<p>For <a href="https://books.google.co.uk/books/about/Ecocriticism_on_the_Edge.html?id=IvOmCQAAQBAJ&redir_esc=y/">some commentators</a>, the Anthropocene marks a breach from the past that requires new ways of thinking. And yet, for at least two centuries, nature writers have been addressing the complexity of humanity’s entanglements with the natural world.</p>
<p>One plausible start date for the Anthropocene is during the Romantic period (1780-1830), which saw the beginning of the world’s industrialisation and of the increasing atmospheric concentration of greenhouse gases that contribute to global warming. Coincidentally or not, the same period also saw a remarkable flowering of literature concerned with the relationship between human beings and nature.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/137365/original/image-20160912-3768-d3pg96.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/137365/original/image-20160912-3768-d3pg96.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=392&fit=crop&dpr=1 600w, https://images.theconversation.com/files/137365/original/image-20160912-3768-d3pg96.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=392&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/137365/original/image-20160912-3768-d3pg96.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=392&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/137365/original/image-20160912-3768-d3pg96.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=492&fit=crop&dpr=1 754w, https://images.theconversation.com/files/137365/original/image-20160912-3768-d3pg96.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=492&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/137365/original/image-20160912-3768-d3pg96.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=492&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Smoking towers soon became a common sight in the British landscape.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:StRolloxChemical_1831.jpg#/media/File:StRolloxChemical_1831.jpg">Wikimedia Commons</a></span>
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</figure>
<p>Authors such as Gilbert White, William and Dorothy Wordsworth, Charlotte Smith, and John Clare wrote about their local flora, fauna, and natural phenomena with unprecedented depth and richness, thereby inventing the modern genre of nature writing.</p>
<p>Their works also bear the imprint of global environmental forces. The final pages of White’s <a href="http://www.gutenberg.org/ebooks/1408">The Natural History of Selborne</a> (1789), for example, describe “the horrible phaenomena” of the summer of 1783, including a “peculiar haze, or smokey fog” that appeared across Europe and created a “superstitious kind of dread”. And the poet William Cowper wrote of the same summer that: </p>
<blockquote>
<p>the props<br>
And pillars of our planet seem to fail,<br>
And nature with a dim and sickly eye<br>
To wait the close of all. </p>
</blockquote>
<p>The principal cause of the unusual conditions of 1783 was the eruption of the Laki volcano in Iceland. A generation later, the much larger eruption of the Indonesian volcano Mount Tambora in 1815 was to have a defining impact: both on the climate, and on Romantic literature.</p>
<h2>The year without a summer</h2>
<p>The following year, 1816, was exceptionally cold and wet and came to be known as the “year without a summer”. What Samuel Taylor Coleridge called “this end of the World Weather” led to incidences of famine, political unrest, and disease across the globe.</p>
<p>The summer of 1816 is also known as one of the most productive periods in the history of English literature. This is not least because it saw the conception of Mary Shelley’s <a href="http://www.gutenberg.org/ebooks/84">Frankenstein</a>, as well as major works by her husband Percy Bysshe Shelley and their friend Lord Byron. All were composed during the time that the three spent together near Geneva.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/137367/original/image-20160912-3807-1c72ea4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/137367/original/image-20160912-3807-1c72ea4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/137367/original/image-20160912-3807-1c72ea4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=785&fit=crop&dpr=1 600w, https://images.theconversation.com/files/137367/original/image-20160912-3807-1c72ea4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=785&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/137367/original/image-20160912-3807-1c72ea4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=785&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/137367/original/image-20160912-3807-1c72ea4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=986&fit=crop&dpr=1 754w, https://images.theconversation.com/files/137367/original/image-20160912-3807-1c72ea4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=986&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/137367/original/image-20160912-3807-1c72ea4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=986&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lord Byron.</span>
</figcaption>
</figure>
<p>A mixture of terrible weather, the sublime Alpine landscapes that they visited, and their interest in science led them to think hard about the vulnerability of human communities living with uncontrollable natural forces. They even considered the possibility of human extinction.</p>
<p>A key concern for Byron and the Shelleys was global cooling. Responding to contemporary geological theories (and no doubt the unnaturally cold temperature), Percy Shelley argued that the glaciers around Mont Blanc were continually “augmenting”. In a letter to his friend Thomas Love Peacock, he raised the possibility that “this globe which we inhabit will at some future period be changed into a mass of frost by the encroachments of the polar ice”. And his poem “<a href="https://www.poetryfoundation.org/poems-and-poets/poems/detail/45130">Mont Blanc</a>” describes glaciers that “creep | Like snakes that watch their prey”; a “flood of ruin” that threatens human existence.</p>
<p>Byron goes further in his poem “<a href="https://www.poetryfoundation.org/poems-and-poets/poems/detail/43825">Darkness</a>”, imagining the dimming of the entire universe: “The icy earth | Swung blind and blackening in the moonless air.” In a chillingly apocalyptic vision, the growing cold and darkness leads to resource wars, ecosystem collapse, famine, and eventually the destruction of all life on Earth, leaving it “a lump of death”.</p>
<p>The extinction of the human species is also addressed in Frankenstein and here again it is linked to global cooling. Victor eventually destroys his work on the Creature’s companion due to his fear that the two might procreate and supplant humanity. Significantly, the Creature is much better adapted to cold conditions than his creator. Frankenstein raises the spectre of a post-human future in which a stronger species develops that is able to flourish on an icy globe.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/137369/original/image-20160912-3777-fik88t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/137369/original/image-20160912-3777-fik88t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=753&fit=crop&dpr=1 600w, https://images.theconversation.com/files/137369/original/image-20160912-3777-fik88t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=753&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/137369/original/image-20160912-3777-fik88t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=753&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/137369/original/image-20160912-3777-fik88t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=947&fit=crop&dpr=1 754w, https://images.theconversation.com/files/137369/original/image-20160912-3777-fik88t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=947&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/137369/original/image-20160912-3777-fik88t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=947&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Boris Karloff as Frankenstein’s monster.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Frankenstein%27s_monster_(Boris_Karloff).jpg#/media/File:Frankenstein%27s_monster_(Boris_Karloff).jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>Cold futures</h2>
<p>The anxieties of Romantic writers might seem rather different to ours. Despite their interest in climate – including the possibility that human activity could “improve” it – they were not concerned by the possibility of a human-made global climate crisis. But given that <a href="https://theconversation.com/blocking-out-the-sun-wont-fix-climate-change-but-it-could-buy-us-time-50818">some scientists are proposing</a> to counteract the effects of climate change by mimicking the effects of a large volcanic eruption, their writing seems particularly pertinent to the Anthropocene.</p>
<p>Their works do not offer simplistic solutions. Frankenstein is not a warning against technological experimentation. Nor is it an endorsement of the idea that we should “<a href="http://thebreakthrough.org/index.php/journal/past-issues/issue-2/love-your-monsters">love our monsters</a>” and therefore embrace <a href="https://theconversation.com/uk/topics/geoengineering-1515">geoengineering</a>.</p>
<p>The most interesting Romantic literature is not so much concerned with what we “do” to nature or vice versa, but with the entanglement of human and nonhuman agents. Thus the protagonist of Byron’s drama <a href="http://www.bartleby.com/18/6/11.html">Manfred</a> refuses to bow down to the personified elemental forces that surround him and yet relies on their power. And “Mont Blanc” raises the possibility that reality is defined by the human imagination at the same time as presenting our vulnerability to environmental change. </p>
<p>A key legacy of Romanticism has been a form of nature writing that depicts the solitary individual’s transcendent experience of the sublime landscape. Perhaps unfairly, such writing has sometimes been criticised for its self-absorption and blindness to larger contexts.</p>
<p>But a richer understanding of Romantic literature might inform a nature writing fit for our current situation: messy, urgent, aware that “nature” does not exist separately from politics and economics, and reflective of the complex human-nonhuman assemblages that characterise the Anthropocene.</p><img src="https://counter.theconversation.com/content/64984/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Higgins receives funding from the Arts and Humanities Research Council for the research on which this article is based. </span></em></p>A volcanic eruption in 1815 triggered a year without a summer – prompting a flowering of nature writing that is all too relevant today.David Higgins, Associate Professor in English Literature, University of LeedsLicensed as Creative Commons – attribution, no derivatives.