'Hothouse Earth' Co-Author Says 'People Will Look Back on 2018 as the Year When Climate Reality Hit'
20 August 2018
Climate
Flames of the Simi Valley fire ravage a Southern California mountain side on Oct. 29, 2012. U.S. Air Force / Senior Master Sgt. Dennis W. Goff
By Jessica Corbett
Amid a flurry of "breathless headlines" about warnings in a new study that outlines a possible "Hothouse Earth" scenario, one co-author optimistically expressed his belief that "people will look back on 2018 as the year when climate reality hit."
<p>In an interview with the Guardian on this past Friday, Stockholm Resilience Center executive director Johan Rockström declared, "This is the moment when people start to realize that global warming is not a problem for future generations, but for us now." Rockström's study has received an "unprecedented" amount of global attention in the past week—270,000 downloads and counting.</p>
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<p>"Published in the <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.1810141115" target="_blank">Proceedings of the National Academy of Sciences</a>, the new study, while not conclusive in its findings, warns that <a href="https://www.economist.com/leaders/2018/08/02/the-world-is-losing-the-war-against-climate-change" target="_blank">humanity may be just 1°C away from creating</a> a series of dynamic feedback loops that could push the world into a climate scenario not seen since the dawn of the Helocene Period, nearly 12,000 years ago," Common Dreams <a href="https://www.commondreams.org/news/2018/08/07/hothouse-future-humanity-scientists-behind-terrifying-climate-analysis-hope-they-are" target="_blank">reported</a> last week.<br></p><p>This domino effect of feedbacks loops, the report explains, would pose "severe risks for health, economies, political stability, and ultimately, the habitability of the planet for humans." Though such warnings are chilling, the report authors and climate experts pointed out a major takeaway from the study that much reporting on it failed to highlight: that there is still time for humanity to act.</p><p>"Yes, the prospect of runaway climate change is terrifying. But this dead world is not our destiny. It's entirely avoidable," meteorologist Eric Holthaus <a href="https://www.commondreams.org/views/2018/08/14/terrified-hothouse-earth-dont-despair-do-something" style="" target="_blank">wrote</a> for Grist this week. "As the authors of the paper have argued in response to the coverage, implying otherwise is the same as giving up just as the fight gets tough."</p><p>Investigative journalist Antonia Juhasz, known for her deep dives on the oil industry, spoke with another co-author of the report, University of Arizona professor Diana Liverman, about actions the international community can take right now to address the climate crisis.</p>
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<p>"Collective human action is required to steer the Earth System away from a potential threshold and stabilize it in a habitable interglacial-like state," the report's abstract declares. "Such action entails stewardship of the entire Earth System—biosphere, climate, and societies—and could include decarbonization of the global economy, enhancement of biosphere carbon sinks, behavioral changes, technological innovations, new governance arrangements, and transformed social values."<br></p><p>Rockström told the Guardian that he is concerned about the growing gap between scientists warnings' and most politicians' docile statements and actions, noting that "politicians prefer small problems that they can solve and get credit for. They don't like big problems that, even if they succeed, leave the rewards for their successors."</p><p>However, Rockström added, "once you pile up public pressure, politicians find it hard to avoid taking responsibility." As the <em>Guardian </em>acknowledged, "even in the U.S., which President Donald Trump has vowed to pull out of the Paris accord, public opinion surveys <a href="http://closup.umich.edu/files/ieep-nsee-2018-spring-climate-belief.pdf" target="_blank">have shown a growing acceptance of climate science</a>," likely helped along by recent <a href="https://www.commondreams.org/tag/extreme-weather" target="_blank">extreme weather</a> across the globe, which experts have linked to the climate crisis.</p><p>Gallup <a href="https://news.gallup.com/poll/231530/global-warming-concern-steady-despite-partisan-shifts.aspx?g_source=link_newsv9&g_campaign=item_231386&g_medium=copy" target="_blank">polling</a> found earlier this year that although there's a notable partisan divide—only 35 percent of Republicans believe human activity is causing the crisis, compared with 89 percent of Democrats and 62 percent of Independents—"majorities of Americans overall say most scientists think global warming is occurring (66 percent), it is caused by human activities (64 percent), and its effects have begun (60 percent)."</p><p> <em>Reposted with permission from our media associate <a href="https://www.commondreams.org/news/2018/08/17/hothouse-earth-co-author-says-people-will-look-back-2018-year-when-climate-reality" target="_blank">Common Dreams</a>.</em><em></em></p>
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MARK GARLICK / SCIENCE PHOTO LIBRARY / Getty Images
By Richard Betts
A new scientific paper proposing a scenario of unstoppable climate change has gone viral, thanks to its evocative description of a "Hothouse Earth."
<p>
Much of the media coverage suggests that we face an imminent and unavoidable extreme climate catastrophe. But as a climate scientist who has carried out <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/wcc.130" target="_blank">similar research</a> myself, I am aware that this latest work is a lot more nuanced than the headlines imply. So what does the hothouse paper actually say, and how did the authors draw their conclusions?
</p><p>
First, it's important to note that the paper is a "perspective" piece—an essay based on knowledge of the scientific literature, rather than new modeling or data analysis. Leading Earth System scientist <a href="http://climate.anu.edu.au/about-us/people/will-steffen" target="_blank">Will Steffen</a> and his 15 co-authors draw on a diverse set of literature to paint a picture of how a chain of self-reinforcing changes might potentially be initiated, eventually leading to very large climate warming and sea level rise.
</p><p>
One example would be the thawing of Arctic permafrost, which releases methane into the atmosphere. As methane is a greenhouse gas, this means the Earth retains more heat, causing more permafrost to thaw, and so on. Other possible self-reinforcing processes include the large-scale die-back of forests, the melting of sea ice, or the loss of ice sheets on land.
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<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODI5NTA5OS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY1MDY4NzEyMH0.dyf-PP1pyBTTPIGTIyartuTarhhuoBYbYz6w2cletcM/img.png?width=980" id="15ae1" class="rm-shortcode" data-rm-shortcode-id="1ef0cf358ee6a17886ab75f885073510" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Global map of potential tipping cascades, with arrows showing potential interactions. </small><small class="image-media media-photo-credit" placeholder="add photo credit..."><a href="http://www.pnas.org/content/pnas/early/2018/07/31/1810141115.full.pdf" target="_blank">Steffen et al / PNAS</a></small>
</p><h2>Hothouse or Stabilized?</h2><p>
Steffen and colleagues introduce the term "Hothouse Earth" to emphasize that these extreme conditions would be outside those that have occurred over the <a href="https://theconversation.com/the-last-time-earth-was-this-hot-hippos-lived-in-britain-thats-130-000-years-ago-53398" target="_blank">past few hundred thousand years</a>, which have been cycles of ice ages with milder periods in between. They also present an alternative scenario of a "Stabilized Earth" where these changes are not triggered, and the climate remains similar to now.
</p><p>
The authors make the case that there is a level of global warming which is a critical threshold between these two scenarios. Beyond this point, the Earth System might conceivably become set on a pathway that makes the extreme "hothouse" conditions inevitable in the long term. They argue—or perhaps speculate—that the process of irreversible self-reinforcing changes could in theory start at levels of global warming as low as 2°C above pre-industrial levels, which could be reached around the middle of this century (we are already at around 1°C). They also acknowledge large uncertainty in this estimate, and say that it represents a "risk averse approach".
</p><p>
A key point is that, even if the self-perpetuating changes do begin within a few decades, the process would take a long time to fully kick in—centuries or millennia.
</p><p>
Steffen and colleagues support their suggestion of a threshold at 2°C through reference to previously-published scientific work. These include other <a href="http://www.pnas.org/content/105/6/1786" target="_blank">review papers</a> which themselves <a href="https://www.nature.com/articles/nclimate3013" target="_blank">drew on wider literature</a>, and an <a href="http://www.pnas.org/content/106/13/5041.short" target="_blank">"expert elicitation" study</a> in which scientists were asked to estimate the levels of global warming at which "tipping points" for these key climate processes might be passed (I was one of those consulted).
</p><p>
The authors argue that 2°C can still be avoided if humanity takes concerted action to reduce its warming effect on the climate. In a similar way that the "Hothouse Earth" scenario involves huge changes in the climate system with multiple effects of one process leading to another, the concerted global action to avoid 2°C would, they suggest, also involve huge changes in the human system, again with several fundamental steps leading from one change to another.
</p><h2>Don't Ignore the Caveats</h2><p>
Personally, I found this an interesting and important think piece that was well worth reading. But since this is not actually new research, why is it getting so much coverage? I suspect that one reason is the use of the vivid "Hothouse Earth" term at a time when everyone's talking about <a href="https://theconversation.com/uk/topics/heatwave-4853" target="_blank">heatwaves</a>. Another is that it's clearly a dramatic narrative, and not surprisingly this has led to some sensationalist articles.
</p><p>
With some exceptions, much of the highest-profile coverage of the essay presents the scenario as definite and imminent. The impression is given that 2°C is a definite "point of no return", and that beyond that the "hothouse" scenario will rapidly arrive. Many <a href="https://metro.co.uk/2018/08/07/earth-decades-away-from-tipping-point-which-triggers-runaway-climate-change-apocalypse-7805451/" target="_blank">articles</a> <a href="https://www.theguardian.com/environment/2018/aug/06/domino-effect-of-climate-events-could-push-earth-into-a-hothouse-state" target="_blank">ignore the caveats</a> that the 2°C threshold is extremely uncertain, and that even if it were correct, the extreme conditions would not occur for centuries or millennia.
</p><p>
Some articles do however <a href="https://www.forbes.com/sites/michaelmarshalleurope/2018/08/07/there-is-a-real-risk-that-earths-climate-could-run-out-of-control/amp/?__twitter_impression=true" target="_blank">emphasise the more tentative nature of the work</a>, and some <a href="https://www.theguardian.com/commentisfree/2018/aug/07/climate-change-catastrophe-political-will-grassroots-engagement" target="_blank">push back</a> against this overselling of the doomsday scenario, arguing that provoking fear or despair is counterproductive.
</p><p>
One thing that strikes me about the scientific literature on "tipping points" is that there are a lot of review papers like this that end up citing the same studies and each other – indeed, my colleagues and I wrote one <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/wcc.130" target="_blank">a while ago</a>. There is a great deal of interesting, insightful research going on using theoretical methods and calculations with large approximations. However, we have yet to see an equivalent level of research in the highly-complex <a href="https://onlinelibrary.wiley.com/doi/pdf/10.1002/wcc.148" target="_blank">Earth System Models</a> which generate the kind of detailed climate projections used for addressing policy-relevant questions by the Intergovernmental Panel on Climate Change (IPCC).
</p><p>
Steffen and colleagues have made a good start at addressing such questions, going as far as they can on the basis of the existing literature, but their essay should motivate new research to help narrow down the huge uncertainties. This will help us see better whether "Hothouse Earth" is our destiny, or mere speculation. In the meantime, awareness of the risks—however tentative—can still help us decide how to manage our impact on the global climate.
</p><p>
<em>Reposted with permission from our media associate </em><em><a href="https://theconversation.com/hothouse-earth-heres-what-the-science-actually-does-and-doesnt-say-101341" target="_blank">The Conversation</a></em><em>.</em>
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In two recent studies, scientists have looked into the future and into the past to see what might happen to the global climate if we fail to curb greenhouse gas emissions in time. The results are frightening.
<p>A <a href="https://liverman.faculty.arizona.edu/sites/liverman.faculty.arizona.edu/files/2018-08/Steffen%20et%20al%202018%20Trajectories%20of%20the%20Earth%20System%20in%20the%20Anthropocene_0.pdf" target="_blank">study</a> published Monday in Proceedings of the National Academy of Sciences examined how, once a certain threshold was crossed, feedback loops could push the planet's climate towards a "Hothouse Earth." </p><p>The researchers expressed uncertainty as to whether limiting warming to the <a href="http://www.ecowatch.com/tag/paris-agreement" target="_self">Paris agreement</a>'s upper limit of 2 degrees Celsius above pre-industrial levels would be enough to halt the impacts of <a href="http://www.ecowatch.com/tag/climate-change" target="_self">climate change</a>, or if feedback loops already in motion would accelerate the process regardless. </p><p>"We note that the Earth has never in its history had a quasi-stable state that is around 2C warmer than the preindustrial and suggest that there is substantial risk that the system, itself, will 'want' to continue warming because of all of these other processes—even if we stop emissions," study author Katherine Richardson from the University of Copenhagen told <a href="https://www.theguardian.com/environment/2018/aug/06/domino-effect-of-climate-events-could-push-earth-into-a-hothouse-state" target="_blank">The Guardian</a>. </p><p>Some of those other processes include the release of <a href="http://www.ecowatch.com/tag/methane" target="_self">methane</a> from the thawing of the permafrost and the dieback of carbon sinks like the Amazon Rainforest.</p><p>When it comes to <a href="http://www.ecowatch.com/tag/sea-level-rise" target="_self">sea level rise</a>, the scientists outlined how the melting of <a href="http://www.ecowatch.com/tag/greenland" target="_self">Greenland</a>'s ice could disrupt the Gulf Stream current, lifting sea levels and warming the Southern Ocean, which would in turn melt more ice in <a href="http://www.ecowatch.com/tag/antarctica" target="_self">Antarctica</a>. </p><p>A "Hothouse Earth" would be four degrees warmer than pre-industrial levels, and the path towards reaching it would most likely flood deltas, increase the intensity of coastal storms, and kill off <a href="http://www.ecowatch.com/tag/coral-reefs" target="_self">coral reefs</a> by the end of this century or sooner. </p><p>Currently, the Earth is around one degree Celsius warmer than pre-industrial levels, and that is already leading to more extreme impacts than would have been predicted, study author and executive director of the Stockholm Resilience Centre Johan Rockström told The Guardian. </p><p>"The heatwave we now have in Europe is not something that was expected with just 1C of warming," Rockström said. "Several positive feedback loops are already in operation, but they are still weak. We need studies to show when they might cause a runaway effect."</p><p>The paper concluded that to safely avoid a hothouse scenario, humans would have to change their relationship to the Earth. </p><p>"Collective human action is required to steer the Earth System away from a potential threshold and stabilize it in a habitable interglacial-like state. Such action entails stewardship of the entire Earth System—biosphere, climate and societies—and could include decarbonization of the global economy, enhancement of biosphere carbon sinks, behavioral changes, technological innovations, new governance arrangements, and transformed social values," the paper said. </p><p>Another paper published July 30 in <a href="https://www.nature.com/articles/s41561-018-0199-0" target="_blank">Nature Geoscience</a> looked millions of years into the past to see how hot an Earth with a carbon-dioxide-heavy atmosphere would really be.</p><p>The study used peat fossils to assess mid-level temperatures in the early Paleogene, 56 to 48 million years ago.</p><p>This was the period after the extinction of the dinosaurs that saw the rise of mammals, as well as atmospheric carbon dioxide levels of 1,000 parts per million, which is what they are predicted to reach by the end of this century if no action is taken, <a href="https://www.theatlantic.com/science/archive/2018/08/earths-scorching-hot-history/566762/" target="_blank">The Atlantic reported</a>.</p><p>The study found that during that time, average temperatures in what are now the UK, Germany and New Zealand averaged 23 to 39 degrees Celsius, 10 to 15 degrees warmer than now. </p><p>"Europe would look like the Everglades and a heat wave like we're currently experiencing in Europe would be completely normal. That is, it would be the everyday climate," study author and University of Bristol geochemist David Naafs told The Atlantic. </p><p>Naafs and his colleagues tried to assess temperatures in the tropics as well, but the ancient lignite samples from India they found turned up temperatures too hot for their method to accurately measure.</p><p>"Some climate models suggest that the tropics just became a dead zone with temperatures over 50 degrees Celsius like in Africa and South America," Naafs told The Atlantic. "But we have no data so we don't know."</p>
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