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Saturday, October 6, 2018

Graham Readfearn: Earth's climate monsters could be unleashed as temperatures rise

As a UN panel prepares a report on 1.5 C global warming, researchers warn of the risks of ignoring ‘feedback’ effects

Amazon forest

 Fundamental questions are being raised about the ability of governments to stop the Earth from spiraling into a ‘hothouse’. Photograph: Peter van der Sleen/University o/PA

by Graham Readfearn, The Guardian, October 6, 2018

This week, hundreds of scientists and government officials from more than 190 countries have been buzzing around a convention centre in the South Korean city of Incheon.

They are trying to agree on the first official release of a report – the bit called the Summary for Policymakers – that pulls together all of what’s known about how the world might be affected once global warming gets to 1.5 C.
What will happen to coral reefs? How will extreme weather events and droughts change? What about heatwaves? And then, what are the different “pathways” that economies could choose to keep temperatures to 1.5 C?
On Monday morning, the summary document is expected to be released, and there will be a cascade of headlines around the world.
The report, being pulled together by the United Nations Intergovernmental Panel on Climate Change, was one tiny part of the Paris climate change agreement.
As things stand, if you add up all the things that the 190-plus countries have committed to do as part of that Paris deal, global temperatures will probably go well above 3 C.
We’re already at 1 C of warming, so the extra half a degree isn’t far away – many scientists will say it’s already locked in, while others say there are plausible ways to stabilize temperatures at that level.
But in August, one of the world’s leading scientific journals – the Proceedings of the National Academy of Sciences – published a “perspective” article that has become known as the “hothouse earth” paper.
There was no new science in the paper and while it was speculative, it did raise fundamental questions about the ability of governments around the world to stop the Earth from spiraling into a “hothouse.”
One of the report’s authors, Professor Will Steffen, of Australian National University and the Stockholm Resilience Centre, talked me through it.
The problem lies with “feedbacks” – in the “supplementary information” attached to the paper, Steffen and colleagues actually listed 10 of them. With each, they include estimates of how much extra CO2 and temperature they could add once you hit about 2 C of global warming.
For example, the ability of the land and ocean to keep soaking up CO2 could weaken, giving you an extra 0.25 C of warming. Dieback of trees in the Amazon and subarctic could give us another 0.1 C.
Permafrost, which is already starting to defy its name by not being all that permanent, could release ever more methane and carbon that might add a bit more warming again (0.09 C is the estimate there).
The point is that once you add them all up, you get close to 0.5 C of warming by the end of the century. Given we’re already at 1 C of global warming, that makes the job of keeping warming “well below 2 C” or even holding it at 1.5 C much, much harder than it already is.
And there’s the rub.
While governments have the means to affect how much CO2 gets released through policies that radically cut the use of fossil fuels, it would be much harder to get a grip on thawing permafrost, mass forest collapses, or the loss of polar sea ice.
By failing to get a grip on a thing that’s feasibly under your control, we end up risking the release a whole gang of other monsters that we can’t.
This gets us to another big issue, says Steffen, because climate models don’t include some of these feedbacks. In essence, the warmer things get, the less reliable the models become. He tells me:
“I think the dominant linear, deterministic framework for assessing climate change is flawed, especially at higher levels of temperature rise.
So, yes, model projections using models that don’t include these processes indeed become less useful at higher temperature levels. Or, as my co-author John Schellnhuber says, we are making a big mistake when we think we can “park” the Earth System at any given temperature rise – say 2 C – and expect it to stay there.”
For those who understand the idea of a carbon budget – where scientists have calculated him much CO2 you could emit before hitting certain temperature rises – it looks even meaner than before if Steffen and his colleagues are right.
But as they also point out, several of these feedbacks might have “tipping points” that then set off a cascade of other issues. Steffen says:
“Even at the current level of warming of about 1 C above pre-industrial, we may have already crossed a tipping point for one of the feedback processes (Arctic summer sea ice), and we see instabilities in others – permafrost melting, Amazon forest dieback, boreal forest dieback and weakening of land and ocean physiological carbon sinks.
And we emphasize that these processes are not linear and often have built-in feedback processes that generate tipping point behavior. For example, for melting permafrost, the chemical process that decomposes the peat generates heat itself, which leads to further melting and so on.”
For the record, Steffen thinks the assumptions in climate models that cuts in fossil fuel emissions will deliver relative cuts in temperatures “is OK for perhaps lower temperature rises of 1.5 or 2 C,” but beyond that, he’s sceptical.

The paper has received a bit of pushback from scientists, largely, it appears, because of the sensational headlines it attracted.

For example, Professor Richard Betts, of the UK’s MetOffice, has a measured perspective that’s well worth a look.

Dr Glen Peters, an Australian scientist and climate modeller based at the Centre for International Climate Research in Norway, also thought some of the media coverage went too far with the doomsday vibe.

But he told me that, while it was true that many of the feedbacks in the paper were not well covered by climate models, this was partly because they were not that well understood. I’ll leave you with his thoughts:
“The hothouse earth paper conjectures that many of these feedbacks may interact like a domino effect, lead the Earth system to spiral out of control to reach a new steady state very different from today, and these processes may even start if we are successful at meeting the goals of the Paris Agreement.
“There is also an important timescale question, are we talking decades or millennia, and that is very important for how society may respond. While all the claims made in the hothouse earth paper are justified, we simply don’t have the data to verify if those claims are true. While the paper put in plenty of language to indicate its exploratory nature … many headlines and statements went too far, indicating we had already gone too far and there was no turning back.”
https://www.theguardian.com/environment/planet-oz/2018/oct/06/earths-climate-monsters-could-be-unleashed-as-temperatures-rise

Tuesday, October 2, 2018

An ice-free corridor sustained Arctic marine life during the last ice age, according to scientist from Norway and the UK

AN ICE FREE CORRIDOR SUSTAINED ARCTIC MARINE LIFE DURING THE LAST ICE AGE

Sea ice marginal zone in front of West Antarctic ice sheet. Polynias, ice free corridors between the sea ice and land based ice sheets, are common in Antarctica today. Photo: M. Forwick


During the last ice age, there was an ice free corridor wedged between two large ice masses in the Arctic. This corridor, which spanned several hundred kilometers, provided habitats for highly adaptable marine life-forms.


In a new study, scientists from Norway and the UK have shown that, 20,000 years ago, Arctic sea ice in the winter covered more than twice the area than it does today. Yet, there was a small ice-free oasis between ice covered continents and the frozen ocean. There, marine life prevailed.
“When we were looking for evidence of biological life in sediments at the bottom of the ocean, we found that between the sea ice covered oceans, and the ice sheets on land, there must have been a narrow ice-free corridor that extended over hundreds of kilometres into the Arctic. Such ice-free regions are often called “polynyas” – a Russian expression for an area of open water that is surrounded by sea ice and/or ice sheets,” says research scientist Jochen Knies from CAGE and the Geological Survey of Norway. 
The new findings, which were published recently in Nature Communications, also reveal that the polynya was sustained for at least 5,000 years, when the surroundings were largely covered by ice, and global ocean circulation was at a minimum.
Arctic oasis in front of the Eurasian ice sheet during the last Ice Age, 20.000 years ago (from Knies et al., 2018, Nature Communications).

Common today in Antarctica and Greenland

Today, polynyas are common around Antarctica and Greenland. They form through a combination of offshore winds blowing from nearby ice sheets and warm water rising from the deep ocean. In areas of extreme cold and little access to food, polynyas provide an oasis for marine mammals to survive and they are also critical for global ocean circulation.
“Polynyas in the polar regions are common nowadays, but it’s difficult to confirm their existence in the past. However, by finding chemical fossils of algae that live in the open ocean and in sea ice, we have shown that polynyas must have existed during the last Ice Age,” says co-author Simon Belt, professor of chemistry at Plymouth University. 
During a subsequent period of abrupt climate change around 17,500 years ago, cold freshwater from the melting ice caps caused entire northern oceans to be covered by thick sea ice, and the polynya disappeared. This resulted in a dramatic decline in marine life.  It took up to 2,000 years for life to recover.
The research is of international importance since it shows the vulnerability of marine ecosystems in the northern oceans to periods of rapid climate change, as well as their adaptability to various extreme climate states.
Reference 
Knies, J., Köseoğlu, D., Rise, L., Baeten, N., Bellec, V.K., Bøe, R., Klug, M., Panieri, G., Jernas, P.T., Belt, S.T. (2018). Nordic Seas polynyas and their role in preconditioning marine productivity during the Last Glacial Maximum, Nature Communications, doi: 10.1038/s41467-018-06252-8.

Thursday, July 19, 2018

Rising sea levels will soon destroy underground US internet cables, scientists warn

'The expectation was that we'd have 50 years to plan for it. We don't have 50 years'

Coastal cities like Miami have already experienced serious flooding thanks to recent hurricanes, and researchers warn that inundation with water could endanger the region's internet infrastructure


Coastal cities like Miami have already experienced serious flooding thanks to recent hurricanes, and researchers warn that inundation with water could endanger the region's internet infrastructure

Coastal cities like Miami have already experienced serious flooding thanks to recent hurricanes, and researchers warn that inundation with water could endanger the region's internet infrastructure ( Joe Raedle/Getty Images )

by Josh Gabbatiss, Science Correspondent, The Independent, July 17, 2018

Underground internet cables criss-crossing coastal regions will be inundated by rising seas within the next 15 years, according to a new study.
Thousands of miles of fibre optic cables are under threat in US cities like New York, Seattle and Miami, and could soon be out of action unless steps are taken to protect them.
The report, presented at a meeting of internet network researchers in Montreal, is among the first to reveal the damage a changing climate will cause for the network of cables and data centres that underpins so much of modern life.
What shocked computer scientist Professor Paul Barford and his colleagues most when they investigated the effect of rising tides on US cities was the speed at which the internet will be compromised.
"Most of the damage that's going to be done in the next 100 years will be done sooner than later," said Professor Barford, a researcher at the University of Wisconsin-Madison.
"That surprised us. The expectation was that we'd have 50 years to plan for it. We don't have 50 years."
Most of this infrastructure was constructed around 25 years ago along trails running parallel with highways and coastlines, with no thought given to how geography would alter as the climate changed.
In their study, presented at the Applied Networking Research Workshop, the scientists combined a comprehensive map of the internet’s physical structure with projections of sea level rise produced by the US National Oceanic and Atmospheric Administration (NOAA).
The most at-risk stretches of cable were unsurprisingly those already close to sea level, meaning the slight increases predicted for the next few years will be enough to cover them.
The researchers estimated that in total more than 4,000 miles of buried fibre optic cable in the US will be submerged by 2033.
Massive underwater internet cables link North America with the rest of the world, and the landing points where these cables end will be submerged “in a short period of time”, according to Professor Barford.
While the large transoceanic cables are completely waterproof, the buried smaller fibre optic cables are not and if they are submerged there could be far-reaching impacts not only in the coastal US but potentially around the world.
Flooding in coastal cities has been acknowledged as a major threat, and many areas have already begun building hardy sea walls to prepare for the worst. Professor Barford said such preparations will go some way to protecting the internet, but will probably not be enough.
"The first instinct will be to harden the infrastructure," said Professor Barford. 
"But keeping the sea at bay is hard. We can probably buy a little time, but in the long run it's just not going to be effective."
Professor Barford said recent hurricanes and storm surges in the eastern US had already given a taste of the kind of flooding that is to come. He said this study should serve as a “wake-up call” that prompts a discussion about how to protect the world’s precious internet from climate change.
Efforts have also been made in the UK to predict the impact of climate change on the nation’s digital infrastructure, with the major threats thought to be “flooding from increased winter rainfall, changes to humidity and temperature and high winds.”
https://www.independent.co.uk/environment/sea-levels-rise-internet-cables-climate-change-underground-new-york-miami-a8449716.html

Monday, July 16, 2018

THIS! Raising a Child in a Doomed World

Some would say our mistake was having our daughter in the first place

by Roy Scranton, The New York Times, July 16, 2018

I cried two times when my daughter was born. First for joy, when after 27 hours of labor the little feral being we’d made came yowling into the world, and the second for sorrow, holding the earth’s newest human and looking out the window with her at the rows of cars in the hospital parking lot, the strip mall across the street, the box stores and drive-throughs and drainage ditches and asphalt and waste fields that had once been oak groves. A world of extinction and catastrophe, a world in which harmony with nature had long been foreclosed. 

My partner and I had, in our selfishness, doomed our daughter to life on a dystopian planet, and I could see no way to shield her from the future.

Anyone who pays much attention to climate change knows the outlook is grim. It’s not unreasonable to say that the challenge we face today is the greatest the human species has ever confronted. And anyone who pays much attention to politics can assume we’re almost certainly going to botch it. To stop emitting waste carbon completely within the next five or 10 years, we would need to radically reorient almost all human economic and social production, a task that’s scarcely imaginable, much less feasible. It would demand centralized control of key economic sectors, enormous state investment in carbon capture and sequestration and global coordination on a scale never before seen, at the very time when the political and economic structures that held the capitalist world order together under American leadership after World War II are breaking apart. The very idea of unified national political action toward a single goal seems farcical, and unified action on a global scale mere whimsy.

And even if world leaders somehow got their act together, significant and dangerous levels of warming are still inevitable, baked into the system from all the carbon dioxide that has already been dumped. There’s a time lag between carbon dioxide increase and subsequent effects, between the wind we sow and the whirlwind we reap. Our lives are lived in that gap. My daughter was born there.

Barring a miracle, the next 20 years are going to see increasingly chaotic systemic transformation in global climate patterns, unpredictable biological adaptation and a wild spectrum of human political and economic responses, including scapegoating and war. After that, things will get worse. The middle and later decades of the 21st century — my daughter’s adult life — promise a global catastrophe whose full implications any reasonable person must turn away from in horror.

Some people might say the mistake was having a child in the first place. As Maggie Astor  reported, more and more people are deciding not to have children because of climate change. This concern, conscious or unconscious, is no doubt contributing to the United States’ record-low birthrate. Some people can’t bear the idea of having a child whose life is going to be worse than their own. Others, struggling with the ethics of living in a carbon-fueled consumer society, consider having children selfish and environmentally destructive.

Take the widely cited 2017 research letter by the geographer Seth Wynes and the environmental scientist Kimberly Nicholas, which argues that the most effective steps any of us can take to decrease carbon emissions are to eat a plant-based diet, avoid flying, live car free and have one fewer child — the last having the most significant impact by far. Wynes and Nicholas argue for teaching these values in high school, thus transforming society through education. On its face, this proposal might seem sensible. But when values taught in the classroom don’t match the values in the rest of society, the classroom rarely wins. The main problem with this proposal isn’t with the ideas of teaching thrift, flying less or going vegetarian, which are all well and good, but rather with the social model such recommendations rely on: the idea that we can save the world through individual consumer choices. We cannot.

Society is not simply an aggregate of millions or billions of individual choices but a complex, recursive dynamic in which choices are made within institutions and ideologies that change over time as these choices feed back into the structures that frame what we consider possible. All the while, those structures are being disrupted and nudged and warped and shaken by countless internal and external drivers, including environmental factors such as global warming, material and social innovation, and the occasional widespread panic. Which is just to say that we are not free to choose how we live any more than we are free to break the laws of physics. We choose from possible options, not ex nihilo.

Of course, nobody really needs to have children. It just happens to be the single strongest drive humans have, the fundamental organizing principle of every human society and the necessary condition of a meaningful human world. Procreation alone makes possible the persistence of human culture through time.

To take Wynes and Nicholas’s recommendations to heart would mean cutting oneself off from modern life. It would mean choosing a hermetic, isolated existence and giving up any deep connection to the future. Indeed, taking Wynes and Nicholas’s argument seriously would mean acknowledging that the only truly moral response to global climate change is to commit suicide. There is simply no more effective way to shrink your carbon footprint. Once you’re dead, you won’t use any more electricity, you won’t eat any more meat, you won’t burn any more gasoline, and you certainly won’t have any more children. If you really want to save the planet, you should die.

This is the choice David Buckel made one crisp April morning, when he walked from his Brooklyn apartment to Prospect Park, doused himself in gasoline and lit himself on fire. He was in good health. He had a partner and a daughter. While some might be inclined to ascribe his suicide to mental illness, the letters he left make it clear that his act was political. “Pollution ravages our planet, oozing inhabitability via air, soil, water and weather,” he wrote. “Most humans on the planet now breathe air made unhealthy by fossil fuels, and many die early deaths as a result — my early death by fossil fuel reflects what we are doing to ourselves.”

Buckel’s self-sacrifice takes the logic of personal choice to its ultimate end. But like most of us, I can’t or won’t make that choice. I’m committed to life in this world, the world I live in, in all its stupidity and suffering, because this world is the one everyone else lives in too: my colleagues and students, my friends and family, my partner and daughter. This world is the only one in which my choices have meaning. And this world, doomed as it is, is the only one that offers joy.

When my daughter was born I felt a love and connection I’d never felt before: a surge of tenderness harrowing in its intensity. I knew that I would kill for her, die for her, sacrifice anything for her, and while those feelings have become more bearable since the first delirious days after her birth, they have not abated. And when I think of the future she’s doomed to live out, the future we’ve created, I’m filled with rage and sorrow.

Every day brings new pangs of grief. Seeing the world afresh through my daughter’s eyes fills me with delight, but every new discovery is haunted by death. Reading to her from “Polar Bear, Polar Bear, What Do You Hear?,” I can’t help marveling at the disconnect between the animal life pictured in that book and the mass extinction happening right now across the planet. When I sing along with Elizabeth Mitchell’s version of “Froggie Went a-Courtin’,” I can’t help feeling like I’m betraying my daughter by filling her brain with fantastic images of a magical nonhuman world, when the actual nonhuman world has been exploited and despoiled. 

How can I read her “Winnie the Pooh” or “The Wind in the Willows” when I know the pastoral harmony they evoke is lost to us forever, and has been for decades? How soon do I explain to her what’s happening? In all the most important ways, it’s already too late.

Our children will not face the choices we face. They won’t have the opportunities we now have for action. They’ll confront a range of outcomes whose limits were determined by the choices we made. Yet while some degree of warming now appears inevitable, the range of possible outcomes over the next century is wide enough and the worst outcomes extreme enough that there is some narrow hope that revolutionary socio-economic transformation today might save billions of human lives and preserve global civilization as we know it in more or less recognizable form, or at least stave off human extinction. But the range of outcomes decreases every day, shifting month by month toward the more apocalyptic end of the spectrum, and waiting even five years may see the window for saving humanity shut.

We live in the gap between the wind and the whirlwind, but taking that gap for a reprieve is a mistake. The catastrophe is now, even if it’s almost impossible for most of us to see it. That very dissonance is perhaps the defining truth of our era, the key to its anxious, bipolar character.

The real choice we all face is not what to buy, whether to fly or whether to have children but whether we are willing to commit to living ethically in a broken world, a world in which human beings are dependent for collective survival on a kind of ecological grace. There is no utopia, no Planet B, no salvation, no escape. We’re all stuck here together. And living in that world, the only world there is, means giving up any claims to innocence or moral purity, since to live at all means to cause suffering.

Living ethically means understanding that our actions have consequences, taking responsibility for how those consequences ripple out across the web of life in which each of us is irrevocably enmeshed and working every day to ease what suffering we can. Living ethically means limiting our desires, respecting the deep interdependence of all things in nature and honoring the fact that our existence on this planet is a gift that comes from nowhere and may be taken back at any time.

I can’t protect my daughter from the future and I can’t even promise her a better life. All I can do is teach her: teach her how to care, how to be kind and how to live within the limits of nature’s grace. I can teach her to be tough but resilient, adaptable and prudent, because she’s going to have to struggle for what she needs. But I also need to teach her to fight for what’s right, because none of us is in this alone. I need to teach her that all things die, even her and me and her mother and the world we know, but that coming to terms with this difficult truth is the beginning of wisdom.

Roy Scranton is a professor of English at the University of Notre Dame. This essay was adapted from his new book, “We’re Doomed. Now What? Essays on War and Climate Change.

Friday, June 29, 2018

WaPo: A city in Oman just posted the world’s hottest low temperature ever recorded: 109 degrees



Temperature difference from normal at 10 p.m. local time Tuesday in Oman analyzed by American (GFS) model. (TropicalTidBits.com)

by Jason Samenow, Capital Weather Gang, The Washington Post, June 27, 2018

Over a period of 24 hours, the temperature in the coastal city of Quriyat, Oman, never dropped below 108.7 degrees (42.6 Celsius) Tuesday, most likely the highest minimum temperature ever observed on Earth.
For a location to remain no lower than 109 degrees around the clock is mind-boggling. In many locations, a temperature of 109 degrees even during the heat of the afternoon would be unprecedented. For example, in nearly  150 years of weather records, Washington, D.C.’s high temperature has never exceeded 106 degrees.
Quriyat’s suffocating low temperature, first reported by Jeff Masters at Weather Underground, breaks the world’s previous hottest minimum temperature of 107.4 degrees (41.9 Celsius), also set in Oman, on June 27, 2011.
Masters received word of the exceptional temperature from weather records expert Maximiliano Herrera. Incredibly, the temperature in Quriyat, Masters said, remained above 107.4 degrees (41.9 Celsius) for 51 straight hours. Its blistering afternoon high temperature of 121.6 degrees (49.8 Celsius) Tuesday was just about two degrees shy of Oman’s all-time heat record and its highest June temperature, Masters reported.
Quriyat, sometimes also spelled Qurayyat, is a small fishing village in northeast Oman adjacent to the Sea of Oman that spills into the Arabian Sea. The city’s population is just over 50,000, and it is about an hour southeast of Muscat, Oman’s capital.
This sweltering episode marked the second exceptional weather event to affect Oman in as many months. In May, Category 3 Tropical Cyclone Mekunu slammed into its southwest coast, making landfall near Salalah. It was the most intense tropical cyclone to make landfall on the Arabian Peninsula on record.
Tuesday’s record-breaking heat resulted from a strong, high-altitude, high-pressure system or heat dome anchored over the region, which pumped air temperatures up to 15 degrees above normal. Masters said sea surface temperatures in the adjacent waters were about 90 degrees, keeping air temperatures elevated even through the night and offering no reprieve from the oppressive conditions.
Tuesday’s 109-degree low, while the highest known, is not official and remains unverified. Although the World Meteorological Organization validates and maintains records for the hottest maximum world temperature, it does not do so for minimum temperatures.
Nevertheless, assuming it is legitimate, this weather extreme adds to a tremendous number of hot-weather milestones established around the world in just over the past year, which include:
All of these heat records are part and parcel of a planet that is trending hotter as greenhouse gas concentrations increase due to human activity. The past four years have been the hottest four years on record.
https://www.washingtonpost.com/news/capital-weather-gang/wp/2018/06/27/a-city-in-oman-just-set-the-worlds-hottest-low-temperature-ever-recorded-109-degrees/

Tuesday, June 19, 2018

Harvests will shrink as the planet heats up and crops will be less nutritious

Shrinking harvests likely as heat increases

A warmer world could mean shrinking harvests and a more meagre diet for millions of people, according to two new studies.
by Tim Radford, Climate News Network, June 19, 2018

LONDON 
– A hotter world could also be a hungrier one, with shrinking harvests and poorer quality plants. As planetary temperatures rise in response to ever more profligate combustion of fossil fuels, climate change could lower the yield of  vegetable and legume crops – and at the same time reduce their nutritional content.
And the same high end-of-the-century temperatures could raise the risk of massive, near-global losses for the world’s most widely grown cereal, maize.
This double blow comes close upon the evidence – from field trials over many years – that another global staple, rice, is likely to become less rich in protein and vitamins as temperatures increase.
British researchers report in the Proceedings of the National Academy of Sciences that they studied 174 research papers based on 1,540 experiments in 40 countries between 1975 and 2016, on the probable effect of changes in water supplies, ozone, atmospheric carbon dioxide, and ambient temperatures, on vegetables and legumes.
They found that on the basis of changes predicted for later this century, average yields of vegetables could fall by 35%, and legumes by 9%. There has been evidence that more atmospheric carbon dioxide could fertilize more plant growth, but other accompanying changes – greater extremes of heat, drought, flood and so on – could cancel out any such gains.
“As the planet warms, it becomes more likely for different countries to simultaneously experience major crop losses”
Pauline Scheelbeck, of the London School of Hygiene and Tropical Medicine, who led the study, called the finding “a real threat to global agricultural production, with likely impacts on food security and population health.”
Scientists have been warning for at least five years of the potential impact of climate change on agriculture and food supply: other studies have shown that fruit and vegetable supplies could be at risk.
US researchers report – once again, in the Proceedings of the National Academy of Sciences – that they took a fresh look at the response of markets to what they call “volatility” in the global crop of just one cereal: maize, or corn.
Heavy dependence
This is grown widely: it is a staple for humans and fodder for livestock; it provides oil for cooking and has even been turned into fuel for motor cars. It is traded worldwide, but four countries – the US, Brazil, Argentina, and Ukraine – account for more than 85% of all exports. The chance that all four exporters would have bad harvests in the same year right now is almost zero.
But under a warming of 2 °C – a level which 195 nations agreed in Paris in 2015 to keep well below – this risk would rise to 7%. If global temperatures rise by 4 °C, which is what will happen if humans go on burning ever more fossil fuels, the chance that all four maize exporters would have harvest failures at the same time rises to 86%. And, if that happened, corn prices would rise dramatically.
“When people think about climate change and food, they initially think about drought, but it’s really extreme heat that’s very detrimental for crops,” said Michelle Tigchelaar of the University of Washington, who led the research.
“We find that as the planet warms, it becomes more likely for different countries to simultaneously experience major crop losses, which has big implications for food prices and food security.”