Latest climate models show more intense droughts to come

Latest climate models show more intense droughts to come
The Maranoa River south of Mitchell, Queensland, during the 2017 drought. Credit: Chris Fithall (Flickr Creative Commons CC BY 2.0)

An analysis of new climate model projections by Australian researchers from the ARC Centre of Excellence for Climate Extremes shows southwestern Australia and parts of southern Australia will see longer and more intense droughts due to a lack of rainfall caused by climate change.

But Australia is not alone. Across the globe several important agricultural and forested regions in the Amazon, Mediterranean and southern Africa can expect more frequent and intense  droughts. While some regions like central Europe and the boreal forest zone are projected to get wetter and suffer fewer droughts, those droughts they do get are projected to be more intense when they occur.

The research published in Geophysical Research Letters examined rainfall-based drought using the latest generation of  models (known as CMIP6), which will inform the next IPCC assessment report on .

“We found the new models produced the most robust results for future droughts to date and that the degree of the increase in drought duration and intensity was directly linked to the amount of greenhouse gases emitted into the atmosphere,” said lead author Dr. Anna Ukkola.

“There were only slight changes to the areas of drought under a mid-range emissions scenario versus a high-emissions pathway. However, the change in the magnitude of drought with a higher emissions scenario was more marked, telling us that early mitigation of greenhouse gases matters.”

Much of the earlier research into future droughts only considered changes to average rainfall as the metric to determine how droughts would alter with global warming. This often produced a highly uncertain picture.

But we also know that with climate change, rainfall is likely to become increasingly variable. Combining metrics on variability and mean rainfall, the study increased clarity around how droughts would change for some regions.

The researchers found the duration of droughts was very closely aligned to changes in the average rainfall, but the intensity of droughts was much more closely connected to the combination of average rainfall and variability. Regions with declining average rainfall like the Mediterranean, Central America and the Amazon are projected to experience longer and more frequent droughts. Meanwhile other regions, such as the boreal forests are expected to experience shorter droughts in line with increasing .

However, the situation is different for drought intensity alone with most regions projected to experience more intense rainfall droughts due to increasing rainfall variability. Importantly, the researchers were unable to locate any  that showed a reduction in future drought intensity. Even regions with long-term increases in rainfall, such as central Europe, can expect more intense droughts as rainfall becomes more variable.

“Predicting future changes in drought is one of the greatest challenges in climate science but with this latest generation of models and the opportunity to combine different  metrics in a more meaningful way we can gain a clearer insight into the future impacts of climate change,” said Dr. Ukkola.

“However, while these insights grow clearer with each advance, the message they deliver remains the same—the earlier we act on reducing our emissions, the less economic and social pain we will face in the future.”

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OU meteorologist expects severe drought and heavy rain events to worsen globally

Climate change: May was sunniest calendar month on record in UK

Low water levels in the Llwyn-on reservoir in Taf Fawr valleyImage copyrightGETTY IMAGES
Image captionLow water levels can be seen in Llwyn-on reservoir in Taf Fawr valley, Wales

May was the sunniest calendar month on record, and spring was the sunniest spring, the Met Office has said.

The UK enjoyed 266 hours of sunshine in May – surpassing the previous record of 265 hours in June 1957.

And it is even more extraordinary following a drenching winter, with record rain in February.

Meteorologists say they are amazed at the sudden switch from extreme wet to extreme dry – it is not “British” weather.

On average the UK gets 436 hours of sunshine between March and the end of May.

Since 1929, only 10 years have had more than 500 hours. And none has got more than 555 hours.

Scientists say the recent weather in the UK has been unprecedented and astounding.

This year we’ve bathed in an extraordinary 626 hours – smashing the previous record by a “staggering” amount, one Met Office worker said.

It is because the jet stream has locked the fine weather in place, just as it locked the previous winter rainfall in place.

Floods near The Boat Inn in Jackfield near IronbridgeImage copyrightPA MEDIA
Image captionThe Met Office declared February 2020 as the wettest February on record

Professor Liz Bentley, chief executive of the Royal Meteorological Society, told BBC News: “We’ve swung from a really unsettled spell with weather systems coming in off the Atlantic to a very, very settled spell.

“It’s unprecedented to see such a swing from one extreme to the other in such a short space of time. That’s what concerns me. We don’t see these things normally happening with our seasons.

“It’s part of a pattern where we’re experiencing increasingly extreme weather as the climate changes.”

Mark McCarthy, from the Met Office, said: “If we look at the difference in rainfall that’s fallen over the winter compared to spring it is the largest difference in rainfall amount in our national series from 1862.

“The sunshine statistics are really astounding.

“The stand out is by how much sunshine has broken the previous record – set in 1948. There’s been more sunshine than most of our past summer seasons. It’s quite remarkable.”

One of his colleagues described the figures as “absolutely staggering”.

Bournemouth beachImage copyrightGETTY IMAGES
Image captionCrowds flocked to the beach at Bournemouth, to enjoy the soaring temperatures on bank holiday Monday last month

The Met Office says this year is not an indicator of the future, because the jet stream might behave differently.

Scientists suspect man-made climate change may be implicated, but it is too soon to tell.

Some of them believe the rapid man-made heating of the Arctic, which has led to record temperatures and wildfires in Siberia, may be influencing the jet stream, although that is not proven.

Professor Joe Smith, chief executive of the Royal Geographical Society, told BBC News: “For many people, the recent long sunny spell is simply ‘nice weather’.

“In a wider context it’s a signal of the increasing unpredictability of the UK’s climate. Planning for the growing season is starting to resemble a night at the gambling tables.

“The fact remains that bold early actions to slash emissions can still cut the larger risks associated with climate change in the UK and around the world”.

Why ‘Carbon-Cycle Feedbacks’ Could Drive Temperatures Even Higher

Dead trees are visible in the canopy of the Amazon rainforest, 60 miles southwest of Macapa, Brazil.

Dead trees are visible in the canopy of the Amazon rainforest, 60 miles southwest of Macapa, Brazil. DANIEL BELTRÁ / GREENPEACE

New research indicates that parts of the Amazon and other tropical forests are now emitting more CO2 than they absorb. Some scientists are concerned this development, which is not yet incorporated into climate models, could put the temperature goals set by the Paris Agreement out of reach.

    It is not often you meet a scientist breathless with excitement about their new findings. But it happened to me last September at the National Institute for Space Research in the Brazilian research city of Sao Jose dos Campos. Atmospheric chemist Luciana Gatti was rushing to tell her colleagues the result of her latest analysis of carbon dioxide emissions from the Amazon rainforest, which she had completed that morning.

    For a decade, her team had been sampling the air from sensors on aircraft flying over the world’s largest rainforest. Their collating of recent results showed that, perhaps for the first time in thousands of years, a large part of the Amazon had switched from absorbing CO2 from the air, damping down global warming, to being a “source” of the greenhouse gas and thus speeding up warming.

    “We have hit a tipping point,” Gatti almost shouted, caught between elation at her discovery and anguish at the consequences.

    As she spoke, fires were burning across the Amazon, making headlines around the globe. But her findings were not the short-term result of the fires. They were based on measurements from before the upsurge in fires, and showed a long-term trend. She had previously observed the same thing briefly during drought years. But now it no longer mattered if it was a wet or a dry year, or how many fires there were, the sink had become a source. “Each year it gets worse,” she said. “We have to stop deforestation while we work out what to do.”

    Gatti asked me to keep silent for the time being, while she prepared her data for publication. When I contacted her this month, her paper was still being finalized. But I can now tell the story. It vividly illustrates a growing dismay among climate scientists, who are seeing ecosystems around the world going the way of the Amazon.

    Without such “carbon sinks,” global warming to date would have been twice as great and already exceeded the 2-degree target.

    The scientists are warning that past climate models used by the UN’s Intergovernmental Panel on Climate Change (IPCC) have not fully reflected the scale of the warming that lies ahead as carbon sinks die. These revelations are coming from three areas of research:

    • Studies such as Gatti’s in the Amazon, showing forests turning from sinks to sources of CO2;
    • A new generation of climate models that incorporate these findings into future projections of climate change, and whose early outputs are just emerging;
    • Recent revelations that ecosystems are releasing rising volumes of methane, the second most important greenhouse gas and of vital importance for temperatures in the next couple of decades.

    The extra emissions, known as carbon-cycle feedbacks, could already be making the prospect of keeping warming below 2 degrees Celsius — the target agreed to in the Paris climate accord in 2015 — all but impossible. The new modeling is likely to result in more pessimistic projections in the next scientific assessment from the IPCC, which is due — coronavirus-permitting — in April 2021.

    Our planet’s land and oceans currently take up about half of all the CO2 we put into the atmosphere. The gas dissolves in seawater and is absorbed by growing plants. Without these “carbon sinks,” warming to date would have been twice as great. We would already have exceeded the 2-degree target. But the question now is whether the take-up will remain as it is, or diminish.

    That depends on how ecosystems respond to the extra gas in the air. This response takes two competing forms. First, the extra CO2 speeds up plant growth. This fertilization effect means that forests absorb more CO2 as they grow, slowing the build-up in the air. Good news.

    A lone nut tree remains in a logged area of the Amazon in the Brazilian state of Pará.

    A lone nut tree remains in a logged area of the Amazon in the Brazilian state of Pará. DANIEL BELTRÁ / GREENPEACE

    But the bad news is that the higher temperatures, also brought about by the added CO2, are pulling in the other direction, reducing nature’s ability to soak up CO2. This happens because warmer ocean waters dissolve less CO2, while soils release more of the gas and some forests suffer heat stress and die or catch fire.

    Both these feedbacks are in play. But the debilitating effects of the warming, especially when combined with deforestation, are becoming increasingly dominant, ecologists say. That is what Gatti has seen in the Amazon. And the trend is often happening faster than expected.

    Gatti’s findings, while relating to the southeast of the Amazon, the region’s most heavily deforested area, suggest that the rainforest as a whole could be close to flipping from a sink to a source of CO2. The ability of intact areas of the rainforest to absorb CO2 have already halved since the 1990s, says Carlos Nobre of the University of Sao Paulo, Brazil’s most noted climate scientist. Passing the tipping point for the whole forest would release more than 50 billion tons of carbon, he said recently, which is the equivalent of five years of global fossil-fuel and industrial emissions

    Non-tropical forests remain largely in carbon “sink” mode. But other tropical rainforests appear to be following the Amazon in moving toward becoming carbon sources. Wannes Hubau, now at the Royal Museum of Central Africa in Belgium, reported recently that “overall, the uptake of carbon into Earth’s intact tropical forests peaked in the 1990s” and has been declining since. The jungles of tropical Africa began showing increased carbon losses around 2010, he found.

    Some researchers think these alarming findings are unlikely to be realistic in future predictions and should be dismissed.

    Another big concern is the impact of thawing permafrost. This frozen ground, which covers large areas of the far north, holds hundreds of billions of tons of carbon that could be released as the land thaws. How much and how fast is an unresolved question. But the signs are not good. One recent study in northern Canada found thawing had reached depths “already exceeding those projected to occur by 2090.”

    The risks of such rapid runaway carbon releases to the atmosphere have been worrying ecologists for a while. That worry is now being reinforced by the projections of a new generation of climate models designed to factor in how ecosystems respond to climate change.

    Until now, most climate models have largely confined themselves to assessing how our CO2 emissions warm the air, and how that warming interacts with physical feedbacks such as reduced ice cover, elevated atmospheric water vapor, and changes to clouds. This remains a work in progress. I wrote here on Yale Environment 360 in February how new field research suggests that the ability of clouds to keep us cool could be drastically reduced as the world warms, pushing global heating into overdrive.

    When ecological feedbacks have been included in the models, it has mostly been in a very simplistic way. But new models being developed for the next IPCC assessment of climate science are changing that. For the first time, they capture the full range of possibilities for how nature’s ability to soak up CO2 may change as the climate changes, says Richard Betts of Britain’s Met Office Hadley Centre, one of the world’s top climate modeling groups. His initial assessment of the early outcomes of these new models is sounding alarm bells.

    A thawing section of ice-rich permafrost falls into the sea along Drew Point, Alaska.

    A thawing section of ice-rich permafrost falls into the sea along Drew Point, Alaska. BENJAMIN JONES / USGS

    Writing with Zeke Hausfather, of the Breakthrough Institute, in a blog this month on the website Carbon Brief, he warns that many of the projections of the new models “end up with much higher CO2 concentrations by 2100.” That means more warming. “The combination of high climate sensitivity and high carbon-cycle feedbacks could result in substantial warming, even under more moderate emissions scenarios,” they say.

    Even a scenario that is “reasonably consistent with currently enacted climate policies” could deliver up to 5 degrees C of warming rather than the current estimate of 3 degrees. This, Betts says, is “because the upper end of possible feedbacks results in 40 percent more CO2 in the air than previously supposed: 936 parts per million [ppm] by 2100, compared to a prediction without the carbon-cycle feedbacks of 670 ppm.” (Current levels are 415 ppm, and pre-industrial levels were around 280 ppm.)

    And if the world backtracks on existing climate policies, things could be a great deal worse. One such scenario based on this produced an almost unimaginable warming of 7.7 degrees C (13.9 degrees Fahrenheit) by the end of the century, rather than the 6 degrees C predicted without the carbon-cycle feedbacks.

    Some researchers think such alarming findings should be dismissed out of hand. Katarzyna Tokarska of ETH Zurich, with others, claimed recently that models with extreme warming would not accurately “predict” current climate — and so were biased and unlikely to be realistic in their future predictions. According to these researchers, this means that, with “ambitious” action to reduce emissions, the world could meet the temperature target set by the Paris Agreement.

    But others say that if climate change pushes ecosystems such as the Amazon beyond key tipping points, then the present is unlikely to be a reliable guide to the future.

    The growing concern about CO2 feedbacks comes amid news of a trend in rising atmospheric levels of methane.

    Betts and Hausfather say that while the extreme outcomes of the new models are not the most likely, they represent “a risk that merits consideration.”

    Peter Cox of the University of Exeter first introduced the carbon cycle into climate modeling in a 2000 paper that predicted that “carbon-cycle feedbacks could significantly accelerate climate change over the 21st century.” He says today that even he has been “surprised by the large increases in CO2 in recent models when carbon-cycle feedbacks are switched on.” He warns that while the new models may not yet be accurate representations of the future, “they are very helpful to reveal the sensitivities of the real world.”

    So it is a shame that not all these new carbon-savvy predictions will be included in the next IPCC assessment, as first intended. Hausfather says that the international effort to develop the new models is running “a year behind schedule,” and many of them will miss the deadline for being included as new research findings in the assessment, which is this October.

    The growing concern about CO2 feedbacks comes on top of alarm about trends in atmospheric levels of the second most important greenhouse gas, methane. These are more than twice pre-industrial levels, and after a decade of stability until 2007 they have been rising again sharply. The National Oceanic and Space Administration (NOAA) estimated this month that methane levels in the atmosphere reached a record 1,875 parts per billion in 2019, after the second largest year-on-year leap ever recorded.

    How come? Euan Nisbet of Royal Holloway, University of London, says isotopic analysis shows industrial emissions such as those from fracking remain important sources of methane. But the major reason for the recent upsurge is microbial emissions, mostly from the tropics.

    A satellite view of the Sudd wetland in South Sudan, where rising temperatures are resulting in a spike in methane emissions.

    A satellite view of the Sudd wetland in South Sudan, where rising temperatures are resulting in a spike in methane emissions. COPERNICUS DATA 2019 / ESA / SENTINEL-2

    Microbial emissions include agricultural sources such as rice paddies and the guts of cattle, but also microbes in natural ecosystems, particularly wetlands. When Nisbet flew from Uganda to Zambia collecting air samples last year, he found what he called “a great plume of methane” rising from wetland swamps around Lake Victoria and Lake Bangweulu. Mark Lunt of Edinburgh University has also found a dramatic increase in emissions from the Sudd, a vast wetland downstream of Lake Victoria on the Nile in South Sudan. The presumption is that warmer temperatures are making microbes more active.

    None of this methane increase is built into even the new climate models with carbon-cycle feedbacks. These models mostly assume that methane levels in the air will remain stable. But the concern is growing that, even if technology can reduce industrial emissions, a warmer world will drive a continuing surge in methane levels — and more warming as a consequence.

    That is a very big problem for efforts to meet the Paris target of halting warming below 2 degrees C.

    Methane typically lasts in the atmosphere for only a decade – much less than CO2. But while it is there, it packs a big warming punch. Measured over 20 years, each molecule of methane emitted has 84 times more warming effect than each molecule of CO2.

    Climate models conventionally assess the warming impacts of greenhouse gases over a century. This effectively tunes them to emphasize the importance of C02, and relegates methane to an also-ran. But if they were tuned to the shorter timeframe, methane would appear almost three times more important.

    It seems odd that this shorter timeframe is rarely adopted, given that the world risks exceeding its two-degree warming limit by 2050. As Nisbet puts it, if natural ecosystems keep pumping out more methane as the world warms, “it may become very difficult to meet the Paris goals.”

    Nature, it seems, is biting back. Having so far absorbed our pollution indiscretions, it now seems to be making them worse. We only have ourselves to blame.

    It Hit 80 Degrees in the Arctic This Week

    This story will provide important context for the headline, and I encourage you to read it—but really, the headline tells you what you need to know: It was 80 degrees Fahrenheit above the Arctic Circle this week.

    A little farther south, in Siberia—you know, the region of world we reference when we want to connote something cold—it was 86 degrees Fahrenheit. Arctic sea ice in the neighboring Kara Sea took the deepest May nose dive ever recorded. Oh, and random swaths of the region are on fire. Things are extremely wrong.

    Let’s start with the heat above Arctic Circle. Mika Rantanen, a researcher at the Finnish Meteorological Institute, flagged a map showing blistering heat across western Siberia. The region has been the epicenter of an explosive heat wave that has rippled across the Arctic this week. Models forecast temperatures there will be as much as 36 degrees Fahrenheit above normal for this time of year. The heat could break a bit by the middle of next week, but widespread warmth will continue to grip the region.

    “The primary reason for the heat is a so called upper-level ridge, am omega-shaped high pressure system which allows clear skies and sinking air motion,” Rantanen told Earther in a Twitter direct message. “However, what I think is the most noteworthy aspect is that that particular area in Russia has been record-warm in winter. So I believe that lack of snow can play a role as the heat us not consumed into melting of snow.”

    On land, it means wildfires continue to spread. Pierre Markuse, a satellite monitoring expert, has kept an eye on the series of increasingly odd fires above the Arctic Circle, a place known more for ice than fire. Most of the blazes he’s documented are in the eastern portion of Siberia, which also dealt with its fair share of heat all year in addition to low snowpack. Seeing fires burn next to braided rivers and large patches of unmelted snow is truly a mood for our current era of climate destabilization.

    Totally cool and normal fire burning above the Arctic Circle.
    Totally cool and normal fire burning above the Arctic Circle.
    Image: Pierre Markuse (Flickr)

    Then there are the ocean impacts, because climate change doesn’t just stop at the water’s edge. Warmth has washed over the seas that border Siberia, and the Kara Sea north of the western part of the region has seen the most precipitous decline in sea ice. After a slow decline in the first part of May, warm air has fueled a stark decline in sea ice. As of earlier this week, ice extent was the lowest level that’s ever been record in May. It stands as a stark outlier, especially when looking at how ice behaved in the 1980s. I’m old enough to remember when the ice in the Kara Sea used to decline in July.

    Numerous other seas that ring the Arctic have also been losing ice. And while they’re not at record-setting levels like the Kara Sea, the Bering and Barents Seas are both at some of their lowest levels on record for this time of year.

    These impacts are the latest in a litany of climate horrors for the Arctic as a whole. Last summer, it reached nearly 95 degrees Fahrenheit above the Arctic Circle in Sweden. The same summer, the mercury hit 70 degrees Fahrenheit at the northernmost settlement on the planet. Greenland also melted and burned. That’s just some of what happened last year. I could list the same for 2018. And 2017. And you get the point.

    I have to be honest. I’m getting sick of writing these stories. The Arctic is warming twice as fast as the rest of the globe, and what’s happening there is unprecedented. But how many ways can you talk about the fact that the Arctic is just extremely, massively fucked by climate change when the impacts are relentless? After a while, the degrees above normal start to feel normal, and the records are ephemeral, set to broken again the next year.

    But here we are with just another absolutely outlandish occurrence. I’ll keep writing about them, because even if the records start to blend together, that in itself is a sign we really need to get our shit together and cut emissions now.

    Update May 22, 11:25 a.m.: Mika Rantanen’s comments have been added to this post.

    The world is on lockdown. So where are all the carbon emissions coming from?

    Tayfun Coskun / Anadolu Agency / Getty Images

    Pedestrians have taken over city streets, people have almost entirely stopped flying, skies are blue (even in Los Angeles!) for the first time in decades, and global CO2 emissions are on-track to drop by … about 5.5 percent.

    Wait, what? Even with the global economy at a near-standstill, the best analysis suggests that the world is still on track to release 95 percent of the carbon dioxide emitted in a typical year, continuing to heat up the planet and driving climate change even as we’re stuck at home.

    A 5.5-percent drop in carbon dioxide emissions would still be the largest yearly change on record, beating out the financial crisis of 2008 and World War II. But it’s worth wondering: Where do all of those emissions come from? And if stopping most travel and transport isn’t enough to slow down climate change, what will be?

    Transportation makes up a little over 20 percent of global carbon dioxide emissions, according to the International Energy Agency. (In the United States, it makes up around 28 percent.) That’s a significant chunk, but it also means that even if all travel were completely carbon-free (imagine a renewable-powered, electrified train system, combined with personal EVs and battery-powered airplanes), there’d still be another 80 percent of fossil fuel emissions billowing into the skies.

    So where are all those emissions coming from? For one thing, utilities are still generating roughly the same amount of electricity — even if more of it’s going to houses instead of workplaces. Electricity and heating combined account for over 40 percent of global emissions. Many people around the world rely on wood, coal, and natural gas to keep their homes warm and cook their food — and in most places, electricity isn’t so green either.

    Even with a bigger proportion of the world working from home, people still need the grid to keep the lights on and connect to the internet. “There’s a shift from offices to homes, but the power hasn’t been turned off, and that power is still being generated largely by fossil fuels,” Schmidt said. In the United States, 60 percent of electricity generation still comes from coal, oil, and natural gas. (There is evidence, however, that the lockdown is shifting when people use electricity, which has some consequences for renewables.)

    Manufacturing, construction, and other types of industry account for approximately 20 percent of CO2 emissions. Certain industrial processes like steel production and aluminum smelting use huge amounts of fossil fuels — and so far, Schmidt says, that type of production has mostly continued despite the pandemic.

    The reality is that emissions need to be cut by 7.6 percent every year to keep global warming from surpassing 1.5 degrees Celsius above pre-industrial levels — the threshold associated with the most dangerous climate threats — according to an analysis by the United Nations Environment Program. Even if the global lockdown and economic slump reduce emissions by 7.6 percent this year, emissions would have to fall even more the year after that. And the year after that. And so on.

    In the middle of the pandemic, it’s become common to point to clear skies in Los Angeles and the cleaner waters of Venice as evidence that people can make a difference on climate change. “The newly iconic photos of a crystal-clear Los Angeles skyline without its usual shroud of smog are unwanted but compelling evidence of what can happen when individuals stop driving vehicles that pollute the air,” wrote Michael Grunwald in POLITICO magazine.

    But these arguments conflate air and water pollution — crucial environmental issues in their own right! — with CO2 emissions. Carbon dioxide is invisible, and power plants and oil refineries are still pumping it into the atmosphere. Meanwhile, natural gas companies and livestock farming (think cow burps) keep releasing methane.

    “I think people should bike instead of driving, and they should take the train instead of flying,” said Schmidt. “But those are small, compared to the really big structural things that haven’t changed.”

    It’s worth remembering that a dip in carbon emissions won’t lead to any changes in the Earth’s warming trend. Some scientists compare carbon dioxide in the atmosphere to water flowing into a leaky bathtub. The lockdown has turned the tap down, not off. Until we cut emissions to net-zero — so that emissions flowing into the atmosphere are equivalent to those flowing out — the Earth will continue warming.

    That helps explain why 2020 is already on track to be the warmest ever recorded, beating out 2016. In a sad irony, the decrease in air pollution may make it even hotter. Veerabhadran Ramanathan, a professor at the Scripps Institution of Oceanography at University of California, San Diego, explained that many polluting particles have a “masking” effect on global warming, reflecting the sun’s rays, canceling out some of the warming from greenhouse gas emissions. With that shield of pollution gone, Ramanathan said, “We could see an increase in warming.”

    Appreciate the bluer skies and fresher air, while you can. But the emissions drop from the pandemic should be a warning, not a cause for celebration: a sign of how much further there is to go.

    Update: As of April 30, the International Energy Agency estimates that carbon emissions will fall by 8 percent this year. The IEA drew on more data than an earlier CarbonBrief analysis which estimated a drop of 5.5 percent.

    What Causes Climate Change?

    climate change













    Graph providing evidence that atmospheric CO2 has increased since the Industrial Revolution




    Who emits the most CO2?







    It’s already getting too hot and humid in some places for humans to survive

    Extreme conditions are happening more often than scientists previously thought

    Temperatures Soar To Highest Of The YearPhoto by Peter Macdiarmid/Getty Images

    A combination of heat and humidity so extreme that it’s unendurable isn’t just a problem for the future — those conditions are already here, a new study finds. Off-the-chart readings that were previously thought to be nearly nonexistent on the planet today have popped up around the globe, and unyielding temperatures are becoming more common.

    Extreme conditions reaching roughly 115 degrees Fahrenheit on the heat-index scale — a measurement of both heat and humidity that’s often referred to as what the temperature “feels like” — doubled between 1979 and 2017, the study found. Humidity and heat are a particularly deadly combination, since humidity messes with the body’s ability to cool itself off by sweating. The findings imply that harsh conditions that scientists foresaw as an impending result of climate change are becoming reality sooner than expected.

    “We may be closer to a real tipping point on this than we think,” Radley Horton, co-author of the new study published today in the journal Science Advances, said in a statement. His previous research had projected that the world wouldn’t experience heat and humidity beyond human tolerance for decades.

    More intense and frequent heat events are one of the symptoms of climate change, a lot of research has shown. But most of those studies were based on readings that looked at averages over a wide area over a long period of time. Instead, Horton and his co-authors looked closely at hourly data from 7,877 weather stations around the world. They used the “wet bulb” centigrade scale, which measures other factors such as wind speed and solar radiation on top of heat and humidity.

    That’s how they found more than a thousand readings of severe heat and humidity, reaching wet bulb readings of 31 degrees Celsius, that were previously thought to be very rare. Along the Persian Gulf, they saw more than a dozen readings above what’s thought to be the human tolerance limit of 35 degrees Celsius on the wet bulb scale. That’s the highest wet bulb reading that scientific literature has ever documented. In 2015, the city of Bandar Mahshahr in Iran experienced a wet bulb reading just under 35 degrees Celsius. At more than 160 degrees Fahrenheit on the heat-index scale, that’s about 30 degrees higher than where the National Weather Service’s heat-index range ends — and it’s a scenario that climate models hadn’t forecast to happen until the middle of the century.

    They make the case that future studies ought to take a similarly localized look to get a better understanding of how climate change is playing out in communities that will feel the crunch ahead of the rest of the world. A Pulitzer prize-winning series by The Washington Post took this sort of approach in a series about places where average temperatures have already risen 2 degrees Celsius, the threshold at which the Paris climate accord aims to keep the globe from surpassing.

    “If you zoom in you see things that you don’t see at a larger scale,” says Colin Raymond, lead author and a postdoctoral researcher at NASA’s Jet Propulsion Laboratory. “At the smallest scale, it’s more intense.” One of the limitations to their study, according to Raymond, is that there are places across the globe that simply lack weather stations. So what they were able to document could be happening at an even wider scale, there just aren’t tools in place yet to make those measurements everywhere.

    Extreme heat already kills more people in the US than any other weather-related event.

    In 50 years, between 1 to 3 billion people could find themselves living in temperatures so hot that they’re outside the range in which humans have been able to thrive, found another study published this week. Just how many billions will face that future depends on what action is taken now to stop the planet from dangerously overheating.

    The emergence of heat and humidity too severe for human tolerance


     See all authors and affiliations

    Science Advances  08 May 2020:
    Vol. 6, no. 19, eaaw1838
    DOI: 10.1126/sciadv.aaw1838


    Humans’ ability to efficiently shed heat has enabled us to range over every continent, but a wet-bulb temperature (TW) of 35°C marks our upper physiological limit, and much lower values have serious health and productivity impacts. Climate models project the first 35°C TW occurrences by the mid-21st century. However, a comprehensive evaluation of weather station data shows that some coastal subtropical locations have already reported a TW of 35°C and that extreme humid heat overall has more than doubled in frequency since 1979. Recent exceedances of 35°C in global maximum sea surface temperature provide further support for the validity of these dangerously high TW values. We find the most extreme humid heat is highly localized in both space and time and is correspondingly substantially underestimated in reanalysis products. Our findings thus underscore the serious challenge posed by humid heat that is more intense than previously reported and increasingly severe.


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    Humans’ bipedal locomotion, naked skin, and sweat glands are constituents of a sophisticated cooling system (1). Despite these thermoregulatory adaptations, extreme heat remains one of the most dangerous natural hazards (2), with tens of thousands of fatalities in the deadliest events so far this century (34). The additive impacts of heat and humidity extend beyond direct health outcomes to include reduced individual performance across a range of activities, as well as large-scale economic impacts (57). Heat-humidity effects have prompted decades of study in military, athletic, and occupational contexts (89). However, consideration of wet-bulb temperature (TW) from the perspectives of climatology and meteorology began more recently (1011).

    While some heat-humidity impacts can be avoided through acclimation and behavioral adaptation (12), there exists an upper limit for survivability under sustained exposure, even with idealized conditions of perfect health, total inactivity, full shade, absence of clothing, and unlimited drinking water (910). A normal internal human body temperature of 36.8° ± 0.5°C requires skin temperatures of around 35°C to maintain a gradient directing heat outward from the core (1013). Once the air (dry-bulb) temperature (T) rises above this threshold, metabolic heat can only be shed via sweat-based latent cooling, and at TW exceeding about 35°C, this cooling mechanism loses its effectiveness altogether. Because the ideal physiological and behavioral assumptions are almost never met, severe mortality and morbidity impacts typically occur at much lower values—for example, regions affected by the deadly 2003 European and 2010 Russian heat waves experienced TW values no greater than 28°C (fig. S1). In the literature to date, there have been no observational reports of TW exceeding 35°C and few reports exceeding 33°C (9111415). The awareness of a physiological limit has prompted modeling studies to ask how soon it may be crossed. Results suggest that, under the business-as-usual RCP8.5 emissions scenario, TW could regularly exceed 35°C in parts of South Asia and the Middle East by the third quarter of the 21st century (1416).

    Here, we use quality-assured station observations from HadISD (1718) and high-resolution reanalysis data from ERA-Interim (1920), verified against radiosondes and marine observations (see the Supplementary Materials) (2122), to compute TW baseline values, geographic patterns, and recent trends. Uncertainties in TW from station data due to instrumentation and procedures are on the order of 0.5° to 1.0°C in all regions considered, an important consideration for proper interpretation of the results. Our approach of using TW and sea surface temperature (SST) observations as guidance for future TW projections offers a different line of evidence from previous research that used coupled or regional models without explicitly including historical station data.


    Our survey of the climate record from station data reveals many global TW exceedances of 31° and 33°C and two stations that have already reported multiple daily maximum TW values above 35°C. These conditions, nearing or beyond prolonged human physiological tolerance, have mostly occurred only for 1- to 2-hours’ duration (fig. S2). They are concentrated in South Asia, the coastal Middle East, and coastal southwest North America, in close proximity to extraordinarily high SSTs and intense continental heat that together favor the occurrence of extreme humid heat (214). Along coastlines, the marine influence is manifest via anomalous onshore low-level winds during midday and afternoon hours, and these wind shifts can cause rapid dew point temperature (Td) increases in arid and semiarid coastal areas (figs. S3 to S9). Regionally coherent observational evidence supports these intense values: Of the stations along the Persian Gulf coastline with at least 50% data availability over 1979 to 2017, all have a historical 99.9th percentile of TW (the value exceeded roughly 14 times in 39 years) above 31°C (Fig. 1; see fig. S1 for the all-time maximum). In the ERA-Interim reanalysis, the highest values are similarly located over the Persian Gulf and immediately adjacent land areas, as well as parts of the Indus River Valley (fig. S10). The spatiotemporal averaging inherent in reanalysis products causes ERA-Interim to be unable to represent the short durations and small areas of critical heat stress, causing its extreme TW values to be substantially lower than those of weather stations across the tropics and subtropics (fig. S11). In the Persian Gulf and adjacent Gulf of Oman, these differences are consistently in the range of −2° to −4°C (fig. S12). Larger bias but similar consistency is present along the eastern shore of the Red Sea, presenting a basis for future studies examining the reasons for this behavior, as well as further comparisons between station and reanalysis data.

    Fig. 1 Observed global extreme humid heat.

    Color symbols represent the 99.9th percentile of observed daily maximum TW for 1979–2017 for HadISD stations with at least 50% data availability over this period. Marker size is inversely proportional to station density.

    Other >31°C hotspots in the weather station record emerge through surveying the globally highest 99.9th TW percentiles: eastern coastal India, Pakistan and northwestern India, and the shores of the Red Sea, Gulf of California, and southern Gulf of Mexico (Fig. 1). All are situated in the subtropics, along coastlines (typically of a semienclosed gulf or bay of shallow depth, limiting ocean circulation and promoting high SSTs), and in proximity to sources of continental heat, which together with the maritime air comprise the necessary combination for the most exceptional TW (11). That subtropical coastlines are hotspots for heat stress has been noted previously (2324); our analysis makes clear the broad geographic scope but also the large intraregional variations (Fig. 1). Western South Asia stands as the main exception to this coastline rule, likely due to the efficient inland transport of humid air by the summer monsoon together with large-scale irrigation (1525). Tropical forest and oceanic areas generally experience TW no higher than 31° to 32°C, perhaps a consequence of the high evapotranspiration potential and cloud cover, along with the greater instability of the tropical atmosphere. However, more research is needed on the thermodynamic mechanisms that prevent these areas from attaining higher values.

    Steep and statistically significant upward trends in extreme TW frequency (exceedances of 27°, 29°, 31°, and 33°C) and magnitude are present across weather stations globally (Fig. 2). Each frequency trend represents more than a doubling of occurrences of the corresponding threshold between 1979 and 2017. Trends in ERA-Interim are strongly correlated with those of HadISD but are smaller for the highest values (Fig. 2), consistent with ERA-Interim’s underestimation of extreme TW that is largest for the most extreme conditions (fig. S11). We also find a sharp peak in the number of global TW = 27°C and TW = 29°C extremes during the strong El Niño events of 1998 and 2016. Linearly detrending this global-TW-extremes time series reveals that the El Niño–Southern Oscillation (ENSO) correlation is largest for TW values that are high but not unusual (~27° to 28°C) across the tropics and subtropics (fig. S13). Further work is necessary to test to what extent this relationship may be related to the effect of ENSO on hydrological extremes at the global scale, on tropospheric-mean temperatures, or on SSTs in particular basins, and the implications of these effects for TW predictability (2627). Overall, TW extremes in the tropics largely correspond on an interannual basis to mean TW (fig. S14), indicating that climate forcings and modes of internal variability resulting in mean temperature shifts can be expected to modulate tropical TW extremes. This is the case in the subtropics as well, although to a somewhat lesser extent.

    Fig. 2 Global trends in extreme humid heat.

    (A to D) Annual global counts of TW exceedances above the thresholds labeled on the respective panel, from HadISD (black, right axes, with units of station days) and ERA-Interim grid points (gray, left axes, with units of grid-point days). We consider only HadISD stations with at least 50% data availability over 1979–2017. Correlations between the series are annotated in the top left of each panel, and dotted lines highlight linear trends. (E) Annual global maximum TW in ERA-Interim. (F) The line plot shows global mean annual temperature anomalies (relative to 1850–1879) according to HadCRUT4 (40), which we use to approximate each year’s observed warming since preindustrial; circles indicate HadISD station occurrences of TW exceeding 35°C, with radius linearly proportional to global annual count, measured in station days.

    We also observe modulation on a seasonal scale, by considering as an illustrative example the South Asian monsoon region. There, the timing of peak TW varies with the advance of the summer monsoon (15). Splitting South Asia into “early monsoon” and “late monsoon” subregions, we find that the number of TW extremes is largest around the time of the local climatological monsoon onset date (Fig. 3). Although equivalent extreme values of TW are possible before, during, and after the monsoon rains in any given year, they are of a different character; especially in the northern and western parts of the subcontinent, they become continually moister and have lower dry-bulb temperatures as summer progresses. Across the globe, such temperature and humidity variations occur within a well-defined bivariate space (fig. S15). That these variations are systematically associated with the summer monsoon in South Asia emphasizes the important role of moisture, and of weather systems on synoptic to subseasonal time scales, in controlling extreme TW (1528). Our findings underscore the diversity of conditions that can lead to extreme humid heat in the same location at different times, suggesting that impacts adaptation strategies may benefit from taking this recognition into account. Such intraseasonal variability in TW also matters for physiological acclimation, which requires several-day time scales to develop (29); TW character is especially relevant when considering effects on human systems that vary in their sensitivity to humidity and temperature—for example, thermoregulation and energy demand for artificial cooling are strongly affected by TW, whereas the materials that make up the built environment are principally affected by temperature alone (1330).

    Fig. 3 Monsoon-modulated seasonality of extreme humid heat.

    (A) Early monsoon areas (light orange shading; <June 15 average onset date) and late monsoon areas (green shading; ≥June 15 average onset date) in South Asia. (B) (Solid line) Mean annual number of TW exceedances of 31°C per station, by pentad, in the early monsoon areas. (Dashed line) Mean relative humidity associated with these exceedances. The division between the brown- and blue-shaded sections represents the station-weighted-average climatological monsoon onset date. (C) Same as in (B), but for the late monsoon areas.

    While our analysis of weather stations indicates that TW has already been reported as having exceeded 35°C in limited areas for short periods, this has not yet occurred at the regional scale represented by reanalysis data, which is also the approximate scale of model projections of future TW extremes considered in previous studies (1415). To increase the comparability of our station findings with these model projections, we implement a generalized extreme value (GEV) analysis to estimate the amount of global warming from the preindustrial period until TW will regularly exceed 35°C at the global hottest ERA-Interim grid cells, currently all located in the Persian Gulf area (Fig. 4). Complete details of this procedure are in Materials and Methods. In brief, we fit a nonstationary GEV model to the grid cells experiencing the highest TW values, with the GEV location parameter a function of the annual global-mean air-temperature anomaly. This enables us to quantify how much global warming is required for annual maximum TW ≥ 35°C to become at most a 1-in-30-year event at any grid cell. We conduct this analysis solely for grid cells where the nonstationary GEV model is a significantly (P < 0.05) better fit to the annual maximum time series (1979–2017) than a stationary alternative. We then define the temperature of emergence (ToE) as the amount of global warming required until TW ≥35°C is at most a 1-in-30-year event at the ERA-Interim spatiotemporal scale, such that the lowest ToE at any grid cell approximates the first occurrences of TW = 35°C that are widespread and sustained enough to cause serious or fatal health impacts, as estimated from physiological studies (61031).

    Fig. 4 Projections of extreme humid heat exceeding the physiological survivability limit.

    (A) Shading shows the amount of global warming (since preindustrial) until TW = 35°C is projected to become at least a 1-in-30-year event at each grid cell according to a nonstationary GEV model. In blank areas, more than 4°C of warming is necessary. Black dots indicate ERA-Interim grid cells with a maximum TW (1979–2017) in the hottest 0.1% of grid cells worldwide. (B) Total area with TW of at least 35°C, as a function of mean annual temperature change 〈T〉 from the preindustrial period. Red (green) vertical lines highlight the lowest 〈T〉 for which there are nonzero areas over land (sea)—the respective ToE. (C) Bootstrap estimates of the ToE. See text for details of this definition and calculation.

    Our method yields a ToE of 1.3°C over the waters of the Persian Gulf (90% confidence interval, 0.81° to 1.73°C) and of 2.3°C for nearby land grid cells (1.4° to 3.3°C) (Fig. 4). Adjusting these numbers for ERA-Interim’s robust Persian Gulf differences of approximately −3°C for extreme TW (fig. S12) supports the conclusion from the station observations that recent warming has increased exceedances of TW = 35°C, but that this threshold has most likely been achieved on occasion throughout the observational record (Fig. 2). The strong marine influence on these values is also apparent in Fig. 1.

    To further assess the physical realism of our GEV extrapolation, we additionally examine observed annual maximum (monthly mean) SSTs. An atmospheric boundary layer fully equilibrated with the ocean surface would be at saturation and have the same temperature as the underlying SSTs, meaning that, in principle, 35°C is the lowest SST that could sustain the critical 35°C value of TW in the air above. In reality, equilibrium will not be achieved if air-mass residence times over extreme SSTs are too short, which is more likely if the vertical profile of the atmosphere allows strong surface heating to trigger deep convection (10). Current large-scale SSTs and their trends may therefore provide some guidance as to whether our projections of extreme TW are physically plausible. It is in this context that we note monthly mean SSTs exceeding the 35°C threshold for the first time, reaching 35.2°C in the Persian Gulf in 2017 (Fig. 5). As a result, our GEV projection of large-scale maritime TW ≥ 35°C, for less than 1.5°C warming, appears physically consistent with SST observations at the same scale. Analogous corroboration of station-based TW ≥ 35°C events is provided by point scale, hourly SST and TW across the Persian Gulf from an independent database of marine observations (see the Supplementary Materials) (21), in which we find SSTs have exceeded 35°C in every year since 1979, with ~33% of July to September 2017 observations above this threshold. During the summer of 2017, reports of Persian Gulf over-water TW ≥ 35°C also peaked at ~6% of all TW measurements there.

    Fig. 5 Trends and maxima of observed SST.

    (A) Annual maximum of monthly SST across all grid cells in the HadISST dataset; orange dashed line is a running 30-year average, and red line marks 35°C. (B) All-time maximum SST around the Persian Gulf and Arabian Sea. The blue points mark locations where monthly mean SST rose above 35°C in 2017.


    The station-based approach that we take here and the model-based approach taken in previous studies (1416) represent different methods for obtaining valuable perspective on the genesis and characteristics of global TW extremes. The primary strength of station data is its ability to precisely capture local conditions, but even the best-available station data have limitations, uncertainties, and potential unobserved humidity biases (for example, due to observational procedures, instrumentation type, or siting), as well as highly incomplete spatial coverage (see discussion in the Supplementary Materials) (3233). In contrast, reanalysis products and high-resolution regional models satisfy the need for spatiotemporal continuity and consistency and allow analysis of additional variables, but often underestimate extremes (34).

    In this study, we demonstrate that efforts to better understand extreme TW would benefit from further close examination, and improved standardization and integration, of station data to alleviate model shortcomings—especially along coasts where TW can vary markedly over small distances and where high-quality humidity data are therefore essential—but that station-based and physical modeling–based approaches are fundamentally complementary. Further research into the origins of extreme-TW biases in gridded products and continued advances in data assimilation would also help enable the development of a more unified approach drawing on all available sources of knowledge. For instance, it is important to understand the treatment of extreme values in reanalyses, and whether false-positive or false-negative rejections might be taking place, particularly as temperature and humidity distributions shift toward ever-higher values. Key multiscale TW processes necessitating closer comparison between observations and models include coastal upwelling, atmospheric convection, land-atmosphere interactions, and atmospheric variability linked to SSTs (28)—for instance, at the hourly, 1- to 10-km scale. Detailed analyses of individual events could help illuminate the unfolding interactions of processes and provide additional investigative power, such as in tracing and forecasting the rapid increases in humidity, which tend to accompany TW extremes (fig. S5), and in assessing the role of topography and land use/land cover in creating apparent TW hotspots (fig. S4). Studies comparing biases and trends in TW and SSTs among reanalyses, models, and regions would be especially beneficial, as would investigation of the sensitivity of extreme-TW projections to historical variability, changes in forcing patterns, and statistical methodologies.

    Imminent severe humid heat provides incentive for a broad interdisciplinary research initiative to better characterize health impacts. Increased collection of high-resolution health data, international collaborations with public health experts and social scientists, and dedicated modeling projects would aid in answering questions about how vulnerable populations (such as the elderly, outdoor laborers, and those with preexisting health conditions) will be adversely affected as peak TW advances further into the extreme ranges we consider here. Of particular salience is the need to ascertain how acclimation to high-heat-stress conditions is diminished as the physiological survivability limit is approached. Such efforts may also help resolve the reasons for the paucity of reported mortality and morbidity impacts associated with observed near 35°C conditions (1114).

    Our findings indicate that reported occurrences of extreme TW have increased rapidly at weather stations and in reanalysis data over the last four decades and that parts of the subtropics are very close to the 35°C survivability limit, which has likely already been reached over both sea and land. These trends highlight the magnitude of the changes that have taken place as a result of the global warming to date. At the spatial scale of reanalysis, we project that TW will regularly exceed 35°C at land grid points with less than 2.5°C of warming since preindustrial—a level that may be reached in the next several decades (35). According to our weather station analysis, emphasizing land grid points underplays the true risks of extreme TW along coastlines, which tends to occur when marine air masses are advected even slightly onshore (14). The southern Persian Gulf shoreline and northern South Asia are home to millions of people, situating them on the front lines of exposure to TW extremes at the edge of and outside the range of natural variability in which our physiology evolved (36). The deadly heat events already experienced in recent decades are indicative of the continuing trend toward increasingly extreme humid heat, and our findings underline that their diverse, consequential, and growing impacts represent a major societal challenge for the coming decades.


    Weather station observations

    We use HadISD, version, which is produced by the Met Office Hadley Centre as a more rigorously quality-controlled version of the National Climatic Data Center Integrated Surface Database (ISD) (1718). HadISD results from the implementation of additional data availability and quality control procedures to ISD, including checks on both temperature and Td, the two variables required for computing TW. Because of a lack of good-quality data in the tropics, our conclusions are most reliable in the subtropics and midlatitudes, especially where multiple nearby stations are in agreement. TW uncertainties range from ~0.5°C for the most recent data from North America and Europe to ~1.2°C for the oldest data and that from South Asia, Africa, and Latin America. Data validation is considered in depth in the Supplemental Materials.

    We use a MATLAB implementation (37) of the formula of (38) for computing TW. We compute TW daily maxima irrespective of stations’ temporal resolutions, which vary from 1 to 6 hours. TW values are for 2 m above ground level, with station surface pressure calculated from its elevation using a standard atmosphere and an assumed sea-level pressure of 1013 mb. A sensitivity analysis reveals the error in TW owing to this assumption to be on the order of 0.1°C.

    We additionally eliminate HadISD station data that fail any one of the following meteorological and climatological tests. Tests are listed in the order implemented, with the fraction of HadISD 31+°C readings removed at each successive step shown in parentheses:

    1. A TW extreme occurs in conjunction with a dew point depression of ≤0.5°C (65/10,492).

    2. The Td associated with a TW extreme is more than 10°C different from the elevation-adjusted value at the closest grid cell and time step in the ERA-Interim reanalysis (289/10,427).

    3. A TW extreme occurring in 1979–1993 is greater than the maximum in 2003–2017 (67/10,138).

    4. A TW extreme is followed at any point by at least 1000 consecutive days of missing Td data (365/10,071).

    5. A TW extreme occurs on a day when the daily maximum and daily minimum T or Td are identical (53/9706).

    6. A TW extreme is more than 7.5°C higher than any other TW value co-occurring in a 7.5° × 7.5° box centered on the station (405/9653).

    7. A TW extreme is associated with a Td change of more than 8°C in 1 hour or 12°C in 3 hours (77/9248).

    8. A TW extreme is associated with a Td greater than the previously reported, although unofficial, global maximum value of 35°C recorded at Dhahran, Saudi Arabia, on 8 July 2003 (18/9171).

    9. A TW extreme occurs during a period with two or more consecutive identical daily maximum TW and Td values (289/9153).

    10. A TW extreme before 2001 is higher than any value recorded since 2001 (270/8864).

    11. The top five TW extremes at a station all occur within a 365-day period (60/8594).

    12. The Td associated with a TW extreme is higher than the 99.5th percentile of the first 5000 days, only at stations where this value is more than 1°C larger than the 99.9th percentile of the last 5000 days (55/8534).

    13. The Td associated with a TW extreme is higher than the 99.5th percentile of the last 5000 days, only at stations where this value is more than 6°C larger than the 99.9th percentile of the first 5000 days (362/8479).

    14. A TW extreme is associated with a relative humidity of ≥95% (29/8117).

    15. A TW extreme occurs on a day when the daily maximum TW takes place before 11:00 a.m. or after 8:00 p.m. local standard time (26/8088).

    16. A TW extreme is the all-time maximum at a station and is more than 2°C higher than the next largest value (6/8062).

    17. A remaining ≥33°C TW extreme is manually ascertained to be associated with a significant changepoint or not fully supported by gridded humidity and temperature data (508/8056).

    Remaining TW = 35°C readings are also closely examined on a subdaily basis so as to ensure validity to the extent possible. We deem valid all other values that pass the above additional quality control measures, beyond the original quality control and homogenization (1718). Summaries of the TW = 33°C and 35°C values in the final dataset are given in tables S1 and S2.

    Interannual trends are calculated using an ordinary least squares regression, with significance evaluated using a t test on the slope coefficient. Our assessment of extreme TW frequency considers threshold exceedances in 2°C increments from 35° to 27°C, so as to strike a balance between values that are sufficiently distinct from one another while being high enough to remain relevant from an impact perspective.

    Marine observations

    We use monthly SSTs from the 1° HadISST version 1.1 dataset (20) to assess the physical realism of our GEV extrapolations and use in situ point observations of SST and TW from International Comprehensive Ocean-Atmosphere Data Set (ICOADS) (21) as an independent (versus HadISD) check on the extreme TW values reported at nearby land-based weather stations. Details of these comparisons are provided in the Supplementary Materials.

    Marine and vertical profile data

    The ICOADS integrated dataset (21) is used as validation of near-surface conditions over water. Radiosondes are from the Integrated Global Radiosonde Archive (2239).

    GEV modeling of TW extremes in reanalysis data

    We fit a GEV distribution to the time series of annual maximum TW from selected grid cells in ERA-Interim, a reanalysis dataset that optimally blends observations with a numerical hindcast and, thus, provides an estimate of the atmospheric state less sensitive to observation error and microclimatic variability (19). While well suited to identifying and extrapolating global trends, it is inevitable in such an approach that decadal temperature trends and other large-scale variability may affect our results modestly.


    An Ancient Type of El Niño Could Awaken Because of Climate Change

    The drought-ridden Puzhal reservoir on the outskirts of Chennai, India in June 2019
    The drought-ridden Puzhal reservoir on the outskirts of Chennai, India in June 2019
    Photo: Getty Images

    El Niño is one of the most familiar climate patterns on Earth. Pools of water in the eastern tropical Pacific Ocean become abnormal warm, triggering changes in global weather patterns.

    Thanks to the climate crisis, El Niño may have some competition. A new study published in Science Advances on Wednesday shows that as early as mid-century, global warming could cause an ancient climate pattern similar to El Niño in the Indian Ocean to reawaken. It would throw weather further into disarray, particularly in places in the global south that depend on rainfed agriculture.

    The study builds on a previous one published by some of the same authors last year, which found that this climate pattern in the Indian Ocean may have existed during the last Ice Age, 20,000 years ago. Back then, thanks to abrupt global warming driven by natural causes, fluctuating ocean temperatures wreaked havoc on global weather patterns.

    Now, human activities are driving the climate into a similarly unsteady state. To examine how our rising carbon emissions could influence the Indian Ocean, the researchers used climate models of what the rest of the century will look like if world leaders do nothing to curb greenhouse gas emissions (a scenario known as RCP8.5). They found that if current global warming trends continue, we could see huge fluctuations in the Indian Ocean’s surface temperatures by 2050 similar to what happened 20,000 years ago.

    “The Indian Ocean today experiences very slight year-to-year climate swings because the prevailing winds blow gently from west to east, keeping ocean conditions stable,” Pedro Di Nezio, the study’s lead author and a geophysicist at the University of Texas, told Earther in an email. “According to the simulations, global warming could reverse the direction of these winds, destabilizing the ocean and tipping the climate into swings of warming and cooling.”

    Though it’s a separate phenomenon, the possible new pattern would be linked in many ways to El Niño and its opposite counterpart, La Niña. Every three to seven years, temperatures would increase or decrease by up to 2 degrees Celsius (3.6 degrees Fahrenheit), depending on whether it’s an El Niño year or a La Nina year. The changes would last between three and six months.

    Changes of a mere degree or two may not seem like a huge deal. But if this pattern re-emerges, floods, storms, and droughts will become worse and more frequent, especially in Africa, Australia, Indonesia, and Indiaareas already severely impacted by climate change. Warm events could drive droughts over the Horn of Africa and southern India (both of which have already seen grave climate effects) and increased rainfall in Indonesia and northern Australia. Cold events could create opposite effects—for instance, the Indian peninsula could see increased rainfall.

    The effects would be disastrous. A number of these locations rely on rainfed agriculture, and any shifts in precipitation could be disastrous for farmers. Drought conditions in Australia also raise the risk of dangerous bushfires, which the world got a glimpse of earlier this year. The swing between drought and flood in the Horn of Africa created the conditions for massive locust swarms, which are currently threatening food security for tens of thousands of people.

    Malte Stuecker, an Oceanography Professor at the University of Hawaii at Manoa, who didn’t work on the study, said these findings were “robust.” He also noted even the comparatively small temperature variations that already occur in the Indian Ocean have a huge influence on weather patterns in the global south.

    “As Earth continues to warm, these new type of future temperature variations in the Indian Ocean will have much amplified impacts on rainfall across all Indian Ocean rim countries and beyond,” he said.

    It’s not clear exactly what threshold global warming would have to cross to trigger these shifts. But that’s actually disconcerting because the unknowns and tipping point-driven shifts make it harder to plan for the future.

    “The exact magnitude of global warming… at which the first of these El Niño (or La Niña) events will be triggered is hard to know with precision,” said Di Nezio. He said scientists will soon begin research to determine whether or not these changes will occur once we pass 1.5 degrees Celsius (2.7 degrees Fahrenheit) of warming above pre-industrial levels.

    To learn more, Stuecker suggested researchers compare their findings with the latest climate models being used for an upcoming United Nations climate report.

    “These simulations were not available during the time that this paper was written,” he said.

    Though there is much more to learn about the potential of an Indian Ocean El Niño, one thing is clear: The biggest factor in whether or not it will emerge is our actions.

    “The re-emergence will depend strongly on the rate of global warming, so ultimately on whether greenhouse gas emissions are abated or not,” said Di Nezio. “We are certain that the risks of these extreme events is becoming larger and larger as we pump more CO2 into the atmosphere, and certainly going to have an unequal impact on countries in the tropics.”

    Why “Planet of the Humans,” Michael Moore’s new film about green energy, is so controversial

    Planet Of The Humans poster | Michael Moore (Ozzie Zehner/AP Photo/Evan Agostini/Invision/Salon)

    The documentary, directed by Jeff Gibbs and produced by Moore, is streaming free on YouTube now






    MAY 1, 2020 10:00PM (UTC)
    Michael Moore has a long history of releasing documentaries that ask tough questions in challenging times. In fact, as evidenced by films like “Bowling for Columbine” and “Fahrenheit 9/11,” it would be fair to say that his signature move is shaking up the status quo, skewering sacred cows and asking his audience to confront what he calls “the awful truth.”

    Moore is also a trailblazer when it comes to finding creative ways to capture the attention of his audience. He literally revolutionized the documentary form, transforming it from a genre that only intellectuals and schoolkids watched to a mainstay of entertainment media. He also renovated the format of the increasingly popular genre of satirical investigative news with “TV Nation,” which aired on BBC from 1994-1995.

    So, it shouldn’t shock us that in the midst of the coronavirus pandemic he decided to drop a myth-shattering film about the fragile future of human life for free on YouTube. Yet, as with all Michael Moore projects, it turns out that he still offers us a lot of surprises.

    On April 21, Moore presented “Planet of the Humans,” a documentary executive produced by Moore and directed by his longtime collaborator Jeff Gibbs. “Planet of the Humans” is a bold film that argues that human beings are losing the fight to stop climate change because they are following the wrong leaders. Researched for over a decade and originally slated to hit festivals this spring, the film was in a holding pattern due to the pandemic until Moore and Gibbs realized that it had an uncanny timeliness that demanded a creative and immediate release. So, they made it available for free on YouTube.

    Opening with Gibbs in voice over, the films asks: How long do you think we humans have? As it cuts to a series of on-the-street interview replies, most of which are glib or unaware, the pandemic-stricken viewer can’t help but feel an eerie sense of doom.

    “Planet of the Humans” may be Moore’s most provocative project yet, because the film questions the flawed thinking and self-congratulatory activism of the environmentalist left rather than the usual targets of right-wing corruption. It has already sparked controversy, especially among a number of high-profile climate activists like Josh Fox, director of “Gasland,” and Bill McKibben, who comes under tough scrutiny. Critics suggest that some of the data cited in the film is outdated and comes too close to parroting pro-fossil fuel positions.

    But many critiques avoid engaging with the core issues raised in the film — a sign that the film has indeed struck a nerve in the green movement. While Moore has been called on to “retract” the film, there is no sign that there are any plans to do so, especially now that PEN America has written a statement suggesting that pulling the film would be censorship.

    Those of us familiar with Moore’s work know that he refuses to shy away from controversial views if those views ask his audience to rethink paradigms, reassess the status quo, and reframe the narrative.

    Here are five claims from “Planet of the Humans” that challenge widely-accepted narratives about green energy.

    1. Renewable energy is not exactly renewable.

    In one pivotal scene, Ozzie Zehner, author of “Green Illusions” and a producer on the film, claims that much renewable energy relies on “some of the most toxic and industrial processes that we’ve ever created.” Among the examples: solar panels are made from mined quartz and coal rather than sand, electric cars can get much of their power off of the non-renewable energy grid, and that wind power requires a significant amount of fossil-fuel energy.

    There are two core arguments made in the film that suggest that faith in “renewable” energy is more a game of pretend than a real substitute for fossil fuel sources. First, the amount of fossil fuel energy required to produce alternative energy is examined, both in the actual production of renewable energy sources like solar panels, electric cars, and wind turbines, but also in the renewable energy process itself.

    The second argument is that renewable energy itself damages the climate.  Zehner says the public is led to believe that renewable energy is “environmentally benign” and that’s often not true. Biomass energy, which is often touted as a much better choice than fossil fuels, is simply another word for deforestation and burning it releases carbon dioxide into the atmosphereWind energy can lead to mountaintop removalThe construction of solar panels requires the burning of quartz and coal which also releases carbon dioxide into the air. Batteries increase the carbon footprintSolar panels degrade over time and can become a waste management issue. Tesla’s electric cars use lithium, which relies on toxic mining, and aluminum, which uses eight times more energy than steel. Solar arrays require forests to be chopped down and Joshua Trees in the desert to be wiped out.

    The film asks why we have been sold a version of these “renewable” energy sources that hides the real ways that they also hurt the climate. As one climate activist interviewed in the film puts it, “We shouldn’t replace one terrible way of getting energy with another terrible way of getting energy.” While critics might dispute some of the facts and figures in the film, what isn’t being discussed is the fact that most energy consumers don’t realize the complex ways that so-called renewable energy has been developed with a co-dependency on non-renewables.

    2. Many green movement leaders are actually part of a corporate-influenced elite.

    The film features a number of high-profile green energy leaders, among them Bill McKibben, Al Gore, Robert F. Kennedy and the Sierra Club. It then digs into their various networks and sources of support to show how these leaders have been compromised by corporate influence.

    Among those examined is The Sierra Club, which the film argues promotes natural gas and takes contributions from Jeremy Grantham, a titan in timber investments. In another example Gibbs confronts Kennedy on biomass, to which Kennedy replies that the good news about renewables is that you “don’t have to pick a favorite.” When McKibben is asked the same question, he avoids it. In another scene, McKibben sidesteps questions about the sources of his funding. In scene after scene, Gibbs reveals that many of the icons of the green energy movement have ties to the logging industry, fossil fuel companies, and other corporate sponsors who are anything but green in mission. To drive home the point Gibbs underscores a series of sponsors for Earth Day that include, among others, Toyota and Caterpillar.

    When Gibbs makes the rounds at a green energy event, there is only one high-profile green energy activist, Indian environmentalist Vandana Shiva, willing to speak out against biomass and biofuels — the burning of trees and crops for energy.

    At the heart of this critique is the notion that the green movement has become steeped in hypocrisy. For example, Gibbs shows how green energy festivals will often have a prominent display of a solar array, only to hide the reality that they are actually plugged into the fossil fuel grid.

    This all leads Gibbs to ask what these leaders were hiding and why. “What if they had become misguided?” he asks. “What if they have made some kind of deal they shouldn’t have made?” How did green energy leadership transform, the film asks, from those who resisted capitalism to those who collaborated with it?

    3. Corporate capitalism has taken over green energy.

    We’ve heard of greenwashing — efforts by corporations to give a false sense of being environmentally sound — but what “Planet of the Humans” uncovers goes far deeper than that. The film explains that corporate capitalism doesn’t just greenwash; it actually profits from its deep ties to so-called green energy.

    Gibbs drives home the point that much of what drives green energy today is tied to a profit motive: “The only reason we had been force fed the story ‘climate change plus renewables equals we’re saved’ is because billionaires, bankers and corporations profit from it.”

    Depicted in the film are a range of ways The Koch Brothers profit from green energy. For example, the mirrors that were made to support the Ivanpah Solar grid came from a Koch Brothers-owned company. They also build the plants that produce polysilicon for solar cells. According to the film, the Koch Brothers are likely the largest recipient of green energy biomass subsidies in the United States.  In 2013, Business Insider calculated that they received $73.1 million in state and local subsidies. And Yasha Levine tracked $1 billion in subsidies for their biofuels division in 2011 alone.

    As if the Koch Brothers profiting from green energy weren’t disturbing enough, “Planet of the Humans” then runs down the slimy ties between Wall Street and green energy advocates. We see shots of Goldman Sachs execs explaining how to turn forests into profits; we learn that Sierra Club partners with Aspiration Funds, which despite its green projects also includes a number that profit from the destruction of the planet. And we see Al Gore team up with former Goldman Sachs asset manager David Blood, touting the idea that capitalism gives people an incentive to do “their best.”

    McKibben promotes divesting from fossil fuels and investing in green options, like Green Century Funds. But the film reports that less than 1 percent of their stock is invested in solar and wind energy.

    The film argues that even left-leaning, pro-planet activists can become elitist oligarchs shilling for corporate capital. Underscoring that these developments are anything but subtle, Gibbs remarks to viewers that “the takeover of the environmental movement by capitalism is now complete.”

    4. The manufactured faith in renewable energy has distracted us from considering ways to reduce consumption.

    “Planet of the Humans” asks why the environmental movement lost sight of the basic need to reduce human energy consumption as a core mission. If renewable energy is not so renewable after all, then how did it come to dominate energy activism? “The reason why we are not talking about population, consumption, and the suicide of economic growth,” Gibbs says, “is that it would be bad for business, especially for the cancerous form of capitalism that rules the world now hiding under a cover of green.”

    Techno-fixes create an illusion of helping the planet when all they do is help capitalism generate more profit, the film argues. This green illusion, as Zehner puts it, has allowed climate-concerned citizens to think that green energy is a solution. If they support it, they feel “good” and they don’t have to change their patterns of consumption.

    It’s a basic lesson in capitalist ideology: Consumers are led to believe that their consumption doesn’t do any damage. The film argues that this artifice of a “safe” way to get energy has distracted the public from a much-needed conversation about how to reduce the energy demands of the population.

    Gibbs explains that at one point the mantra of climate activism was “reduce, reuse, recycle.” Yet, the idea of reducing and reusing has been sidelined as capitalism wormed its way into the green movement and convinced everyone that renewables were the answer.

    5. Why can’t we talk about constructively about how to reduce human footprint?

    Perhaps one of the most sensitive topics raised in the film is the question of what to do about the rise in population growth and the increase in energy demands. “Planet of the Humans” makes a bold claim — that the only way to take seriously the human toll on the planet is to talk about what humans do to it.

    My colleague, Penn State Anthropology professor Nina Jablonksi, who is interviewed in the film, suggests that “population growth” is the elephant in the room that few climate activists are willing to address. Then she adds that “we have to have our ability to consume reigned in, because we are not good at reigning them if there are seemingly unrestrained resources” or close to it. As long as humans believe that they have unconstrained resources, i.e. that their energy needs can be met in renewable and sustainable ways, they will refuse to limit their consumption demands.

    This line of questioning has been sidelined by leftist environmentalists because it has so often been used to advance fascist and racist agendas. But, the film asks, isn’t it time to try to broach this topic in a way that highlights the fact that the highest energy demands derive from the privileged West? What if the fascism-consumption fallacy has allowed the left to ignore the need to talk about consumption? And, what if, ignoring that conversation allowed climate-concerned citizens to feel like they were doing good things for the planet when they weren’t after all?

    At the heart of the film is the notion that the real “inconvenient truth” that Al Gore once referred to in his iconic environmentalist film is actually more like Moore’s “awful truth”: Maybe we didn’t focus on reducing consumption because we didn’t want to. Maybe it was easier to believe that renewables would give us all the energy we wanted without asking us to change. Or, maybe we didn’t know that renewables weren’t the energy saviors we thought they were. After watching this film, you won’t be able to think about the human toll on the planet in the same way again.

    Clearly “Planet of the Humans” has struck a nerve. In its first week it had been seen over four million times, attacked by calls to have it censored, and lauded as a much-needed intervention into the energy debate.  There is no question that, in the spirit of Moore’s confrontational, provocative, socially committed, progressive style, “Planet of the Humans” is a game-changer designed to spark an intense and meaningful debate over an urgent issue. It may well be that the pandemic has created the ideal context for viewers to consider that the only way to save the planet and to support human life is to change the way we live.




    Sophia A. McClennen is Professor of International Affairs and Comparative Literature at the Pennsylvania State University. She writes on the intersections between culture, politics, and society. Her latest book, co-authored with Remy M. Maisel, is, Is Satire Saving Our Nation? Mockery and American Politics.