Climate models have predicted extreme weather fluctuations. Can the damage be reversed?

William Brangham:

Scientists have linked extreme weather fluctuations, from heat waves to torrential rains, to climate change, and these extremes are not limited to Europe.

Last month, ground temperatures in the Arctic Circle reached over 100 degrees Fahrenheit. Much of the western United States is suffering from severe drought, which has provided tinder ready for the wildfires that erupted particularly early this year.

And for the first time in recorded history, deforestation and fires in the Amazon, coupled with warmer temperatures, are causing parts of the rainforest to spit out more carbon dioxide than it absorbs. Scientists fear this reversal may be a tipping point, where one of the best ways to store massive amounts of Earth’s carbon is now becoming a carbon emitter.

And now Gavin Schmidt is joining me. He is a climatologist and senior climate advisor to NASA.

Gavin Schmidt, nice to see you again on “NewsHour”.

We see this devastation and flooding in Europe and also here in the United States. The West is cooking with this drought and forest fires. These are the things that climate models have always predicted would happen, right, more and more of these extreme fluctuations.

Director Gavin Schmidt, NASA Goddard Institute for Space Studies: So climate models predicted that the globe as a whole would get warmer and at the same time we would see more heat waves and we would see more intense precipitation and exacerbation of signals of drought, especially in places like the southwest or the Mediterranean region, where you see a lot more demand for evaporation pulling water out of the soil, making droughts caused by a lack of rainfall more severe for the people on the ground.

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The Guardian: Thermal dome burns through climate models | Opinion

The recent incredibly high temperatures in the northwestern United States and Canada were – and are – very frightening. The heat and the fires it caused killed hundreds of people and are believed to have killed a billion sea creatures.

Daily temperature records have been broken by more than 9 degrees Fahrenheit in some places. In Lytton, British Columbia, the heat reached 121 degrees. The forest fires that consumed the city produced their own thunderstorms, as well as thousands of lightning strikes.

An early study shows that human activity has made this thermal dome – in which a high pressure ridge acts as a cover preventing hot air from escaping – at least 150 times more likely. The World Weather Attribution Group of scientists, which uses computer climate models to assess global heating trends and extreme weather conditions, has warned that the heat of two weeks ago exceeded even their worst-case scenarios.

While it has long been recognized that the climate system has thresholds or tipping points beyond which humans risk losing control of what happens, scientists have not hidden their concern that ‘a generally cold part of the Pacific Northwest had been turned into a furnace. A climatologist said that the prospect opened by the thermal dome “takes my breath away.”

The worrying signs of climate change are not limited to North America. Pakistan and Siberia have also seen record temperatures in recent weeks, as have Moscow, Helsinki and Estonia. In Madagascar, the worst drought in 40 years has left one million people facing food shortages. Climate author David Wallace-Wells suggested that current conditions should be seen as harbingers of a “permanent emergency.”

As policymakers struggle to absorb the very serious implications for human societies of current models, it is frankly difficult to accept the suggestion that these models may underestimate the threat. The prospect of the jet stream blocking and weather systems such as tropical storms stop moving in the way we’re used to, carries nightmarish possibilities. And California still has most of its wildfire season ahead.

If there is anything positive to be learned from this new information and reports on the suffering and destruction caused by the heat, perhaps it is that it intensifies the pressure on policymakers to act. On July 7, the Swiss-based Financial Stability Board issued a warning ahead of the G20 meeting in Venice this weekend. He urged finance ministers and central banks to take greater account of far-reaching climate impacts.

The magnitude of these impacts will depend on decisions taken by governments over the coming months and years. So far, the binding commitments to cut carbon emissions needed to avoid temperature rises above 2 degrees Celsius are notable for their absence. With each worrying news about the climate, the stakes ahead of the November Cop26 conference keep growing.

Environmentalists used to shake their heads when very unusual weather conditions were reported in terms that ignored the contribution of climate change. Now, thanks to the science of attribution, the connection is firmly established. To avoid future thermal domes, countries like the United States and Canada must stop pumping so much energy into the climate system.

The Guardian newspaper, London

The Guardian newspaper, London

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North American heatwave broke records

Climatologists have been shocked by recent deadly heat waves in western Canada and the northwestern United States, which have exceeded all global heating forecasts

Climate scientists have warned that the world is already experiencing episodes of extreme heat that are only expected to occur on a much hotter planet.

The extraordinary heat that engulfed northwestern Canada and the United States last week broke temperature records by several degrees, with temperatures exceeding 40 ° C for days and reaching 49.6 ° C in the village of Lytton, Canada.

Soon after, Lytton was destroyed in forest fires. In Western Canada, nearly 500 people are estimated to have died and experts expect the death toll to rise.

Without the influence of man-made climate change, the heat wave would have been “virtually impossible,” according to a rapid attribution analysis by an international team of 27 leading climatologists who have worked tirelessly to publish the study.

Climate change, they found, has made the heat wave at least 150 times more likely to occur – such extreme heat not occurring according to current statistical analyzes.

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The results have prompted scientists to question their understanding of the impact of climate change on heat waves, which could lead to the revision of some climate models.

Friederike Otto, from the Environmental Change Institute at the University of Oxford, one of the study’s authors, said climate science has been “a little complacent” about how it understands sea waves. heat.

The intensity of heat waves is increasing in orders of magnitude not seen for other extreme events, she said. “Heat waves are how climate change is killing us. This is how climate change manifests itself more strongly.

Using computer observations and stimulation, the scientists compared the past climate in the region covering Portland, Seattle and Vancouver with current trends after global warming of around 1.2 ° C since the end of the 19th century.e century.

They found that the temperatures during last week’s event were so extreme that it was difficult to estimate with certainty how rare the event was, but suggested that it amounted to a single event in a thousand. years in the current climate.

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Geert Jan van Oldenborgh of the Royal Netherlands Meteorological, another of the authors, told reporters that the heat wave had shattered previous temperature records of up to 5 ° C – “an extraordinary event”.

“For comparison, here in the Netherlands we were really shocked when the previous record was broken by 1.8 ° C and it’s more than double. “

The heat wave, said Van Oldenborgh, is “both a major disaster and weather event, but also a major scientific challenge to understand what happened.”

He said the state of climate science in 2020 would have shown that the heat wave was “fundamentally impossible” and that more research was needed to understand how it happened and whether such an event could occur in other parts of the world.

“It’s rather shaking that our theoretical picture of heat wave behavior has been shattered so brutally,” he said. “We are much less certain of how the climate [change] affects heat waves than we were two weeks ago.

South Africa Climate advisers call for faster shift away from fossil fuels

The authors of the article identified two possible explanations for the extreme jump in maximum temperatures observed in North America.

The first is ‘really bad luck’ and that, although exaggerated by climate change, it remains a very low probability event. However, in a future world characterized by global warming of 2 ° C, such an extreme heat wave could occur once every 5 to 10 years, according to the study.

Another explanation is that the climate system in this region has crossed a threshold that has increased the likelihood of such extreme heat well beyond the gradual rise in temperature peaks that have been observed so far.

In this scenario, record-breaking heat waves like last week’s event are already more likely to occur than climate models predict – which the team of scientists says needs further investigation.

“This is such an exceptional event that we cannot rule out the possibility that we are facing extreme heat today that we only expected to reach higher levels of global warming,” said Otto.

If this second scenario turns out to be correct, it could lead to the revision of climate models.

If an essential climate process is missing from current climate models, these will “definitely need to be improved,” Van Oldenborgh said.

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Canadian hell: northern heat surpasses worst climate models | Climate crisis

If you had made a list of possible locations for Hell on Earth before this week, the tiny mountain village of Lytton in Canada probably wouldn’t have occurred to you.

Few people outside of British Columbia had heard of this community of 250 people. Those who had it were more likely to view it as bucolic. Nestled at the confluence of rivers in the forested foothills of the Lillooet and Botania mountain ranges, the municipal website boasts: “Lytton is the perfect place for nature lovers to connect with incredible natural beauty and the freedom of the countryside. ‘fresh air.”

Over the past seven days, however, the village has been making headlines around the world for an incredibly prolonged and intense temperature spike that has turned the romance into hell.

US President Joe Biden and Canadian Prime Minister Justin Trudeau have warned worried populations to prepare for more. Shocked climatologists wonder how even the worst-case scenarios failed to predict such furnace conditions so far north.

Johan Rockström, director of the Potsdam Institute for Climate Impact Research, said recent extreme weather anomalies were not represented in global computer models used to project how the world might change with more emissions . The fear is that weather systems will be blocked more frequently due to human emissions. “This is a risk – of a severe regional climate impact triggered by global warming – that we have underestimated so far,” he said.

In Lytton, it was as if time itself had stagnated. Trapped in a vast dome of heat that enveloped western Canada and the northwestern United States, temperatures had no choice but to rise.

In Lytton, the Canadian national heat record was broken Monday, shattered Tuesday, then erased Wednesday when the local monitoring station recorded 49.6 ° C (121 ° F).

After the unbearable heat came the suffocating fire. First the forest burned down, then parts of the city. On Wednesday evening, Mayor Jan Polderman issued the evacuation order. ” It’s horrible. The whole town is on fire, “he said on television.” It took about 15 minutes from the first sign of smoke and, suddenly, fire everywhere. “On Thursday, satellite images showed a fires erupt around the village and a cloud of smoke widening in the area.

Heatwave in Canada: Resident films escape wildfire as flames engulf Lytton village - video
Heatwave in Canada: Resident films escape wildfire as flames engulf Lytton village – video

Police stations and hospitals have reported an increase in the number of heat-related deaths – 486 in British Columbia and dozens more south of the border. The roads twisted as the asphalt spread. At least one city has suffered power cuts.

The psychological, political and economic impacts are harder to quantify, but for many the horror has been accompanied by a sense of astonishment that these northern territories are hotter than the Middle East. David Phillips, the Canadian government’s senior climatologist, summed it up in an interview with CTV. “I mean, it’s just not something that looks Canadian.”

A woman and her cat rest inside a tent at the Oregon Convention Center cooling station in Portland, United States. Photograph: Kathryn Elsesser / AFP / Getty Images

More and more people in more countries feel that their climate belongs to another part of the world. Across the border in Washington state, the maximum heat measured at Olympia and Quillayute was 6 ° C above the previous all-time record, according to the Weather Prediction Center. In Oregon, the city of Salem hit 47C, shattering the previous record of 9C. Several parts of California and Idaho also recorded new highs.

The week before, Northern Europe and Russia also suffocated in an unprecedented heat bubble. June records were broken in Moscow (34.8C), Helsinki (31.7C), Belarus (35.7C) and Estonia (34.6C).

Further east, Siberia experienced an early heat wave that helped reduce the amount of sea ice in the Laptev Sea to an all-time high for the time of year. The city of Oymyakon, Russia, widely considered the coldest inhabited place on earth, was warmer (31.6 ° C) than it ever was in June. This follows an incredibly prolonged heat wave in Siberia last year that lasted for several months.

Carlo Buontempo, director of the Copernicus Climate Change Service, said there was a clear human imprint on this “very abnormal” event. Without emissions from cars, farms and industry, he said, record temperatures in western North America would only be expected once every tens of thousands of years, but the probability increases with the levels of greenhouse gases. “In today’s climate, having an extremely hot June is common and likely to happen twice in three decades. However, an analysis of numerous computer models suggests that by the end of the century, these extreme temperatures are more likely than not. It is estimated that human influence increased the likelihood of a new record several thousand times. “


The rise in temperatures is visible all over the world. Even in the Middle East, temperatures over 50 ° C were once outliers, but parts of Pakistan, India, Australia, the United States and Canada are now regularly approaching or exceeding this mark. .

But the intensity of the heat in the northwestern Americas this year and in Siberia last year took many scientists by surprise and suggested that additional factors could be involved in the northern latitudes.

One theory is that the recent spike in temperature may have been caused not only by global warming, but by the slowing of weather systems that remain stuck in one place for an extended period of time, giving them time to escalate and recede. cause more damage. This was a major factor in the devastation in Texas caused by Hurricane Harvey in 2018, which remained over Houston for several days rather than blowing inland and weakening. The stranded high pressure fronts were also blamed for the scorching heat wave in Europe in 2019.

Experts at the Potsdam Institute and elsewhere believe that the rapid warming of the Arctic and the decline of sea ice are causing the jet stream to move in large meanders, called Rossby resonance waves, trapping weather systems at high and low pressure in one place. for longer.

This theory remains disputed, but Michael Mann, director of the Earth System Science Center at Pennsylvania State University, said this week’s surprisingly fierce heat in Lytton and elsewhere should prompt climatologists to consider additional impacts of the weather. ‘human activity.

“We should take this event very seriously,” he wrote in an email. “You’re warming the planet, you’re going to see an increase in the incidence of extreme heat. Climate models capture this effect very well and predict large increases in heat extremes. But something else is happening with this heat wave, and indeed, with many of the very persistent extreme weather conditions we’ve seen in recent years in the United States, Europe, Asia and elsewhere, where models don’t capture not quite the impact of climate change. “

Whatever interactions to blame, scientists agree that the easiest way to reduce the risk of further temperature shocks is to cut fossil fuel emissions and stop deforestation.

“It seems that this heat wave is still a rare phenomenon in the current climate, but that it remains dependent on our decisions,” he added. Friederike Ottosaid the associate director of the Environmental Change Institute at the University of Oxford. “If the world does not quickly eliminate the use of fossil fuels and other sources of greenhouse gas emissions like deforestation, global temperatures will continue to rise and such deadly heat waves will become even more severe. current. “

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Climate models can predict decadal precipitation v

image: Ensemble mean forecast anomalies averaged over forecast years 2 to 9 for summer precipitation over the Inner Tibetan Plateau. Red line: retrospectives; Blue line: near real-time predictions; Black line: observations. Shadows represent uncertainty.
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Credit: HU Shuai

Summer precipitation on the Tibetan Plateau is highly predictable over multi-year timescales in large ensemble forecasts, according to a research team led by ZHOU Tianjun of the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences.

The study, published in Scientists progress June 9, shows that the predictable summer rainfall signal in the Tibetan Plateau hinterland is significantly underestimated in advanced decadal forecast models.

The predictable signal is so weak that it can be masked by unpredictable noise. “The predictable signal that is too weak comes from the low signal-to-noise ratios in the models compared to the real world,” said ZHOU, corresponding author of the study. “This phenomenon is kind of a deficiency in climate models, but it also prompts us to once again recognize the decadal predictability of prediction models.”

ZHOU is Principal Investigator at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics at IAP. He is also a professor at the University of the Chinese Academy of Sciences.

ZHOU and his team used large assemblies from the Sixth Coupled Model Intercomparison Project (CMIP6) of the Decadal Climate Prediction Project (DCPP), an archive of comprehensive decadal prediction experiments based on various climate models, to eliminate stochastic noise. unpredictable and extract the predictable signal. summer rainfall in the Tibetan plateau.

The researchers produced realistic predictions through a post-processing variance adjustment procedure, indicating that the Tibetan Plateau’s summer precipitation is highly predictable over ten-year time scales.

The Tibetan Plateau has the most glaciers outside of the Arctic and Antarctic. Melt water supplies more than 10 major rivers, including the Yangtze River, the Yellow River and the Ganges. “Our results mean a lot for the management of water resources for about 40% of the world’s population,” ZHOU said.

Based on real-time forecasts, the researchers revealed that the Tibetan Plateau hinterland will become wetter, with a 12.8% increase in rainfall for the period 2020-2027 compared to 1986-2005.

“The government and scientists have recognized the urgent need for effective short-term climate information (2021-2040), but there are large uncertainties in traditional short-term climate projections based on summer rainfall scenarios on the Tibetan Plateau. due to internal variability. in the climate system, ”ZHOU said. “Our results demonstrate that decadal climate prediction systems can be a valuable tool in overcoming the shortcoming of traditional projection uncertainties based on short-term climate change scenarios on the Tibetan Plateau.”


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New Research Finds Climate Models Usually Do It Right

New climate research, conducted primarily in San Diego, reveals that a study of Earth’s temperatures during the last ice age confirms some widely held ideas about climate change.

Lead author Alan Seltzer, a paleoclimatologist at the Wood’s Hole Institute of Oceanography, studied ancient water as a way to better understand never-before-recorded planetary temperatures.

New Research Finds Climate Models Usually Do It Right

Hear this story from Erik Anderson.

New Research Finds Climate Models Usually Do It Right

Working in the oceanography laboratory of the Scripps Institution of Oceanography at Jeffery Severinghaus in La Jolla, Seltzer analyzed the composition of ancient groundwater in San Diego and other places around the world.

“A huge amount of our planet’s land surface, like about a third of our planet’s land surface, contains ancient water that has fallen as rain or entered the subsoil as runoff from the earth. rivers during the last ice age, ”said Seltzer.

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After chemically dating the water using radiocarbon techniques, the researchers measured the amount of rare gases dissolved in the water. They compiled data on all continents except Antarctica.

“Paleo noble gas temperature records are so powerful because they are based on a physical principle and are not influenced much by life – which always complicates everything – or by extreme short-term events,” said co-author Martin Stute, researcher in the Department of Environmental Sciences at Barnard College and Associate Principal Investigator at the Lamont-Doherty Earth Observatory.

This technique allowed researchers to extrapolate the temperature of the planet during the last ice age.

He also confirmed the results that determine ocean temperatures during this period, giving scientists more confidence in models that predict climate change.

“This gives the models a little more confidence in a longer term climate perspective well beyond human observation,” said Seltzer.

Researchers can tell with more confidence what the temperature of the earth will be based on the amount of carbon in the air.

“The most important thing he tells us is that the models are actually on the right track and we can believe the models more than before so that we can believe them,” Severinghaus said.

RELATED: San Diego Supervisors Chart New Course for Climate Action Plan

Previous work seriously underestimated the climate’s sensitivity to greenhouse gases, according to Severinghaus. Climate change could be more destabilizing than current forecasts predict, he said.

“The rather high climate sensitivity that our results suggest is not good news regarding future global warming, which could be stronger than expected using previous best estimates,” said co-author Werner Aeschbach, researcher at the Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany.

“In particular, our overall review strengthens the conclusion from several single rare gas case studies that the tropics were significantly colder during the last ice maximum than today. The unpleasant implication for the future is that the warmer regions of the world are not immune from further warming, ”he said.

The results are published in the current edition of the journal Nature.

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Scientists explain why climate models cannot r

image: Warming rate during the rapid warming period (1975 / 01-1997 / 12) (a) and warming gap period (1998 / 01-2013 / 12) (b) and the change in warming rate during the period of hiatus from the period of rapid warming (c). All warming rates are derived from 28 simulated global temperature time series (bars) and six observed (vertical lines).
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Credit: © Science China Press

A new study led by Dr Wei and Dr Qiao of the First Institute of Oceanography at the Department of Natural Resources provides an assessment of the performance of recently published CMIP6 models to simulate the slowdown in global warming observed in the early 2000s. This study reveals that the key to simulating and predicting short-term temperate change is to separate and properly simulate the two distinct signals i.e. the human-induced long-term warming trend and natural variabilities, in particular those at interannual, interdecadal and multidecadal scales. . This work was published online in SCIENCE CHINA Earth Sciences on April 15, 2021.

After the unprecedented warming during the last quarter of the 20th century, the growth of global surface temperature unexpectedly slowed between 1998 and 2013 despite the sharp increase in greenhouse gas emissions; this phenomenon is called hiatus or slowing down of global warming to be more precise. Slowing global warming challenges existing scientific understanding of the mechanisms of global temperature change, so has been one of the most worrying issues in recent climate research and even the public.

However, the sophisticated and advanced climate models of CMIP5 could not simulate this slowdown in warming. Over the period 1998-2013, the models mainly show a rapid warming surge that deviates considerably from the observed flat temperature time series. The models considerably overestimate the rate of warming observed over the recent period. IPCC AR5 said: “Almost all historical CMIP5 simulations do not reproduce the recent observed warming gap.” As a result, the ability to simulate and predict sophisticated climate models has been called into question.

Now, CMIP6 model data is gradually released since 2020. Newly developed models include a better understanding of the mechanisms of global temperature change, in particular more reasonable physical processes of natural variability. Successful simulations of the global warming slowdown are expected in next-generation models. As data from 28 new models becomes available, there is a need to timely review the ability of CMIP6 models to exhibit the recent slowing of warming.

Against six widely used global surface temperature datasets, the research team at the First Institute of Oceanography at the Department of Natural Resources are evaluating the performance of the 28 newly released CMIP6 models to simulate the recent slowdown in warming and find that the Most CMIP6 models still fail to reproduce. slowing warming, although they show encouraging improvements over the CMIP5 models (Figure 1).

In addition, they explored possible reasons for the difficulty of CMIP6 models in simulating the recent slowdown in warming. They reveal that it is associated with model shortcomings in simulating temperature change signals distinct from the long-term human-induced warming trend and / or the three crucial natural variabilities at interannual, interdecadal and multidecadal scales ( Figure 2).

This study reveals that the key to simulating and predicting short-term temperate change is to separate and properly simulate the two distinct signals, i.e. the human-induced long-term warming trend and variability. natural, in particular those at interannual, interdecadal and multidecadal scales. . This suggests that key-scale variabilities require more attention in models, given their vital roles in modulating the change in the rate of warming at decadal to multi-decadal scales. This result can provide important information for simulating and predicting short-term climate change.


This research was funded by the National Natural Science Foundation of China (No. 41806043 and 41821004).

See the article: Wei M, Shu Q, Song Z, Song Y, Yang X, Guo Y, Li X, Qiao F. 2021. Could CMIP6 climate models reproduce the slowdown in global warming of the early 2000s? Science China Earth Sciences, 64,

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New information on acid formation may help refine atmospheric and climate models

Atmospheric acidity is increasingly established by organic acids, such as formic acid and carbon dioxide. The former contributes to the development of aerosol particles as a precursor to raindrops and thus affects the pH of rainwater and cloud growth..

Diagram of the main emission sectors and primary emissions, meteorological and chemical processes, impacts on air quality and climate, and measurement and analysis tools used to analyze the effects of changes in emissions . Image credit: B. Franco et al, Ubiquitous atmospheric production of organic acids mediated by cloud droplets, Nature, May 2021.

In previous models of the atmospheric chemistry of acid formation, formic acid had played an insignificant role. The chemical processes involved in its formation were not fully understood.

Under the aegis of the Forschungszentrum Jülich, an international research team has now succeeded in filling this gap and decoding the dominant mechanism of the development of formic acid. This further improves atmospheric and climatic models. The results of the study were recently published in the peer-reviewed journal Nature.

The Germans are familiar with acid rain, especially from their experience in the 1980s. The reason for acid rain was that the sulfur oxides and nitrogen oxides released into the air by humans form acid. nitric and sulfuric acid by reacting with water droplets in clouds. The pH of acid rain is around 4.2 to 4.8, which is lower than that of pure rainwater which has a pH of 5.5 to 5.7. Normal acidity is due to the natural carbon dioxide content of the air.

But the chemical process that takes place in most of the formic acid found in the air was not known until now. Dr Bruno Franco and Dr Domenico Taraborrelli from the Jülich Energy and Climate Research Institute – Troposphere have now successfully decoded it: formaldehyde is naturally formed by the photo-oxidation of volatile organic compounds.

Methanediol is formed when formaldehyde reacts in cloud droplets with water molecules. Most of this methanediol is released and then reacts with OH radicals, sometimes called “atmospheric detergents”, to form formic acid by a photochemical process. A smaller part also forms formic acid by reacting with the liquid phase of the water droplets and this acid is dispersed by rain.

According to our calculations, the oxidation of methanediol in the gas phase produces up to four times more formic acid than what is produced in other known chemical processes in the atmosphere..

Domenico Taraborrelli, Energy and Climate Research Institute, Forschungszentrum Jülich

This amount lowers the pH of rainwater and clouds to 0.3, which underlines the contribution of organic carbon to the natural acidity present in the air.

Initially, the two researchers tested their concept using MESSy, a global model of atmospheric chemistry, and compared the results with remote sensing data. To perform the modeling, the team used the Jülich JURECA supercomputer. The results were confirmed by subsequent experiments carried out in the SAPHIR atmosphere simulation chamber at Jülich.

We assume that the demonstrated mechanism is also active in aqueous aerosols and applies to other organic acids such as oxalic acid, which are not sufficiently taken into account in atmospheric chemistry models to date..

Domenico Taraborrelli, Energy and Climate Research Institute, Forschungszentrum Jülich

One of the impacts of this could be a better understanding of aerosol particle growth and cloud formation.

Journal reference:

Franco, B., et al. (2021) Pervasive atmospheric production of organic acids mediated by cloud droplets. Nature.

Source: https://Www.Fz-Juelich.De/

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ECB climate models are built on obsolete scenarios

The author is professor of environmental studies at the University of Colorado

The late Kenneth Arrow, who won the Nobel Prize in Economics in 1972, previously worked as a long-term weather forecaster in the US military. When he realized that this weather forecast was no more accurate than random guesses, Arrow passed the message on to his superiors. “The commanding general is well aware that the forecast is not good,” Arrow was told. “However, he needs it for planning purposes.”

Much like the commanding general of Arrow, the European Central Bank is currently conducting an economy-wide climate stress test. This makes sense because climate change is real and serious. The ECB test, which aims to assess “the exposure of euro zone banks to future climate risks. . . under different climate scenarios ”, is also ambitious and far-reaching. As ECB Vice President Luis de Guindos wrote in March, it looks 30 years away and covers around 4 million companies worldwide and 2,000 banks – “almost all monetary financial institutions in the area euro ”.

Unfortunately, the scenarios on which the ECB relies are obsolete, calling into question the entire exercise. Although somewhat technical, come into the rabbit hole with me on this one as things get interesting quickly.

The ECB and more than 60 other central banks belong to the Network for Greening the Financial System. This volunteer group covers most of the global economy and advocates for climate stress tests to assess financial resilience “to what-if, extreme, but plausible scenarios.” However, these scenarios are accompanied by a health warning, namely: the most commonly used “were designed about 10 years ago and do not correspond well to recent trends in emissions”.

In fact, as my colleagues and I have documented, these scenarios have dramatically overstated carbon dioxide emissions since 2005. Moreover, even the most recent NGFS scenarios are out of step with real world data. This could lead to bad decisions and possibly even higher systemic risks.

The NGFS uses three main scenarios to guide climate assessments. “Orderly” assumes that policy change begins now, leading to net zero emissions by 2070, with emissions reaching 2100 and severe environmental consequences.

The NGFS is clear that compromises are needed to reduce emissions. A carbon tax could accelerate the transition to net zero and promote carbon capture technologies. At the same time, however, it would increase the costs of some raw materials and force companies to review their operations. This could lead to lower short-term growth but much higher long-term growth – the opposite of the greenhouse scenario.

Unfortunately, some of the other assumptions underlying the three NGFS scenarios are implausible.

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For example, they assume global emissions of carbon dioxide from fossil fuels in 2020 of about 36 gigatonnes. Yet in 2020, these emissions were closer to 33 Gt, a gap that is only partly due to the dire economic consequences of the pandemic. By 2040, this little mistake becomes very important. The “greenhouse” scenario predicted around 45 Gt of fossil fuel emissions. Yet even before the commitments made at last month’s climate summit, the International Energy Agency is projecting around 35 Gt of emissions in 2040. The gap widens as you move forward. future. According to a recent analysis in Nature, fossil fuel emissions would be around 25 Gt by 2100, under assumed 2019 policies and technologies. Yet the greenhouse scenario projects 81 Gt, or more than three times that.

Stress tests use “what-if, extreme” scenarios and, as the NGFS clearly shows, these must be “plausible”. Yet it is simply not convincing that the world collectively decides to convert much of its energy supply to coal, which would be necessary for fossil fuel emissions to exceed 80 Gt by 2100.

The ECB uses its climate scenarios in the same way that Arrow General used his ‘bad’ weather forecast – because there is no alternative for planning purposes. Nevertheless, it is urgent to take stock. Because these climate scenarios are usually out of sight and technical, those who rely on them may not know how much they have diverged from the real world. Because they are institutionalized, changing these stress tests will also be difficult.

Nonetheless, if financial institutions are to perform meaningful climate stress tests, it is imperative that they be based on the latest scientific data and not on improbable scenarios.

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Climate models predict sea level soar if Paris targets are exceeded

May 5 (UPI) – If world leaders and policymakers fail to find a way to cut emissions and limit warming to 2 degrees Celsius, the target set by the Paris Agreement, new models suggest that ice losses in Antarctica will cause a dramatic rise in sea level.

According to a study published Wednesday in the journal Nature, current trends in global warming have caused planet Earth to exceed the goals of the Paris Agreement by 2060.

If that happens, the researchers and their models predict that the destabilization of Antarctic ice sheets will ensure an unstoppable sea-level rise of between 17 and 21 centimeters by the end of the century.

To limit the damage caused by climate change, whether it be prolonged droughts or rising waters, scientists generally agree that world leaders should strive to limit warming to 1.5 degrees Celsius above pre-industrial levels – the most ambitious goal set by the Paris Agreement.

However, climatologists believe that policymakers can also ensure a habitable planet by achieving a slightly less aggressive goal and limiting warming to 2 degrees.

But if world leaders can’t find a way to achieve one of the two goals of the Paris Agreement, the scientists said, all bets are off.

For the new study, a team led by researchers at the University of Massachusetts Amhurst examined the likely behavior of Antarctic ice under different warming scenarios.

According to the analysis, if global warming is limited to between 1.5 and 2 degrees, the most recent models of ice loss in Antarctica predict that the southern continent’s ice sheet would contribute between 6 and 11 centimeters to the rise in level. from the sea by 2100.

If global warming approaches 3 degrees above pre-industrial temperatures, models predict that loss of Antarctic ice will contribute 17 to 21 centimeters to sea level rise by the end of the century.

If current warming trends continue, Earth and the Antarctic ice sheet will reach the tipping point of an uncontrolled rise in sea level by 2060.

As significant amounts of ice cap destabilization accumulate as the climate warms, even moderate warming will ensure that Antarctica will continue to experience significant ice loss over the next several centuries.

The latest models suggest that further warming beyond the Paris Agreement targets will ensure seas rise more than 10 meters by 2300.

Conversely, models show that if policymakers can meet the goals of the Paris Agreement, long-term sea level rise can be limited to 1 meter.

Some studies have shown that the Antarctic ice sheet will continue to melt for the next 300 years, even if warming has slowed considerably. But if the warming continues, the melting and rising sea levels will accelerate more dramatically and faster, the researchers say.

Researchers suggest that the source of Antarctica’s vulnerabilities lies along the coast.

As the continent’s coastal glaciers shrink, they become increasingly vulnerable to warm water currents and less able to slow the descent of inland ice.

This pattern of accelerating ice loss has become particularly apparent in Greenland, where warming trends have been more pronounced.

“If the world continues to heat up, the enormous glaciers of Antarctica could start to behave like their smaller counterparts in Greenland, which would be disastrous in terms of sea level rise,” the first author studied. Rob DeConto, Co-Principal of the Amhurst Land School. and sustainability, said in a press release.

Recent studies have shown that melt rates in much of Greenland have accelerated dramatically over the past decades.

One study even showed that Greenland is now losing four times more ice each year than it was almost two decades ago.

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