Robert Allen

China’s success in cleaning up air pollution may have accelerated global warming: Study

tomwt — Thu, 07 Aug 2025 21:19:04 +0000

China’s success in cleaning up air pollution may have accelerated global warming: Study tomwt Thu, 08/07/2025 - 14:19 More CNAS in the Media Sharon Udasin | The Hill July 14, 2025

THE HILL - Efforts to clean up air pollution in China and across East Asia may have inadvertently contributed to a spike in global warming, a new study has found.

The decline in aerosol emissions — which can cool the planet by absorbing sunlight — have added about 0.05 degrees Celsius in warming per decade since 2010, according to the study, published on Monday in Communications Earth & Environment.

At that time, China began implementing aggressive air quality policies and was ultimately able to achieve a 75 percent reduction in emissions rate of toxic sulfur dioxide, the authors noted.

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“Reducing air pollution has clear health benefits, but without also cutting CO₂, you’re removing a layer of protection against climate change,” co-author Robert Allen, a climatology professor at the University of California, Riverside, said in statement.

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Reforestation can’t undo global warming, but it could help, study says

tomwt — Mon, 09 Jun 2025 16:14:12 +0000

Reforestation can’t undo global warming, but it could help, study says tomwt Mon, 06/09/2025 - 09:14 More CNAS in the Media Erin Blakemore | The Washington Post June 08, 2025

THE WASHINGTON POST - Completely reforesting Earth might help cool the planet more than expected but still not enough to offset the warming that has occurred since industrial times, a recent analysis finds.

The scientists modeled what might happen if humans reached the planet’s reforestation potential, adding about 4.6 million square miles of trees and bringing Earth’s forests back to preindustrial levels.

The good news is that trees’ natural emissions could help with cooling, the researchers write in the journal Communications Earth & Environment.

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“Reforestation is not a silver bullet,” Bob Allen, a professor of climatology at the University of California at Riverside and the paper’s lead author, said in a news release. “It’s a powerful strategy, but it has to be paired with serious emissions reductions.”

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Robert Allen

Trees are part of the climate solution - but not the whole answer

tomwt — Tue, 03 Jun 2025 22:25:05 +0000

Trees are part of the climate solution - but not the whole answer tomwt Tue, 06/03/2025 - 15:25 More CNAS in the Media Andrei Ionescu | Earth.com June 03, 2025

EARTH.COM - Replanting the world’s forests could significantly reduce global warming, particularly in tropical regions, according to a new modeling study.

But even if every tree lost since the 19th century were replaced, the cooling impact would still fall short of reversing the full effects of human-caused climate change. Emissions cuts, the authors stress, remain essential.

The study, led by researchers at the University of California, Riverside, shows that restoring global forests to their preindustrial extent could lower average global temperatures by 0.34 degrees Celsius. That’s about one-quarter of the warming the planet has already experienced.

The modeling is based on a hypothetical increase in forest cover of 12 million square kilometers – about 135% the size of the United States. That estimate is roughly equivalent to the widely discussed goal of planting one trillion trees.

Scientists estimate that the Earth has lost nearly half of its trees – about three trillion – since the dawn of industrial society.

“Reforestation is not a silver bullet,” said Robert Allen, a climate scientist at UC Riverside and the study’s lead author. “It’s a powerful strategy, but it has to be paired with serious emissions reductions.”

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How cleaning up shipping cut pollution — and warmed the planet

tomwt — Thu, 18 Jul 2024 22:07:12 +0000

How cleaning up shipping cut pollution — and warmed the planet tomwt Thu, 07/18/2024 - 15:07 More CNAS in the Media Syris Valentine | Grist July 18, 2024

GRIST - Michael Diamond thought he’d have to wait until this year, at least, to have enough data to understand how a shipping regulation aimed at curbing pollution affected the clouds that deck the ocean. “They’re so variable. They’re so wispy. They’re so ever, ever changing,” he said. “So you really often need a lot of observations to get at what they’re doing.”

Nonetheless, just three years after the international maritime community slashed sulfur emissions in 2020, the cloud physicist with Florida State University published an award-winning paper studying clouds along a shipping lane in the southeast Atlantic. By analyzing satellite data from before and after the regulation took effect, Diamond demonstrated that the clouds had dimmed. In other words, even as it cleaned its emissions, the global shipping sector made marine clouds a little less bright.

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“I think there’s going to be a lot of papers on the shipping emission reductions,” said Robert Allen, a climate scientist from University of California Riverside with expertise in aerosols. “I don’t think they’re all necessarily going to be arguing the same thing.”

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Coming to grips with a climate paradox: Less air pollution spurs more wildfires

tomwt — Tue, 11 Jun 2024 15:53:56 +0000

Coming to grips with a climate paradox: Less air pollution spurs more wildfires tomwt Tue, 06/11/2024 - 08:53 More CNAS in the Media Warren Cornwall | Anthropocene June 05, 2024

ANTHROPOCENE - It’s hard to fathom that there’s an upside to air pollution. But it’s becoming clear that, paradoxically, cleaning up tailpipes and smokestacks comes with a price for the planet.

As pollution controls cut emissions of aerosols such as sulfur dioxide, scientists are uncovering the myriad ways these tiny, sunlight-reflecting particles have been taking some of the sting out of global warming.

Cuts in aerosol pollution have been linked to increased hurricanes in the North Atlantic, a spate of devastating underwater heatwaves in the North Pacific, and nearly half of the global rise in heat driving global warming over the first two decades of the 2000s.

Now, add to the list the increasing flammability of the world’s largest forest biome. “Cleaning up the air, which is something we all want to do, will accelerate global warming and also impact wildfires,” warned Robert Allen, a climate scientist at the University of California Riverside.

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Reducing aerosol pollution causes more wildfires in an ironic twist of fate

tomwt — Tue, 04 Jun 2024 22:34:26 +0000

Reducing aerosol pollution causes more wildfires in an ironic twist of fate tomwt Tue, 06/04/2024 - 15:34 More CNAS in the Media Sanjana Gajbhiye | Earth.com June 04, 2024

EARTH.COM - The quest for cleaner air is a noble, shared aspiration for a healthier planet and happier lungs. But what if this pursuit to improve air quality by reducing aerosol pollution, however well-intentioned, inadvertently fuels a different kind of environmental disaster?

A study from the University of California, Riverside (UCR) reveals a startling paradox: reducing air pollution could lead to an increase in forest fires, particularly in the vast boreal forests of the northern hemisphere.

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Eliminating this common pollutant could actually lead to more forest fires

tomwt — Fri, 31 May 2024 17:51:36 +0000

Eliminating this common pollutant could actually lead to more forest fires tomwt Fri, 05/31/2024 - 10:51 More CNAS in the Media Lauren Leffer | Inverse May 30, 2024

INVERSE - Nobody likes smog. Aerosol pollution, a mucky particulate cocktail of soot, dust, chemical fumes, and other compounds that linger in the atmosphere, is a worldwide problem. It’s unsightly, triggers environmental harms like acid rain, and is terrible for the health of humans and wildlife alike. Scientists and environmental advocates generally agree: We want cleaner air. But a new study suggests we should be careful about what we wish for, or at least mindful of the route we take to get there.

Reducing aerosol pollution, without simultaneously cutting back on greenhouse gas emissions, could lead to more and worse wildfires across the Northern Hemisphere, according to research published May 29 in the journal Science Advances. Using an intricate climate model, the study researchers found that imposing strict air quality standards, while continuing to pump out carbon dioxide and methane, could significantly boost boreal fire activity in Canada, Russia, Alaska, and parts of Europe. And, in fact, reductions in aerosol pollution could end up being a bigger driver of these northern fires than a continued increase in greenhouse gasses.

“Cleaning up the air, which is something we all want to do, will accelerate global warming and also impact wildfires unless we also reduce emissions of greenhouse gasses like methane and carbon dioxide,” said Robert Allen, lead study researcher and a climatologist at the University of California, Riverside, in a press release.

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