Ran Feng brings new light to global dimming—Aerosol effect on climate—Radio Ecoshock 2019-10-02
Channel: Stop Fossil Fuels
Date: 21/05/2020

Last week I asked French scientist Olivier Boucher (https://youtu.be/s2PiFdMNmL4) about the climate impacts of aerosols, the smog particles we launch into the atmosphere as we burn fossil fuels. He said that is hard to model. But new science finds another way by comparing the atmosphere now to a period around 3 million years ago when the continents were the same  and so were the CO2 levels. The results are astounding. This is hard science. If you listen to the Ran Feng interview, I promise climate news you have not heard before, and another kick to get us all going into rapid climate action.

The Arctic has become incredibly hot. In 2019, Alaska roasted. Wildfires were rampant in Siberia, and Greenland shed vast amounts of meltwater. Of course our carbon burning is the driving force. But scientists are studying another surprising source behind Arctic warming: our need for cleaner air to breathe. All this leads to a key question about our common future: how much heating has been masked, hidden and delayed by smog shading out incoming sunlight? What happens if pollution is reduced as politicians promise? Are we in for a rude surprise warming?

Underlying that are more questions, like what is “clean air” really? and why did the Arctic Sea become ice-free in an earlier age, even when conditions are like ours now? Is a Blue Ocean event in the Arctic possible as air pollution regulations kick in?

Ran Feng is an assistant professor with the University of Connecticut. Her new paper studies a period about 3 million years ago—when a climate shift created the savannas where our first ancestors evolved. That climate past may be our future.

Show by Radio Ecoshock, reposted under CC License. Episode details at https://www.ecoshock.org/2019/09/7-degrees-c-by-2100-possible-new-science.html

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DID EUROPE’S AIR CLEANUP ADD TO ARCTIC WARMING?
In 2016 and 2017, scientists at Stockholm University—led by Juan C. Acosta Navarro—showed that a significant fraction of Arctic warming has developed since sulfur emissions peaked back in the 1980’s. I ask Ran Feng to explain the relationship between smog reduction in the Northern Hemisphere and a hotter Arctic. The Navarro-led paper “Amplification of Arctic warming by past air pollution reductions in Europe“ says:

“Here we present simulations with an Earth system model with comprehensive aerosol physics and chemistry that show that the sulfate aerosol reductions in Europe since 1980 can potentially explain a significant fraction of Arctic warming over that period.”

Navarro and his team also showed global mean temperature would go up anywhere from 1/3 of a degree to almost 1 degree if air pollution is reduced. That suggests Earth would already be much hotter without smog shielding out some of the sun.

Ran Feng says “it seems like in the intermediate scenario, the radiative cooling effect due to the effect on clouds could be around -.5 or a little bit more than -.5 watts per meter squared which is something around 30 ppm CO2 equivalent“. And if that is the “intermediate scenario” is there a worse case scenario than that?

According to her team’s research into the climate around 3 million years ago, not with models but with biochemical proxies and other data, increased clouds from modern aerosols could be masking more than half the heating we have really created with our greenhouse gases! If true, clearing up the air (to end the premature death of millions of humans) could lead to an unexpected climate catastrophe.

A paper in progress makes the case that a reduction in Asian pollution (due mainly to government action against smog)—may be a direct cause of the recent burst of heating in the last three years, including this year with the hottest July ever. Other scientists disagree with that estimate, so we will see.

Feng’s latest paper, “Contributions of aerosol-cloud interactions to mid-Piacenzian seasonally sea ice-free Arctic“, investigates a time around 3 million years ago, “the mid-Piacenzian period“.

The Swedish team led by Navarro found that Europe’s reduction of air pollution may have warmed the Arctic by half a degree. That is because, as Ran Feng’s research shows, we were looking at pollution the wrong way. It is true smog, especially sulfates from burning coal, oil and gas, bounces a fraction of solar radiation back into space, cooling the planet perhaps half a degree. But the real is because aerosol particles trigger more clouds that cool the Earth even more. The masking effect of global dimming is much greater than we thought, hiding perhaps half of the true warming that will be revealed as various countries clean up the air to save millions of people from premature deaths. That is the awful position we are in.