Climate’s ‘Catch-22’: Cutting air pollution heats up the planet — more confusion ahead?

Chinese smog
[image credit: BBC]

A choice between overheating and lung damage doesn’t appeal much, giving would-be climate controllers a new conundrum for their models to grapple with. Another excuse to wheel out catastrophe fears again.
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Air pollution, a global scourge that kills millions of people a year, is shielding us from the full force of the sun, says Euractiv.

Getting rid of it will accelerate climate change. That’s the unpalatable conclusion reached by scientists poring over the results of China’s decade-long and highly effective “war on pollution”, according to six leading climate experts.

The drive to banish pollution, caused mainly by sulphur dioxide (SO2) spewed from coal plants, has cut SO2 emissions by close to 90% and saved hundreds of thousands of lives, Chinese official data and health studies show.

Yet stripped of its toxic shield, which scatters and reflects solar radiation, China’s average temperatures have gone up by 0.7 degrees Celsius since 2014, triggering fiercer heatwaves, according to a Reuters review of meteorological data and the scientists interviewed.

“It’s this Catch-22,” said Patricia Quinn, an atmospheric chemist at the US National Oceanic and Atmospheric Administration (NOAA), speaking about cleaning up sulphur pollution globally. “We want to clean up our air for air quality purposes but, by doing that, we’re increasing warming.”

The removal of the air pollution – a term scientists call “unmasking” – may have had a greater effect on temperatures in some industrial Chinese cities over the last decade than the warming from greenhouse gases themselves, the scientists said. [Talkshop comment – no mention of urban heat island effects].

Other highly polluted parts of the world, such as India and the Middle East, would see similar jumps in warming if they follow China’s lead in cleaning the skies of sulphur dioxide and the polluting aerosols it forms, the experts warned.

They said efforts to improve air quality could actually push the world into catastrophic warming scenarios and irreversible impacts.

Full article here.
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From a Phys.org preview of the new Hansen et al climate paper:

Aerosols
The authors also conclude that much of the expected greenhouse gas warming in the past century has been offset by the cooling effect of human-made aerosols—fine airborne particles. Aerosols have declined in amount since 2010 as a result of reduced air pollution in China and global restrictions on aerosol emissions from ships. This aerosol reduction is good for human health, as particulate air pollution kills several million people per year and adversely affects the health of many more people.

However, aerosol reduction is now beginning to unmask greenhouse gas warming that had been hidden by aerosol cooling. The authors have long termed the aerosol cooling a “Faustian bargain” because, as humanity eventually reduces air pollution, payment in the form of increased warming comes due.

This new paper predicts that a post-2010 acceleration of global warming will soon be apparent above the level of natural climate variability. The 1970-2010 global warming rate of 0.18°C per decade is predicted to increase to at least 0.27°C per decade during the few decades after 2010. As a result, the 1.5°C global warming level will be passed this decade and the 2°C level will be passed within the following two decades.
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