Climate Change > Air Pollution and Global Warming - New Study Surprises

 

New climate study revisits link between air pollution in East Asia and global warming

Scientist Bjorn Samset says discovery that clean-up may contribute to warming shows intricate nature of climate change and dynamics at play

Over the past decade, clean-up efforts in East Asia have reduced air pollution significantly, improving quality of life and health in the region. But they may also have inadvertently contributed to speeding up global warming, by removing particles that helped to cool the Earth.

Pollutants are made up of aerosols, liquid and solid particles suspended in the air. Although their removal is good for public health, this can lead to less cloud and less ground protection from the sun, and may have altered global climate and weather patterns – although how to quantify the impact is an ongoing debate among scientists.

An independent climate study published in Communications Earth & Environment journal on July 14 said it might have found a potential correlation between the two, going by the falling levels of air pollution in East Asia over the past decade.

“Polluted air may have been masking the full effects of global warming”, said Bjorn Samset, a senior researcher in climate and atmospheric sciences at the Centre for International Climate and Environmental Research in Oslo and a contributing author to the study.

The East Asian region – which includes China, Japan, North and South Korea and Mongolia – has undertaken major efforts to cut air pollution over the past decade. In China especially, efforts to reduce the emission of sulphur dioxide have brought about the world’s most significant improvements to air quality.

The amount of sulphur dioxide polluting the air in East Asia has fallen by an estimated 75 per cent since 2013, according to the study.

The researchers found that emission reduction in East Asia was likely to have contributed up to 0.05 degrees Celsius (0.09 degrees Fahrenheit) of the observed 0.06 degree per decade average rate of global surface warming since 2010.

Global warming has accelerated since 2010, rising about 1.1 degrees above pre-industrial levels, a direct result of human activities, primarily the burning of fossil fuels.

At least, that's the theory! But if the numbers above are correct - 0.06 deg. C per decade, then the planet should warm about 0.45 deg. C by the end of the century.

Is that really something to get hysterical about? Less than half of one degree in 75 years!

“East Asian aerosol clean-up is thus likely a key contributor to recent global warming acceleration and to Pacific warming trends,” the study said.

Samset said that before the study, the researchers did not anticipate how neatly the observed drop in aerosol levels would fit with the acceleration of warming. Their discovery showed the intricate nature of climate change, and how many dynamics were at play.

“It’s quite a complex picture to try and disentangle,” he said.

According to the Chinese Academy of Sciences (CAS), the reduction of aerosols in China is a crucial part of the global improvement in air quality, and the weakening of the “umbrella effect” has rendered the previously masked greenhouse effect more apparent.

“We must recognise that the primary reason global warming has become so severe is the substantial increase in greenhouse gases worldwide, not the reduction of aerosols”, CAS said in an article posted to its social media account on Tuesday.

Responding to the research paper, it said: “The significance of the study is not to criticise the efforts of developing countries in improving air quality, but to provide an opportunity for us to gain a deeper understanding of the current global warming issue.”

Study leader Samset similarly said the reduction in pollutants was not the problem.

“No one has ever criticised anyone for cleaning up air pollution,” he said. “This is an unavoidable side effect of doing what, in principle, we should have done all along, which is: not emit pollution.”

Although this temperature increase appears minute, Jimmy Fung, a professor in the division of environment and sustainability at the Hong Kong University of Science and Technology, said that with every 1-degree Celsius increase in temperature, the Earth’s atmosphere held an extra 7 per cent of moisture, which could alter global rain and weather patterns.

Floods in the fall of 2021 from devastating rainfalls in British Columbia were attributed to global warming. But satellite photos from that 'atmospheric river' reveal it's 'headwaters' were over China. It happened that a few weeks before, China reopened dozens of coal-fired plants to end rolling blackouts as the country began recovering from Covid's slowdown of their economy.

IMHO, the record rainfalls in British Columbia came not from global warming, but from the unprecedented air pollution in China, mostly from increased coal burning, combined with La Nina.

“When the pattern slightly changes, those places that used to have rain may not have rain, and the places that used to not have rain will have rain,” Fung said, pointing to more recent extreme weather events.

“Because we are cleaning up the air more, we should pay more attention to cutting our [carbon dioxide] even more aggressively,” he added, referring to the key greenhouse gas.

According to the study, the impact of further emission reductions in East Asia on global warming rates “is likely to be less significant,” since total emissions have already been substantially reduced and the pace of emission decline is expected to slow.

The East Asian region has undertaken major efforts to cut air pollution over the past decade. Photo: VCG via Getty Images

Samset said the effect of aerosol emissions in Europe, India, China and Africa was different to each other, relative to their distinct features.

“Global temperature is more sensitive to air pollution from East Asia than air pollution from South Asia,” he said.

This was explained by the directions in which aerosols travelled. From East Asia, wind currents carry aerosols to the Pacific Ocean where there is substantial cloud cover. There, they increase already high levels of moisture in the air, leading to more rainfall and harsher weather patterns.

Air pollutants from India, however, travel towards the Persian Gulf and Horn of Africa, where their cooling effect has much less impact.

Samset said that although India still had more air pollution, its efforts to reduce this would not substantially affect global temperatures.

Cleaner air across the globe remained a clear priority, he asserted.

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