Climate-Changing Aerosols a Looming Threat, Scientists Say

Scientists argue that COP27 should have prioritised addressing the harmful effects of aerosol changes on vulnerable regions after climate policymakers agreed to a landmark agreement to help these areas.

The team of researchers, led by Dr Laura Wilcox of the University of Reading and the National Centre for Atmospheric Science, write in the journal Nature that the regional impacts of aerosol pollution must be included in future strategies to prevent and adapt to the effects of climate change.

Dr Wilcox said: “Aerosols, and their climate effects, are complex to model, and many of the tools we use to produce policy-relevant information from our simulations don’t consider them.

“They are typically treated as a simple offset to greenhouse gases, but there are many cases of regional climate change where aerosol changes have been the main cause.

“Aerosol emissions are likely to change rapidly over the next couple of decades, so by not fully accounting for the effects of aerosols, we might underestimate the rate and magnitude of change in regions that are particularly vulnerable to aerosol changes.

“Huge progress was made in supporting vulnerable regions to deal with climate change at COP27, but world leaders also need to consider how aerosol changes will harm these same areas.”

Aerosols are made up of soot and other air pollutants from industry and fires. They play a big role in extreme weather events like flooding, but because of how complicated their effects are on global warming and regional weather patterns, they are often left out of climate risk assessments for the next few years and decades.

Scientists say that changes in aerosol concentrations could have made the severe floods in Pakistan in June 2022 even worse. This is because aerosols have a significant impact on monsoon rains. Despite this, the role of aerosols in the floods that killed 1,600 people was not taken into account in early attribution studies.

In the past, some of the short-term effects of global warming were lessened by aerosols in the atmosphere, which sent some of the sun's heat back into space. This has covered up some of the effects of rising greenhouse gas levels, but only for a short time since most aerosols fall back to earth in a few days or weeks while carbon dioxide stays in the atmosphere for hundreds of years.

By lowering the concentration of aerosols in the air over the next few decades, often to protect public health from the bad effects of air pollution, more vulnerable parts of the world will be at risk of sudden changes in extreme heat and floods.

At COP27, policymakers made headway on plans to protect vulnerable regions from greenhouse gas effects, but aerosols' near-future implications were almost completely overlooked.

Aerosols were mostly made in industrialised areas of North America and Europe for most of the 20th century. However, since many heavy industries have moved to Asia, most of the world's emissions now come from India and China.

Aerosols are to blame for poor air quality in many of the world's most densely populated areas, but they also have a huge cooling effect on the Earth's surface by reflecting sunlight and changing the way clouds work. Without them, today's global warming would be up to 50% greater.

Reducing emissions of aerosols due to air quality concerns leads to more extremely hot days and strongly affects the likelihood of extreme precipitation events in the short term.

Aerosol levels are expected to change over the next few decades, according to scientists. Climate change caused by aerosols could be as big in the next 30 years as it has been in the last 170 years. This would mean more extreme weather events all over the world, but especially in areas with a lot of people, like Southeast Asia and West Africa. Environmental Research Letters published a study in 2020 that showed that reducing global aerosols made future increases in extreme heat over Europe and China by up to 40%.

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Source: University of Reading

Account for aerosols in climate risk assessments is published in Nature