Study finds decline in aerosol levels could be driving heatwaves more than greenhouse gas emissions

New Delhi, Jul 17 (PTI) Declining levels of aerosols -- particles that make up smog and air pollution -- could be making heatwaves more common compared to greenhouse gas emissions, especially in populated areas of the world, according to a study.

Aerosols, which are being studied for their role in global warming -- the particles can cause a cooling effect by reflecting sunlight back into space -- can also produce a warming effect by absorbing solar radiation and influencing cloud formation.

Researchers, led by those at The University of Texas, US, said that recent studies have linked the lowering of aerosols with rising regional temperatures.

However, the study, published in the journal Environmental Research Letters, is the first to look at how aerosols can impact the frequency of heatwaves.

The average number of heatwave days globally could rise from 40 per year to about 110 per year by 2080, with regions in sub-Saharan Africa, South Asia, South America and Western Europe projected to be hit particularly hard, the team said.

"We knew that aerosol emissions were suppressing global warming at the regional level, but the impact of that same suppression on heatwaves near urban centres was much greater than we expected," co-author Cameron Cummins, a computational geoscientist in the department of Earth and planetary sciences at The University of Texas, said. "So, as cities seek to curb their aerosol emissions to improve public health, they will also likely experience more heatwaves," Cummins said.

Using global climate models, the researchers found that aerosols could be up to 2.5 times more influential in driving heatwave frequency in populated areas of the world, compared to greenhouse gas emissions.

An analysis of data since 1920 suggests that higher aerosol levels helped suppress the occurrence of heatwaves in populated areas by about half, the team said.

However, the trend is now reversing in part due to clean air policies targeted at addressing aerosols, which are known to negatively affect public health by harming the heart and lungs, they said.

"Our results show that increased aerosol emissions since 1920 have suppressed heatwave frequency over populated regions by roughly half through present-day -- a trend that is now reversing with shifting emission patterns and net global declining emissions," the authors wrote.

Lead researcher Geeta Persad, an assistant professor at the University of Texas's school of geosciences, explained that even as countries reduce aerosol emissions, impacts are often evident in a matter of years.

Populated areas -- which release the most aerosols -- are particularly at risk for accelerating heatwaves driven by a decline in aerosols in the near future, she said.

"Aerosols are really good at counteracting exposure [to heatwaves] right now, but that could rapidly change in the future," she said.

She cautioned that the study's results should not be taken as a license to pollute, and instead signal cities to prepare for a warmer future with a higher risk of heatwaves. PTI KRS KRS MPL MPL