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Air pollution will increase dramatically in a hotter climate

Although it is a widespread belief that humans contribute the most to air pollution, there are also vast amounts of pollutants emerging from natural sources. According to a new study led by the University of California, Riverside (UCR), if global temperatures rise by four degrees Celsius above pre-industrial levels, harmful plant emissions and dust will also increase by as much as 14 percent.

“We are not looking at human emissions of air pollution, because we can change what we emit,” said study lead author James Gomez, a doctoral student in Global Climate and Environmental Change at UCR. “We can switch to electric cars. But that may not change air pollution from plants or dust.”

Plants constantly produce and emit chemicals called biogenic volatile compounds (BVOCs), which give rise, for instance, to the smell of a freshly-mowed lawn or the sweetness of ripe strawberries. While on their own, BVOCs are benign, once they react with oxygen, they produce organic aerosols which, when inhaled, can lead to infant mortality and childhood asthma, as well as lung cancer and heart disease in adulthood.

Two factors projected to continue to increase due to climate – atmospheric carbon dioxide and temperature – will both boost BVOC production. However, as the scientists stress, growing plants can still help the environment by reducing the levels of CO2 in the atmosphere. Moreover, BVOCs from small gardens will not be harmful.

“Your lawn, for example, won’t produce enough BVOCs to make you sick. It’s the large-scale increase in carbon dioxide that contributes to the biosphere increasing BVOCs, and then organic aerosols,” Gomez explained.

The second largest contributor to pollution from natural sources will likely be dust from the Saharan desert which, as the climate warms, will be blown around the globe, leading to hazardous amounts of air pollution in Africa, the eastern U.S., and the Caribbean. Moreover, due to West African monsoons, dust over Northern Africa is likely to further increase.

Since they have a diameter of 2.5 micrometers or less, both organic aerosols and dust fall into the category of PM2.5 airborne pollutants, which are among the most dangerous pollutants. According to the experts, the increase in naturally sourced PM2.5 pollution is directly proportional with rises in CO2 levels. “The more we increase CO2, the more PM2.5 we see being put into the atmosphere, and the inverse is also true. The more we reduce, the better the air quality gets,” Gomez said. Thus, in order to have a positive effect on future air quality, CO2 emissions will need to decrease sharply.

“The results of this experiment may even be a bit conservative because we did not include climate-dependent changes in wildfire emissions as a factor. In the future, make sure you get an air purifier,” he concluded.

The study is published in the journal Nature Communications Earth & Environment.

By Andrei Ionescu, Staff Writer

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