Air pollution enhances the negative effect of climate change

The effect of air pollution on human health, the economy and agriculture is radically different depending on where the pollutants are emitted on the planet, a finding that could incentivize some countries to reduce their toxic emissions.

The study, led by the University of Texas at Austin and the University of California, San Diego, and published Friday in Science Advances, was done in collaboration with economists and public health experts from Stanford and Harvard universities.

Aerosols are tiny particles – solid or liquid – emitted by industry, power plants and vehicle exhaust pipes.

Regardless of CO2 in the atmosphere, these toxins can directly affect human health (when inhaled) and climate (they influence temperature, precipitation patterns and the amount of sunlight reaching the earth’s surface).

But while CO2 and aerosols are often emitted at the same time during fuel combustion, these substances behave differently in the atmosphere, explains Geeta Persad of the University at Austin.

“Carbon dioxide has the same impact on the climate regardless of who emits it, but aerosols are concentrated near the place where they are emitted,” says the researcher.

The scientists analyzed eight key regions: Brazil, China, East Africa, Western Europe, India, Indonesia, the United States and South Africa.

The study showed that aerosols can worsen the economic impact of greenhouse gases by up to 66% where they are emitted.

To do the study, the team created a set of climate simulations in which each of the eight regions produced identical aerosol emissions, and mapped how temperature, precipitation and air quality at the surface of the entire planet were affected.

They then linked these data to known relationships between climate and air quality and infant mortality, crop productivity and gross domestic product in the eight regions.

Finally, they compared the total social costs of these aerosol-induced impacts with the social costs of CO2 emitted in each of the eight regions, and produced global maps of the combined effects of both toxicants (aerosols and_CO2).

The result paints a mixed and complicated picture: in Europe, for example, local emissions cause four times more child deaths outside Europe than inside.

But the researchers point out that aerosol emissions are always bad for both the emitter and the planet as a whole.

“Although we might think that aerosols, which cool the climate, have the advantage of counteracting the warming caused by_CO2, when we look at all these effects combined, we found that no region experiences overall local benefits or generates overall global benefits from aerosol emission,” Persad said.

The researchers believe these findings could motivate some countries to reduce their emissions.

For example, the study found that adding aerosol costs to_CO2 costs could double China’s incentive to mitigate emissions, and shifts the impact of local emissions in Europe from “a net local benefit to a net cost.”

The authors also believe the study can help maximize the benefits of current emissions reduction strategies such as those set out in the Paris Climate Agreement, a global compact that states that all countries target the same_CO2 emissions per capita.

The study revealed that this approach does not improve mortality or crop impacts from combined aerosol and_CO2 emissions because it concentrates the reduction in regions that already have a fairly low aerosol impact, such as the United States and Europe.

“By expanding social cost calculations to include the geographically resolved social impacts of co-emitted aerosols, we are demonstrating that the incentive for individual countries to mitigate and collaborate on mitigation is much greater than if we only think about greenhouse gases,” Burney concludes.

Source: Swiss Info