According to a new study, the effects of air pollution on people’s health, economies, and agriculture vary a lot depending on where on the planet the pollutants are released. This could give some countries a reason to cut their emissions that change the climate. The study, published in Science Advances on September 23 and led by the University of Texas at Austin and the University of California, San Diego, is the first to simulate how aerosol pollution affects climate and air quality for locations around the world. Aerosols are minute solid particles and liquid droplets emitted by industrial factories, power plants, and vehicle tailpipes that contribute to smog. Compared to carbon dioxide (CO2) emissions, which are the primary focus of efforts to mitigate climate change, they have unique global effects on human health and agricultural and economic productivity.
Even though CO2 and aerosols are often released at the same time when fuel is burned, Geeta Persad, an assistant professor at the UT Austin Jackson School of Geosciences and co-author of the study, says that the two substances behave differently in the Earth’s atmosphere.
Persad stated, “Carbon dioxide has the same effect on the climate regardless of who emits it.” However, aerosol pollutants tend to remain concentrated close to where they’re emitted, so their impact on the climate system is highly variable and highly dependent on where they’re coming from.
Aerosols, depending on where they are emitted, can increase the social cost of carbon—an estimate of the economic costs greenhouse gases have on society—by as much as 66%, according to the findings of the researchers. The researchers looked at Brazil, China, East Africa, Western Europe, India, Indonesia, South Africa, the United States, and the United States.
Jennifer Burney, co-lead author and holder of the Marshall Saunders Chancellor’s Endowed Chair in Global Climate Policy and Research at the UC San Diego School of Global Policy and Strategy, stated, “This research demonstrates how the harmful effects of our emissions are generally underappreciated.” CO2 is a part of global warming, but it is also released along with a number of other compounds that have direct effects on people and plants and also change the climate.
Persad and Burney, who are physical scientists, collaborated with a group of economists and public health professionals on this project, which was funded by the National Science Foundation. Marshall Burke, Eran Bendavid, and Sam Heft-Neal from Stanford University and Jonathan Proctor from Harvard University are co-authors.
Independent of CO2, aerosols can have a direct impact on both human health and the climate. They have negative health effects when inhaled and can affect the climate by altering temperature, precipitation patterns, and the amount of sunlight that reaches the Earth’s surface.
The team created a series of climate simulations using the Community Earth System Model version 1 developed by the National Center for Atmospheric Research in order to examine the influence of aerosols relative to CO2. They ran simulations in which each of the eight regions produced identical aerosol emissions and mapped the resulting effects on global temperature, precipitation, and surface air quality. The researchers then correlated this information with known relationships between climate and air quality and infant mortality, crop yield, and gross domestic product across eight regions. In a final step, they compared the total societal costs of these aerosol-driven impacts to the total societal costs of the co-emitted CO2 in each of the eight regions and generated global maps of the combined effects of aerosols and CO2. According to the researchers, previous research either only looked at the effects of aerosols on air quality or didn’t look at their different effects on the global climate.
The outcome paints a complex and diverse picture. Some regions’ aerosol emissions produce climate and air quality effects that are two to ten times stronger than those of other regions, as well as social costs that sometimes affect neighboring regions more than the source region. In Europe, local pollution kills four times as many babies outside of Europe as it does in Europe.
However, according to the researchers, aerosol emissions are always detrimental to both the emitter and the planet as a whole.
Although we may consider aerosols, which cool the climate, to have the silver lining of counteracting CO2-driven warming, when we consider all of these effects together, we find that no region experiences overall local benefits or generates overall global benefits by emitting aerosols,” said Persad.
The findings, according to the researchers, create potential new incentives for countries to reduce emissions and to care about the emissions of other nations. For example, adding aerosol costs to CO2 costs could increase China’s incentive to reduce emissions by a factor of two. And it changes the net local benefit of local emissions in Europe from a net local cost. The study also shows that some emerging economies, like those in East Africa and India, may be more likely to work together to reduce emissions because their emissions have a big effect on each other.
This framework can also be used to maximize societal benefits from mitigation strategies currently under consideration by policymakers. The researchers applied it, for instance, to the “fair-share” approach outlined in the Paris Climate Agreement, in which all countries aim for the same CO2 emissions per capita. They found that the approach is good for keeping the climate stable, but it doesn’t help with death and crop damage from a combination of aerosol and CO2 emissions. This is because it focuses mitigation on places like the United States and Europe that already have low aerosol impacts.
Burney said, “By expanding societal cost calculations to include the geographically-resolved societal impacts of co-emitted aerosols, we show that individual countries are much more likely to take action and work together to do so than if we only looked at greenhouse gases.”
