New research published in the journal Science Advances urges the necessity of reducing carbon dioxide and aerosol pollution simultaneously, warning that just cutting aerosol pollution on its own will fuel further warming of the planet.
"The conundrum," explained UC Riverside climate scientist and study co-author Robert Allen, "is that aerosols cause poor air quality and lead to premature deaths. However, these particles have a net cooling impact on the climate, so when you cut them that leads to a net warming effect."
As Allen mentioned, aerosol particles, the pollution that is emitted by the burning of fossil fuels, are particularly harmful for human health, with well-documented adverse effects such as asthma, bronchitis, and cancer. However, they also play a significant role in deflecting radiation from the sun and thus keeping the planet cooler than it otherwise would be.
To dig into the complexities of this relationship, the research team used computer models to pinpoint how aerosols impact the oceans under two different scenarios: one in which there is only a reduction in aerosols, and another scenario in which greenhouse gases are reduced simultaneously. They concentrated particularly on how the Atlantic meridional overturning circulation, or AMOC, would be affected.
The models showed that as aerosols are removed from the atmosphere, the AMOC would be disturbed, which would in turn have significant consequences on our climate. "The first scenario leads to the surprising result that fewer aerosols in the atmosphere could shift the region where most of the ocean is taking up heat, from the Southern Ocean toward the North Atlantic," Allen said.
"A projected decline in humanmade aerosols potentially induces a weakening of the AMOC, which plays an important role in ocean heat uptake and storage in the North Atlantic," elaborated Wei Liu, an assistant professor of climate change and sustainability at UCR.
The research team plans to continue their investigation by identifying the mechanisms by which aerosol reductions weaken the AMOC. In the meantime, the researchers urge for the need to cut aerosol pollution and greenhouse gas emissions simultaneously.
"Assuming complete removal, aerosols at most will cause warming of about 1 K," concluded Allen. "However, aerosol-induced warming, as well as the associated ocean circulation changes, can be moderated by rigorous cuts in greenhouse gases including methane and carbon dioxide."