Sulfate Aerosols' Cooling Ability Overestimated, Researchers Say

Sulfate aerosols cooling the atmosphere might not be as effective as previously thought, a new study has found.

The sulfate aerosol particles reflect light, keeping the earth cool. However, the life span of these cloud-forming aerosols is much shorter than estimated, skewing estimates regarding their cooling effect.

For the study, researchers from Max Planck Institute for Chemistry looked at the process of cloud formation on the top of a mountain. The sulfur particles act as nuclei for the clouds. Researchers in the study traced aerosol particles during cloud formation.

The study team analyzed the composition of sulfur compounds in various cloud samples. Researchers found that sulfur compounds had different isotopes. "The relative reaction rates of isotopes are like fingerprints, which tell us how the sulfate was formed from the sulfur dioxide," said Eliza Harris from the Max Planck Institute for Chemistry, according to a news release.

The sulfate in the clouds occurs primarily from oxidation of sulfur by oxygen. This reaction is catalyzed by transition metal ions. These processes usually occurred on large dust particles, which researchers believe leads to heavier clouds that fall much faster to the ground.

According to researchers, the clouds formed on heavier particles don't stay longer in the atmosphere to offer any cooling effect.

Eliza Harris and Bärbel Sinha from the Max Planck Institute for Chemistry, authors of the current study, say that current models that predict the cooling effect over countries such as China and India need to consider the role of transition metal ions in cloud formation.

The study is published in the journal Science.