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Sulfate Aerosols Cool Climate Less Than Assumed

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Max Planck Institute for Chemistry

Life span of cloud-forming sulfate particles in the air is shorter than assumed due to a sulfur dioxide oxidation pathway which has been neglected in climate models so far

Measurement Station Schmücke. HCCT 2010 (Hill Cap Cloud Thuringia 2010) - A ground-based integrated study of chemical-aerosol-cloud interactions at the Schmücke Mountain in the Thuringian Forest in September/October 2010. Source: Dr. Stephan Mertes/TROPOS

Measurement Station Schmücke. HCCT 2010 (Hill Cap Cloud Thuringia 2010) – A ground-based integrated study of chemical-aerosol-cloud interactions at the Schmücke Mountain in the Thuringian Forest in September/October 2010. Source: Dr. Stephan Mertes/TROPOS

Sulfur dioxide is as antagonist of greenhouse gases less effective than previously assumed. It forms sulfate aerosol particles in the air, which reflect sunlight, and as so-called cloud condensation nuclei influence the chemical processes within clouds. Therefore, sulfate aerosol particles help to cool the earth, making them an important factor in climate models. However, a team around researchers from the Max Planck Institute for Chemistry found out that it is likely most models overestimate the cooling effect of these particles. The reason is a largely disregarded reaction pathway catalysed by mineral dust within clouds, which has a strong influence on the life span of sulfate aerosol particles and their ability to reflect sunlight. [..]

Eliza Harris assumes that the models have overestimated the climate cooling effect of sulfate aerosols. So far it is not quantifiable to what degree Harris’ discovery will impact climate prognoses. However, future models should consider the TMI catalysis reaction as an important pathway for the oxidation of sulfur dioxide, says the scientist. She thinks that the impact on climate models of European regions might probably be low, as mineral dust concentrations in the air are small and sulfur dioxide (SO2) emissions are declining. “In India and China, however, where sulfur dioxide emissions are expected to rise in the near future, combined with significantly higher concentrations of mineral dust in the air, the effect could be stronger”, assumes Harris. Future studies will show.

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