Uncertainty exists in aerosol climate modeling

NOV 03, 2009

Physics Today

Science : Many aerosols cool the atmosphere (a negative forcing), whereas ozone and black carbon aerosol have a warming effect (a positive forcing).There is thus a strong motivation for treating air pollution control and climate change in common policy frameworks, argue Almut Arneth and colleagues in Science .However, changes in pollutant and precursor emissions, atmospheric burden, and radiative forcing are not necessarily proportional. Drew T. Shindell and colleagues at NASA Goddard Institute for Space Studies in New York, report that current models do not capture many of the complex atmospheric processes involving aerosols and reactive trace gases.As Arneth and colleagues state:

Changing aerosol burdens may alter local and regional cloud cover and precipitation, change the intensity or timing of the monsoon circulation, and even shift precipitation across national borders. Changes in cloud cover and precipitation will also feed back on the photochemistry and rainout of short-lived species. These issues must be considered if aerosol emissions are to become part of climate policy.Given the toxicity of pollutants, the question is not whether ever stricter air pollution controls will be implemented, but when and where. The jury is out on whether air pollution control will accelerate or mitigate climate change. Still, the studies available to date mostly suggest that air pollution control will accelerate warming in the coming decades.