10 September 2009
A new study led by researchers from CSD has sharpened the understanding of the climate effects of atmospheric aerosols (tiny airborne particles from pollution, biomass burning, and other sources). The study appeared on September 10 in the Journal of Geophysical Research and is featured as an Editor's Highlight. Lead author Dan Murphy and coauthors applied fundamental conservation of energy principles to construct a global energy "budget" of the climate's "credits" and "debits"-heating and cooling processes-since 1950, using only observations and straightforward calculations. They then calculated the cooling effect of the aerosols as the only missing term in the budget. The new estimate agrees well with the estimate of the 2007 assessment of the Intergovernmental Panel on Climate Change, but places that estimate on more solid ground and rules out the larger cooling effects that were previously thought to be possible.
Background: Particles formed from pollution can cool the climate directly by reflecting sunlight. Soot from biomass burning absorbs sunlight and warms the climate. Aerosols can also affect the formation and properties of clouds, altering their influence on climate. The net effect of all these direct and indirect factors is a cooling by aerosols, which has partially offset the warming by greenhouse gases. NASA and the University of Leeds in the United Kingdom were partners in the study.
Significance: The new observations-based study enhances the understanding of one of the more uncertain aspects of the human impacts on climate change research. This information on aerosol effects will help in predicting climate change and accounting for climate change to date.
D.M. Murphy, S. Solomon, R. W. Portmann, and K. H. Rosenlof of the NOAA Earth System Research Laboratory; P. M. Forster of the University Leeds, UK; and T. Wong of the NASA Langley Research Center, An observationally based energy balance for the Earth since 1950, Journal of Geophysical Research, doi:10.1029/2009JD012105, 2009.