Sunday, March 11, 2007

Global Dimming: Role of Aerosols

Global dimming is a term coined for reduction in surface reaching solar radiation. Surface observation of solar radiation over different location around the world shows overall decline in the surface reaching solar energy over long period of time. One of the major causes for this dimming is increase in aerosols loading in the atmosphere. There was research study by Alper et al., 2005 published in GRL.

The abstract reads...

‘From the 1950s to the 1980s, a significant decrease of surface solar radiation has been observed at different locations throughout the world. Here we show that this phenomenon, widely termed global dimming, is dominated by the large urban sites. The global-scale analysis of year-to-year variations of solar radiation fluxes shows a decline of 0.41 W/m2/yr for highly populated sites compared to only 0.16 W/m2/yr for sparsely populated sites (less than 0.1 million). Since most of the globe has sparse population, this suggests that solar dimming is of local or regional nature. The dimming is sharpest for the sites at 10°N to 40°N with great industrial activity. In the equatorial regions even the opposite trend to dimming is observed for sparsely populated sites.’

A documentary on global dimming is produced by BBC, for more details follow the link below

Complete Reference:

Alpert, P., P. Kishcha, Y. J. Kaufman, and R. Schwarzbard (2005), Global dimming or local dimming?: Effect of urbanization on sunlight availability, Geophys. Res. Lett., 32, L17802, doi:10.1029/2005GL023320

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