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AGU: Geophysical Research Letters

 

Index Terms

  • Atmospheric Composition and Structure: Aerosols and particles
  • Global Change: Atmosphere
  • Atmospheric Composition and Structure: Pollution—urban and regional
  • Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 29, 1340, 4 PP., 2002
doi:10.1029/2002GL014687

Evidence of surface cooling from absorbing aerosols

R. Krishnan

Center for Atmospheric Sciences, Scripps Institution of Oceanography, University of California, San Diego, California, USA

V. Ramanathan

Center for Atmospheric Sciences, Scripps Institution of Oceanography, University of California, San Diego, California, USA

Anthropogenic emissions over the Asian region have grown rapidly with increase in population and industrialization. Air-pollutants from this region lead to a brownish haze over most of the North Indian Ocean and South Asia during winter and spring. The haze, with as much as 10–15% of black carbon (by mass), is known to reduce the surface solar insolation by about 10% (−15 Wm−2) and nearly double the lower atmospheric solar heating. Here we present an analysis of observed surface-temperature variations over the Indian subcontinent, which filters out effects of greenhouse gases and natural variability. The analysis reveals that the absorbing aerosols have led to a statistically significant cooling of about 0.3°C since the 1970s. The seasonally asymmetric cooling, which is consistent with the seasonality of the South Asian aerosol forcing, raises the new possibility that the surface cooling underneath the polluted regions, is balanced by warming elsewhere.

Published 14 May 2002.

Citation: Krishnan, R., and V. Ramanathan (2002), Evidence of surface cooling from absorbing aerosols, Geophys. Res. Lett., 29(9), 1340, doi:10.1029/2002GL014687.

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