Posted by: Michael Ritter PhD | November 14, 2008

Atmospheric Brown Clouds Having Widespread Impact on Earth Systems

A satellite image shows a dense blanket of polluted air over central eastern China covering the coastline around Shanghai. (NASA/Goddard Space Flight Center)

A satellite image shows a dense blanket of polluted air over central eastern China covering the coastline around Shanghai. (NASA/Goddard Space Flight Center)

A new study from the United Nations Environment Programme reports “brown clouds” are darkening the skies over Asian cities, causing more extreme weather conditions, glaciers in the Himalayas to melt faster, and masking the effects of global warming.

Professor Veerabhadran Ramanathan, head of the UNEP scientific panel that released the report “”Atmospheric Brown Clouds: Regional Assessment Report With Focus on Asia,” focused on a three km-thick layer of soot and other made-made particulate that stretches from the Arabian Peninsula to China and the western Pacific. Atmospheric brown clouds result from the burning of fossil fuels and biomass.

In some instances, brown clouds aggravate the impact of global warming as they lead to the formation of black carbon and soot that absorbs sunlight and heats the air. But globally, brown clouds may be masking the impacts of climate change by 20 to 80 percent according to some researchers.

The study found five regional hotspots:

  • East Asia, covering eastern China;
  • The Indo-Gangetic plains in South Asia from the northwest and northeast regions of eastern Pakistan across India to Bangladesh and Myanmar;
  • Southeast Asia, covering Cambodia, Indonesia, Thailand, and Vietnam;
  • Southern Africa extending southwards from sub-Saharan Africa into Angola, Zambia and Zimbabwe; and
  • The Amazon Basin in South America.

Additional hotspots along the eastern seaboard of North America and in Europe were identified – but winter precipitation tends to remove and reduce their impact.

For more about atmospheric brown clouds and their impacts see the UNEP press release: Cities Across Asia Get Dimmer: Impacts on Glaciers, Agriculture and the Monsoon Get Clearer

The Physical Environment Links: Composition of the Atmosphere.

Watch Dr. Ramanathan give the presentation “Global Warming and Atmospheric Brown Clouds” for the Perspectives on Ocean Science series sponsored by UCTV

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