Atmospheric Brown Clouds: Regional Assessment Report with Focus on Asia

Report commissioned by the United Nations Environment Programme (UNEP), prepared by the Agriculture Impact Study Group coordinated by the Indian Agricultural Research Institute (IARI, India) and the Center for Clouds Chemistry and Climate of the Scripps Institution of Oceanography (SIO), USA; Water Impact Study Group coordinated by Nanyang Technological University (NTU), Singapore; and Health Impact Study Group Coordinated by Chulabhorn Research Institute (CRI), Thailand in coordination with the ABC Science Team. Cities from Beijing to New Delhi are getting darker, glaciers in ranges like the Himalayas are melting faster and weather systems becoming more extreme, in part, due to the combined effects of human-made atmospheric brown clouds (ABCs) and greenhouse gases in the atmosphere. The brown clouds, the result of burning of fossil fuels and biomass, are in some cases and regions aggravating the impacts of greenhouse gas-induced climate change, says the report. This is because ABCs lead to the formation of particles like black carbon and soot that absorb sunlight and heat the air; and gases such as ozone which enhance the greenhouse effect of CO2. Globally however brown clouds may be countering or 'masking' the warming impacts of climate change by between 20 and up to 80 per cent the researchers suggest.