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Atmospheric Brown Clouds

Atmospheric brown clouds (ABCs), the result of burning of fossil fuels and biomass, contain a variety of toxic aerosols, carcinogens and tiny particles that have been linked with a variety of health effects from respiratory disease and cardio-vascular problems to premature death. Brown clouds also affect agriculture and in some cases and regions aggravating the impacts of greenhouse gas-induced climate change. 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. This is because of particles such as sulfates and some organics which reflect sunlight and cool the surface.

Project Atmospheric Brown Cloud was established by the United Nations Environment Programme (UNEP) in 2002 following the documentation of brown clouds and haze by the Indian Ocean Experiment.

General information about Project Atmospheric Brown Cloud can be found at:

Atmospheric Brown Clouds: Regional Assessment Report with Focus on Asia (November 2008) can be found at:

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