Brown haze dims skies worldwide

A dirty brown haze sometimes more than a mile thick is darkening skies over vast areas of Asia and in the Middle East, southern Africa and the Amazon Basin, changing weather patterns and threatening health and food supplies, the United Nations reported.

The so-called atmospheric brown clouds are a mix of particles, ozone and other chemicals that come from cars, coal-fired power plants, burning fields and wood-burning stoves and fireplaces.

A report commissioned by the U.N. Environment Program said the clouds dim light by as much as 25% in some cities, including Karachi, Pakistan; New Delhi; Shanghai; and Beijing.