The Asian Brown Cloud

London used to be famous for its pea-souper fogs; Los Angeles still has a vast haze of pollution that hangs over it for long periods, and Mexico City suffers from an almost permanent haze of pollution. So does Santiago in Chile. These smogs are collections of chemical and physical particles usually from burning processes (energy power stations, heating systems and car and aircraft engines) which through their aerosols create huge clouds of pollution. The three cities I have mentioned cover urban areas (including those outside the city limits) where fifty million people live. That is plenty of people affected by these mixed-particle hazes. However the world’s largest mixed particle haze affects billions of people. It hangs over Southern Asia and the Indian Ocean and is known as the Asian Brown Cloud. Continue reading