In a United Nations report, atmospheric brown clouds are described as one of the greatest threats to environmental health and the worldwide food supply. Brown clouds also have a huge negative effect on overall human health as well. Atmospheric brown clouds are persistent, moving air masses, found high in the atmosphere, largely made up of soot, chemicals, aerosols and unhealthy gases such as ozone. Brown clouds are caused by fossil fuels such as coal and other highly industrialized man-made pollutants. Controlled burning of wood and plants also contributes to the formation of brown clouds. Atmospheric brown clouds increase the amount of greenhouses gases in the air especially in industrialized countries.
Every country in the entire world is at risk from pollution caused by brown clouds. Brown cloud masses can move across entire continents in as little as two days. Cloud hot spots have been identified over North and South America, Europe, South Africa and Asia. The region from the Persian Gulf extending through much of Asia is covered with a brown cloud annually from November through April due to lack of monsoon rains to wash heavy pollutants out of the air. The brown cloud currently hanging over this region has caused a 25% reduction in sunlight. This effects crop production and helps to create the extreme weather conditions that have been witnessed in this part of the world in recent years.
Many scientists think that enough studies have been done to prove that brown clouds contribute to glacial melting. The Himalayan Glaciers which are the primary source of water for rivers throughout many parts of Asia have shrunk by five percent in the past 50 years and scientists think the glaciers could shrink another 70% in the next 50 years. While some scientists insist that there is no doubt that brown cloud pollution is contributing to glacial melting it is sometimes difficult to see the full impact of damage caused by brown clouds because these dense clouds help cool the earth's surface temperatures in some areas of the world because the pollution particles found inside of these toxic clouds reflect sunlight and cool down the air.
Scientists who study brown clouds warn that not only do brown clouds have a negative effect on the environment but they also have a negative effect on human health. Over two million people die in India each year from cardiovascular and respiratory diseases. Countries such as China and Hong Kong routinely suffer from smog pollution and residents of these countries have higher instances of asthma and other respiratory diseases. "All of this points to an even greater and urgent need to look at emissions across the planet because this is where the stories are linked in terms of greenhouse emissions and particle emissions and the impact that they're having on our global climate," said Achim Steiner, U.N. undersecretary general and executive director of the U.N. environment program.