How Brown Clouds Cause Environmental Damage
The greatest damage being done by brown clouds, also known as Atmospheric Brown Clouds, or ABCs, may be the damage to glaciers, especially those glaciers that provide the headwaters for most Asian rivers. These massive clouds also influence rainfall amounts and frequency, increasing the risk of flooding in some places, while decreasing rainfall amounts in others. ABCs also carry pollution around the world, creating problems in regions far from the point where they originated.
Brown clouds are caused by particles of soot and other substances known as aerosols. National Geographic reporter Anne Casselman reports that brown clouds can contribute to Himalaya glacier melt. She explains that "the latest study suggests that aerosols can be responsible for regional warming. Specifically, the cloud of aerosols over India enhance atmospheric warming there by 50%."
Since warming is a direct cause of glacial melting, the ABCs seem to be influencing that process. They amplify climate change by absorbing sunlight and heating the surrounding air (Science Daily). The retreat of glaciers in this region is especially disturbing. The "Hindu Kush-Himalayan-Tibetan glaciers... provide the head-waters for most Asian rivers, and thus have serious implications for the water and food security of Asia"(Science Daily).
Food security is threatened not just by the decreased amount of glacial water carried by rivers in the area. The ABCs also seem to be influencing rainfall amounts and duration for the entire region.
Since the 1950s "the Indian summer monsoon is...shrinking" both in the number of rainy days and the amount of rain that falls during the season. These decreases have ranged from five to seven percent since the 50s (Science Daily).
The ABCs impact weather, including monsoons, by setting up "new gradients in surface sea temperatures and surface sea evaporation rates" (Science Daily).
In other areas ABCs may cause "significant drying in northern China" while increasing the likelihood of "flooding in southern China" (Science Daily).
Air Quality Degraded
ABCs affect air quality far from the places where they form. These clouds carry pollution around the world, affecting air quality and agriculture.
In some places brown clouds measure two miles thick. These clouds are also causing some megacities, such as New Delhi and Beijing to actually become darker (Science Daily). Other cities identified as ABC hotspots include Bangkok, Cairo, Karachi, Seoul, Shanghai and Tehran. In these cities "soot levels are 10 per cent of the total mass of all human-made particles" (India Environment Portal).
Casselman, Anne. news.nationalgeographic/news
India Environment Portal. Nov 24 2008.
United Nations Environment Program. "Dirty Brown Clouds Impact Glaciers, Agriculture And The Monsoon." ScienceDaily 16 November 2008. 19 November 2009 http://www.sciencedaily.com