How Now Brown Cloud?
As world government and environment leaders congregate in Poznan, Poland this week to progress down the path towards a post-Kyoto Protocol global climate change action accord, evidence of human production of carbon dioxide, other gases and particulates are clearly evident in the form of massive brown clouds that exist over huge areas of Asia, the Middle East, southern Africa and the Amazon Basin. In addition to posing health problems and limiting visibility, these “atmospheric brown clouds,” the result of burning fossil fuels and wood, are changing weather patterns and threatening food supplies, according to a United Nations Environment Program report.
Found to be more than one mile thick around glaciers in the Himalaya and Hindu Kush mountains and evident over Beijing during the Summer Olympics, the brown clouds are an unhealthy mix of CO2 and other gases, particles, ozone and other chemicals that come from vehicle emissions, those of coal-fired power plants, burning fields and wood burning stoves. First discovered in 1990, they are more widespread and are causing more environmental damage than previously thought, according to UNEP's latest report, which was undertaken with funding from Italy, Sweden and the US.
The international community needs to respond to the “the twin threats of greenhouse gases and brown clouds and the unsustainable development that underpins both,” firstly in the form of basic research to better understand the as yet uncertain specific effects and mechanisms by which the brown clouds are affecting weather patterns and climate at the regional level, lead researcher Veerabhadran Ramanathan, a University of California professor of climate and ocean sciences, was quoted as saying in an AP report.
The brown clouds obscure the sun and absorb solar radiation, prompting concerns about there climate changing effects and their role in causing extreme weather conditions. Monsoon rains over India and southeast Asia have decreased between 5 and 7 percent since the 1950s, brown clouds and global warming cited as possible causes. The latter are also dimming solar light by as much as 25% in cities including Karachi, New Delhi, Beijing and Shanghai. Soot levels in 13 mega cities across the Asian continent have risen alarmingly, according to UNEP.
Glaciers feed the Ganges, Indus, Yangtze and Yellow rivers. Soot from the clouds winds up on the surface of the glaciers and increases the amount of sunlight they absorb, increasing melting. The glaciers and rivers underpin the entire continent's agricultural and food supplies. China's glaciers have shrunk 5% since the 1950s and some 47,000 glaciers in China have receded some 3,000 square kilometers (1,158.31 square miles) in the past 25 years, according to the Chinese Academy of Sciences.
Though their effects are otherwise deleterious, the phenomenon help cool the earth's surface and mask the impact of global warming by an average 40%, according to to AP's report.