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Features May 2007: Volume 4, Number 2

Asia’s Brown Cloud
By Robert Monroe


When Veerabhadran Ramanathan visits his native India these days, he is often treated like a pesky relative. His research and conclusions are unwelcome in certain government offices, and with various research labs.

Ramanathan, an atmospheric and climate sciences professor at UC San Diego’s Scripps Institution of Oceanography, is a world leader in the study of greenhouse gases, and has spent more than a decade studying what he terms the “atmospheric brown cloud”—a mass of soot and other pollutants that mix to form a haze of particles over the subcontinent. Heaviest in winter and spring, it hangs over Indian cities and Thai farmlands, over Chinese company towns and hitherto untouched Nepalese mountain peaks.

The cloud contains tiny soot particles from the burning of fossil fuels, crop residues burned by farmers, and cow dung and firewood burned by household cooks in practices unchanged for centuries. It also contains industrial gases issued by the manufacturing plants of the world ’s fastest growing economies, and soil dust from plains rapidly turning into desert through drought, water diversion and aggressive farming.

From the Indian Ocean Experiment (INDOEX) that Ramanathan led in the late 1990s to the three-dimensional profiles of the region ’s clouds gathered by unmanned aircraft starting in 2005, scientists have made measurements of everything from the size of the particles on which cloud droplets form to the amount of solar energy that reaches the ground.

The researchers determined that through a complex interplay of light, heat and atmospheric chemistry, the brown cloud is disrupting rainfall patterns in the region. Its thick haze has the dual effect of making the subcontinent cooler at street level but warmer at high altitudes. This latter effect has special consequence in the Himalayas, where Ramanathan recently discovered that the brown cloud is accelerating the melting of high-elevation glaciers, which provide billions of Asians with their drinking water. All this is on top of the respiratory problems faced by the billions breathing this smog on a daily basis.

However, in 2002, when the United Nations Environment Programme issued its first report on Ramanathan ’s Project Atmospheric Brown Clouds (ABC), and linked the pollution phenomenon profiled by INDOEX to societal impacts ranging from lung disease to lower crop yields, Indian scientists and administrators reacted with indignation. One team suggested that the UNEP and Ramanathan needed to separate “fact from fantasy” after Ramanathan suggested the brown cloud could imperil Asian agriculture.

Several Asian legislators and government officials have accused Ramanathan of playing into the Bush Administration ’s hands, which they feel may use his research on India and China’s pollution problems as an excuse not to take its own steps toward reducing air pollution and greenhouse gas emissions. Ramanathan notes, however, that the tide has turned somewhat. Several climate researchers, many of them from south and east Asia, have begun to provide observations and model simulations that support his original findings.

The cloud from Asia eventually reaches the West Coast of the United States, and Ramanathan and graduate student Odelle Hadley have seen evidence that the snowpack in the Sierra Nevada and other western mountain chains are being coated by pollution particles rinsed from the atmosphere by precipitation. The resulting “dirty snow” is duller and melts faster.

But the Scripps researcher is quick to point out that south Asia is but one cog in a worldwide chain of polluters. The United States pays it forward, however, by emitting pollution that ends up in western Europe. The sequence plays out globally every day with nearly every country in the world adding its share of airborne pollutants.

Ramanathan shared the results of a special analysis of the brown cloud in a February United Nations Environmental Programme meeting in Monaco, a session for the environmental ministers of China, India and African countries. In assessing its impacts, he reported that the rapid glacial melt being stoked by the brown cloud poses a threat to China and India ’s water and food supplies more than those of any other countries in the region. He left with a new charge from the African delegation to launch a study there similar to his Project ABC and with encouraging acknowledgement from the Chinese delegation of the problem its country faces.

But where mitigation of global warming will require infrastructure changes on a global scale, Ramanathan believes that the brown cloud could be history with a few years of effort and the use of technologies that already exist. He first observes that soot and the other forms of black carbon that create the brown cloud don’t remain in the atmosphere for long. Particles of that size are usually washed from the atmosphere within weeks after emission in contrast to carbon dioxide, which remains in the atmosphere a full century after spitting out from someone’s tailpipe.

Second, he believes that inexpensive, low-tech changes to everyday practices across rural areas of south and east Asia could yield immediate benefits. In India, for instance, 50 to 60 percent of black carbon emissions come from rural cooking that uses fuels like cow dung or firewood. Ramanathan is spearheading a pilot project in which such fuels are replaced with nvironmentally friendly alternative energy sources such as solar-powered cookers.

China’s recent actions, especially in anticipation of this summer’s Olympic Games in Beijing, suggest it is ready to try a similar course of mitigation to protect the health of its own citizens. The city will reportedly keep 1.5 million cars off the roads during the event and temporarily idle polluting factories in an attempt to improve air quality; Ramanathan plans to conduct a field project in neighboring South Korea to see if he can detect a drop-off in atmospheric pollution when the curbs are in place.

“ ”Ramanathan says. “So the technology is available to undertake a massive reduction. With international collaboration, Asia should be able to reduce its emissions substantially.”

But in the case of Beijing and other major Chinese cities, coal-fired power plants pose more of a problem than biomass burning. Scrubbing away the soot that issues from these plants will be no easy task, according to Charles Kennel, the former director of Scripps and the founding director of the UCSD Environment and Sustainability Initiative. But when he addressed the Indian and Chinese delegations in Monaco
in February he came away believing the two countries have no delusions about the magnitude of the job.

“ I would not say that reducing black carbon emissions will be easy,” Kennel says. “It will be tremendously difficult, but the public health and other advantages of doing so make it an attractive alternative for them.”

Robert Monroe is a writer at Scripps Institution of Oceanography, UC San Diego.


Pollution from China and India is turning up in the California snow pack, as well as accelerating global climate change, and affecting the health of a number of Asian nations.