BEIJING, China, November 13, 2008 (ENS) – A brown cloud of pollution caused by human activities, three kilometers thick and stretching from the Arabian Peninsula across Asia to the western Pacific Ocean, is darkening cities, speeding the melting of Himalayan glaciers and affecting human health, finds a new report from the United Nations Environment Programme.

Atmospheric brown clouds, formed by the burning of fossil fuels, biofuels, wood and plants, absorb sunlight and heat the air, experts write in the study released today in Beijing.

The clouds also mask the actual warming impact of climate change by anywhere between 20 and 80 percent because they include sulfates and other chemicals which reflect sunlight and cool the surface, according to the report.

Dimming of between 10 and 25 percent is occurring over Beijing and Shanghai, in China, Karachi, Pakistan, and New Delhi, India.

Air pollution dims Beijing. July 2008.
(Photo credit unknown)

Professor Veerabhadran Ramanathan, head of the UNEP scientific panel carrying out the research, is based at the Scripps Institution of Oceanography in La Jolla, California.

The new report provides confirmation of the atmospheric brown clouds effects that Ramanathan’s research first documented six years ago.

“Our preliminary assessment, published in 2002, triggered a great deal of awareness but also skepticism,” he said. “That has often been the initial reaction to new, novel and far reaching, counter-intuitive scientific research.”

Ramanathan called for an international response to the report’s findings that “tackles the twin threats of greenhouse gases and brown clouds and the unsustainable development that underpins both.”

“One of the most serious problems highlighted in the report is the documented retreat of the Hind Kush-Himalayan-Tibetan glaciers, which provide the headwaters for most Asian rivers, and thus have serious implications for the water and food security of Asia,” he said.

The scientific team behind the report is drawn from universities and research centers in China, India, Japan, Korea, Singapore and Thailand as well as Europe and the United States.

The scientists found that the artificial lowering of temperature by atmospheric brown clouds is leading to sharp shifts in weather patterns, causing drying in northern China while increasing the risk of flooding in China’s south.

Monsoon precipitation over India and South-East Asia has dropped up to seven percent since the 1950s, with the summer monsoon both weakening and shrinking.

The possible impact of atmospheric brown clouds could include elevated levels of ground-level ozone, which could result in crop losses of up to 40 percent in Asia.

Smoke and soot rises into the air over Mumbai.
(Photo by Avinash Anand)

Achim Steiner, UNEP’s executive director, voiced hope that the report, “Atmospheric Brown Clouds: Regional Assessment Report with Focus on Asia” will serve as an early warning of the phenomenon, which he hopes will now be “firmly on the international community’s radar.”

He called on developed countries to help their poorer counterparts attain the technology needed to spur green economic growth.

“In doing so, they can not only lift the threat of climate change but also turn off the soot-stream that is feeding the formation of atmospheric brown clouds in many of the world’s regions,” Steiner said.

Atmospheric brown clouds start as indoor and outdoor air pollution consisting of particles called primary aerosols and pollutant gases, such as nitrogen oxides (NOx), carbon monoxide (CO), sulfur dioxide (SO2), ammonia (NH3), and hundreds of organic gases and acids.

“Widespread plumes resulting from the combustion of biofuels from indoors; biomass burning outdoors and fossil fuels, are found in all densely inhabited regions and oceanic regions downwind of populated continents,” the report states.

The report points to 13 megacities as being “hotspots” for atmospheric brown clouds – Bangkok, Beijing, Cairo, Dhaka, Karachi, Kolkata, Lagos, Mumbai, New Delhi, Seoul, Shanghai, Shenzhen and Tehran.

Soot levels in these cities make up 10 percent of the total mass of all carbon particles in the atmosphere that result from human activities.

The clouds contain toxic aerosols, carcinogens and other harmful particles, which could result in more people suffering from respiratory disease and cardiovascular problems.

More research is needed to determine the precise role of the clouds on food production and farmers’ livelihoods, the report states. More research is also required on the brown clouds that exist in parts of North America, Europe, Southern Africa and the Amazon Basin.

“The new research, by identifying some of the causal factors, offers hope for taking actions to slow down this disturbing phenomenon,” said Professor Ramanathan. But he cautioned that “significant uncertainty remains in our understanding of the complexity of the regional effects of ABCs and more surprises may await us.”

To read the report, “Atmospheric Brown Clouds: Regional Assessment Report With Focus on Asia,” click here [www.unep.org].

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SAN DIEGO, California, March 23, 2008 (ENS) – Black carbon, particulate matter in the air produced by diesel exhaust, biomass burning, and cooking with solid fuels, has a warming effect in the atmosphere three to four times greater than existing estimates, according to scientists in an upcoming review article in the journal “Nature Geoscience.”

Atmospheric scientist V. Ramanathan with the Scripps Institution of Oceanography at University of California-San Diego and University of Iowa chemical engineer Greg Carmichael, said that soot and other forms of black carbon could have as much as 60 percent of the current global warming effect of carbon dioxide, more than that of any greenhouse gas besides carbon dioxide, CO2.

The researchers also say that mitigation would have immediate societal benefits in addition to the long-term effect of reducing greenhouse gas emissions.

The article, “Global and regional climate changes due to black carbon,” is posted in today’s online version of “Nature Geoscience.”

Professor V. Ramanathan explains his new
findings to reporters. (Photo
courtesy UC San Diego)

“Observationally based studies such as ours are converging on the same large magnitude of black carbon heating as modeling studies from Stanford, Caltech and NASA,” said Ramanathan.

“We now have to examine if black carbon is also having a large role in the retreat of arctic sea ice and Himalayan glaciers as suggested by recent studies,” he said.

In the paper, Ramanathan and Carmichael integrated observed data from satellites, aircraft and surface instruments about the warming effect of black carbon and found that its warming effect in the atmosphere, is about 0.9 watts per meter squared.

That compares to estimates of between 0.2 watts per meter squared and 0.4 watts per meter squared that were agreed upon as a consensus estimate in a report released last year by the Intergovernmental Panel on Climate Change, a United Nations sponsored agency that periodically synthesizes the body of climate change research.

Ramanathan and Carmichael said the lower, more conservative estimates are based on widely used computer model simulations that do not take into account the amplification of black carbon’s warming effect when mixed with other aerosols such as sulfates.

The models also do not adequately represent the full range of altitudes at which the warming effect occurs, they said.

The most recent observations have found significant black carbon warming effects at altitudes in the range of 6,500 feet, levels at which black carbon particles absorb not only sunlight but also solar energy reflected by clouds at lower altitudes.

Between 25 and 35 percent of black carbon in the global atmosphere comes from China and India, emitted from the burning of wood and cow dung in household cooking and through the use of coal to heat homes.

Countries in Europe and elsewhere that rely heavily on diesel fuel for transportation also contribute large amounts.

“Per capita emissions of black carbon from the United States and some European countries are still comparable to those from south Asia and east Asia,” Ramanathan said.

Black carbon rises from land clearing fires on the island of Borneo. October 2006. (NASA image by Jeff Schmaltz, MODIS Rapid Response Team)

In south Asia, air pollution often forms a brownish haze. Ramanathan’s previous research has indicated that the warming effects of this smog appear to be accelerating the melt of Himalayan glaciers that provide billions of people throughout Asia with drinking water.

In addition, the inhalation of smoke during indoor cooking has been linked to the deaths of an estimated 400,000 women and children in south and east Asia.

Ramanathan said that an observation program for which he is currently seeking corporate sponsorship could dramatically illustrate the benefits. Known as Project Surya, the proposed venture would provide some 20,000 rural Indian households with smoke-free cookers and equipped to transmit data. At the same time, a team of researchers led by Ramanathan would observe air pollution levels in the region to measure the effect of the cookers.

Carmichael said he hopes that the paper’s presentation of the immediacy of the benefits will make it easier to generate political and regulatory momentum toward reduction of black carbon emissions.

“It offers a chance to get better traction for implementing strategies for reducing black carbon,” he said.

The National Science Foundation, the National Oceanic and Atmospheric Administration and the National Aeronautics and Space Administration funded the review.

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