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Asian Brown Cloud Particulate Pollution Amplifies Global Warming

Asian Brown Cloud pollution is amplifying warming, accelerating the melting of the Himalayan glaciers. Click to enlarge. Credit: Nicolle Rager Fuller, National Science Foundation

A new analysis of pollution-filled “brown clouds” over south Asia by researchers at the Scripps Institution of Oceanography in La Jolla, Calif., suggests that the region may be able to arrest some of the alarming melting of Himalayan and other tropical glaciers by reducing its air pollution.

The team, led by atmospheric chemist V. Ramanathan of Scripps, found that atmospheric brown clouds enhanced solar heating of the lower atmosphere by about 50%. The results are in a paper in this week’s issue of the journal Nature.

The combined heating effect of greenhouse gases and brown clouds, which contain soot, trace metals and other particles from urban, industrial and agricultural sources, is enough to account for the retreat of Himalayan glaciers in the past half century, the researchers concluded. These glaciers supply water to major Asian rivers, including the Yangtze, Ganges and Indus. These rivers are the chief water supply for billions of people in China, India and other south Asian countries.

If it becomes widespread and continues for several more decades, the rapid melting of these glaciers, the third-largest ice mass on the planet, will have unprecedented effects on southern and eastern Asia.

—V. Ramanathan

The scientists based their conclusions on data gathered by a fleet of unmanned aircraft during a landmark field campaign conducted in March 2006, in the skies over the Maldives, an island nation in the Indian Ocean south of India.

The Maldives Autonomous unmanned aerial vehicle Campaign (MAC) took place during the region’s dry season when polluted air masses travel south from the continent to the Indian Ocean. (Earlier post.) The air typically contains particles released from industrial and vehicle emissions, and through biomass burning.

Such polluted air has a dual effect of warming the atmosphere as particles absorb sunlight, and of cooling Earth’s surface as the particles reduce the amount of sunlight that reaches the ground.

Atmospheric brown clouds are mostly the result of biomass burning and fossil fuel consumption. They consist of a mixture of light-absorbing and light-scattering aerosols and therefore contribute to atmospheric solar heating and surface cooling. The sum of the two climate forcing terms—the net aerosol forcing effect—is thought to be negative and may have masked as much as half of the global warming attributed to the recent rapid rise in greenhouse gases. There is, however, at least a fourfold uncertainty in the aerosol forcing effect. Atmospheric solar heating is a significant source of the uncertainty, because current estimates are largely derived from model studies.

...We found that atmospheric brown clouds enhanced lower atmospheric solar heating by about 50 per cent. Our general circulation model simulations, which take into account the recently observed widespread occurrence of vertically extended atmospheric brown clouds over the Indian Ocean and Asia, suggest that atmospheric brown clouds contribute as much as the recent increase in anthropogenic greenhouse gases to regional lower atmospheric warming trends.

—“Warming trends in Asia amplified by brown cloud solar absorption”

During 18 flight missions, the aircraft, flying in stacked formations, made nearly simultaneous measurements of brown clouds from different altitudes, creating a profile of soot concentrations and light absorption that was unprecedented in its level of vertical detail. The researchers validated the data from the aircraft with ground-based measurements taken at a station at the Maldivian island Hanimadhoo.

The main cause of climate change is the buildup of greenhouse gases from the burning of fossil fuels. But brown clouds, whose environmental and economic impacts are beginning to be unraveled by scientists, are complicating and in some cases aggravating their effects. It is likely that in curbing greenhouse gases we can tackle the twin challenges of climate change and brown clouds, and in doing so, reap wider benefits--from reduced air pollution to improved agricultural yields.

—Achim Steiner, United Nations under-secretary general and executive director of the UN Environment Programme (UNEP)

The analysis reveals that the effect of the brown clouds explains temperature changes observed in the region over the last half-century. It also indicates that south Asia’s warming trend is more pronounced at higher altitudes.

The conventional thinking is that brown clouds have masked as much as 50 percent of global warming by greenhouse gases through so-called global dimming. While this is true globally, this study reveals that over southern and eastern Asia, the soot particles in the brown clouds are in fact amplifying the atmospheric warming trend caused by greenhouse gases by as much as 50 percent.

—V. Ramanathan

In addition to Ramanathan, the report’s authors include Muvva Ramana, Gregory Roberts, Dohyeong Kim, Craig Corrigan, Chul Chung from Scripps Oceanography and David Winkler from NASA’s Langley Research Center.

The National Ocean and Atmospheric Administration (NOAA) and NASA also provided funding, as did UNEP, which sponsors the Atmospheric Brown Clouds (ABC) project and operates the Maldives ABC observatory in collaboration with Scripps.




So the brown cloud is good "global dimming" helps keep the planet cool or is brown cloud bad because it heats up the atmosphere^/~???

Clean up the air and the ice pack won't melt as fast. Millions of people won't have asthma they will just die from lack of water.....wait,what

Lou Grinzo

Joseph: No. Stop global warming and people will have more water, as the glaciers and snow packs that many millions of people depend on for their summer water supply will stop shrinking.


I imagine that the soot from these particulate emissions also lands on the glaciers and adds yet more heat absorbtion to the equation. Without the glaciers the only thing they can do are massive desalination plants, which creates their own set of problems (brine, energy).

I imagine that cleaning up the particulates would be the best first step they can make.


Just a good illustration of how complex GW is. Soot has some cooling effect and some warming. And we can't say what portion of warming is due to this and what is from CO2 and what may be natural.

But what we can say is that man is adding this soot and other particles to the air. Burning coal releases sulfur gases and mercury and some other traces into the air. And regardless of what soot does in warming it certainly is bad for health.

Effective technology to clean up coal burning exists and is affordable - not free but not ruinous either. It is simply a matter of whether governments demand it.

I wish reducing CO2 emission was as practical.


Glaciers have no effect on river's flow. Amount of winter snowfall and rate of its melting do. It is well-known fact to everybody living in mountain region.


"Glaciers have no effect on river's flow."

When the glaciers are gone, and the rivers turn to sand in the dry season, then, indeed, the glaciers will have no effect.

Tarun Juyal

I am a regular reader of your article. And I am very impress with your blog upon Global Warming. Now I am also write a blog upon effects and causes of Global Warming. This blog is collection of news & reviews like the study found that global warming since 1985 has been caused neither by an increase in solar radiation nor by a decrease in the flux of galactic cosmic rays. Some researchers had also suggested that the latter might influence global warming because the rays trigger cloud formation.


"I imagine that cleaning up the particulates would be the best first step they can make."

I had read this earlier as well, that the black soot mainly produced by China(though do not rule out Russian preponderance of old furnaces) is more damaging, due to the particulate matter distributing across glaciers, mountains, etc., increasing heat absorbtion.

Stan Peterson

The Global Warming enthusiasts are truly getting desperate.

In order to explain why temperatures declined from 1940 to until the late '70s, even while atmospheric CO2 level were "rising", they blamed aerosol cooling. They said aerosols cooled the world and masked and prevented the warming that should have happened, but didn't.

Now they say the same aerosols, from emerging East Asia heat the world. Bovine Scatology.

Recent Science reveals that Solar radiation reached a cyclical peak in 1940, and then declined until 1976. That explains why the Earth cooled. And despite "rising" CO2 levels.

The Solar output increased from 1976 until 1998 and the Earth warmed. Solar out put then crested and plateaued before beginning a cyclical decline. Then it has only started its periodic decline and there hasn't been any appreciable warming since 1998's peak.

Evidence from the fleet of new Solar orbiting satellites have revolutionized the Sciences of the Sun since 2002. We can now even predict that there will be a minor blip upward in Solar output for two years or so in 2011 and 2012, and the Earth will resume cooling until at least 2030 that it has now begun.

But it seems that some scientists resist the new. Opponents with quite valid scintific reputations, of Newton said his Gravitational theories were impossible. Ditto for Einstein's relativity. Ironically, Einstein late in life resisted Bohr's Quantum Mechanics.

These fellows must be GHG apologists, as they twist GHG theories until they break. They insist the Solar output has no part to play in any of this.

Well modern Science, almost daily produces evidence otherwise, and the IPCC is listening. If you look at any evidence predating about 2001 its all Global
Warming oriented. Any recent Science since then is increasingly debunking the "certainties" of the '80s and '90s.

Science, unlike political dogma, evolves as more is known. It was only a few years years ago, that Dark Matter and Dark Energy were undreamed of ideas. Now we know that they constitute most of the Universe, even as we don't know much about either. Global Warming was "settled Science" in about the same era, and is increasingly looking like ancient theories as valid as Ptolemy's Epicycles.

Even if GHG theory has some validity; the IPCC has already limited it and decreased it ability to alter the climate by some 35%, in the period from TAR III and AR4 (5 years). This is due, to the stabilization and decline of all GHG gases except CO2, and the removal of GHG responsibility for 12% of warming due to more intense light from the Sun.

The latest results roilling the Science community, is the emerging scandal about the Sibel antarctic ice cores.

And also the re-investigation of old 18th, 19th, and early 20th century scientific measurements of atmospheric content, including CO2. These had been discredited and disregarded by Callendar and Keeling in the '50s and '60s. Now revisiting this data is generating lots of questions.

There was lots of data from some 600 odd science teams, including the works of at least 4 Nobel Prize winners that was disregarded and not looked at for the past 50 years.

That data has revealed a new CO2 lunar cycle that was unappreciated and overlooked by the modern Mauna Loa CO2 observatory. It also reveals Tambora and Krakatoa effects. But most of all it reveals the CO2 measurements were variable over time and place from 440 ppm in 1815 as a result of Tamboro, to a low of 300 ppm.

On average the over 90,000 measurements of CO2 levels were about 340 ppm. It appears this data negates the presumed pre-Industrial level of rock steady 290 ppm for CO2.


We can now even predict that there will be a minor blip upward in Solar output for two years or so in 2011 and 2012, and the Earth will resume cooling until at least 2030 that it has now begun.

Are you referring to the routine solar maximum that will happen around 2011-2012, or a blip on top of that?

Either way, we're almost certainly due for some cooling - NASA is predicting that solar cycle 25 will be substantially weaker than normal, and it's beginning to look like the upcoming cycle 24 may be as well.


ACE workshop is a great cheater in Bangladesh. So careful about this cheater.

Stan Peterson

Matthew, Yes I am speaking to that solar maximum.. and yes Solar 25 will be a the smallest maximum since Science started keeping records a few hundred years ago...

The scandalous way the Sibel ice cores were handled, is also causing some consternation. Now that it has been revealed after all this time. Letting the cores partially melt while bringing them back from Antarctica and not revealing that any data from them was compromised, is reflecting badly on those researchers.

Those cores have been the basis of much of the "evidence" for pre-industrial CO2 at 290 ppm. Now that it has been revealed that they do not agree with the Vostock ice cores and that the Vostock ice cores have other issues with the very unorthodox way they handled entrained air issue, is roiling the ice core community.

Dr Zbiegniew Zaworowski, who is a world authority on Ice core analysis,has already called for new analysis to replace this data. He was was the original Chairman of the UN Organization now known as the IPCC, was appalled when he discovered the news about the fudged data. He said this called into question any data or analysis created from the Sibel and Vostock ice cores.


its really a serious matter that we are living under a cloud that is slowly killing us..

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