March 27, 2005
Soot pollution from southern Asia appears to be contributing to climate changes at the North Pole, according to a study by NASA scientists.
The pollution is raising atmospheric temperatures and speeding up the melting of snow and sea ice, the researchers said.
They believe they have found a link between the timing of Arctic warming and ice loss and deposits of tiny particles from man-made pollution during the late 20th century. They have been tracking the worldwide effects of soot.
The findings, which support earlier conclusions, demonstrate that the climate changes affecting the Arctic region are complex and may be a result of traditional pollution as well as global warming from the release of heat-trapping greenhouse gases.
The findings also show that most of the pollution does not come from smokestacks and tailpipes in the developed world. Instead, it comes from industrial emissions in south Asia and forest fires and other burning of vegetation across the planet.
CNN.com
December 23, 2003
WASHINGTON (AP) --NASA scientists say soot, mostly from diesel engines, is causing as much as a quarter of all observed global warming by reducing the ability of snow and ice to reflect sunlight.
Their findings on how soot affects reflective ability, known as albedo, raise new questions about human-caused climate change from the Arctic to the Alps.
"We suggest that soot contributes to near worldwide melting of ice that is usually attributed solely to global warming," National Aeronautics and Space Administration scientists James Hansen and Larissa Nazarenko wrote in a paper published Monday in the Proceedings of the National Academy of Sciences.
"Soot is a more all-around 'bad actor' than has been appreciated," they wrote. Soot is a blackened material formed mainly from carbon particles that are, along with salts and dust, byproducts of burning fossil fuels and vegetation.
Hansen, director of NASA's Goddard Institute for Space Studies, and Nazarenko, a staff associate there, found soot is twice as potent as carbon dioxide in changing global surface air temperatures in the Arctic and the Northern Hemisphere.
Greenland may be an exception, they said, because it is downwind from Canadian forests and has little manmade pollution.
The biggest source of soot in developed countries is diesel fuel, but major sources elsewhere include burning wood, animal dung, vegetable oil and other biofuels.
Hansen told The Associated Press that the authors estimate the soot effect is equivalent to putting a 1-watt bulb, the size of a miniature Christmas tree bulb, over every two square yards in the Northern Hemisphere. The effect is greater in northernmost snow regions, and almost nonexistent in the tropics.
Levels of airborne soot as high as about 100 parts per billion were found in the Alps, enough to reduce the snow's ability to reflect light rather than absorb it from about 98 percent down to between 80 percent and 90 percent, Hansen said. In spring and summer, as the snow melts and some soot accumulates as crud on the surface, the remaining snow is even darker, he said.
The scientists suggest in their paper that the same pattern could occur in the Himalaya range of South Asia, where prevailing winds might deposit fossil fuel and biofuel soot carried in a brown haze from India.
Many scientists believe the burning of fossil fuels is causing an increase in atmospheric carbon dioxide, triggering what is called the greenhouse effect. A higher concentration of CO2 in the atmosphere would trap more of the sun's heat, possibly causing the Earth to warm.
Scientists thought until recently that only carbon dioxide and other greenhouse gases have global reach and effect. They now are finding the same thing with these microscopic, suspended particles of pollutants, generically known as aerosols, that settle on ground hours later.
Soot particles, which absorb toxic organic material, are minute enough to penetrate skin. Soot is the aerosol most responsible for the haze in rapidly developing countries such as India and China, the scientists said.
Michael Oppenheimer, a Princeton professor and expert on climate policy, called the study "an interesting early calculation" that could prove to be important.
"It means that -- if it's right -- we need to keep an eye on it," he said. "When we think about all these greenhouse gases, we ought also to think about controlling these particles that are also changing the climate."
The Bush administration in 2001 ordered pollution cuts from heavy-duty diesel engines and diesel fuel used in highway trucks and buses. This year it proposed requiring a 90 percent reduction in pollution from diesel-powered construction and other off-road equipment, starting with 2008 models.
By John Heilprin
December 23, 2003
Soot mostly from diesel engines is blocking snow and ice from reflecting sunlight, which is contributing to "near worldwide melting of ice" and as much as a quarter of all observed global warming, top NASA scientists say.
The findings about the snow and ice albedos — their power to reflect
light falling on the surface — raise new questions about human-caused
climate change from the Arctic to the Alps.
"We suggest that soot is a more all-around `bad actor' than has been
appreciated," NASA scientists James Hansen and Larissa Nazarenko wrote
in a paper published Monday in the Proceedings of the National Academy
of Sciences.
Soot comprises carbon particles that are, along with salts and dust, byproducts of burning fossil fuels and vegetation. In developed countries, the biggest source is diesel fuel. Elsewhere, burning wood, animal dung, vegetable oil and other biofuels is a major source of soot.
Hansen, director of National Aeronautic and Space Administration's Goddard Institute for Space Studies, and Nazarenko, a staff associate there, found soot is twice as potent as carbon dioxide in changing global surface air temperatures in the Arctic and the Northern Hemisphere.
Greenland may be an exception, they said, because it is downwind from Canadian forests and has little manmade pollution.
In response to questions from The Associated Press, Hansen said Monday that the authors estimate the soot effect is equivalent to putting a 1-watt bulb, the size of a miniature Christmas tree bulb, over every two square yards in the Northern Hemisphere. The effect is greater in northernmost snow regions, and about zero in the tropics.
Levels of airborne soot as high as about 100 parts per billion were found in the Alps, enough to reduce the snow's ability to reflect light rather than absorb it from about 98 down to between 80 and 90 percent, Hansen said. In the spring and summer, as the snow melts and some soot accumulates as crud on the surface, the remaining snow is even darker, he said.
The scientists suggest in their paper that the same could occur in the Himalaya range of South Asia, where prevailing winds might deposit fossil fuel and biofuel soot carried in a brown haze from India.
Scientists thought until recently that only carbon dioxide and other greenhouse gases have global reach and effect. They now are finding the same thing with these microscopic, suspended particles of pollutants, generically known as aerosols, that settle on ground hours later.
Soot particles, which absorb toxic organic material, are minute enough to penetrate skin when breathed in. Soot is the aerosol most responsible for the haze in rapidly developing countries such as India and China, the scientists said.
Michael Oppenheimer, a Princeton professor and expert on climate policy, called the study "an interesting early calculation" that could prove to be important.
"It means that — if it's right — we need to keep an eye on it," he said. "When we think about all these greenhouse gases, we ought also to think about controlling these particles that are also changing the climate."
The Bush administration ordered in 2001 pollution cuts from heavy-duty diesel engines and diesel fuel used in highway trucks and buses. This year it proposed requiring a 90 percent reduction in pollution from diesel-powered construction and other off-road equipment starting with 2008 models.
December 23, 2003
To enlarge the image, click on it.
Soot pouring out of trucks and chimneys
is having a major worsening effect on global warming, scientists said
today.
The impact of soot in the atmosphere on climate is much larger than was
previously realized, a new study has shown.
It could even be responsible for a quarter of observed global warming,
say the researchers.
Soot, mainly composed of black carbon, is the dusty by-product of
burning fossil fuels and vegetation.
Levels are highest over China and India, where coal and biofuels are
burned in households. Europe and North America were the major source is
diesel fuel.
Soot warms the Earth by darkening snow and ice, causing it to absorb
rather than reflect sunlight.
Two NASA scientists have now found that soot is twice as effective as
carbon dioxide at raising global surface air temperature.
James Hansen and Larissa Nazarenko, from the American space agency’s
Goddard Institute for Space Studies in New York, said high soot
emissions might be substantially contributing to earlier spring melts.
It could also be helping glaciers, sea ice and ice sheets to melt at
lower temperatures, because black carbon absorbs more energy than clean
snow and ice.
The researchers wrote in the journal Proceedings of the National Academy
of Sciences: “This indirect soot forcing may have contributed to global
warming of the past century, including the trend toward early springs in
the northern hemispheres, thinning arctic sea ice, and melting land ice
and permafrost.”
They suggested reducing soot emissions – a move that has not yet been
considered by the international community.