Soot And Climate Change
Black carbon particulate pollution, or soot, may be making a much greater contribution to global warming than previously thought, according to a study published this week in Nature Geoscience. In “Global and regional climate changes due to black carbon”, atmospheric scientist V. Ramanathan and chemical engineer Greg Carmichael conclude that the atmospheric warming effect of soot is three to four times higher than the consensus estimate released in an IPCC report last year.
While CO2 traps solar energy radiating back from the Earth’s surface, soot particles absorb solar radiation as it enters the atmosphere, increasing its heat. When they subsequently settle on snowy areas, the reduced albedo increases heat absorption leading to melting of ice and snow.
Black carbon’s warming effect in the atmosphere is about 0.9 watts per square meter, compared with the IPCC estimate of 0.2 to 0.4 watts per square meter. It is the second most important contributor to global warming after CO2. 25% to 35% of black carbon in the atmosphere comes from South and East Asia, caused by the burning of wood and cow dung in household cooking and the use of coal to heat homes. In the US and Europe, diesel engines, wood fires and barbecues are major sources of black carbon. Forest fires also make a significant contribution. In addition to accelerating glacial melt, affecting water supplies for millions, soot-based smog has serious health implications, with the inhalation of smoke during indoor cooking linked to the deaths of an estimated 400,000 women and children.
While CO2 persists in the atmosphere for decades, soot particles remain airborne for a matter of weeks, so eliminating black carbon offers a nearly instant return on investment, the researchers said. Commercially available products that could substantially reduce black carbon emissions already exist. Ramanathan is seeking sponsorship for Project Surya, which would provide 20,000 rural Indian households with smoke-free cookers and monitor air pollution levels to measure the effect of the cookers.
Scripps Institution of Oceanography news item
Sphere: Related ContentPete Smith @ March 25, 2008