A new research by scientists has suggested that black carbon, a form of particulate air pollution, has a warming effect in the atmosphere three to four times greater than prevailing estimates.
Scripps Institution of Oceanography carried out the research at UC San Diego atmospheric scientist V. Ramanathan and University of Iowa chemical engineer Greg Carmichael.
According to the scientists, soot and other forms of black carbon, which are often produced from biomass burning, cooking with solid fuels and diesel exhaust, could have as much as 60 percent of the current global warming effect of carbon dioxide.
That is more than that of any greenhouse gas besides CO2.
For their research, Ramanathan and Carmichael integrated observed data from satellites, aircraft and surface instruments about the warming effect of black carbon and found that its forcing, or 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.
The most recent observations, in contrast, have found significant black carbon warming effects at altitudes in the range of 2 kilometers (6,500 feet), levels at which black carbon particles absorb not only sunlight but also solar energy reflected by clouds at lower altitudes.
"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," said Ramanathan.
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.
The researchers also noted, however, that mitigation would have immediate societal benefits in addition to the long term effect of reducing greenhouse gas emissions.
According to them, elimination of black carbon, a contributor to global warming and a public health hazard, offers a nearly instant return on investment. Black carbon particles only remain airborne for weeks at most compared to carbon dioxide, which remains in the atmosphere for more than a century.
In addition, technology that could substantially reduce black carbon emissions already exists in the form of commercially available products.