Soot, diesel exhaust worst culprits in global warming

March 24th, 2008 - 11:21 am ICT by admin

New York, March 24 (IANS) Black carbon pollution - soot, diesel exhaust - is a greater contributor to global warming than believed earlier, according to leading atmospheric scientist V. Ramanathan of the Scripps Institution of Oceanography. And China and India are major culprits, together accounting for between 25 and 35 percent of black carbon emissions.

Produced by biomass burning, cooking with solid fuels and diesel exhaust, black carbon has a warming effect three to four times greater than estimated, Madurai-born Ramanathan has written in the journal Nature Geoscience.

The article, co-authored by Greg Carmichael of the University of Iowa, 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.

The researchers also noted that mitigating black carbon would have immediate health benefits in addition to the long-term effect of reducing greenhouse gas emissions.

“Observationally-based studies such as ours are converging on the same large magnitude of black carbon heating as modelling studies from Stanford, Caltech and NASA,” said Ramanathan, one of the first persons to identify the role of CFCs in ozone depletion in the atmosphere.

“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.”

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

That is far higher than estimates of between 0.2 watts per metre squared and 0.4 watts per metre squared that were agreed upon as a consensus estimate in a report released in 2007 by the R.K. Pachauri-headed Intergovernmental Panel on Climate Change (IPCC), which won the Nobel last year.

Ramanathan, who has an engineering degree from Bangalore, said the 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 sulphates.

Though China and India contributed in a big way to black carbon emissions - thanks to burning of wood and cow dung in household cooking and the use of coal to heat homes, European nations that rely heavily on diesel fuel for transportation were also responsible.

“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.

In South Asia, pollution often forms a prevalent brownish haze that has been termed the “atmospheric brown cloud”.

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.