Soot case

Worse than estimated

Published: Saturday 15 November 2003

while scrutinising data of a new climate model, researchers from the us have found that microscopic black carbon particles (commonly known as soot) are more abundant across the world than was previously assumed by the Intergovernmental Panel on Climate Change (ipcc). The finding is alarming, as it means that most climate change negotiations to date may have been misdirected -- those trying to fight global warming consider estimates of atmospheric conditions by ipcc nothing less than the instructions in the Bible.

The new model, called the Aerosol Robotic Network (aeronet), is a global system of more than 100 sun photometres that measure the amount of sunlight absorbed by fine particles in the air at wavelengths ranging from ultraviolet to infrared. The researchers (from the Goddard Institute for Space Studies (giss) and the Columbia University) were startled to see the aeronet data vastly differing from information provided by the global-aerosol computer model and giss climate model, both of which include sources of soot aerosols considered by ipcc to make its estimation.

The difference was attributed to the fact that other climate models do not consider the tiniest of carbon particles incorporated inside the larger ones. According to the researchers, as per the aeronet data, soot causes about twice as much global warming than what has been estimated by ipcc.

Both soot aerosols as well as light-coloured tiny air pollutant particles (called sulphate aerosols) pose problems for air quality. Efforts are on to reduce sulphate aerosols. There is a pitfall, however, in reducing sulphate aerosols emissions without reducing black carbon emissions. Since soot is black, it absorbs heat and causes warming. Sulphate aerosols, on the other hand, are white and scatter sunlight; hence they lead to cooling (and thus partially mitigate the warming effect). If these soot particles are not reduced as rapidly as light-coloured pollutants, the world could warm more quickly.

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