An unexpected and unwelcome Indian contribution to climate change is beginning to be highlighted: that of so-called black carbon (or, more colloquially, soot) which, according to recent studies, may account for almost 1/5 of global warming — or nearly half of the global warming contribution of carbon dioxide (CO2), the best known global-warming gas which has received substantially more attention from both the Indian and global policy communities.

Only in the last two years has black carbon’s importance to global warming begun to be well understood, as scientists began to analyse how soot deposits on Himalayan glaciers, often carried from distant parts of India and other countries, has caused these glaciers to absorb more sunlight and heat. While accurate statistics on black carbon are difficult to compile because its sources are highly diffuse, India is generally believed to be second only to China as a black carbon polluter with the two countries accounting for between 1/4 and 1/3 of the global black carbon emissions. And while wealthier countries tend to dominate the emissions of CO2, especially on a per capita basis, developing countries have relatively higher per capita emissions of soot, as these are exacerbated by dirtier combustion processes of all types, such as in coal-fired power plants and in engines, but most particularly in the often highly inefficient cookstoves that predominate among the rural poor.

The increasing importance of black carbon in the climate debate is a good news/bad news situation for India. On the positive part of the ledger, black carbon’s residence time in the atmosphere is brief (a matter of weeks, as opposed to decades for CO2) and thus by addressing black carbon, countries can achieve much more rapid reductions in global warming than can be achieved through CO2 reductions. Furthermore, India could make significant reductions in black carbon emissions and use these reductions as demonstrations that it is making serious efforts to address climate change — without signing up for any mandatory emissions restrictions which Indian politicians and diplomats have been understandably reluctant to embrace. Furthermore, because black carbon also causes a great deal of local pollution and damages human health, tackling the black carbon problem presents a rare alignment of interests between Indian officials and the international climate change community. Smoke inhalation from indoor cooking on unimproved stoves is estimated to contribute to 400,000 deaths in India each year; reducing such deaths has been an increasing focus of India’s public health community. Also, inefficient traditional stoves often require much time and effort to supply with sufficient fuel.

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