Black carbon consists of pure carbon formed through the incomplete combustion of fossil fuels, biofuel and biomass. It has been linked to environmental pollution and is rated third as a cause of global warming, after carbon di-oxide and methane.
According to US researchers, uncertainties prevail over existing methods to estimate black carbon emissions on the Indo-Gangetic plain with models currently in use not validated by on-site measurements.
Reporting their findings in Climate Change and Health, published in March, the researchers say that more accurate inventories of black carbon emissions, in particular from biomass-burning cook stoves used in the Indo-Gangetic plain region, are “critical to many health and climate applications”.
About 20 per cent of global black carbon emissions could be attributed to inefficient cook stoves that burn biomass. In South Asia, where millions of people lack access to clean cooking technologies, biomass burning is estimated to account for about two-thirds of black carbon emissions. Atmospheric winds are known to carry black carbon from the Indo-Gangetic plains and dump them on the glaciers and the snow-capped mountains of the Himalayas where they appear to influence glacial retreat.
Broadly, there are two approaches to estimating black carbon emissions. In the 'top down’ approach, ambient black carbon concentrations are measured and attributed to different sources using mathematical models. In the second, 'bottom up’ method, emissions from various sources are measured and estimations of the overall black carbon concentration are made.
The two approaches give contrasting estimates of the role of biomass burning, possibly because of the fact that they do not take into account the relationship between indoor and outdoor emissions that vary during the day. Studies in the Indo-Gangetic plain region have shown that both indoor and outdoor emissions peak when households prepare food — once in the morning, and once in the evening.
“Addressing the research gap in better understanding indoor to outdoor emissions of black carbon related to cooking with solid fuels will require better monitoring efforts as well as integration of data from field studies,” says Sutyajeet I. Suneja, a researcher at the Johns Hopkins University, and one of the authors of the paper.
Suruchi Bhadwal, associate director at The Energy Research Institute, New Delhi, suggests looking into the persistence of black carbon. “Since these emissions are localised, they might contribute to further heat absorption and high temperatures in those regions. These factors may aggravate the effects of climate change and steepen the impacts,” she says.
This piece was produced by SciDev.Net’s South Asia desk.