Our freelance writer Biplab Das dug out an interesting research paper from Geophysical Research Letters this week. Though the authors are from Argonne National Laboratory, Illinois; NASA Goddard Institute for Space Studies and Columbia Earth Institute, Columbia University, New York; they have been working on the contribution of aerosols to climate change in India and China.
It is worth pointing out here that there has been very little study of the contribution of aerosol emissions from India and China to radiative forcing. Radiative forcing is the process through which about 30 per cent of sunlight reaching the Earth’s surface is reflected back into space as invisible infrared light. Aerosols generated by human activities reflect infrared light generated by reflected sunlight, thereby trapping it in the atmosphere. This alters radiative forcing, resulting in climate change. Recent studies have identified aerosol emission, particularly black carbon emission from industrializing countries like India and China, as emission control targets for mitigating climate change.
So the researchers have found that these small airborne particles called aerosols (for example, black carbon particles in diesel exhaust and sulfate particles produced by coal burning) in India and China may indirectly contribute to climate change. Higher black carbon levels in the atmosphere lead to warming, whereas increased sulfate levels cause cooling.
To find out the situation in India and China, the researchers examined emissions from the most important aerosol sources in the two neighbouring countries and estimated the net radiative forcing from each source, both locally and globally. In this analysis, they used models developed by the NASA Goddard Institute for Space Studies.
Major emission sources of black carbon are diesel truck and bus exhaust and residential biofuel and fossil-fuel combustion. For organic carbon, residential biofuel and fossil-fuel combustion are important sources. The study found that fossil-fuel combustion in the power sector accounts for 52.3 per cent of sulphur dioxide emission in India.
The researchers reveal that residential biofuel combustion in both India and China gave rise to significant positive direct radiative forcing through black carbon emission. They say that aerosol emission from diesel trucks and buses also makes a positive contribution to radiative forcing in India.
1. Streets, D. G. et al. Radiative forcing due to major aerosol emitting sectors in China and India. Geophys. Res. Lett. (2013) doi: 10.1002/grl.50805