Sources of Uncertainties in Climate Forcing by Black Carbon Aerosol over Indian Region Using Regional Climate Model

The models of the atmospheric Black Carbon (BC) cycle are highly uncertain and the results are difficult to evaluate as they are influenced by emission inventories, the inclusion of BC ageing processes that can change BC lifetime and wet deposition that is the most uncertain process in the models. The objective of this study is to understand the various sources of uncertainties in climate models and to quantify the uncertainty in Climate Forcing due to the treatment of BC (emission and transport) in Regional Climate Model (RegCM 4.1). The methodology adopted in this study utilized emission data of June and December 2001 obtained from EDGAR. The comparative study was done between the estimated surface Radiative forcing for BC with the results obtained in similar studies done for Bangalore in December 2001 and 5 year averaged value for June and December for Kanpur. The effects on the surface temperature, surface pressure and daily precipitation rate were estimated for the months of June and December 2001 to quantify the response of the atmosphere to BC forcing in Climate models. The study concludes that the uncertainties involved in the climate models due to BC emission inventories are due to the underestimation of the emissions in EDGAR database as compared to the other emission inventories for Indian region. It was observed that the BC aerosols in atmosphere are responsible for surface cooling over the Indian region. The reduced surface temperatures in the Bay of Bengal, Arabian Sea and over Indian region act to reduce the surface pressure and precipitation over maximum parts of India.