Construction of climate change scenarios for a tropical monsoon region

Abstract

Composite seasonal scenarios (per °C change in global equilibrium mean) were developed for the Indian subcontinent for the period 2010-2039 using 5 General Circulation Models (GCMs), namely, HadCM2, CSIRO-MK2b, CGCM1, GFDL-Rl5 and ECHAM4/OPYC3. These scenarios indicate a general warming over the entire region by about 0.3 to 0.6°C (± 0.2°C) with more warming in the northern part and less in the southern part of the country. The study shows pockets of negative and positive changes in rainfall over the study area. Large variations in the estimation of rainfall changes from different models also set the upper and lower limits to more extreme values. Further, scenarios indicate a warming of about 0.4 ± 0.2°C over Gangetic West Bengal (GWTB) and surrounding regions in the eastern part of the country. The maximum change in rainfall over this part of the country, according to the scenarios developed, would be 4 %. Sub-grid scale seasonal scenarios have been developed over GWB, and surrounding regions through statistical downscaling. HadCM2 and ECHAM4/OPYC3 are considered for this purpose, as they more effectively represent spatial and temporal variations in rainfall and temperature over the area. Results reveal more warming (0.3 to 0.9°C) and more rainfall changes (-5 to +9%) than the projections developed without downscaling the GCM output. Further, scenarios developed for the winter and pre-monsoon seasons show unusual changes in rainfall and temperature, which may be due to mesoscale activities present in the study area. © Inter-Research 2005.