In order to assess the climatic impacts of increasing greenhouse gas concentrations in the atmosphere on the Indian subcontinent with a fair degree of confidence, we recently undertook an intercomparison study of a range of general circulation modeling experiments for which the data were available to as. This study (Lal et al., 1998) reported our findings on the performance of each of the 17 global climate model experiments in simulating the present-day regional climatology over the Indian subcontinent. The analysis suggested that a few global climate models performed exceptionally well in their control simulation to represent the observed present-day climatological patterns over the region of interest. In this paper, we focus on the development of plausible climate change scenario for the Indian subcontinent based on selected model simulations with enhanced greenhouse gas forcings.
Our analysis suggests that, for a 1°C rise in mean annual global temperature, the seasonal surface air temperature increase over the Indian subcontinent is likely to range from 0.7°C to 1.1°C during winter and 0.6°C to 1.0°C during summer. The increase in summer precipitation associated with the projected scaled rise in surface temperature could be between 1.2% to 4.5% . The model results do not suggest any significant change in the winter precipitation over the region.
Taking into account the suggested range of climate sensitivity as well as the range of future greenhouse gas-induced global warming in selected general circulation model experiments, a plausible climate change scenario for the Indian subcontinent is developed for the years 2030 and 2070. A rise in mean winter surface air temperature of between 0.4°C to 1.7°C by the year 2030 and between 0.7°C to 3.4 °C by the year 2070 is projected. During the summer season, the temperature rise is expected to range between 0.3°C to 1.4°C by the year 2030 and 0.6°C to 3.1°C by the year 2070. The study suggests intense spells of summer monsoon rainfall over the Indian subcontinent due to enhanced convective activity in a warmer atmosphere.