IMPACT OF GREENHOUSE WARMING ON THE CLIMATE OF NORTH-WEST INDIA AS INFERRED FROM A COUPLED ATMOSPHERE OCEAN CLIMATE MODEL

One of the most significant consequences of climate change due to increasing concentrations of greenhouse gases in the atmosphere is a possible systematic increase in rainfall intensity over selected regions of the tropics. Despite the limited horizontal resolution, the current state-of-the-art coupled atmosphere-ocean general circulation models provide a qualitative description of the latitudinal and seasonal variations in rainfall type and intensity. In general, the model-simulated changes in the rainfall intensity under enhanced greenhouse conditions are found more statistically significant in terms of their uniformity on spatial and temporal scales. The air over the arid and semi-arid regions of India is relatively warmer during the daytime and hence has a larger water holding capacity. If a pronounced greenhouse warming were to occur over this region, the associated enhanced convective activity should lead to more extreme rainfall events. This could have strong implications for the hydrology and water resource of the region. Recently, a set of three time-dependent greenhouse warming simulations (IPCC's scenarios A and D and a sudden increase of CO2) and a reference control experiement have been performed with the Hamburg global coupled atmosphere-ocean general circulation model. The model has demonstrated substantial skill in simulating the present-day climate and its inter-annual variability over the monsoon region. Using the output of the Hamburg climate model, we have examined the possible changes in the key climatological variables over the north-west margins of Indian sub-continent over the next 100 years. The results indicate that the warming is likely to be most pronounced over the north-west margins of India (Thar Desert) by the end of next century. However, inspite of the projected temperature rise and associated enhancement in evaporation rate, the non-availability of moisture could prohibit the deep convective activity in the region leading to more extensive deserts. © 1993 Academic Press. All rights reserved.