SPECIAL SECTION: CLIMATE CHANGE AND INDIA CURRENT SCIENCE, VOL. 90, NO. 3, 10 FEBRUARY 2006 334 *For correspondence. (e-mail: kolli@tropmet.res.in) High-resolution climate change scenarios for India for the 21st century K. Rupa Kumar*, A. K. Sahai, K. Krishna Kumar, S. K. Patwardhan, P. K. Mishra, J. V. Revadekar, K. Kamala and G. B. Pant Indian Institute of Tropical Meteorology, Pune 411 008, India A state-of-art regional climate modelling system, known as PRECIS (Providing Regional Climates for Impacts Studies) developed by the Hadley Centre for Climate Prediction and Research, is applied for India to develop high-resolution climate change scenarios. The present- day simulation (1961–1990) with PRECIS is evaluated, including an examination of the impact of enhanced resolution and an identification of biases. The RCM is able to resolve features on finer scales than those re- solved by the GCM, particularly those related to im- proved resolution of the topography. The most notable advantage of using the RCM is a more realistic repre- sentation of the spatial patterns of summer monsoon rainfall such as the maximum along the windward side of the Western Ghats. There are notable quantitative biases in precipitation over some regions, mainly due to similar biases in the driving GCM. PRECIS simula- tions under scenarios of increasing greenhouse gas concentrations and sulphate aerosols indicate marked increase in both rainfall and temperature towards the end of the 21st century. Surface air temperature and rainfall show similar patterns of projected changes under A2 and B2 scenarios, but the B2 scenario shows slightly lower magnitudes of the projected change. The warming is monotonously widespread over the country, but there are substantial spatial differences in the projected rainfall changes. West central India shows maximum expected increase in rainfall. Extremes in maximum and minimum temperatures are also ex- pected to increase into the future, but the night tem- peratures are increasing faster than the day temperatures. Extreme precipitation shows substantial increases over a large area, and particularly over the west coast of India and west central India. Keywords: Regional climate model, downscaling, re- gional climate projections, Indian climate, Indian monsoon. HUMAN activities since the beginning of the industrial revo- lution have led to unprecedented changes in the chemical composition of the earth’s atmosphere. We now have credible evidence to show that such changes have the potential to influence earth’s climate 1 , though it is difficult to clearly delineate the characteristics of climate change associated with natural and anthropogenic forcings due to complex interactions within the climate system. Although meteoro- logical data compiled over the past century suggest that the earth is warming, there are significant differences at re- gional levels. Climate variations and change, caused by external forcings, may be partly predictable, particularly on the larger (e.g. continental, global) spatial scales. Because human activities, such as the emission of greenhouse gases or land-use change, do result in external forcing, it is be- lieved that the large-scale aspects of human-induced climate change are also partly predictable. However, the ability to actually do so is limited because we cannot accurately predict population change, economic policy, technological development, and other relevant characteristics of future human activity. In practice, therefore, one has to rely on care- fully constructed scenarios of human behaviour and deter- mine climate projections on the basis of such scenarios. The Third Assessment Report (TAR) of the IPCC (Inter- governmental Panel on Climate Change) notes that the current versions of atmosphere–ocean general circulation models (AOGCMs) have generally well simulated the features of the present-day climate at the large and conti- nental scale 1 . Though the large inter-model differences on a regional scale with the consequent uncertainties is a cause for concern, an encouraging sign is that the AOGCMs have been showing steady improvement over the recent past. The effects of climate change are expected to be greatest in the developing world, especially in countries reliant on primary production as a major source of income. One of the high priorities for narrowing gaps between cur- rent knowledge and policymaking needs is the quantita- tive assessment of the sensitivity, adaptive capacity and vulnerability to climate change, particularly in terms of the major agro-economic indicators in the developing countries. To systematically pursue such assessments, the most fundamental requirement is the availability of reli- able estimates of future climatic patterns on the regional scale, which can be readily used by different impact assess- ment groups. This needs a systematic validation of the climate model simulations and development of suitable regional climate change scenarios, estimations of the as- sociated uncertainties. Climate scenarios often make use of climate projections (descriptions of the modelled response of the climate system to scenarios of greenhouse gas and aerosol concentrations or some other hypothetical forcings on the climatic com-