Agriculture based economy of India and the farmer’s high reliance on rainfall, led the scientific community, policy makers and the public, more concerned about the climate change issue. So, a detailed study has been undertaken to investigate the past and current climate, and future projection of climate change in India. More emphasis has been put on the eastern part of India, i.e., over Gangetic West Bengal and its neighbourhood, where a detailed high-resolution future climate change scenarios have been constructed followed by an assessment of the implications on agriculture sector.
Statistical analyses reveal that significant warming trends are present in the winter and postmonsoon seasons in all-India scale, which is also reflected in the annual mean temperature. While rainfall series shows insignificant trend though short-term fluctuations exist. The eastern region follows a similar increasing temperature trend (1oC /100 years), slightly higher than that of all-India scale. Warming trend is detected from the Fifties in case of the winter season while the Eighties for the postmonsoon season over this part of the country. However, unlike all-India scale, the region has experienced significant recent decreasing trend in the monsoon rainfall.
Future projection in the period 2010-2039, as derived from the GCMs integrations due to greenhouse gas forcing, reveals warming in all-India scale irrespective of the seasons. While inclusion of sulphate aerosols, reduced the warming slightly. An amount of 0.3 - 0.6 ± 0.2oC per oC global mean temperature change is noticed in the composite scenarios, with more warming in the northern India and less warming in the southern India. However, unlike mean temperature, pockets of positive as well as negative changes in rainfall are observed in different parts of the country. Composite scenarios also reveal that rainfall changes are less. It is due to the fact that when a model projects a positive change over a small region, the other model may project negative change, resulting a less change of rainfall over the region. This also indicates the inability of the GCMs to explore the spatial details. To capture such sub-grid scale details, several techniques are used. Perhaps, the commonly used and simple technique is statistical downscaling. Using this technique, a warming of 0.2-0.8 oC has been projected, which is higher than that obtained from the all-India scenarios over the same region. Moreover, the projection indicates more warming and less changes of rainfall (-3 to +1%) in the monsoon season, unlike the all-India scale. All the above results are expressed per oC global mean temperature change. The global mean temperature change is about 2.5oC for the GCMs, which are used for the construction of high-resolution scenario development over the study area. So, projection for 2010-2039 indicates a warming of about 0.5-2.0oC. Such a change can alter the productivity of rice as assessed through Oryza 2000, a crop simulation model for rice. GWB and its neighbourhood is expected to experience nominal change in the either sides as rice production increases by about 10% with 1oC rise in temperature and falls by 30% with a rise of temperature by 2oC. However, the same study should be carried out under different environmental conditions at different locations of the study area. It may be extended to consider the other agricultural products so as to have a comprehensive picture on the implications on agriculture sector as a whole.