CMIP5 based past and future climate change scenarios over South Bihar, India

The present study has been carried out to investigate the past and future rainfall and temperature change scenarios over three locations (Patna, Gaya, and Bhagalpur) falling in two agro-climatic zones (IIIa and IIIb) of South Bihar, using rainfall and temperature records from the India Meteorological Department (IMD) and Global Climate Model (GCM) data from the Coupled Model Intercomparison Project Phase 5 (CMIP5). It was observed that CMIP5 models exhibit either dry or wet bias in rainfall and warm or cool bias in temperature. Multi-model ensemble (MME) using large numbers of GCMs can produce more realistic climate information, at least at the local scale where a wide range of uncertainty is exhibited. Both model and observational records indicated moderate warming in the last century, although some models revealed higher warming. Rainfall in Patna and Gaya showed a declining trend during 1901–2015, whereas Bhagalpur has shown an increasing trend. Future projection of rainfall in CMIP5 GCMs indicated an increase of 0–25% annual rainfall in all three locations, whereas the pre-monsoon rainfall may increase at a higher rate, i.e., 0–40%, than the total annual rainfall towards the end of the 21st century. It is found that the rate of increase of annual and pre-monsoon rainfall during the 2090s could be ~2 times more than the 2030s in the study locations.