Decision Support System for Agrotechnology Transfer (DSSAT v4.5) Cropping System Model (CSM) was used to study the impact of climate change and variability on productivity of different kharif (rice, maize, jowar and bajra) and rabi crops (wheat and barley) at Varanasi. Keeping in view the observed trends in climate variability, productivity of different kharif and rabi crops were simulated under plausible synthetic climatic scenarios of changes in temperature, solar radiation and carbon dioxide. Productivity of kharif crops viz. rice, maize, jowar and bajra and rabi crops viz. wheat, and barley decreased with an increase in temperature or a decrease in solar radiation above normal. However, productivity of different kharif and rabi crops increased under expected enhanced CO2 concentrations. Highest productivity decreased in barley crop (40.7%) of rabi season and minimum in rice crop (5%) of kharif season with an increase of 3.0 0C in temperature from normal. Whereas, maximum productivity decreased in barley crop (5.0%) of rabi season and minimum in jowar crop (1.8%) of kharif season with a decrease of 2.5 per cent in solar radiation from normal. Highest productivity increase in barley crop (58.2%) of rabi season and lowest in jowar crop (4.2%) of kharif season were simulated under expected enhanced CO2 concentration of 660 ppm. The maximum decrease in productivity of barley crop (45%) in rabi season and minimum in rice crop (7%) in kharif season were simulated when a decrease in temperature by 3 0C and solar radiation by 2.5 per cent from normal. Highest counter-balance on productivity of rice crop (13%) in kharif season and lowest in barja crop (-23%) of kharif season were simulated when an increase in temperature by 3 0C from normal under expected enhanced CO2 concentration of 660 ppm.