Decision Support System for Agrotechnology Transfer (DSSAT v4.6.1) was used to study the impact of climate change and variability on productivity of different monsoon (pigeonpea and groundnut) and winter season crops (chickpea, mustard, tomato and potato) at Varanasi. Keeping in view the observed trends in climate variability, productivity of different cash crops were simulated under plausible synthetic climatic scenarios of changes in temperature and carbon dioxide. Productivity of pigeonpea and groundnut in monsoon season and mustard, tomato and potato in winter season decreased with an increase in temperature. Productivity of different pulse, oilseed and vegetable crops increased under expected enhanced CO2 concentrations. Highest productivity decreased in pigeonpea crop (96.0%) in monsoon season and minimum in tomato crop (4.0%) in winter season with an increase of 3.0 °C in temperature above normal. Highest productivity increase in mustard crop (164.0%) in winter season and lowest in pigeonpea crop (33.0%) in monsoon season were simulated under projected enhanced CO2 concentration of 760 ppm. Highest counter-balance in productivity of mustard crop (150%) followed by tomato crop (81%) during winter season and lowest in pigeonpea crop (99%) during monsoon season were simulated when an increase in temperature by 3.0 °C above normal under projected enhanced CO2 concentration of 760 ppm.