Greenhouse gas emissions (GHG) were simulated from commonly used crop rotations in eastern Poland for conventional and conservation tillage systems. We used denitrification-decomposition (DNDC) model baseline climate conditions and two future climate scenarios (2030 and 2050). Analyzed cropping systems included corn, rapeseed, and spring and winter wheat. It has been shown that an increase of temperature and decrease of precipitation can reduce net global warming potential (GWP) by 2% in the 2030 climate scenario and by 5% in the 2050 scenario in conventional tillage with reference to the baseline scenario. In the case of conservation tillage, a reduction of GWP by 5% and by 10% was estimated. The use of conservation tillage results decrease the GWP by 17-19% in the baseline scenario, in the 2030 scenario by 16-18%, and in the 2050 scenario by 15-17%. It also has been shown that change in climate conditions has declined biomass production of winter wheat and corn, which may suggest that a larger area would be needed for these crops to maintain production at the same level.