Assessment of Climate Change Risk Impacts on Potential Evapotranspiration; Case Study Shahrood Region

In recent years human activities induced increases in atmospheric carbon dioxide (CO2) which caused global warming and climate change. Temperature increasing resulting from climate change lead to increase the evapotranspiration which play key role in determination of crop water requirement. Potential evapotranspiration (ETo) was calculated using Ref-ET model and FAO56 formula to assess the climate change impacts on ETo for the baseline (1971-2000) and future (2016-2045 and 2070-2099) periods in Shahrood city. Hence, climate change scenarios were generated from 13 coupled atmosphere-ocean general circulation models (AOGCM) under two greenhouse gases emission (GHG) scenarios (A2 and B1) and then was downscaled using LARS-WG model. The calculated ETo for different climate change scenarios were compared with those of baseline period. Result showed that in first future period (2016-2045), mean of ETo is increased about 4.5 percent for both A2 and B1 scenarios. In 2070-2099 period, mean of ETo is increased about 15 and 8 percent for A2 and B1 scenarios, respectively. It was also found that ETo is increased more in warmer months in comparison with cold months.