摘要：The goal of limiting the increasing global mean temperature below 2.0 and possibly 1.5 ºC, was decided in the Paris Agreement of 2015. It is therefore important to understand the climate risk and impacts associated with 1.5 and 2.0 ºC additional warming scenarios. The current study investigates the impacts of 1.5 and 2.0 ºC additional warming on wheat yield in Pakistan using a gridded modeling approach. The generated climate data by four GCMs under 1.5 and 2.0 ºC were acquired from the Half a Degree Additional Warming, Prognosis and Projected Impacts (HAPPI) scenarios group. The CERES-Wheat model was calibrated and evaluated using field data and then applied to the entire region of Pakistan. Model calibration results showed a close association between observed and simulated wheat yield with an error ranging from 0.52 to 1.36%. Climate change projections indicated that the mean temperature is expected to rise by 0.46 and 1.44 ºC in the 1.5 and 2.0 ºC additional warming scenarios in the GCMs, respectively. The spatial variations of precipitation range from –22.4 to 42.6% and 4.6 to 34.1% under the 1.5 and 2.0 ºC HAPPI scenarios, respectively. Higher precipitation was recorded in northern Pakistan as compared to central and southern Pakistan. The projected changes in temperature and precipitation will decrease the wheat yield by 3.2 and 4.7% in Punjab, 17.8% and 13.8% in Sindh province under 1.5 and 2.0 ºC additional warming, respectively. However, the wheat yield will increase by 4.7 and 13% in Khyber Pakhtunkhwa and 9.4 and 15.3% in Baluchistan under 1.5 and 2.0 ºC additional warming, respectively.
