ارزیابی مدل‌ها و سناریوهای گزارش پنجم تغییراقلیم در برآورد دما و بارش ایستگاه بیرجند

Introduction According to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, the atmospheric concentrations of the greenhouse gases, i.e., carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), have increased to unprecedented levels in the last 800 000 years. An increase in the levels of GHGs (greenhouse gases) can lead to greater warming, which, in turn, can influence the world’s climate that leading to the phenomenon climate change. It is predicted that climate change induced weather extremes, extreme heat, severe drought and heavy precipitation that will have significant impacts on agriculture. In support of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC), the fifth phase of the Coupled Model Intercomparison Project 5 (CMIP5) provides a new suite of coordinated climate model experiments focusing on major gaps in understanding of historical and future climate changes. Most of the present day CMIP5 models show good performances in reproducing the present climatology, climate variability and climate extremes. In this research, the trend of rainfall changes, minimum temperature and maximum temperature of the synoptic station of Birjand during the decades and different periods from 2010 to 2100 years was studied using the data of CMIP5.
Materials and Methods This research was conducted to determine climate changes  condition in Birjand Synoptic Station located at longitude between 59˚ 7’ N and latitude between 32˚ 52’E, Iran. AR5 Global Climate Models of CSIROMK3.6, GFDL-ESM2M, GISS-E2-R, IPSL-CM5A-MR and MIROC-ESM with RCP2.6, RCP4.5, RCP6 and RCP8.5 Emission scenarios performed precipitation, minimum temperature and maximum temperature in the coming decades for the Birjand Synoptic Station.  Also, the process of changes in meteorological variables in the two form of decades-decades from 2010 to 2100 and between the next three periods of 2040-2010, 2070-2070, and 2070-2100 were taken. The changes in meteorological variables of the future periods were investigated to the base period (1970-2000) of station.
Results and Discussion The results of the study indicated that GFDL-ESM2M and GISS-E2-R models have a more accurate estimation of meteorological variables over the base and future time periods. Also The trend of precipitation from 2010 to 2100 year for various models and scenarios in different decades. However, the GFDL-ESM2M and MIROC-ESM models estimate a further decrease in rainfall between models and RCP8.5 among scenarios. Also Comparison of scenarios in all models showed that the maximum temperature in the RCP8.5 and RCP2.6 respectively with the highest and the least increase in the coming years. This increase in temperature for the scenario is RCP8.5 and the two MIROC-ESM and IPSL-CM5A-MR models will be more than 6 degrees Celsius in 2100 year in compared to 2010 year.
The maximum and minimum temperatures Changes unlike precipitation are steadily increasing  and except in the near future  period (2040-2010), in the next two periods, the models estimate the trend of temperature rise in the future relative to the base period. The MIROC-ESM and IPSL-CM5A-MR models and the MIROC-ESM and GFDL-ESM2M models estimate the highest maximum temperature and minimum temperature increase in the future compared to the base period. In Comparing periods, the far future (2070-2100) and mid-term (2040-2070) period estimated a higher increase in temperature and precipitation, respectively. The GISS-E2-R model estimates the minimum maximum and maximum temperature rise for the three periods.
Conclusions The research has determined that models are uncertain in the estimation of weather variables, which makes it difficult to select the appropriate model for use in research. Changes in scenarios are also different and the 8.5 scenario estimates higher-risk conditions that including higher temperature increases and further reductions for the future. Also, in comparison to periods, highest rainfall and temperature increase was estimated in the 2055 period and 2085 period respectively. The use of climate change Fifth Report data and the study of variations in meteorological variables over the next three periods can determinate what will happen in the future in accordance with the climate change scenarios. Also, the results of this research can be helpful in considering future weather variables in planning for management of different sectors of agriculture, water resources and environment in the future.