event of climate change, its impact on durum wheat planting and during the growing season case study: station of sararood, kermanshah

introduction climate change generally affect all economic sectors, but the agricultural sector is the most sensitive and vulnerable sector, because crops are highly dependent on climatic resource. according to the scientific evidences, climate change in the future, especially the combined effects of rising temperatures and rising co2 concentrations in the atmosphere and increase the likelihood of some events may have significant impacts on agricultural products. this paper is trying to explore the past and future trends in climate parameters, their outcomes on the sowing date and length of the growing season in rainfed wheat in the kermanshah region. materials and methods the synoptic station of sararood, kermanshah, has geographical position of 47 degrees 20 minutes western with height of 1351.6 meters above sea level. simulation of climate parameters i.e., maximum and minimum temperatures and rainfall in coming decades was carried out using the results of output the ccsm4 model under the scenario rcp4.5. the outputs of the above mentioned model is low. thus for produce the climatic data of temperature in the studied area, these outputs statistically were small-scaled in the period 2013-2039 and consequently the simulated data were used for next stages. in order to study the impact of climate change on the displacement of sowing date and change the length of growth period in the future, firstly to estimate sowing date of rainfed wheat, initial rainfall dates were extracted from the synoptic station of sararood. then, according to this definition that the sowing date can be considered when the total rainfall by early october reach to five mm, provided that fifteen days after that should not be dry, sowing date for both past and future climates was determined. in regard to the correlation between the each growth stage of wheat with the heating temperature factor, the length of growth period of wheat using the index ggd was calculated. but the remarkable thing here is that due to the lack of data on the growth period before 1988, length of growth period for base period was considered from 1988. results and discussion changes in temperature and rainfall in the past results of kendall and sen 's estimator slop indicated that changes in rainfall in most months of the year has been decreased. this trend was significant (p