Abstract
Temperature is one of the important climatic factors in agriculture, any change of which can affect the process of growth and production of agricultural products. Today, due to the occurrence of climate change, the importance of examining this issue, especially in agriculture, in terms of the impact on the food security of the people of the world, has become particularly important. Based on this, in this research, using the variables of minimum temperature, maximum temperature and average temperature in 17 meteorological stations in the northwest and west of Iran in the time period of 1985–2019, 5 cooling indices and 6 heating indices (at different temperature thresholds) were calculated and then trend analysis was done using two methods, Mann-Kendall (along with Sen’s slope estimator) and Innovative Trend Analysis (ITA). Based on the analysis, it was found that the cooling indices in most of the stations have undergone a time shift while reducing the duration of the period. From the point of view of heating indices, in most stations, along with increasing the length of the growing season at different thresholds, thermal stress has also occurred, which has a negative effect on the growth of crops. Investigations showed that the two stations of Maragheh (in the north of the region) and Khorram Abad (in the south) had the most changes. It was also found that the ITA and the Mann-Kendall methods have little difference in showing the type of trend and the ITA shows the changes in a more reasonable way.