Analyzing the two-dimensional plot of the interannual climate variability for detection of the climate change in the Large Karoun River Basin, Iran

Abstract

In most studies on climate change, the first problem often faced by the researcher is detecting the climate change of the study area during the past periods and attributing it to the greenhouse gases. In this study, an attempt has been made to introduce a method for detecting the climate change during the past periods in regional scale and attributing it to greenhouse gases with regard to climate processes in a region. For this purpose, at first it is necessary to calculate the interannual variability range of the region climatic variables, resulting from the interaction between the climate systems of the ‘earth’ (atmosphere, biosphere, etc.). Hence, long-term statistics (1000 years) of the temperature and precipitation, resulting from control run (fix greenhouse gases) of AOGCM models (HadCM3 and CGCM3), were used for Large Karoun River Basin. Then, based on the two-variant normal distribution, the interannual climate variability range of the study area was plotted as two-dimensional temperatureprecipitation graphs. Next, the annual temperature and precipitation anomaly values of the observation stations in different regions of Large Karoun River Basin were compared with the region interannual variability range for detecting the climate change of the study area during the past and attributing it to greenhouse gases. The results show increase in temperature and decrease in precipitation trends, denoting the fact that the temperature variable has been influenced by the climate change. So, in all regions of the Large Karoun River Basin, the final years of the period (1971 to 2009) have almost been located outside the interannual climate variability range, indicating the effect of climate change on the climatic variables of the said years.

Key words: Interannual climate variability, detecting the climate change, AOGCM models, Large Karoun River Basin.