Analysis of Seasonal Climate Variability and Future Projection by Using CCSM4 Model for Metropolitan Islamabad, Pakistan

Abstract

Climate change has an enormous effect on the environment and natural resources. Changes in rainfall and temperature are major parameters of climate affecting the environment. To assess the spatial and temporal dynamics of meteorological variables in the context of changing climate, mainly in countries where rainfed agriculture prevails, it is crucial to assess climate-induced changes. Variation in quantities such as precipitation and temperature is often assessed by detecting and characterizing trends in available and projected meteorological data. The objective of this study is to determine the recent, and long-term trends in seasonal precipitation and mean seasonal air temperature for Islamabad. This study is carried out for Islamabad regarding spring season (March, April, May), summer season (June, July, August), autumn season (September October, November), and winter season (December, January, February). The study analyzed trends in weather time series (air temperature and rainfall) data from 1981 to 2010 as the observed period and also analyzed projected changes in mean seasonal temperatures and precipitation trends for the near future time period (2021-2039), mid future time period (2040-2069) and far future time period (2070-2099) using the Community Climate System Model (CCSM4) at -0.25 X 0.25° horizontal atmospheric resolution. Projected changes in mean annual rainfall for the twenty-first century was calculated relative to the base line period using two possible future levels of atmospheric greenhouse gases concentration referred to as Representative Concentration Pathways (RCPs) 4.5 w/m² and 8.5 w/m² Cool and wet as well as hot and dry season showed a significant decreasing trend in precipitation and increasing trends in temperature. The projected changes in mean seasonal rainfall pattern show that rainfall amount decreases throughout all the time periods, te. (2021-2039), (2040-2069), and (2070-2099) over the Islamabad. It is anticipated that if the projected changes in mean seasonal ramfall pattern occur in the future, it may lead to stress on water-dependent sensitive sectors in the region. The results of the study reaffirm climate change is happening, therefore, proper adaptation measures should be employed to reduce the vulnerability to climate change in the area because of its significance.