Assessing the Trend of Climate Change in the Western Nepal

This study assesses the change in the climatic variables in the western region of Nepal. Monthly data on minimum temperature, maximum temperature and rainfall for five stations, namely, Chame, Lumle, Khudibazar, Khairenitar and Dumkauli of Manang, Kaski, Lumjung, Tanahu and Nawalparasi districts respectively, obtained from the Department of Hydrology and Meteorology (DHM) of Nepal are considered. Data availability for these three variables are not uniform and ranges earlier from 1970 to the latest 2018. To measure the change in the climatic variables, the first data were deseasonalized using classical multiplicative technique taking a moving average of twelve periods and central moving average and finally, the ordinary least squared method was applied to estimate the trend. Further, the student's t-test confirmed whether there is any significant change or time trend in the variable. The study also performed both Mann-Kendall and Sen’s slope tests for robustness check to the trend. The study result shows that maximum temperature has increased in all stations; the minimum temperature has increased in Khudibazar, Khairenitar and Dumkauli stations; and rainfall has increased in Chame and, decreased in Lumle and Khairenitar stations. Further, both maximum temperature and minimum temperature have increased faster in higher altitudes; and rainfall has decreased slower in lower altitudes. Both Mann-Kendall and Sen’s slope tests are consistent with the result. The outcome of the study which is based on local stations could be useful information for making climate change adaption strategy at the local level.