Analysis of long-term seasonal and annual temperature trends in North Bengal, India

In the recent past, scientific modeling of climatic elements, in particular, temperature data has attained considerable importance as it affects many aspects of the environment and also indicates a clear sign of climate change. The temperature warming is mainly associated with the increasing concentration of greenhouse gases triggered by the land use and land cover changes. In the last century, exploitation of forest resource, population influx, and expansion of agricultural land has changed the natural landscape of North Bengal to a great extent. Thus the present study intends to find out long-term changes in maximum and minimum temperature for six northern districts of the state of West Bengal, popularly known as North Bengal. The non-parametric Mann-Kendall test and Theil-Sen's slope estimator reveals the presence of warming trends in both maximum and minimum temperature. Annual temperature is rising 0.006 degrees C per year and 0.007 degrees C per year at most of the districts for the maximum and minimum temperature respectively. However, the seasonal analysis of trend exposes that post-monsoon and winter temperature rise are predominantly contributing to the upward annual trend. The highest increasing trend in maximum and minimum temperature is observed at Malda (0.013 degrees C per year) in the post-monsoon and winter season respectively. Except the post-monsoon season, the minimum temperature is rising rapidly than maximum temperature across the region. Additionally, Sequential Mann-Kendall test exhibits the periodic fluctuation of trends, which aremore prominent in pre-monsoon and monsoon season.