Trends of Climate Change in Bangladesh: Temperature and Rainfall Variability

Abstract

Climate change is a global issue that is affecting Bangladesh , a vulnerable country in the southeast region of the world.The Earth is experiencing rising temperatures and increasing average rainfall due to two critical climate parameters ,temperature and rainfall. Although Bangladesh's contribution to climate change is minimal, it is facing the consequences of this global issue. This study focuses on the analysis of three climate parameters namely minimum temperature (Tmin), maximum temperature (Tmax) and rainfall in Bangladesh between 1968 and 2017. The study finds that the average minimum temperature in Bangladesh has increased at a rate of 0.19° C per decade, with an increase of 0.95 C between 1968 to 2017. The temperature is expected to rise by 0.63 C by 2050. Moreover, the average minimum temperature during the premonsoon season has increased at a rate of 0.21 ° C per decade and by 0.69 ° C in fifty years. During the monsoon season, the temperature has increased by 0.63 ° C over the past fifty years. Similarly, the average temperature during the post-monsoon has also risen, increasing by 0.1 C over fifty years at a rate of 0.02  C. This study also indicates that the average temperature during the dry season has risen by 0.84 C over the past fifty years at a rate of 0.17  C. The minimum temperature in the climatic zonal has also increased, with the northeastern zone receiving the highest minimum temperature of 1.03  C over the past fifty years at a rare of 0.26  C. The western zone received the lowest average minimum temperature of 0.60  C at a rate of 0.12  C, while the southeastern zone received 0.78  C,the northern part of the northern region received 0.64  C, the southwestern zone received 0.65  C and south-central zone received 1.35  C. During the last fifty years (1968-2017), the average maximum temperature of Bangladesh has been observed to be on the rise.This study revealed that the temperature has increased by 0.65  C, at a rate of 0.13  C per decade during that period. The temperature during the pre-monsoon period has increased by 0.58  C at V a rate of 0.12  C per decade, during monsoon by 1.43  C at a rate of 0.29  C per decade, during post-monsoon period by 1.16  C at a rate of 0.23  C and during the dry or winter season by 0.40  C at a rate of 0.08  C per decade. Furthermore, the study found that the average maximum temperature of the south-eastern zone has increased by 0.33  C over the last fifty years at a rate of 0.067  C per decade. The north-eastern zone experienced an increase of 1.57  C at a rate of 0.31  C per decade while the north-western zone had an increase 0.78  C at a rate of 0.156  C per decade. The western zone had an increase of 0.43  C at a rate of 0.08  C per decade, the south-western zone had an increase of 0.75 C at a rate of 0.15 C per decade, and the south-central zone had an increase of 0.94  C at a rate of 0.19  C. The only exceptional was the northern part of the northern region, where the average maximum temperature was observed to be decreasing. Over the last fifty years,the temperature there decreased by -1.9  C at the rate of -0.38  C per decade. The average total rainfall of Bangladesh has increased 5125 mm in the last fifty years at a rate of 1025 mm per decade. This increase has been observed in all seasons including premonsoon, monsoon, post-monsoon and dry. During premonsoon, the rainfall increased by 765 mm at a rate of 153 mm per decade, during monsoon it increased by 3595 mm at a rate of 719 mm per decade, during post-monsoon it increased by 780 mm at a rate of 156 mm, during dry/winter the average total rainfall increased by 150 mm at a rate of 30 mm per decade. In terms of climatic zones, the south-western zone received the highest amount of rainfall at 12195 mm at a rate of 2439 mm per decade. The north-eastern zone received 5320 mm at a rate of 1064 mm per decade while the northern part of the northern region received 3115 mm at a rate of 623 mm per decade. However, the north-western received less rainfall of -4205 mm at a decreasing rate of -841 mm per decade.Similarly the western zone received less rainfall of -255 mm at a rate of -51 mm per decade. The South-western zone received 2210 mm of rainfall at a rate of 442 mm per decade, while the south-central zone received -756mm at a rate of -153 mm, per decade.