Investigation Into the Sea Level Rise as Fallout of Climatic Change: Case Study of the Coast of Bangladesh

Abstract

Several thousands of years have so far been elapsed since its emergence as an alluvial land, the today’s land of Bangladesh exhibits the experiences almost all the natural calamities, hazards and disasters in its geographical perspectives. Magnitudes of occurrences of the natural disasters have always been inversed and exemplified now a days due to the immense multiplications of the human population in a comparatively smaller area. Needless to say, that the pressure of ever-increasing population in Bangladesh has exerted innumerable adverse effects on the natural settings of the region and often worsening the situation appearing as some complex and intricate anthropogenic hazards and disasters in Bangladesh. To evaluate regional and local climate settings and its trend is a complicated task and should give due consideration to the consistency, homogeneity and continuity of data, unequal length of available data, outliers and extreme values in available records and appropriate statistical and mapping tools. Most of the CMIP5 and earth system model simulations for AR5 WRI were performed with prescribed CO2 concentrations reaching 421 ppm (RCP2.6), 538 ppm (RCP4.5), 670 ppm (RCP6.0) and 936 ppm (RCP 8.5) by the year 2100. In this research I found RCP4.5 a strong correlation regression R2 = 0.917 with temperature and sea level rise in Bangladesh among RCPs. Annual average mean, maximum (mean) and minimum (mean) temperature found increasing trend during 1948-2016 is 0.82 0C, 0.96 0C and 1.41 0C per century whereas in the period of 1987-2016 is 0.85 0C, 2.38 0C and 1.24 0C per century respectively; but in seasonal, period of 1948-2016 is increasing trend and period of 1987-2016 increasing and decreasing both trends are present. During 1948-2016 SNHT showed that out of 35 stations, there are 22, 21 and 19 common stations in annual average mean, maximum (mean) and minimum (mean) temperature increasing trend respectively with high significant. Decadal variation of premonsoon, monsoon, post-monsoon and winter rainfall showed that increasing trends are 52.32 mm, 210.02 mm, 26.06 mm and 4.13 mm per climatic period respectively. The annual seasonal increasing trend in the pre-monsoon, monsoon, post-monsoon and winter were found 5.21 mm, 20.93 mm, 2.61 mm and 0.39 mm/yr respectively, at the same time most of the monthly normal rainfall having the same trends. A SimCLIM simulation based on baseline 1995 temperature that, the global temperature showed the lowest and height temperature are -44.52 0C and 30.27 0C. In Bangladesh average mean, maximum (mean) and minimum (mean) temperature from baseline varied 19.00 0C-29.10 0C, 25.80 0C-34.40 0C and 12.20 0C-26.20 0C respectively and precipitation is 7.00 mm - 381.00 mm. Annual average mean, maximum (mean) and minimum (mean) temperature for observed and model projected values are 25.90 0C (baseline), 26.58 0C,vii 27.20 0C, 27.81 0C and 28.46 0C; 30.67 0C (baseline), 31.33 0C, 31.93 0C, 32.55 0C and 33.16 0C; 21.18 0C (baseline), 21.88 0C, 22.53 0C, 23.22 0C and 23.92 0C respectively by the year of baseline, 2025, 2050, 2075 and 2100. In this research I found overall mainland shoreline and island shoreline net loss/gain are -14.79 km and 579.20 km respectively. Island shoreline (positive value) bigger than mainland shoreline (negative value). 1910s-2015 mainland and island area in total net gain 1178.55 km2 and 288.75 km2 respectively. Overall Bangladesh coastal zone obtain 1467.30 km2 area in this 105 year. In this research I also found the average sea level rise rate in Bangladesh is 2.72 mm/yr whereas global average 5.87 mm/yr which is about two times more than Bangladesh average. Khepupara is the height increasing rate by 13.32 mm/yr and Sonapur is the lowest decreasing rate by -11.59 mm/yr. Three regions, Eastern rate is 2.80 mm/yr, Central rate is -1.04 mm/yr and Western rate is 6.39 mm/yr. Eastern and Western region is higher rate than Central region where Central region is negative in trend. Except Teknaf, the trend in Bangladesh average, only 1.63 mm/yr, this rate is very little compare to the global average. In this study the rise in Global Mean Sea Level for the period of 2025-2100, based on process-based models is likely to be in the range 10.33-53.33 cm for RCP 4.5, 10.00-55.33 cm for RCP 6.0 and 10.00-75.00 for RCP 8.5. If we encompass 2015 is the base year and its trend go through the same rate then in the year of 2025 Bangladesh will be reach 27.20 mm from 2015; and 2050, 2075 and 2100 will be 95.20 mm, 163.20 mm and 231.20 mm respectively. Calculate the global rate, in the year of 2025 world will reach 63.90 mm from 2015; and 2050, 2075 and 2100 will be 223.65 mm, 383.40 mm and 543.15 mm respectively