Analysis of Climate Change Induced Parameters of South-Eastern Coastal Islands of Bangladesh: Comparison from 1977 to 2017

Climate change is one of the biggest threats for the new millennium, and Bangladesh is considered as "Poster Child" as an impact on climate change in the world. The main focus of this study is to investigate the changing pattern of climate parameters, particularly temperature, rainfall, humidity, cloud coverage, and wind speed in two coastal islands of the southeastern coast of Bangladesh from 1977 to 2017. The linear regression model described that the temperature in Kutubdia and Sandwip islands was 0.0298 and 0.0444 times increased from 1977 to 2017. Besides, rainfall patterns in Kutubdia decreased by 0.4083, and Sandwip Islands increased by 0.875 every year from its previous counterpart. The humidity level also increased due to the rise of temperature and water availability for evaporation from irrigation. Moreover, significant changes in wind speed and the cloud coverage rate in the Island areas increased with the increasing value of temperature and humidity. It also means the rainfall rate increases with cloud cover in the sky. However, the study found decreasing rates of bright sunshine in the Island areas. The declining rate of sunshine is very high and is a matter of great concern for the agriculture and health sectors in particular areas. Therefore, the community's concept of climate parameters, association, and extremes is well apparent. Identify poor land use planning as the primary anthropogenic driver of the change, and they advocated boosting the capacity of linked fields that are in danger owing to climate change. To conclude, the coastal inhabitants recommended that taking preparedness would be easier if the information transmitted through quicker and reliable sources such as news broadcasts, phone messages, or the internet. Ac c pt ed M nu sc rip t AUTHOR ACCEPTED MANUSCRIPT – JOURNAL OF MULTIDISCIPLINARY APPLIED NATURAL SCIENCE


INTRODUCTION
Climate, as opposed to weather, is the long-term (usually about 30 years) generalized pattern of weather conditions, including temperature, rainfall, humidity, wind, pressure, and cloudiness, in a particular area. However, in addition to the averages, the deviation from the averages, or seasonal oscillations, as well as the weather extremes, are essential components of climate. The seasonal oscillations and deviations are very pronounced in Bangladesh because of the monsoon type of climate prevailing here. In the study, 40 years long term average of the seasonal cycle of climate parameters is used for assessing the changing pattern of climate data in the three coastal islands. Forty years of data are considered long enough to calculate an average that is not affected by year-to-year variability [1]- [3].
Climate change poses a significant threat for Bangladesh, particularly the projected climate change effects include sea-level rise, higher temperature, enhanced monsoon precipitation, and run-off, potentially reduced dry season precipitation, and increase in cyclone intensity in the coastal region. Those threats would induce severe impediments to the socio-economic development of Bangladesh including coastal areas. A subjective ranking of key climate change effects for coastal Bangladesh identifies cyclone and sea-level rise as being of the highest priority in terms of severity, certainty, and urgency of impact. Among the 64 districts of Bangladesh, 26 districts are evidence of climate displacement in Bangladesh.
Climate Displacement is a major consequence of climate change in Bangladesh because due to climate change-induced natural disasters, people are losing housing and land from their origin and are forced to be displaced in new areas to survive [4]- [6]. Bangladesh ranked 7 th in the Global Climate Risk Index 2021, which said it was the seventh-worst hit by climate change-induced natural disasters between 2000 and 2019, where the country lost 15,000 people, damaged the economic losses worth $ 3.72 billion, and experienced 185 extreme weather events because of climate change [7]. At present, Bangladesh has been called the "ground zero" of climate change. However, the impact of 'climate change' is reasoning an increase in the frequency and severity of these disasters adversely affecting agriculture, water and sanitation, infrastructure, and health. Bangladesh is having a coastal area of 47,211 sq. km, which is 32 % of its entire land. The coast of A c c e p t e d M a n u s c r i p t AUTHOR ACCEPTED MANUSCRIPT -JOURNAL OF MULTIDISCIPLINARY APPLIED NATURAL SCIENCE Bangladesh is approximately 710 km long and has very low-lying flat land. 62 % of the land has an elevation of fewer than three meters, and 86% have less than five meters [8]- [10].
The Coastal zone of Bangladesh is comprised of 19 administrative districts stretching into 147 Upazilas, delineated based on the tidal fluctuations, cyclone, storm surge risk, and salinity intrusion. Among the Upazilas, 48 from 12 districts face the coast or lower estuary and are known as exposed coast, and the rest 99 Upazilas that are behind the exposed coast is known as interior coast [11]- [13]. The climate of Bangladesh is conquered by seasonal reversal of winds from the southwest during summer and from the northwest during winter, consequences for wet southwest monsoon and dry north-west monsoon respectively. The South-Eastern coastal area of Bangladesh is comparatively susceptible to cyclones, tidal floods, coastal erosion, heavy rainfall that varies from year to year, both in terms of intensity and duration. Several studies were conducted on climatic trends and climate change impacts in the coastal region of Bangladesh. Analysis of global observations of surface temperature shows that there has been a warming of about 0.6 °C over the past hundred years [14]. The trend is toward a more substantial increase in minimum than in maximum daily temperatures.
The reason for this difference is linked to associated increases in low cloudiness and aerosol effects as well as the enhanced greenhouse effect. Changes in precipitation and other components of the hydrological cycle are determined more by changes in the weather systems and their tracks than by changes in temperature. Because such weather systems are so variable in both space and time, patterns of change in precipitation are much more complicated than patterns of temperature change. Precipitation has increased over land in the high latitudes of the Northern Hemisphere, especially during the cold season [15] [16].
From the record of temperature data over the last 100 years in Bangladesh, it is found that the rate of temperature increment found higher than the present which is 0.5 °C. Another study shows the mean annual temperature of Bangladesh has increased between 1895 and 1980 at 0.3 °C over the past two decades and from 1900 to 2017, the rate increased by nearly 0.80 °C. In general, the associated degree of the increasing trend is found in both summer and winter temperatures [17]- [19]. There was no significant trend within the annual rainfalls of Bangladesh. The study on the long-term monsoon rainfall pattern at 12 stations in Bangladesh found no overall trend in seasonal total rainfall but there detected some trends in monthly rainfalls [20].
Climate analysis results are also dependent on the quality of the datasets, above all on their homogeneity. This study intends to understand the trend of climate parameters such as temperature, rainfall, humidity, cloud coverage, sunshine, and wind speed over the 40 years

RESULTS AND DISCUSSIONS
Bangladesh Meteorological Department (BMD) provided the climate data for Kutubdia and Sandwip upazila over the period 1977-2017. The climate data comprised monthly, seasonal, and annual average maximum, minimum climate parameters over the period. The annual total rainfall of the study was observed. The pattern of the total rainfall for the period of 1977-2017 was irregular but increased significantly from 2015 to 2017. For time-series data analysis of climatic components, particularly rainfall, the three climatic hotspot area's data were intended and analyzed. The following section has been depicted the real scenarios of rainfall variability in three different geographical locations. Figure 1 1973, 1976, 1978, 1979, 1980, 1981, 1982, 1984, 1986 and 2000. It was noticeable that in 1979 rainfall was abruptly decreased and severe drought caused widespread damage to crops. The consecutive droughts of 1979 directly affected about 42% of cultivated land, 44% of the population, and reduced rice production by an estimated 2 million tons and it was one of the severest in recent times [25]. The increasing trends in annual maximum rainfalls in Kutubdia and Sandwip upazila are eventually the path of traverse of the southwestern monsoon wind. This indicates that the intensity of heavy rainfall may have increased along the main route of the monsoon wind. Relative humidity (RH) is another important climatic factor and is also responsible for the formation of any kind of unsteady condition.
Study on this parameter is also important because temperature and RH relate good influence on the formation of the cyclone [26]- [28].
The study found significant changes in wind speed over the study areas.  (Table 1). A c c e p t e d M a n u s c r i p t

CONCLUSIONS
The finding of the study describes the changing pattern of annual climate parameters like temperature, rainfall, humidity, bright sunshine, cloud coverage, and wind speed for Kutubdia paper are inadequate to remark about the global climate change impact on climate trends in the south-eastern islands of Bangladesh. Increased temperature, rainfall, and monsoon precipitation are probably responsible for the frequent tropical disease outbreak and raised sternness and incidence of hydrological different disasters. On the other hand, amplified rainfall could assist to remain the groundwater in balance and agriculture production in the coastal areas. This is anticipated that the climate trend maps and the research finding will support to outline of the planning of climate change policy perspective in Bangladesh and to understand the regional climate changes to realize the broad features of the Asian coupledland-atmospheric system.