The Climate of Bangladesh

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The Climate Of Bangladesh
Bangladesh has a subtropical monsoon climate characterized by wide seasonal variations in rainfall, moderately warm temperatures, and high humidity. Regional climatic differences in this flat country are minor. Three seasons are generally recognized: a hot, humid summer from March to June; a cool, rainy monsoon season from June to October; and a cool, dry winter from October to March. In general, maximum summer temperatures range between 32°C and 38°C. April is the warmest month in most parts of the country. January is the coldest month, when the average temperature for most of the country is 10°C. Winds are mostly from the north and northwest in the winter, blowing gently at one to three kilometers per hour in northern and central areas and three to six kilometers per hour near the coast. From March to May, violent thunderstorms, called northwesters by local English speakers, produce winds of up to sixty kilometers per hour. During the intense storms of the early summer and late monsoon season, southerly winds of more than 160 kilometers per hour cause waves to crest as high as 6 meters in the Bay of Bengal, which brings disastrous flooding to coastal areas. Heavy rainfall is characteristic of Bangladesh. With the exception of the relatively dry western region of Rajshahi, where the annual rainfall is about 160 centimeters, most parts of the country receive at least 200 centimeters of rainfall per year (see fig. 1). Because of its location just south of the foothills of the Himalayas, where monsoon winds turn west and northwest, the region of Sylhet in northeastern Bangladesh receives the greatest average precipitation. From 1977 to 1986, annual rainfall in that region ranged between 328 and 478 centimeters per year. Average daily humidity ranged from March lows of between 45 and 71 percent to July highs of between 84 and 92 percent, based on readings taken at selected stations nationwide in 1986 (see fig. 3; table 2, Appendix). About 80 percent of Bangladesh's rain falls during the monsoon season. The monsoons result from the contrasts between low and high air pressure areas that result from differential heating of land and water. During the hot months of April and May hot air rises over the Indian subcontinent, creating low-pressure areas into which rush cooler, moisture-bearing winds from the Indian Ocean. This is the southwest monsoon, commencing in June and usually lasting through

September. Dividing against the Indian landmass, the monsoon flows in two branches, one of which strikes western India. The other travels up the Bay of Bengal and over eastern India and Bangladesh, crossing the plain to the north and northeast before being turned to the west and northwest by the foothills of the Himalayas (see fig. 4). Natural calamities, such as floods, tropical cyclones, tornadoes, and tidal bores--destructive waves or floods caused by flood tides rushing up estuaries--ravage the country, particularly the coastal belt, almost every year. Between 1947 and 1988, thirteen severe cyclones hit Bangladesh, causing enormous loss of life and property. In May 1985, for example, a severe cyclonic storm packing 154 kilometer-per-hour winds and waves 4 meters high swept into southeastern and southern Bangladesh, killing more than 11,000 persons, damaging more than 94,000 houses, killing some 135,000 head of livestock, and damaging nearly 400 kilometers of critically needed embankments. Annual monsoon flooding results in the loss of human life, damage to property and communication systems, and a shortage of drinking water, which leads to the spread of disease. For example, in 1988 two-thirds of Bangladesh's sixty-four districts experienced extensive flood damage in the wake of unusually heavy rains that flooded the river systems. Millions were left homeless and without potable water. Half of Dhaka, including the runways at the Zia International Airport--an important transit point for disaster relief supplies--was flooded. About 2 million tons of crops were reported destroyed, and relief work was rendered even more challenging than usual because the flood made transportation of any kind exceedingly difficult. There are no precautions against cyclones and tidal bores except giving advance warning and providing safe public buildings where people may take shelter. Adequate infrastructure and air transport facilities that would ease the sufferings of the affected people had not been established by the late 1980s. Efforts by the government under the Third Five-Year Plan (1985-90) were directed toward accurate and timely forecast capability through agrometeorology, marine meteorology, oceanography, hydrometeorology, and seismology.

Primary concept on Climate Change
The planet named the Earth is becoming hotter day by day. This global warming is bringing the problem like climate change and sea level change. For the influence of global warming advanced sea water will submerge the coastal area with saline water and will increase the natural calamity day by day. Climate is changeable through out the world. World climate has changed in past, still it is changing and it will change in future. In past climate change was climate change was a slow and natural process and today climate change is the result of human activities against the nature. In the eighty's of last century, world meteorologists have confirmed that global warming is increasing fast. According to the third Assessment Report (TAR) of Inter Governmental Panel on Climate Change (IPCC) which is established by the combined effort of World Meteorological Organization (WMO) and United Nations Environmental Programme (UNEP) the temperature of the earth's surface is increasing by 0.6°C in 100 years. And the scientists have blamed the human activities as the main reason for this global warming. This global warming has changed the total climate system.

Scientists have got the proof of the fluctuation of the earth's temperature in last one millennium (1000 B.C to 2000 B.C). Based on the information of last 1000 years, the temperature of the northern hemisphere is irregular and has become cool. By this time temperature has increased in 11th to 14th century. Again temperature has decreased from 15th to 19th century. World temperature has fluctuated from 0.4°C to 0.8°C in last 140 years (1861 to 2000). In last 100 years (1901 to 2000) earth's surface temperature has increased from 0.6°C +/_ 0.2°C (+/- 0.2°C means, minimum 0.4°C and maximum 8°C). This temperature has changed in two phases. From the year 1910 to year 1945 is the first phase and the year 1976 to year 2000 is the second phase. Analyzing the temperature of the Northern Hemisphere scientists got that in the last 1000 years ( 1901 to 2000) temperature has increased most and the last decade ( 1991 to 2000) of the last century was the warmest decade and 1998 was the warmest year of the last decade ( TAR, WGL, IPCC,p-13). The tendency of global warming is increasing day by day. For example, after 1998, 2002 was the second warmest year. Scientists are suspecting that in next 100 years warming would be two to ten times faster. This kind of global warming is beyond the previous world history. One of the main causes of the global warming is the use of fossil fuel. Beside this, Scientists consider deforestation, unskilled to use fuel energy, agricultural production, and chemical pesticides use and human activities against nature all these factors are responsible for the global warming. Increase use of fossil fuel, deforestation and human negative activities, increasing the amount of Green House Gases in the atmosphere. According to the Kyoto Protocol Carbon dioxide (CO2), Methane (CH4), Nitrous Oxide (N2O), Halo Carbon (HC), Ozone (O3) and Sulfur dioxide (SO2) these six gases recognized as the main Green House Gases. From the very past these Green House Gases are protected the heat comes from the sun and have balanced the world temperature (Water vapor also help to consume heat). Green House process is an important factor to balance the world energy. But after the Industrial revolution in eighty's, use of petroleum and other natural gas has increased a lot. For increasing the amount of Green House Gases in the atmosphere, the natural Green House System has become faster. In result of that more heat energy is being trapped in the atmosphere. Warm atmosphere then increases the temperature of the earth's surface. In this circumstances with the total system of the climate, nature of different components, like- rainfall, wind flow, ocean current etc are changing. With a few degrees change in temperature in the atmosphere will bring a huge change in rainfall, ocean current, wind flow etc. The previous climate model will be changed if the

components of the climate are changed. This sort of irregularities and change is observed in the global climatic condition for the global warming influenced by the Green House Gases.

Adaptation Strategies
Adaptation is defined as any adjustment of physical infrastructure, natural systems, social and economic activities or institutional arrangements that reduce the vulnerability to climate change or enhances the opportunities these changes offer (Bangladesh climate change and sustainable development, World Bank, July, 2001) Why adaptation is required? Most of the effect of climate change in Bangladesh is long term, irrevocable and gradual. In some cases the impact increases the intensity of extreme events. In both cases to minimize the losses or to increase the effectiveness of mitigation measure it is necessary to implement the anticipatory adaptation measure. Beside this, to implement or to construct any long term structural measure it is required to consider the climate change to avoid any affect in the long run. Who would adapt? Depending on the type and range of the problem, the Government of Bangladesh (GOB), Non Government Organization or Research Organizations can consider adaptation. There are so many works, programs or projects have been done where there were scopes to consider climate change in the development program but it was not. GOB (1988), UNDP (1989), USAID (1989), French Engineering construction (1989) and Government of Japan (1989) etc should be mentioned for their study on flood of Bangladesh of 1987, 1988. In May 1992 United Nations Framework Convention on climate change (UNFCCC) was adopted. Although the main focus of the convention was to reduce green house gas emission, it also recognizes the role of adaptation. In 2003, the Government of Bangladesh along with UNDP and DFID took decision about the Comprehensive Disaster Management Plan

(CDMP). CDMP open a climate change component: climate change cell. In 2004 Climate Change Cell was established as a unit of the Department of Environment. World Bank and Asian Development Bank (ADB) have done many projects on environmental issues like: Small scale Water Resource Development Sector Project (SSWRDSP), Khulna-Jessore Drainage Rehabilitation Project (KDRP), Sundarban Biodiversity Conservation Project (SBCP), Coastal Green belt Project (CGP) etc, where they have scope to work on climate change. Bangladesh Institute for Development Studies (BIDS), Bangladesh Center for Advanced Studies (BCAS), Bangladesh Agricultural Research Council (BARC), Bangladesh Unnayan Parishad (BUP), CARE, PRODIPAN have initiated some work on climate change.

Risks in Individual Sector
Coastal Zone of Bangladesh: • Drainage congestion is one of the important problems in the coastal area. Drainage congestion caused by the high water flow and over sedimentation in the flood plain. Saline water intrusion is increasing as the sea water encroaches the land due to the sea level rise and Lower River flows. Coastal land is degrading due to the erosion by the changing dynamics in river flow. Coastal storm-surges make serious impact on the adjacent area due to the imbalance between the coastal land and the sea level.

Fresh Water Resources: • Fresh water availability is decreasing due to the increasing demand (increased population), increase of evapo-transpiration and lower river discharge.

Drainage congestion for the high water flow and increased the level of the bed due to the sedimentation in the flood plain. Land erosion is increasing due to the change in dynamics in the river flow but not filling up in that way.

Agriculture: • Due to the increase in temperature the agricultural production is under threat. During the flood period a vast area/amount of agricultural product is damaged by the food water. In the coastal area due to the intrusion of saline water and for the increase in salinity in water and soil the agricultural production is hampered.

Public Health: • Diarrhea, Cholera and other water born diseases increases due to climate change. Reduction of drinking water availability Risk in human lives is increasing with the increased intensity of extreme events. Loss in agricultural production cause ultimate threat to the food chain.

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Ecosystem and Biodiversity: • Increased salinity Sunderban. cause adverse effect on the trees of

Lower river and ground water flow may cause desertification in the coastal zone in some sensitive area. Increase in temperature reduces the availability of fishes.

Adaptive Measures/Steps in different sectors
Considering the above risks in different sectors of Bangladesh following adaptation strategies should be bring under consideration. • To avoid the drainage congestion in the coastal zone it is necessary to make infrastructure for over sedimentation in the flood plain or in the bed. For example Increasing drainage capacity, construction of tidal basin, pump drainage etc. New infrastructure can be made to develop drainage system and local water management in the coastal area. Beside this it is needed to proper monitoring of management and operational activity of existing drainage system. Dredging and river training are also effective to increase the flow in river and reducing the water congestion. Increase river water flow can help in reduction of saline water intrusion in the land area. To protect the morphological change by erosion different structures like- mangrove greenbelt, river training, dams etc can be made. To minimizing the impact of storm surge, cyclone etc cyclone centre, advanced forecasting system and plantation (mangrove greenbelt) can constructed. To increase the fresh water availability it is important to increase the flow in upstream and any alternative like water storage can be made. Improved drainage system after flooding is required to avoid the congestion of fresh water. For example restoration of channel through river dredging, river training, flushing to prevent over siltation, increasing the capacity of openings in roads, high way, and proper regulation to discharge the required volume of water etc.

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To adapt the increased morphological dynamics of the river physical adaptation is required to build protection against bank erosion and dredging of navigation channels. For improved and efficient irrigation, crops diversification and conjunctive use of surface and ground water is important to reduce the impact of drought. To provide safe and quality drinking water, water treatment facility can be established. Sewage treatment is another important issue should consider to keep the local water body clean. Improved public health education for reproductive health system is essential. In case of Sundarban a sustainable water flow is required in the water body. Coastal green belt, agro-forestry is very important as an adaptive measure. To aware the people about the adaptation of the ecosystem is indispensable. To adapt different important species of Sundarban can be attempted.

Source: 1. The Library Of Congress Country Studies. 2.

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