Part 2-Appen A

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  Appendix A   Climate Change in Bangladesh A.1   CLIMATE CHANGE Climate Change is basically the change in climate over a time period that ranges from decades to centuries. Climate change is a normal part of the Earth’s natural variability, which is related to interactions among the atmosphere, ocean, and land, as well as changes in the amount of solar radiation reaching the earth. However, the term “climate change” has two official definitions defined by Intergovernmental Panel on Climate Change (IPCC) and United Nations Fr amework Convention on Climate Change (UNFCCC). According to IPCC “ Climate Change refers to any change in climate over time, whether due to natural variability or as a result of human activity  .” And UNFCCC defined climate change as “  A change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.”    The climate of the earth is determined by both natural and human srcin factors. There are a number of natural factors responsible for climate change such as continental drift, volcanoes, ocean currents, comets and meteorites etc. The problem is not the fact that the climate is changing, but the rate at which it is changing. Rising fossil fuel burning and land use changes have emitted, and are continuing to emit, increasing quantities of greenhouse gases into the Earth’s atmosphere. These greenhouse gases include carbon dioxide (CO 2 ), methane (CH 4 ), nitrogen dioxide (N 2 O)and the halocarbons (a group of gases containing fluorine, chlorine and bromine), and a rise in these gases has caused a rise in the amount of heat from the sun withheld in the Earth’s atmosphere, heat that would normally be radiated back into space. This increase in heat has led to the greenhouse effect, resulting in climate change. Current green house gas emission is 17,500 Gg and will be 44,500 Gg for next 100 years. The main characteristics of climate change are increases in average global temperature (global warming); changes in cloud cover and precipitation particularly over land; melting of ice caps and glaciers and reduced snow cover; and increases in ocean temperatures and ocean acidity  –  due to seawater absorbing heat and carbon dioxide from the atmosphere. A.2   Climate change in Bangladesh: Bangladesh has been identified as one of the countries with the highest level of vulnerability to climate change particularly the coastal zone, covering about 30 per cent of the country. Bangladesh is highly vulnerable, because it is low-lying, located on the Bay of Bengal in the delta of the Ganges, Brahmaputra and Meghna, high population density and high level of poverty. The country is frequently affected by natural disaster like floods, tropical cyclones, storm surges and droughts etc, which are likely to become more frequent and severe in coming years due to climate change impacts. Sea level rise, temperature rise, increased evaporation, changes in precipitation and changes in cross boundary river flows are identified as the agents of these changes. National economy of Bangladesh is strongly dependent on agriculture and natural resources that are highly sensitive to climate change and sea level rise. The direct annual cost to the national economy of natural disasters over the last 10 years is estimated to be between 0.5% and 1% of GDP. These changes will threaten the country’s significant achievement and initiatives towards reducing poverty and achieve Millennium development Goals (MDCs).  Part 2 2 Fig. 1 Ganges, Brahmaputra and Meghna river basin A.3   Climate change scenario: The future climate parameters have been estimated utilizing Global Circulation Models (GCM) as used by IPCC Fourth Assessment Report. For this purpose “Model for the Assessment of Greenhouse -gas Induced Climate Change” (MAGICC) and “SCENario GENerator” (SC ENGEN) developed by the National Center for Atmospheric Research (NCAR), USA and Climatic Research Unit (CRU), University of East Anglia, UK have been used. The predicted future changes in temperature and precipitation for Bangladesh has been computed two Special Report on Emissions Scenarios (SRES) A2 and B1 and for two time periods 2030s and 2050s. SRES A2 scenario considers a very heterogeneous world with continuously increasing global population and regionally oriented economic growth that is more fragmented and slower than in other scenarios. B1 scenario considers a convergent world with very rapid global population but with rapid changes in economic structures toward a service and information economy, with reductions in material intensity, and the introduction of clean and resource-efficient technologies (Nakicenovic et al., 2000). Table 1 presents the annual average changes predicted under two scenarios for 2030s and 2050s. From the Table 1 it is observed that temperature will increase 1.6°C by 2050s while precipitation will increase by 8%. Division wise annual average changes in temperature and precipitation for A2 and B1 scenarios are given in annex A. Table 1: Annual average changes in temperature and precipitation Emission Scenario Temperature (Change in °C) Precipitation (Percentage change) 2030s 2050s 2030s 2050s A2 0. 73 1.32 4.9 8.1 B1 0.78 1.62 6.3 8.4 A.4   Climate change impact: Bangladesh is probably the only country in the world with most of its territory lying on the deltaic flood-plain of three major rivers and their numerous tributaries. Literature on impacts of climate change for the country suggest that current water-related variations and extremes will be further accentuated by climate change, implying that it is more likely to face high-intensity extreme weather/climatic conditions such as floods,   Appendix A 3 droughts, cyclones, and associated storm surges (Huq et al., 1998; World Bank, 2000). The climate change impacts that are likely to affect Bangladesh more are briefly described below.  A.4.1   Flood: Flood is a common phenomenon in Bangladesh. Generally, the frequency of occurrence of more intense rainfall events coupled with huge discharge from upstream causing severe floods in Bangladesh. During the last 50 years, at least 6 serious floods occurred, affecting 35-75% of the land area. Two exceptional years were 1987 and 1988 when consecutive floods devastated more than 40% of the country. The historical water level and discharge data shows that the peak of discharges in the Ganges, Brahmaputra and Meghna rivers do not occur at the same time in each year. The onset and withdrawal of the peak flows are shifting. Flow records over 50 years long for the station Bahadurabad Brahmaputra/Jamuna rivers) show that peak discharge is increasing and is peaking earlier. The flood vulnerability of Bangladesh is shown in Figure 2. Under climate change, the flooded area is estimated to increase for example, it is estimated that, flooded area may increase by 6% and 14% in 2030 and 2050 respectively. The expansion will be observed mainly in the existing flood prone areas. Change in flooded area in 2030s and 2050s for A2 and B1 scenarios are shown in annex B. Figure 1: Flood Vulnerability Map of Bangladesh  Part 2 4  A.4.2   Cyclone: Cyclones are common phenomena in the coastal area of Bangladesh. A storm surge during a cyclone inundates coastal areas and offshore islands and is responsible for most of the loss of life and property. Bangladesh is hit by about 0.93% (~1%) of the world’s total tropical storms. Therefore, in terms of frequency Bangladesh is not a high-risk cyclone prone area, however, about 53% of the total world deaths due to tropical cyclones occurred in Bangladesh (Ali, 1999). Vulnerability is therefore a critical element in cyclone impacts. Between 1881 and 2001, decadal frequency cyclone shows that 3 to 7 cyclones hit the coastal area of Bangladesh. During this period there has been about an 8% increase in the frequency of devastating cyclones. Ali (1999) commented that an increase in 2°C in sea surface temperature (SST) would likely cause an increase in the probability of cyclone formation from depressions. According to IPCC (2001) there is some evidence that regional frequencies of tropical cyclones may change but none that their locations will change. There is also evidence that the peak intensity may increase by 5% and 10%. . According to Hassan et al, 2007  , the cyclone High Risk Areas (HRAs) of 8,900 sq km will increase by 40% in the 2050s (Figure 3) and currently about 8.3 million people live in cyclone HRAs that will increase to 20.3 million in the 2050s. Figure 2: Changes in cyclone High Risk Areas for current conditions, the 2020s and the 2050s. Only worst case examples included  –  highest warming.  A.4.3   Salinity: Because of its low lying situation Bangladesh is very vulnerable to current coastal hazards and future sea level rise (SLR). Sea level rise would increase the extent of saline water intrusion by pushing the saline water front landwards. Due to change in salinity extent, there will be significant changes in fresh water zone and brackish water zone. Salt water from the Bay of Bengal is reported to have penetrated to 100 km or more inland along tributary channels during the dry season. Current salinity, area within >1ppt salinity range is 6,687sq. km which will be 9,814 sq. km in 2050 (shown in Figure 4). As a result, the coastal populations are currently facing scarcity of fresh water during the dry season which will aggravate in future due to sea level rise The Sundarbans, which is already experiencing high salinity, will be affected more by salinity water intrusion due to increased sea level both in dry and monsoon season.
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