Global warming may have severe consequences for developing countries prone to extreme weather events. Projections by the Intergovernmental Panel on Climate Change and the World Meteorological Organization suggest the frequencies and/or intensities of climate extremes will increase in the 21st century. Some recent extreme weather events illustrate how severe their consequences can be. Examples include heavy floods in Australia and Brazil in 2011, extreme winter weather all over Europe, heat wave in Russia, devastating floods in Pakistan, India, China, and Mozambique in 2010, and super cyclones in Myanmar (in 2008) and Bangladesh (in 2007).
Adaptation to increased risks of severe weather events and impacts of climate change is essential for development. Adaptation will require climate-smart policies and investments to make countries more resilient to the effects of climate change, such as losses of property, habitat, infrastructure, and lives. However, country governments and their citizens, as well as development partner institutions and climate negotiators, need a better understanding of adaptation cost and potential damage due to climate change, to formulate effective adaptation policies.
Recently, to shed light on potential damage from extreme weather events and adaptation costs, experts from the Institute of Water Modeling and Center for Environmental and Geographic Information Services in Bangladesh, Mainul Huq, Kiran Pandey and I considered potential intensification of cyclones due to climate change for Bangladesh. Bangladesh is the world’s most vulnerable country to tropical cyclones, and the focus of our study was on cyclones with 10 percent or greater probability of occurring each year.
Historical records indicate that the greatest damage during cyclones result from the inundation caused by cyclone-induced storm surges. In a changing climate, increase in ocean surface temperature and rising sea levels would likely intensify cyclonic storm surges and further increase the depth and extent of storm surge-induced coastal inundation in Bangladesh. Hence, we integrated information on climate change, hydrodynamic models, and geographic overlays to assess the vulnerability of coastal areas in Bangladesh to larger storm surges and sea-level by 2050.
We considered a sea-level rise of 27 centimeters, increased wind speed of 10 percent, and landfall during high tide to simulate cyclonic storm surges in a changing climate by 2050. Our analysis was conducted in three steps. First, we delineated the potential inundation zone and projected depth of inundation for 2050 without and with climate change. Second, we identified the critical populations and infrastructure exposed to the increased risk of inundation in a changing climate. Finally, we quantified the cost of adapting these assets to avoid further damage due to climate change.
Our estimates indicate that the vulnerable area in coastal Bangladesh with more than 3 meters of inundation depth is likely to increase by 69%, and that with a 1 meter – 3 meters inundation depth is likely to increase by 14% due to climate change. We further estimate that currently 8.06 million people in coastal Bangladesh are vulnerable to inundation depths greater than 3 meters resulting from cyclonic storm surges. With population growth, that number is expected to increase to 13.5 million by 2050 even without climate change. Without further adaptation measures, another 9.1 million coastal inhabitants will be exposed to similar inundation risk by 2050 in a changing climate. Population exposed to 1 meter - 3 meters inundation depth is expected to increase by 7.06 million due to climate change.
The Government of Bangladesh is fully committed to improving the country’s resilience to cyclone risks. Over the past 35 years, a significant investment has been made in polders, cyclone shelters, emergency warning, and evacuation systems; and the country has established infrastructure design standards and building codes. In general, the relative severity of the impacts from cyclones in Bangladesh has decreased substantially since the 1970s from the progress in disaster management and flood protection infrastructure. It is feared that these gains may be at risk if cyclones intensify due to of climate change.
Our analysis indicates that despite the extensive infrastructure Bangladesh has in place to protect coastal residents from cyclonic storm surges and tidal waves, it has a current adaptation deficit (deficits in dealing with current climate-related risks) of US$2.46 billion. In a changing climate, the greater expanse and depth of the areas inundated would put many more existing structures at risk. By 2050, nearly half of the country’s 123 coastal polders would be overtopped, and inadequate mangrove forests would mean higher-velocity storm surges. Moreover, the capacity of life-saving cyclone shelters and early warning and evacuation systems would be exceeded.
By 2050, the adaptation cost of coping with cyclonic storm surges in a changing climate will total about US$2.4 billion, with an annual recurrent cost of more than $50 million. Once again, this adaptation cost refers to the increased inundation area and depth for a 10-year return cyclone in a changing climate. About half of this adaptation cost—US$1.2 billion—is for constructing the 5,702 extra multipurpose cyclone shelters needed to protect the additional coastal residents exposed to inundation risk. More than one-third of the total cost is for enhancing the height of polders—33 sea-facing and 26 interior polders—while the remainder is dedicated to constructing cyclone-resistant private housing, increasing coastal afforestation to protect sea-facing polders, and strengthening the early warning system.
In 2007, Cyclone Sidr, a 10-year return cyclone struck the south-west coast of Bangladesh with an average wind speed of 223 kilometers per hour, causing 3,406 casualties, 55,282 injuries and affecting 8.9 million people. It damaged 0.6 million hectares of standing crop land, completely destroyed 537,775 houses, and submerged 8,075 km of roads. Estimated damages and losses from Cyclone Sidr, according to the Government of Bangladesh, totaled US$1.67 billion. In a changing climate, a similar 10-year return period is expected to be more intense. We estimate the total additional potential damage from a 10-year- return-period cyclone in a changing (2050) climate at US$2.44 billion, with US$2.12 billion in added potential losses. The assessment drew on projected annual growth in Bangladesh’s coastal population (1 percent) and GDP (6–8 percent) and the devastation (US$1.67 billion damages and losses) experienced in 2007 resulting from Cyclone Sidr.
Total damages and losses from cyclones in Bangladesh will far exceed this figure as damages from more frequent but less intense cyclones, nonetheless destructive, have not been considered in our estimation. However, comparison of the conservative damage estimate from a single 10-year return period cyclone with the storm surge protection cost indicates that the incremental cost of adapting to climate change by 2050 is small compared to the potential damage due to climate change. This strengthens the case for rapid adaptation.
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