Climate Change, Health, and Costs 11 malaria and diarrheal diseases contribute to approximately the same proportion to this total cost (though for the high-cost scenario, diarrheal diseases account for a slightly higher share). As noted by Ebi (2008), a key assumption behind these estimates is that the number of annual cases of diarrheal diseases, malaria, and malnutrition, as well as the cost of treatment, remain constant over the period of analysis. Given the projected increase in population, this implies that the rates of incidence of each of these health outcomes decrease over time in line with the rate of population growth. Ebi (2008) notes: Conducting a sensitivity analysis that incorporated these population increases would require assumptions of future incidence rates of these health outcomes, based on assumptions of socioeconomic development, including improvements in health care delivery, the rate of deployment of current interventions, and the development of more effective technologies. Using the current number of cases in the analysis in effect assumes that incidence will decrease as population increases, without attribution of the possible reasons for such a decline (page 6). In a recent World Bank study (2010) such attribution was explicitly modeled insofar as income is concerned. The study used WHO econometric models using panel data on income and health to project cause-specific deaths and disability-adjusted life-year rates by demographic group through 2030 (WHO 2004). Accounting solely for this attribution (as income increases, the rate of incidence falls), the average global costs of adaptation in the health sector for the prevention and treatment of diarrhea and malaria alone (not including malnutrition) over the period 2010–2050 was estimated to reach $1.3 billion (in the dry weather scenario) to $1.6 billion per year (in the wet weather scenario), in 2005 dollars (Table5). East Asia, the Pacific, and South Asia account for half of this estimated cost of adaptation. As a result of the different modeling approaches, these estimates (World Bank 2010) are significantly lower than those reported by Ebi (2008). One concludes that (i) there remains large uncertainty as to the adaptation costs for climate change–related health outcomes, and (ii) the analyses have so far captured a limited number of climate change–related health outcomes. For example, neither Ebi (2008) nor the Table 5 Average Annual Adaptation Cost for Human Health: Preventing and Treating Malaria and Diarrhea, by Region and Decade, 2010–2050 ($ billion at 2005 prices, no discounting) Period EAP ECA LAC MENA SA SSA All 2010–2019 0.7 0.1 0.0 0.1 1.0 0.9 2.8 2020–2029 0.2 0.0 0.0 0.1 0.7 0.7 1.7 2030–2039 0.1 0.0 0.0 0.1 0.3 0.7 1.2 2040–2049 0.1 0.0 0.0 0.0 0.1 0.8 1.0 2010–2049 0.2 0.0 0.0 0.1 0.5 0.8 1.6 2010–2019 0.5 0.0 0.0 0.1 0.8 0.6 2.0 2020–2029 0.1 0.0 0.0 0.1 0.7 0.6 1.5 2030–2039 0.1 0.0 0.0 0.0 0.3 0.6 1.0 2040–2049 0.0 0.0 0.0 0.0 0.1 0.6 0.7 2010–2049 0.2 0.0 0.0 0.0 0.5 0.6 1.3 Wet scenario Dry scenario EAP = East Asia and Pacific, ECA = Europe and Central Asia, LAC = Latin America and Caribbean, MENA = Middle East and North Africa, SA = South Asia, SSA = Sub-Saharan Africa. Note: Numbers have been rounded to the first decimal point. “0.0” billion should not be read as absolute zero. Source: World Bank. 2010. The Economics of Adaptation to Climate Change: Synthesis Report. Washington, DC.