Costing the health impacts of climate change is complex and controversial. It is complex because of the great heterogeneity of the health impacts, which include death, infectious disease, nutritional deprivation, and post-traumatic stress disorders. It is controversial because of difficulties in assigning money values to a diverse range of health deficits, doing so across varied cultures and economies, and taking account of the full "stream" of health impacts into the future (with appropriate time-discounting). During the 1990s, an attempt was made to develop a more standardized approach to measurement of the population health deficit by combining chronic illness or disability and premature death, via weighting procedures, into an integrated index—the Disability-Adjusted Life Year (Murray, 1994; Murray and Lopez, 1996).

To date, however, there is negligible scientific literature on the population burden of disease attributable to current or future climate change. There is no such literature on the DALY-based impact. Hence, there is no basis for making overall estimates of the direct costs to society of the health impacts of climate change. Nevertheless, some approximate estimations have been published of the impacts on national economies of major infectious disease outbreaks, such as might occur more often under conditions of climate change. For example, the outbreak of plague-like disease in Surat, northwest India, in 1994 cost an estimated US$3 billion in lost revenues to India alone (John, 1996; WHO, 1997). The cost of the 1994 Dengue Haemorrhagic Fever (DHF) epidemic in Thailand was estimated to be US$19-51 million (Sornmani, et al., 1995). The cost of the 1994 epidemic of dengue/ DHF in Puerto Rico was estimated to be US$12 million for direct hospitalization costs alone (Rodriguez, 1997; Meltzer et al., 1998).

The ideas of development, sustainability, and equity inform much of the content of this chapter. It has been noted repeatedly that health impacts will tend to occur unevenly in the world and that the impacts in poorer populations, especially in the least-developed countries, often will be augmented by the heightened vulnerability of those populations. That is one of several reasons why—in today's world in which the gap between rich and poor is widening (UNDP 1999), in association with the nonredistributive character of market-dominated global economics (McMichael and Beaglehole, 2000)—new ways of redressing the imbalance in wealth and knowledge should be found.

The chapter also notes that development on a broad front—social, economic, technological, and provision of public health services and capacities—is crucial to a population's adaptive capacity to lessen the impacts of climate change.

Indeed, the health of a population is a key indicator of "sustainability." The capacity of the global population to achieve and maintain good health is an index of how well the natural and social environments are being managed. Wealthy local populations can afford to subsidize their health maintenance, drawing on resources imported from elsewhere. At a global level, however, health indicators provide a more valid indication of the extent to which the "carrying capacity" of the biosphere is being maintained.

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