It is frequently noted that humans are quintessentially adaptable, that people live both in the Arctic north and in the heated tropics. This observation is sometimes taken to indicate that there would be no direct impacts on people from a projected climate change. However, studies show that there could be effects resulting from higher temperatures, both in the United States [ Kalkstein, 1991] and internationally [ Kalkstein and Smoyer, 1993], and Longstreth [1991] has examined a long list of possible human health impacts--heat stress, allergen production, migration of disease vectors, perinatal mortality, and shifts in the seasonal pattern of communicable disease occurrence--some of these interacting with the ability of extra ultraviolet sunlight admitted to the surface by the depleted ozone layer to damage the immune response of people. Disease impacts and studies are summarized by Shope [1991]. These studies find that some diseases may spread with the spread of warmer climates and with the rapid metamorphosis of the disease vectors and microorganisms, while diseases whose vectors are dependent on ecosystem integrity, e.g., Lyme disease, could become less prominent.
The assumptions implicit in the baseline projections of a major climate change, for example that there will be a continuing increase in the use of fossil fuels, coal in particular, imply that there will be sizable direct health effects from industrial emissions independent of the climate change itself [ Piver, 1991]. As mentioned earlier in another context, this fact compounds the study of climate change impacts and will make the separate observation of these impacts more difficult.