IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability Summary of human health

There is now good evidence of changes in the northward range of some disease vectors, as well as changes in the seasonal pattern of allergenic pollen. There is not yet any clear evidence that climate change is affecting the incidence of human vector-borne diseases, in part due to the complexity of these disease systems. High temperature has been associated with excess mortality during the 2003 heatwave in Europe. Declines in winter mortality are apparent in many temperate countries, primarily due to increased adaptation to cold.

1.3.8 Disasters and hazards

Rapid-onset meteorological hazards with the potential to cause the greatest destruction to property and lives include extreme river floods, intense tropical and extra-tropical cyclone windstorms (along with their associated coastal storm surges), as well as the most severe supercell thunderstorms. Here we assess the evidence for a change in the frequency, geography and/or severity of these high-energy events. By definition, the extreme events under consideration here are rare events, with return periods at a specific location typically in excess of 10 to 20 years, as the built environment is generally sited and designed to withstand the impacts of more frequent extremes. Given that the strong rise in global temperatures only began in the 1970s, it is difficult to demonstrate statistically a change in the occurrence of extreme floods and storms (with return periods of 20 years or more) simply from the recent historical record (Frei and Schar, 2001). In order to identify a change in extreme flood and storm return periods, data has been pooled from independent and uncorrelated locations that share common hazard characteristics so as to search collectively for changes in occurrence. A search for a statistically significant change in occurrence characteristics of relatively high-frequency events (with return periods less than 5 years) can also be used to infer changes at longer return periods.