The prevalence of particular diseases and other threats to human health depend largely on local climate. As several of the serious diseases only appear in warm areas, any significant climate change will increase their prevelance. Warm temperatures also increase air and water pollution, which in turn harm human health. As the climate changes human health needs will change.
Human-induced changes in the global climate system and in stratospheric ozone pose a range of health risks. Irrespective of actions that might soon be taken to reduce or halt these environmental changes, human populations will be exposed to some degree of climate change and increased ultraviolet irradiation over the coming decades.
Diseases that are spread by mosquitoes and other insects could become more prevalent if warmer temperatures enabled those insects to become established farther north. Such "vector-borne" diseases include malaria, dengue fever, yellow fever, and encephalitis.