Millions worldwide may die from heat and disease as global warming worsens. The IPCC projects that more frequent and more severe heat waves will be an early effect of global warming. Events such as the deadly stretch of hot days that killed 669 people in the Midwest during the summer of 1995 and 250 in the Eastern United States in July 1999 are likely to become more common. Scientists are already finding that the number and intensity of extreme weather events are increasing.
Infectious disease is the second major threat that global warming poses to human health.
As temperatures rise, disease-carrying mosquitoes and rodents move into new areas, infecting people in their wake. Global warming could mean millions more around the world will become infected with malaria. Since 1990, the start of the hottest decade on record, outbreaks of locally transmitted malaria have occurred in California, Florida, Georgia, Michigan, New Jersey and New York. IPCC scientists project that as warmer temperatures spread north and south from the tropics, and to higher elevations, malaria-carrying mosquitoes will spread with them. In association with a warm winter and prolonged drought, New York City experienced a significant outbreak of West Nile virus in the summer of 1999.