Alpine glaciers and ice-caps in Africa, the Americas, Europe, even much of the Himalayas, are receding, some could disappear altogether, with devastating consequences for river flow and downstream irrigation. Wetlands are drying out, rainfall patterns are changing, weather extremes (floods, hurricanes, droughts, etc) are all becoming more frequent and more severe at a greater rate than originally estimated. The health impacts of all these processes could be devastating, and will affect huge numbers of people. For example, an increase in the average ambient temperature of half to one degree Celsius would expand the range of malaria-carrying mosquitoes into temperate zones and higher altitudes that would put almost a billion additional people at risk. Melting of polar and alpine icecaps and thermal expansion of the sea water mass is expected to raise sea levels by about 50 cm in the next 50 years. Half a billion people live very near sea level; their habitat, especially in small island states will disappear or be threatened with inundation. Climate change also threatens food security, by leading to less predictable weather patterns and growing seasons, and more frequent extreme weather (floods, droughts). Climate change forces people to migrate as environmental refugees, and thereby imposes severe strains on public health services, many of which are already stretched to the limit because tax revolts and budget cuts have led to deterioration of public health infrastructure.