Global warming health effects

Severe heat waves -- characterized by stagnant masses of warm air and consecutive nights with high minimum temperatures -- will intensify in the United States and Canada, according to the data on North America released Monday by the United Nations

Intergovernmental Panel on Climate Change.

 Higher temperatures over the coming decades are expected to cause more smoggy days and heat waves, contributing to a greater number of illnesses and deaths in the United

States, according to international climate scientists.

Just how much people and ecosystems suffer in North America, scientists reported, depends on how well greenhouse gases are controlled. And, the scientists cautioned, it depends on how well they plan for and try to prevent the damage.

Global warming is already affecting people's health, said Kristi Ebi, an epidemiologist from Virginia and lead author of a chapter on human health written for the international science panel.