The first step to making that case is understanding exactly what warmer temperatures will do to us and our diseases -- and few scientists know more about the topic than Patz, a member of the UN's Nobel Prize-winning Intergovernmental Panel on Climate Change (IPCC). (Hear Patz talk about global warming and health on this week's Greencast.) As temperatures increase, and hotter, drier summers become the norm in regions that were once temperate, powerful heat waves -- like the one in Europe in 2003, which killed an estimated 35,000 people -- will take a toll. At the same time, climate models suggest that rain could become less frequent overall but more intense when it does fall, leading to a double whammy. Longer and fiercer droughts in some areas will worsen hunger, but severe rainstorms carry an increased risk of water-borne diseases like cholera. "It's not just warming, it's climate change," says Patz. "It's changing the air cycle, creating more extreme flooding, more extreme droughts."