Connections between climate and disease are not new.5 Climate constrains the range of many infectious diseases, and weather affects the timing and intensity of outbreaks.6 Reappraisal of these associations is aided by increased understanding of the Earth's climate system, in particular how land and sea surface temperatures and pressure gradients drive winds and weather. The atmosphere holds 6 percent more water vapor with each rise in temperature of one degree Celsius. Sudden weather changes and sequential extremes also can yield surprises. Droughts suppress predators, whereas heavy rains boost food supplies-a synergy that can spark rodent population explosions. If the world's oceans are a long-term heat sink for this century's global warming, then this has profound implications for marine life and terrestrial weather patterns.
Ecological integrity is central to health.
Parched agricultural lands attract aphids, locusts, and virus-bearing white flies, while fungi flourish after floods. Of great concern are diseases that attack coral and sea grasses, essential habitats that sustain mobile aquatic species. High sea surface temperatures in the 1990s have resulted in bleaching, perhaps the most disturbing biological sign of global warming. With disproportionate warming in the winter, at high latitudes and high elevation,19 most summit glaciers are in retreat. The effects of warming and changing weather patterns on forests, agriculture, marine life, and water may hold the most profound consequences for global health.