Facing an Uncertain Climate

Our climate is changing, and the results are increasingly disruptive. Droughts, dust storms, and wildfires are occurring more often in some areas, while others are plagued by an increasing number of intense rainstorms and hurricanes. Glaciers are melting, sea levels are rising, coasts are eroding, and heat waves are happening at historic rates, seriously threatening the survival of ecosystems and placing approximately 25% of all plant and animal species on the path to extinction by 2050 (1). Melting sea ice has shortened the season during which polar bears can search for food and has hindered their reproduction; the U.S. Fish and Wildlife Service is on the verge of deeming them the first mammals in danger of extinction because of global warming.

Human health is at stake, too. Research has linked climate change to a long list of health problems, including asthma, allergies, infectious diseases, heart disease, and cancer. The World Health Organization (WHO) has estimated that warming and precipitation trends already claim at least 150 000 lives annually worldwide and that this number will climb to at least 300 000 annually by 2030.

Nearly all scientists agree that the buildup of greenhouse gases in the atmosphere—particularly carbon dioxide from combustion of fossil fuels and forest burning—is warming the Earth and altering the natural climate and weather patterns in new and potentially perilous ways. Carbon dioxide levels are higher now than at any time in the past 800 000 years and are predicted to increase significantly in this century. The effects are likely to imperil health both directly (from extreme weather events, such as hurricanes, heat waves, or floods) and indirectly (from the disturbance of complex ecological processes, such as changes in patterns of infectious disease, freshwater supplies, and food availability) (2). A seminal report from the Intergovernmental Panel on Climate Change, …