At the start of a heat wave in June 1988, James E. Hansen, director of the Goddard Institute for Space Studies at the National Aeronautics and Space Administration, testified before Congress that human-induced global warming as a result of greenhouse gas emissions was changing the earth’s climate. His testimony focused international attention on the issue of global warming.

Since 1988 many scientists and environmentalists have sided with Hansen in the belief that global warming poses a threat to the environment. The United Nations Intergovernmental Panel on Climate Change (IPCC) projects that the earth’s average surface temperature will increase by 2.5 to 10.4 degrees Fahrenheit from 1990 to 2100. Rising sea levels, extreme weather, and dislocated populations are impacts anticipated from rapid warming. Writes Dr. Kevin E. Trenberth of the National Center for Atmospheric Research, “[Global warming] is disruptive to human systems...