A report issued in July 2008 by the U.S. Climate Change Science Program (CCSP) and prepared by the Environmental Protection Agency (EPA), says that in the coming decades, climate change will pose “substantial” threats to human health. Across the US public health will be affected by heat waves, droughts, wildfires, flooding and worsening air quality, with the poor, elderly and children suffering the most.

The report, entitled ’Analyses of the Effects of Global Change on Human Health and Welfare’, "concludes that climate change poses real risk to human health and human system that supports our way of life in the United States."

Health effects will vary by region. In the West changing weather patterns could thin mountain snow and ice that feeds rivers, affecting hydroelectric dams and water supplies. Eastern cities are likely to suffer a higher number of bad air days. Midwestern and Northeastern cities which are not as well adapted to heat as Southern cities are likely to be disproportionately affected by heat related illnesses.

According to the report climate change will “accentuate the disparities already evident in the American health care system”, therefore the most important adaptation strategy to help respond to the changing climate will be to “support and maintain the United States’ public health infrastructure.”

Despite the report’s warnings, in the same month the EPA decided not to regulate greenhouse gas emissions (GHG) under the federal Clean Air Act, at least not until after a change in the US administration. Instead the White House dismissed the report’s findings, arguing that the Clean Air Act is the wrong tool to control global warming.