Gaps often exist between scientific findings and the actions taken by policy makers. In the case of global climate change, the United States has chosen not to act to reduce its greenhouse gas emissions. This is despite warnings from the Intergovernmental Panel on Climate Change that “most of the warming observed over the last 50 years is attributable to human activities,” and that these forces are expected to cause an additional 1.4–5.8°C rise in temperature by 2100.