This publication provides technical supporting information for the 26 indicators that appear in the U.S. Environmental Protection Agency's (EPA's) report, Climate Change Indicators in the United States, 2012. EPA prepared this publication to ensure that each indicator is fully transparent-so readers can learn where the data come from, how each indicator was calculated, and how accurately each indicator represents the intended environmental condition. EPA developed a standard documentation form, then worked with data providers and reviewed the relevant literature to address the elements on the form as completely as possible.