The U.S. Climate Change Science Program (CCSP), a consortium of Federal agencies that investigates climate, has established a Synthesis and Assessment Program as part of its Strategic Plan. A primary objective of the CCSP is to provide the best science-based knowledge possible to support public discussion and government- and private-sector decisions about the risks and opportunities associated with changes in climate and in related environmental systems (U.S. Climate Change Science Program, 2007). The CCSP has identified an initial set of 21 Synthesis and Assessment Products (SAPs) that address the highest-priority research, observation, and information needed to support decisions about issues related to climate change. This assessment, SAP 1.2, focuses on the evidence for and record of past climate change in the Arctic. This SAP is one of three reports that addresses the climate-variability-and-change research element and Goal 1 of the CCSP Strategic Plan to improve knowledge of Earth’s past and present climate and environment, including its natural variability, and improve understanding of the causes of observed variability and change. The development of an improved understanding of natural, long-term cycles in climate is one of the primary goals of the climate research element and Goal 1 of the CCSP (U.S. Climate Change Science Program, 2007). The Arctic region of Earth, by virtue of its sensitivity to the effects of climate change through strong climate feedback mechanisms, has a particularly informative paleoclimate record. Because mechanisms operating in the Arctic and at high northern latitudes are also linked to global climate mechanisms, an examination of how Arctic climate has changed in the past is also globally informative.