This report focuses on the Climate Projections Based on Emissions Scenarios. The influence of greenhouse gases and particle pollution on our present and future climate has been widely examined. While both long-lived (e.g., carbon dioxide) and short-lived (e.g., soot) gases and particles affect the climate, other projections of future climate, such as the IPCC reports focus largely on the long-lived gases. This U.S. Climate Change Science Program Synthesis and Assessment Product provides a different emphasis. The authors examine the effect of long-lived greenhouse gases on the global climate based on updated emissions scenarios produced by another CCSP Synthesis and Assessment Product (SAP 2.1a). In these scenarios, atmospheric concentrations of the long-lived greenhouse gases leveled off, or stabilized, at predetermined levels by the end of the twenty-first century (unlike in the IPCC scenarios). However, the projected future temperature changes fall within the same range as those projected for the latest IPCC report. The authors confirm the robust future warming signature and other associated changes in the climate.

This document is part of the Synthesis and Assessment Products (SAP) described in the U.S. Climate Change Science Program (CCSP) Strategic Plan. This report is meant to synthesize and communicate the current state of understanding about the characteristics and implications of uncertainty related to climate change and variability to an audience of policymakers, decision makers, and members of the media and general public with an interest in developing a fundamental understanding of the issue.