The world’s leading climate scientists have reached consensus that human activity in the form of greenhouse gas (GHG) emissions is warming the planet in ways that will have profound and unsettling impacts on natural resources, energy use, ecosystems, economic activity, and potentially quality of life. The earth’s climate is always in a state of flux, but what is of concern today is the rapid rate of change and the unabated contribution of human activity to its occurrence.Many studies have already examined the potential impacts of climate change on broad sectors of the economy, such as agriculture and forestry, but few have studied the impacts on transportation.

The primary focus of this report is on the consequences of climate change1 for the infrastructure and operations of U.S. transportation.2 The report provides transportation professionals with an overview of the scientific consensus on those current and future climate changes of particular relevance to U.S. transportation, including the limitations of present scientific understanding as to their precise timing, magnitude, and geographic location; identifies potential impacts on U.S. transportation and adaptation options; and offers recommendations for both research and actions that can be taken to prepare for climate change. The report also summarizes previous work on strategies for reducing transportation-related emissions of carbon dioxide (CO2)—the primary GHG—that contribute to climate change, a relatively well-researched area (see Appendix B).

Climate change will have significant impacts on transportation, affecting the way U.S. transportation professionals plan, design, construct, operate, and maintain infrastructure. Decisions taken today, particularly those related to the redesign and retrofitting of existing or the location and design of new transportation infrastructure,will affect how well the system adapts to climate change far into the future. Focusing on the problem now should help avoid costly future investments and disruptions to operations. The primary objective of this report is to provide guidance for transportation decision makers on how best to proceed.