Federal Coordinating Lead Authors:
Jeffrey Arnold, U.S. Army Corps of Engineers
Roger Pulwarty, National Oceanic and Atmospheric Administration
Chapter Lead:
Robert Lempert, RAND Corporation
Chapter Authors:
Kate Gordon, Paulson Institute
Katherine Greig, Wharton Risk Management and Decision Processes Center at University of Pennsylvania (formerly New York City Mayor’s Office of Recovery and Resiliency)
Cat Hawkins Hoffman, National Park Service
Dale Sands, Village of Deer Park, Illinois
Caitlin Werrell, The Center for Climate and Security
Review Editor:
Mary Ann Lazarus, Cameron MacAllister Group
Technical Contributors:
Lauren Kendrick, RAND Corporation
Pat Mulroy, Brookings Institution
Costa Samaras, Carnegie Mellon University
Bruce Stein, National Wildlife Federation
Tom Watson, The Center for Climate and Security
Jessica Wentz, Columbia University
USGCRP Coordinators:
Sarah Zerbonne, Adaptation and Decision Science Coordinator
Fredric Lipschultz, Senior Scientist and Regional Coordinator

Reducing Risks Through Adaptation Actions

Many regions and sectors across the United States already experience significant impacts from climate change effects, and many of these effects are projected to increase. By the middle of this century, annual losses in the United States due to climate change could reach hundreds of billions of dollars (Ch. 29: Mitigation).2

Adaptation refers to actions taken at the individual, local, regional, and national levels to reduce risks from even today’s changed climate conditions and to prepare for impacts from additional changes projected for the future.3,4,5,6

Adaptation is a form of risk management. Risk is sometimes defined as the likelihood of an event’s occurrence multiplied by a measure of its consequences for human and natural systems. But because the probabilities and consequences of climate change threats are often not known with precision, and because different people often value the same consequences differently, it is useful to define risk more broadly as “the potential for adverse consequences when something of value is at stake, and the outcome is uncertain.”7 Risk arises from the combination of exposure to climate hazards, sensitivity to those hazards, and adaptive capacity. Adaptation can, however, provide significant societal benefits, reducing by more than half the cost of climate impacts in some sectors (Ch. 29: Mitigation).8

Adaptation involves managing both short- and long-term risks. Many important climate-influenced effects—storm intensity, sea level, frequency of heat waves—have already changed due to past greenhouse gas (GHG) emissions and will continue to change in the decades ahead.3,4 Because several GHGs, in particular carbon dioxide, reside in the atmosphere for decades or longer, many climate-influenced effects are projected to continue changing through 2050, even if GHG emissions were to stop immediately. Thus, climate risk management requires adaptation for the next several decades, independent of the extent of GHG emission reductions. After 2050, the magnitude of changes, and thus the demands on adaptation, begins to depend strongly on the scale of GHG emissions reduction today and over the coming decades.4,9

Individuals, business entities, governments, and civil society as a whole can take adaptation actions at many different scales. Some of these are changes to business operations, adjustments to natural and cultural resource management strategies, targeted capital investments across diverse sectors, and changes to land use and other policies. Adaptation actions can yield beneficial short-term and/or longer-term outcomes in excess of their costs, based on economic returns, ecological benefits, and broader concepts of social welfare and security. Moreover, many strategies can provide multiple benefits, resulting in long-term cost savings. For example, restoring wetlands can provide valuable habitat for fish and wildlife as well as flood protection to nearby communities,10 and conserving mangrove ecosystems can protect coastal communities from damaging storms11 as well as help to store carbon.12

People are not uniformly vulnerable to climate change. Access to resources, culture, governance, and information affects the risks faced by different populations and partly determines the best ways to reduce their risks.13 Achieving the benefits of adaptation can require up-front investments to achieve longer-term savings, engaging with differing stakeholder interests and values, and planning in the face of uncertainty.

Integrating climate risk management into existing design, planning, and operations workflows (or mainstreaming), in contrast to adding novel decision processes for climate adaptation alone, can provide many adaptation benefits.14,15,16 Additional climate risk reduction, particularly under the most severe longer-term climate change projections, emphasizes the need for more and more significant changes to regulatory and policy environments at all scales, to cultural and community resource planning, to economic and financial systems, to technology applications, and to ecosystems.


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