Strong evidence on climate change underscores need for actions to reduce emissions and begin adapting to impacts, report finds

"These reports show that the state of climate change science is strong," said Ralph J. Cicerone, president of the National Academy of Sciences. "But the nation also needs the scientific community to expand upon its understanding of why climate change is happening, and focus also on when and where the most severe impacts will occur and what we can do to respond."

'Poses Significant Risks'

The compelling case that climate change is occurring and is caused in large part by human activities is based on a strong, credible body of evidence, says Advancing the Science of Climate Change, one of the new reports. While noting that there is always more to learn and that the scientific process is never "closed," the report emphasizes that multiple lines of evidence support scientific understanding of climate change. The core phenomenon, scientific questions, and hypotheses have been examined thoroughly and have stood firm in the face of serious debate and careful evaluation of alternative explanations.

"Climate change is occurring, is caused largely by human activities, and poses significant risks for -- and in many cases is already affecting -- a broad range of human and natural systems," the report concludes. It calls for a new era of climate change science where an emphasis is placed on "fundamental, use-inspired" research, which not only improves understanding of the causes and consequences of climate change but also is useful to decision makers at the local, regional, national, and international levels acting to limit and adapt to climate change. Seven cross-cutting research themes are identified to support this more comprehensive and integrative scientific enterprise.

The report recommends that a single federal entity or program be given the authority and resources to coordinate a national, multidisciplinary research effort aimed at improving both understanding and responses to climate change. The U.S. Global Change Research Program, established in 1990, could fulfill this role, but it would need to form partnerships with action-oriented programs and address weaknesses that in the past have led to research gaps, particularly in the critical area of research that supports decisions about responding to climate change. Leaders of federal climate research should also redouble efforts to deploy a comprehensive climate observing system.

Beyond 'Business as Usual'

Substantially reducing greenhouse gas emissions will require prompt and sustained efforts to promote major technological and behavioral changes, says Limiting the Magnitude of Future Climate Change, another of the new reports. Although limiting emissions must be a global effort to be effective, strong U.S. actions to reduce emissions will help encourage other countries to do the same. In addition, the U.S. could establish itself as a leader in developing and deploying the technologies necessary to limit and adapt to climate change.

An inclusive national policy framework is needed to ensure that all levels of government, the private sector, and millions of households and individuals are contributing to shared national goals. Toward that end, the U.S. should establish a greenhouse gas emissions "budget" that sets a limit on total domestic emissions over a set period of time and provides a clear, directly measurable goal. However, the report warns, the longer the nation waits to begin reducing emissions, the harder and more expensive it will likely be to reach any given emissions target.

The report does not recommend a specific target for a domestic emissions budget, but suggests a range of emissions from 170 to 200 gigatons of carbon dioxide (CO₂) equivalent for the period 2012 through 2050 as a reasonable goal, a goal that is roughly in line with the range of emission reduction targets proposed recently by the Obama administration and members of Congress. Even at the higher end of this range, meeting the target will require a major departure from "business-as-usual" emission trends. The report notes that with the exception of the recent economic downtown, domestic emissions have been rising for most of the past three decades. The U.S. emitted approximately 7 gigatons of CO₂ equivalent in 2008 (the most current year for which such data were available). If emissions continue at that rate, the proposed budget range would be used up well before 2050, the report says.

A carbon-pricing system is the most cost-effective way to reduce emissions. Either cap-and-trade, a system of taxing emissions, or a combination of the two could provide the needed incentives. While the report does not specifically recommend a cap-and-trade system, it notes that cap-and-trade is generally more compatible with the concept of an emissions budget.

Carbon pricing alone, however, is not enough to sufficiently reduce domestic emissions, the report warns. Strategically chosen, complementary policies are necessary to assure rapid progress in key areas such as: increasing energy efficiency; accelerating the development of renewable energy sources; advancing full-scale development of new-generation nuclear power and carbon capture and storage systems; and retrofitting, retiring, or replacing existing emissions-intensive energy infrastructure. Research and development of new technologies that could help reduce emissions more cost effectively than current options also should be strongly supported.

Managing the Risks

Reducing vulnerabilities to impacts of climate change that the nation cannot, or does not, avoid is a highly desirable strategy to manage and minimize the risks, says the third report, Adapting to the Impacts of Climate Change. Some impacts -- such as rising sea levels, disappearing sea ice, and the frequency and intensity of some extreme weather events like heavy precipitation and heat waves -- are already being observed across the country. The report notes that policymakers need to anticipate a range of possible climate conditions and that uncertainty about the exact timing and magnitude of impacts is not a reason to wait to act. In fact, it says boosting U.S. adaptive capacity now can be viewed as "an insurance policy against an uncertain future," while inaction could increase risks, especially if the rate of climate change is particularly large.

Although much of the response to climate change will occur at local and regional levels, a national adaptation strategy is needed to facilitate cooperation and collaboration across all lines of government and between government and other key parties, including the private sector, community organizations, and nongovernmental organizations. As part of this strategy, the federal government should provide technical and scientific resources that are lacking at the local or regional scale, incentives for local and state authorities to begin adaptation planning, guidance across jurisdictions, and support of scientific research to expand knowledge of impacts and adaptation.

Adapting to climate change will be an ongoing, iterative process, the report says, and will involve decision makers at every scale of government and all parts of society. A first step is to identify vulnerabilities to climate change impacts and begin to examine adaptation options that will improve resilience. To build the scientific knowledge base and provide a basis for increasingly effective action in the future, adaptation efforts should be monitored and analyzed to judge successes, problems, and unintended consequences. The report also calls for research to develop new adaptation options and a better understanding of vulnerabilities and impacts on smaller spatial scales.

Adaptation to climate change should not be seen as an alternative to attempts to limit it, the report emphasizes. Rather, the two approaches should be seen as partners, given that society's ability to cope with the impacts of climate change decreases as the severity of climate change increases. At moderate rates and levels of climate change, adaptation can be effective, but at severe rates, adapting to disturbances caused by climate change may not be possible, the report says.

Flexible and Adjustable

The new reports stress that national climate change research, efforts to limit emissions, and adaptation strategies should be designed to be flexible and responsive to new information and conditions in the coming decades. Because knowledge about future climate change and possible impacts will evolve, policies and programs should continually monitor and adjust to progress and consequences of actions.

America's Climate Choices also includes two additional reports that will be released later this year: Informing an Effective Response to Climate Change will examine how to best provide decision makers information on climate change, and an overarching report will build on each of the previous reports and other work to offer a scientific framework for shaping the policy choices underlying the nation's efforts to confront climate change.

The project was requested by Congress and is funded by the National Oceanic and Atmospheric Administration. For more information, visit http://americasclimatechoices.org. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council are independent, nonprofit institutions that provide science, technology, and health policy advice under an 1863 congressional charter. Committee and panel members, who serve pro bono, are chosen by for each study based on their expertise and experience and must satisfy the Research Council's conflict-of-interest standards. The resulting consensus reports undergo external peer review before completion. For more information, visit http://national-academies.org/studycommitteprocess.pdf.