The final report reaffirms that "the preponderance of scientific evidence points to human activities -- especially the release of carbon dioxide and other greenhouse gases into the atmosphere -- as the most likely cause for most of the global warming that has occurred over the last several decades. This trend cannot be explained by natural factors such as internal climate variability or changes in incoming energy from the sun. The report adds that the impacts of climate change on human and natural systems can generally be expected to intensify with warming."
According to the report, while it recognized that climate change is inherently a global issue requiring an international response, the committee focused on the charge from Congress to identify steps and strategies that
According to the Committee, "Substantial reductions of greenhouse gas emissions should be among the highest priorities in the national response." Although the exact magnitude and speed of reductions will depend on how much risk society deems acceptable, "it would be imprudent to delay taking action." The Committee cited many reasons for not waiting, including that the faster emissions are reduced, the lower the risks. And because the effects of greenhouse gases can take decades to manifest and then persist for hundreds or even thousands of years, "waiting for impacts to occur before taking action will likely be too late for meaningful mitigation. Beginning emissions reductions soon will also lower the pressure to make steeper and costlier cuts later." Carnesale said, "It is our judgment that the most effective strategy is to begin ramping down emissions as soon as possible."
The Committee said, state and local efforts currently under way or being initiated to reduce greenhouse gas emissions are "potentially quite significant but unlikely to yield outcomes comparable to what could be achieved with a strong federal effort." It said the most efficient way to accelerate emissions reductions is through "a nationally uniform price on greenhouse gas emissions with a price trajectory sufficient to spur investments in energy efficiency and low-carbon technologies. Having such policies in place is crucial to guide investments in energy infrastructure that will largely determine the direction of greenhouse gas emissions for decades to come."
The Committee deemed the risks of sticking to "business as usual" to be a much greater concern than the risks associated with a strong response. They said, "Most policy responses could be reversed if they prove to be more stringent than is needed, but adverse changes to the climate system are difficult or impossible to undo." It also said that "uncertainty in projecting the severity, location, or time of climate change impacts is not a reason for inaction. On the contrary, uncertainty about future risks could be a compelling reason for taking action given that abrupt, unanticipated, or more severe impacts could occur."
The committee emphasized that, aggressive cuts in greenhouse gas emissions would reduce the need for adaptation but not eliminate it and urged the nation to mobilize now to reduce vulnerability to climate change impacts. While adaptation planning largely occurs at the state and local level, the Federal government should help coordinate these efforts and develop a national adaptation strategy.
In addition, they said the Federal government should maintain an integrated portfolio of research programs aimed at increasing understanding of the causes and consequences of climate change and developing tools to limit climate change and adapt to its impacts. The government also needs to take the lead in collecting and sharing climate change information to ensure that pertinent knowledge is used to inform decisions. Public and private sector engagement through broad-based deliberative processes is essential as well. These processes should include transparent analyses of climate change information, an explicit discussion of uncertainties, and consideration of how decisions will be affected by differing personal values.
The Committee said, "Because emissions reductions in the U.S. alone will not be adequate to avert dangerous climate change risks, U.S. leadership needs to remain actively engaged in international climate change response efforts. If the
The final report in the series builds upon the four previous
Jennifer Morgan, director of the Climate and Energy Program, World Resources Institute (WRI) said, "This report, from one of America's leading scientific institutions, provides another stark reminder of the increasing risks associated with human-caused climate change. The report delivers a clear message that the federal government should take an active role in managing these very serious risks. We need policies to reduce greenhouse gas emissions, as we advance adaptation measures and develop technologies to respond to the changing world. We don't wait for the flood to arrive or the fire to spark before we buy insurance. The same should be true for climate change."