adaptive capacity of human and natural systems, which can vary widely in space and time and generally are not as well understood as changes in the physical climate system.
Climate change also poses challenges that set it apart from other risks with which people normally deal. For example, many climate change processes have considerable inertia and long time lags, so it is mainly future generations that will have to deal with the consequences (both positive and negative) of decisions made today. Also, rather than smooth and gradual climate shifts, there is the potential that the Earth system could cross tipping points or thresholds that result in abrupt changes. Some of the greatest risks posed by climate change are associated with these abrupt changes and other climate “surprises” (unexpected changes or impacts), yet the likelihood of such events is not well known. Moreover, there has been comparatively little research on the impacts that might be associated with “extreme” climate change—for example, the impacts that could be expected if global temperatures rise by 10°F (6°C) or more over the next century. Thus, while it seems clear that the Earth’s future climate will be unlike the climate that ecosystems and human societies have become accustomed to during the last 10,000 years, the exact magnitude of future climate change and the nature of its impacts will always remain somewhat uncertain.
Decision makers of all types, including businesses, governments, and individual citizens, are beginning to take actions to reduce the risks posed by climate change—including actions to limit its magnitude and actions to adapt to its impacts. Effective management of climate risks will require decision makers to take actions that are flexible and robust, to learn from new knowledge and experience, and to adjust future actions accordingly. The long time lags associated with climate change and the presence of differential vulnerabilities and capacities to respond to climate change likewise represent formidable management challenges. These challenges also have significant implications for the nation’s climate science enterprise.
Conclusion 2: The nation needs a comprehensive and integrative climate change science enterprise, one that not only contributes to our fundamental understanding of climate change but also informs and expands America’s climate choices.
Research efforts over the past several decades have provided a wealth of information to decision makers about the known and potential risks posed by climate change.