The Potential Consequences of Climate Change for the US—Results from the National Assessment

Humanity's influence on the global climate is projected to grow significantly during the 21st century. To provide a basis for beginning to consider possible adaptive responses, the United States undertook the National Assessment of the Potential Consequences of Climate Variability and Change. This landmark effort has begun a national process of research, analysis, and dialogue about the coming changes in climate, their impacts, and what Americans can do to adapt to an uncertain and continuously changing climate. The Assessment, sponsored by the United States Global Change Research Program (USGCRP) was conducted under the leadership of the National Assessment Synthesis Team (NAST), which was a committee of experts drawn from governments, universities, industry, and non-governmental organizations. Key findings of the assessment included: · Significantly greater warming is projected for the 21st century than for the 20th century,. · Many ecosystems are highly vulnerable to the projected rate and magnitude of climate change. · Changes in the availability and reliability of water resources are an issue in every region of the country. · The agriculture sector is likely to be able to adapt to climate change, with overall US crop productivity very likely to increase over the next few decades. · Forest productivity is likely to increase over the next several decades in some areas as trees respond to higher carbon dioxide levels. Over the longer term, changes in larger-scale processes such as fire, insects, droughts, and disease will possibly decrease forest productivity. · Climate change and the resulting rise in sea level are likely to exacerbate threats to buildings, roads, powerlines, and other infrastructure in climatically sensitive places. · A range of negative health impacts is possible from climate change, but adaptation is likely to help protect much of the US population. · Climate change is very likely to magnify the cumulative impacts of other stresses. Despite the progress made, uncertainties remain and surprises are expected. Further research would improve understanding and the ability to project societal and ecosystem impacts, while also providing the public with additional useful information about options for adaptation.

Acknowledgements: The author is on assignment from Lawrence Livermore National Laboratory, Livermore CA. This paper was prepared under the auspices of the Department of Energy's Environmental Sciences Division by the Lawrence Livermore National Laboratory under contract W-7405-ENG-48.