approaches for addressing future climate uncertainties and an overview of the remainder of the report.

CLIMATE CHANGE EFFECTS

There is broad scientific consensus on many climate change topics.6 These climate certainties include measured or observed (1) higher surface, troposphere, and ocean temperatures; (2) more precipitation and drought extremes; (3) melting of mountain glaciers, Arctic sea ice, and ice sheets; and (4) a rising sea level.7 Each of the four certainties has the potential to impact U.S. naval forces’ operations and installations; if continued as projected, many will have national security implications as well. In most cases, the effects of climate change can be summarized through the effects on water—prolonged droughts, more intense storms and floods, melting ice, and/or changing ocean conditions, including ocean acidification. Many of these climate change effects and their resulting impacts are summarized in Box 1.1 and illustrated in Figures 1.1 and 1.2. In many regions of the world, the impact of climate change is likely to further exacerbate the preexisting stress on water supplies and the associated mounting pressures of population growth.8 While these issues and other potential climate change impacts are important, this report is focused through the lens of relevance and implications for U.S. naval forces.

6

For example, the National Research Council of the National Academies has recently released the first four reports from a congressionally mandated suite of studies known as America’s Climate Choices. These studies are discussed later in this chapter, and additional information is provided at the America’s Climate Choices website: http://americasclimatechoices.org/, accessed July 28, 2010.

7

The U.S. Global Change Research Program, composed of 13 federal agencies, reported in 2009 that climate-related changes are already being observed in every region of the world, including the United States and its coastal waters. Among these physical changes are increases in heavy downpours, rising temperature and sea level, rapidly retreating glaciers, thawing permafrost, lengthening growing seasons, lengthening ice-free seasons in the oceans and on lakes and rivers, earlier snowmelt, and alterations in river flows. See Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson, 2009, Global Climate Change Impacts in the United States, Cambridge University Press, New York, pp. 25-47.

8

For example, Columbia University’s Center for International Earth Science Information Network (CIESIN) has compiled information from IPCC assessments, the 2005 World Bank report Natural Disaster Hotspots: A Global Risk Analysis, and CIESIN’s gridded world population data sets to present a projected geographic distribution of vulnerability in 2050. In presentations to the committee, CIESIN representatives reported that global population nearly doubled from 1968 through 2008, and that by 2048 it could grow another 40 percent, to more than 9 billion people, adding even greater stresses to water and food supplies (Robert S. Chen, Center for International Earth Science Information Network, Columbia University, “Human Dimensions of Climate Change,” and Marc Levy, Center for International Earth Science Information Network, Columbia University, “Climate Change and U.S. National Security,” presentations to the committee, November 19, 2009, Washington, D.C.). CIESIN also reported that population increases are fastest in areas most vulnerable to intense storms and flooding (e.g., coastal areas, islands, and river basins). The CIESIN analysis combines its population data sets with IPCC-projected climate-change-related vulnerabilities, economic data, and past disaster-related losses to identify areas at relative high risk from one or more hazards.



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