Box 31 Two Myths about Climate Change continued

Figure 3-2. Relative Vulnerability to Tropical Cyclones, 1980-2000" Average annual deaths

• Bangladesh

u China

• Haiti ,-t • Pakistan * . .. ■ '


Solomon Islands

El Salvador,

• . •1

• •

Puerto Rico New Zealand • Mauritius

0.1 1 10 102 Population exposed to tropical cyclones (millions)

Source: N. Pelling, A. Maskrey, P. Ruiz, and L. Hall, Reducing Disaster Risk: A Challenge for Development, A Global Report (New York: United Nations Development Program, Bureau for Crisis Prevention and Recovery, 2004 []).

a. Countries near the diagonal line, such as India and the Philippines, exhibited vulnerability similar to the United States. Countries below the diagonal line, including China, Cuba, and Japan, were less vulnerable than the United States.

and material resources toward coping with climate change. In general, severe climate change impacts affecting wealthy nations portend diversion of foreign aid to domestic projects, generating greater potential for environmental refugees to attempt to migrate to wealthy countries.

1. Committee on Abrupt Climate Change, Abrupt Climate Change: Inevitable Surprises (Washington: National Academy Press, 2002).

3. IPCC, "Summary for Policymakers," in Climate Change 2007: Impacts, Adaptation and Vulnerability; IPCC, "Summary for Policymakers," in Climate Change 2007: The Physical Science Basis; Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by Susan Solomon and others (Cambridge University Press, 2007), pp. 1-18; 7-22.

5. J. Alcamo and others, "Europe," in Climate Change 2007: Impacts, Vulnerability and Sustainability: Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by M. L. Parry and others (Cambridge University Press, 2007).

6. P. A. Stott, D. A. Stone, and M. R. Allen, "Human Contribution to the European Heatwave of 2003," Nature 432 (2004): 610-14.

7. R. J. Nicholls, "Coastal Flooding and Wetland Loss in the 21st Century: Changes under the SRES Climate and Socio-Economic Scenario," Global Environmental Change 14 (2004): 69-86; R. J. Nicholls and others, "Coastal Systems and Low-Lying Areas," in Climate Change 2007: Impacts, Adaptation and Vulnerability, pp. 315-56.

considers continued growth of man-made greenhouse gas emissions under rapid economic growth, technological development, and ongoing efficiency improvements, but with significant continued reliance on fossil fuels.5 Atmospheric carbon dioxide (CO2) rises to a concentration of about 700 parts per million (ppm)—2.5 times the preindustrial concentration—by the end of the twenty-first century, which the AR4 projects would be associated with a global surface temperature increase of 1.7 to 4.4°C (3.1 to 7.9°F), with a best estimate of 2.8°C (5.0°F).6 Although SRES scenarios assume that society takes no actions to limit climate change, it is possible for society to enact policies that would limit emissions significantly below the level of the A1B projection.7

An unavoidable caveat of basing our impacts scenarios on IPCC model projections is that the regional projections are continental or subcontinental in scale and impacts are generally described in aggregate. How climate in any specific location might deviate from the subcontinental average is uncertain; it might not be possible to predict correctly the consequences of climate change for particular locales from the existing scientific literature. As a result, assessing the security implications of climate change requires making some assumptions regarding the impacts that may occur in a given geopolitical arena.

Two of the impacts scenarios outlined here project changes to the year 2040. Although we choose a particular emissions scenario as a reference case, temperature increases based on the various emissions scenarios examined by the IPCC do not diverge significantly by the year 2040, as past emissions dominate temperature forcing over this short time frame. Uncertainty in the temperature outcome within this time frame is related less to greenhouse gas emissions than to uncertainty about physical climate sensitivity to greenhouse gas forcing and the response of individual climate components (for example, ice sheets, sea level, or storm systems) to a given degree of warming.8 Over the longer time frame (about one century) of the most severe scenario, divergence of different emissions scenarios is significant and A1B emerges as a mid-range projection of temperature change, which we adjust in scenario 3 to account for potential underestimation as described below.

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