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Published online by Cambridge University Press:  24 June 2009

Michael E. Mann
Meteorology and Geosciences, Pennsylvania State University


The science underlying global warming, climate change, and the connections between these phenomena are reviewed. Projected future climate changes under various plausible scenarios of future human behavior are explored, as are the potential impacts of projected climate changes on society, ecosystems, and our environment. The economic, security, and ethical considerations relevant to determining the threat posed by climate change are subsequently assessed. The article then discusses the various means available for climate change mitigation, focusing on the relative strengths and weaknesses of various societal alternatives including ‘geoengineering’ and transitioning to less carbon intensive energy sources. The article concludes with the author's views as to what steps might most profitably be taken to avert dangerous anthropogenic interference with Earth's climate, and the ramifications if such steps are not taken.

Research Article
Copyright © Social Philosophy and Policy Foundation 2009

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11 See section of chapter 10 of the Working Group I report: G. A. Meehl et al., “Global Climate Projections,” in Solomon et al., eds., Climate Change 2007: The Physical Science Basis.

12 It is this (flawed) scientific premise that provides the basis for the plot of the disaster movie The Day After Tomorrow, released by Twentieth Century Fox in 2004, written and directed by Roland Emmerich.

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41 The European Union Carbon Emission Trading scheme covers slightly less than half of the EU's energy- and industry-related greenhouse gas emissions. Emission allowances or “permits” are apportioned to major emitters for a period of several years at a time. The scheme requires emitters to monitor and report their emissions, and to return to the government a number of permits that is equivalent to their emissions on an annual basis. Permits can be bought from other emitters or the government as needed, or sold when they are available in excess of what is required by the emitter, thus creating a tradable emissions market. Upon instituting this scheme in 2005, the price of carbon credits began near the low end of the range of SCC estimates cited in the text, but then rose to around US$100/ton, close to the mid-range of estimates, before falling in 2006 (because the credits were believed to have been too generous). These fluctuations all fall within the range of SCC estimates cited in the text.

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57 See Lomborg, Cool It.

58 Hansen et al., “Global Temperature Change.”

59 This example is highlighted by Diamond, Jared in Collapse: How Societies Choose to Fail or Succeed (New York: Viking, 2004)Google Scholar.