Economic aspects of global warming in a post-Copenhagen environment
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Contributed by William D. Nordhaus, May 10, 2010 (sent for review February 4, 2010)

Abstract
The science of global warming has reached a consensus on the high likelihood of substantial warming over the coming century. Nations have taken only limited steps to reduce greenhouse gas emissions since the first agreement in Kyoto in 1997, and little progress was made at the Copenhagen meeting in December 2009. The present study examines alternative outcomes for emissions, climate change, and damages under different policy scenarios. It uses an updated version of the regional integrated model of climate and the economy (RICE model). Recent projections suggest that substantial future warming will occur if no abatement policies are implemented. The model also calculates the path of carbon prices necessary to keep the increase in global mean temperature to 2 °C or less in an efficient manner. The carbon price for 2010 associated with that goal is estimated to be $59 per ton (at 2005 prices), compared with an effective global average price today of around $5 per ton. However, it is unlikely that the Copenhagen temperature goal will be attained even if countries meet their ambitious stated objectives under the Copenhagen Accord.
Footnotes
- 1E-mail: william.nordhaus{at}yale.edu.
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Author contributions: W.D.N. designed research, performed research, analyzed data, and wrote the paper.
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The author declares no conflict of interest.
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This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1005985107/-/DCSupplemental.
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*The equations of the model, along with key assumptions, are available in SI Appendix . The model is also available as an Excel spreadsheet downloadable from the author's website (http://www.econ.yale.edu/~nordhaus/homepage/homepage.htm). The results reported here are based on the RICE model version of April 25, 2010.
Freely available online through the PNAS open access option.