1. R. Naylor, W. Falcon, Boston Rev.33, 13 (2008).
2. We approximated the main growing season to be summer in the extratropics. Hence north of the equator we used the three-month average temperature June through August (and for south of the equator we used December through February) periods that broadly capture growing season conditions for many crops.
3. IPCC Fourth Assessment Report: Synthesis published online 17 November 2007 www.ipcc.ch/ipccreports/ar4-syr.htm.
4. World Development Report 2008: Agriculture for Development 2007
5. W. Easterlinget al., in Climate Change 2007: Impacts, Adaptation, and Vulnerability, M. Parry et al., Eds. (Cambridge Univ. Press, New York, 2007), p. 976.