[1] Columbia Univ, Goddard Inst Space Studies, New York, NY 10025 USA
[2] Int Inst Appl Syst Anal, A-2361 Laxenburg, Austria
[3] INRA, Unite Rech Agron 874, F-63100 Clermont Ferrand, France
[4] Commonwealth Sci & Ind Res Org Sustainable Ecosys, Canberra, ACT 2601, Australia