[1] Fdn Eni Enrico Mattei, Milan, Italy
[2] Int Ctr Theoret Phys, Trieste, Italy
[3] Catholic Univ Louvain, Ctr Econ Studies, B-3000 Louvain, Belgium
[4] Univ Hamburg, Res Unit Sustainabil & Global Change, Hamburg, Germany
[5] Ctr Marine & Atmsopher Sci, Hamburg, Germany
[6] Vrije Univ Amsterdam, Inst Environm Sci, NL-1081 HV Amsterdam, Netherlands
[7] Carnegie Mellon Univ, Pittsburgh, PA 15213 USA