1. a International Institute for Applied Systems Analysis (IIASA) , Am Schlossplatz 1, A-2361 , Laxenburg , Austria
2. b School of Geography, University of Leeds , University Road, Leeds , LS2 9JT , UK
3. c Joint Research Centre of the European Commission , TP 266Via Enrico Fermi 2749, I-21027 , Ispra (VA) , Italy