1. Ministry of Education Key Laboratory for Earth System Modelling, Centre for Earth System Science, Tsinghua University, Beijing 100084, China
2. Key Laboratory of Technology in Geo-spatial Information Processing and Application System, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China
3. Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720-3114, USA
4. Joint Centre for Global Change Studies, Beijing 100875, China