1. School of Geography and Planning, Sun Yat-sen University, Guangzhou 510275, China
2. Department of Geographical Sciences, University of Maryland, College Park, Maryland 20742, United States
3. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
4. Center for Energy and Environmental Sciences (IVEM), Energy and Sustainability Research Institute Groningen (ESRIG), University of Groningen, Groningen 9747 AG, Netherlands
5. Department of Earth System Science, Tsinghua University, Beijing 100084, China