1. Department of Earth System Science, Stanford University, Stanford, CA 94305, USA.
2. Woods Institute for the Environment, Stanford University, Stanford, CA 94305, USA.
3. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA.
4. School of the Environment, Washington State University, Vancouver, WA 98686, USA.
5. NASA Goddard Institute for Space Studies, New York, NY 10025, USA.
6. Department of Geography, Dartmouth College, Hanover, NH 03755, USA.