1. Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA 94720, USA.
2. Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
3. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA.
4. Earth Institute, Columbia University, New York, NY 10025, USA.