1. Food Security and Environment Program, Woods Institute for the Environment and the Freeman Spogli Institute for International Studies, Stanford University, Stanford, CA 94305, USA.
2. Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA.
3. National Center for Atmospheric Research, Boulder, CO 80305, USA.
4. Woods Institute for the Environment, Stanford University, Stanford, CA 94305, USA.