Martin I. Hoffert,1* Ken Caldeira,3 Gregory Benford,4 David R. Criswell,5Christopher Green,6 Howard Herzog,7 Atul K. Jain,8 Haroon S. Kheshgi,9Klaus S. Lackner,10 John S. Lewis,12 H. Douglas Lightfoot,13 Wallace Manheimer,14John C. Mankins,15 Michael E. Mauel,11 L. John Perkins,3 Michael E. Schlesinger,8Tyler Volk,2 Tom M. L. Wigley16

Stabilizing the carbon dioxide-induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energydemand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (~1013 watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission-free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non-primary power technologies that could contribute to climate stabilization include efficiency improvements,hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development.

1 Department of Physics,
2 Department of Biology, New York University, New York, NY 10003, USA.
3 Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
4 Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA.
5 Institute of Space Systems Operations, University of Houston, Houston, TX 77204, USA.
6 Department of Economics, McGill University, Montreal, Quebec H3A 2T7, Canada.
7 MIT Laboratory for Energy and the Environment, Cambridge, MA 02139, USA.
8 Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
9 ExxonMobil Research and Engineering Company, Annandale, NJ 08801, USA.
10 Department of Earth and Environmental Engineering,
11 Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA.
12 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
13 Centre for Climate and Global Change Research, McGill University, Montreal, Quebec H3A 2K6, Canada.
14 Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375, USA.
15 NASA Headquarters, Washington, DC 20546, USA.
16 National Center for Atmospheric Research, Boulder, CO 80307, USA.
*   To whom correspondence should be addressed. E-mail: marty.hoffert@nyu.edu