Description:    Geoengineering methods are intended to reduce climate change, which is already having demonstrable effects on ecosystem structure and functioning in some regions. Two types of geoengineering activities that have been proposed are: carbon dioxide (CO 2 ) removal (CDR), which removes CO 2 from the atmosphere, and solar radiation management (SRM, or sunlight reflection methods), which reflects a small percentage of sunlight back into space to offset warming from greenhouse gases (GHGs). Current research suggests that SRM or CDR might diminish the impacts of climate change on ecosystems by reducing changes in temperature and precipitation. However, sudden cessation of SRM would exacerbate the climate effects on ecosystems, and some CDR might interfere with oceanic and terrestrial ecosystem processes. The many risks and uncertainties associated with these new kinds of purposeful perturbations to the Earth system are not well understood and require cautious and comprehensive research. Content Type Journal Article Category Review Paper Pages 1-20 DOI 10.1007/s13280-012-0258-5 Authors Lynn M. Russell, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr. Mail Code 0221, La Jolla, CA 92093-0221, USA Philip J. Rasch, Pacific Northwest National Laboratory, 902 Battelle Boulevard, P. O. Box 999, MSIN K9-34, Richland, WA 99352, USA Georgina M. Mace, Centre for Population Biology, Imperial College London, Ascot, Berks SL5 7PY, UK Robert B. Jackson, Nicholas School of the Environment, Duke University, Durham, NC 27708, USA John Shepherd, Earth System Science, School of Ocean and Earth Sciences, National Oceanography Centre, University of Southampton, European Way, Southampton, SO14 3ZH UK Peter Liss, School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ UK Margaret Leinen, Harbor Branch Oceanographic Institute, 5600 US Rt 1 North, Fort Pierce, FL 34946, USA David Schimel, NEON Inc, 1685 38th Street, Boulder, CO 80305, USA Naomi E. Vaughan, Tyndall Centre for Climate Change Research, School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK Anthony C. Janetos, Joint Global Change Research Institute Pacific Northwest National Laboratory/University of Maryland, 5825 University Research Court, Suite 3500, College Park, MD 20740, USA Philip W. Boyd, NIWA Centre of Chemical & Physical Oceanography, Department of Chemistry, University of Otago, Dunedin, New Zealand Richard J. Norby, Environmental Sciences Division, Oak Ridge National Laboratory, Bethel Valley Road, Bldg. 2040, MS-6301, Oak Ridge, TN 37831-6301, USA Ken Caldeira, Department of Global Ecology, Carnegie Institution, Stanford, CA 94305, USA Joonas Merikanto, Division of Atmospheric Sciences, Department of Physics, University of Helsinki, P.O Box 64, 00014 Helsinki, Finland Paulo Artaxo, Institute of Physics, University of São Paulo, Rua do Matão, Travessa R, 187, São Paulo, SP CEP 05508-090, Brazil Jerry Melillo, The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA M. Granger Morgan, Department of Engineering and Public Policy, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA Journal AMBIO: A Journal of the Human Environment Online ISSN 1654-7209 Print ISSN 0044-7447