Climate model response from the Geoengineering Model Intercomparison Project (GeoMIP)

• Published in: Journal of geophysical research. Atmospheres Vol. 118; no. 15; pp. 8320 - 8332
• Main Authors: Kravitz, Ben, Caldeira, Ken, Boucher, Olivier, Robock, Alan, Rasch, Philip J., Alterskjær, Kari, Karam, Diana Bou, Cole, Jason N. S., Curry, Charles L., Haywood, James M., Irvine, Peter J., Ji, Duoying, Jones, Andy, Kristjánsson, Jón Egill, Lunt, Daniel J., Moore, John C., Niemeier, Ulrike, Schmidt, Hauke, Schulz, Michael, Singh, Balwinder, Tilmes, Simone, Watanabe, Shingo, Yang, Shuting, Yoon, Jin-Ho
• Format: Journal Article
• Language: English
• Published: Hoboken, NJ Blackwell Publishing Ltd 16-08-2013; John Wiley & Sons; American Geophysical Union
• Subjects: Anthropogenic factors; Carbon dioxide; Climate change; Climate effects; Climate models; Computer simulation; Earth Sciences; Earth, ocean, space; Evaporation; Exact sciences and technology; External geophysics; Geoengineering; Geophysics; Global temperatures; Global warming; Greenhouse effect; Greenhouse gases; Heat tolerance; Hydrologic cycle; Hydrology; Meteorology; model intercomparison; Offsets; Precipitation; Reduction; Sciences of the Universe; Sea ice; Solar radiation; Surface temperature; Tropical environments; Arctic Ocean; PN, Arctic; Thermal comfort; Gas emission; atmospheric precipitation; Insolation; Carbon dioxide; Regional scope; tropical zone; solar radiation; Surface temperature; Climate models; anomalies; greenhouse gas; intensity; Geoengineering; Bioclimatology; sea ice; Effect on climate; Polar region; primary productivity; evaporation; Comparative study; stability; Anthropogenic factor
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/jgrd.50646

Solar geoengineering—deliberate reduction in the amount of solar radiation retained by the Earth—has been proposed as a means of counteracting some of the climatic effects of anthropogenic greenhouse gas emissions. We present results from Experiment G1 of the Geoengineering Model Intercomparison Project, in which 12 climate models have simulated the climate response to an abrupt quadrupling of CO2 from preindustrial concentrations brought into radiative balance via a globally uniform reduction in insolation. Models show this reduction largely offsets global mean surface temperature increases due to quadrupled CO2 concentrations and prevents 97% of the Arctic sea ice loss that would otherwise occur under high CO2 levels but, compared to the preindustrial climate, leaves the tropics cooler (−0.3 K) and the poles warmer (+0.8 K). Annual mean precipitation minus evaporation anomalies for G1 are less than 0.2 mm day−1 in magnitude over 92% of the globe, but some tropical regions receive less precipitation, in part due to increased moist static stability and suppression of convection. Global average net primary productivity increases by 120% in G1 over simulated preindustrial levels, primarily from CO2 fertilization, but also in part due to reduced plant heat stress compared to a high CO2 world with no geoengineering. All models show that uniform solar geoengineering in G1 cannot simultaneously return regional and global temperature and hydrologic cycle intensity to preindustrial levels.
Key Points
Temperature reduction from uniform geoengineering is not uniform
Geoengineering cannot offset both temperature and hydrology changes
NPP increases mostly due to CO2 fertilization