The hydrological impact of geoengineering in the Geoengineering Model Intercomparison Project (GeoMIP)
Journal of Geophysical Research Atmospheres
American Geophysical Union
This is the final version of the article. Available from the American Geophysical Union via the DOI in this record.
The hydrological impact of enhancing Earth's albedo by solar radiation management is investigated using simulations from 12 Earth System models contributing to the Geoengineering Model Intercomparison Project (GeoMIP). We contrast an idealized experiment, G1, where the global mean radiative forcing is kept at preindustrial conditions by reducing insolation while the CO <inf>2</inf> concentration is quadrupled to a 4×CO<inf>2</inf> experiment. The reduction of evapotranspiration over land with instantaneously increasing CO<inf>2</inf> concentrations in both experiments largely contributes to an initial reduction in evaporation. A warming surface associated with the transient adjustment in 4×CO<inf>2</inf> generates an increase of global precipitation by around 6.9% with large zonal and regional changes in both directions, including a precipitation increase of 10% over Asia and a reduction of 7% for the North American summer monsoon. Reduced global evaporation persists in G1 with temperatures close to preindustrial conditions. Global precipitation is reduced by around 4.5%, and significant reductions occur over monsoonal land regions: East Asia (6%), South Africa (5%), North America (7%), and South America (6%). The general precipitation performance in models is discussed in comparison to observations. In contrast to the 4×CO<inf>2</inf> experiment, where the frequency of months with heavy precipitation intensity is increased by over 50% in comparison to the control, a reduction of up to 20% is simulated in G1. These changes in precipitation in both total amount and frequency of extremes point to a considerable weakening of the hydrological cycle in a geoengineered world. Key Points Geoengineering leads to a weakening of the hydrologic cycle Evapotranspiration changes important for initial reduction of precipitation Considerable reduction of monsoonal precipitation over land with SRM ©2013. American Geophysical Union. All Rights Reserved.
We thank all participants of the Geoengineering Model Intercomparison Project and their model development teams, the CLIVAR/WCRP Working Group on Coupled Modeling for endorsing GeoMIP, and the scientists managing the Earth System Grid data nodes who have assisted with making GeoMIP output available. We further acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups for producing and making available their model output. For CMIP, the U.S. Department of Energy’s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. We thank the TRMM Online Visualization and Analysis System (TOVAS) and the GPCC Global Precipitation Climatology Centre for providing the rainfall data set. The participation of J. Fasullo is supported by NASA Award NNG06GB91G. J. Haywood and A. Jones were supported by the joint DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). K. Alterskjær, D. B. Karam, J. E. Kristjánsson, U. Niemeier, H. Schmidt, and M. Schulz received funding from the European Unions Seventh Framework Programme (FP7/2007-2013) under grant agreement 226567-IMPLICC. K. Alterskjær and J.E. Kristjánsson received support from the Norwegian Research Council’s Programme for Supercomputing (NOTUR) through a grant of computing time. B. Kravitz is supported by the Fund for Innovative Climate and Energy Research. Simulations performed by B. Kravitz were supported by the NASA High-End Computing (HEC) Program through the NASA Center for Climate Simulation (NCCS) at Goddard Space Flight Center. Computer resources for P.J. Rasch, B. Singh, and J.-H. Yoon were provided by the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract DE-AC02-05CH11231. J.-H. Yoon was further supported by the NERSC. D. Ji and J. Moore thank all members of the BNU-ESM model group, as well as the Center of Information and Network Technology at Beijing Normal University for assistance in publishing the GeoMIP data set. H. Muri was supported by the EU 7th Framework Programme grant agreement 306395, EuTRACE. A. Robock is supported by the U.S. National Science Foundation grant AGS-1157525. S. Watanabe was supported by SOUSEI Program, MEXT, Japan, and the Earth Simulator was used for the simulations of MIROC-ESM. Finally, we thank Gary Strand for CCSM4 output formatting and James Hurrell for supporting this study. The National Center for Atmospheric Research is funded by the National Science Foundation. We thank all reviewers and Govindasamy Bala for useful suggestions to the paper.
Journal of Geophysical Research Atmospheres, 2013, Vol. 118, Issue 19, pp. 11036 - 11058