Sea spray geoengineering experiments in the geoengineering model intercomparison project (GeoMIP): Experimental design and preliminary results

B. Kravitz (1) , P.M. Forster (2) , A. Jones (3) , A. Robock (4) , K. Alterskjær (5) , Olivier Boucher (6) , A.K.L. Jenkins (2) , H. Korhonen (7) , J.E. Kristjánsson (5) , H. Muri (5) , U. Niemeier (8) , A.-I. Partanen (7) , P.J. Rasch (1) , H. Wang (1) , S. Watanabe (9)

1 Atmospheric Sciences and Global Change Division
2 SEE - School of Earth and Environment [Leeds]
3 MOHC - Met Office Hadley Centre
4 Department of Environmental Sciences [New Brunswick]
5 Department of Geosciences [Oslo]
6 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
7 Kuopio Unit [FMI]
8 MPI-M - Max Planck Institute for Meteorology
9 JAMSTEC - Japan Agency for Marine-Earth Science and Technology

Marine cloud brightening through sea spray injection has been proposed as a method of temporarily alleviating some of the impacts of anthropogenic climate change, as part of a set of technologies called geoengineering. We outline here a proposal for three coordinated climate modeling experiments to test aspects of sea spray geoengineering, to be conducted under the auspices of the Geoengineering Model Intercomparison Project (GeoMIP). The first, highly idealized, experiment (G1ocean-albedo) involves a uniform increase in ocean albedo to offset an instantaneous quadrupling of CO2 concentrations from preindustrial levels. Results from a single climate model show an increased land-sea temperature contrast, Arctic warming, and large shifts in annual mean precipitation patterns. The second experiment (G4cdnc) involves increasing cloud droplet number concentration in all low-level marine clouds to offset some of the radiative forcing of an RCP4.5 scenario. This experiment will test the robustness of models in simulating geographically heterogeneous radiative flux changes and their effects on climate. The third experiment (G4sea-salt) involves injection of sea spray aerosols into the marine boundary layer between 30°S and 30°N to offset 2 W m-2 of the effective radiative forcing of an RCP4.5 scenario. A single model study shows that the induced effective radiative forcing is largely confined to the latitudes in which injection occurs. In this single model simulation, the forcing due to aerosol-radiation interactions is stronger than the forcing due to aerosol-cloud interactions. Key Points Outline of three marine cloud brightening experiments Land-sea contrast is an important feature of marine cloud brightening Direct effect of sea salt injection may be greater than indirect effect ©2013. American Geophysical Union. All Rights Reserved.

Domaines: Climatologie; Géologie appliquée

B. Kravitz, P.M. Forster, A. Jones, A. Robock, K. Alterskjær, et al.. Sea spray geoengineering experiments in the geoengineering model intercomparison project (GeoMIP): Experimental design and preliminary results. Journal of Geophysical Research: Atmospheres, 2013, 118 (19), pp.11175-11186. ⟨10.1002/jgrd.50856⟩. ⟨hal-01099543⟩