1Max Planck Institute for Meteorology, Hamburg, Germany
2University of Oslo, Oslo, Norway
3Laboratoire des Sciences du Climat et l'Environnement, CEA, CNRS, UVSQ, Gif-sur-Yvette, France
4Met Office Hadley Centre, Exeter, UK
5Norwegian Meteorological Institute, Oslo, Norway
6Cicero, Oslo, Norway
7Max Planck Institute for Chemistry, Mainz, Germany
*now at: Laboratoire de Météorologie Dynamique, Institut Pierre Simon Laplace/CNRS, Paris, France
**now at: Institute for Advanced Sustainability Studies, Potsdam, Germany
Received: 13 Jan 2012 – Discussion started: 25 Jan 2012
Abstract. In this study we compare the response of four state-of-the-art Earth system models to climate engineering under scenario G1 of two model intercomparison projects: GeoMIP (Geoengineering Model Intercomparison Project) and IMPLICC (EU project "Implications and risks of engineering solar radiation to limit climate change"). In G1, the radiative forcing from an instantaneous quadrupling of the CO2 concentration, starting from the preindustrial level, is balanced by a reduction of the solar constant. Model responses to the two counteracting forcings in G1 are compared to the preindustrial climate in terms of global means and regional patterns and their robustness. While the global mean surface air temperature in G1 remains almost unchanged compared to the control simulation, the meridional temperature gradient is reduced in all models. Another robust response is the global reduction of precipitation with strong effects in particular over North and South America and northern Eurasia. In comparison to the climate response to a quadrupling of CO2 alone, the temperature responses are small in experiment G1. Precipitation responses are, however, in many regions of comparable magnitude but globally of opposite sign.
Revised: 08 May 2012 – Accepted: 14 May 2012 – Published: 06 Jun 2012
Schmidt, H., Alterskjær, K., Bou Karam, D., Boucher, O., Jones, A., Kristjánsson, J. E., Niemeier, U., Schulz, M., Aaheim, A., Benduhn, F., Lawrence, M., and Timmreck, C.: Solar irradiance reduction to counteract radiative forcing from a quadrupling of CO2: climate responses simulated by four earth system models, Earth Syst. Dynam., 3, 63-78, doi:10.5194/esd-3-63-2012, 2012.