http://www.earth-syst-dynam.net/3/63/2012/esd-3-63-2012.html

Earth Syst. Dynam., 3, 63-78, 2012
www.earth-syst-dynam.net/3/63/2012/doi:10.5194/esd-3-63-2012 © Author(s)
2012. This work is distributed under the Creative Commons Attribution 3.0
License.

Solar irradiance reduction to counteract radiative forcing from a
quadrupling of CO 2 : climate responses simulated by four earth system
models

H. Schmidt 1 , K. Alterskjær 2 , D. Bou Karam 3 , O. Boucher 4,* , A. Jones
4 , J. E. Kristjánsson 2 , U. Niemeier 1 , M. Schulz 5 , A. Aaheim 6 , F.
Benduhn 7 , M. Lawrence 7,** , and C. Timmreck 1

1 Max Planck Institute for Meteorology, Hamburg, Germany 2 University of
Oslo, Oslo, Norway 3 Laboratoire des Sciences du Climat et l'Environnement,
CEA, CNRS, UVSQ, Gif-sur-Yvette, France 4 Met Office Hadley Centre, Exeter,
UK 5 Norwegian Meteorological Institute, Oslo, Norway 6 Cicero, Oslo,
Norway 7 Max 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

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 CO 2 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 CO 2 alone, the temperature responses

are small in experiment G1. Precipitation responses are, however, in many
regions of comparable magnitude but globally of opposite sign.

Final Revised Paper (PDF, 3712 KB) Discussion Paper (ESDD)

Citation: 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 CO 2 : climate responses simulated
by four earth system models, Earth Syst. Dynam., 3, 63-78,
doi:10.5194/esd-3-63-2012, 2012. Bibtex EndNote Reference Manager XML

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