Solar-induced versus internal variability in a coupled climate model

Drijfhout, S.S., Haarsma, R.J., Opsteegh, J.D. and Selten, F.M. (1999) Solar-induced versus internal variability in a coupled climate model. Geophysical Research Letters, 26 (2), 205-208. (doi:10.1029/1998GL900277).

Abstract

A series of experiments is conducted in which a variable solar irradiance is imposed for a range of frequencies and amplitudes in a simplified coupled General Circulation Model. For realistic amplitudes solar forcing dominates over internal variability in global mean surface air temperature (GM-SAT) beyond decadal timescales. Its impact increases with period up to 50 years. Evidence is found for interactions between climate variations with different timescales. A weak 22-yr solar irradiance variation excites a significant spectral peak with a 70-yr period in GM-SAT. On the regional-scale the internal variability dominates at all timescales. Patterns of internal variability and their associated variance are robust for a variable solar forcing. The temporal spectra, however, are sensitive to such forcing. Some preferred decadal timescales of the internal modes of the coupled system disappear when the solar forcing varies.

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Contributors

Author: S.S. Drijfhout

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