Small global-mean cooling due to volcanic radiative forcing

Gregory, J. M. ORCID: https://orcid.org/0000-0003-1296-8644, Andrews, T., Good, P., Mauritsen, T. and Forster, P. M. (2016) Small global-mean cooling due to volcanic radiative forcing. Climate Dynamics, 47 (12). pp. 3979-3991. ISSN 1432-0894 doi: 10.1007/s00382-016-3055-1

Abstract/Summary

In both the observational record and atmosphere-ocean general circulation model (AOGCM) simulations of the last ∼∼ 150 years, short-lived negative radiative forcing due to volcanic aerosol, following explosive eruptions, causes sudden global-mean cooling of up to ∼∼ 0.3 K. This is about five times smaller than expected from the transient climate response parameter (TCRP, K of global-mean surface air temperature change per W m−2 of radiative forcing increase) evaluated under atmospheric CO2 concentration increasing at 1 % yr−1. Using the step model (Good et al. in Geophys Res Lett 38:L01703, 2011. doi:10.​1029/​2010GL045208), we confirm the previous finding (Held et al. in J Clim 23:2418–2427, 2010. doi:10.​1175/​2009JCLI3466.​1) that the main reason for the discrepancy is the damping of the response to short-lived forcing by the thermal inertia of the upper ocean. Although the step model includes this effect, it still overestimates the volcanic cooling simulated by AOGCMs by about 60 %. We show that this remaining discrepancy can be explained by the magnitude of the volcanic forcing, which may be smaller in AOGCMs (by 30 % for the HadCM3 AOGCM) than in off-line calculations that do not account for rapid cloud adjustment, and the climate sensitivity parameter, which may be smaller than for increasing CO2 (40 % smaller than for 4 × CO2 in HadCM3).

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/55877
Identification Number/DOI	10.1007/s00382-016-3055-1
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > NCAS
Publisher	Springer
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