Transient Climate Response in a Two-Layer Energy-Balance Model. Part II: Representation of the Efficacy of Deep-Ocean Heat Uptake and Validation for CMIP5 AOGCMs

Geoffroy, Olivier; Saint‐Martin, David; Bellon, Gilles; Voldoire, Aurore; Olivié, Dirk; Tytéca, S.

doi:10.1175/jcli-d-12-00196.1

Cited by 151 publications

(285 citation statements)

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“…A number of studies have attributed this strengthening of the feedbacks to changes in the pattern of surface warming (Williams et al, 2008), mainly in the eastern tropical Pacific where an intensification of warming can occur after a few decades, but also in other regions such as the Southern Ocean . The impact of variations in ocean heat uptake has also been suggested to be a contributing factor (Geoffroy et al, 2013;Held et al, 2010;Winton et al, 2010).…”

Section: Gregory Plotsmentioning

confidence: 99%

“…A limitation of this approach is that it assumes that the response of climate to a forcing is linear after the first 20 years, which has been shown to be unlikely in longer simulations of several decades or centuries Armour et al, 2013;. However, a comparison of the difference in temperature response to upper-and deep-ocean heat uptake and its contribution to the relationship between net radiative flux change (N) and global temperature change ( T ) in Geoffroy et al (2013) indicated that the method of of fitting two separate linear models to the early and subsequent (N, T ) data gives a good approximation of T g eq , F and α as they have been calculated here. A study by Li et al (2013) also found that, using the Gregory plot methodology, T g eq was estimated to within 10 % of its ac- tual value, obtained by running the simulation very close to equilibrium (∼ 6000 years).…”

Section: Gregory Plotsmentioning

confidence: 99%

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Emulation of long-term changes in global climate: application to the late Pliocene and future

et al. 2017

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Abstract. Multi-millennial transient simulations of climate changes have a range of important applications, such as for investigating key geologic events and transitions for which high-resolution palaeoenvironmental proxy data are available, or for projecting the long-term impacts of future climate evolution on the performance of geological repositories for the disposal of radioactive wastes. However, due to the high computational requirements of current fully coupled general circulation models (GCMs), long-term simulations can generally only be performed with less complex models and/or at lower spatial resolution. In this study, we present novel longterm "continuous" projections of climate evolution based on the output from GCMs, via the use of a statistical emulator. The emulator is calibrated using ensembles of GCM simulations, which have varying orbital configurations and atmospheric CO 2 concentrations and enables a variety of investigations of long-term climate change to be conducted, which would not be possible with other modelling techniques on the same temporal and spatial scales. To illustrate the potential applications, we apply the emulator to the late Pliocene (by modelling surface air temperature -SAT), comparing its results with palaeo-proxy data for a number of global sites, and to the next 200 kyr (thousand years) (by modelling SAT and precipitation). A range of CO 2 scenarios are prescribed for each period. During the late Pliocene, we find that emulated SAT varies on an approximately precessional timescale, with evidence of increased obliquity response at times. A comparison of atmospheric CO 2 concentration for this period, estimated using the proxy sea surface temperature (SST) data from different sites and emulator results, finds that relatively similar CO 2 concentrations are estimated based on sites at lower latitudes, whereas higher-latitude sites show larger discrepancies. In our second illustrative application, spanning the next 200 kyr into the future, we find that SAT oscillations appear to be primarily influenced by obliquity for the first ∼ 120 kyr, whilst eccentricity is relatively low, after which precession plays a more dominant role. Conversely, variations in precipitation over the entire period demonstrate a strong precessional signal. Overall, we find that the emulator provides a useful and powerful tool for rapidly simulating the long-term evolution of climate, both past and future, due to its relatively high spatial resolution and relatively low computational cost. However, there are uncertainties associated with the approach used, including the inability of the emulaPublished by Copernicus Publications on behalf of the European Geosciences Union. 1540 N. S. Lord et al.: Emulation of long-term changes in global climate tor to capture deviations from a quasi-stationary response to the forcing, such as transient adjustments of the deep-ocean temperature and circulation, in addition to its limited range of fixed ice sheet configurations and its requirement for prescribed atmos...

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Section: Gregory Plotsmentioning

confidence: 99%

Section: Gregory Plotsmentioning

confidence: 99%

Emulation of long-term changes in global climate: application to the late Pliocene and future

et al. 2017

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“…That is, the surface temperature change and the ocean heat uptake hold a linear relation under constant radiative forcing in the two-layer model. Geoffroy et al (2013a) applied this model to analyze the CMIP5 AOGCM simulations and showed that the two-layer models tuned to emulate the global mean surface temperature response of AOGCMs in the abrupt4xCO2 experiment can also emulate the result of the slowly increasing CO 2 (1pctCO2) experiment reasonably well. This supports the assumption that the two-layer model is effective in capturing the minimal physics of the global mean surface temperature transient response.…”

Section: Time Scale Of the Responsementioning

confidence: 99%

A review of progress towards understanding the transient global mean surface temperature response to radiative perturbation

Yoshimori

Shiogama

Oka

et al. 2016

Prog. in Earth and Planet. Sci.

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The correct understanding of the transient response to external radiative perturbation is important for the interpretation of observed climate change, the prediction of near-future climate change, and committed warming under climate stabilization scenarios, as well as the estimation of equilibrium climate sensitivity based on observation data. It has been known for some time that the radiative damping rate per unit of global mean surface temperature increase varies with time, and this inconstancy affects the transient response. Knowledge of the equilibrium response alone is insufficient, but understanding the transient response of the global mean surface temperature has made rapid progress. The recent progress accompanies the relatively new concept of the efficacies of ocean heat uptake and forcing. The ocean heat uptake efficacy associates the temperature response induced by ocean heat uptake with equilibrium temperature response, and the efficacy of forcing compares the temperature response caused by non-CO 2 forcing with that by CO 2 forcing. In this review article, recent studies on these efficacies are discussed, starting from the classical global feedback framework and basis of the transient response. An attempt is made to structure different studies that emphasize different aspects of the transient response and to stress the relevance of those individual studies. The implications on the definition and computation of forcing and on the estimation of the equilibrium response in climate models are also discussed. Along with these discussions, examples are provided with MIROC climate model multi-millennial simulations.

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“…4c, black), equal to the range of ε displayed in CMIP5 models evaluated by Geoffroy et al (2013). 3.…”

Section: Monte Carlo Input Parameter Distributionsmentioning

confidence: 99%

How historic simulation–observation discrepancy affects future warming projections in a very large model ensemble

Goodwin

2016

Clim Dyn

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Transient Climate Response in a Two-Layer Energy-Balance Model. Part II: Representation of the Efficacy of Deep-Ocean Heat Uptake and Validation for CMIP5 AOGCMs

Cited by 151 publications

References 20 publications

Emulation of long-term changes in global climate: application to the late Pliocene and future

Emulation of long-term changes in global climate: application to the late Pliocene and future

A review of progress towards understanding the transient global mean surface temperature response to radiative perturbation

How historic simulation–observation discrepancy affects future warming projections in a very large model ensemble

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