Global reconstruction of historical ocean heat storage and transport

Zanna, Laure; Khatiwala, S.; Gregory, Jonathan M.; Ison, Jonathan; Heimbach, Patrick

doi:10.1073/pnas.1808838115

Cited by 239 publications

(314 citation statements)

References 50 publications

(75 reference statements)

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“…In addition, comparison of hydrographic observations taken decades apart shows only minor changes in density perturbations (Roemmich and Wunsch, 1984). As the large-scale ocean circulation is in balance with the density structure through geostrophy, these observations suggest that the large-scale circulation did not undergo major reorganizations in the recent past (see also, Zanna et al, 2019). This assumption should be reassessed with additional data that are now available, and the potential effect of changes in circulation is later tested in the section on Penetration of Surface Anomalies.…”

Section: Simulation Of the Common Era Circulation Modelmentioning

confidence: 80%

Atlantic Warming Since the Little Ice Age

Gebbie¹

2019

Oceanog

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Section: Simulation Of the Common Era Circulation Modelmentioning

confidence: 80%

Atlantic Warming Since the Little Ice Age

Gebbie¹

2019

Oceanog

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“…We use the heat uptake observation from Zanna et al (). This estimate agrees with available instrumental records but also extends back in time using Green's functions fit to a data‐assimilation‐constrained ocean circulation.…”

Section: A Constraint From Preindustrial To Present‐day Evolutionmentioning

confidence: 99%

Climate Sensitivity of GFDL's CM4.0

Winton

Adcroft

Dunne

et al. 2020

J Adv Model Earth Syst

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GFDL's new CM4.0 climate model has high transient and equilibrium climate sensitivities near the middle of the upper half of CMIP5 models. The CMIP5 models have been criticized for excessive sensitivity based on observations of present-day warming and heat uptake and estimates of radiative forcing. An ensemble of historical simulations with CM4.0 produces warming and heat uptake that are consistent with these observations under forcing that is at the middle of the assessed distribution. Energy budget-based methods for estimating sensitivities based on these quantities underestimate CM4.0's sensitivities when applied to its historical simulations. However, we argue using a simple attribution procedure that CM4.0's warming evolution indicates excessive transient sensitivity to greenhouse gases. This excessive sensitivity is offset prior to recent decades by excessive response to aerosol and land use changes. Plain Language SummaryWe evaluate the climate sensitivity of the Geophysical Fluid Dynamics Laboratory (GFDL) CM4.0 climate model. Climate sensitivity is an important factor determining the magnitude of future climate change under anthropogenic forcing. We find that CM4.0 is a high climate sensitivity model. A simple method for estimating climate sensitivity from historical changes significantly underestimates CM4.0's sensitivity when applied to CM4.0's historical simulation. However, more sophisticated methods that make use of the detailed evolution of global warming identify CM4.0 as most likely too sensitive to anthropogenic forcing. Key Points: • CM4.0 has high equilibrium and transient climate sensitivities, both near the CMIP5 75th percentile • The energy budget sensitivity estimation method significantly underestimates CM4.0's sensitivities • CM4.0's excessive warming over recent decades most likely indicates excessive transient sensitivity Correspondence to: M. Winton, Michael.Winton@noaa.gov Citation: Winton, M., Adcroft, A., Dunne, J. P., Held, I. M., Shevliakova, E., Zhao, M., et al. (2020). Climate sensitivity of GFDL's CM4.0.

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“…where σ T is defined as for the abrupt-CO2 case as the standard deviation of HadCRUT 1850-1950 values. Shallow andDeep Ocean heat fluxes are taken as the 0-300m and 300m+ heat content derivatives respectively in (Zanna et al, 2019), with σ H and σ D taken as 1850-1950 standard deviations from the same dataset.…”

Section: B11 Model Optimizationmentioning

confidence: 99%

Relating Climate Sensitivity Indices to projection uncertainty

Sanderson¹

2019

Preprint

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Abstract. Can we summarize uncertainties in global response to greenhouse gas forcing with a single number? Here we assess the degree to which traditional metrics are related to future warming indices using an ensemble of simple climate models together with results from CMIP5 and CMIP6. We consider Effective Climate Sensitivity (EffCS), Transient Climate Response at CO2 quadrupling (T140) and a proposed simple metric of temperature change 140 years after a quadrupling of carbon dioxide (A140). In a perfectly equilibrated model, future temperatures under a non-mitigation scenario are almost perfectly described by T140, whereas in a strongly mitigated future, both ECS and T140 are found to be poor predictors of 21st century warming, and future temperatures are better correlated with A140. However, we show that T140 and EffCS calculated in full CMIP simulations are subject to errors arising from control model drift and internal variability. Simulating these factors in the simple model leads to 30 % relative error in the measured value of T140, but only a 10 % error for EffCS. As such, measured values of EffCS can be better correlated with true TCR than measured values of TCR itself. We propose that this could be an explanatory factor in the previously noted surprising result that EffCS is a better predictor than TCR of future transient warming under RCP8.5.

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Global reconstruction of historical ocean heat storage and transport

Cited by 239 publications

References 50 publications

Atlantic Warming Since the Little Ice Age

Atlantic Warming Since the Little Ice Age

Climate Sensitivity of GFDL's CM4.0

Relating Climate Sensitivity Indices to projection uncertainty

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