Effective radiative forcing in a GCM with fixed surface temperatures

Andrews, Timothy; Smith, Christopher J.; Myhre, Gunnar; Forster, Piers M.; Chadwick, Robin

doi:10.1002/essoar.10504260.1

Cited by 7 publications

(8 citation statements)

References 40 publications

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“…By contrast, Richardson et al. (2019) found no significant differences in feedback between the two kinds of aerosols (SO 4 and BC) and GHGs, regardless of whether they calculated ERF as in the present paper, or additionally correcting for the impact of land surface temperature adjustments (Andrews et al., 2021). There are several possible explanations for our disagreement, including the following.…”

Section: Investigating Radiative Feedback Differences In Terms Of Sta...contrasting

confidence: 55%

Interpreting Differences in Radiative Feedbacks From Aerosols Versus Greenhouse Gases

Salvi

Ceppi

Gregory

2022

Geophysical Research Letters

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Experiments with seven Coupled Model Intercomparison Project phase 6 models were used to assess the climate feedback parameter for net historical, historical greenhouse gas (GHG) and anthropogenic aerosol forcings. The net radiative feedback is found to be more amplifying (higher effective climate sensitivity) for aerosol than GHG forcing, and hence also less amplifying for net historical (GHG + aerosol) than GHG only. We demonstrate that this difference is consistent with their different latitudinal distributions. Historical aerosol forcing is most pronounced in northern extratropics, where the boundary layer is decoupled from the free troposphere, so the consequent temperature change is confined to low altitude and causes low‐level cloud changes. This is caused by change in stability, which also affects upper‐tropospheric clear‐sky emission, affecting both shortwave and longwave radiative feedbacks. This response is a feature of extratropical forcing generally, regardless of its sign or hemisphere.

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Section: Investigating Radiative Feedback Differences In Terms Of Sta...contrasting

confidence: 55%

Interpreting Differences in Radiative Feedbacks From Aerosols Versus Greenhouse Gases

Salvi

Ceppi

Gregory

2022

Geophysical Research Letters

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“…Compared with the Gregory method, the Hansen method is more computationally efficient and less sensitive to the selected simulation years (Forster et al., 2016). However, the land surface temperature in fixed‐SST experiments is allowed to change and it could contribute to the change of global‐mean surface temperature (Andrews et al., 2021). Whereas their definitions are different, comparing these two types of ERFs across models can help understand the model diversity of ERF and the correspondence between atmosphere‐only and coupled ERF among CMIP models.…”

Section: Resultsmentioning

confidence: 99%

On the Correspondence Between Atmosphere‐Only and Coupled Simulations for Radiative Feedbacks and Forcing From CO₂

2022

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Radiative feedback and forcing are generally calculated from fully coupled simulations of global climate models (GCMs) forced by abruptly quadrupled CO 2 concentration run for 150 yr or longer. However, conducting sensitivity experiments to better understand the physical mechanisms driving feedbacks is generally not feasible with fully coupled simulations, which are computationally expensive. Hence, simplified atmosphere-only experiments, including Atmospheric Model Intercomparison Project (AMIP) and aquaplanet experiments with globally uniform increases in sea surface temperature (SST), are more commonly used to understand inter-model differences in radiative feedbacks and forcing (

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“…A limitation to our ERF calculation approach is that we only fix the SSTs and SICs in the simulation, but not the land temperatures. Fixing the land temperatures has been shown to increase ERF in warmer climates even more than when only SSTs and SICs are fixed (Andrews et al., 2021). To account for this, we removed the land and sea‐ice warming effects in our ERF calculations, following Equation 1 in Hansen et al.…”

Section: Resultsmentioning

confidence: 99%

Asymmetric Warming/Cooling Response to CO₂ Increase/Decrease Mainly Due To Non‐Logarithmic Forcing, Not Feedbacks

Mitevski

Polvani

Orbe

2022

Geophysical Research Letters

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Equilibrium climate sensitivity (ECS) is the global mean surface temperature change after the doubling of CO 2 concentrations from pre-industrial (PI) levels. ECS is perhaps the most important metric in climate science, and it has been extensively investigated in the literature (Sherwood et al., 2020). An important question is whether the amount of warming for each CO 2 doubling (which we refer to as the effective climate sensitivity, S G ) is constant or not (i.e., whether it is CO 2 dependent). Necessary conditions for a constant S G are (a) that the radiative forcing of the climate system for each CO 2 doubling is constant and (b) that the net radiative feedback does not change with CO 2 levels. This question has been investigated in many modeling studies (Bloch-Johnson et al., 2021;Meraner et al., 2013;Mauritsen et al., 2019;Sherwood et al., 2020), which have reported that S G is indeed CO 2 dependent. Most of these studies find that S G increases at higher CO 2 levels and that the change in feedbacks, not the change in CO 2 radiative forcing, is the primary driver of S G CO 2 dependence.An alternative approach to using climate models to investigate the dependency of S G on CO 2 is to seek observational constraints from reconstructions of past climates. In particular, most studies conclude that S G inferred from paleoclimate records does depend on CO 2 (

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Effective radiative forcing in a GCM with fixed surface temperatures

Cited by 7 publications

References 40 publications

Interpreting Differences in Radiative Feedbacks From Aerosols Versus Greenhouse Gases

Interpreting Differences in Radiative Feedbacks From Aerosols Versus Greenhouse Gases

On the Correspondence Between Atmosphere‐Only and Coupled Simulations for Radiative Feedbacks and Forcing From CO₂

Asymmetric Warming/Cooling Response to CO₂ Increase/Decrease Mainly Due To Non‐Logarithmic Forcing, Not Feedbacks

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Effective radiative forcing in a GCM with fixed surface temperatures

Cited by 7 publications

References 40 publications

Interpreting Differences in Radiative Feedbacks From Aerosols Versus Greenhouse Gases

Interpreting Differences in Radiative Feedbacks From Aerosols Versus Greenhouse Gases

On the Correspondence Between Atmosphere‐Only and Coupled Simulations for Radiative Feedbacks and Forcing From CO2

Asymmetric Warming/Cooling Response to CO2 Increase/Decrease Mainly Due To Non‐Logarithmic Forcing, Not Feedbacks

Contact Info

Product

Resources

About

On the Correspondence Between Atmosphere‐Only and Coupled Simulations for Radiative Feedbacks and Forcing From CO₂

Asymmetric Warming/Cooling Response to CO₂ Increase/Decrease Mainly Due To Non‐Logarithmic Forcing, Not Feedbacks