Sensitivity of an Earth system climate model to idealized radiative forcing

Andrews, Timothy; Ringer, Mark A.; Doutriaux-Boucher, Marie; Webb, Mark J.; Collins, William

doi:10.1029/2012gl051942

Cited by 33 publications

(33 citation statements)

References 18 publications

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“…Total cloud cover increases in all five scenarios with no strong dependency on the forcing agent (not shown), but most CMIP3 and CMIP5 models actually show a decrease in total cloud cover (Bender, 2011;Andrews et al, 2012). Gregory and Webb (2008) as well as Andrews and Forster (2008) showed that fast cloud adjustments caused by an increase in CO 2 forcing are responsible for most of the spread among models.…”

Section: Changes In the Hydrological Cyclementioning

confidence: 94%

The sensitivity of the modeled energy budget and hydrological cycle to CO<sub>2</sub> and solar forcing

et al. 2013

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Abstract. The transient responses of the energy budget and the hydrological cycle to CO2 and solar forcings of the same magnitude in a global climate model are quantified in this study. Idealized simulations are designed to test the assumption that the responses to forcings are linearly additive, i.e. whether the response to individual forcings can be added to estimate the responses to the combined forcing, and to understand the physical processes occurring as a response to a surface warming caused by CO2 or solar forcing increases of the same magnitude. For the global climate model considered, the responses of most variables of the energy budget and hydrological cycle, including surface temperature, do not add linearly. A separation of the response into a forcing and a feedback term shows that for precipitation, this non-linearity arises from the feedback term, i.e. from the non-linearity of the temperature response and the changes in the water cycle resulting from it. Further, changes in the energy budget show that less energy is available at the surface for global annual mean latent heat flux, and hence global annual mean precipitation, in simulations of transient CO2 concentration increase compared to simulations with an equivalent transient increase in the solar constant. On the other hand, lower tropospheric water vapor increase is similar between simulations with CO2 and solar forcing increase of the same magnitude. The response in precipitation is therefore more muted compared to the response in water vapor in CO2 forcing simulations, leading to a larger increase in residence time of water vapor in the atmosphere compared to solar forcing simulations. Finally, energy budget calculations show that poleward atmospheric energy transport increases more in solar forcing compared to equivalent CO2 forcing simulations, which is in line with the identified strong increase in large-scale precipitation in solar forcing scenarios.

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Section: Changes In the Hydrological Cyclementioning

confidence: 94%

The sensitivity of the modeled energy budget and hydrological cycle to CO<sub>2</sub> and solar forcing

et al. 2013

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“…An increasing stomatal closure under high CO 2 affects the balance of latent and sensible heat fluxes from plant canopies and thereby (among other effects) reduces the formation of low-level clouds (Sellers et al 1996;Doutriaux-Boucher et al 2009;de Arellano et al 2012). Moreover, vegetation cover changes and increasing leaf area due to CO 2 fertilization can lead to surface albedo modifications and changes in dust mobilization (Zickfeld et al 2011;Andrews et al 2012). All of these processes change the radiative balance within the atmosphere and establish a radiative forcing that leads to surface warming (DoutriauxBoucher et al 2009).…”

Section: Experiments Description and Analysis Methodsmentioning

confidence: 99%

Nonlinearity of Ocean Carbon Cycle Feedbacks in CMIP5 Earth System Models

et al. 2014

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Carbon cycle feedbacks are usually categorized into carbon–concentration and carbon–climate feedbacks, which arise owing to increasing atmospheric CO2 concentration and changing physical climate. Both feedbacks are often assumed to operate independently: that is, the total feedback can be expressed as the sum of two independent carbon fluxes that are functions of atmospheric CO2 and climate change, respectively. For phase 5 of the Coupled Model Intercomparison Project (CMIP5), radiatively and biogeochemically coupled simulations have been undertaken to better understand carbon cycle feedback processes. Results show that the sum of total ocean carbon uptake in the radiatively and biogeochemically coupled experiments is consistently larger by 19–58 petagrams of carbon (Pg C) than the uptake found in the fully coupled model runs. This nonlinearity is small compared to the total ocean carbon uptake (533–676 Pg C), but it is of the same order as the carbon–climate feedback. The weakening of ocean circulation and mixing with climate change makes the largest contribution to the nonlinear carbon cycle response since carbon transport to depth is suppressed in the fully relative to the biogeochemically coupled simulations, while the radiatively coupled experiment mainly measures the loss of near-surface carbon owing to warming of the ocean. Sea ice retreat and seawater carbon chemistry contribute less to the simulated nonlinearity. The authors’ results indicate that estimates of the ocean carbon–climate feedback derived from “warming only” (radiatively coupled) simulations may underestimate the reduction of ocean carbon uptake in a warm climate high CO2 world.

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“…HadGEM2-ES has the 2nd highest equilibrium climate sensitivity of any of the CMIP5 models at 4.6 °C (Andrews et al 2012b). This value is also substantially higher than HadCM3 for which the value is closer to 3.7 °C (e.g.…”

Section: Implications For the Climate In Response To Increased Comentioning

confidence: 99%

Last glacial maximum constraints on the Earth System model HadGEM2-ES

Hopcroft

Valdes

2014

Clim Dyn

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Sensitivity of an Earth system climate model to idealized radiative forcing

Cited by 33 publications

References 18 publications

The sensitivity of the modeled energy budget and hydrological cycle to CO<sub>2</sub> and solar forcing

The sensitivity of the modeled energy budget and hydrological cycle to CO<sub>2</sub> and solar forcing

Nonlinearity of Ocean Carbon Cycle Feedbacks in CMIP5 Earth System Models

Last glacial maximum constraints on the Earth System model HadGEM2-ES

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Sensitivity of an Earth system climate model to idealized radiative forcing

Cited by 33 publications

References 18 publications

The sensitivity of the modeled energy budget and hydrological cycle to CO&lt;sub&gt;2&lt;/sub&gt; and solar forcing

The sensitivity of the modeled energy budget and hydrological cycle to CO&lt;sub&gt;2&lt;/sub&gt; and solar forcing

Nonlinearity of Ocean Carbon Cycle Feedbacks in CMIP5 Earth System Models

Last glacial maximum constraints on the Earth System model HadGEM2-ES

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Product

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The sensitivity of the modeled energy budget and hydrological cycle to CO<sub>2</sub> and solar forcing

The sensitivity of the modeled energy budget and hydrological cycle to CO<sub>2</sub> and solar forcing