scholarly journals An Assessment of Climate Feedbacks in Coupled Ocean–Atmosphere Models

2006 ◽  
Vol 19 (14) ◽  
pp. 3354-3360 ◽  
Author(s):  
Brian J. Soden ◽  
Isaac M. Held
Keyword(s):  
Water Vapor ◽  
Temperature Response ◽  
Lapse Rate ◽  
Climate Feedbacks ◽  
Regional Patterns ◽  
Surface Warming ◽  
Ocean Atmosphere ◽  
Tightly Coupled ◽  
Vertical Changes ◽  
Water Vapor Mixing Ratio

Abstract The climate feedbacks in coupled ocean–atmosphere models are compared using a coordinated set of twenty-first-century climate change experiments. Water vapor is found to provide the largest positive feedback in all models and its strength is consistent with that expected from constant relative humidity changes in the water vapor mixing ratio. The feedbacks from clouds and surface albedo are also found to be positive in all models, while the only stabilizing (negative) feedback comes from the temperature response. Large intermodel differences in the lapse rate feedback are observed and shown to be associated with differing regional patterns of surface warming. Consistent with previous studies, it is found that the vertical changes in temperature and water vapor are tightly coupled in all models and, importantly, demonstrate that intermodel differences in the sum of lapse rate and water vapor feedbacks are small. In contrast, intermodel differences in cloud feedback are found to provide the largest source of uncertainty in current predictions of climate sensitivity.

scholarly journals Geographical Distribution of Climate Feedbacks in the NCAR CCSM3.0

2011 ◽  
Vol 24 (11) ◽  
pp. 2737-2753 ◽  
Author(s):  
Patrick C. Taylor ◽  
Robert G. Ellingson ◽  
Ming Cai
Keyword(s):  
Water Vapor ◽  
Spatial Variability ◽  
Surface Temperature ◽  
Spatial Patterns ◽  
Temperature Response ◽  
Lapse Rate ◽  
Strongly Correlated ◽  
Climate Feedbacks ◽  
Net Flux ◽  
Radiative Perturbation

Abstract This study performs offline, partial radiative perturbation calculations to determine the geographical distributions of climate feedbacks contributing to the top-of-atmosphere (TOA) radiative energy budget. These radiative perturbations are diagnosed using monthly mean model output from the NCAR Community Climate System Model version 3 (CCSM3.0) forced with the Special Report Emissions Scenario (SRES) A1B emission scenario. The Monte Carlo Independent Column Approximation (MCICA) technique with a maximum–random overlap rule is used to sample monthly mean cloud frequency profiles to perform the radiative transfer calculations. It is shown that the MCICA technique provides a good estimate of all feedback sensitivity parameters. The radiative perturbation results are used to investigate the spatial variability of model feedbacks showing that the shortwave cloud and lapse rate feedbacks exhibit the most and second most spatial variability, respectively. It has been shown that the model surface temperature response is highly correlated with the change in the TOA net flux, and that the latter is largely determined by the total feedback spatial pattern rather than the external forcing. It is shown by representing the change in the TOA net flux as a linear combination of individual feedback radiative perturbations that the lapse rate explains the most spatial variance of the surface temperature response. Feedback spatial patterns are correlated with the model response and other feedback spatial patterns to investigate these relationships. The results indicate that the model convective response is strongly correlated with cloud and water vapor feedbacks, but the lapse rate feedback geographic distribution is strongly correlated with the climatological distribution of convection. The implication for the water vapor–lapse rate anticorrelation is discussed.

scholarly journals A 1D RCE Study of Factors Affecting the Tropical Tropopause Layer and Surface Climate

2019 ◽  
Vol 32 (20) ◽  
pp. 6769-6782 ◽  
Author(s):  
Sally Dacie ◽  
Lukas Kluft ◽  
Hauke Schmidt ◽  
Bjorn Stevens ◽  
Stefan A. Buehler ◽  
...  
Keyword(s):  
Water Vapor ◽  
Climate Models ◽  
Temperature Response ◽  
Global Climate Models ◽  
Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Surface Climate ◽  
Ozone Profile ◽  
Convective Adjustment

Abstract There are discrepancies between global climate models regarding the evolution of the tropical tropopause layer (TTL) and also whether changes in ozone impact the surface under climate change. We use a 1D clear-sky radiative–convective equilibrium model to determine how a variety of factors can affect the TTL and how they influence surface climate. We develop a new method of convective adjustment, which relaxes the temperature profile toward the moist adiabat and allows for cooling above the level of neutral buoyancy. The TTL temperatures in our model are sensitive to CO2 concentration, ozone profile, the method of convective adjustment, and the upwelling velocity, which is used to calculate a dynamical cooling rate in the stratosphere. Moreover, the temperature response of the TTL to changes in each of the above factors sometimes depends on the others. The surface temperature response to changes in ozone and upwelling at and above the TTL is also strongly amplified by both stratospheric and tropospheric water vapor changes. With all these influencing factors, it is not surprising that global models disagree with regard to TTL structure and evolution and the influence of ozone changes on surface temperatures. On the other hand, the effect of doubling CO2 on the surface, including just radiative, water vapor, and lapse-rate feedbacks, is relatively robust to changes in convection, upwelling, or the applied ozone profile.

Consistent Differences in Climate Feedbacks between Atmosphere–Ocean GCMs and Atmospheric GCMs with Slab-Ocean Models*

2013 ◽  
Vol 26 (12) ◽  
pp. 4264-4281 ◽  
Author(s):  
Karen M. Shell
Keyword(s):  
Water Vapor ◽  
General Circulation ◽  
Ocean Dynamics ◽  
Lapse Rate ◽  
Climate Feedbacks ◽  
Temperature Changes ◽  
Model Type ◽  
Global Average ◽  
Ocean Models ◽  
Slab Ocean

Abstract Climate sensitivity is generally studied using two types of models. Atmosphere–ocean general circulation models (AOGCMs) include interactive ocean dynamics and detailed heat uptake. Atmospheric GCMs (AGCMs) with slab ocean models (SOMs) cannot fully simulate the ocean’s response to and influence on climate. However, AGCMs are computationally cheaper and thus are often used to quantify and understand climate feedbacks and sensitivity. Here, physical climate feedbacks are compared between AOGCMs and SOM-AGCMs from the Coupled Model Intercomparison Project phase 3 (CMIP3) using the radiative kernel technique. Both the global-average (positive) water vapor and (negative) lapse-rate feedbacks are consistently stronger in AOGCMs. Water vapor feedback differences result from an essentially constant relative humidity and peak in the tropics, where temperature changes are larger for AOGCMs. Differences in lapse-rate feedbacks extend to midlatitudes and correspond to a larger ratio of tropical- to global-average temperature changes. Global-average surface albedo feedbacks are similar between models types because of a near cancellation of Arctic and Antarctic differences. In AOGCMs, the northern high latitudes warm faster than the southern latitudes, resulting in interhemispheric differences in albedo, water vapor, and lapse-rate feedbacks lacking in the SOM-AGCMs. Meridional heat transport changes also depend on the model type, although there is a large intermodel spread. However, there are no consistent global or zonal differences in cloud feedbacks. Effects of the forcing scenario [Special Report on Emissions Scenarios A1B (SRESa1b) or the 1% CO2 increase per year to doubling (1%to2x) experiments] on feedbacks are model dependent and generally of lesser importance than the model type. Care should be taken when using SOM-AGCMs to understand AOGCM feedback behavior.

scholarly journals Climate Feedbacks in CCSM3 under Changing CO2 Forcing. Part II: Variation of Climate Feedbacks and Sensitivity with Forcing

2013 ◽  
Vol 26 (9) ◽  
pp. 2784-2795 ◽  
Author(s):  
Alexandra K. Jonko ◽  
Karen M. Shell ◽  
Benjamin M. Sanderson ◽  
Gokhan Danabasoglu
Keyword(s):  
Water Vapor ◽  
Temperature Change ◽  
Climate Sensitivity ◽  
General Circulation ◽  
Coupled Model ◽  
Lapse Rate ◽  
Climate Feedbacks ◽  
Cloud Feedbacks ◽  
Response To Temperature ◽  
Fully Coupled

Abstract Are equilibrium climate sensitivity and the associated radiative feedbacks a constant property of the climate system, or do they change with forcing magnitude and base climate? Using the radiative kernel technique, feedbacks and climate sensitivity are evaluated in a fully coupled general circulation model (GCM) for three successive doublings of carbon dioxide starting from present-day concentrations. Climate sensitivity increases by 23% between the first and third CO2 doublings. Increases in the positive water vapor and cloud feedbacks are partially balanced by a decrease in the positive surface albedo feedback and an increase in the negative lapse rate feedback. Feedbacks can be decomposed into a radiative flux change and a climate variable response to temperature change. The changes in water vapor and Planck feedbacks are due largely to changes in the radiative response with climate state. Higher concentrations of greenhouse gases and higher temperatures lead to more absorption and emission of longwave radiation. Changes in cloud feedbacks are dominated by the climate response to temperature change, while the lapse rate and albedo feedbacks combine elements of both. Simulations with a slab ocean model (SOM) version of the GCM are used to verify whether an SOM-GCM accurately reproduces the behavior of the fully coupled model. Although feedbacks differ in magnitude between model configurations (with differences as large as those between CO2 doublings for some feedbacks), changes in feedbacks between CO2 doublings are consistent in sign and magnitude in the SOM-GCM and the fully coupled model.

scholarly journals Seasonal Variations of Climate Feedbacks in the NCAR CCSM3

2011 ◽  
Vol 24 (13) ◽  
pp. 3433-3444 ◽  
Author(s):  
Patrick C. Taylor ◽  
Robert G. Ellingson ◽  
Ming Cai
Keyword(s):  
Surface Temperature ◽  
Surface Albedo ◽  
Global Climate ◽  
Temperature Response ◽  
Lapse Rate ◽  
Climate Feedback ◽  
Climate Simulation ◽  
Climate Feedbacks ◽  
Climate System Model ◽  
Global Mean

Abstract This study investigates the annual cycle of radiative contributions to global climate feedbacks. A partial radiative perturbation (PRP) technique is used to diagnose monthly radiative perturbations at the top of atmosphere (TOA) due to CO2 forcing; surface temperature response; and water vapor, cloud, lapse rate, and surface albedo feedbacks using NCAR Community Climate System Model, version 3 (CCSM3) output from a Special Report on Emissions Scenarios (SRES) A1B emissions-scenario-forced climate simulation. The seasonal global mean longwave TOA radiative feedback was found to be minimal. However, the global mean shortwave (SW) TOA cloud and surface albedo radiative perturbations exhibit large seasonality. The largest contributions to the negative SW cloud feedback occur during summer in each hemisphere, marking the largest differences with previous results. Results suggest that intermodel spread in climate sensitivity may occur, partially from cloud and surface albedo feedback seasonality differences. Further, links between the climate feedback and surface temperature response seasonality are investigated, showing a strong relationship between the seasonal climate feedback distribution and the seasonal surface temperature response.

Surface warming patterns dominate the uncertainty in global water vapor plus lapse rate feedback

2020 ◽  
Vol 39 (3) ◽  
pp. 81-89 ◽  
Author(s):  
Jingchun Zhang ◽  
Jian Ma ◽  
Jing Che ◽  
Zhenqiang Zhou ◽  
Guoping Gao
Keyword(s):  
Water Vapor ◽  
Lapse Rate ◽  
Surface Warming ◽  
Rate Feedback ◽  
Global Water

scholarly journals The Vertical Structure of Tropospheric Water Vapor: Comparing Radiative and Ocean-Driven Climate Changes

2016 ◽  
Vol 29 (11) ◽  
pp. 4251-4268 ◽  
Author(s):  
Brian E. J. Rose ◽  
M. Cameron Rencurrel
Keyword(s):  
Water Vapor ◽  
Surface Temperature ◽  
Diagnostic Technique ◽  
Lapse Rate ◽  
Ocean Heat Uptake ◽  
Surface Warming ◽  
Wide Range ◽  
Single Column ◽  
Transient Climate Change ◽  
Lapse Rates

Abstract Changes in column-integrated water vapor (Q) in response to increased CO2 and ocean heat uptake (OHU) are investigated in slab-ocean aquaplanet simulations. The simulations span a wide range of warming and moistening patterns due to the spatial structures of the imposed OHU. Fractional changes in Q per degree of surface warming range from 0% to 20% K−1 locally and from 3.6% to 11% K−1 globally. A new diagnostic technique decomposes these changes into relative humidity (RH), surface temperature, and lapse rate contributions. Single-column calculations demonstrate substantial departures from apparent (surface temperature based) Clausius–Clapeyron (CC) scaling due to lapse rates changes; a moist-adiabatic column with fixed, uniform RH exceeds the CC rate by 2.5% K−1. The RH contribution is very small in most simulations. The various Q scalings are thus all consistent CC, but result from different patterns of polar amplification and lapse rate change. Lapse rates are sensitive to location and magnitude of OHU, with implications for Q under transient climate change. CO2 with subpolar (tropical) OHU results in higher (lower) Q scalings than CO2 alone. The weakest Q scaling (and largest RH effects) is found for increased poleward ocean heat transport, which causes strongly polar-amplified warming and near-zero tropical temperature change. Despite weak RH changes and fidelity to the CC relation, Q is expected to vary widely on different time scales in nature due to sensitivity of lapse rates to OHU along with the nonlinearity of the diagnostics.

scholarly journals An Assessment of Direct Radiative Forcing, Radiative Adjustments, and Radiative Feedbacks in Coupled Ocean–Atmosphere Models*

2015 ◽  
Vol 28 (10) ◽  
pp. 4152-4170 ◽  
Author(s):  
Eui-Seok Chung ◽  
Brian J. Soden
Keyword(s):  
Surface Temperature ◽  
Radiative Forcing ◽  
Climate Models ◽  
Substantial Part ◽  
Regional Patterns ◽  
Surface Warming ◽  
Ocean Atmosphere ◽  
Direct Radiative Forcing ◽  
Radiative Feedbacks ◽  
Global Mean

Abstract In this study, radiative kernels are used to separate direct radiative forcing from radiative adjustments to that forcing to quantify the magnitude and intermodel spread of tropospheric and stratospheric adjustments in coupled ocean–atmosphere climate models. Radiative feedbacks are also quantified and separated from radiative forcing by assuming that feedbacks are a linear response to changes in global-mean surface temperature. The direct radiative forcing due to a quadrupling of CO2 is found to have an intermodel spread of ~3 W m−2. In contrast to previous studies, relatively small estimates of cloud adjustments are obtained, which are both positive and negative. This discrepancy is at least partially attributable to small, but nonnegligible, global-mean surface warming in fixed sea surface temperature experiments, which aliases a surface-driven feedback response into estimates of the adjustments. This study suggests that correcting for the bias induced from this global-mean surface warming offers a more accurate estimate of tropospheric adjustments. It is shown that the regional patterns in the tropospheric adjustments tend to oppose the radiative feedback. This compensation is closely tied to spatial inhomogeneities in the initial rate of surface warming, suggesting that a substantial part of the spatial variation in the estimated tropospheric adjustment is an artifact of the linear regression methodology. Even when assuming that the global-mean estimates of the tropospheric adjustments are valid, neglecting them introduces little uncertainty in estimates of the total forcing, feedback, or effective climate sensitivity relative to the intermodel spread in these values.

Climate Feedbacks in Response to Changes in Obliquity

2011 ◽  
Vol 24 (11) ◽  
pp. 2830-2845 ◽  
Author(s):  
Damianos F. Mantsis ◽  
Amy C. Clement ◽  
Anthony J. Broccoli ◽  
Michael P. Erb
Keyword(s):  
Water Vapor ◽  
Ocean Circulation ◽  
Climate Model ◽  
Lapse Rate ◽  
High Latitudes ◽  
Climate Feedbacks ◽  
Radiative Fluxes ◽  
Global Mean Temperature ◽  
Low Latitudes ◽  
Global Mean

Abstract The feedbacks involved in the response of climate to a reduction of Earth’s obliquity are investigated in the GFDL Climate Model version 2.1 (CM2.1). A reduction in obliquity increases the meridional gradient of the annual mean insolation, causing a strengthening of the atmospheric and ocean circulation that transports more heat poleward. The heat transport does not balance the direct obliquity forcing completely, and additional local radiative fluxes are required to explain the change in the equilibrium energy budget. The surface temperature generally increases at low latitudes and decreases at high latitudes following the change in the insolation. However, in some areas, the sign of the temperature change is opposite of the forcing, indicating the strong influence of feedbacks. These feedbacks are also responsible for a decrease in the global mean temperature despite that the change in the global mean insolation is close to zero. The processes responsible for these changes are increases in the ice fraction at high latitudes and the global cloud fraction—both of which reduce the absorbed solar radiation. A reduction in the global greenhouse trapping, due to changes in the distribution of the water vapor content of the atmosphere as well as a change in the lapse rate, has an additional cooling effect. Among these feedbacks, clouds and the lapse rate have the larger contribution, with water vapor and surface albedo having a smaller effect. The implications of the findings presented here for interpretation of obliquity cycles in the paleoclimate record are discussed.

Sources of Intermodel Spread in the Lapse Rate and Water Vapor Feedbacks

2018 ◽  
Vol 31 (8) ◽  
pp. 3187-3206 ◽  
Author(s):  
Stephen Po-Chedley ◽  
Kyle C. Armour ◽  
Cecilia M. Bitz ◽  
Mark D. Zelinka ◽  
Benjamin D. Santer ◽  
...  
Keyword(s):  
Water Vapor ◽  
Sea Ice ◽  
General Circulation ◽  
Large Scale ◽  
General Circulation Models ◽  
Lapse Rate ◽  
Cross Model ◽  
Surface Warming ◽  
Antarctic Sea Ice ◽  
The Tropics

Abstract Sources of intermodel differences in the global lapse rate (LR) and water vapor (WV) feedbacks are assessed using CO2 forcing simulations from 28 general circulation models. Tropical surface warming leads to significant warming and moistening in the tropical and extratropical upper troposphere, signifying a nonlocal, tropical influence on extratropical radiation and feedbacks. Model spread in the locally defined LR and WV feedbacks is pronounced in the Southern Ocean because of large-scale ocean upwelling, which reduces surface warming and decouples the surface from the tropospheric response. The magnitude of local extratropical feedbacks across models and over time is well characterized using the ratio of tropical to extratropical surface warming. It is shown that model differences in locally defined LR and WV feedbacks, particularly over the southern extratropics, drive model variability in the global feedbacks. The cross-model correlation between the global LR and WV feedbacks therefore does not arise from their covariation in the tropics, but rather from the pattern of warming exerting a common control on extratropical feedback responses. Because local feedbacks over the Southern Hemisphere are an important contributor to the global feedback, the partitioning of surface warming between the tropics and the southern extratropics is a key determinant of the spread in the global LR and WV feedbacks. It is also shown that model Antarctic sea ice climatology influences sea ice area changes and southern extratropical surface warming. As a result, model discrepancies in climatological Antarctic sea ice area have a significant impact on the intermodel spread of the global LR and WV feedbacks.

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