The varying climate feedback parameter connected to the atmosphere-ocean coupling and ocean circulation

2021 ◽  
Author(s):  
Diego Jiménez de la Cuesta
Keyword(s):  
Ocean Circulation ◽  
Climate Feedback ◽  
Feedback Parameter ◽  
Ocean Coupling

scholarly journals The inconstancy of the transient climate response parameter under increasing CO 2

2015 ◽  
Vol 373 (2054) ◽  
pp. 20140417 ◽  
Author(s):  
J. M. Gregory ◽  
T. Andrews ◽  
P. Good
Keyword(s):  
Radiative Forcing ◽  
Coupled Model ◽  
Surface Air Temperature ◽  
Deep Ocean ◽  
Climate Feedback ◽  
Climate Response ◽  
Ocean Heat Uptake ◽  
Transient Climate Response ◽  
Feedback Parameter ◽  
Response Parameter

In the Coupled Model Intercomparison Project Phase 5 (CMIP5), the model-mean increase in global mean surface air temperature T under the 1pctCO2 scenario (atmospheric CO 2 increasing at 1% yr −1 ) during the second doubling of CO 2 is 40% larger than the transient climate response (TCR), i.e. the increase in T during the first doubling. We identify four possible contributory effects. First, the surface climate system loses heat less readily into the ocean beneath as the latter warms. The model spread in the thermal coupling between the upper and deep ocean largely explains the model spread in ocean heat uptake efficiency. Second, CO 2 radiative forcing may rise more rapidly than logarithmically with CO 2 concentration. Third, the climate feedback parameter may decline as the CO 2 concentration rises. With CMIP5 data, we cannot distinguish the second and third possibilities. Fourth, the climate feedback parameter declines as time passes or T rises; in 1pctCO2, this effect is less important than the others. We find that T projected for the end of the twenty-first century correlates more highly with T at the time of quadrupled CO 2 in 1pctCO2 than with the TCR, and we suggest that the TCR may be underestimated from observed climate change.

The Carbon Cycle

2019 ◽  
pp. 129-158
Author(s):  
Han Dolman
Keyword(s):  
Carbon Cycle ◽  
Primary Production ◽  
Ocean Circulation ◽  
Net Primary Production ◽  
Gross Primary Production ◽  
Carbon Stocks ◽  
Climate Feedback ◽  
Fossil Fuel Burning ◽  
Thermal Maximum ◽  
Natural Carbon

The chapter first shows carbon dioxide variability over long geological timescales. The current stocks and fluxes of carbon are then given, for the whole planet and for the atmosphere, ocean and land separately. The main flows of carbon in the ocean, through the biological pump (via uptake through photosynthesis) and the physical pump (via involving chemical transformation uptake in water and production of carbonate), and on land, through photosynthesis (Gross Primary Production) and respiration leading to Net Primary Production, Net Ecosystem Production and Net Biome Production and through the storage of carbon in biomass, are described. Next, carbon interactions during the Paleocene–Eocene Thermal Maximum and glacial–interglacial transitions, thought to involve changes in ocean circulation and upwelling, are examined. The key changes from anthropogenic perturbation of the natural carbon cycle are shown to be due to fossil fuel burning and land-use change (deforestation). The effects of the carbon–climate feedback on temperature and carbon stocks are also shown.

scholarly journals On the Accuracy of Deriving Climate Feedback Parameters from Correlations between Surface Temperature and Outgoing Radiation

2010 ◽  
Vol 23 (18) ◽  
pp. 4983-4988 ◽  
Author(s):  
D. M. Murphy ◽  
P. M. Forster
Keyword(s):  
Surface Temperature ◽  
Climate Model ◽  
Mixed Layer Depth ◽  
Box Model ◽  
Climate Feedback ◽  
Time Interval ◽  
Feedback Parameter ◽  
Outgoing Radiation ◽  
The Difference ◽  
Climate Studies

Abstract Changes in outgoing radiation are both a consequence and a cause of changes in the earth’s temperature. Spencer and Braswell recently showed that in a simple box model for the earth the regression of outgoing radiation against surface temperature gave a slope that differed from the model’s true feedback parameter. They went on to select input parameters for the box model based on observations, computed the difference for those conditions, and asserted that there is a significant bias for climate studies. This paper shows that Spencer and Braswell overestimated the difference. Differences between the regression slope and the true feedback parameter are significantly reduced when 1) a more realistic value for the ocean mixed layer depth is used, 2) a corrected standard deviation of outgoing radiation is used, and 3) the model temperature variability is computed over the same time interval as the observations. When all three changes are made, the difference between the slope and feedback parameter is less than one-tenth of that estimated by Spencer and Braswell. Absolute values of the difference for realistic cases are less than 0.05 W m−2 K−1, which is not significant for climate studies that employ regressions of outgoing radiation against temperature. Previously published results show that the difference is negligible in the Hadley Centre Slab Climate Model, version 3 (HadSM3).

Connections between climate sensitivity and the extratropical circulation

2020 ◽  
Author(s):  
Luke Davis ◽  
David Thompson ◽  
Thomas Birner
Keyword(s):  
Climate Change ◽  
Climate Sensitivity ◽  
General Circulation ◽  
Damping Coefficient ◽  
Climate Feedback ◽  
Dynamical Response ◽  
Feedback Parameter ◽  
Dynamical Core ◽  
Linear Damping ◽  
Extratropical Circulation

<div>The dry dynamical core represents one of the simplest possible numerical models for studying the response of the extratropical circulation to climate change. In the model, the circulation is forced by relaxing temperature to a notional “equilibrium” using linear damping. The linear damping coefficient plays an essential role in governing the structure of the circulation. But despite decades of research with the dry dynamical core, the role of the damping coefficient in governing the circulation has received relatively little scrutiny.</div><div><br>In this work, we systematically vary the damping coefficient in a dry dynamical core in order to understand how the amplitude of the damping influences extratropical dynamics. Critically, we prove that the local climate feedback parameter is proportional to the damping coefficient – that is, the damping timescale is a measure of climate sensitivity for the dry atmosphere. The key finding is that the steady-state extratropical circulation responds to changes in this climate sensitivity.</div><div><br>Longer damping timescales (i.e. higher climate sensitivities) lead to a less dynamically active extratropical circulation, stronger and more persistent annular modes, and equatorward shifts in the jet. When perturbed with climate change-like forcings, changing the damping timescale can also change the dynamical response to the forcing. We argue that understanding the response of the circulation to climate change is critically dependent on understanding its climate sensitivity, and consider how climate sensitivity might be inferred from its effect on the circulation in the dry model and more complex general circulation models.</div>

scholarly journals The Dependence of Radiative Forcing and Feedback on Evolving Patterns of Surface Temperature Change in Climate Models

2015 ◽  
Vol 28 (4) ◽  
pp. 1630-1648 ◽  
Author(s):  
Timothy Andrews ◽  
Jonathan M. Gregory ◽  
Mark J. Webb
Keyword(s):  
Surface Temperature ◽  
Temperature Change ◽  
Radiative Forcing ◽  
General Circulation ◽  
Climate Feedback ◽  
Climate Feedbacks ◽  
Surface Temperature Change ◽  
Feedback Parameter ◽  
Surface Warming ◽  
Global Mean

Abstract Experiments with CO2 instantaneously quadrupled and then held constant are used to show that the relationship between the global-mean net heat input to the climate system and the global-mean surface air temperature change is nonlinear in phase 5 of the Coupled Model Intercomparison Project (CMIP5) atmosphere–ocean general circulation models (AOGCMs). The nonlinearity is shown to arise from a change in strength of climate feedbacks driven by an evolving pattern of surface warming. In 23 out of the 27 AOGCMs examined, the climate feedback parameter becomes significantly (95% confidence) less negative (i.e., the effective climate sensitivity increases) as time passes. Cloud feedback parameters show the largest changes. In the AOGCM mean, approximately 60% of the change in feedback parameter comes from the tropics (30°N–30°S). An important region involved is the tropical Pacific, where the surface warming intensifies in the east after a few decades. The dependence of climate feedbacks on an evolving pattern of surface warming is confirmed using the HadGEM2 and HadCM3 atmosphere GCMs (AGCMs). With monthly evolving sea surface temperatures and sea ice prescribed from its AOGCM counterpart, each AGCM reproduces the time-varying feedbacks, but when a fixed pattern of warming is prescribed the radiative response is linear with global temperature change or nearly so. It is also demonstrated that the regression and fixed-SST methods for evaluating effective radiative forcing are in principle different, because rapid SST adjustment when CO2 is changed can produce a pattern of surface temperature change with zero global mean but nonzero change in net radiation at the top of the atmosphere (~−0.5 W m−2 in HadCM3).

scholarly journals A small climate-amplifying effect of climate-carbon cycle feedback

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xuanze Zhang ◽  
Ying-Ping Wang ◽  
Peter J. Rayner ◽  
Philippe Ciais ◽  
Kun Huang ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Global Climate ◽  
Gain Factor ◽  
Climate Feedback ◽  
Historical Period ◽  
Earth System ◽  
Feedback Parameter ◽  
Feedback Analysis ◽  
Decadal Scale ◽  
Amplifying Effect

AbstractThe climate-carbon cycle feedback is one of the most important climate-amplifying feedbacks of the Earth system, and is quantified as a function of carbon-concentration feedback parameter (β) and carbon-climate feedback parameter (γ). However, the global climate-amplifying effect from this feedback loop (determined by the gain factor, g) has not been quantified from observations. Here we apply a Fourier analysis-based carbon cycle feedback framework to the reconstructed records from 1850 to 2017 and 1000 to 1850 to estimate β and γ. We show that the β-feedback varies by less than 10% with an average of 3.22 ± 0.32 GtC ppm−1 for 1880–2017, whereas the γ-feedback increases from −33 ± 14 GtC K−1 on a decadal scale to −122 ± 60 GtC K−1 on a centennial scale for 1000–1850. Feedback analysis further reveals that the current amplification effect from the carbon cycle feedback is small (g is 0.01 ± 0.05), which is much lower than the estimates by the advanced Earth system models (g is 0.09 ± 0.04 for the historical period and is 0.15 ± 0.08 for the RCP8.5 scenario), implying that the future allowable CO2 emissions could be 9 ± 7% more. Therefore, our findings provide new insights about the strength of climate-carbon cycle feedback and about observational constraints on models for projecting future climate.

scholarly journals Estimation of the climate feedback parameter by using radiative fluxes from CERES EBAF

2013 ◽  
Vol 4 (1) ◽  
pp. 25-47
Author(s):  
P. Björnbom
Keyword(s):  
Radiative Forcing ◽  
Phase Plane ◽  
Southern Oscillation ◽  
Radiant Energy ◽  
Radiative Flux ◽  
Climate Feedback ◽  
Time Interval ◽  
Feedback Parameter ◽  
Temperature Anomalies ◽  
Straight Lines

Abstract. Top-of-the-Atmosphere (TOA) net radiative flux anomalies from Clouds and Earth's Radiant Energy Systems (CERES) Energy Balanced and Filled (EBAF) and surface air temperature anomalies from HadCRUT3 were compared for the time interval September 2000–May 2011. In a phase plane plot with the radiative flux anomalies lagging the temperature anomalies with 7 months the phase plane curve approached straight lines during about an eight months long period at the beginning and a five year period at the end of the interval. Both of those periods, but more clearly the latter one, could be connected to the occurrence of distinct El Niño Southern Oscillation (ENSO) episodes. This result is explained by using a hypothesis stating that non-radiative forcing connected to the ENSO is dominating the temperature changes during those two periods and that there is a lag between the temperature change and the radiative flux feedback. According to the hypothesis the slopes of the straight lines equal the value of the climate feedback parameter. By linear regression based on the mentioned five year period the value of the climate feedback parameter was estimated to 5.5 ± 0.6 W m−2 K−1 (± two standard errors).

Revisiting the variation of the climate feedback parameter

2021 ◽  
Author(s):  
Diego Jiménez-de-la-Cuesta
Keyword(s):  
Energy Balance ◽  
Explicit Expression ◽  
Climate Feedback ◽  
Additional Contribution ◽  
Earth System ◽  
Surface Temperature Change ◽  
Feedback Parameter ◽  
The Earth ◽  
Ocean Atmosphere ◽  
Spatio Temporal

<p>Observations and models indicate a varying radiative response of the Earth system to CO<sub>2</sub> forcing. This variation introduces large uncertainties in the climate sensitivity estimates to increasing atmospheric CO<sub>2</sub> concentration. This variation is represented as an additional feedback mechanism in energy-balance models, which depends on more than only the surface temperature change. Models and observations also indicate that a spatio-temporal pattern in the surface warming controls this additional contribution to the radiative response. However, several authors picture this effect as a feedback change in the atmosphere, reducing the role of the ocean's enthalpy-uptake variations. I use a widely-known linearised conceptual energy-balance model and its analytical solutions to find an explicit expression of the radiative response and its temporal evolution. This explicit expression provides another timescale in the Earth system, as the ocean-atmosphere coupling modulates the radiative response. Thus, to understand the variation of the climate feedback parameter, we need not only to know its relation to the spatio-temporal warming pattern but an improved picture of the ocean-atmosphere coupling that generates the pattern.</p>

scholarly journals Carbon-Cycle Feedbacks Operating in the Climate System

2019 ◽  
Vol 5 (4) ◽  
pp. 282-295 ◽  
Author(s):  
Richard G. Williams ◽  
Anna Katavouta ◽  
Philip Goodwin
Keyword(s):  
Carbon Cycle ◽  
Surface Temperature ◽  
Climate System ◽  
Climate Forcing ◽  
Climate Feedback ◽  
Direct Response ◽  
Feedback Parameter ◽  
Ocean Carbon ◽  
Carbon Stores ◽  
Climate Responses

AbstractClimate change involves a direct response of the climate system to forcing which is amplified or damped by feedbacks operating in the climate system. Carbon-cycle feedbacks alter the land and ocean carbon inventories and so act to reduce or enhance the increase in atmospheric CO2 from carbon emissions. The prevailing framework for carbon-cycle feedbacks connect changes in land and ocean carbon inventories with a linear sum of dependencies on atmospheric CO2 and surface temperature. Carbon-cycle responses and feedbacks provide competing contributions: the dominant effect is that increasing atmospheric CO2 acts to enhance the land and ocean carbon stores, so providing a negative response and feedback to the original increase in atmospheric CO2, while rising surface temperature acts to reduce the land and ocean carbon stores, so providing a weaker positive feedback for atmospheric CO2. The carbon response and feedback of the land and ocean system may be expressed in terms of a combined carbon response and feedback parameter, λcarbon in units of W m− 2K− 1, and is linearly related to the physical climate feedback parameter, λclimate, revealing how carbon and climate responses and feedbacks are inter-connected. The magnitude and uncertainties in the carbon-cycle response and feedback parameter are comparable with the magnitude and uncertainties in the climate feedback parameter from clouds. Further mechanistic insight needs to be gained into how the carbon-cycle feedbacks are controlled for the land and ocean, particularly to separate often competing effects from changes in atmospheric CO2 and climate forcing.

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