scholarly journals Correspondence: Variations in ocean heat uptake during the surface warming hiatus

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Xianyao Chen ◽  
Ka-Kit Tung
Keyword(s):  
Ocean Heat Uptake ◽  
Surface Warming ◽  
Heat Uptake ◽  
Warming Hiatus

scholarly journals Sensitivity of Global Warming to Carbon Emissions: Effects of Heat and Carbon Uptake in a Suite of Earth System Models

2017 ◽  
Vol 30 (23) ◽  
pp. 9343-9363 ◽  
Author(s):  
Richard G. Williams ◽  
Vassil Roussenov ◽  
Philip Goodwin ◽  
Laure Resplandy ◽  
Laurent Bopp
Keyword(s):  
Climate Sensitivity ◽  
Carbon Emissions ◽  
Radiative Forcing ◽  
Carbon Uptake ◽  
Earth System ◽  
Ocean Heat Uptake ◽  
Surface Warming ◽  
System Models ◽  
Heat Uptake ◽  
Earth System Models

Climate projections reveal global-mean surface warming increasing nearly linearly with cumulative carbon emissions. The sensitivity of surface warming to carbon emissions is interpreted in terms of a product of three terms: the dependence of surface warming on radiative forcing, the fractional radiative forcing from CO2, and the dependence of radiative forcing from CO2 on carbon emissions. Mechanistically each term varies, respectively, with climate sensitivity and ocean heat uptake, radiative forcing contributions, and ocean and terrestrial carbon uptake. The sensitivity of surface warming to fossil-fuel carbon emissions is examined using an ensemble of Earth system models, forced either by an annual increase in atmospheric CO2 or by RCPs until year 2100. The sensitivity of surface warming to carbon emissions is controlled by a temporal decrease in the dependence of radiative forcing from CO2 on carbon emissions, which is partly offset by a temporal increase in the dependence of surface warming on radiative forcing. The decrease in the dependence of radiative forcing from CO2 is due to a decline in the ratio of the global ocean carbon undersaturation to carbon emissions, while the increase in the dependence of surface warming is due to a decline in the ratio of ocean heat uptake to radiative forcing. At the present time, there are large intermodel differences in the sensitivity in surface warming to carbon emissions, which are mainly due to uncertainties in the climate sensitivity and ocean heat uptake. These uncertainties undermine the ability to predict how much carbon may be emitted before reaching a warming target.

Quantifying uncertainty in decadal ocean heat uptake due to intrinsic ocean variability

2020 ◽  
Author(s):  
Bablu Sinha ◽  
Alex Megann ◽  
Thierry Penduff ◽  
Jean-Marc Molines ◽  
Sybren Drijfhout
Keyword(s):  
North Pacific ◽  
Western Boundary ◽  
High Latitudes ◽  
Intrinsic Variability ◽  
Ocean Heat Uptake ◽  
Decadal Timescale ◽  
Surface Warming ◽  
Ocean Variability ◽  
Heat Uptake ◽  
Global Surface

<p>Remarkably, global surface warming since 1850 has not proceeded monotonically, but has consisted of a series of decadal timescale slowdowns (hiatus periods) followed by surges. Knowledge of a mechanism to explain these fluctuations would greatly aid development and testing of near term climate forecasts. Here we evaluate the influence of ocean intrinsic variability on global ocean heat uptake and hence the rate of global surface warming, using a 50-member ensemble of eddy-permitting ocean general circulation model simulations (OCCIPUT ensemble) forced with identical surface atmospheric condition for the period 1960-2015. Air-sea heat flux, integrated zonally and accumulated with latitude provides a useful measure of ocean heat uptake. We plot the ensemble mean difference of this quantity between 2000-2009 (hiatus) and 1990-1999 (surge). OCCIPUT suggests that the 2000s saw increased ocean heat uptake of ~0.32 W m<sup>-2</sup>compared to the 1990s and that the increased uptake was shared between the tropics and the high latitudes. OCCIPUT shows that intrinsic ocean variability modifies the mean ocean heat uptake change by up to 0.05 W m<sup>-2</sup>or ±15%. Moreover composite analysis of the ensemble members with the most extreme individual decadal heat uptake changes pinpoints the southern and northern high latitudes as the regions where intrinsic variability plays a large role: tropical heat uptake change is largely fixed by the surface forcing. The western boundary currents and the Antarctic Circumpolar Current (i.e. eddy rich regions) are responsible for the range of simulated ocean heat uptake, with the North Pacific exhibiting a particularly strong signal. The origin of this North Pacific signal is traced to decadal timescale latitudinal excursions of the Kuroshio western boundary current.</p>

scholarly journals Robust Seasonality of Arctic Warming Processes in Two Different Versions of the MIROC GCM

2014 ◽  
Vol 27 (16) ◽  
pp. 6358-6375 ◽  
Author(s):  
Masakazu Yoshimori ◽  
Ayako Abe-Ouchi ◽  
Masahiro Watanabe ◽  
Akira Oka ◽  
Tomoo Ogura
Keyword(s):  
Climate Models ◽  
Co2 Concentration ◽  
The Arctic ◽  
Ocean Heat Uptake ◽  
Arctic Warming ◽  
Surface Warming ◽  
Relative Contribution ◽  
Heat Uptake ◽  
Balance Analysis ◽  
The Difference

Abstract It is one of the most robust projected responses of climate models to the increase of atmospheric CO2 concentration that the Arctic experiences a rapid warming with a magnitude larger than the rest of the world. While many processes are proposed as important, the relative contribution of individual processes to the Arctic warming is not often investigated systematically. Feedbacks are quantified in two different versions of an atmosphere–ocean GCM under idealized transient experiments based on an energy balance analysis that extends from the surface to the top of the atmosphere. The emphasis is placed on the largest warming from late autumn to early winter (October–December) and the difference from other seasons. It is confirmed that dominating processes vary with season. In autumn, the largest contribution to the Arctic surface warming is made by a reduction of ocean heat storage and cloud radiative feedback. In the annual mean, on the other hand, it is the albedo feedback that contributes the most, with increasing ocean heat uptake to the deeper layers working as a negative feedback. While the qualitative results are robust between the two models, they differ quantitatively, indicating the need for further constraint on each process. Ocean heat uptake, lower tropospheric stability, and low-level cloud response probably require special attention.

Importance of Ocean Heat Uptake Efficacy to Transient Climate Change

2010 ◽  
Vol 23 (9) ◽  
pp. 2333-2344 ◽  
Author(s):  
Michael Winton ◽  
Ken Takahashi ◽  
Isaac M. Held
Keyword(s):  
Climate Change ◽  
Climate Models ◽  
Climate Model ◽  
Balance Model ◽  
Intergovernmental Panel ◽  
Ocean Heat Uptake ◽  
Transient Climate Response ◽  
Surface Warming ◽  
Global Mean Temperature ◽  
Heat Uptake

Abstract This article proposes a modification to the standard forcing–feedback diagnostic energy balance model to account for 1) differences between effective and equilibrium climate sensitivities and 2) the variation of effective sensitivity over time in climate change experiments with coupled atmosphere–ocean climate models. In the spirit of Hansen et al. an efficacy factor is applied to the ocean heat uptake. Comparing the time evolution of the surface warming in high and low efficacy models demonstrates the role of this efficacy in the transient response to CO2 forcing. Abrupt CO2 increase experiments show that the large efficacy of the Geophysical Fluid Dynamics Laboratory’s Climate Model version 2.1 (CM2.1) sets up in the first two decades following the increase in forcing. The use of an efficacy is necessary to fit this model’s global mean temperature evolution in periods with both increasing and stable forcing. The intermodel correlation of transient climate response with ocean heat uptake efficacy is greater than its correlation with equilibrium climate sensitivity in an ensemble of climate models used for the third and fourth Intergovernmental Panel on Climate Change (IPCC) assessments. When computed at the time of doubling in the standard experiment with 1% yr−1 increase in CO2, the efficacy is variable amongst the models but is generally greater than 1, averages between 1.3 and 1.4, and is as large as 1.75 in several models.

Controls of the Transient Climate Response to Emissions: effects of physical feedbacks, heat uptake and saturation of radiative forcing

2020 ◽  
Author(s):  
Ric Williams ◽  
Paulo Ceppi ◽  
Anna Katavouta
Keyword(s):  
Carbon Emissions ◽  
Radiative Forcing ◽  
Carbon Emission ◽  
Atmospheric Co2 ◽  
Climate Response ◽  
Climate Feedbacks ◽  
Ocean Heat Uptake ◽  
Transient Climate Response ◽  
Surface Warming ◽  
Heat Uptake

<p>The surface warming response to carbon emissions, defines a climate metric, the Transient Climate Response to cumulative carbon Emissions (TCRE), which is important in estimating how much carbon may be emitted to avoid dangerous climate. The TCRE is diagnosed from a suite of 9 CMIP6 Earth system models following an annual 1% rise in atmospheric CO2 over 140 years.   The TCRE   is nearly constant in time during emissions for these climate models, but its value   differs between individual models. The near constancy of this climate metric is due to a strengthening in the surface warming per unit radiative forcing, involving a weakening in both the climate feedback parameter and   fraction of radiative forcing warming the ocean interior, which are compensated by a weakening in the radiative forcing per unit carbon emission from the radiative forcing saturating with increasing atmospheric CO2. Inter-model differences in the TCRE are mainly controlled by the   surface warming response to radiative forcing with large inter-model differences in physical climate feedbacks dominating over smaller, partly compensating differences in ocean heat uptake. Inter-model differences in the radiative forcing per unit carbon emission   provide smaller inter-model differences in the TCRE, which are mainly due to differences in the ratio of the radiative forcing and change in atmospheric CO2 rather than from differences in the airborne fraction.     Hence, providing tighter constraints in the climate projections for the TCRE during emissions requires improving estimates of the physical climate feedbacks,   the rate of ocean   heat uptake, and how the radiative forcing saturates with atmospheric CO2.</p>

scholarly journals Surface warming hiatus caused by increased heat uptake across multiple ocean basins

2014 ◽  
Vol 41 (22) ◽  
pp. 7868-7874 ◽  
Author(s):  
S. S. Drijfhout ◽  
A. T. Blaker ◽  
S. A. Josey ◽  
A. J. G. Nurser ◽  
B. Sinha ◽  
...  
Keyword(s):  
Surface Warming ◽  
Heat Uptake ◽  
Warming Hiatus

Global warming pattern formation: the role of ocean heat uptake

2021 ◽  
pp. 1-46
Keyword(s):  
Pattern Formation ◽  
Coupled Model ◽  
Cooling Effect ◽  
Ocean Heat Uptake ◽  
Surface Warming ◽  
Warming Pattern ◽  
Ocean Atmosphere ◽  
Heat Uptake ◽  
Global Mean

Abstract This study investigates the formation mechanism of ocean surface warming pattern in response to a doubling CO2 with a focus on the role of ocean heat uptake (or ocean surface heat flux change, ΔQnet). We demonstrate that the transient patterns of surface warming and rainfall change simulated by the dynamic ocean-atmosphere coupled model (DOM) can be reproduced by the equilibrium solutions of the slab ocean-atmosphere coupled model (SOM) simulations when forced with the DOM ΔQnet distribution. The SOM is then used as a diagnostic, inverse modeling tool to decompose the CO2-induced thermodynamic warming effect and the ΔQnet (ocean heat uptake)-induced cooling effect. As ΔQnet is largely positive (i.e., downward into the ocean) in the subpolar oceans and weakly negative at the equator, its cooling effect is strongly polar amplified and opposes the CO2 warming, reducing the net warming response especially over Antarctica. For the same reason, the ΔQnet-induced cooling effect contributes significantly to the equatorially enhanced warming in all three ocean basins, while the CO2 warming effect plays a role in the equatorial warming of the eastern Pacific. The spatially varying component of ΔQnet, although globally averaged to zero, can effectively rectify and lead to decreased global mean surface temperature of a comparable magnitude as the global mean ΔQnet effect under transient climate change. Our study highlights the importance of air-sea interaction in the surface warming pattern formation and the key role of ocean heat uptake pattern.

Controls of the TCRE in Earth system models

2021 ◽  
Author(s):  
Ric Williams ◽  
Paulo Ceppi ◽  
Anna Katavouta
Keyword(s):  
Radiative Forcing ◽  
Thermal Response ◽  
Earth System ◽  
Climate Feedbacks ◽  
Ocean Heat Uptake ◽  
Surface Warming ◽  
System Models ◽  
Heat Uptake ◽  
Ocean Carbon ◽  
Earth System Models

<p>The controls of a climate metric, the Transient Climate Response to cumulative carbon Emissions (TCRE), are assessed using a suite of Earth system models, 9 CMIP6 and 7 CMIP5, following an annual 1% rise in atmospheric CO2 over 140 years. The TCRE is interpreted in terms of a product of three dependences: (i) a thermal response involving the surface warming dependence on radiative forcing (including the effects of physical climate feedbacks and planetary heat uptake), (ii) a radiative response involving the radiative forcing dependence on changes in atmospheric carbon and (iii) a carbon response involving the airborne fraction (involving terrestrial and ocean carbon uptake). The near constancy of the TCRE is found to result primarily from a compensation between two factors: (i) the thermal response strengthens  in time from more surface warming per radiative forcing due to a strengthening in surface warming from short-wave cloud feedbacks and a declining effectiveness of ocean heat uptake, while  (ii) the radiative response weakens in time due to a saturation in the radiative forcing with increasing atmospheric carbon. This near constancy of the TCRE at least in complex Earth system models appears to be rather fortuitous given the competing effects of physical climate feedbacks, saturation in radiative forcing, changes in ocean heat uptake and changes in terrestrial and ocean carbon uptake.</p><p>Intermodel differences in the TCRE are mainly controlled by the thermal response, which arise through large differences in physical climate feedbacks that are only partly compensated by smaller differences in ocean heat uptake. The other contributions to the TCRE from the radiative and carbon responses are of comparable importance to the contribution from the thermal response on timescales of 50 years and longer for our subset of CMIP5 models, and 100 years and longer for our subset of CMIP6 models.</p><p> </p>

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