Is there warming in the pipeline? A multi-model analysis of the zero emission commitment from CO2

2020 ◽  
Author(s):  
Andrew H. MacDougall ◽  
Thomas L. Frölicher ◽  
Chirs D. Jones ◽  
Joeri Rogelj ◽  
H. Damon Matthews ◽  
...  
Keyword(s):  
Carbon Budget ◽  
Carbon Uptake ◽  
Model Intercomparison ◽  
Ocean Heat Uptake ◽  
Global Mean Temperature ◽  
Ensemble Mean ◽  
Intercomparison Project ◽  
Ocean Carbon ◽  
Earth System Models ◽  
Global Mean

<p>The Zero Emissions Commitment (ZEC) is the change in global mean temperature expected to occur following the cessation of net CO<sub>2</sub> emissions, and as such is a critical parameter for calculating the remaining carbon budget. The Zero Emissions Commitment Model Intercomparison Project (ZECMIP) was established to gain a better understanding of the potential magnitude and sign of ZEC, in addition to the processes that underlie this metric. Eighteen Earth system models of both full and intermediate complexity participated in ZECMIP. All models conducted an experiment where atmospheric CO<sub>2</sub> concentration increases exponentially until 1000 PgC has been emitted. Thereafter emissions are set to zero and models are configured to allow free evolution of atmospheric CO<sub>2</sub> concentration. The inter-model range of ZEC 50 years after emissions cease for the 1000 PgC experiment is -0.36 to 0.29 <sup>o</sup>C with a model ensemble mean of -0.06 <sup>o</sup>C, median of -0.05 <sup>o</sup>C and standard deviation of 0.19 <sup>o</sup>C. Models exhibit a wide variety of behaviours after emissions cease, with some models continuing to warm for decades to millennia and others cooling substantially. Analysis shows that both ocean carbon uptake and carbon uptake by the terrestrial biosphere are important for counteracting the warming effect from reduction in ocean heat uptake in the decades after emissions cease.</p><p> </p><p>Overall, the most likely value of ZEC on decadal time-scales is assessed to be close to zero, consistent with prior work. However substantial continued warming for decades or centuries following cessation of emission is a feature of a minority of the assessed models and thus cannot be ruled out.</p>

scholarly journals Is there warming in the pipeline? A multi-model analysis of the zero emission commitment from CO<sub>2</sub>

2020 ◽  
Author(s):  
Andrew H. MacDougall ◽  
Thomas L. Frölicher ◽  
Chris D. Jones ◽  
Joeri Rogelj ◽  
H. Damon Matthews ◽  
...  
Keyword(s):  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Gradual Transition ◽  
Carbon Uptake ◽  
Ocean Heat Uptake ◽  
Atmospheric Co2 Concentration ◽  
Global Mean Temperature ◽  
Intercomparison Project ◽  
Ocean Carbon ◽  
Earth System Models

Abstract. The Zero Emissions Commitment (ZEC) is the change in global mean temperature expected to occur following the cessation of net CO2 emissions, and as such is a critical parameter for calculating the remaining carbon budget. The Zero Emissions Commitment Model Intercomparison Project (ZECMIP) was established to gain a better understanding of the potential magnitude and sign of ZEC, in addition to the processes that underlie this metric. Eighteen Earth system models of both full and intermediate complexity participated in ZECMIP. All models conducted an experiment where atmospheric CO2 concentration increases exponentially until 1000 PgC has been emitted. Thereafter emissions are set to zero and models are configured to allow free evolution of atmospheric CO2 concentration. Many models conducted additional second priority simulations with different cumulative emissions totals and an alternative idealized emissions pathway with a gradual transition to zero emissions. The inter-model range of ZEC 50 years after emissions cease for the 1000 PgC experiment is − 0.36 to 0.29 ºC with a model ensemble mean of −0.06 ºC, median of −0.05 ºC and standard deviation of 0.19 ºC. Models exhibit a wide variety of behaviours after emissions cease, with some models continuing to warm for decades to millennia and others cooling substantially. Analysis shows that both ocean carbon uptake and carbon uptake by the terrestrial biosphere are important for counteracting the warming effect from reduction in ocean heat uptake in the decades after emissions cease. Overall, the most likely value of ZEC on multi-decadal timescales is close to zero, consistent with previous model experiments.

scholarly journals Reduced Complexity Model Intercomparison Project Phase 1: introduction and evaluation of global-mean temperature response

2020 ◽  
Vol 13 (11) ◽  
pp. 5175-5190
Author(s):  
Zebedee R. J. Nicholls ◽  
Malte Meinshausen ◽  
Jared Lewis ◽  
Robert Gieseke ◽  
Dietmar Dommenget ◽  
...  
Keyword(s):  
Phase 1 ◽  
Temperature Response ◽  
Earth System ◽  
Model Intercomparison ◽  
Radiative Forcings ◽  
Global Mean Temperature ◽  
Mean Temperature ◽  
Intercomparison Project ◽  
Reduced Complexity ◽  
Global Mean

Abstract. Reduced-complexity climate models (RCMs) are critical in the policy and decision making space, and are directly used within multiple Intergovernmental Panel on Climate Change (IPCC) reports to complement the results of more comprehensive Earth system models. To date, evaluation of RCMs has been limited to a few independent studies. Here we introduce a systematic evaluation of RCMs in the form of the Reduced Complexity Model Intercomparison Project (RCMIP). We expect RCMIP will extend over multiple phases, with Phase 1 being the first. In Phase 1, we focus on the RCMs' global-mean temperature responses, comparing them to observations, exploring the extent to which they emulate more complex models and considering how the relationship between temperature and cumulative emissions of CO2 varies across the RCMs. Our work uses experiments which mirror those found in the Coupled Model Intercomparison Project (CMIP), which focuses on complex Earth system and atmosphere–ocean general circulation models. Using both scenario-based and idealised experiments, we examine RCMs' global-mean temperature response under a range of forcings. We find that the RCMs can all reproduce the approximately 1 ∘C of warming since pre-industrial times, with varying representations of natural variability, volcanic eruptions and aerosols. We also find that RCMs can emulate the global-mean temperature response of CMIP models to within a root-mean-square error of 0.2 ∘C over a range of experiments. Furthermore, we find that, for the Representative Concentration Pathway (RCP) and Shared Socioeconomic Pathway (SSP)-based scenario pairs that share the same IPCC Fifth Assessment Report (AR5)-consistent stratospheric-adjusted radiative forcing, the RCMs indicate higher effective radiative forcings for the SSP-based scenarios and correspondingly higher temperatures when run with the same climate settings. In our idealised setup of RCMs with a climate sensitivity of 3 ∘C, the difference for the ssp585–rcp85 pair by 2100 is around 0.23∘C(±0.12 ∘C) due to a difference in effective radiative forcings between the two scenarios. Phase 1 demonstrates the utility of RCMIP's open-source infrastructure, paving the way for further phases of RCMIP to build on the research presented here and deepen our understanding of RCMs.

scholarly journals The impact of stratospheric aerosol intervention on the North Atlantic and Quasi-Biennial Oscillations in the Geoengineering Model Intercomparison Project (GeoMIP) G6sulfur experiment

2021 ◽  
Author(s):  
Andy Jones ◽  
Jim M. Haywood ◽  
Adam A. Scaife ◽  
Olivier Boucher ◽  
Matthew Henry ◽  
...  
Keyword(s):  
North Atlantic ◽  
Stratospheric Aerosol ◽  
Injection Rate ◽  
Model Intercomparison ◽  
Quasi Biennial Oscillation ◽  
The North ◽  
Global Mean Temperature ◽  
Intercomparison Project ◽  
The Impact ◽  
Earth System Models

Abstract. As part of the Geoengineering Model Intercomparison Project a numerical experiment known as G6sulfur has been designed in which temperatures under a high-forcing future scenario (SSP5-8.5) are reduced to those under a medium-forcing scenario (SSP2-4.5) using the proposed geoengineering technique of stratospheric aerosol intervention (SAI). G6sulfur involves introducing sulphate aerosol into the tropical stratosphere where it reflects incoming sunlight back to space, thus cooling the planet. Here we compare the results from six Earth-system models which have performed the G6sulfur experiment and examine how SAI affects two important modes of natural variability, the northern wintertime North Atlantic Oscillation (NAO) and the Quasi-Biennial Oscillation (QBO). Although all models show that SAI is successful in reducing global-mean temperature as designed, they are also consistent in showing that it forces an increasingly positive phase of the NAO as the injection rate increases over the course of the 21st century, exacerbating precipitation reductions over parts of southern Europe compared with SSP5-8.5. In contrast to the robust result for the NAO there is less consistency for the impact on the QBO, but the results nevertheless indicate a risk that equatorial SAI could cause the QBO to stall and become locked in a phase with permanent westerly winds in the lower stratosphere.

scholarly journals FGOALS-g3 Model Datasets for CMIP6 Flux-Anomaly-Forced Model Intercomparison Project

2020 ◽  
Vol 37 (10) ◽  
pp. 1093-1101
Author(s):  
Yaqi Wang ◽  
Zipeng Yu ◽  
Pengfei Lin ◽  
Hailong Liu ◽  
Jiangbo Jin ◽  
...  
Keyword(s):  
Sea Level ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Global Ocean ◽  
Model Intercomparison ◽  
Ocean Heat Uptake ◽  
Intercomparison Project ◽  
Global Mean

Abstract The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) is an endorsed Model Intercomparison Project in phase 6 of the Coupled Model Intercomparison Project (CMIP6). The goal of FAFMIP is to investigate the spread in the atmosphere-ocean general circulation model projections of ocean climate change forced by increased CO2, including the uncertainties in the simulations of ocean heat uptake, global mean sea level rise due to ocean thermal expansion and dynamic sea level change due to ocean circulation and density changes. The FAFMIP experiments have already been conducted with the Flexible Global Ocean-Atmosphere-Land System Model, gridpoint version 3.0 (FGOALS-g3). The model datasets have been submitted to the Earth System Grid Federation (ESGF) node. Here, the details of the experiments, the output variables and some baseline results are presented. Compared with the preliminary results of other models, the evolutions of global mean variables can be reproduced well by FGOALS-g3. The simulations of spatial patterns are also consistent with those of other models in most regions except the North Atlantic and the Southern Ocean, indicating large uncertainties in the regional sea level projections of these two regions.

scholarly journals The Zero Emissions Commitment Model Intercomparison Project (ZECMIP) contribution to C4MIP: quantifying committed climate changes following zero carbon emissions

2019 ◽  
Vol 12 (10) ◽  
pp. 4375-4385 ◽  
Author(s):  
Chris D. Jones ◽  
Thomas L. Frölicher ◽  
Charles Koven ◽  
Andrew H. MacDougall ◽  
H. Damon Matthews ◽  
...  
Keyword(s):  
Co2 Emissions ◽  
Temperature Change ◽  
General Circulation ◽  
Carbon Budget ◽  
Quantitative Information ◽  
Earth System ◽  
Model Intercomparison ◽  
System Models ◽  
Intercomparison Project ◽  
Earth System Models

Abstract. The amount of additional future temperature change following a complete cessation of CO2 emissions is a measure of the unrealized warming to which we are committed due to CO2 already emitted to the atmosphere. This “zero emissions commitment” (ZEC) is also an important quantity when estimating the remaining carbon budget – a limit on the total amount of CO2 emissions consistent with limiting global mean temperature at a particular level. In the recent IPCC Special Report on Global Warming of 1.5 ∘C, the carbon budget framework used to calculate the remaining carbon budget for 1.5 ∘C included the assumption that the ZEC due to CO2 emissions is negligible and close to zero. Previous research has shown significant uncertainty even in the sign of the ZEC. To close this knowledge gap, we propose the Zero Emissions Commitment Model Intercomparison Project (ZECMIP), which will quantify the amount of unrealized temperature change that occurs after CO2 emissions cease and investigate the geophysical drivers behind this climate response. Quantitative information on ZEC is a key gap in our knowledge, and one that will not be addressed by currently planned CMIP6 simulations, yet it is crucial for verifying whether carbon budgets need to be adjusted to account for any unrealized temperature change resulting from past CO2 emissions. We request only one top-priority simulation from comprehensive general circulation Earth system models (ESMs) and Earth system models of intermediate complexity (EMICs) – a branch from the 1 % CO2 run with CO2 emissions set to zero at the point of 1000 PgC of total CO2 emissions in the simulation – with the possibility for additional simulations, if resources allow. ZECMIP is part of CMIP6, under joint sponsorship by C4MIP and CDRMIP, with associated experiment names to enable data submissions to the Earth System Grid Federation. All data will be published and made freely available.

scholarly journals Modelling mid-Pliocene climate with COSMOS

2012 ◽  
Vol 5 (5) ◽  
pp. 1221-1243 ◽  
Author(s):  
C. Stepanek ◽  
G. Lohmann
Keyword(s):  
Surface Air Temperature ◽  
Pi Control ◽  
Earth System ◽  
Model Intercomparison ◽  
Experimental Procedure ◽  
Intercomparison Project ◽  
Model Setup ◽  
Fully Coupled ◽  
Earth System Models ◽  
Global Mean

Abstract. In this manuscript we describe the experimental procedure employed at the Alfred Wegener Institute in Germany in the preparation of the simulations for the Pliocene Model Intercomparison Project (PlioMIP). We present a description of the utilized Community Earth System Models (COSMOS, version: COSMOS-landveg r2413, 2009) and document the procedures that we applied to transfer the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) Project mid-Pliocene reconstruction into model forcing fields. The model setup and spin-up procedure are described for both the paleo- and preindustrial (PI) time slices of PlioMIP experiments 1 and 2, and general results that depict the performance of our model setup for mid-Pliocene conditions are presented. The mid-Pliocene, as simulated with our COSMOS setup and PRISM boundary conditions, is both warmer and wetter in the global mean than the PI. The globally averaged annual mean surface air temperature in the mid-Pliocene standalone atmosphere (fully coupled atmosphere-ocean) simulation is 17.35 °C (17.82 °C), which implies a warming of 2.23 °C (3.40 °C) relative to the respective PI control simulation.

scholarly journals The Zero Emission Commitment Model Intercomparison Project (ZECMIP) contribution to CMIP6: Quantifying committed climate changes following zero carbon emissions

2019 ◽  
Author(s):  
Chris D. Jones ◽  
Thomas L. Frölicher ◽  
Charles Koven ◽  
Andrew H. MacDougall ◽  
H. Damon Matthews ◽  
...  
Keyword(s):  
Co2 Emissions ◽  
Temperature Change ◽  
General Circulation ◽  
Carbon Budget ◽  
Quantitative Information ◽  
Earth System ◽  
Model Intercomparison ◽  
System Models ◽  
Intercomparison Project ◽  
Earth System Models

Abstract. The amount of additional future temperature change following a complete cessation of CO2 emissions is a measure of the unrealized warming to which we are committed due to CO2 already emitted to the atmosphere. This "Zero Emissions Commitment" (ZEC) is also an important quantity when estimating the remaining carbon budget – a limit on the total amount of CO2 emissions consistent with limiting global mean temperature at a particular level. In the recent IPCC Special Report on Global Warming of 1.5 °C, the carbon budget framework used to calculate the remaining carbon budget for 1.5 °C included the assumption that the ZEC due to CO2 emissions is negligible and close to zero. Previous research has shown significant uncertainty even in the sign of the ZEC. To close this knowledge gap, we propose the Zero Emissions Commitment Model Intercomparison Project (ZECMIP), which will quantify the amount of unrealized temperature change that occurs after CO2 emissions cease and investigate the geophysical drivers behind this climate response. Quantitative information on ZEC is a key gap in our knowledge, and one that will not be addressed by currently planned CMIP6 simulations, yet it is crucial for verifying whether carbon budgets need to be adjusted to account for any unrealized temperature change resulting from past CO2 emissions. We request only one top priority simulation from comprehensive general circulation Earth System Models (ESMs) and Earth System Models of Intermediate Complexity (EMICs) – a branch from the 1 % CO2 run with CO2 emissions set to zero at the point of 1000 PgC of total CO2 emissions in the simulation – with the possibility for additional simulations, if resources allow. ZECMIP is part of CMIP6, under joint sponsorship by C4MIP and CDRMIP, with associated experiment names to enable data submissions to Earth System Grid Federation. All data will be published and made freely available.

scholarly journals Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO<sub>2</sub>

2020 ◽  
Vol 17 (11) ◽  
pp. 2987-3016 ◽  
Author(s):  
Andrew H. MacDougall ◽  
Thomas L. Frölicher ◽  
Chris D. Jones ◽  
Joeri Rogelj ◽  
H. Damon Matthews ◽  
...  
Keyword(s):  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Gradual Transition ◽  
Cumulative Emission ◽  
Ocean Heat Uptake ◽  
Atmospheric Co2 Concentration ◽  
Global Mean Temperature ◽  
Heat Uptake ◽  
Intercomparison Project ◽  
Earth System Models

Abstract. The Zero Emissions Commitment (ZEC) is the change in global mean temperature expected to occur following the cessation of net CO2 emissions and as such is a critical parameter for calculating the remaining carbon budget. The Zero Emissions Commitment Model Intercomparison Project (ZECMIP) was established to gain a better understanding of the potential magnitude and sign of ZEC, in addition to the processes that underlie this metric. A total of 18 Earth system models of both full and intermediate complexity participated in ZECMIP. All models conducted an experiment where atmospheric CO2 concentration increases exponentially until 1000 PgC has been emitted. Thereafter emissions are set to zero and models are configured to allow free evolution of atmospheric CO2 concentration. Many models conducted additional second-priority simulations with different cumulative emission totals and an alternative idealized emissions pathway with a gradual transition to zero emissions. The inter-model range of ZEC 50 years after emissions cease for the 1000 PgC experiment is −0.36 to 0.29 ∘C, with a model ensemble mean of −0.07 ∘C, median of −0.05 ∘C, and standard deviation of 0.19 ∘C. Models exhibit a wide variety of behaviours after emissions cease, with some models continuing to warm for decades to millennia and others cooling substantially. Analysis shows that both the carbon uptake by the ocean and the terrestrial biosphere are important for counteracting the warming effect from the reduction in ocean heat uptake in the decades after emissions cease. This warming effect is difficult to constrain due to high uncertainty in the efficacy of ocean heat uptake. Overall, the most likely value of ZEC on multi-decadal timescales is close to zero, consistent with previous model experiments and simple theory.

scholarly journals Differences in carbon cycle and temperature projections from emission- and concentration-driven earth system model simulations

2014 ◽  
Vol 5 (2) ◽  
pp. 991-1012 ◽  
Author(s):  
P. Shao ◽  
X. Zeng ◽  
X. Zeng
Keyword(s):  
Coupled Model ◽  
System Model ◽  
Carbon Uptake ◽  
Earth System ◽  
Average Difference ◽  
Model Intercomparison ◽  
Feedback Parameter ◽  
Intercomparison Project ◽  
Atmospheric Co2 Concentrations ◽  
Earth System Models

Abstract. The influence of prognostic and prescribed atmospheric CO2 concentrations ([CO2]) on the carbon uptake and temperature is investigated using all eight Earth System Models (ESMs) with relevant output variables from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Under the RCP8.5 scenario, the projected [CO2] differences in 2100 vary from −19.7 to +207.3 ppm in emission-driven ESMs. Incorporation of the interactive concentrations also increases the range of global warming, computed as the 20 year average difference between 2081–2100 and 1850–1869/1861–1880, by 49% from 2.36 K (i.e. ranging from 3.11 to 5.47 K) in the concentration-driven simulations to 3.51 K in the emission-driven simulations. The observed seasonal amplitude of global [CO2] from 1980–2011 is about 1.2–5.3 times as large as those from the eight emission-driven ESMs, while the [CO2] seasonality is simply neglected in concentration-driven ESMs, suggesting the urgent need of ESM improvements in this area. The temperature-concentration feedback parameter α is more sensitive to [CO2] (e.g. during 1980–2005 versus 2075–2100) than how [CO2] is handled (i.e. prognostic versus prescribed). This sensitivity can be substantially reduced by using a more appropriate parameter α' computed from the linear regression of temperature change versus that of the logarithm of [CO2]. However, the inter-model relative variations of both α and α' remain large, suggesting the need of more detailed studies to understand and hopefully reduce these discrepancies.

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.

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