Plant Physiology Increases the Magnitude and Spread of the Transient Climate Response in CMIP6 Earth System Models

AbstractIncreasing concentrations of CO2 in the atmosphere influence climate both through CO2’s role as a greenhouse gas and through its impact on plants. Plants respond to atmospheric CO2 concentrations in several ways that can alter surface energy and water fluxes and thus surface climate, including changes in stomatal conductance, water use, and canopy leaf area. These plant physiological responses are already embedded in most Earth system models, and a robust literature demonstrates that they can affect global-scale temperature. However, the physiological contribution to transient warming has yet to be assessed systematically in Earth system models. Here this gap is addressed using carbon cycle simulations from phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP) to isolate the radiative and physiological contributions to the transient climate response (TCR), which is defined as the change in globally averaged near-surface air temperature during the 20-yr window centered on the time of CO2 doubling relative to preindustrial CO2 concentrations. In CMIP6 models, the physiological effect contributes 0.12°C (σ: 0.09°C; range: 0.02°–0.29°C) of warming to the TCR, corresponding to 6.1% of the full TCR (σ: 3.8%; range: 1.4%–13.9%). Moreover, variation in the physiological contribution to the TCR across models contributes disproportionately more to the intermodel spread of TCR estimates than it does to the mean. The largest contribution of plant physiology to CO2-forced warming—and the intermodel spread in warming—occurs over land, especially in forested regions.

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Context for interpreting equilibrium climate sensitivity and transient climate response from the CMIP6 Earth system models

Science Advances ◽

10.1126/sciadv.aba1981 ◽

2020 ◽

Vol 6 (26) ◽

pp. eaba1981 ◽

Cited By ~ 21

Author(s):

Gerald A. Meehl ◽

Catherine A. Senior ◽

Veronika Eyring ◽

Gregory Flato ◽

Jean-Francois Lamarque ◽

...

Keyword(s):

Climate Sensitivity ◽

Coupled Model ◽

Cmip5 Models ◽

Climate Response ◽

Earth System ◽

Transient Climate Response ◽

Equilibrium Climate Sensitivity ◽

System Models ◽

Intercomparison Project ◽

Earth System Models

For the current generation of earth system models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6), the range of equilibrium climate sensitivity (ECS, a hypothetical value of global warming at equilibrium for a doubling of CO2) is 1.8°C to 5.6°C, the largest of any generation of models dating to the 1990s. Meanwhile, the range of transient climate response (TCR, the surface temperature warming around the time of CO2 doubling in a 1% per year CO2 increase simulation) for the CMIP6 models of 1.7°C (1.3°C to 3.0°C) is only slightly larger than for the CMIP3 and CMIP5 models. Here we review and synthesize the latest developments in ECS and TCR values in CMIP, compile possible reasons for the current values as supplied by the modeling groups, and highlight future directions. Cloud feedbacks and cloud-aerosol interactions are the most likely contributors to the high values and increased range of ECS in CMIP6.

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INTEGRATING STABLE ISOTOPES IN PRECIPITATION AND EARTH SYSTEM MODELS TO INTERPRET LOCAL WATER CYCLE DYNAMICS

10.1130/abs/2016nc-274917 ◽

2016 ◽

Author(s):

Stephania Zneimer ◽

Keyword(s):

Stable Isotopes ◽

Water Cycle ◽

Earth System ◽

System Models ◽

Local Water ◽

Earth System Models

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The evaluation of Earth System Models: discussion summary

Procedia Environmental Sciences ◽

10.1016/j.proenv.2011.05.023 ◽

2011 ◽

Vol 6 ◽

pp. 216-221

Author(s):

Sönke Zaehle ◽

Colin Prentice ◽

Sarah Cornell

Keyword(s):

Earth System ◽

System Models ◽

Earth System Models

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Using field observations to inform thermal hydrology models of permafrost dynamics with ATS (v0.83)

Geoscientific Model Development Discussions ◽

10.5194/gmdd-8-3235-2015 ◽

2015 ◽

Vol 8 (4) ◽

pp. 3235-3292 ◽

Cited By ~ 5

Author(s):

A. L. Atchley ◽

S. L. Painter ◽

D. R. Harp ◽

E. T. Coon ◽

C. J. Wilson ◽

...

Keyword(s):

Carbon Sink ◽

Thermal Response ◽

Field Measurements ◽

Early Summer ◽

Active Layer Thickness ◽

Earth System ◽

Model Refinement ◽

System Models ◽

Developed Surface ◽

Earth System Models

Abstract. Climate change is profoundly transforming the carbon-rich Arctic tundra landscape, potentially moving it from a carbon sink to a carbon source by increasing the thickness of soil that thaws on a seasonal basis. However, the modeling capability and precise parameterizations of the physical characteristics needed to estimate projected active layer thickness (ALT) are limited in Earth System Models (ESMs). In particular, discrepancies in spatial scale between field measurements and Earth System Models challenge validation and parameterization of hydrothermal models. A recently developed surface/subsurface model for permafrost thermal hydrology, the Advanced Terrestrial Simulator (ATS), is used in combination with field measurements to calibrate and identify fine scale controls of ALT in ice wedge polygon tundra in Barrow, Alaska. An iterative model refinement procedure that cycles between borehole temperature and snow cover measurements and simulations functions to evaluate and parameterize different model processes necessary to simulate freeze/thaw processes and ALT formation. After model refinement and calibration, reasonable matches between simulated and measured soil temperatures are obtained, with the largest errors occurring during early summer above ice wedges (e.g. troughs). The results suggest that properly constructed and calibrated one-dimensional thermal hydrology models have the potential to provide reasonable representation of the subsurface thermal response and can be used to infer model input parameters and process representations. The models for soil thermal conductivity and snow distribution were found to be the most sensitive process representations. However, information on lateral flow and snowpack evolution might be needed to constrain model representations of surface hydrology and snow depth.

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Relationship between physical and biogeochemical parameters and the scenario dependence of the transient climate response to cumulative carbon emissions

Progress in Earth and Planetary Science ◽

10.1186/s40645-020-00392-6 ◽

2020 ◽

Vol 7 (1) ◽

Author(s):

Kaoru Tachiiri

Keyword(s):

Carbon Emissions ◽

Carbon Budget ◽

Extreme Case ◽

Initial Increase ◽

Climate Response ◽

Earth System ◽

Transient Climate Response ◽

Large Correlation ◽

Before And After ◽

Biogeochemical Parameters

AbstractThe transient climate response to cumulative carbon emissions (TCRE) is a key metric in estimating the remaining carbon budget for given temperature targets. However, the TCRE has a small scenario dependence that can be non-negligible for stringent temperature targets. To investigate the parametric correlations and scenario dependence of the TCRE, the present study uses a 512-member ensemble of an Earth system model of intermediate complexity (EMIC) perturbing 11 physical and biogeochemical parameters under scenarios with steady increases of 0.25%, 0.5%, 1%, 2%, or 4% per annum (ppa) in the atmospheric CO2 concentration (pCO2), or an initial increase of 1% followed by an annual decrease of 1% thereafter. Although a small difference of 5% (on average) in the TCRE is observed between the 1-ppa and 0.5-ppa scenarios, a significant scenario dependence is found for the other scenarios, with a tendency toward large values in gradual or decline-after-a-peak scenarios and small values in rapidly increasing scenarios. For all scenarios, correlation analysis indicates a remarkably large correlation between the equilibrium climate sensitivity (ECS) and the relative change in the TCRE, which is attributed to the longer response time of the high ECS model. However, the correlations of the ECS with the TCRE and its scenario dependence for scenarios with large pCO2 increase rates are slightly smaller, and those of biogeochemical parameters such as plant respiration and the overall pCO2–carbon cycle feedback are larger, than in scenarios with gradual increases. The ratio of the TCREs under the overshooting (i.e., 1-ppa decrease after a 1-ppa increase) and 1-ppa increase only scenarios had a clear positive relation with zero-emission commitments. Considering the scenario dependence of the TCRE, the remaining carbon budget for the 1.5 °C target could be reduced by 17 or 22% (before and after considering the unrepresented Earth system feedback) for the most extreme case (i.e., the 67th percentile when using the 0.25-ppa scenario as compared to the 1-ppa increase scenario). A single ensemble EMIC is also used to indicate that, at least for high ECS (high percentile) cases, the scenario dependence of the TCRE should be considered when estimating the remaining carbon budget.

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Evolution of the Arabian Sea Upwelling from the Last Millennium to the Future as Simulated by Earth System Models

Climate ◽

10.3390/cli9050072 ◽

2021 ◽

Vol 9 (5) ◽

pp. 72

Author(s):

Xing Yi ◽

Birgit Hünicke ◽

Eduardo Zorita

Keyword(s):

Arabian Sea ◽

Positive Trend ◽

Last Millennium ◽

Earth System ◽

System Models ◽

Sediment Records ◽

The Future ◽

Water Stratification ◽

Arabian Sea Upwelling ◽

Earth System Models

Arabian Sea upwelling in the past has been generally studied based on the sediment records. We apply two earth system models and analyze the simulated water vertical velocity to investigate coastal upwelling in the western Arabian Sea over the last millennium. In addition, two models with slightly different configurations are also employed to study the upwelling in the 21st century under the strongest and the weakest greenhouse gas emission scenarios. With a negative long-term trend caused by the orbital forcing of the models, the upwelling over the last millennium is found to be closely correlated with the sea surface temperature, the Indian summer Monsoon and the sediment records. The future upwelling under the Representative Concentration Pathway (RCP) 8.5 scenario reveals a negative trend, in contrast with the positive trend displayed by the upwelling favorable along-shore winds. Therefore, it is likely that other factors, like water stratification in the upper ocean layers caused by the stronger surface warming, overrides the effect from the upwelling favorable wind. No significant trend is found for the upwelling under the RCP2.6 scenario, which is likely due to a compensation between the opposing effects of the increase in upwelling favorable winds and the water stratification.

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GFDL’s ESM2 Global Coupled Climate–Carbon Earth System Models. Part I: Physical Formulation and Baseline Simulation Characteristics

Journal of Climate ◽

10.1175/jcli-d-11-00560.1 ◽

2012 ◽

Vol 25 (19) ◽

pp. 6646-6665 ◽

Cited By ~ 620

Author(s):

John P. Dunne ◽

Jasmin G. John ◽

Alistair J. Adcroft ◽

Stephen M. Griffies ◽

Robert W. Hallberg ◽

...

Keyword(s):

Climate Changes ◽

Southern Oscillation ◽

Heat Content ◽

Ocean Dynamics ◽

Thermocline Depth ◽

Earth System ◽

System Models ◽

Model Version ◽

Earth System Models

Abstract The physical climate formulation and simulation characteristics of two new global coupled carbon–climate Earth System Models, ESM2M and ESM2G, are described. These models demonstrate similar climate fidelity as the Geophysical Fluid Dynamics Laboratory’s previous Climate Model version 2.1 (CM2.1) while incorporating explicit and consistent carbon dynamics. The two models differ exclusively in the physical ocean component; ESM2M uses Modular Ocean Model version 4p1 with vertical pressure layers while ESM2G uses Generalized Ocean Layer Dynamics with a bulk mixed layer and interior isopycnal layers. Differences in the ocean mean state include the thermocline depth being relatively deep in ESM2M and relatively shallow in ESM2G compared to observations. The crucial role of ocean dynamics on climate variability is highlighted in El Niño–Southern Oscillation being overly strong in ESM2M and overly weak in ESM2G relative to observations. Thus, while ESM2G might better represent climate changes relating to total heat content variability given its lack of long-term drift, gyre circulation, and ventilation in the North Pacific, tropical Atlantic, and Indian Oceans, and depth structure in the overturning and abyssal flows, ESM2M might better represent climate changes relating to surface circulation given its superior surface temperature, salinity, and height patterns, tropical Pacific circulation and variability, and Southern Ocean dynamics. The overall assessment is that neither model is fundamentally superior to the other, and that both models achieve sufficient fidelity to allow meaningful climate and earth system modeling applications. This affords the ability to assess the role of ocean configuration on earth system interactions in the context of two state-of-the-art coupled carbon–climate models.

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Challenges in simulating sea ice in Earth System Models

Wiley Interdisciplinary Reviews Climate Change ◽

10.1002/wcc.189 ◽

2012 ◽

Vol 3 (6) ◽

pp. 509-526 ◽

Cited By ~ 21

Author(s):

Dirk Notz

Keyword(s):

Sea Ice ◽

Earth System ◽

System Models ◽

Earth System Models

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Assessing the capacity of Earth System Models to simulate spatiotemporal variability in fire weather indicators

10.5194/egusphere-egu21-12208 ◽

2021 ◽

Author(s):

Carolina Gallo Granizo ◽

Jonathan Eden ◽

Bastien Dieppois ◽

Matthew Blackett

Keyword(s):

Climate Change ◽

Spatial Scales ◽

Fire Danger ◽

Spatiotemporal Variability ◽

Global Evaluation ◽

Fire Weather ◽

Earth System ◽

Fire Weather Index ◽

System Models ◽

Earth System Models

Weather and climate play an important role in shaping global fire regimes and geographical distributions of burnable areas. At the global scale, fire danger is likely to increase in the near future due to warmer temperatures and changes in precipitation patterns, as projected by the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). There is a need to develop the most reliable projections of future climate-driven fire danger to enable decision makers and forest managers to take both targeted proactive actions and to respond to future fire events.Climate change projections generated by Earth System Models (ESMs) provide the most important basis for understanding past, present and future changes in the climate system and its impacts. ESMs are, however, subject to systematic errors and biases, which are not fully taken into account when developing risk scenarios for wild fire activity. Projections of climate-driven fire danger have often been limited to the use of single models or the mean of multi-model ensembles, and compared to a single set of observational data (e.g. one index derived from one reanalysis).Here, a comprehensive global evaluation of the representation of a series of fire weather indicators in the latest generation of ESMs is presented. Seven fire weather indices from the Canadian Forest Fire Weather Index System were generated using daily fields realisations simulated by 25 ESMs from the 6th Coupled Model Intercomparison Project (CMIP6). With reference to observational and reanalysis datasets, we quantify the capacity of each model to realistically simulate the variability, magnitude and spatial extent of fire danger. The highest-performing models are identified and, subsequently, the limitations of combining models based on independency and equal performance when generating fire danger projections are discussed. To conclude, recommendations are given for the development of user- and policy-driven model evaluation at spatial scales relevant for decision-making and forest management.

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