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

Science Advances, Journal Year: 2020, Volume and Issue: 6(26)

Published: June 24, 2020

A historical context is provided for interpreting the equilibrium climate sensitivity (ECS) and transient response (TCR).

Language: Английский

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Overview of the Norwegian Earth System Model (NorESM2) and key climate response of CMIP6 DECK, historical, and scenario simulations

Geoscientific model development, Journal Year: 2020, Volume and Issue: 13(12), P. 6165 - 6200

Published: Dec. 4, 2020

The second version of the coupled Norwegian Earth System Model (NorESM2) is presented and evaluated. NorESM2 based on Community (CESM2) shares with CESM2 computer code infrastructure many system model components. However, employs entirely different ocean biogeochemistry models. atmosphere component (CAM-Nor) includes a module for aerosol physics chemistry, including interactions cloud radiation; additionally, CAM-Nor improvements in formulation local dry moist energy conservation, global angular momentum computations deep convection air–sea fluxes. surface components have minor changes albedo calculations to land sea-ice We present results from simulations that were carried out sixth phase Coupled Intercomparison Project (CMIP6). Two versions are used: one lower (∼ 2∘) atmosphere–land resolution medium 1∘) resolution. stability pre-industrial climate sensitivity abrupt gradual quadrupling CO2 assessed, along ability simulate historical under CMIP6 forcings. Compared observations reanalyses, represents an improvement over previous NorESM most aspects. appears less sensitive greenhouse gas forcing than its predecessors, estimated equilibrium 2.5 K both resolutions 150-year time frame; however, this estimate increases window at equilibration much higher. also consider response future scenarios as defined by selected Shared Socioeconomic Pathways (SSPs) Scenario CMIP6. Under four (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5), warming period 2090–2099 compared 1850–1879 reaches 1.3, 2.2, 3.0, 3.9 NorESM2-LM, 2.1, 3.1, NorESM-MM, robustly similar resolutions. NorESM2-LM shows rather satisfactory evolution recent area. In ice-free Arctic Ocean only avoided SSP1-2.6 scenario.

Language: Английский

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Carbon–concentration and carbon–climate feedbacks in CMIP6 models and their comparison to CMIP5 models

Biogeosciences, Journal Year: 2020, Volume and Issue: 17(16), P. 4173 - 4222

Published: Aug. 18, 2020

Abstract. Results from the fully and biogeochemically coupled simulations in which CO2 increases at a rate of 1 % yr−1 (1pctCO2) its preindustrial value are analyzed to quantify magnitude carbon–concentration carbon–climate feedback parameters measure response ocean terrestrial carbon pools changes atmospheric concentration resulting change global climate, respectively. The results based on 11 comprehensive Earth system models most recent (sixth) Coupled Model Intercomparison Project (CMIP6) compared with eight fifth CMIP (CMIP5). strength is comparable magnitudes over land (mean ± standard deviation = 0.97 0.40 PgC ppm−1) (0.79 0.07 ppm−1), while (−45.1 50.6 ∘C−1) about 3 times larger than (−17.2 5.0 ∘C−1). both feedbacks an order more uncertain as has been seen existing studies. These values their spread CMIP6 have not changed significantly CMIP5 models. absolute lower for that include representation nitrogen cycle. transient climate cumulative emissions (TCRE) considered here 1.77 0.37 ∘C EgC−1 similar found (1.63 0.48 EgC−1) but somewhat reduced model spread. expressions configurations 1pctCO2 simulation simplified when small temperature ignored. Decomposition terms these used gain insight into reasons differing responses among cycle

Language: Английский

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The Chemistry Mechanism in the Community Earth System Model Version 2 (CESM2)

Journal of Advances in Modeling Earth Systems, Journal Year: 2020, Volume and Issue: 12(4)

Published: March 25, 2020

Abstract The Community Earth System Model version 2 (CESM2) includes a detailed representation of chemistry throughout the atmosphere in Atmosphere with and Whole Climate configurations. These model configurations use for Ozone Related chemical Tracers (MOZART) family mechanisms, covering troposphere, stratosphere, mesosphere, lower thermosphere. new MOZART tropospheric scheme (T1) has number updates over previous (MOZART‐4) CESM, including improvements to oxidation isoprene terpenes, organic nitrate speciation, aromatic speciation thus improved ozone secondary aerosol precursors. An evaluation present‐day simulations CESM2 being provided Intercomparison Project round 6 (CMIP6) is presented. simulations, using anthropogenic biomass burning emissions from inventories specified CMIP6, as well online calculation biogenic compounds, lightning NO, dust, sea salt, indicate an underestimate variety carbon monoxide hydrocarbons. simulation surface southeast United States versions, largely due reactive nitrogen compounds resulting production rate than CESM1 but still overestimates observations summer. agrees ozonesonde many parts globe. comparison NO x PAN aircraft indicates simulates budget well.

Language: Английский

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Global predictions of primary soil salinization under changing climate in the 21st century

Nature Communications, Journal Year: 2021, Volume and Issue: 12(1)

Published: Nov. 18, 2021

Soil salinization has become one of the major environmental and socioeconomic issues globally this is expected to be exacerbated further with projected climatic change. Determining how climate change influences dynamics naturally-occurring soil scarcely been addressed due highly complex processes influencing salinization. This paper sets out address long-standing challenge by developing data-driven models capable predicting primary (naturally-occurring) salinity its variations in world's drylands up year 2100 under changing climate. Analysis future predictions made here identifies dryland areas South America, southern western Australia, Mexico, southwest United States, Africa as hotspots. Conversely, we project a decrease northwest Horn Africa, Eastern Europe, Turkmenistan, west Kazakhstan response over same period. Excess salt accumulation root zone causes health, biodiversity food security. Authors used machine learning algorithms predict global scale 21st century.

Language: Английский

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Climate model projections from the Scenario Model Intercomparison Project (ScenarioMIP) of CMIP6

Earth System Dynamics, Journal Year: 2021, Volume and Issue: 12(1), P. 253 - 293

Published: March 1, 2021

Abstract. The Scenario Model Intercomparison Project (ScenarioMIP) defines and coordinates the main set of future climate projections, based on concentration-driven simulations, within Coupled phase 6 (CMIP6). This paper presents a range its outcomes by synthesizing results from participating global coupled Earth system models. We limit our scope to analysis strictly geophysical outcomes: mainly averages spatial patterns change for surface air temperature precipitation. also compare CMIP6 projections CMIP5 results, especially those scenarios that were designed provide continuity across CMIP phases, at same time highlighting important differences in forcing composition, as well results. precipitation changes end century (2081–2100) encompassing Tier 1 experiments Shared Socioeconomic Pathway (SSP) (SSP1-2.6, SSP2-4.5, SSP3-7.0 SSP5-8.5) SSP1-1.9 spans larger compared CMIP5, due higher warming (by close 1.5 ∘C) reached upper 5 %–95 % envelope highest scenario (SSP5-8.5). is both wider radiative new cover sensitivities some models their predecessors. Spatial averaged over have familiar features, an variations confirms model structural be dominant source uncertainty. Models differ with respect size evolution internal variability measured individual models' initial condition ensemble spreads, according simulations available under SSP3-7.0. These suggest tendency decrease along course this scenario, result will benefit further Benefits mitigation, all else being equal terms societal drivers, appear clearly when comparing developed SSP but which different degrees mitigation been applied. It found mild overshoot few decades around mid-century, represented SSP5-3.4OS, does not affect outcome 2100, return levels gradually increasing SSP4-3.4 (not erasing possibility, however, other aspects may easily reversible). Central estimates means reach given level might biased inclusion shown faster historical period than observed. Those show reaching ∘C 1850–1900 baseline second half current decade, span between slow fast covering 20 27 years present. 2 early 2039 mean SSP5-8.5 late mid-2060s SSP1-2.6. considered (5 only until mid-2090s.

Language: Английский

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Tracking Improvement in Simulated Marine Biogeochemistry Between CMIP5 and CMIP6

Current Climate Change Reports, Journal Year: 2020, Volume and Issue: 6(3), P. 95 - 119

Published: Aug. 18, 2020

The changes or updates in ocean biogeochemistry component have been mapped between CMIP5 and CMIP6 model versions, an assessment made of how far these led to improvements the simulated mean state marine biogeochemical models within current generation Earth system (ESMs).The representation has progressed models. However, it remains difficult identify which are responsible for a given improvement. In addition, full potential terms interactions climate feedback poorly examined models.Increasing availability data, as well improved understanding underlying processes, allows advances components ESMs. present study scrutinizes extent ESMs 5th 6th phases Coupled Model Intercomparison Project (CMIP).

Language: Английский

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CMIP6 Models Predict Significant 21st Century Decline of the Atlantic Meridional Overturning Circulation

Geophysical Research Letters, Journal Year: 2020, Volume and Issue: 47(12)

Published: May 25, 2020

Abstract We explore the representation of Atlantic Meridional Overturning Circulation (AMOC) in 27 models from CMIP6 multimodel ensemble. Comparison with RAPID and SAMBA observations suggests that ensemble mean represents AMOC strength vertical profile reasonably well. Linear trends over entire historical period (1850–2014) are generally neutral, but many exhibit an peak around 1980s. Ensemble decline future (SSP) scenarios is stronger than CMIP5 models. In fact, surprisingly insensitive to scenario at least up 2060. find emergent relationship among a majority between 21st century decline. Constraining this might 6 8 Sv (34–45%) by 2100. A smaller group projects much less weakening only 30%.

Language: Английский

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Effective radiative forcing and adjustments in CMIP6 models

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(16), P. 9591 - 9618

Published: Aug. 17, 2020

Abstract. The effective radiative forcing, which includes the instantaneous forcing plus adjustments from atmosphere and surface, has emerged as key metric of evaluating human natural influence on climate. We evaluate in 17 contemporary climate models that are participating Coupled Model Intercomparison Project (CMIP6) have contributed to Radiative Forcing (RFMIP). Present-day (2014) global-mean anthropogenic relative pre-industrial (1850) levels stands at 2.00 (±0.23) W m−2, comprised 1.81 (±0.09) m−2 CO2, 1.08 (± 0.21) other well-mixed greenhouse gases, −1.01 0.23) aerosols −0.09 (±0.13) land use change. Quoted uncertainties 1 standard deviation across model best estimates, 90 % confidence reported forcings, due internal variability, is typically within 0.1 m−2. majority remaining 0.21 likely be ozone. In most cases, largest contributors spread (ERF) (IRF) cloud responses, particularly aerosol–cloud interactions aerosol forcing. As determined previous studies, cancellation tropospheric surface means stratospherically adjusted approximately equal ERF for gas but not aerosols, consequentially, total. ranges −0.63 −1.37 exhibiting a less negative mean narrower range compared 10 CMIP5 models. 4×CO2 also narrowed CMIP6 13 Aerosol uncorrelated with sensitivity. Therefore, there no evidence suggest increasing sensitivity models, related high-sensitivity consequence stronger present-day little modelling groups systematically tuning or recreate observed historical warming.

Language: Английский

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Antarctic Sea Ice Area in CMIP6

Geophysical Research Letters, Journal Year: 2020, Volume and Issue: 47(9)

Published: April 17, 2020

Abstract Fully coupled climate models have long shown a wide range of Antarctic sea ice states and evolution over the satellite era. Here, we present high‐level evaluation in 40 from most recent phase Coupled Model Intercomparison Project (CMIP6). Many capture key characteristics mean seasonal cycle area (SIA), but some simulate implausible historical compared to observations, leading large intermodel spread. Summer SIA is consistently biased low across ensemble. Compared previous model generation (CMIP5), spread winter summer has reduced, regional distribution concentration improved. Over 1979–2018, many strong negative trends concurrently with stronger‐than‐observed global surface temperature (GMST). By end 21st century, project clear differences between forcing scenarios.

Language: Английский

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