The Community Earth System Model Version 2 (CESM2)

Journal of Advances in Modeling Earth Systems, Journal Year: 2020, Volume and Issue: 12(2)

Published: Jan. 17, 2020

An overview of the Community Earth System Model Version 2 (CESM2) is provided, including a discussion challenges encountered during its development and how they were addressed. In addition, an evaluation pair CESM2 long preindustrial control historical ensemble simulations presented. These performed using nominal 1° horizontal resolution configuration coupled model with both "low-top" (40 km, limited chemistry) "high-top" (130 comprehensive versions atmospheric component. contains many substantial science infrastructure improvements new capabilities since previous major release, CESM1, resulting in improved comparison to CESM1 available observations. include reductions low-latitude precipitation shortwave cloud forcing biases; better representation Madden-Julian Oscillation; El Niño-Southern Oscillation-related teleconnections; global land carbon accumulation trend that agrees well observationally based estimates. Most tropospheric surface features low- high-top are very similar each other, so these present configurations. has equilibrium climate sensitivity 5.1–5.3 °C, larger than primarily due combination relatively small changes microphysics boundary layer parameters. contrast, CESM2's transient response 1.9–2.0 °C comparable CESM1. The outputs from other research community, represent contributions Coupled Intercomparison Project Phase 6.

Language: Английский

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Causes of Higher Climate Sensitivity in CMIP6 Models

Geophysical Research Letters, Journal Year: 2020, Volume and Issue: 47(1)

Published: Jan. 3, 2020

Abstract Equilibrium climate sensitivity, the global surface temperature response to CO doubling, has been persistently uncertain. Recent consensus places it likely within 1.5–4.5 K. Global models (GCMs), which attempt represent all relevant physical processes, provide most direct means of estimating sensitivity via quadrupling experiments. Here we show that closely related effective increased substantially in Coupled Model Intercomparison Project phase 6 (CMIP6), with values spanning 1.8–5.6 K across 27 GCMs and exceeding 4.5 10 them. This (statistically insignificant) increase is primarily due stronger positive cloud feedbacks from decreasing extratropical low coverage albedo. Both these are tied representation clouds CMIP6 lead weaker responses cover water content unforced variations temperature. Establishing plausibility higher imperative given their implied societal ramifications.

Language: Английский

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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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GISS‐E2.1: Configurations and Climatology

Journal of Advances in Modeling Earth Systems, Journal Year: 2020, Volume and Issue: 12(8)

Published: July 10, 2020

This paper describes the GISS-E2.1 contribution to Coupled Model Intercomparison Project, Phase 6 (CMIP6). model version differs from predecessor (GISS-E2) chiefly due parameterization improvements atmospheric and ocean components, while keeping resolution same. skill when compared modern era climatologies is significantly higher than in previous versions. Additionally, updates forcings have a material impact on results. In particular, there been specific representations of modes variability (such as Madden-Julian Oscillation other Pacific) significant simulation climate Southern Oceans, including sea ice. The effective sensitivity 2 × CO2 slightly previously at 2.7-3.1°C (depending version) result lower radiative forcing stronger positive feedbacks.

Language: Английский

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Advances in understanding large‐scale responses of the water cycle to climate change

Annals of the New York Academy of Sciences, Journal Year: 2020, Volume and Issue: 1472(1), P. 49 - 75

Published: April 4, 2020

Abstract Globally, thermodynamics explains an increase in atmospheric water vapor with warming of around 7%/°C near to the surface. In contrast, global precipitation and evaporation are constrained by Earth's energy balance at ∼2–3%/°C. However, this rate is suppressed rapid adjustments response greenhouse gases absorbing aerosols that directly alter budget. Rapid forcings, cooling effects from scattering aerosol, observational uncertainty can explain why observed responses currently difficult detect but expected emerge accelerate as increases aerosol forcing diminishes. Precipitation be smaller over land than ocean due limitations on moisture convergence, exacerbated feedbacks affected adjustments. Thermodynamic fluxes amplify wet dry events, driving intensification extremes. The deviate a simple thermodynamic in‐storm larger‐scale feedback processes, while changes large‐scale dynamics catchment characteristics further modulate frequency flooding increases. Changes circulation radiative evolving surface temperature patterns capable dominating cycle some regions. Moreover, direct impact human activities through abstraction, irrigation, use change already significant component regional importance demand grows population.

Language: Английский

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Ubiquity of human-induced changes in climate variability

Earth System Dynamics, Journal Year: 2021, Volume and Issue: 12(4), P. 1393 - 1411

Published: Dec. 9, 2021

Abstract. While climate change mitigation targets necessarily concern maximum mean state changes, understanding impacts and developing adaptation strategies will be largely contingent on how variability responds to increasing anthropogenic perturbations. Thus far Earth system modeling efforts have primarily focused projected changes the sensitivity of specific modes variability, such as El Niño–Southern Oscillation. However, our knowledge forced in overall spectrum higher-order statistics is relatively limited. Here we present a new 100-member large ensemble projections conducted with Community System Model version 2 over 1850–2100 examine internal fluctuations greenhouse warming. Our unprecedented simulations reveal that considered broadly terms probability distribution, amplitude, frequency, phasing, patterns, are ubiquitous span wide range physical ecosystem variables across many spatial temporal scales. Greenhouse warming model alters variance spectra characterized by non-Gaussian distributions, rainfall, primary production, or fire occurrence. results important implications for efforts, resource management, seasonal predictions, assessing potential stressors terrestrial marine ecosystems.

Language: Английский

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Insights From CMIP6 for Australia's Future Climate

Earth s Future, Journal Year: 2020, Volume and Issue: 8(5)

Published: April 8, 2020

Outputs from new state-of-the-art climate models under the Coupled Model Inter-comparison Project phase 6 (CMIP6) promise improvement and enhancement of change projections information for Australia. Here we focus on three key aspects CMIP6: what is in these models, how available CMIP6 evaluate compared to CMIP5, their future Australian CMIP5 focussing highest emissions scenario. The ensemble has several features relevance policymakers others, example, integrated matrix socioeconomic concentration pathways. show incremental improvements simulation region, including a reduced equatorial Pacific cold tongue bias, slightly improved rainfall teleconnections with large-scale drivers, representation atmosphere ocean extreme heat events, as well dynamic sea level. However, important regional biases remain, evident excessive over Maritime Continent pattern nearby tropical convergence zones. Projections temperature broadly agree those except group higher sensitivity greater warming increase some extremes after 2050. are similar but examined narrower range austral summer Northern Australia winter Southern Overall, national likely be previous versions perhaps areas confidence clarity.

Language: Английский

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Reduced global warming from CMIP6 projections when weighting models by performance and independence

Earth System Dynamics, Journal Year: 2020, Volume and Issue: 11(4), P. 995 - 1012

Published: Nov. 13, 2020

Abstract. The sixth Coupled Model Intercomparison Project (CMIP6) constitutes the latest update on expected future climate change based a new generation of models. To extract reliable estimates warming and related uncertainties from these models, spread in their projections is often translated into probabilistic such as mean likely range. Here, we use model weighting approach, which accounts for models' historical performance several diagnostics well interdependence within CMIP6 ensemble, to calculate constrained distributions global temperature change. We investigate skill our approach perfect test, where previous-generation CMIP5 models pseudo-observations period. distribution weighted abovementioned manner with respect matching then evaluated, find increase about 17 % compared unweighted distribution. In addition, show that independence metric correctly clusters known be similar “family tree”, enables application degree inter-model dependence. apply two observational (the fifth European Centre Medium-Range Weather Forecasts Retrospective Analysis – ERA5, Modern-Era analysis Research Applications, version 2 MERRA-2), constrain under weak (SSP1-2.6) strong (SSP5-8.5) scenarios (SSP refers Shared Socioeconomic Pathways). Our results reduction projected both because some high receive systematically lower weights. end-of-century (2081–2100 relative 1995–2014) SSP5-8.5 3.7 ∘C, 4.1 ∘C without weighting; (66%) uncertainty range 3.1 4.6 equates 13 decrease spread. For SSP1-2.6, 1 (0.7 1.4 ∘C), −0.1 −24 case.

Language: Английский

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Framing, Context, and Methods

Cambridge University Press eBooks, Journal Year: 2023, Volume and Issue: unknown, P. 147 - 286

Published: June 29, 2023

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Language: Английский

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