Ubiquity of human-induced changes in climate variability

Rodgers, Keith B.; Lee, Sun‐Seon; Rosenbloom, Nan; Timmermann, Axel; Danabasoglu, Gökhan; Deser, Clara; Edwards, Jim; Kim, Jieun; Simpson, Isla R.; Stein, Karl; Stuecker, Malte F.; Yamaguchi, Ryohei; Bódai, Tamás; Chung, Eui‐Seok; Huang, Lei; Kim, Who M.; Lamarque, Jean‐François; Lombardozzi, Danica; Wieder, William R.; Yeager, Stephen

doi:10.5194/esd-12-1393-2021

Cited by 152 publications

(143 citation statements)

References 103 publications

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“…It remains unknown how perturbing the ocean state might affect the internal variability captured by the ensemble. The CESM2 Large Ensemble simulations, combining the different initial oceanic states and atmospheric states, would be helpful to understand this issue (Rodgers et al 2021).…”

Section: Discussionmentioning

confidence: 99%

Two Distinct Modes of Climate Responses to the Anthropogenic Aerosol Forcing Changes

2022

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Unlike greenhouse gases (GHGs), anthropogenic aerosol (AA) concentrations have increased and then decreased over the past century or so, with the timing of the peak concentration varying in different regions. To date, it has been challenging to separate the climate impact of AAs from that due to GHGs and background internal variability. We use a pattern recognition method, taking advantage of spatiotemporal covariance information, to isolate the forced patterns for the surface ocean and associated atmospheric variables from the all-but-one forcing Community Earth System Model ensembles. We find that the aerosol forced responses are dominated by two leading modes with one associated with the historical increase and future decrease of global mean aerosol concentrations (dominated by the NH sources) while the other due to the transition of the primary sources of AA from the West to the East and also from Northern Hemisphere extratropical regions to tropical regions. In particular, the aerosol transition effect, to some extent compensating the global mean effect, exhibits a zonal asymmetry in the surface temperature and salinity responses. We also show that this transition effect dominates the total AA effect during recent decades, e.g. 1967-2007.

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Section: Discussionmentioning

confidence: 99%

Two Distinct Modes of Climate Responses to the Anthropogenic Aerosol Forcing Changes

2022

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“…We use a well et al, 2016) and a recently released large initial-condition ensemble, hereafter referred to as the CESM2-LE (Rodgers et al, 2021). Second, CESM2 has a mean state Arctic sea ice bias.…”

Section: Model Simulations and Comparison Strategiesmentioning

confidence: 99%

“…For CESM2, we use the first 50 ensemble members of the CESM2-LE. As described in Rodgers et al (2021), members 1-50 share the same transient CMIP6 forcing: historical (1850-2014) and the SSP3-7.0 future scenario (2015-2100O'Neill et al, 2016). For CESM2-lessmelt, we ran a four-member mini ensemble using the same historical and SSP3-7.0 CMIP6 forcing as CESM2-LE members 1-50.…”

Section: Model Simulations and Comparison Strategiesmentioning

confidence: 99%

Less Surface Sea Ice Melt in the CESM2 Improves Arctic Sea Ice Simulation With Minimal Non‐Polar Climate Impacts

Kay

DeRepentigny

Holland

et al. 2022

J Adv Model Earth Syst

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This study isolates the influence of sea ice mean state on pre‐industrial climate and transient 1850–2100 climate change within a fully coupled global model: The Community Earth System Model version 2 (CESM2). The CESM2 sea ice model physics is modified to increase surface albedo, reduce surface sea ice melt, and increase Arctic sea ice thickness and late summer cover. Importantly, increased Arctic sea ice in the modified model reduces a present‐day late‐summer ice cover bias. Of interest to coupled model development, this bias reduction is realized without degrading the global simulation including top‐of‐atmosphere energy imbalance, surface temperature, surface precipitation, and major modes of climate variability. The influence of these sea ice physics changes on transient 1850–2100 climate change is compared within a large initial condition ensemble framework. Despite similar global warming, the modified model with thicker Arctic sea ice than CESM2 has a delayed and more realistic transition to a seasonally ice free Arctic Ocean. Differences in transient climate change between the modified model and CESM2 are challenging to detect due to large internally generated climate variability. In particular, two common sea ice benchmarks—sea ice sensitivity and sea ice trends—are of limited value for comparing models with similar global warming. More broadly, these results show the importance of a reasonable Arctic sea ice mean state when simulating the transition to an ice‐free Arctic Ocean in a warming world. Additionally, this work highlights the importance of large initial condition ensembles for credible model‐to‐model and observation‐model comparisons.

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“…Aerosols were simulated using the four-mode version of the Modal Aerosol Module (Liu et al, 2016). Each component was configured at a nominal 1° spatial resolution (Rodgers et al, 2021).…”

Section: Model Datamentioning

confidence: 99%

Increased Variability of Biomass Burning Emissions in CMIP6 Amplifies Hydrologic Cycle in the CESM2 Large Ensemble

Heyblom

Singh

Rasch

et al. 2022

Geophysical Research Letters

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Historical simulations performed for the Coupled Model Intercomparison Project Phase 6 used biomass burning emissions between 1997 and 2014 containing higher spatial and temporal variability compared to emission inventories specified for earlier years, and compared to emissions used in previous (e.g., CMIP5) simulation intercomparisons. Using the Community Earth System Model version 2 Large Ensemble, we show this increased biomass burning emissions variability leads to amplification of the hydrologic cycle poleward of 40°N. Notably, the high variability of biomass burning emissions leads to increased latent heat fluxes, column‐integrated precipitable water, and precipitation. Greater ocean heat uptake, weaker meridional energy transport from the tropics, greater atmospheric shortwave and longwave absorption, and lower relative humidity act to moderate this hydrologic cycle amplification. Our results suggest it is not only the secular changes (on multidecadal timescales) in biomass burning emissions that impact the hydrologic cycle, but also the shorter timescale variability in emissions.

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Ubiquity of human-induced changes in climate variability

Cited by 152 publications

References 103 publications

Two Distinct Modes of Climate Responses to the Anthropogenic Aerosol Forcing Changes

Two Distinct Modes of Climate Responses to the Anthropogenic Aerosol Forcing Changes

Less Surface Sea Ice Melt in the CESM2 Improves Arctic Sea Ice Simulation With Minimal Non‐Polar Climate Impacts

Increased Variability of Biomass Burning Emissions in CMIP6 Amplifies Hydrologic Cycle in the CESM2 Large Ensemble

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