Changing State of the Climate System

Cambridge University Press eBooks, Journal Year: 2023, Volume and Issue: unknown, P. 287 - 422

Published: June 29, 2023

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Language: Английский

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Scattering and absorbing aerosols in the climate system

Nature Reviews Earth & Environment, Journal Year: 2022, Volume and Issue: 3(6), P. 363 - 379

Published: May 24, 2022

Language: Английский

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Antarctic Bottom Water and North Atlantic Deep Water in CMIP6 models

Ocean science, Journal Year: 2021, Volume and Issue: 17(1), P. 59 - 90

Published: Jan. 13, 2021

Abstract. Deep and bottom water formation are crucial components of the global ocean circulation, yet they were poorly represented in previous generation climate models. We here quantify biases Antarctic Bottom Water (AABW) North Atlantic (NADW) formation, properties, transport, extent 35 models that participated latest Climate Model Intercomparison Project (CMIP6). Several CMIP6 correctly forming AABW via shelf processes, but 28 Southern Ocean all form deep open-ocean convection too deeply, often, and/or over large an area. Models convect least most accurate NADW. The four CESM2 with their overflow parameterisation among In Atlantic, colder AABW, stronger abyssal overturning at 30∘ S, further north layer extends. saltier NADW, Meridional Overturning Circulation (AMOC), south NADW Indian Pacific oceans contrast, fresher ones which extend furthest regardless strength overturning, likely because also weakest fronts Circumpolar Current. There clear improvements since CMIP5: several represent or parameterise fewer exhibit convection, more right location Labrador Sea, density reduced, is realistic. However, required, e.g. by generalising use parameterisations coupling to interactive ice sheet models, before hence heat carbon storage, accurately.

Language: Английский

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Climate change in the Baltic Sea region: a summary

Earth System Dynamics, Journal Year: 2022, Volume and Issue: 13(1), P. 457 - 593

Published: March 15, 2022

Abstract. Based on the Baltic Earth Assessment Reports of this thematic issue in System Dynamics and recent peer-reviewed literature, current knowledge effects global warming past future changes climate Sea region is summarised assessed. The study an update Second Climate Change (BACC II) published 2015 focuses atmosphere, land, cryosphere, ocean, sediments, terrestrial marine biosphere. summaries gained palaeo-, historical, regional research, we find that main conclusions from earlier assessments still remain valid. However, new long-term, homogenous observational records, for example, Scandinavian glacier inventories, sea-level-driven saltwater inflows, so-called Major Inflows, phytoplankton species distribution, scenario simulations with improved models, glaciers, lake ice, food web, have become available. In many cases, uncertainties can now be better estimated than before because more models were included ensembles, especially Sea. With help coupled feedbacks between several components system been studied, multiple driver studies performed, e.g. projections web include fisheries, eutrophication, change. New datasets led to a revised understanding some variables such as salinity. Furthermore, it has evident natural variability, particular ocean multidecadal timescales, greater previously estimated, challenging our ability detect observed projected climate. context, first palaeoclimate regionalised are instructive. Hence, increased. addition well-known influence North Atlantic Oscillation, was found also other low-frequency modes internal Multidecadal Variability, profound region. Challenges identified, systematic discrepancy cloudiness trends difficulty confidently attributing large ecosystems Finally, compare results coastal sea assessments, Region (NOSCCA), change differ those Sea, since oceanography very different seas While dynamics dominated by tides, characterised brackish water, perennial vertical stratification southern subbasins, seasonal ice cover northern subbasins.

Language: Английский

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An Overview of Ocean Climate Change Indicators: Sea Surface Temperature, Ocean Heat Content, Ocean pH, Dissolved Oxygen Concentration, Arctic Sea Ice Extent, Thickness and Volume, Sea Level and Strength of the AMOC (Atlantic Meridional Overturning Circulation)

Frontiers in Marine Science, Journal Year: 2021, Volume and Issue: 8

Published: Sept. 21, 2021

Global ocean physical and chemical trends are reviewed updated using seven key climate change indicators: (i) Sea Surface Temperature, (ii) Ocean Heat Content, (iii) pH, (iv) Dissolved Oxygen concentration (v) Arctic Ice extent, thickness, volume (vi) Level (vii) the strength of Atlantic Meridional Overturning Circulation (AMOC). The globally averaged surface temperature shows a mean warming trend 0.062 ± 0.013°C per decade over last 120 years (1900–2019). During (2010–2019) rate has accelerated to 0.280 0.068°C decade, 4.5 times higher than long term mean. Content in upper 2,000 m linear 0.35 0.08 Wm –2 period 1955–2019 (65 years). during is twice (0.70 0.07 ) record. Each six decades have been warmer previous one. pH declined on average by approximately 0.1 units (from 8.2 8.1) since industrial revolution (1770). By end this century (2100) projected decline additionally 0.1–0.4 depending RCP (Representative Concentration Pathway) SSP (Shared Socioeconomic Pathways) future scenario. time emergence signal varies from 8 15 for open sites, 16–41 coastal sites. dissolved oxygen levels decreased 4.8 petamoles or 2% 5 decades, with profound impacts local basin scale habitats. Regional varying due multiple processes impacting oxygen: solubility change, respiration changes, circulation changes multidecadal variability. sea ice extent declining −13.1% summer (September) −2.6% winter (March) 4 (1979–2020). combined thickness indicate that non-seasonal 75% 1979. level increased 1993–2019 (the altimetry era) at 3.15 0.3 mm year –1 experiencing an acceleration ∼ 0.084 (0.06–0.10) . (1900–2015; 115y) global (GMSL) rised 19 cm, near 40% GMSL rise taken place 1993 (22y). Independent proxies evolution (AMOC) AMOC its weakest several hundreds slowing down century. A final visual summary indicators recent provided.

Language: Английский

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The evolution of the North Atlantic Meridional Overturning Circulation since 1980

Nature Reviews Earth & Environment, Journal Year: 2022, Volume and Issue: 3(4), P. 241 - 254

Published: March 1, 2022

Language: Английский

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Natural variability has dominated Atlantic Meridional Overturning Circulation since 1900

Nature Climate Change, Journal Year: 2022, Volume and Issue: 12(5), P. 455 - 460

Published: April 25, 2022

Abstract There is debate about slowing of the Atlantic Meridional Overturning Circulation (AMOC), a key component global climate system. Some focus on sea surface temperature (SST) slightly cooling in parts subpolar North despite widespread ocean warming. SST influenced by AMOC, especially decadal timescales and beyond. The local could thus reflect AMOC diminishing heat transport, consistent with model responses to rising atmospheric greenhouse gas concentrations. Here we show from prevalence natural variability since 1900. This historical simulations for 1900–2014 predicting average 1 Sv at 30° N after 1980, which within range internal multidecadal derived models’ preindustrial control runs. These results highlight importance systematic sustained in-situ monitoring systems that can detect attribute high confidence an anthropogenic signal.

Language: Английский

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Mechanisms and Impacts of Earth System Tipping Elements

Reviews of Geophysics, Journal Year: 2023, Volume and Issue: 61(1)

Published: Feb. 16, 2023

Abstract Tipping elements are components of the Earth system which may respond nonlinearly to anthropogenic climate change by transitioning toward substantially different long‐term states upon passing key thresholds or “tipping points.” In some cases, such changes could produce additional greenhouse gas emissions radiative forcing that compound global warming. Improved understanding tipping is important for predicting future risks and their impacts. Here we review mechanisms, predictions, impacts, knowledge gaps associated with 10 notable proposed be elements. We evaluate approaching critical whether shifts manifest rapidly over longer timescales. Some have a higher risk crossing points under middle‐of‐the‐road pathways will possibly affect major ecosystems, patterns, and/or carbon cycling within 21st century. However, literature assessing scenarios indicates strong potential reduce impacts many through mitigation. The studies synthesized in our suggest most do not possess abrupt years, exhibit behavior, rather responding more predictably directly magnitude forcing. Nevertheless, uncertainties remain elements, highlighting an acute need further research modeling better constrain risks.

Language: Английский

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Contribution of anthropogenic aerosols to persistent La Niña-like conditions in the early 21st century

Proceedings of the National Academy of Sciences, Journal Year: 2024, Volume and Issue: 121(5)

Published: Jan. 22, 2024

The discrepancy between the observed lack of surface warming in eastern equatorial Pacific and climate model projections an El Niño-like pattern confronts research community. While anthropogenic aerosols have been suggested as a cause, prolonged cooling trend over appears conflict with Northern Hemisphere aerosol emission reduction since 1980s. Here, using CESM, we show that superposition fast slow responses to change—an increase followed by decrease—can sustain La Niña-like condition for longer time than expected. rapid adjustment Hadley Cell triggers joint feedback low clouds, wind, evaporation, sea temperature Southeast Pacific, leading wedge-shaped extends central Pacific. Meanwhile, northern subtropical cell gradually intensifies, resulting subsurface lasts decades.

Language: Английский

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Improved Decadal Predictions of North Atlantic Subpolar Gyre SST in CMIP6

Geophysical Research Letters, Journal Year: 2020, Volume and Issue: 48(3)

Published: Dec. 7, 2020

Abstract Due to its wide‐ranging impacts, predicting decadal variations of sea surface temperature (SST) in the subpolar North Atlantic remains a key goal climate science. Here, we compare representation observed SST since 1960 initialized and uninitialized historical simulations from 5th 6th phases Coupled Model Intercomparison Project (CMIP5/6). Initialized hindcasts CMIP6 explain 88% variance post‐1980 gyre at lead years 5–7 (77% simulations) compared 42% (8%) CMIP5, indicating more prominent role for forcing driving changes than previously thought. Analysis single‐forcing experiments suggests much this correlation is due natural forcing, explaining ∼55% variance. The amplitude underestimated improved by initialization CMIP6, continued value SST.

Language: Английский

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