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Minière A, von Schuckmann K, Sallée JB, Vogt L. Robust acceleration of Earth system heating observed over the past six decades. Sci Rep 2023; 13:22975. [PMID: 38151491 PMCID: PMC10752897 DOI: 10.1038/s41598-023-49353-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 12/07/2023] [Indexed: 12/29/2023] Open
Abstract
Global heating of the Earth system is unequivocal. However, detecting an acceleration of Earth heating has remained elusive to date, despite suggestive evidence of a potential increase in heating rates. In this study, we demonstrate that since 1960, the warming of the world ocean has accelerated at a relatively consistent pace of 0.15 ± 0.05 (W/m2)/decade, while the land, cryosphere, and atmosphere have exhibited an accelerated pace of 0.013 ± 0.003 (W/m2)/decade. This has led to a substantial increase in ocean warming, with a magnitude of 0.91 ± 0.80 W/m2 between the decades 1960-1970 and 2010-2020, which overlies substantial decadal-scale variability in ocean warming of up to 0.6 W/m2. Our findings withstand a wide range of sensitivity analyses and are consistent across different observation-based datasets. The long-term acceleration of Earth warming aligns qualitatively with the rise in CO2 concentrations and the decline in aerosol concentration during the same period, but further investigations are necessary to properly attribute these changes.
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Affiliation(s)
- Audrey Minière
- Université Toulouse III - Paul Sabatier, Toulouse, France.
- Mercator Ocean International, Toulouse, France.
| | | | - Jean-Baptiste Sallée
- LOCEAN-IPSL, Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques, CNRS/IRD/MNHN, Sorbonne Université, Paris, France
| | - Linus Vogt
- LOCEAN-IPSL, Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques, CNRS/IRD/MNHN, Sorbonne Université, Paris, France
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2
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Pöppelmeier F, Jeltsch-Thömmes A, Lippold J, Joos F, Stocker TF. Multi-proxy constraints on Atlantic circulation dynamics since the last ice age. NATURE GEOSCIENCE 2023; 16:349-356. [PMID: 37064010 PMCID: PMC10089918 DOI: 10.1038/s41561-023-01140-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 01/27/2023] [Indexed: 06/19/2023]
Abstract
Uncertainties persist in the understanding of the Atlantic meridional overturning circulation and its response to external perturbations such as freshwater or radiative forcing. Abrupt reduction of the Atlantic circulation is considered a climate tipping point that may have been crossed when Earth's climate was propelled out of the last ice age. However, the evolution of the circulation since the Last Glacial Maximum (22-18 thousand years ago) remains insufficiently constrained due to model and proxy limitations. Here we leverage information from both a compilation of proxy records that track various aspects of the circulation and climate model simulations to constrain the Atlantic circulation over the past 20,000 years. We find a coherent picture of a shallow and weak Atlantic overturning circulation during the Last Glacial Maximum that reconciles apparently conflicting proxy evidence. Model-data comparison of the last deglaciation-starting from this new, multiple constrained glacial state-indicates a muted response during Heinrich Stadial 1 and that water mass geometry did not fully adjust to the strong reduction in overturning circulation during the comparably short Younger Dryas period. This demonstrates that the relationship between freshwater forcing and Atlantic overturning strength is strongly dependent on the climatic and oceanic background state.
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Affiliation(s)
- Frerk Pöppelmeier
- Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
| | - Aurich Jeltsch-Thömmes
- Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
| | - Jörg Lippold
- Institute of Earth Sciences, Heidelberg University, Heidelberg, Germany
| | - Fortunat Joos
- Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
| | - Thomas F Stocker
- Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
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Kaufman DS, Broadman E. Revisiting the Holocene global temperature conundrum. Nature 2023; 614:425-435. [PMID: 36792734 DOI: 10.1038/s41586-022-05536-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 11/07/2022] [Indexed: 02/17/2023]
Abstract
Recent global temperature reconstructions for the current interglacial period (the Holocene, beginning 11,700 years ago) have generated contrasting trends. This Review examines evidence from indicators and drivers of global change, as inferred from proxy records and simulated by climate models, to evaluate whether anthropogenic global warming was preceded by a long-term warming trend or by global cooling. Multimillennial-scale cooling before industrialization requires extra climate forcing and major climate feedbacks that are not well represented in most climate models at present. Conversely, global warming before industrialization challenges proxy-based reconstructions of past climate. The resolution of this conundrum has implications for contextualizing post-industrial warming and for understanding climate sensitivity to several forcings and their attendant feedbacks, including greenhouse gases. From a large variety of available evidence, we find support for a relatively mild millennial-scale global thermal maximum during the mid-Holocene, but more research is needed to firmly resolve the conundrum and to advance our understanding of slow-moving climate variability.
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Affiliation(s)
- Darrell S Kaufman
- School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ, USA.
| | - Ellie Broadman
- School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ, USA
- Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ, USA
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Multiple carbon cycle mechanisms associated with the glaciation of Marine Isotope Stage 4. Nat Commun 2022; 13:5443. [PMID: 36114188 PMCID: PMC9481522 DOI: 10.1038/s41467-022-33166-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 09/02/2022] [Indexed: 12/01/2022] Open
Abstract
Here we use high-precision carbon isotope data (δ13C-CO2) to show atmospheric CO2 during Marine Isotope Stage 4 (MIS 4, ~70.5-59 ka) was controlled by a succession of millennial-scale processes. Enriched δ13C-CO2 during peak glaciation suggests increased ocean carbon storage. Variations in δ13C-CO2 in early MIS 4 suggest multiple processes were active during CO2 drawdown, potentially including decreased land carbon and decreased Southern Ocean air-sea gas exchange superposed on increased ocean carbon storage. CO2 remained low during MIS 4 while δ13C-CO2 fluctuations suggest changes in Southern Ocean and North Atlantic air-sea gas exchange. A 7 ppm increase in CO2 at the onset of Dansgaard-Oeschger event 19 (72.1 ka) and 27 ppm increase in CO2 during late MIS 4 (Heinrich Stadial 6, ~63.5-60 ka) involved additions of isotopically light carbon to the atmosphere. The terrestrial biosphere and Southern Ocean air-sea gas exchange are possible sources, with the latter event also involving decreased ocean carbon storage. Summary for general audience: We used carbon stable isotope data from an Antarctic ice core to evaluate which mechanisms caused changes in atmospheric carbon dioxide 74-59 thousand years ago, including a ~40 ppm decrease at the beginning of the last ice age.
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A global long-term ocean surface daily/0.05° net radiation product from 1983–2020. Sci Data 2022. [PMCID: PMC9198043 DOI: 10.1038/s41597-022-01419-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
AbstractThe all-wave net radiation (Rn) on the ocean surface characterizes the available radiative energy balance and is important to understand the Earth’s climate system. Considering the shortcomings of available ocean surface Rn datasets (e.g., coarse spatial resolutions, discrepancy in accuracy, inconsistency, and short duration), a new long-term global daily Rn product at a spatial resolution of 0.05° from 1983 to 2020, as part of the Global High Resolution Ocean Surface Energy (GHOSE) products suite, was generated in this study by fusing several existing datasets including satellite and reanalysis products based on the comprehensive in situ measurements from 68 globally distributed moored buoy sites. Evaluation against in-situ measurements shows the root mean square difference, mean bias error and correlation coefficient squared of 23.56 Wm−2, 0.88 Wm−2 and 0.878. The global average ocean surface Rn over 1983–2020 is estimated to be 119.71 ± 2.78 Wm−2 with a significant increasing rate of 0.16 Wm−2 per year. GHOSE Rn product can be valuable for oceanic and climatic studies.
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Globally resolved surface temperatures since the Last Glacial Maximum. Nature 2021; 599:239-244. [PMID: 34759364 DOI: 10.1038/s41586-021-03984-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 09/01/2021] [Indexed: 11/08/2022]
Abstract
Climate changes across the past 24,000 years provide key insights into Earth system responses to external forcing. Climate model simulations1,2 and proxy data3-8 have independently allowed for study of this crucial interval; however, they have at times yielded disparate conclusions. Here, we leverage both types of information using paleoclimate data assimilation9,10 to produce the first proxy-constrained, full-field reanalysis of surface temperature change spanning the Last Glacial Maximum to present at 200-year resolution. We demonstrate that temperature variability across the past 24 thousand years was linked to two primary climatic mechanisms: radiative forcing from ice sheets and greenhouse gases; and a superposition of changes in the ocean overturning circulation and seasonal insolation. In contrast with previous proxy-based reconstructions6,7 our results show that global mean temperature has slightly but steadily warmed, by ~0.5 °C, since the early Holocene (around 9 thousand years ago). When compared with recent temperature changes11, our reanalysis indicates that both the rate and magnitude of modern warming are unusual relative to the changes of the past 24 thousand years.
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A New Empirical Estimation Scheme for Daily Net Radiation at the Ocean Surface. REMOTE SENSING 2021. [DOI: 10.3390/rs13204170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ocean surface net radiation (Rn) is significant in research on the Earth’s heat balance systems, air–sea interactions, and other applications. However, there have been few studies on Rn until now. Based on radiative and meteorological measurements collected from 66 globally distributed moored buoys, it was found that Rn was dominated by downward shortwave radiation (Rg↓) when the length ratio of daytime (LRD) was greater than 0.4 but dominated by downward longwave radiation (Rl↓) for the other cases (LRD ≤ 0.4). Therefore, an empirical scheme that includes two conditional models named Case 1 (LRD > 0.4) utilizing Rg↓ as a major input and Case 2 (LRD ≤ 0.4) utilizing Rl↓ as a major input for Rn estimation was successfully developed. After validation against in situ Rn, the performance of the empirical scheme was satisfactory with an overall R2 value of 0.972, an RMSE of 9.768 Wm−2, and a bias of −0.092 Wm−2. Specifically, the accuracies of the two conditional models were also very good, with RMSEs of 9.805 and 2.824 Wm−2 and biases of −0.095 and 0.346 Wm−2 for the Case 1 and Case 2 models, respectively. However, due to the limited number of available samples, the performances of these new models were poor in coastal and high-latitude areas, and the models did not work when the LRD was too small (i.e., LRD < 0.3). Overall, the newly developed empirical scheme for Rn estimation has strong potential to be widely used in practical use because of its simple format and high accuracy.
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20 th century cooling of the deep ocean contributed to delayed acceleration of Earth's energy imbalance. Nat Commun 2021; 12:4604. [PMID: 34326319 PMCID: PMC8322321 DOI: 10.1038/s41467-021-24472-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 06/11/2021] [Indexed: 12/01/2022] Open
Abstract
The historical evolution of Earth’s energy imbalance can be quantified by changes in the global ocean heat content. However, historical reconstructions of ocean heat content often neglect a large volume of the deep ocean, due to sparse observations of ocean temperatures below 2000 m. Here, we provide a global reconstruction of historical changes in full-depth ocean heat content based on interpolated subsurface temperature data using an autoregressive artificial neural network, providing estimates of total ocean warming for the period 1946-2019. We find that cooling of the deep ocean and a small heat gain in the upper ocean led to no robust trend in global ocean heat content from 1960-1990, implying a roughly balanced Earth energy budget within −0.16 to 0.06 W m−2 over most of the latter half of the 20th century. However, the past three decades have seen a rapid acceleration in ocean warming, with the entire ocean warming from top to bottom at a rate of 0.63 ± 0.13 W m−2. These results suggest a delayed onset of a positive Earth energy imbalance relative to previous estimates, although large uncertainties remain. Cooling of the global ocean below 2000 m counteracted some of the warming of the shallow ocean over much of the late 20th century. Here the authors show that this trend has shifted to warming, leading the deep ocean to absorb a meaningful fraction of total ocean heat during the 21st century.
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Gebbie G. Combining Modern and Paleoceanographic Perspectives on Ocean Heat Uptake. ANNUAL REVIEW OF MARINE SCIENCE 2021; 13:255-281. [PMID: 32928022 DOI: 10.1146/annurev-marine-010419-010844] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Monitoring Earth's energy imbalance requires monitoring changes in the heat content of the ocean. Recent observational estimates indicate that ocean heat uptake is accelerating in the twenty-first century. Examination of estimates of ocean heat uptake over the industrial era, the Common Era of the last 2,000 years, and the period since the Last Glacial Maximum, 20,000 years ago, permits a wide perspective on modern-day warming rates. In addition, this longer-term focus illustrates how the dynamics of the deep ocean and the cryosphere were active in the past and are still active today. The large climatic shifts that started with the melting of the great ice sheets have involved significant ocean heat uptake that was sustained over centuries and millennia, and modern-ocean heat content changes are small by comparison.
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Affiliation(s)
- Geoffrey Gebbie
- Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA;
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