Articles | Volume 20, issue 9
https://doi.org/10.5194/cp-20-1989-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-20-1989-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| Highlight paper
| 
12 Sep 2024
Research article | Highlight paper |
| 12 Sep 2024
| 12 Sep 2024
Can we reliably reconstruct the mid-Pliocene Warm Period with sparse data and uncertain models?
James D. Annan
CORRESPONDING AUTHOR
Blue Skies Research Ltd, The Old Chapel, Albert Hill, Settle, BD24 9HE, UK
Julia C. Hargreaves
Blue Skies Research Ltd, The Old Chapel, Albert Hill, Settle, BD24 9HE, UK
Thorsten Mauritsen
Department of Meteorology, Stockholm University, Stockholm, Sweden
Erin McClymont
Department of Geography, Durham University, Durham, DH1 3LE, UK
Sze Ling Ho
Institute of Oceanography, National Taiwan University, 10617 Taipei, Taiwan
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James D. Annan, Julia C. Hargreaves, and Thorsten Mauritsen
Clim. Past, 18, 1883–1896, https://doi.org/10.5194/cp-18-1883-2022, https://doi.org/10.5194/cp-18-1883-2022, 2022
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We have created a new global surface temperature reconstruction of the climate of the Last Glacial Maximum, representing the period 19–23 000 years before the present day. We find that the globally averaged mean temperature was roughly 4.5 °C colder than it was in pre-industrial times, albeit there is significant uncertainty on this value.
Chris M. Brierley, Anni Zhao, Sandy P. Harrison, Pascale Braconnot, Charles J. R. Williams, David J. R. Thornalley, Xiaoxu Shi, Jean-Yves Peterschmitt, Rumi Ohgaito, Darrell S. Kaufman, Masa Kageyama, Julia C. Hargreaves, Michael P. Erb, Julien Emile-Geay, Roberta D'Agostino, Deepak Chandan, Matthieu Carré, Partrick J. Bartlein, Weipeng Zheng, Zhongshi Zhang, Qiong Zhang, Hu Yang, Evgeny M. Volodin, Robert A. Tomas, Cody Routson, W. Richard Peltier, Bette Otto-Bliesner, Polina A. Morozova, Nicholas P. McKay, Gerrit Lohmann, Allegra N. Legrande, Chuncheng Guo, Jian Cao, Esther Brady, James D. Annan, and Ayako Abe-Ouchi
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This paper provides an initial exploration and comparison to climate reconstructions of the new climate model simulations of the mid-Holocene (6000 years ago). These use state-of-the-art models developed for CMIP6 and apply the same experimental set-up. The models capture several key aspects of the climate, but some persistent issues remain.
Martin Renoult, James Douglas Annan, Julia Catherine Hargreaves, Navjit Sagoo, Clare Flynn, Marie-Luise Kapsch, Qiang Li, Gerrit Lohmann, Uwe Mikolajewicz, Rumi Ohgaito, Xiaoxu Shi, Qiong Zhang, and Thorsten Mauritsen
Clim. Past, 16, 1715–1735, https://doi.org/10.5194/cp-16-1715-2020, https://doi.org/10.5194/cp-16-1715-2020, 2020
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Interest in past climates as sources of information for the climate system has grown in recent years. In particular, studies of the warm mid-Pliocene and cold Last Glacial Maximum showed relationships between the tropical surface temperature of the Earth and its sensitivity to an abrupt doubling of atmospheric CO2. In this study, we develop a new and promising statistical method and obtain similar results as previously observed, wherein the sensitivity does not seem to exceed extreme values.
James D. Annan, Julia C. Hargreaves, Thorsten Mauritsen, and Bjorn Stevens
Earth Syst. Dynam., 11, 709–719, https://doi.org/10.5194/esd-11-709-2020, https://doi.org/10.5194/esd-11-709-2020, 2020
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In this paper we explore the potential of variability for constraining the equilibrium response of the climate system to external forcing. We show that the constraint is inherently skewed, with a long tail to high sensitivity, and that while the variability may contain some useful information, it is unlikely to generate a tight constraint.
James D. Annan and Julia C. Hargreaves
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We explore the implicit assumptions that underlie many published probabilistic estimates of the equilibrium climate sensitivity – that is, the amount the climate will warm under a doubling of the atmospheric CO2 concentration. We demonstrate that many such estimates have made assumptions that would be difficult to justify and show how the calculations can be repeated in a more defensible manner. Our results show some significant differences from previous calculations.
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James D. Annan and Julia C. Hargreaves
Earth Syst. Dynam., 8, 211–224, https://doi.org/10.5194/esd-8-211-2017, https://doi.org/10.5194/esd-8-211-2017, 2017
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The concept of independence has been frequently raised in climate science, but has rarely been defined and discussed in a theoretically robust and quantifiable manner. Improved understanding of this topic is critical to better understanding of climate change. In this paper, we introduce a unifying approach based on the statistical definition of independence, and illustrate with simple examples how it can be applied to practical questions.
J. C. Hargreaves and J. D. Annan
Clim. Past, 12, 1591–1599, https://doi.org/10.5194/cp-12-1591-2016, https://doi.org/10.5194/cp-12-1591-2016, 2016
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The mid-Pliocene Warm Period, 3 million years ago, was the most recent interval with high greenhouse gases. By modelling the period with the same models used for future projections, we can link the past and future climates. Here we use data from the mid-Pliocene to produce a tentative result for equilibrium climate sensitivity. We show that there are considerable uncertainties that strongly influence the result, but we are optimistic that these may be reduced in the next few years.
G. A. Schmidt, J. D. Annan, P. J. Bartlein, B. I. Cook, E. Guilyardi, J. C. Hargreaves, S. P. Harrison, M. Kageyama, A. N. LeGrande, B. Konecky, S. Lovejoy, M. E. Mann, V. Masson-Delmotte, C. Risi, D. Thompson, A. Timmermann, L.-B. Tremblay, and P. Yiou
Clim. Past, 10, 221–250, https://doi.org/10.5194/cp-10-221-2014, https://doi.org/10.5194/cp-10-221-2014, 2014
J. C. Hargreaves, J. D. Annan, R. Ohgaito, A. Paul, and A. Abe-Ouchi
Clim. Past, 9, 811–823, https://doi.org/10.5194/cp-9-811-2013, https://doi.org/10.5194/cp-9-811-2013, 2013
E. J. Stone, D. J. Lunt, J. D. Annan, and J. C. Hargreaves
Clim. Past, 9, 621–639, https://doi.org/10.5194/cp-9-621-2013, https://doi.org/10.5194/cp-9-621-2013, 2013
J. D. Annan and J. C. Hargreaves
Clim. Past, 9, 367–376, https://doi.org/10.5194/cp-9-367-2013, https://doi.org/10.5194/cp-9-367-2013, 2013
Thomas Hocking, Linda Megner, Maria Hakuba, and Thorsten Mauritsen
EGUsphere, https://doi.org/10.5194/egusphere-2025-829, https://doi.org/10.5194/egusphere-2025-829, 2025
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The imbalance between the energy the Earth absorbs from the Sun and emits back to space gives rise to climate change, but measuring the small imbalance is challenging. The Earth surface reflects sunlight more in some directions than in others, as with e.g. ocean sunglint. We simulate satellites to investigate how this uneven reflection impacts estimates of the imbalance. We identify orbits that cover all directions well, so that the impact is small.
Mark A. Stevenson, Dominic A. Hodgson, Michael J. Bentley, Darren R. Gröcke, Neil Tunstall, Chris Longley, Alice Graham, and Erin L. McClymont
EGUsphere, https://doi.org/10.5194/egusphere-2025-513, https://doi.org/10.5194/egusphere-2025-513, 2025
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EGUsphere, https://doi.org/10.5194/egusphere-2025-509, https://doi.org/10.5194/egusphere-2025-509, 2025
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The nextGEMS project developed two Earth system models that resolve processes of the order of 10 km, giving more fidelity to the representation of local phenomena, globally. In its fourth cycle, nextGEMS performed simulations with coupled ocean, land, and atmosphere over the 2020–2049 period under the SSP3-7.0 scenario. Here, we provide an overview of nextGEMS, insights into the model development, and the realism of multi-decadal, kilometer-scale simulations.
Louise C. Sime, Rahul Sivankutty, Irene Malmierca-Vallet, Sentia Goursaud Oger, Allegra N. LeGrande, Erin L. McClymont, Agatha de Boer, Alexandre Cauquoin, and Martin Werner
EGUsphere, https://doi.org/10.5194/egusphere-2025-288, https://doi.org/10.5194/egusphere-2025-288, 2025
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We used climate models to study how stable water isotopes in ice cores changed in the Arctic and Antarctica during the warm Last Interglacial (LIG) period. Whilst standard simulations underestimate polar warming, when the effects of ice sheet meltwater from the preceding deglaciation are included, there is a much better match with observations. Findings suggest that previous estimates of LIG Arctic warming were too high. Understanding these past polar changes can help improve future predictions.
Thomas Hocking, Thorsten Mauritsen, and Linda Megner
Atmos. Meas. Tech., 17, 7077–7095, https://doi.org/10.5194/amt-17-7077-2024, https://doi.org/10.5194/amt-17-7077-2024, 2024
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The imbalance between the energy the Earth absorbs from the Sun and the energy the Earth emits back into space gives rise to climate change, but measuring the small imbalance is challenging. We simulate satellites in various orbits to investigate how well they sample the imbalance and find that the best option is to combine at least two satellites that see complementary parts of the Earth and cover the daily and annual cycles. This information is useful when planning future satellite missions.
Alejandro Uribe, Frida A.-M. Bender, and Thorsten Mauritsen
Atmos. Chem. Phys., 24, 13371–13384, https://doi.org/10.5194/acp-24-13371-2024, https://doi.org/10.5194/acp-24-13371-2024, 2024
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Andrea Mosso, Thomas Hocking, and Thorsten Mauritsen
Atmos. Chem. Phys., 24, 12793–12806, https://doi.org/10.5194/acp-24-12793-2024, https://doi.org/10.5194/acp-24-12793-2024, 2024
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Martin Renoult, Navjit Sagoo, Johannes Hörner, and Thorsten Mauritsen
EGUsphere, https://doi.org/10.5194/egusphere-2024-2981, https://doi.org/10.5194/egusphere-2024-2981, 2024
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Antoine Hermant, Linnea Huusko, and Thorsten Mauritsen
Atmos. Chem. Phys., 24, 10707–10715, https://doi.org/10.5194/acp-24-10707-2024, https://doi.org/10.5194/acp-24-10707-2024, 2024
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Aerosol particles, from natural and human sources, have a cooling effect on the climate, partially offsetting global warming. They do this through direct (sunlight reflection) and indirect (cloud property alteration) mechanisms. Using a global climate model, we found that, despite declining emissions, the direct effect of human aerosols has increased while the indirect effect has decreased, which is attributed to the shift in emissions from North America and Europe to Southeast Asia.
Raphael Grodofzig, Martin Renoult, and Thorsten Mauritsen
Earth Syst. Dynam., 15, 913–927, https://doi.org/10.5194/esd-15-913-2024, https://doi.org/10.5194/esd-15-913-2024, 2024
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We investigate whether the Amazon rainforest has lost substantial resilience since 1990. This assertion is based on trends in the observational record of vegetation density. We calculate the same metrics in a large number of climate model simulations and find that several models behave indistinguishably from the observations, suggesting that the observed trend could be caused by internal variability and that the cause of the ongoing rapid loss of Amazon rainforest is not mainly global warming.
Jack T. R. Wilkin, Sev Kender, Rowan Dejardin, Claire S. Allen, Victoria L. Peck, George E. A. Swann, Erin L. McClymont, James D. Scourse, Kate Littler, and Melanie J. Leng
J. Micropalaeontol., 43, 165–186, https://doi.org/10.5194/jm-43-165-2024, https://doi.org/10.5194/jm-43-165-2024, 2024
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The sub-Antarctic island of South Georgia has a dynamic glacial history and is sensitive to climate change. Using benthic foraminifera and various geochemical proxies, we reconstruct inner–middle shelf productivity and infer glacial evolution since the late deglacial, identifying new mid–late-Holocene glacial readvances. Fursenkoina fusiformis acts as a good proxy for productivity.
Lauren E. Burton, Alan M. Haywood, Julia C. Tindall, Aisling M. Dolan, Daniel J. Hill, Erin L. McClymont, Sze Ling Ho, and Heather L. Ford
Clim. Past, 20, 1177–1194, https://doi.org/10.5194/cp-20-1177-2024, https://doi.org/10.5194/cp-20-1177-2024, 2024
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The Pliocene (~ 3 million years ago) is of interest because its warm climate is similar to projections of the future. We explore the role of atmospheric carbon dioxide in forcing sea surface temperature during the Pliocene by combining climate model outputs with palaeoclimate proxy data. We investigate whether this role changes seasonally and also use our data to suggest a new estimate of Pliocene climate sensitivity. More data are needed to further explore the results presented.
Tobias Roylands, Robert G. Hilton, Erin L. McClymont, Mark H. Garnett, Guillaume Soulet, Sébastien Klotz, Mathis Degler, Felipe Napoleoni, and Caroline Le Bouteiller
Earth Surf. Dynam., 12, 271–299, https://doi.org/10.5194/esurf-12-271-2024, https://doi.org/10.5194/esurf-12-271-2024, 2024
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Chemical weathering of sedimentary rocks can release carbon dioxide and consume oxygen. We present a new field-based method to measure the exchange of these gases in real time, which allows us to directly compare the amount of reactants and products. By studying two sites with different rock types, we show that the chemical composition is an important factor in driving the weathering reactions. Locally, the carbon dioxide release changes alongside temperature and precipitation.
Clare Marie Flynn, Linnea Huusko, Angshuman Modak, and Thorsten Mauritsen
Atmos. Chem. Phys., 23, 15121–15133, https://doi.org/10.5194/acp-23-15121-2023, https://doi.org/10.5194/acp-23-15121-2023, 2023
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The latest-generation climate models show surprisingly cold mid-20th century global-mean temperatures, often despite exhibiting more realistic late 20th/early 21st century temperatures. A too-strong aerosol forcing in many models was thought to the be primary cause of these too-cold mid-century temperatures, but this was found to only be a partial explanation. This also partly undermines the hope to construct a strong relationship between the mid-century temperatures and aerosol forcing.
Anna Hauge Braaten, Kim A. Jakob, Sze Ling Ho, Oliver Friedrich, Eirik Vinje Galaasen, Stijn De Schepper, Paul A. Wilson, and Anna Nele Meckler
Clim. Past, 19, 2109–2125, https://doi.org/10.5194/cp-19-2109-2023, https://doi.org/10.5194/cp-19-2109-2023, 2023
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In the context of understanding current global warming, the middle Pliocene (3.3–3.0 million years ago) is an important interval in Earth's history because atmospheric carbon dioxide concentrations were similar to levels today. We have reconstructed deep-sea temperatures at two different locations for this period, and find that a very different mode of ocean circulation or mixing existed, with important implications for how heat was transported in the deep ocean.
Sushant Das, Frida Bender, and Thorsten Mauritsen
EGUsphere, https://doi.org/10.5194/egusphere-2023-1605, https://doi.org/10.5194/egusphere-2023-1605, 2023
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Quantifying global and Indian precipitation responses to anthropogenic aerosol and CO2 forcings using multiple models is needed for reducing climate uncertainty. The response to global warming from CO2 increases precipitation both globally and over India, whereas the cooling response to sulfate aerosol leads to a reduction in precipitation in both cases. An opposite response to black carbon is noted i.e., a global decrease but an increase of precipitation over India implying changes in dynamics.
Georgia R. Grant, Jonny H. T. Williams, Sebastian Naeher, Osamu Seki, Erin L. McClymont, Molly O. Patterson, Alan M. Haywood, Erik Behrens, Masanobu Yamamoto, and Katelyn Johnson
Clim. Past, 19, 1359–1381, https://doi.org/10.5194/cp-19-1359-2023, https://doi.org/10.5194/cp-19-1359-2023, 2023
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Regional warming will differ from global warming, and climate models perform poorly in the Southern Ocean. We reconstruct sea surface temperatures in the south-west Pacific during the mid-Pliocene, a time 3 million years ago that represents the long-term outcomes of 3 °C warming, which is expected for the future. Comparing these results to climate model simulations, we show that the south-west Pacific region will warm by 1 °C above the global average if atmospheric CO2 remains above 350 ppm.
Angshuman Modak and Thorsten Mauritsen
Atmos. Chem. Phys., 23, 7535–7549, https://doi.org/10.5194/acp-23-7535-2023, https://doi.org/10.5194/acp-23-7535-2023, 2023
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We provide an improved estimate of equilibrium climate sensitivity (ECS) constrained based on the instrumental temperature record including the corrections for the pattern effect. The improved estimate factors in the uncertainty caused by the underlying sea-surface temperature datasets used in the estimates of pattern effect. This together with the inter-model spread lifts the corresponding IPCC AR6 estimate to 3.2 K [1.8 to 11.0], which is lower and better constrained than in past studies.
Bjørg Risebrobakken, Mari F. Jensen, Helene R. Langehaug, Tor Eldevik, Anne Britt Sandø, Camille Li, Andreas Born, Erin Louise McClymont, Ulrich Salzmann, and Stijn De Schepper
Clim. Past, 19, 1101–1123, https://doi.org/10.5194/cp-19-1101-2023, https://doi.org/10.5194/cp-19-1101-2023, 2023
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In the observational period, spatially coherent sea surface temperatures characterize the northern North Atlantic at multidecadal timescales. We show that spatially non-coherent temperature patterns are seen both in further projections and a past warm climate period with a CO2 level comparable to the future low-emission scenario. Buoyancy forcing is shown to be important for northern North Atlantic temperature patterns.
James A. Smith, Louise Callard, Michael J. Bentley, Stewart S. R. Jamieson, Maria Luisa Sánchez-Montes, Timothy P. Lane, Jeremy M. Lloyd, Erin L. McClymont, Christopher M. Darvill, Brice R. Rea, Colm O'Cofaigh, Pauline Gulliver, Werner Ehrmann, Richard S. Jones, and David H. Roberts
The Cryosphere, 17, 1247–1270, https://doi.org/10.5194/tc-17-1247-2023, https://doi.org/10.5194/tc-17-1247-2023, 2023
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The Greenland Ice Sheet is melting at an accelerating rate. To understand the significance of these changes we reconstruct the history of one of its fringing ice shelves, known as 79° N ice shelf. We show that the ice shelf disappeared 8500 years ago, following a period of enhanced warming. An important implication of our study is that 79° N ice shelf is susceptible to collapse when atmospheric and ocean temperatures are ~2°C warmer than present, which could occur by the middle of this century.
Martin Renoult, Navjit Sagoo, Jiang Zhu, and Thorsten Mauritsen
Clim. Past, 19, 323–356, https://doi.org/10.5194/cp-19-323-2023, https://doi.org/10.5194/cp-19-323-2023, 2023
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The relationship between the Last Glacial Maximum and the sensitivity of climate models to a doubling of CO2 can be used to estimate the true sensitivity of the Earth. However, this relationship has varied in successive model generations. In this study, we assess multiple processes at the Last Glacial Maximum which weaken this relationship. For example, how models respond to the presence of ice sheets is a large contributor of uncertainty.
Cathy Hohenegger, Peter Korn, Leonidas Linardakis, René Redler, Reiner Schnur, Panagiotis Adamidis, Jiawei Bao, Swantje Bastin, Milad Behravesh, Martin Bergemann, Joachim Biercamp, Hendryk Bockelmann, Renate Brokopf, Nils Brüggemann, Lucas Casaroli, Fatemeh Chegini, George Datseris, Monika Esch, Geet George, Marco Giorgetta, Oliver Gutjahr, Helmuth Haak, Moritz Hanke, Tatiana Ilyina, Thomas Jahns, Johann Jungclaus, Marcel Kern, Daniel Klocke, Lukas Kluft, Tobias Kölling, Luis Kornblueh, Sergey Kosukhin, Clarissa Kroll, Junhong Lee, Thorsten Mauritsen, Carolin Mehlmann, Theresa Mieslinger, Ann Kristin Naumann, Laura Paccini, Angel Peinado, Divya Sri Praturi, Dian Putrasahan, Sebastian Rast, Thomas Riddick, Niklas Roeber, Hauke Schmidt, Uwe Schulzweida, Florian Schütte, Hans Segura, Radomyra Shevchenko, Vikram Singh, Mia Specht, Claudia Christine Stephan, Jin-Song von Storch, Raphaela Vogel, Christian Wengel, Marius Winkler, Florian Ziemen, Jochem Marotzke, and Bjorn Stevens
Geosci. Model Dev., 16, 779–811, https://doi.org/10.5194/gmd-16-779-2023, https://doi.org/10.5194/gmd-16-779-2023, 2023
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Models of the Earth system used to understand climate and predict its change typically employ a grid spacing of about 100 km. Yet, many atmospheric and oceanic processes occur on much smaller scales. In this study, we present a new model configuration designed for the simulation of the components of the Earth system and their interactions at kilometer and smaller scales, allowing an explicit representation of the main drivers of the flow of energy and matter by solving the underlying equations.
James D. Annan, Julia C. Hargreaves, and Thorsten Mauritsen
Clim. Past, 18, 1883–1896, https://doi.org/10.5194/cp-18-1883-2022, https://doi.org/10.5194/cp-18-1883-2022, 2022
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We have created a new global surface temperature reconstruction of the climate of the Last Glacial Maximum, representing the period 19–23 000 years before the present day. We find that the globally averaged mean temperature was roughly 4.5 °C colder than it was in pre-industrial times, albeit there is significant uncertainty on this value.
Raúl Tapia, Sze Ling Ho, Hui-Yu Wang, Jeroen Groeneveld, and Mahyar Mohtadi
Biogeosciences, 19, 3185–3208, https://doi.org/10.5194/bg-19-3185-2022, https://doi.org/10.5194/bg-19-3185-2022, 2022
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We report census counts of planktic foraminifera in depth-stratified plankton net samples off Indonesia. Our results show that the vertical distribution of foraminifera species routinely used in paleoceanographic reconstructions varies in hydrographically distinct regions, likely in response to food availability. Consequently, the thermal gradient based on mixed layer and thermocline dwellers also differs for these regions, suggesting potential implications for paleoceanographic reconstructions.
Erin L. McClymont, Michael J. Bentley, Dominic A. Hodgson, Charlotte L. Spencer-Jones, Thomas Wardley, Martin D. West, Ian W. Croudace, Sonja Berg, Darren R. Gröcke, Gerhard Kuhn, Stewart S. R. Jamieson, Louise Sime, and Richard A. Phillips
Clim. Past, 18, 381–403, https://doi.org/10.5194/cp-18-381-2022, https://doi.org/10.5194/cp-18-381-2022, 2022
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Sea ice is important for our climate system and for the unique ecosystems it supports. We present a novel way to understand past Antarctic sea-ice ecosystems: using the regurgitated stomach contents of snow petrels, which nest above the ice sheet but feed in the sea ice. During a time when sea ice was more extensive than today (24 000–30 000 years ago), we show that snow petrel diet had varying contributions of fish and krill, which we interpret to show changing sea-ice distribution.
Charlotte L. Spencer-Jones, Erin L. McClymont, Nicole J. Bale, Ellen C. Hopmans, Stefan Schouten, Juliane Müller, E. Povl Abrahamsen, Claire Allen, Torsten Bickert, Claus-Dieter Hillenbrand, Elaine Mawbey, Victoria Peck, Aleksandra Svalova, and James A. Smith
Biogeosciences, 18, 3485–3504, https://doi.org/10.5194/bg-18-3485-2021, https://doi.org/10.5194/bg-18-3485-2021, 2021
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Long-term ocean temperature records are needed to fully understand the impact of West Antarctic Ice Sheet collapse. Glycerol dialkyl glycerol tetraethers (GDGTs) are powerful tools for reconstructing ocean temperature but can be difficult to apply to the Southern Ocean. Our results show active GDGT synthesis in relatively warm depths of the ocean. This research improves the application of GDGT palaeoceanographic proxies in the Southern Ocean.
Jule Radtke, Thorsten Mauritsen, and Cathy Hohenegger
Atmos. Chem. Phys., 21, 3275–3288, https://doi.org/10.5194/acp-21-3275-2021, https://doi.org/10.5194/acp-21-3275-2021, 2021
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Shallow trade wind clouds are a key source of uncertainty to projections of the Earth's changing climate. We perform high-resolution simulations of trade cumulus and investigate how the representation and climate feedback of these clouds depend on the specific grid spacing. We find that the cloud feedback is positive when simulated with kilometre but near zero when simulated with hectometre grid spacing. These findings suggest that storm-resolving models may exaggerate the trade cloud feedback.
Chris M. Brierley, Anni Zhao, Sandy P. Harrison, Pascale Braconnot, Charles J. R. Williams, David J. R. Thornalley, Xiaoxu Shi, Jean-Yves Peterschmitt, Rumi Ohgaito, Darrell S. Kaufman, Masa Kageyama, Julia C. Hargreaves, Michael P. Erb, Julien Emile-Geay, Roberta D'Agostino, Deepak Chandan, Matthieu Carré, Partrick J. Bartlein, Weipeng Zheng, Zhongshi Zhang, Qiong Zhang, Hu Yang, Evgeny M. Volodin, Robert A. Tomas, Cody Routson, W. Richard Peltier, Bette Otto-Bliesner, Polina A. Morozova, Nicholas P. McKay, Gerrit Lohmann, Allegra N. Legrande, Chuncheng Guo, Jian Cao, Esther Brady, James D. Annan, and Ayako Abe-Ouchi
Clim. Past, 16, 1847–1872, https://doi.org/10.5194/cp-16-1847-2020, https://doi.org/10.5194/cp-16-1847-2020, 2020
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This paper provides an initial exploration and comparison to climate reconstructions of the new climate model simulations of the mid-Holocene (6000 years ago). These use state-of-the-art models developed for CMIP6 and apply the same experimental set-up. The models capture several key aspects of the climate, but some persistent issues remain.
Martin Renoult, James Douglas Annan, Julia Catherine Hargreaves, Navjit Sagoo, Clare Flynn, Marie-Luise Kapsch, Qiang Li, Gerrit Lohmann, Uwe Mikolajewicz, Rumi Ohgaito, Xiaoxu Shi, Qiong Zhang, and Thorsten Mauritsen
Clim. Past, 16, 1715–1735, https://doi.org/10.5194/cp-16-1715-2020, https://doi.org/10.5194/cp-16-1715-2020, 2020
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Interest in past climates as sources of information for the climate system has grown in recent years. In particular, studies of the warm mid-Pliocene and cold Last Glacial Maximum showed relationships between the tropical surface temperature of the Earth and its sensitivity to an abrupt doubling of atmospheric CO2. In this study, we develop a new and promising statistical method and obtain similar results as previously observed, wherein the sensitivity does not seem to exceed extreme values.
Erin L. McClymont, Heather L. Ford, Sze Ling Ho, Julia C. Tindall, Alan M. Haywood, Montserrat Alonso-Garcia, Ian Bailey, Melissa A. Berke, Kate Littler, Molly O. Patterson, Benjamin Petrick, Francien Peterse, A. Christina Ravelo, Bjørg Risebrobakken, Stijn De Schepper, George E. A. Swann, Kaustubh Thirumalai, Jessica E. Tierney, Carolien van der Weijst, Sarah White, Ayako Abe-Ouchi, Michiel L. J. Baatsen, Esther C. Brady, Wing-Le Chan, Deepak Chandan, Ran Feng, Chuncheng Guo, Anna S. von der Heydt, Stephen Hunter, Xiangyi Li, Gerrit Lohmann, Kerim H. Nisancioglu, Bette L. Otto-Bliesner, W. Richard Peltier, Christian Stepanek, and Zhongshi Zhang
Clim. Past, 16, 1599–1615, https://doi.org/10.5194/cp-16-1599-2020, https://doi.org/10.5194/cp-16-1599-2020, 2020
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We examine the sea-surface temperature response to an interval of climate ~ 3.2 million years ago, when CO2 concentrations were similar to today and the near future. Our geological data and climate models show that global mean sea-surface temperatures were 2.3 to 3.2 ºC warmer than pre-industrial climate, that the mid-latitudes and high latitudes warmed more than the tropics, and that the warming was particularly enhanced in the North Atlantic Ocean.
James D. Annan, Julia C. Hargreaves, Thorsten Mauritsen, and Bjorn Stevens
Earth Syst. Dynam., 11, 709–719, https://doi.org/10.5194/esd-11-709-2020, https://doi.org/10.5194/esd-11-709-2020, 2020
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In this paper we explore the potential of variability for constraining the equilibrium response of the climate system to external forcing. We show that the constraint is inherently skewed, with a long tail to high sensitivity, and that while the variability may contain some useful information, it is unlikely to generate a tight constraint.
Clare Marie Flynn and Thorsten Mauritsen
Atmos. Chem. Phys., 20, 7829–7842, https://doi.org/10.5194/acp-20-7829-2020, https://doi.org/10.5194/acp-20-7829-2020, 2020
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The range of climate sensitivity of models participating in CMIP6 has increased relative to models participating in CMIP5 due to decreases in the total feedback parameter. This is caused by increases in the shortwave all-sky and clear-sky feedbacks, particularly over the Southern Ocean. These shifts between CMIP6 and CMIP5 did not arise by chance. Both CMIP5 and CMIP6 models are found to exhibit aerosol forcing that is too strong, causing too much cooling relative to observations.
James D. Annan and Julia C. Hargreaves
Earth Syst. Dynam., 11, 347–356, https://doi.org/10.5194/esd-11-347-2020, https://doi.org/10.5194/esd-11-347-2020, 2020
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We explore the implicit assumptions that underlie many published probabilistic estimates of the equilibrium climate sensitivity – that is, the amount the climate will warm under a doubling of the atmospheric CO2 concentration. We demonstrate that many such estimates have made assumptions that would be difficult to justify and show how the calculations can be repeated in a more defensible manner. Our results show some significant differences from previous calculations.
Maria Luisa Sánchez-Montes, Erin L. McClymont, Jeremy M. Lloyd, Juliane Müller, Ellen A. Cowan, and Coralie Zorzi
Clim. Past, 16, 299–313, https://doi.org/10.5194/cp-16-299-2020, https://doi.org/10.5194/cp-16-299-2020, 2020
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In this paper, we present new climate reconstructions in SW Alaska from recovered marine sediments in the Gulf of Alaska. We find that glaciers reached the Gulf of Alaska during a cooling climate 2.9 million years ago, and after that the Cordilleran Ice Sheet continued growing during a global drop in atmospheric CO2 levels. Cordilleran Ice Sheet growth could have been supported by an increase in heat supply to the SW Alaska and warm ocean evaporation–mountain precipitation mechanisms.
Daniel T. McCoy, Paul R. Field, Gregory S. Elsaesser, Alejandro Bodas-Salcedo, Brian H. Kahn, Mark D. Zelinka, Chihiro Kodama, Thorsten Mauritsen, Benoit Vanniere, Malcolm Roberts, Pier L. Vidale, David Saint-Martin, Aurore Voldoire, Rein Haarsma, Adrian Hill, Ben Shipway, and Jonathan Wilkinson
Atmos. Chem. Phys., 19, 1147–1172, https://doi.org/10.5194/acp-19-1147-2019, https://doi.org/10.5194/acp-19-1147-2019, 2019
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The largest single source of uncertainty in the climate sensitivity predicted by global climate models is how much low-altitude clouds change as the climate warms. Models predict that the amount of liquid within and the brightness of low-altitude clouds increase in the extratropics with warming. We show that increased fluxes of moisture into extratropical storms in the midlatitudes explain the majority of the observed trend and the modeled increase in liquid water within these storms.
Andrew E. Dessler, Thorsten Mauritsen, and Bjorn Stevens
Atmos. Chem. Phys., 18, 5147–5155, https://doi.org/10.5194/acp-18-5147-2018, https://doi.org/10.5194/acp-18-5147-2018, 2018
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One of the most important parameters in climate science is the equilibrium climate sensitivity (ECS). Estimates of this quantity based on 20th-century observations suggest low values of ECS (below 2 °C). We show that these calculations may be significantly in error. Together with other recent work on this problem, it seems probable that the ECS is larger than suggested by the 20th-century observations.
Tomoo Ogura, Hideo Shiogama, Masahiro Watanabe, Masakazu Yoshimori, Tokuta Yokohata, James D. Annan, Julia C. Hargreaves, Naoto Ushigami, Kazuya Hirota, Yu Someya, Youichi Kamae, Hiroaki Tatebe, and Masahide Kimoto
Geosci. Model Dev., 10, 4647–4664, https://doi.org/10.5194/gmd-10-4647-2017, https://doi.org/10.5194/gmd-10-4647-2017, 2017
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Present-day climate simulated by coupled ocean atmosphere models exhibits significant biases in top-of-atmosphere radiation and clouds. This study shows that only limited part of the biases can be removed by parameter tuning in a climate model. The results underline the importance of improving parameterizations in climate models based on cloud process studies. Implementing a shallow convection parameterization is suggested as a potential measure to alleviate the biases.
Paul E. Bachem, Bjørg Risebrobakken, Stijn De Schepper, and Erin L. McClymont
Clim. Past, 13, 1153–1168, https://doi.org/10.5194/cp-13-1153-2017, https://doi.org/10.5194/cp-13-1153-2017, 2017
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We present a high-resolution multi-proxy study of the Norwegian Sea, covering the 5.33 to 3.14 Ma time window within the Pliocene. We show that large-scale climate transitions took place during this warmer than modern time, most likely in response to ocean gateway transformations. Strong warming at 4.0 Ma in the Norwegian Sea, when regions closer to Greenland cooled, indicate that increased northward ocean heat transport may be compatible with expanding glaciation and Arctic sea ice growth.
James D. Annan and Julia C. Hargreaves
Earth Syst. Dynam., 8, 211–224, https://doi.org/10.5194/esd-8-211-2017, https://doi.org/10.5194/esd-8-211-2017, 2017
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The concept of independence has been frequently raised in climate science, but has rarely been defined and discussed in a theoretically robust and quantifiable manner. Improved understanding of this topic is critical to better understanding of climate change. In this paper, we introduce a unifying approach based on the statistical definition of independence, and illustrate with simple examples how it can be applied to practical questions.
Bjorn Stevens, Stephanie Fiedler, Stefan Kinne, Karsten Peters, Sebastian Rast, Jobst Müsse, Steven J. Smith, and Thorsten Mauritsen
Geosci. Model Dev., 10, 433–452, https://doi.org/10.5194/gmd-10-433-2017, https://doi.org/10.5194/gmd-10-433-2017, 2017
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A simple analytic description of aerosol optical properties and their main effects on clouds is developed and described. The analytic description is easy to use and easy to modify and should aid experimentation to help understand how aerosol radiative and cloud interactions effect climate and circulation. The climatology is recommended for adoption by models participating in the sixth phase of the Coupled Model Intercomparison Project.
J. C. Hargreaves and J. D. Annan
Clim. Past, 12, 1591–1599, https://doi.org/10.5194/cp-12-1591-2016, https://doi.org/10.5194/cp-12-1591-2016, 2016
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The mid-Pliocene Warm Period, 3 million years ago, was the most recent interval with high greenhouse gases. By modelling the period with the same models used for future projections, we can link the past and future climates. Here we use data from the mid-Pliocene to produce a tentative result for equilibrium climate sensitivity. We show that there are considerable uncertainties that strongly influence the result, but we are optimistic that these may be reduced in the next few years.
M. Tjernström, C. Leck, C. E. Birch, J. W. Bottenheim, B. J. Brooks, I. M. Brooks, L. Bäcklin, R. Y.-W. Chang, G. de Leeuw, L. Di Liberto, S. de la Rosa, E. Granath, M. Graus, A. Hansel, J. Heintzenberg, A. Held, A. Hind, P. Johnston, J. Knulst, M. Martin, P. A. Matrai, T. Mauritsen, M. Müller, S. J. Norris, M. V. Orellana, D. A. Orsini, J. Paatero, P. O. G. Persson, Q. Gao, C. Rauschenberg, Z. Ristovski, J. Sedlar, M. D. Shupe, B. Sierau, A. Sirevaag, S. Sjogren, O. Stetzer, E. Swietlicki, M. Szczodrak, P. Vaattovaara, N. Wahlberg, M. Westberg, and C. R. Wheeler
Atmos. Chem. Phys., 14, 2823–2869, https://doi.org/10.5194/acp-14-2823-2014, https://doi.org/10.5194/acp-14-2823-2014, 2014
G. A. Schmidt, J. D. Annan, P. J. Bartlein, B. I. Cook, E. Guilyardi, J. C. Hargreaves, S. P. Harrison, M. Kageyama, A. N. LeGrande, B. Konecky, S. Lovejoy, M. E. Mann, V. Masson-Delmotte, C. Risi, D. Thompson, A. Timmermann, L.-B. Tremblay, and P. Yiou
Clim. Past, 10, 221–250, https://doi.org/10.5194/cp-10-221-2014, https://doi.org/10.5194/cp-10-221-2014, 2014
M. D. Shupe, P. O. G. Persson, I. M. Brooks, M. Tjernström, J. Sedlar, T. Mauritsen, S. Sjogren, and C. Leck
Atmos. Chem. Phys., 13, 9379–9399, https://doi.org/10.5194/acp-13-9379-2013, https://doi.org/10.5194/acp-13-9379-2013, 2013
J. C. Hargreaves, J. D. Annan, R. Ohgaito, A. Paul, and A. Abe-Ouchi
Clim. Past, 9, 811–823, https://doi.org/10.5194/cp-9-811-2013, https://doi.org/10.5194/cp-9-811-2013, 2013
E. J. Stone, D. J. Lunt, J. D. Annan, and J. C. Hargreaves
Clim. Past, 9, 621–639, https://doi.org/10.5194/cp-9-621-2013, https://doi.org/10.5194/cp-9-621-2013, 2013
J. D. Annan and J. C. Hargreaves
Clim. Past, 9, 367–376, https://doi.org/10.5194/cp-9-367-2013, https://doi.org/10.5194/cp-9-367-2013, 2013
Related subject area
Subject: Proxy Use-Development-Validation | Archive: Marine Archives | Timescale: Cenozoic
Southern Ocean control on atmospheric CO2 changes across late Pliocene Marine Isotope Stage M2
A clumped isotope calibration of coccoliths at well-constrained culture temperatures for marine temperature reconstructions
Paleocene–Eocene age glendonites from the Mid-Norwegian Margin – indicators of cold snaps in the hothouse?
Assessing environmental change associated with early Eocene hyperthermals in the Atlantic Coastal Plain, USA
Technical note: A new online tool for δ18O–temperature conversions
A 15-million-year surface- and subsurface-integrated TEX86 temperature record from the eastern equatorial Atlantic
Sclerochronological evidence of pronounced seasonality from the late Pliocene of the southern North Sea basin and its implications
Pliocene evolution of the tropical Atlantic thermocline depth
Maastrichtian–Rupelian paleoclimates in the southwest Pacific – a critical re-evaluation of biomarker paleothermometry and dinoflagellate cyst paleoecology at Ocean Drilling Program Site 1172
Southern Ocean bottom-water cooling and ice sheet expansion during the middle Miocene climate transition
Rapid and sustained environmental responses to global warming: the Paleocene–Eocene Thermal Maximum in the eastern North Sea
Atmospheric carbon dioxide variations across the middle Miocene climate transition
OPTiMAL: a new machine learning approach for GDGT-based palaeothermometry
Technical note: A new automated radiolarian image acquisition, stacking, processing, segmentation and identification workflow
Late Paleocene–early Eocene Arctic Ocean sea surface temperatures: reassessing biomarker paleothermometry at Lomonosov Ridge
Surface-circulation change in the southwest Pacific Ocean across the Middle Eocene Climatic Optimum: inferences from dinoflagellate cysts and biomarker paleothermometry
A new age model for the Pliocene of the southern North Sea basin: a multi-proxy climate reconstruction
Joint inversion of proxy system models to reconstruct paleoenvironmental time series from heterogeneous data
Mercury anomalies across the Palaeocene–Eocene Thermal Maximum
Reinforcing the North Atlantic backbone: revision and extension of the composite splice at ODP Site 982
Highly variable Pliocene sea surface conditions in the Norwegian Sea
The PRISM4 (mid-Piacenzian) paleoenvironmental reconstruction
Revisiting carbonate chemistry controls on planktic foraminifera Mg / Ca: implications for sea surface temperature and hydrology shifts over the Paleocene–Eocene Thermal Maximum and Eocene–Oligocene transition
The Paleocene–Eocene Thermal Maximum at DSDP Site 277, Campbell Plateau, southern Pacific Ocean
The bivalve Glycymeris planicostalis as a high-resolution paleoclimate archive for the Rupelian (Early Oligocene) of central Europe
Pliocene diatom and sponge spicule oxygen isotope ratios from the Bering Sea: isotopic offsets and future directions
Re-evaluation of the age model for North Atlantic Ocean Site 982 – arguments for a return to the original chronology
Exploring the controls on element ratios in middle Eocene samples of the benthic foraminifera Oridorsalis umbonatus
Application of Fourier Transform Infrared Spectroscopy (FTIR) for assessing biogenic silica sample purity in geochemical analyses and palaeoenvironmental research
Suning Hou, Leonie Toebrock, Mart van der Linden, Fleur Rothstegge, Martin Ziegler, Lucas J. Lourens, and Peter K. Bijl
Clim. Past, 21, 79–93, https://doi.org/10.5194/cp-21-79-2025, https://doi.org/10.5194/cp-21-79-2025, 2025
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Based on dinoflagellate cyst assemblages and sea surface temperature records west of offshore Tasmania, we find a northward migration and freshening of the subtropical front, not at the M2 glacial maximum but at its deglaciation phase. This oceanographic change aligns well with trends in pCO2. We propose that iceberg discharge from the M2 deglaciation freshened the subtropical front, which together with the other oceanographic changes affected atmosphere–ocean CO2 exchange in the Southern Ocean.
Alexander J. Clark, Ismael Torres-Romero, Madalina Jaggi, Stefano M. Bernasconi, and Heather M. Stoll
Clim. Past, 20, 2081–2101, https://doi.org/10.5194/cp-20-2081-2024, https://doi.org/10.5194/cp-20-2081-2024, 2024
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Coccoliths are abundant in sediments across the world’s oceans, yet it is difficult to apply traditional carbon or oxygen isotope methodologies for temperature reconstructions. We show that our coccolith clumped isotope temperature calibration with well-constrained temperatures systematically differs from inorganic carbonate calibrations. We suggest the use of our well-constrained calibration for future coccolith carbonate temperature reconstructions.
Madeleine L. Vickers, Morgan T. Jones, Jack Longman, David Evans, Clemens V. Ullmann, Ella Wulfsberg Stokke, Martin Vickers, Joost Frieling, Dustin T. Harper, Vincent J. Clementi, and IODP Expedition 396 Scientists
Clim. Past, 20, 1–23, https://doi.org/10.5194/cp-20-1-2024, https://doi.org/10.5194/cp-20-1-2024, 2024
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The discovery of cold-water glendonite pseudomorphs in sediments deposited during the hottest part of the Cenozoic poses an apparent climate paradox. This study examines their occurrence, association with volcanic sediments, and speculates on the timing and extent of cooling, fitting this with current understanding of global climate during this period. We propose that volcanic activity was key to both physical and chemical conditions that enabled the formation of glendonites in these sediments.
William Rush, Jean Self-Trail, Yang Zhang, Appy Sluijs, Henk Brinkhuis, James Zachos, James G. Ogg, and Marci Robinson
Clim. Past, 19, 1677–1698, https://doi.org/10.5194/cp-19-1677-2023, https://doi.org/10.5194/cp-19-1677-2023, 2023
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The Eocene contains several brief warming periods referred to as hyperthermals. Studying these events and how they varied between locations can help provide insight into our future warmer world. This study provides a characterization of two of these events in the mid-Atlantic region of the USA. The records of climate that we measured demonstrate significant changes during this time period, but the type and timing of these changes highlight the complexity of climatic changes.
Daniel E. Gaskell and Pincelli M. Hull
Clim. Past, 19, 1265–1274, https://doi.org/10.5194/cp-19-1265-2023, https://doi.org/10.5194/cp-19-1265-2023, 2023
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One of the most common ways of reconstructing temperatures in the geologic past is by analyzing oxygen isotope ratios in fossil shells. However, converting these data to temperatures can be a technically complicated task. Here, we present a new online tool that automates this task.
Carolien M. H. van der Weijst, Koen J. van der Laan, Francien Peterse, Gert-Jan Reichart, Francesca Sangiorgi, Stefan Schouten, Tjerk J. T. Veenstra, and Appy Sluijs
Clim. Past, 18, 1947–1962, https://doi.org/10.5194/cp-18-1947-2022, https://doi.org/10.5194/cp-18-1947-2022, 2022
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The TEX86 proxy is often used by paleoceanographers to reconstruct past sea-surface temperatures. However, the origin of the TEX86 signal in marine sediments has been debated since the proxy was first proposed. In our paper, we show that TEX86 carries a mixed sea-surface and subsurface temperature signal and should be calibrated accordingly. Using our 15-million-year record, we subsequently show how a TEX86 subsurface temperature record can be used to inform us on past sea-surface temperatures.
Andrew L. A. Johnson, Annemarie M. Valentine, Bernd R. Schöne, Melanie J. Leng, and Stijn Goolaerts
Clim. Past, 18, 1203–1229, https://doi.org/10.5194/cp-18-1203-2022, https://doi.org/10.5194/cp-18-1203-2022, 2022
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Determining seasonal temperatures demands proxies that record the highest and lowest temperatures over the annual cycle. Many record neither, but oxygen isotope profiles from shells in principle record both. Oxygen isotope data from late Pliocene bivalve molluscs of the southern North Sea basin show that the seasonal temperature range was at times much higher than previously estimated and higher than now. This suggests reduced oceanic heat supply, in contrast to some previous interpretations.
Carolien M. H. van der Weijst, Josse Winkelhorst, Wesley de Nooijer, Anna von der Heydt, Gert-Jan Reichart, Francesca Sangiorgi, and Appy Sluijs
Clim. Past, 18, 961–973, https://doi.org/10.5194/cp-18-961-2022, https://doi.org/10.5194/cp-18-961-2022, 2022
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A hypothesized link between Pliocene (5.3–2.5 million years ago) global climate and tropical thermocline depth is currently only backed up by data from the Pacific Ocean. In our paper, we present temperature, salinity, and thermocline records from the tropical Atlantic Ocean. Surprisingly, the Pliocene thermocline evolution was remarkably different in the Atlantic and Pacific. We need to reevaluate the mechanisms that drive thermocline depth, and how these are tied to global climate change.
Peter K. Bijl, Joost Frieling, Marlow Julius Cramwinckel, Christine Boschman, Appy Sluijs, and Francien Peterse
Clim. Past, 17, 2393–2425, https://doi.org/10.5194/cp-17-2393-2021, https://doi.org/10.5194/cp-17-2393-2021, 2021
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Here, we use the latest insights for GDGT and dinocyst-based paleotemperature and paleoenvironmental reconstructions in late Cretaceous–early Oligocene sediments from ODP Site 1172 (East Tasman Plateau, Australia). We reconstruct strong river runoff during the Paleocene–early Eocene, a progressive decline thereafter with increased wet/dry seasonality in the northward-drifting hinterland. Our critical review leaves the anomalous warmth of the Eocene SW Pacific Ocean unexplained.
Thomas J. Leutert, Sevasti Modestou, Stefano M. Bernasconi, and A. Nele Meckler
Clim. Past, 17, 2255–2271, https://doi.org/10.5194/cp-17-2255-2021, https://doi.org/10.5194/cp-17-2255-2021, 2021
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The Miocene climatic optimum associated with high atmospheric CO2 levels (~17–14 Ma) was followed by a period of dramatic climate change. We present a clumped isotope-based bottom-water temperature record from the Southern Ocean covering this key climate transition. Our record reveals warm conditions and a substantial cooling preceding the main ice volume increase, possibly caused by thresholds involved in ice growth and/or regional effects at our study site.
Ella W. Stokke, Morgan T. Jones, Lars Riber, Haflidi Haflidason, Ivar Midtkandal, Bo Pagh Schultz, and Henrik H. Svensen
Clim. Past, 17, 1989–2013, https://doi.org/10.5194/cp-17-1989-2021, https://doi.org/10.5194/cp-17-1989-2021, 2021
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In this paper, we present new sedimentological, geochemical, and mineralogical data exploring the environmental response to climatic and volcanic impact during the Paleocene–Eocene Thermal Maximum (~55.9 Ma; PETM). Our data suggest a rise in continental weathering and a shift to anoxic–sulfidic conditions. This indicates a rapid environmental response to changes in the carbon cycle and temperatures and highlights the important role of shelf areas as carbon sinks driving the PETM recovery.
Markus Raitzsch, Jelle Bijma, Torsten Bickert, Michael Schulz, Ann Holbourn, and Michal Kučera
Clim. Past, 17, 703–719, https://doi.org/10.5194/cp-17-703-2021, https://doi.org/10.5194/cp-17-703-2021, 2021
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At approximately 14 Ma, the East Antarctic Ice Sheet expanded to almost its current extent, but the role of CO2 in this major climate transition is not entirely known. We show that atmospheric CO2 might have varied on 400 kyr cycles linked to the eccentricity of the Earth’s orbit. The resulting change in weathering and ocean carbon cycle affected atmospheric CO2 in a way that CO2 rose after Antarctica glaciated, helping to stabilize the climate system on its way to the “ice-house” world.
Tom Dunkley Jones, Yvette L. Eley, William Thomson, Sarah E. Greene, Ilya Mandel, Kirsty Edgar, and James A. Bendle
Clim. Past, 16, 2599–2617, https://doi.org/10.5194/cp-16-2599-2020, https://doi.org/10.5194/cp-16-2599-2020, 2020
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We explore the utiliity of the composition of fossil lipid biomarkers, which are commonly preserved in ancient marine sediments, in providing estimates of past ocean temperatures. The group of lipids concerned show compositional changes across the modern oceans that are correlated, to some extent, with local surface ocean temperatures. Here we present new machine learning approaches to improve our understanding of this temperature sensitivity and its application to reconstructing past climates.
Martin Tetard, Ross Marchant, Giuseppe Cortese, Yves Gally, Thibault de Garidel-Thoron, and Luc Beaufort
Clim. Past, 16, 2415–2429, https://doi.org/10.5194/cp-16-2415-2020, https://doi.org/10.5194/cp-16-2415-2020, 2020
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Radiolarians are marine micro-organisms that produce a siliceous shell that is preserved in the fossil record and can be used to reconstruct past climate variability. However, their study is only possible after a time-consuming manual selection of their shells from the sediment followed by their individual identification. Thus, we develop a new fully automated workflow consisting of microscopic radiolarian image acquisition, image processing and identification using artificial intelligence.
Appy Sluijs, Joost Frieling, Gordon N. Inglis, Klaas G. J. Nierop, Francien Peterse, Francesca Sangiorgi, and Stefan Schouten
Clim. Past, 16, 2381–2400, https://doi.org/10.5194/cp-16-2381-2020, https://doi.org/10.5194/cp-16-2381-2020, 2020
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We revisit 15-year-old reconstructions of sea surface temperatures in the Arctic Ocean for the late Paleocene and early Eocene epochs (∼ 57–53 million years ago) based on the distribution of fossil membrane lipids of archaea preserved in Arctic Ocean sediments. We find that improvements in the methods over the past 15 years do not lead to different results. However, data quality is now higher and potential biases better characterized. Results confirm remarkable Arctic warmth during this time.
Marlow Julius Cramwinckel, Lineke Woelders, Emiel P. Huurdeman, Francien Peterse, Stephen J. Gallagher, Jörg Pross, Catherine E. Burgess, Gert-Jan Reichart, Appy Sluijs, and Peter K. Bijl
Clim. Past, 16, 1667–1689, https://doi.org/10.5194/cp-16-1667-2020, https://doi.org/10.5194/cp-16-1667-2020, 2020
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Phases of past transient warming can be used as a test bed to study the environmental response to climate change independent of tectonic change. Using fossil plankton and organic molecules, here we reconstruct surface ocean temperature and circulation in and around the Tasman Gateway during a warming phase 40 million years ago termed the Middle Eocene Climatic Optimum. We find that plankton assemblages track ocean circulation patterns, with superimposed variability being related to temperature.
Emily Dearing Crampton-Flood, Lars J. Noorbergen, Damian Smits, R. Christine Boschman, Timme H. Donders, Dirk K. Munsterman, Johan ten Veen, Francien Peterse, Lucas Lourens, and Jaap S. Sinninghe Damsté
Clim. Past, 16, 523–541, https://doi.org/10.5194/cp-16-523-2020, https://doi.org/10.5194/cp-16-523-2020, 2020
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The mid-Pliocene warm period (mPWP; 3.3–3.0 million years ago) is thought to be the last geological interval with similar atmospheric carbon dioxide concentrations as the present day. Further, the mPWP was 2–3 °C warmer than present, making it a good analogue for estimating the effects of future climate change. Here, we construct a new precise age model for the North Sea during the mPWP, and provide a detailed reconstruction of terrestrial and marine climate using a multi-proxy approach.
Gabriel J. Bowen, Brenden Fischer-Femal, Gert-Jan Reichart, Appy Sluijs, and Caroline H. Lear
Clim. Past, 16, 65–78, https://doi.org/10.5194/cp-16-65-2020, https://doi.org/10.5194/cp-16-65-2020, 2020
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Past climate conditions are reconstructed using indirect and incomplete geological, biological, and geochemical proxy data. We propose that such reconstructions are best obtained by statistical inversion of hierarchical models that represent how multi–proxy observations and calibration data are produced by variation of environmental conditions in time and/or space. These methods extract new information from traditional proxies and provide robust, comprehensive estimates of uncertainty.
Morgan T. Jones, Lawrence M. E. Percival, Ella W. Stokke, Joost Frieling, Tamsin A. Mather, Lars Riber, Brian A. Schubert, Bo Schultz, Christian Tegner, Sverre Planke, and Henrik H. Svensen
Clim. Past, 15, 217–236, https://doi.org/10.5194/cp-15-217-2019, https://doi.org/10.5194/cp-15-217-2019, 2019
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Mercury anomalies in sedimentary rocks are used to assess whether there were periods of elevated volcanism in the geological record. We focus on five sites that cover the Palaeocene–Eocene Thermal Maximum, an extreme global warming event that occurred 55.8 million years ago. We find that sites close to the eruptions from the North Atlantic Igneous Province display significant mercury anomalies across this time interval, suggesting that magmatism played a role in the global warming event.
Anna Joy Drury, Thomas Westerhold, David Hodell, and Ursula Röhl
Clim. Past, 14, 321–338, https://doi.org/10.5194/cp-14-321-2018, https://doi.org/10.5194/cp-14-321-2018, 2018
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North Atlantic Site 982 is key to our understanding of climate evolution over the past 12 million years. However, the stratigraphy and age model are unverified. We verify the composite splice using XRF core scanning data and establish a revised benthic foraminiferal stable isotope astrochronology from 8.0–4.5 million years ago. Our new stratigraphy accurately correlates the Atlantic and the Mediterranean and suggests a connection between late Miocene cooling and dynamic ice sheet expansion.
Paul E. Bachem, Bjørg Risebrobakken, Stijn De Schepper, and Erin L. McClymont
Clim. Past, 13, 1153–1168, https://doi.org/10.5194/cp-13-1153-2017, https://doi.org/10.5194/cp-13-1153-2017, 2017
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We present a high-resolution multi-proxy study of the Norwegian Sea, covering the 5.33 to 3.14 Ma time window within the Pliocene. We show that large-scale climate transitions took place during this warmer than modern time, most likely in response to ocean gateway transformations. Strong warming at 4.0 Ma in the Norwegian Sea, when regions closer to Greenland cooled, indicate that increased northward ocean heat transport may be compatible with expanding glaciation and Arctic sea ice growth.
Harry Dowsett, Aisling Dolan, David Rowley, Robert Moucha, Alessandro M. Forte, Jerry X. Mitrovica, Matthew Pound, Ulrich Salzmann, Marci Robinson, Mark Chandler, Kevin Foley, and Alan Haywood
Clim. Past, 12, 1519–1538, https://doi.org/10.5194/cp-12-1519-2016, https://doi.org/10.5194/cp-12-1519-2016, 2016
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Past intervals in Earth history provide unique windows into conditions much different than those observed today. We investigated the paleoenvironments of a past warm interval (~ 3 million years ago). Our reconstruction includes data sets for surface temperature, vegetation, soils, lakes, ice sheets, topography, and bathymetry. These data are being used along with global climate models to expand our understanding of the climate system and to help us prepare for future changes.
David Evans, Bridget S. Wade, Michael Henehan, Jonathan Erez, and Wolfgang Müller
Clim. Past, 12, 819–835, https://doi.org/10.5194/cp-12-819-2016, https://doi.org/10.5194/cp-12-819-2016, 2016
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We show that seawater pH exerts a substantial control on planktic foraminifera Mg / Ca, a widely applied palaeothermometer. As a result, temperature reconstructions based on this proxy are likely inaccurate over climatic events associated with a significant change in pH. We examine the implications of our findings for hydrological and temperature shifts over the Paleocene-Eocene Thermal Maximum and for the degree of surface ocean precursor cooling before the Eocene-Oligocene transition.
C. J. Hollis, B. R. Hines, K. Littler, V. Villasante-Marcos, D. K. Kulhanek, C. P. Strong, J. C. Zachos, S. M. Eggins, L. Northcote, and A. Phillips
Clim. Past, 11, 1009–1025, https://doi.org/10.5194/cp-11-1009-2015, https://doi.org/10.5194/cp-11-1009-2015, 2015
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Re-examination of a Deep Sea Drilling Project sediment core (DSDP Site 277) from the western Campbell Plateau has identified the initial phase of the Paleocene-Eocene Thermal Maximum (PETM) within nannofossil chalk, the first record of the PETM in an oceanic setting in the southern Pacific Ocean (paleolatitude of ~65°S). Geochemical proxies indicate that intermediate and surface waters warmed by ~6° at the onset of the PETM prior to the full development of the negative δ13C excursion.
E. O. Walliser, B. R. Schöne, T. Tütken, J. Zirkel, K. I. Grimm, and J. Pross
Clim. Past, 11, 653–668, https://doi.org/10.5194/cp-11-653-2015, https://doi.org/10.5194/cp-11-653-2015, 2015
A. M. Snelling, G. E. A. Swann, J. Pike, and M. J. Leng
Clim. Past, 10, 1837–1842, https://doi.org/10.5194/cp-10-1837-2014, https://doi.org/10.5194/cp-10-1837-2014, 2014
K. T. Lawrence, I. Bailey, and M. E. Raymo
Clim. Past, 9, 2391–2397, https://doi.org/10.5194/cp-9-2391-2013, https://doi.org/10.5194/cp-9-2391-2013, 2013
C. F. Dawber and A. K. Tripati
Clim. Past, 8, 1957–1971, https://doi.org/10.5194/cp-8-1957-2012, https://doi.org/10.5194/cp-8-1957-2012, 2012
G. E. A. Swann and S. V. Patwardhan
Clim. Past, 7, 65–74, https://doi.org/10.5194/cp-7-65-2011, https://doi.org/10.5194/cp-7-65-2011, 2011
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Annan, J. D. and Hargreaves, J. C.: A new global reconstruction of temperature changes at the Last Glacial Maximum, Clim. Past, 9, 367–376, https://doi.org/10.5194/cp-9-367-2013, 2013. a, b
Annan, J. D., Hargreaves, J. C., and Mauritsen, T.: A new global surface temperature reconstruction for the Last Glacial Maximum, Clim. Past, 18, 1883–1896, https://doi.org/10.5194/cp-18-1883-2022, 2022. a, b
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Evans, D., Brierley, C., Raymo, M. E., Erez, J., and Müller, W.: Planktic foraminifera shell chemistry response to seawater chemistry: Pliocene–Pleistocene seawater Mg
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Haywood, A. M., Tindall, J. C., Dowsett, H. J., Dolan, A. M., Foley, K. M., Hunter, S. J., Hill, D. J., Chan, W.-L., Abe-Ouchi, A., Stepanek, C., Lohmann, G., Chandan, D., Peltier, W. R., Tan, N., Contoux, C., Ramstein, G., Li, X., Zhang, Z., Guo, C., Nisancioglu, K. H., Zhang, Q., Li, Q., Kamae, Y., Chandler, M. A., Sohl, L. E., Otto-Bliesner, B. L., Feng, R., Brady, E. C., von der Heydt, A. S., Baatsen, M. L. J., and Lunt, D. J.: The Pliocene Model Intercomparison Project Phase 2: large-scale climate features and climate sensitivity, Clim. Past, 16, 2095–2123, https://doi.org/10.5194/cp-16-2095-2020, 2020. a, b
Huang, B., Thorne, P. W., Banzon, V. F., Boyer, T., Chepurin, G., Lawrimore, J. H., Menne, M. J., Smith, T. M., Vose, R. S., and Zhang, H.-M.: NOAA extended reconstructed sea surface temperature (ERSST), J. Climate 30, 8179–8205, https://doi.org/10.1175/JCLI-D-16-0836.1, 2017. a
Inglis, G. N., Bragg, F., Burls, N. J., Cramwinckel, M. J., Evans, D., Foster, G. L., Huber, M., Lunt, D. J., Siler, N., Steinig, S., Tierney, J. E., Wilkinson, R., Anagnostou, E., de Boer, A. M., Dunkley Jones, T., Edgar, K. M., Hollis, C. J., Hutchinson, D. K., and Pancost, R. D.: Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene–Eocene Thermal Maximum (PETM), and latest Paleocene, Clim. Past, 16, 1953–1968, https://doi.org/10.5194/cp-16-1953-2020, 2020. a
Karas, C., Khélifi, N., Bahr, A., Naafs, B., Nürnberg, D., and Herrle, J. O.: Did North Atlantic cooling and freshening from 3.65–3.5 Ma precondition Northern Hemisphere ice sheet growth?, Global Planet. Change, 185, 103085, https://doi.org/10.1016/j.gloplacha.2019.103085, 2020. a
Lawrence, K. T. and Woodard, S.: Past sea surface temperatures as measured by different proxies – A cautionary tale from the late Pliocene, Paleoceanography, 32, 318–324, https://doi.org/10.1002/2017PA003101, 2017. a
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McClymont, E. L., Ford, H. L., Ho, S. L., Tindall, J. C., Haywood, A. M., Alonso-Garcia, M., Bailey, I., Berke, M. A., Littler, K., Patterson, M. O., Petrick, B., Peterse, F., Ravelo, A. C., Risebrobakken, B., De Schepper, S., Swann, G. E. A., Thirumalai, K., Tierney, J. E., van der Weijst, C., White, S., Abe-Ouchi, A., Baatsen, M. L. J., Brady, E. C., Chan, W.-L., Chandan, D., Feng, R., Guo, C., von der Heydt, A. S., Hunter, S., Li, X., Lohmann, G., Nisancioglu, K. H., Otto-Bliesner, B. L., Peltier, W. R., Stepanek, C., and Zhang, Z.: Lessons from a high-CO2 world: an ocean view from ∼ 3 million years ago, Clim. Past, 16, 1599–1615, https://doi.org/10.5194/cp-16-1599-2020, 2020. a, b, c, d, e, f, g, h, i, j, k
McClymont, E. L., Ho, S.-L., Ford, H. L., Bailey, I., Berke, M. A., Bolton, C., De Schepper, S., Grant, G., Groeneveld, J., Inglis, G., Karas, C., Patterson, M., Swann, G., Thirumalai, K., S.M.White, Alonso-Garcia, M., Anand, P., Hoogakker, B. A. A., Littler, K., Petrick, B. F., Risebrobakken, B., Abell, J., Crocker, A., de Graaf, F., Feakins, S., Hargreaves, J., Jones, C., Markowska, M., Ratnayake, A., Stepanek, C., and Tangunan, D.: Climate Evolution through the onset and intensification of Northern Hemisphere Glaciation, Rev. Geophys., 61, e2022RG000793, https://doi.org/10.1029/2022RG000793, 2023. a, b, c
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Sherwood, S. C., Webb, M. J., Annan, J. D., Armour, K. C., Forster, P. M., Hargreaves, J. C., Hegerl, G., Klein, S. A., Marvel, K. D., Rohling, E. J., Watanabe, M., Andrews, T., Braconnot, P., Bretherton, C. S., Foster, G. L., Hausfather, Z., von der Heydt, A. S., Knutti, R., Mauritsen, T., Norris, J. R., Proistosescu, C., Rugenstein, M., Schmidt, G. A., Tokarska, K. B., and Zelinka, M. D.: An assessment of Earth's climate sensitivity using multiple lines of evidence, Rev. Geophys., 58, e2019RG000678, https://doi.org/10.1029/2019RG000678, 2020. a
Smith, D. M., Screen, J. A., Deser, C., Cohen, J., Fyfe, J. C., García-Serrano, J., Jung, T., Kattsov, V., Matei, D., Msadek, R., Peings, Y., Sigmond, M., Ukita, J., Yoon, J.-H., and Zhang, X.: The Polar Amplification Model Intercomparison Project (PAMIP) contribution to CMIP6: investigating the causes and consequences of polar amplification, Geosci. Model Dev., 12, 1139–1164, https://doi.org/10.5194/gmd-12-1139-2019, 2019. a
Tierney, J. E. and Tingley, M. P.: BAYSPLINE: A New Calibration for the Alkenone Paleothermometer, Paleoceanography and Paleoclimatology, 33, 281–301, https://doi.org/10.1002/2017PA003201, 2018. a
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Co-editor-in-chief
This study presents an interesting attempt to reconstruct global surface temperature by combining sparse SST proxy data and PlioMIP2 simulations using a state-of-the-art data assimilation framework. The work highlights the potential of this method for providing key insights into past warming patterns, and will serve as a good starting point for future investigations.
This study presents an interesting attempt to reconstruct global surface temperature by...
Short summary
We have created a new global surface temperature reconstruction of the climate of the mid-Pliocene Warm Period, representing the period roughly 3.2 million years before the present day. We estimate that the globally averaged mean temperature was around 3.9 °C warmer than it was in pre-industrial times, but there is significant uncertainty in this value.
We have created a new global surface temperature reconstruction of the climate of the...
