Kira Lawrence, Helen Coxall, Sindia Sosdian, Margret Steinthorsdottir
This data portal serves as a resource for investigators interested in the study of Miocene climate, about 23 to 5 million years ago. It collates a list of key information about published Miocene sea surface temperature records to enable researchers to rapidly locate and evaluate datasets relevant to the study of Miocene climate change.
The resource provides the metadata for study sites, a map of the location of these sites, references to papers describing the datasets, and links to where each dataset is archived.
The resource also contains a user interface that allows researchers to add information about their new published datasets to the inventory such that it will continue to provide an up to date listing of existing Miocene temperature proxy records.
Here is a map and a data table showing information about published Miocene temperature proxy data. All information can be downloaded at the download button above.
Click on map markers or table rows to show site details. Map marker colours indicate different proxy data types according to the legend (abbreviations are explained below).
Table sorting order, search filter, fullscreen mode and additional columns can be selected interactively.
Click on the button below to provide a new entry to the list of Miocene temperature records. To be added, the data record must be described in a peer-reviewed published work and the data must be archived in an open repository. The information you enter will be vetted by us and will be added to the public data list if it meets the criteria.
The Miocene — a warm period in the past
The Miocene, ~23 – 5 million years ago (Ma), was an interval of overall global warmth relative to the present day. The animals and plants of the Miocene included some quite familiar looking ancestors of modern flora and fauna (Figure 1). Many geographic and oceanic features were also similar to those of today. In fact, many characteristics of the Miocene make this interval of interest as a potential analog for future warm climate conditions. During the early to mid-Miocene (23 – 14 Ma) global temperatures and atmospheric carbon dioxide (CO₂) concentrations were similar to those projected in the coming centuries as a consequence of human-induced climate change1–10. During the early to mid-Miocene, there was also a major collapse of the East Antarctic Ice Sheet, followed by regrowth and onset of a West Antarctic Ice Sheet in the late Miocene11–17. Across the early to middle Miocene, tectonic reorganizations and closure of low latitude seaways played a role in climate change. By the middle Miocene global geography similar to today was achieved18.
Figure 1: Miocene overview
Miocene climatic, oceanic and tectonic changes and select biotic developments, as summarized in Figure 1 in The Miocene: the Future of the Past (Steinthorsdottir et al., 2020)39. Reproduced with permission from AGU.
Middle Miocene — warmhouse to icehouse
Global mean surface temperature during peak Miocene warmth, the Miocene Climate Optimum (MCO) (Figure 2), was 3 – 4 °C warmer than today (~17 – 14.7 Ma)19. Estimates of atmospheric CO₂ concentrations during the MCO range from ~580 – 670 ppm3,4,7–9. This interval was followed by the Middle Miocene Climate Transition (MMCT), which was marked by a 2 °C cooling of deep ocean temperatures and a rapid expansion of the East and West Antarctic Ice Sheets at 14 – 13 Ma as reflected in a stepwise increase in benthic foraminiferal oxygen isotope ratios, a proxy for both ice volume and deep ocean temperature14,16,17,20. CO₂ levels after the Miocene Climate Transition were 380 – 420 ppm1,3,7. Proxy records show widespread cooling in regions around Antarctica and in the North Atlantic9,16,21, a reorganization of polar fronts22,23, and alterations in tropical climate patterns24–26 across the MMCT.
Figure 2: Middle Miocene environment
Middle Miocene (~20 – 14 Ma) topography and sea surface temperature. Topography from the updated Herold boundary conditions as in Burls et al. (2021)40. Sea surface temperatures derived from multi model mean of all simulations forced with Middle Miocene boundary conditions, as listed in Table 2 of Burls et al. (2021). Figure made by Natalie Burls, George Mason University, Virginia, USA.
The late Miocene — cooling and large ecosystem changes
The late Miocene (11 Ma to 5.3 Ma) was a time of enormous change in terrestrial environments and ecosystems, including the well documented expansion of C₄ grasslands (plants that used the C₄ photosynthetic pathway) across large swaths of the tropics and subtropics26–28. A broad drying of the landscape in the subtropics29 and a global radiation of succulent plant lineages also occurred30. These floral changes were accompanied by large turnovers in terrestrial fauna31,32. While benthic foraminiferal oxygen isotope records of the late Miocene (a proxy for both ice volume and deep ocean temperature) show no long-term trend33, records of ocean surface temperature reveal substantial (~6 °C) interhemispheric cooling during the late Miocene34. This disparity suggests that the late Miocene cooling did not lead to a significant permanent increase in continental ice volume and implies that in high latitude deep water formation regions waters were cold prior to the late Miocene.
Causes of Miocene climate change
Carbon cycle changes as well as changes in heat and moisture transport have been implicated as potential causes for the shifting climate conditions of the Miocene26,35,36. Across the early to mid-Miocene, the carbon cycle shows dynamic changes with a long-lasting (~3.5 Myrs) positive carbon isotope excursion evident in foraminiferal records, with the onset of global warmth and reduced ice volume during the MCO. Following the MMCT and the shift from ‘warmhouse’ to icehouse climate state, the carbon isotopic ratio of the global ocean declined. Available records documenting Miocene carbon cycle changes hint at a dynamic interaction between volcanism, organic carbon burial, and weathering26,37,38, including a large shift in how and where carbon is stored on land as Arctic tundra and permafrost biomes expanded ca. 6 Ma36. Identifying the carbon cycle feedbacks at play during past warm intervals like the Miocene, when CO₂ was similar to our near future, is useful for anticipating potential future climatic changes. Understanding the mechanisms that drove the observed climatic shifts, is at the heart of Miocene climate research.
Cyclization index of tetraethers is a ratio of 86-carbon tetraether lipids (GDGTs) which is sensitive to temperature and growth conditions. These organic compounds originate from ammonia-oxidizing Thaumarchaeota.
The ratio of magnesium to calcium in the shells of foraminifera is sensitive to the temperature of the water in which these organisms grew and can serve as a proxy for water temperature at a range of depths depending on the depth habitat of the organisms being analyzed.
The alkenone unsaturation index is the ratio of di- and tri-unsaturated ketones, which are organic compounds produced by a group of marine algae. This ratio is sensitive to organism growth temperature and thus the temperature of the sea surface.
The clumped isotope paleothermometer is based on the difference between the measured and stochastic abundance of doubly substituted isotopologues of CO₂. This value is formation temperature controlled and typically measured on CO₂ derived from biogenic or inorganic carbonates.
Sea surface temperature.
The Oligocene/Miocene boundary (23.03 Ma)
Early-middle Miocene (23.03 – ~16.9 Ma)
The Miocene Climatic Optimum (~16.9 – 14.7 Ma)
Middle-late Miocene (~14.7 – 5.33 Ma)
The Miocene/Pliocene boundary (5.33 Ma)
Obtain paleo coordinates
If you wish to obtain paleolatitude and paleolongitude for any site, we recommend you use Geo Plates web service.
Badger MPS, Lear CH, Pancost RD, et al. CO2 drawdown following the middle Miocene expansion of the Antarctic Ice Sheet. Paleoceanography. 2013;28(1):42-53. https://doi.org/10.1002/palo.20015
Ekart DD, Cerling TE, Montanez IP, Tabor NJ. A 400 million year carbon isotope record of pedogenic carbonate: Implications for paleoatmospheric carbon dioxide. Am J Sci. 1999;299(10):805-827. https://doi.org/10.2475/ajs.299.10.805
Greenop R, Foster GL, Wilson PA, Lear CH. Middle Miocene climate instability associated with high-amplitude CO2 variability. Paleoceanography. 2014;29(9):845-853. https://doi.org/10.1002/2014PA002653
Kürschner WM, Kvaček Z, Dilcher DL. The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of terrestrial ecosystems. Proc Natl Acad Sci. 2008;105(2):449. https://doi.org/10.1073/pnas.0708588105
Sosdian SM, Greenop R, Hain MP, Foster GL, Pearson PN, Lear CH. Constraining the evolution of Neogene ocean carbonate chemistry using the boron isotope pH proxy. Earth Planet Sci Lett. 2018;498:362-376. https://doi.org/10.1016/j.epsl.2018.06.017
Steinthorsdottir M, Jardine PE, Rember WC. Near-Future pCO2 during the hot Mid Miocene Climatic Optimum. Paleoceanogr Paleoclimatology. 2020;n/a(n/a):e2020PA003900. https://doi.org/10.1029/2020PA003900
Super JR, Thomas E, Pagani M, Huber M, O’Brien C, Hull PM. North Atlantic temperature and pCO2 coupling in the early-middle Miocene. Geology. 2018;46(6):519-522. https://doi.org/10.1130/G40228.1
Zhang YG, Pagani M, Liu Z, Bohaty SM, DeConto R. A 40-million-year history of atmospheric CO2. Philos Trans R Soc Math Phys Eng Sci. 2013;371(2001):20130096. https://doi.org/10.1098/rsta.2013.0096
Greenop R, Sosdian SM, Henehan MJ, Wilson PA, Lear CH, Foster GL. Orbital Forcing, Ice Volume, and CO2 Across the Oligocene-Miocene Transition. Paleoceanogr Paleoclimatology. 2019;34(3):316-328. https://doi.org/10.1029/2018PA003420
John CM, Karner GD, Browning E, et al. Timing and magnitude of Miocene eustasy derived from the mixed siliciclastic-carbonate stratigraphic record of the northeastern Australian margin. Earth Planet Sci Lett. 2011;304(3):455-467. https://doi.org/10.1016/j.epsl.2011.02.013
Lear CH, Coxall HK, Foster GL, et al. Neogene ice volume and ocean temperatures: Insights from infaunal foraminiferal Mg/Ca paleothermometry. Paleoceanography. 2015;30(11):1437-1454. https://doi.org/10.1002/2015PA002833
Levy R, Harwood D, Florindo F, et al. Antarctic ice sheet sensitivity to atmospheric CO2 variations in the early to mid-Miocene. Acton G, Askin R, Atkins C, et al., eds. Proc Natl Acad Sci. 2016;113(13):3453–3458. https://doi.org/10.1073/pnas.1516030113
Westerhold T, Marwan N, Drury AJ, et al. An astronomically dated record of Earth’s climate and its predictability over the last 66 million years. Science. 2020;369(6509):1383–1387. https://doi.org/10.1126/science.aba6853
Herold N, Seton M, Müller RD, You Y, Huber M. Middle Miocene tectonic boundary conditions for use in climate models. Geochem Geophys Geosystems. 2008;9(10). https://doi.org/10.1029/2008GC002046
Kuhnert H, Bickert T, Paulsen H. Southern Ocean frontal system changes precede Antarctic ice sheet growth during the middle Miocene. Earth Planet Sci Lett. 2009;284(3):630-638. https://doi.org/10.1016/j.epsl.2009.05.030
Verducci M, Foresi LM, Scott GH, Sprovieri M, Lirer F, Pelosi N. The Middle Miocene climatic transition in the Southern Ocean: Evidence of paleoclimatic and hydrographic changes at Kerguelen plateau from planktonic foraminifers and stable isotopes. Palaeogeogr Palaeoclimatol Palaeoecol. 2009;280(3):371-386. https://doi.org/10.1016/j.palaeo.2009.06.024
Holbourn A, Kuhnt W, Regenberg M, Schulz M, Mix A, Andersen N. Does Antarctic glaciation force migration of the tropical rain belt? Geology. 2010;38(9):783-786. https://doi.org/10.1130/G31043.1
Rousselle G, Beltran C, Sicre MA, Raffi I, De Rafelis M. Sea-surface condition changes in the Equatorial Pacific during the Mio-Pliocene as inferred from coccolith geochemistry. Earth Planet Sci Lett. 2013;361:412-421. https://doi.org/10.1016/j.epsl.2012.11.003
Sosdian SM, Babila TL, Greenop R, Foster GL, Lear CH. Ocean Carbon Storage across the middle Miocene: a new interpretation for the Monterey Event. Nat Commun. 2020;11(1):134. https://doi.org/10.1038/s41467-019-13792-0
Cerling TE, Harris JM, MacFadden BJ, et al. Global Vegetation change through the Miocene/Pliocene boundary. Nature. 1997;389:153-158. https://doi.org/10.1038/38229
Dupont LM, Rommerskirchen F, Mollnehauer G, Schefub E. Miocene to Pliocene changes in South African hydrology and vegetation in relation to the expansion of C4 Plants. Earth Planet Sci Lett. 2013;375:408-417. https://doi.org/10.1016/j.epsl.2013.06.005
Arakaki M, Christin P-A, Nyffeler R, et al. Contemporaneous and recent radiations of the world’s major succulent plant lineages. Proc Natl Acad Sci. 2011;108(20):8379-8384. https://doi.org/10.1073/PNAS.1100628108
Badgley C, Barry JC, Morgan ME, et al. Ecological changes in Miocene mammalian record show impact of prolonged climatic forcing. Proc Natl Acad Sci. 2008;105(34):12145. https://doi.org/10.1073/pnas.0805592105
Wang Y, Cerling TE, MacFadden BJ. Fossile horses and carbon isotopes: new evidence for Cenozoic dietary, habitat, and ecosystem changes in North America. Palaeogeogr Palaeoclimatol Palaeoecol. 1994;107:269-279. https://doi.org/10.1016/0031-0182(94)90099-X
Herbert TD, Lawrence KT, Tzanova A, Peterson LC, Caballero-Gill R, Kelly CS. Late Miocene global cooling and the rise of modern ecosystems. Nat Geosci. 2016;9:843-847. https://doi.org/10.1038/ngeo2813
De Vleeschouwer D, Drury AJ, Vahlenkamp M, Rochholz F, Liebrand D, Pälike H. High-latitude biomes and rock weathering mediate climate–carbon cycle feedbacks on eccentricity timescales. Nat Commun. 2020;11(1):5013. https://doi.org/10.1038/s41467-020-18733-w
Hodell DA, Woodruff F. Variations in the strontium isotopic ratio of seawater during the Miocene: Stratigraphic and geochemical implications. Paleoceanography. 1994;9(3):405-426. https://doi.org/10.1029/94PA00292
Steinthorsdottir M, Coxall HK, de Boer AM, Huber M, Barbolini N, Bradshaw CD, et al. The Miocene: the Future of the Past. Paleoceanography and Paleoclimatology. 2020;35:e2020PA004037. https://doi.org/10.1029/2020PA004037
Burls NJ, Bradshaw CD, De Boer AM, Herold N, Huber M, Pound M, Donnadieu Y, Farnsworth A, Frigola A, Gasson E, von der Heydt AS, Hutchinson DK, Knorr G, Lawrence KT, Lear CH, Li X, Lohmann G, Lunt DJ, Marzocchi A, Prange M, Riihimaki CA, Sarr A-C, Siler N, Zhang Z. Simulating Miocene warmth: insights from an opportunistic Multi-Model ensemble (MioMIP1). Paleoceanography and Paleoclimatology. 2021. https://doi.org/10.1029/2020PA004054
This dataset consists of a table with key information about published Miocene temperature records, which can be downloaded as a comma-separated values (csv) text file having the following content for each site:
Type of temperature record
Proxy data type
Modern latitude (degrees, positive is North)
Modern longitude (degrees, positive is East)
Modern sea surface temperature (°C)
Modern bottom water temperature (°C) (if applicable)
Modern water depth (m)
Paleo water depth (m) (if applicable)
Age description (see list with abbreviations for definitions)
Starting age (Ma)
Ending age (Ma)
Average Sample Resolution (kyr)
References to papers describing the data
Web address to the data
The csv file is saved with utf-8 encoding. It can be opened in any standard text editor, spreadsheet or other data analysis software. Several guides for how to import this type of file in Excel are available on the web, e.g. at the Institute for Advanced Study.
The initial compilation of data available here was prepared for the article Simulating Miocene warmth: insights from an opportunistic multi-model ensemble (MioMIP1) by Burls et al (2021)<sup>40</sup>.
Thanks to Natalie Burls, Matthew Huber, Sevasti Modestou, Francesca Sangiorgi, Timothy Herbert, Carrie Lear, and Ann Pearson for their contribution to this data portal.
Department of Geological Sciences Stockholm University
SE-106 91 Stockholm Sweden