Spatial pattern of super-greenhouse warmth controlled by elevated specific humidity


Earth’s climate sensitivity, defined as the temperature increase for a doubling of partial pressure of carbon dioxide (\(p_{\mathrm{CO}_2}\)), and the mechanisms responsible for amplification of high-latitude warming remain controversial. The latest Palaeocene/earliest Eocene (LPEE; 57–55 million years ago) is a time when atmospheric CO2 concentrations peaked between 1,400 and 4,000 ppm, which allows us to evaluate the climatic response to high \(p_{\mathrm{CO}_2}\). Here we present a reconstruction of continental temperatures and oxygen isotope compositions of precipitation (reflective of specific humidity) based on clumped and oxygen isotope analysis of pedogenic siderites. We show that continental mean annual temperatures reached 41 °C in the equatorial tropics, and summer temperatures reached 23 °C in the Arctic. The oxygen isotope compositions of precipitation reveal that compared with the present day the hot LPEE climate was characterized by an increase in specific humidity and the average residence time of atmospheric moisture and by a decrease in the subtropical-to-polar specific humidity gradient. The global increase in specific humidity reflects the fact that atmospheric vapour content is more sensitive to changes in \(p_{\mathrm{CO}_2}\) than evaporation and precipitation, resulting in an increase in the residence time of moisture in the atmosphere. Pedogenic siderite data from other super-greenhouse periods support the evidence that the spatial patterns of specific humidity and warmth are related, providing a new means to evaluate Earth’s climate sensitivity.

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Fig. 1: Temperature reconstructions during the LPEE.
Fig. 2: Siderite-based reconstructions of the oxygen isotope composition of mean annual precipitation (δ18Op) during the LPEE.
Fig. 3: Spatial pattern in elevated specific humidity during the LPEE.

Data availability

All data discussed in the main text and plotted in the main figures and extended data figures are included in Supplementary Excel files stored in a Pangaea database ( and available along with the Supplementary Information. Siderite clumped and oxygen isotope data can be found in Supplementary Data 3. Raw clumped and oxygen isotope data is stored in an offline Easotope database that can be provided upon request by S.M.B. A compilation of siderite-based and previous early Palaeogene temperatures, both on land and in the ocean, can be found in Supplementary Data 2 together with the respective references that are also included in the Supplementary Information. A compilation of siderite-based reconstructions of δ18Op and previous reconstructions of δDp can be found in Supplementary Data 1. Microprobe data on siderite trace elemental concentrations can be found in Supplementary Data 4. Calculated LPEE saturation vapour pressures can be found in Supplementary Data 5.


  1. 1.

    Foster, G. L., Royer, D. L. & Lunt, D. J. Future climate forcing potentially without precedent in the last 420 million years. Nat. Commun. 8, 14845 (2017).

    Google Scholar 

  2. 2.

    Dickens, G. R., Castillo, M. M. & Walker, J. C. G. A blast of gas in the latest Paleocene: simulating first-order effects of massive dissociation of oceanic methane hydrate. Geology 25, 259–262 (1997).

    Google Scholar 

  3. 3.

    Shackleton, N. J. & Kennett, J. P. Paleotemperature History of the Cenozoic and the Initiation of Antarctic Glaciation; Oxygen and Carbon Isotope Analyses in DSDP Sites 277, 279 and 281 (Deep Sea Drilling Project, 1975).

  4. 4.

    Wing, S. L. & Greenwood, D. R. Fossils and fossil climate: the case for equable continental interiors in the Eocene. Philos. Trans. R. Soc. Lond. B 341, 243–252 (1993).

    Google Scholar 

  5. 5.

    Tierney, J. E., Sinninghe Damsté, J. S., Pancost, R. D., Sluijs, A. & Zachos, J. C. Eocene temperature gradients. Nat. Geosci. 10, 538–539 (2017).

    Google Scholar 

  6. 6.

    Evans, D. et al. Eocene greenhouse climate revealed by coupled clumped isotope-Mg/Ca thermometry. Proc. Natl Acad. Sci. USA 115, 1174–1179 (2018).

    Google Scholar 

  7. 7.

    Suan, G. et al. Subtropical climate conditions and mangrove growth in Arctic Siberia during the early Eocene. Geology 45, 539–542 (2017).

    Google Scholar 

  8. 8.

    Caballero, R. & Huber, M. State-dependent climate sensitivity in past warm climates and its implications for future climate projections. Proc. Natl Acad. Sci. USA 110, 14162–14167 (2013).

    Google Scholar 

  9. 9.

    Carmichael, M. J. et al. Hydrological and associated biogeochemical consequences of rapid global warming during the Paleocene–Eocene Thermal Maximum. Glob. Planet. Change 157, 114–138 (2017).

    Google Scholar 

  10. 10.

    Pagani, M. et al. Arctic hydrology during global warming at the Palaeocene/Eocene thermal maximum. Nature (2006).

  11. 11.

    Carmichael, M. J. et al. A model–model and data–model comparison for the early Eocene hydrological cycle. Clim. Past (2016).

  12. 12.

    White, T., Bradley, D., Haeussler, P. & Rowley, D. B. Late Paleocene–early Eocene paleosols and a new measure of the transport distance of Alaska’s Yakutat Terrane. J. Geol. 125, 113–123 (2017).

    Google Scholar 

  13. 13.

    van Dijk, J. et al. Experimental calibration of clumped isotopes in siderite between 8.5 and 62 °C and its application as paleo-thermometer in paleosols. Geochim. Cosmochim. Acta 254, 1–20 (2019).

    Google Scholar 

  14. 14.

    Cermak, V., Bodri, L., Kresl, M., Dedecek, P. & Safanda, J. Eleven years of ground–air temperature tracking over different land cover types. Int. J. Climatol. 37, 1084–1099 (2017).

    Google Scholar 

  15. 15.

    Jaramillo, C. et al. Effects of rapid global warming at the Paleocene–Eocene boundary on neotropical vegetation. Science (2010).

  16. 16.

    Berry, J. & Bjorkman, O. Photosynthetic response and adaptation to temperature in higher plants. Annu. Rev. Plant Physiol. (1980).

  17. 17.

    Silvola, J., Vaelijoki, J. & Aaltonen, H. Effect of draining and fertilization on soil respiration at three ameliorated peatland sites. Acta Forestalia Fennica 191, 1–32 (1985).

    Google Scholar 

  18. 18.

    Eberle, J. J. et al. Seasonal variability in Arctic temperatures during early Eocene time. Earth Planet. Sci. Lett. 296, 481–486 (2010).

    Google Scholar 

  19. 19.

    Hyland, E. G., Huntington, K. W., Sheldon, N. D. & Reichgelt, T. Temperature seasonality in the North American continental interior during the Early Eocene Climatic Optimum. Clim. Past 14, 1391–1404 (2018).

    Google Scholar 

  20. 20.

    Snell, K. E. et al. Hot summers in the Bighorn Basin during the early Paleogene. Geology 41, 55–58 (2013).

    Google Scholar 

  21. 21.

    Shukla, A., Mehrotra, R. C., Spicer, R. A., Spicer, T. E. V. & Kumar, M. Cool equatorial terrestrial temperatures and the South Asian monsoon in the early Eocene: evidence from the Gurha Mine, Rajasthan, India. Palaeogeogr. Palaeoclimatol. Palaeoecol. (2014).

  22. 22.

    Naafs, B. D. A. et al. High temperatures in the terrestrial mid-latitudes during the early Palaeogene. Nat. Geosci. (2018).

  23. 23.

    Seneviratne, S. I., Lüthi, D., Litschi, M. & Schär, C. Land–atmosphere coupling and climate change in Europe. Nature (2006).

  24. 24.

    Kelson, J. R. et al. A proxy for all seasons? A synthesis of clumped isotope data from Holocene soil carbonates. Quat. Sci. Rev. (2020).

  25. 25.

    Huber, M. & Caballero, R. The early Eocene equable climate problem revisited. Clim. Past 7, 603–633 (2011).

    Google Scholar 

  26. 26.

    Yurtsever, Y. Worldwide Survey of Stable Isotopes in Precipitation (International Atomic Energy Agency, 1975).

  27. 27.

    Lee, J. E., Fung, I., DePaolo, D. J. & Otto-Bliesner, B. Water isotopes during the Last Glacial Maximum: new general circulation model calculations. J. Geophys. Res. Atmos. (2008).

  28. 28.

    Speelman, E. N. et al. Modeling the influence of a reduced Equator-to-pole sea surface temperature gradient on the distribution of water isotopes in the early/middle Eocene. Earth Planet. Sci. Lett. 298, 57–65 (2010).

    Google Scholar 

  29. 29.

    Cramwinckel, M. J. et al. Synchronous tropical and polar temperature evolution in the Eocene. Nature 559, 382–386 (2018).

    Google Scholar 

  30. 30.

    Barron, E. J. Eocene Equator‐to‐pole surface ocean temperatures: a significant climate problem? Paleoceanography 2, 729–739 (1987).

    Google Scholar 

  31. 31.

    Singh, H. K. A., Bitz, C. M., Donohoe, A., Nusbaumer, J. & Noone, D. C. A mathematical framework for analysis of water tracers. Part II: understanding large-scale perturbations in the hydrological cycle due to CO2 doubling. J. Clim. (2016).

  32. 32.

    Held, I. & Soden, B. Robust responses of the hydrological cycle to global warming. J. Clim. 19, 5686–5699 (2006).

    Google Scholar 

  33. 33.

    Aggarwal, P. K. et al. Stable isotopes in global precipitation: a unified interpretation based on atmospheric moisture residence time. Geophys. Res. Lett. (2012).

  34. 34.

    Winnick, M. J., Caves, J. K. & Chamberlain, C. P. A mechanistic analysis of early eocene latitudinal gradients of isotopes in precipitation. Geophys. Res. Lett. 42, 8216–8224 (2015).

    Google Scholar 

  35. 35.

    Kukla, T., Winnick, M. J., Maher, K., Ibarra, D. E. & Chamberlain, C. P. The sensitivity of terrestrial δ18O gradients to hydroclimate evolution. J. Geophys. Res. Atmos. (2019).

  36. 36.

    Noone, D. & Simmonds, I. Associations between δ18O of water and climate parameters in a simulation of atmospheric circulation for 1979–95. J. Clim. (2002).

  37. 37.

    Rozanski, K. in Isotopes in the Water Cycle: Past, Present and Future of a Developing Science (eds Aggarwal, P. K. et al.) 291–302 (Springer, 2005).

  38. 38.

    Moore, M., Kuang, Z. & Blossey, P. N. A moisture budget perspective of the amount effect. Geophys. Res. Lett. (2014).

  39. 39.

    Siler, N., Roe, G. H. & Armour, K. C. Insights into the zonal-mean response of the hydrologic cycle to global warming from a diffusive energy balance model. J. Clim. (2018).

  40. 40.

    Carmichael, M. J., Pancost, R. D. & Lunt, D. J. Changes in the occurrence of extreme precipitation events at the Paleocene–Eocene thermal maximum. Earth Planet. Sci. Lett. (2018).

  41. 41.

    Abbot, D. S. & Tziperman, E. Sea ice, high-latitude convection, and equable climates. Geophys. Res. Lett. (2008).

  42. 42.

    Aggarwal, P. K. et al. Proportions of convective and stratiform precipitation revealed in water isotope ratios. Nat. Geosci. (2016).

  43. 43.

    Schneider, T., Kaul, C. M. & Pressel, K. G. Possible climate transitions from breakup of stratocumulus decks under greenhouse warming. Nat. Geosci. (2019).

  44. 44.

    Zhu, J. et al. Simulation of early Eocene water isotopes using an Earth system model and its implication for past climate reconstruction. Earth Planet. Sci. Lett. (2020).

  45. 45.

    Alduchov, O. A. & Eskridge, R. E. Improved Magnus form approximation of saturation vapor pressure. J. Appl. Meteorol. (1996).

  46. 46.

    Kavanaugh, J. L. & Cuffey, K. M. Space and time variation of δ18O and δD in Antarctic precipitation revisited. Global Biogeochem. Cycles 17, 1017 (2003).

    Google Scholar 

  47. 47.

    Zhu, J., Poulsen, C. J. & Tierney, J. E. Simulation of Eocene extreme warmth and high climate sensitivity through cloud feedbacks. Sci. Adv. (2019).

  48. 48.

    Global Network of Isotopes in Precipitation. The GNIP Database (International Atomic Energy Agency and World Meteorological Organization, accessed November 2018);

  49. 49.

    Handley, L., Pearson, P. N., McMillan, I. K. & Pancost, R. D. Large terrestrial and marine carbon and hydrogen isotope excursions in a new Paleocene/Eocene boundary section from Tanzania. Earth Planet. Sci. Lett. 275, 17–25 (2008).

    Google Scholar 

  50. 50.

    Garel, S. et al. Paleohydrological and paleoenvironmental changes recorded in terrestrial sediments of the Paleocene–Eocene boundary (Normandy, France). Palaeogeogr. Palaeoclimatol. Palaeoecol. (2013).

  51. 51.

    Tipple, B. J. et al. Coupled high-resolution marine and terrestrial records of carbon and hydrologic cycles variations during the Paleocene–Eocene Thermal Maximum (PETM). Earth Planet. Sci. Lett. (2011).

  52. 52.

    Handley, L., Crouch, E. M. & Pancost, R. D. A New Zealand record of sea level rise and environmental change during the Paleocene–Eocene Thermal Maximum. Palaeogeogr. Palaeoclimatol. Palaeoecol.

  53. 53.

    Schmid, T. W., Radke, J., Bernasconi, S. M. & Iv, K. Clumped-Isotope Measurements on Small Carbonate Samples with a Kiel IV Carbonate Device and a MAT 253 Mass Spectrometer Application Note No. 30233 (Thermo Fisher, 2012).

  54. 54.

    Meckler, A. N., Ziegler, M., Millán, M. I., Breitenbach, S. F. M. & Bernasconi, S. M. Long-term performance of the Kiel carbonate device with a new correction scheme for clumped isotope measurements. Rapid Commun. Mass Spectrom. 28, 1705–1715 (2014).

    Google Scholar 

  55. 55.

    Müller, I. A. et al. Clumped isotope fractionation during phosphoric acid digestion of carbonates at 70 °C. Chem. Geol. 449, 1–14 (2017).

    Google Scholar 

  56. 56.

    Müller, I. A. et al. Carbonate clumped isotope analyses with the long-integration dual-inlet (LIDI) workflow: scratching at the lower sample weight boundaries. Rapid Commun. Mass Spectrom. 31, 1057–1066 (2017).

    Google Scholar 

  57. 57.

    Bernasconi, S. M. et al. Reducing uncertainties in carbonate clumped isotope analysis through consistent carbonate-based standardization. Geochem. Geophys. Geosyst. (2018).

  58. 58.

    Hu, B. et al. A modified procedure for gas-source isotope ratio mass spectrometry: the long-integration dual-inlet (LIDI) methodology and implications for clumped isotope measurements. Rapid Commun. Mass Spectrom. 28, 1413–1425 (2014).

    Google Scholar 

  59. 59.

    Bernasconi, S. M. et al. Background effects on Faraday collectors in gas-source mass spectrometry and implications for clumped isotope measurements. Rapid Commun. Mass Spectrom. 27, 603–612 (2013).

    Google Scholar 

  60. 60.

    John, C. M. & Bowen, D. Community software for challenging isotope analysis: first applications of ‘Easotope’ to clumped isotopes. Rapid Commun. Mass Spectrom. 30, 2285–2300 (2016).

    Google Scholar 

  61. 61.

    Brand, W. A., Assonov, S. S. & Coplen, T. B. Correction for the 17O interference in δ13C measurements when analyzing CO2 with stable isotope mass spectrometry (IUPAC Technical Report). Pure Appl. Chem. 82, 1719–1733 (2010).

    Google Scholar 

  62. 62.

    Daëron, M., Blamart, D., Peral, M. & Affek, H. P. Absolute isotopic abundance ratios and the accuracy of Δ47 measurements. Chem. Geol. 442, 83–96 (2016).

    Google Scholar 

  63. 63.

    van Dijk, J., Fernandez, A., Müller, I. A., Lever, M. & Bernasconi, S. M. Oxygen isotope fractionation in the siderite-water system between 8.5 and 62 °C. Geochim. Cosmochim. Acta 220, 535–551 (2018).

    Google Scholar 

  64. 64.

    Fick, S. E. & Hijmans, R. J. Worldclim 2: new 1-km spatial resolution climate surfaces for global land areas. Int. J. Climatol. 37, 4302–4315 (2017).

    Google Scholar 

  65. 65.

    GLOBE Task Team et al. (eds) The Global Land One-kilometer Base Elevation (GLOBE) Digital Elevation Model v.1.0 (National Oceanic and Atmospheric Administration National Geophysical Data Center, 1999);

  66. 66.

    Bowen, G. J. The Online Isotopes in Precipitation Calculator v.3.1 (2018);

  67. 67.

    White, T., Gonzalez, L., Ludvigson, G. & Poulsen, C. Middle Cretaceous greenhouse hydrologic cycle of North America. Geology 29, 363–366 (2001).

    Google Scholar 

  68. 68.

    van Hinsbergen, D. J. J. et al. A paleolatitude calculator for paleoclimate studies. PLoS ONE 10, e0126946 (2015).

    Google Scholar 

  69. 69.

    Torsvik, T. H. et al. Phanerozoic polar wander, palaeogeography and dynamics. Earth Sci. Rev. (2012).

  70. 70.

    Bowen, G. J. & Revenaugh, J. Interpolating the isotopic composition of modern meteoric precipitation. Water Resour. Res. 39, 1299 (2003).

    Google Scholar 

  71. 71.

    Sunderlin, D., Loope, G., Parker, N. E. & Williams, C. J. Paleoclimatic and paleoecological implications of a Paleocene–Eocene fossil leaf assemblage, Chickaloon Formation, Alaska. Palaios 26, 335–345 (2011).

    Google Scholar 

  72. 72.

    Wolfe, A. P. et al. Pristine early Eocene wood buried deeply in kimberlite from northern Canada. PLoS ONE 7, e45537 (2012).

    Google Scholar 

  73. 73.

    Seton, M. et al. Global continental and ocean basin reconstructions since 200 Ma. Earth Sci. Rev. 113, 212–270 (2012).

    Google Scholar 

  74. 74.

    Naafs, B. D. A. et al. Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids. Geochim. Cosmochim. Acta 208, 285–301 (2017).

    Google Scholar 

  75. 75.

    Hillel, D. Applications of Soil Physics (Elsevier, 1982).

  76. 76.

    Richard, Z. D., Pollard, D., Kump, L. R. & White, T. S. Anomalously low δ18O values of high-latitude Permo-Triassic paleosol siderite. Palaeogeogr. Palaeoclimatol. Palaeoecol. 492, 26–40 (2018).

    Google Scholar 

  77. 77.

    Suarez, M. B., Gonzalez, L. A. & Ludvigson, G. A. Estimating the oxygen isotopic composition of equatorial precipitation during the mid-Cretaceous. J. Sediment. Res. 80, 480–491 (2010).

    Google Scholar 

  78. 78.

    Ufnar, D. F., González, L. A., Ludvigson, G. A., Brenner, R. L. & Witzke, B. J. The mid-Cretaceous water bearer: isotope mass balance quantification of the Albian hydrologic cycle. Palaeogeogr. Palaeoclimatol. Palaeoecol. 188, 51–71 (2002).

    Google Scholar 

  79. 79.

    White, T., Witzke, B., Ludvigson, G. & Brenner, R. Distinguishing base-level change and climate signals in a Cretaceous alluvial sequence. Geology 33, 13–16 (2005).

    Google Scholar 

  80. 80.

    Ufnar, D. F., González, L. A., Ludvigson, G. A., Brenner, R. L. & Witzke, B. J. Stratigraphic implications of meteoric sphaerosiderite δ18O values in paleosols of the Cretaceous (Albian) Boulder Creek Formation, NE British Columbia foothills, Canada. J. Sediment. Res. 71, 1017–1028 (2001).

    Google Scholar 

  81. 81.

    Ufnar, D. F., Ludvigson, G. A., González, L. A., Brenner, R. L. & Witzke, B. J. High latitude meteoric δ18O compositions: paleosol siderite in the middle Cretaceous Nanushuk Formation, North Slope, Alaska. Geol. Soc. Am. Bull. 116, 463–473 (2004).

    Google Scholar 

  82. 82.

    Ufnar, D. F., Ludvigson, G. A., González, L. & Gröcke, D. R. Precipitation rates and atmospheric heat transport during the Cenomanian greenhouse warming in North America: estimates from a stable isotope mass-balance model. Palaeogeogr. Palaeoclimatol. Palaeoecol. 266, 28–38 (2008).

    Google Scholar 

  83. 83.

    Lollar, J. C. Probing a Paleoclimate Model–Data Misfit in Arctic Alaska from the Cretaceous Greenhouse World. PhD dissertation, Univ. Kansas (2011).

  84. 84.

    Robinson, S. A., Scotchman, J. I., White, T. S. & Atkinson, T. C. Constraints on palaeoenvironments in the lower Cretaceous Wealden of southern England, from the geochemistry of sphaerosiderites. J. Geol. Soc. Lond. 167, 303–311 (2010).

    Google Scholar 

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We thank M. Jaggi and S. Bishop for assistance in the laboratory. We thank PAREX resources and G. Tellez for allowing sampling, and G. Bayona for identifying the siderite in the sample from Cuervos, Colombia. We thank G. Suan, J. Schnyder and F. Baudin for providing the sample from Arctic Siberia. We thank M. Dechesne, E. D. Currano, R. Dunn and L. E. Schmidt for providing the sample from the Hanna Basin. We thank R. Peters for assistance with the WorldClim-2 and Digital Elevation Model data. We thank D. J. J. van Hinsbergen for assistance with the palaeolatitudes. We thank C. Jaramillo, K. Snell, J. Kelson, E. Middlemas, D. Colwyn, T. Kukla and R. Wills for internal discussions. We acknowledge financial support through ETH project ETH-33 14-1 and Swiss SNF project 200021_169849.

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T.W. and S.M.B. designed the study. J.v.D. wrote the manuscript. J.v.D., A.F. and S.M.B. developed the method for siderite analysis and J.v.D. and A.F. performed the measurements. S.R.P. provided the Faroese sample. T.W. provided most of the other samples. All authors contributed to discussions and editing of the final manuscript.

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Correspondence to Joep van Dijk.

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Extended data

Extended Data Fig. 1 Paleo-geographic map of the Paleocene/Eocene Thermal Maximum (56 Ma) with study sites.

Siderite bearing paleosols (red stars) and previous latest Paleocene/ earliest Eocene study sites (yellow circles; Supplementary Data 2). 1) Cerrejon and Cuervos, Colombia, 2) Elgin and McQueeney, Texas, 3) Pruden mine, Arkansas, 4) Alberhill, California, 5) Calhan, Colorado, 6) Hanna basin, Wyoming, 7) Black diamond, Washington State, 8) Prince of Wales Island, Alaska, 9) Paris basin, France, 10) Faroe Islands, 11) Faddeevsky Island, Russia. Light-grey gridlines represent latitudes and longitudes, with 30° spacing. The map was generated with GPlates® using the rotation frame and tectonic reconstruction of ref. 73.

Extended Data Fig. 2 Schematic on the formation of pedogenic siderite spherules and their proxy information.

Pedogenic siderite forms in permanently waterlogged soils with high organic matter content. From top left to bottom right: 1) Oxygen isotopes in precipitation percolate down into the soil and get incorporated into the dissolved inorganic carbon pool. 2) Bacterial dissimilatory iron reduction in the anoxic soil produces aqueous CO2 and ferrous iron (Fe2+). 3, 4) Pedogenic siderite precipitates in the soil pore spaces under the supersaturation of dissolved inorganic carbon and Fe2+ recording the soil groundwater temperature, the oxygen isotope composition of precipitation and the carbon isotope composition of the soil groundwater (reflective of the dominant soil redox pathway). 5) Clumped isotope-based soil groundwater temperature can be related to the surface air temperature. 6) Oxygen isotope composition of siderite can be related to the oxygen isotope composition of precipitation.

Extended Data Fig. 3 Physical soil temperature depth model in a typical siderite-bearing soil.

We consider a one-meter thick lignite74 overlaying a waterlogged clay horizon and a seasonality of 10 °C at the soil surface. Soil physical properties are taken from ref. 75. Based on the model, the maximum siderite formation temperature at a depth of one meter, just below the A-horizon, can only be slightly biased towards the temperature of the warmest months even if the siderite forms in the summer due to high rates of microbial organic matter degradation. The uncertainty of the clumped isotope-based formation temperature overlaps the mean annual temperature at a soil depth of one meter.

Extended Data Fig. 4 Latest Paleocene/ earliest Eocene siderite-bearing paleosols in California.

Ione Fm. at Ione, California (a) and siderite-bearing paleosol at Alberhill, California (bf). Siderite-bearing horizon at Alberhill with patches of siderite spherules (e) and fossilized roots (d) is located roughly one meter below overlying A-horizon (c, b, f).

Extended Data Fig. 5 Latest Paleocene/ earliest Eocene (LPEE) siderite continental temperatures in comparison to the present-day.

Reconstructions are compared to present-day temperatures at the respective sites or the longitudinal range of present-day temperatures considering the 2σ uncertainty in clumped isotope-based temperatures. We compared the Colombian, southern Alaskan and Siberian reconstructions to the entire present-day longitudinal range of temperatures (circles and dashes lines). Other reconstructions are compared to the respective temperature at the site in the present-day (stars), with the exception of the sites in Wyoming and Colorado that are currently located at high altitude. Black represents comparisons to present-day mean annual temperature and red represents comparisons to present-day temperature of the warmest months, considering the summer-bias in high latitude temperatures.

Extended Data Fig. 6 Compilation of all late Paleocene/ early to middle Eocene continental temperatures without elevation filter.

Yellow stars: siderite Δ47 (this study), green circles: fossil flora, orange triangles: paleosol weathering climofunctions, blue diamonds: MBT’-CBT, purple plus signs: tooth-enamel δ18O, red triangle: goethite δ18O, blue cross: cellulose δ18O, blue hexagons: calcite Δ47 (see Pangaea database). Faint symbols represent the late Paleocene or early/ middle Eocene. Open symbols are from elevations above 200 meters above sea level. Shaded grey represents present-day mean annual temperature and cross-hatched grey represents the present-day temperature of the warmest months.

Extended Data Fig. 7 Super-greenhouse siderite oxygen isotope (δ18O) records.

Latest Paleocene/ earliest Eocene, late Permian/ early Triassic and Albian/ Cenomanian siderite δ18O records76,77,78,79,80,81,82,83,84 show a similar decrease from the tropics to the polar latitudes. Black dashed line is symmetrical with the center at 0 ° and drawn to depict the main features of the datasets.

Supplementary information

Supplementary Information

Supplementary discussion, Figs. 1–11 and Table 1.

Supplementary Data 1

Oxygen and deuterium isotope records presented in Figs. 2 and 3a.

Supplementary Data 2

Temperature records presented in Fig. 1.

Supplementary Data 3

Siderite-based temperature reconstructions presented in Fig. 1.

Supplementary Data 4

Siderite microprobe measurements discussed in the Supplementary Information.

Supplementary Data 5

LPEE saturation vapour pressures presented in Fig. 3b.

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van Dijk, J., Fernandez, A., Bernasconi, S.M. et al. Spatial pattern of super-greenhouse warmth controlled by elevated specific humidity. Nat. Geosci. 13, 739–744 (2020).

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