Ancient siderites reveal hot and humid super-greenhouse climate

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Joep van Dijk , Alvaro Bremer Fernandez , Stefano M Bernasconi, Jeremy Caves-Rugenstein, Simon R Passey, Tim White


Earth’s climate is warming as the rise in atmospheric CO2 (pCO2) contributes to increased radiative forcing. State-of-the-art models calculate a wide range in Earth’s climate sensitivities due to increasing pCO2, and, in particular, the mechanisms responsible for amplification of high latitude temperatures remain highly debated. The geological record provides a means to evaluate the consequences of high radiative forcing on Earth’s climate. Here we present clumped (Δ47) and oxygen (δ18O) isotope data from latest Paleocene/earliest Eocene (LPEE; 57-55 million years ago) pedogenic siderites, a time when pCO2 peaked between 1400 and 4000 ppm. Continental mean annual temperature reached 41 °C in the equatorial tropics, and summer temperatures reached 23 °C in the Arctic. Reconstruction of the oxygen isotopic composition of precipitation reveal that the hot LPEE climate was characterized by a globally averaged increase in specific humidity with a corresponding increase in the average residence time of atmospheric moisture and a decrease in the subtropical-to-polar specific humidity gradient compared to the present-day. Pedogenic siderite data from other ancient super-greenhouse periods support the evidence that with higher global mean temperatures and a decreased meridional temperature gradient the increase in specific humidity is subject to polar amplification.



Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics


climate, clumped isotopes, eocene, hydrological cycle, oxygen isotopes in precipitation, paleocene, siderite


Published: 2020-06-10 10:33

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CC BY Attribution 4.0 International

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Supplemental data will be made openly accessible once the manuscript is published

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