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Access : Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era : Nature
Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era
Rosemarie E. Came1, John M. Eiler1, Ján Veizer2, Karem Azmy3, Uwe Brand4 & Christopher R. Weidman5
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
Ottawa-Carleton Geoscience Centre, University of Ottawa, Ottawa, Ontario KIN 6N5, Canada
Department of Earth Sciences, Memorial University of Newfoundland, St Johns, Newfoundland A1B 3X5, Canada
Department of Earth Sciences, Brock University, St Catharines, Ontario L2S 3A1, Canada
Waquoit Bay National Estuarine Research Reserve, Waquoit, Massachusetts 02536, USA
Correspondence to: Rosemarie E. Came1 Correspondence and requests for materials should be addressed to R.E.C. (Email: [email protected]).
Top of pageAbstractAtmospheric carbon dioxide concentrations seem to have been several times modern levels during much of the Palaeozoic era (543248 million years ago), but decreased during the Carboniferous period to concentrations similar to that of today1, 2, 3. Given that carbon dioxide is a greenhouse gas, it has been proposed that surface temperatures were significantly higher during the earlier portions of the Palaeozoic era1. A reconstruction of tropical sea surface temperatures based on the δ18O of carbonate fossils indicates, however, that the magnitude of temperature variability throughout this period was small4, suggesting that global climate may be independent of variations in atmospheric carbon dioxide concentration. Here we present estimates of sea surface temperatures that were obtained from fossil brachiopod and mollusc shells using the carbonate clumped isotope method5an approach that, unlike the δ18O method, does not require independent estimates of the isotopic composition of the Palaeozoic ocean. Our results indicate that tropical sea surface temperatures were significantly higher than today during the Early Silurian period (443423 Myr ago), when carbon dioxide concentrations are thought to have been relatively high, and were broadly similar to today during the Late Carboniferous period (314300 Myr ago), when carbon dioxide concentrations are thought to have been similar to the present-day value. Our results are consistent with the proposal that increased atmospheric carbon dioxide concentrations drive or amplify increased global temperatures1, 6.
What was the source of that increased CO2 concentration?