Research ArticleCLIMATOLOGY

An early Cambrian greenhouse climate

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Science Advances  09 May 2018:
Vol. 4, no. 5, eaar5690
DOI: 10.1126/sciadv.aar5690

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  • RE: Response to Comment: Overused “greenhouse climate” paradigm: consequence for ancient climate synthesis
    • Thomas W. Wong Hearing, Doctor-Assistant, School of Geography, Geology and the Environment, University of Leicester, UK. British Geological Survey, Keyworth, UK. Curre
    • Other Contributors:
      • Thomas H. P. Harvey, Lecturer in Geoscience, School of Geography, Geology and the Environment, University of Leicester, UK.
      • Mark Williams, Professor of Palaeobiology, School of Geography, Geology and the Environment, University of Leicester, UK.
      • Melanie J. Leng, Science Director for the Stable Isotope Facility & Director of the Centre for Environmental Geochemistry, National Environmental Isotope Facility, British Geological Survey, Keyworth, UK. Centre for Environmental Geochemistry, Schoo
      • Angela L. Lamb, Research Scientist, National Environmental Isotope Facility, British Geological Survey, Keyworth, UK.
      • Philip R. Wilby, Team Leader for Palaeontology, School of Geography, Geology and the Environment, University of Leicester, UK. British Geological Survey, Keyworth, UK.
      • Sarah E. Gabbott, Professor of Palaeobiology, School of Geography, Geology and the Environment, University of Leicester, UK.
      • Alexandre Pohl, Postdoctoral Researcher, Aix Marseille Univ, CNRS, IRD, Coll France, CEREGE, Aix-en-Provence, France.
      • Yannick Donnadieu, Directeur de Recherche, Aix Marseille Univ, CNRS, IRD, Coll France, CEREGE, Aix-en-Provence, France.

    We thank Landing and Geyer for their comments concerning the interpretive framework of our paper (1), which discuss three main topics: (a) early Cambrian paleocontinental configurations, (b) the application of a ‘greenhouse paradigm’, and (c) the relationship between calcite/aragonite seas and CO2 concentration. These points are addressed in detail below, but in summary: although drastically different early Cambrian paleogeographies can be considered, all place Avalonia at high southern paleolatitudes; dissolved CO2 concentration in the oceans is not the dominant control on calcite/aragonite seas; and the early Cambrian climate was in a greenhouse, not an icehouse, state comparable to late Mesozoic and early Cenozoic greenhouse climates.

    The suggestion of an alternative paleocontinental configuration for the early Cambrian -highlights one of the major uncertainties inherent in studying ancient paleoclimates. The paleocontinental configuration we have employed here is derived from paleomagnetic and paleobiogeographic data, along with a parsimonious assumption of kinematic consistency between neighbouring time slabs (2). This suite of paleocontintental configurations is widely used in early Paleozoic paleontological and paleoclimate studies (3–7). Furthermore, this is one of a range of similar paleocontinental configurations, supported by paleomagnetic and paleobiogeographic (e.g. 2, 8–10) data, that place either the North African or South American sectors of Gondwana...

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    Competing Interests: None declared.
  • RE: Overused “greenhouse climate” paradigm: consequence for ancient climate synthesis
    • Ed Landing, State Paleontologist, emeritus, New York State Museum
    • Other Contributors:
      • Gerd Geyer, Research Scientist, Universitaet Wuerzburg

    Ed Landing, New York State Museum,
    Gerd Geyer, Universität Würzburg

    Hearing et al. (1) determine a precise sea-surface temperature from late in the diversification of metazoans. However, we contend their global climate synthesis reflects an unquestioning application of the “greenhouse paradigm,” a problematical paleogeographic reconstruction, and an extremely high pCO2 incompatible with marine carbonate deposition of that time.

    Earth’s temperature controls include, in part, geologically episodic to persistent changes in atmospheric greenhouse gas content, Milankovitch cycles, solar luminosity, and plate tectonic activity that can move a continent over a pole where it becomes glaciated or develop restricted polar seas (i.e., Arctic Ocean) (2). Other factors, including global changes in albedo, insolation, and continent distribution, have received little discussion in climate syntheses. Thus, while Arctic Ocean ice melt has increased global warming the rate by c. 25% in the last 30 years (e.g., 3), the driving factors of lower albedo and increased insolation are unnoted in important discussions that focus only on greenhouse gas determination of global temperature (e.g., 4). Similarly, major eustatic (i.e., global sea level) changes, with offlap and subaerial exposure of reflective continents resulting in higher albedo and transgression by shallow seas meaning increased insolation, along with changes in the latitudinal distribution of continents, have been...

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    Competing Interests: None declared.

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