Preprints
https://doi.org/10.5194/cp-2021-16
https://doi.org/10.5194/cp-2021-16

  26 Feb 2021

26 Feb 2021

Review status: a revised version of this preprint was accepted for the journal CP and is expected to appear here in due course.

Mid-Pliocene West African Monsoon Rainfall as simulated in the PlioMIP2 ensemble

Ellen Berntell1, Qiong Zhang1, Qiang Li1, Alan M. Haywood2, Julia C. Tindall2, Stephen J. Hunter2, Zhongshi Zhang3,4, Xiangyu Li3, Chuncheng Guo4, Kerim H. Nisancioglu4, Christian Stepanek5,6, Gerrit Lohmann6, Linda E. Sohl7,8, Mark A. Chandler7,8, Ning Tan9,10, Camille Contoux10, Gilles Ramstein10, Michiel L. J. Baatsen11, Anna S. von der Heydt11,12, Deepak Chandan13, William Richard Peltier13, Ayako Abe-Ouchi14, Wing-Le Chan14, Youichi Kamae15, Charles J. R. Williams16,17,18, and Dan Lunt16 Ellen Berntell et al.
  • 1Department of Physical Geography and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
  • 2School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, West Yorkshire, UK
  • 3Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan, China
  • 4NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway
  • 5Institute for Environmental Physics, University of Bremen, Bremen, Germany
  • 6Alfred Wegener Institute - Helmholtz-Zentrum für Polar und Meeresforschung, Bremerhaven, Germany
  • 7Center for Climate Systems Research, Columbia University, New York, USA
  • 8NASA Goddard Institute for Space Studies, New York, USA
  • 9Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
  • 10Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France
  • 11Centre for Complex Systems Science, Utrecht University, Utrecht, The Netherlands
  • 12Institute for Marine and Atmospheric research Utrecht (IMAU), Department of Physics, Utrecht University, Utrecht, The Netherlands
  • 13Department of Physics, University of Toronto, Toronto, Ontario, Canada
  • 14Centre for Earth Surface System Dynamics (CESD), Atmosphere and Ocean Research Institute (AORI), University of Tokyo, Tokyo, Japan
  • 15Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
  • 16School of Geographical Sciences, University of Bristol, Bristol, UK
  • 17NCAS-Climate, University of Reading, Reading, UK
  • 18Department of Meteorology, University of Reading, Reading, UK

Abstract. The mid-Pliocene Warm Period (mPWP; ~3.2 million years ago) is seen as the most recent time period characterized by a warm climate state, with similar modern geography and ~400 ppmv atmospheric CO2 concentration, and is therefore often considered an interesting analogue for near-future climate projections. Paleoenvironmental reconstructions indicate higher surface temperatures, decreasing tropical deserts, and a more humid climate in West Africa characterized by a strengthened West African Monsoon (WAM). Using model results from the second phase of the Pliocene Modelling Intercomparison Project (PlioMIP2) ensemble we analyze changes of the WAM rainfall during the mPWP, by comparing with the control simulations for the pre-industrial period. The ensemble shows a robust increase of the summer rainfall over West Africa and the Sahara region with an average increase of 2.7 mm/day, contrasted by a rainfall decrease over the equatorial Atlantic. An anomalous warming of the Sahara Desert and deepening of the Saharan Heat Low, seen in > 90 % of the models, leads to a strengthening of the WAM and an increased monsoonal flow into the continent. A similar warming of the Sahara Desert is seen in future projections using both phase 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5), and though previous studies of future projections indicate a west/east drying/wetting contrast over Sahel, PlioMIP2 simulations indicate a uniform rainfall increase over Sahel in warm climates characterized by increasing greenhouse gas forcing.

Ellen Berntell et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-16', Anonymous Referee #1, 18 Mar 2021
    • AC1: 'Reply on RC1', Ellen Berntell, 04 Jun 2021
  • RC2: 'Comment on cp-2021-16', Anonymous Referee #2, 06 May 2021
    • AC2: 'Reply on RC2', Ellen Berntell, 04 Jun 2021
  • EC1: 'Eidtor's Comment on cp-2021-16', Martin Claussen, 07 May 2021
    • AC3: 'Reply on EC1', Ellen Berntell, 04 Jun 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-16', Anonymous Referee #1, 18 Mar 2021
    • AC1: 'Reply on RC1', Ellen Berntell, 04 Jun 2021
  • RC2: 'Comment on cp-2021-16', Anonymous Referee #2, 06 May 2021
    • AC2: 'Reply on RC2', Ellen Berntell, 04 Jun 2021
  • EC1: 'Eidtor's Comment on cp-2021-16', Martin Claussen, 07 May 2021
    • AC3: 'Reply on EC1', Ellen Berntell, 04 Jun 2021

Ellen Berntell et al.

Ellen Berntell et al.

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Short summary
The mid-Pliocene Warm Period (~3.2 Ma) is often considered an analogue for near-future climate projections, and model results from the PlioMIP2 ensemble show a robust increase of rainfall over West Africa and the Sahara region compared to pre-industrial conditions. Though previous studies of future projections indicate a west/east drying/wetting contrast over Sahel, these results indicate a uniform rainfall increase over Sahel in warm climates characterized by increased greenhouse gas forcing.