Preprints
https://doi.org/10.5194/egusphere-2023-2702
https://doi.org/10.5194/egusphere-2023-2702
28 Nov 2023
 | 28 Nov 2023

Aerosol uncertainties in tropical precipitation changes for the mid-Pliocene Warm Period

Anni Zhao, Ran Feng, Chris M. Brierley, Jian Zhang, and Yongyun Hu

Abstract. The mid-Pliocene Warm Period (mPWP, 3.3 – 3.0 Ma) was characterised by an atmospheric CO2 concentration exceeding 400 ppmv with minor changes in continental and orbital configurations. Simulations of this past climate state have improved with newer models, but still show some substantial differences from proxy reconstructions. There is little information about atmospheric aerosol concentrations during the Pliocene, but previous work suggests that is could have been quite different from the modern. Here we apply idealised aerosol scenario experiments to examine the importance of aerosol forcing on mPWP tropical precipitation and the possibility of aerosol uncertainty explaining the mismatch between reconstructions and simulations. The absence of industrial pollutants leads to further warming especially in the Northern Hemisphere. The Intertropical Convergence Zone (ITCZ) becomes narrower and stronger and shifts northward after removal of anthropogenic aerosols. Though not affecting the location of monsoon domain boundary, removal of anthropogenic aerosol alters the amount of rainfall within the domain, increasing summer rain rate over eastern and southern Asia and western Africa. This work demonstrates that uncertainty in aerosol forcing could be the dominant driver in tropical precipitation changes during the mid-Pliocene: causing larger impacts than the changes in topography and greenhouse gases.

Anni Zhao, Ran Feng, Chris M. Brierley, Jian Zhang, and Yongyun Hu

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2702', Anonymous Referee #1, 19 Dec 2023
    • AC1: 'Reply on RC1', Anni Zhao, 09 Jan 2024
  • RC2: 'Comment on egusphere-2023-2702', Anonymous Referee #2, 03 Jan 2024
    • AC3: 'Reply on RC2', Anni Zhao, 23 Jan 2024
  • RC3: 'Comment on egusphere-2023-2702', Anonymous Referee #3, 09 Jan 2024
    • AC2: 'Reply on RC3', Anni Zhao, 11 Jan 2024
Anni Zhao, Ran Feng, Chris M. Brierley, Jian Zhang, and Yongyun Hu
Anni Zhao, Ran Feng, Chris M. Brierley, Jian Zhang, and Yongyun Hu

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Short summary
We analyse simulations with idealised aerosol scenarios to examine the importance of aerosol forcing on mPWP precipitation and how aerosol uncertainty could explain the data model mismatch. We find further warming, narrower and stronger ITCZ and monsoon domain rainfall change after removal of industrial emissions. Aerosols have more impacts on tropical precipitation than the mPWP boundary conditions. Our results highlight the importance of prescribed aerosol scenarios in simulating mPWP climate.