The warm Pliocene: Bridging the geological data and modelling communities
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

On the climatic influence of CO2 forcing in the Pliocene

Lauren Burton1, Alan Haywood1, Julia Tindall1, Aisling Dolan1, Daniel Hill1, and the PlioMIP Participants*
Lauren Burton et al.
  • 1School of Earth and Environment, University of Leeds, United Kingdom (eeleb@leeds.ac.uk)
  • *A full list of authors appears at the end of the abstract

Understanding the dominant climate forcings in the Pliocene is crucial to assessing the usefulness of the Pliocene as an analogue for future climate. Previous research has shown the dominance of CO2 forcing in driving Pliocene surface air temperature change but little is understood about the drivers of other climate parameters.

We implement a novel, simple linear factorisation method to seven models in the PlioMIP2 ensemble to assess the relative influence of CO2 forcing in the Pliocene. Outputs are termed “FCO2” and reflect the relative influence of CO2, where 1 represents wholly dominant CO2 forcing.

CO2 forcing is found to be the dominant driver of surface air temperature change in six of the seven models (global mean FCO2 of ensemble = 0.56), and five of the seven models for sea surface temperature (global mean FCO2 of ensemble = 0.56). FCO2 varies latitudinally for both, with CO2 forcing less dominant at high latitudes.

FCO2 shows the most variation between models for precipitation change (individual model global mean FCO2 range = 0.30-0.69), though CO2 remains the most dominant driver in the ensemble (global mean FCO2 = 0.51). Spatial change in precipitation is predominantly driven by changes in orography and ice sheets in individual models.

The accuracy of our FCO2 method is evidenced by comparison to an energy balance analysis, which also adds nuance to the results and highlights feedbacks that arise from CO2 forcing.

Our results go some way to better understanding the drivers of Pliocene climate and have implications for the interpretation of proxy data and data-model comparison, which is to be investigated further. Our results could also be expanded to include additional climate parameters, such as surface pressure.

That CO2 forcing is the dominant driver of surface air temperature, sea surface temperature and precipitation change suggests that the Pliocene is a relevant climate analogue for the future, but attention must also be paid to the significant effect of non-CO2 forcing in the Pliocene, the equivalent of which is not expected to be seen for hundreds or thousands of years in the future.

PlioMIP Participants:

PlioMIP Participants

How to cite: Burton, L., Haywood, A., Tindall, J., Dolan, A., and Hill, D. and the PlioMIP Participants: On the climatic influence of CO2 forcing in the Pliocene, The warm Pliocene: Bridging the geological data and modelling communities, Leeds, United Kingdom, 23–26 Aug 2022, GC10-Pliocene-60, https://doi.org/10.5194/egusphere-gc10-pliocene-60, 2022.