Simulation of the mid-Pliocene Warm Period using HadGEM3: experimental design and results from model–model and model–data comparison

Williams, Charles J. R., Sellar, Alistair A., Ren, Xin, Haywood, Alan M., Hopcroft, Peter, Hunter, Stephen J., Roberts, William, Smith, Robin S., Stone, Emma J., Tindall, Julia C. and Lunt, Daniel J. (2021) Simulation of the mid-Pliocene Warm Period using HadGEM3: experimental design and results from model–model and model–data comparison. Climate of the Past, 17 (5). pp. 2139-2163. ISSN 1814-9332

cp-17-2139-2021.pdf - Published Version
Available under License Creative Commons Attribution 4.0.

Download (19MB) | Preview
Official URL:


Here we present the experimental design and results from a new mid-Pliocene simulation using the latest version of the UK's physical climate model, HadGEM3-GC31-LL, conducted under the auspices of CMIP6/PMIP4/PlioMIP2. Although two other palaeoclimate simulations have been recently run using this model, they both focused on more recent periods within the Quaternary, and therefore this is the first time this version of the UK model has been run this far back in time. The mid-Pliocene Warm Period, ∼3 Ma, is of particular interest because it represents a time period when the Earth was in equilibrium with CO2 concentrations roughly equivalent to those of today, providing a possible analogue for current and future climate change.

The implementation of the Pliocene boundary conditions is firstly described in detail, based on the PRISM4 dataset, including CO2, ozone, orography, ice mask, lakes, vegetation fractions and vegetation functional types. These were incrementally added into the model, to change from a pre-industrial setup to a Pliocene setup.

The results of the simulation are then presented, which are firstly compared with the model's pre-industrial simulation, secondly with previous versions of the same model and with available proxy data, and thirdly with all other models included in PlioMIP2. Firstly, the comparison with the pre-industrial simulation suggests that the Pliocene simulation is consistent with current understanding and existing work, showing warmer and wetter conditions, and with the greatest warming occurring over high-latitude and polar regions. The global mean surface air temperature anomaly at the end of the Pliocene simulation is 5.1 ∘C, which is the second highest of all models included in PlioMIP2 and is consistent with the fact that HadGEM3-GC31-LL has one of the highest Effective Climate Sensitivities of all CMIP6 models. Secondly, the comparison with previous generation models and with proxy data suggests a clear increase in global sea surface temperatures as the model has undergone development. Up to a certain level of warming, this results in a better agreement with available proxy data, and the “sweet spot” appears to be the previous CMIP5 generation of the model, HadGEM2-AO. The most recent simulation presented here, however, appears to show poorer agreement with the proxy data compared with HadGEM2 and may be overly sensitive to the Pliocene boundary conditions, resulting in a climate that is too warm. Thirdly, the comparison with other models from PlioMIP2 further supports this conclusion, with HadGEM3-GC31-LL being one of the warmest and wettest models in all of PlioMIP2, and if all the models are ordered according to agreement with proxy data, HadGEM3-GC31-LL ranks approximately halfway among them. A caveat to these results is the relatively short run length of the simulation, meaning the model is not in full equilibrium. Given the computational cost of the model it was not possible to run it for a longer period; a Gregory plot analysis indicates that had it been allowed to come to full equilibrium, the final global mean surface temperature could have been approximately 1.5 ∘C higher.

Item Type: Article
Additional Information: Funding information: This research has been supported by the UK Natural Environment Research Council (NERC)-funded SWEET project (research grant no. NE/P01903X/1), the European Research Council under the European Union's Seventh Framework Programme (FP/2007-868 2013) (ERC grant agreement no. 340923 (TGRES)), the Met Office Hadley Centre Climate Programme funded by BEIS and Defra, the 4D-REEF project receiving funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie research (grant no. 813360 (4D_REEF)), a University of Birmingham Fellowship, the NERC national capability grant for the UK Earth System Modelling (UKESM) project (research grant no. NE/N017951/1), and the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) (ERC grant agreement no. 278636 (PLIO-ESS)).
Subjects: F600 Geology
F800 Physical and Terrestrial Geographical and Environmental Sciences
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: Elena Carlaw
Date Deposited: 19 Nov 2021 16:57
Last Modified: 19 Nov 2021 17:00

Actions (login required)

View Item View Item


Downloads per month over past year

View more statistics