Project highlights

  • Combine state-of-the-art climate and land surface modelling with reconstructed climate and CO2
  • Produce policy-relevant estimate of the Earth System sensitivity


Anthropogenic emissions of greenhouse gases cause the climate to warm. The amount of warming for a doubling of atmospheric carbon dioxide levels (CO2) is denoted the climate sensitivity and is a key metric of global change. However, despite years of research, this quantity remains only loosely constrained by observations and modelling, with a “likely” range of 1.5-4.5°C, but with some newer models suggesting > 5°C . This is because observed warming to date has been driven by a combination of increases in greenhouse gas levels and highly variable aerosol loading among other anthropogenic impacts (e.g. deforestation). Past warm periods provide the opportunity to estimate the Earth System sensitivity (ESS), the longer-term response of the Earth’s climate to elevated greenhouse gas levels. One time period that is particularly relevant is the mid-Pliocene and specifically the mid-Piacenzian warm period (mPWP) around 3.3 million years ago, when CO2 levels were naturally around 400 ppmv, similar to today. To date, uncertainty in reconstructions of past CO2 levels and limited constraints on the spatial patterns of warming have hindered attempts to narrow the uncertainty range on ESS. In this project we will combine the latest reconstructions of pCO2 of the Pliocene with model estimates of other greenhouse gas levels and aerosols and mPWP climate simulations to produce a new palaeoclimate -based estimate of ESS.


University of Birmingham


  • Climate and Environmental Sustainability


Project investigator

  • Dr Peter Hopcroft, University of Birmingham




  • Dr Marcus Badger, Open University
  • Dr Kirsty Edgar, University of Birmingham
  • Dr Tom Dunkley-Jones, University of Birmingham

How to apply


New Pliocene CO2 (de la Vega et al 2020), CH4 (Hopcroft et al 2020) and temperature reconstructions (Salzmann et al 2013, Foley & Dowsett, 2018, Tierney et at 2019) will provide the basis for estimating the Earth System sensitivity. Temperature reconstructions will first be combined with PlioMIP2 Earth System Model simulations (Haywood et al 2020) to produce multiple realisations of the global Pliocene temperature fields. To date only carbon dioxide and changes in ice-sheets and sea-level have been used (Lunt et al 2010, Martinez-Boti et al 2015). We will make use of new model-based simulations of Pliocene non-CO2 trace gases and aerosols (Hopcroft et al., 2020) to give a complete representation of the radiative forcing agents acting during this warm period. This will allow us to generate a probabilistic estimate of ESS and S, the rate of increase of global mean temperature per unit of radiative forcing.

Training and skills

This project will give the student direct experience of high-performance computing and using state-of-the-art climate and vegetation model simulations. During the project the student will receive training in analysing and evaluating complex systems, in Earth System dynamics and computer programming and mathematical analysis.

Partners and collaboration

This project is jointly supervised between the University of Birmingham and the Open University. Peter Hopcroft (University of Birmingham) brings expertise in modelling climate and Earth System processes, including greenhouse gases such as methane. Marcus Badger (Open University), Kirsty Edgar and Tom Dunkley-Jones (both University of Birmingham) bring expertise in reconstructing climate and carbon dioxide levels of the past, especially for early warm periods.

Further details

Please contact Peter Hopcroft ( or Marcus Badger ( if you have any questions about this studentship.

Applications need to be submitted via the University of Birmingham postgraduate portal,, by midnight 11.01.2021. Please first check whether the primary supervisor is within Geography, Earth and Environmental Sciences, or in Biosciences, and click on the corresponding PhD program on the application page.

This application should include

  • a brief cover letter, CV, and the contact details for at least two referees
  • a CENTA application form
  • the supervisor and title of the project you are applying for under the Research Information section of the application form.

Referee’s will be invited to submit their references once you submit your application, but we strongly encourage applicants to ensure referees are aware of your submission and expecting a reference request from us. Students are also encouraged to visit and explore the additional information available on the CENTA website.

Possible timeline

Year 1

Assemble climate model simulations and use a statistical model to combine these with climate reconstructions to generate probabilistic global temperature reconstruction for the Pliocene.

Year 2

Further develop estimates of non-CO2 radiative forcing, including potentially new land-surface simulations to generate estimates of CH4 emissions and emissions of other biogenic compounds and aerosols.

Year 3

Develop a comprehensive estimate of the Earth System sensitivity parameter combining all other aspects of the project.

Further reading

de la Vega, E. et al (2020). Atmospheric CO2 during the Mid-Piacenzian Warm Period and the M2 glaciation, Scientific Reports, 10, 11002.

Foley K, Dowsett H (2019) Community sourced mid-Piacenzian sea surface temperature (SST) data. U.S. Geological Survey data release, doi: 10.5066/P9YP3DTV.

Haywood A et al.,(2020) A return to large-scale features of Pliocene climate: the Pliocene Model Intercomparison project Phase 2, Climate of the Past, in press,

Hopcroft, P.O. et al (2020). Polar amplification of Pliocene climate by elevated trace gas radiative forcing, Proceedings of the National Academy of Sciences, 117(38), 23401-23407.

Lunt D, et al. (2010) Earth system sensitivity inferred from Pliocene modelling and data. Nature Geosci 3:60–64.

Martinez-Boti M, et al. (2015) Plio-Pleistocene climate sensitivity evaluated using high resolution CO2 records. Nature 518:49–54.

Salzmann U, et al. (2013) Challenges in quantifying Pliocene terrestrial warming revealed by data-model discord. Nature Climate Change 3:969–974.

Tierney, J. et al. (2019). Pliocene warmth consistent with greenhouse gas forcing, Geophysical Research Letters, 46, 9136-9144.


This project does not require fieldwork or other practical activities so should be minimally impacted by any travel restrictions due to the pandemic. Access to high performance computing (HPC) is the main requirement and both local and national facilities have remained open for users during the last year. Interruptions to this project are therefore not foreseen in the near future.