CR2026_18

Title: Climate impacts of volcanic eruptions under stabilisation and overshoot pathways

Lead Supervisor: Andrea Dittus, Department of Meteorology, University of Reading

Email: a.j.dittus@reading.ac.uk

Co-supervisors: Ed Hawkins, National Centre for Atmospheric Science, University of Reading; Thomas Aubry, University of Oxford; Colin Jones, University of Leeds

UKRI funding only covers Home fees which increase annually. International students may still apply to this project, but will be required to meet the difference between the International and Home student fees themselves. 

The historical record shows that large volcanic eruptions in the 19th and 20th century have had highly significant impacts on the climate system, ranging from substantial regional cooling, to affecting ocean circulation and even causing a shift in the location of the tropical rain bands and affecting the monsoon systems (e.g. Broennimann et al, 2019). Several recent studies have looked at the impact of possible future volcanic eruptions occurring in a warmer world (e.g. Chim et al., 2023), but this area of research remains largely understudied. Emerging evidence shows that in a warmer world, both the realised volcanic forcing as well as its climate impacts could be different from the effects of the same eruption, had the eruption occurred before anthropogenic greenhouse gas emissions caused the climate to warm (e.g. Aubry et al., 2021).

As our warming world gets closer to breaching the 1.5°C target set out by the Paris Agreement with every passing year, climate scientists are increasingly studying so called temperature stabilisation and overshoot scenarios, where a temperature target is temporarily exceeded before being brought back down below a certain temperature limit, or stabilising at a given temperature level once net-zero emissions of greenhouse gases are achieved. A key question of interest to scientists is the question: are the changes observed as the climate warms reversible?

Experimental protocols have been proposed to answer such questions. However, the most common modelling frameworks for studying stabilisation and overshoot simulations use idealised forcing scenarios, often including CO2 emissions as the only external forcing (e.g. Jones et al., 2025). The role of volcanic eruptions in stabilised and overshoot climate simulations is virtually unexplored.

In the first part of this project, novel simulations with a state-of-the-art Earth System Model, UKESM1.2, will be conducted where different types of volcanic eruptions occur during different phases of warming and overshoot simulations, across a range of warming levels (see e.g. Figure 1 for an example of zero emissions simulations). The reference simulations without volcanic eruptions but including all other forcing agents will be provided by supervisor Dittus, and the successful PhD student will re-run portions of the reference simulations with added volcanic eruptions.

This PhD project will answer the following overarching science questions:

How does the physical climate response to volcanic eruptions differ in a stabilisation and overshoot context, compared to traditional climate projections and historical simulations? What are plausible impacts of large future volcanic eruptions for the UK?

To answer the first question, the student will investigate how the atmosphere and ocean circulations respond to volcanic eruptions, and how this response depends on the background climate state such as the level of global warming (e.g. 2°C vs. 4°C). Past research has shown that volcanic forcing under warming and its impacts can be altered due to a) changes in the volcanic plume height and b) changes in ocean stratification, among other many other processes (Aubry et al., 2022). For the climate impacts over Europe, the impacts for a given warming level may also be sensitive to whether they occur concurrently with changes in the ocean circulation, specifically the Atlantic Meridional Overturning Circulation (AMOC). AMOC weakening is a well-known response to greenhouse gas forcing in climate models, and the AMOC is often considered to be a tipping element in the Earth System. Interactions between the AMOC and volcanic eruptions will be studied in this project, both for weakened and stronger AMOC states seen across warming levels.

In the final part of the project, the student will investigate what a large volcanic eruption in a warmer world might mean for the British and Irish Isles. To answer this question, a subset of the volcanic eruptions simulated in the earlier part of the project will be downscaled with a regional climate model, run on the model output generated in year 1 and 2. These higher resolution simulations, typically at a resolution of 12 km, will allow the student to develop storylines of plausible impacts of volcanic eruptions for the UK at different global warming levels. Information will be provided for key variables such as temperature and precipitation changes. To our knowledge, this is a highly novel approach that has not previously applied to volcanic impacts in the UK.

Training opportunities:

This PhD project will involve visits to the Met Office to collaborate with members of the UKESM Core team. The UK-Ireland Climate + CoCentre will fund a research visit to Ireland, to support the development of storylines for volcanic impacts in the UK and Ireland.

Student profile: 

We are looking for an enthusiastic student with a natural science background from subjects like meteorology, physics, environmental/earth science, or mathematics, with demonstrated strong analytical and quantitative skills. An interest in learning about climate modelling and climate physics is expected. The student will also need to have or acquire the necessary programming and data analysis skills required for the analysis of big climate data sets. UKRI funding only covers Home fees which increase annually. International students may still apply to this project, but will be required to meet the difference between the International and Home student fees themselves. 

References

• Aubry, T. J., Staunton-Sykes, J., Marshall, L. R., et al. (2021). Climate change modulates the stratospheric volcanic sulfate aerosol lifecycle and radiative forcing from tropical eruptions. Nature Communications, 12, 4708. https://doi.org/10.1038/s41467-021-24943-7

• Aubry, T. J., Farquharson, J. I., Rowell, C. R., et al. (2022). Impact of climate change on volcanic processes: Current understanding and future challenges. Bulletin of Volcanology, 84, 58. https://doi.org/10.1007/s00445-022-01562-8

• Brönnimann, S., Franke, J., Nussbaumer, S. U., et al. (2019). Last phase of the Little Ice Age forced by volcanic eruptions. Nature Geoscience, 12, 650–656. https://doi.org/10.1038/s41561-019-0402-y

• Chim, M. M., Aubry, T. J., Abraham, N. L., Marshall, L., Mulcahy, J., Walton, J., & Schmidt, A. (2023). Climate projections very likely underestimate future volcanic forcing and its climatic effects. Geophysical Research Letters, 50, e2023GL103743. https://doi.org/10.1029/2023GL103743

• Jones, __., Bossert, I., Dennis, D. P., Jeffery, H., Jones, C. D., Koenigk, T., Loriani, S., Sanderson, B., Séférian, R., Wyser, K., Yang, S., Abe, M., Bathiany, S., Braconnot, P., Brovkin, V., Burger, F. A., Cadule, P., Castruccio, F. S., Danabasoglu, G., Dittus, A., Donges, J. F., Fröb, F., Frölicher, T., Georgievski, G., Guo, C., Hu, A., Lawrence, P., Lerner, P., Licón-Saláiz, J., Otto-Bliesner, B., Romanou, A., Shevliakova, E., Silvy, Y., Swingedouw, D., Tjiputra, J., Walton, J., Wiltshire, A., Winkelmann, R., Wood, R., Yokohata, T., & Ziehn, T. (2025). The TIPMIP Earth system model experiment protocol: Phase 1. EGUsphere [preprint]. https://doi.org/10.5194/egusphere-2025-3604

 

---