Detecting the benefits of climate mitigation across the Earth system

Background

The effects of climate change are evident in the cryosphere, biosphere, oceans and atmosphere. Climate policy is focused on delivering rapid greenhouse gas emission reductions with the goal of stabilising global temperature. Once emissions peak, scientists will need to provide evidence of policy effectiveness to enable up-to-date climate risk assessments. Short-term climate trends are influenced by internal climate variability, which presents a source of uncertainty in interpreting observations in the context of climate mitigation. Due to ocean thermal inertia, a slowdown in global warming could only be detected from the noise of internal variability several decades after emissions peak. However, lower uncertainty in tracking the effect of mitigation could come from combining geophysical signals with higher signal-to-noise ratios. The aim of this project is to reduce uncertainty in detecting climate mitigation and enable policymakers to have greater confidence in policy effectiveness.

PhD Opportunity

There is a need to identify where the geophysical signals of greenhouse gas emission reductions will first emerge with low uncertainty in the Earth system to provide timely, robust information to policymakers. This project will identify components of the Earth system with high signal-to-noise ratios and use signal processing and optimisation methods to combine data in order to reduce uncertainty in where and when altered climate trends will be detectible under decreasing greenhouse gas emissions. This is novel as many studies only consider signals in individual climate system components, without attempting to combine them to provide more robust detection of climate trends. Some example goals of the project include:
1) Characterise current changes in the climate system and their uncertainty characteristics using observation data.
2) Use the outputs from 1) to develop uncertainty optimised combinations of observable quantities that could detect a mitigation signal.
3) Quantify projected trends in these optimised quantities and their detectability under different climate mitigation scenarios, including after net zero emissions.
Goal 1 can be achieved via comparisons of Earth system model simulations to observed trends. Goals 2-3 can be achieved through analysis of Earth system model simulations.
The results will inform policymakers and support public understanding and communication, setting expectations for attributing the benefits of mitigation. The work will also have relevance to informing which observational platforms are needed to ensure that Essential Climate Variables of key climate relevant quantities are continued – this is critical at a time where the future availability of some observational datasets is uncertain. You will work alongside your supervisors at the University of Leeds and the UK Met Office and have the opportunity to visit the Met Office and engage with researchers in both the Climate Monitoring Group and Climate Processes and Projections Group.

Applicant Profile

The project would ideally suit a student with a background in physics, mathematics, statistics, meteorology, geoscience or natural sciences. Some prior experience of data analysis and computer programming would be beneficial.

Other Information

Marotzke J. Quantifying the irreducible uncertainty in near-term climate projections. WIREs Clim Change. 2019; 10:e563. https://doi.org/10.1002/wcc.563

King, A. D., Ziehn, T., Chamberlain, M., Borowiak, A. R., Brown, J. R., Cassidy, L., Dittus, A. J., Grose, M., Maher, N., Paik, S., Perkins-Kirkpatrick, S. E., and Sengupta, A.: Exploring climate stabilisation at different global warming levels in ACCESS-ESM-1.5, Earth Syst. Dynam., 15, 1353–1383, https://doi.org/10.5194/esd-15-1353-2024

Mauritsen, T., Tsushima, Y., Meyssignac, B., Loeb, N. G., Hakuba, M., Pilewskie, P., et al. (2025). Earth’s energy imbalance more than doubled in recent decades. AGU Advances, 6, e2024AV001636. https://doi.org/10.1029/2024AV001636

Romanzini-Bezerra, G., Maycock, A.C. Projected rapid response of stratospheric temperature to stringent climate mitigation. Nat Commun 15, 6590 (2024). https://doi.org/10.1038/s41467-024-50648-8