As Earth warms past 1.5°C, scientists are testing whether deliberately dimming sunlight or brightening clouds could buy the planet time. This project evaluates four controversial solar radiation management (SRM) strategies that aim to reflect more sunlight back into space, cooling the climate directly rather than cutting emissions. Current models cannot reliably predict whether these approaches would work, where they would have unintended side effects, or how they compare in risk. The researchers will run Earth system model simulations for each method: thinning high clouds that trap heat, brightening marine clouds over the Mediterranean, flooding sea ice to increase its reflectivity, and injecting cellulose nanocrystals—a biodegradable material—into the stratosphere as an alternative to sulphate aerosols. If successful, the project will produce the first direct comparison of these four strategies under the same climate scenarios, including what happens if temperatures temporarily overshoot 1.5°C. The final work package will deliver a risk-risk analysis for policymakers, showing trade-offs between cooling effectiveness, regional disruption, and stratospheric ozone damage. This is fundamental science with immediate policy relevance: without such evidence, decisions about whether to deploy SRM would rest on guesswork rather than data.
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This research will evaluate the climatic impacts of four solar radiation management (SRM) approaches: three focused on solar or terrestrial radiation and one examining cellulose nanocrystals (CNCs) for stratospheric aerosol injection (SAI). We will assess these approaches across various temperature scenarios, including the critical 1.5°C threshold and potential overshoot, analysing their effects on radiative forcing, temperature changes, and associated risks. By selecting scenarios based on future projections, our goal is to deliver a comprehensive assessment of the effectiveness and risks of these SRM methods. With increasing evidence of a warming planet and its impacts on temperature and precipitation extremes, there is an urgent need to explore whether deliberate climate interventions can mitigate severe effects on human populations and ecosystems. This project utilises Earth System Models to deepen our understanding of the cooling potential of each SRM approach across the work packages. Work Package 1 will focus on reducing uncertainty in cloud thinning for cooling by integrating observational data to refine climate model simulations. Work Package 2 will analyse climate model outputs related to Marine Sky Brightening over the Mediterranean Sea, assessing its regional cooling effects and its ability to mitigate extreme warming impacts while minimising teleconnections to other areas. Work Package 3 will conduct targeted computational experiments to evaluate the impact of sea ice flooding on climate and environmental dynamics, aiming to establish how albedo modification (due to a change in ice cover) will impact the solar radiation budget. Work Package 4 will be the first to study the effects of injecting cellulose nanocrystals for solar radiation management, developing a new parameterization of their optical scattering properties within the UKESM-1 climate model. This will enable a comprehensive assessment of their global climate impacts and stratospheric ozone effects as a potential SAI material. The project will culminate in Work Package 5, which aims to integrate the findings from all previous work packages into a cohesive framework. This package will produce a comprehensive report summarising the outcomes of each work package, along with actionable recommendations on how and where to implement the SRM approaches. It will prioritise the key insights gained, assess associated risks, and highlight the potential benefits of each strategy. Additionally, Work Package 5 will include a risk-risk analysis to evaluate and compare the different risks associated with each option, helping to identify trade-offs and informing decision-making. By synthesising the data and analyses from the earlier stages, this package will provide stakeholders with a clear understanding of the implications of these SRM techniques, guiding informed choices for climate intervention efforts. We bring a wealth of multidisciplinary expertise in climate science, modelling, and environmental policy that is crucial for executing this project effectively. We have extensive experience in atmospheric science and risk assessment, ensuring a well-rounded understanding of both the technical and socio-economic aspects of SRM strategies. We have successfully collaborated on similar projects, demonstrating our ability to manage complex research initiatives and deliver impactful results. Our collective knowledge and skills will enable us to navigate the challenges of this project and foster informed decision-making in climate intervention.
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