New research will model the risks and impact of using solar radiation modification (SRM) to build understanding of the radical process and address evidence gaps.
The UK government is committed to delivering net zero and tackling the underlying causes of climate change.
However, as climate impacts increase globally, there is increased attention on radical intervention measures to control temperatures, including SRM, a process in which some radiation from the Sun is reflected back into space.
There is currently insufficient knowledge of the impact these interventions might have on the Earth's system if they are ever deployed at scale, and how this would affect regional climate, humans and ecosystems.
There are also uncertainties around the effectiveness of some proposed SRM approaches.
The Natural Environment Research Council will invest £10 million in four research projects, launching in April, that aim to address these gaps in our understanding.
These projects will not deploy SRM in the real world.
Using computer modelling research and historical data-driven research only, the five-year studies will investigate the impact of:
- Stratospheric aerosol intervention - the process of adding particles into the atmosphere that will reflect the Sun's rays.
- Marine cloud brightening - this technique aims to increase the reflectivity of clouds over the ocean by spraying sea water to create more cloud condensation nuclei.
- How the environment might respond to SRM by comparing to real world natural analogues such as volcanic eruptions and changes in shipping emissions.
- The cooling potential of four less well-known SRM approaches - three focused on solar or terrestrial radiation and one examining the use of tiny, rod-like nanoparticles (cellulose nanocrystals) derived from natural cellulose sources to enhance the effectiveness of stratospheric aerosol intervention.
The programme aligns with the UK Government's position on SRM, which is that the UK is not deploying SRM and has no plans to do so. The UK continues to invest in modelling studies to better understand the impacts of SRM deployment.
The research aims to deliver independent risk-risk analyses to inform policymakers on the potential environmental impacts of SRM.
NERC, with support from Sciencewise, is also commissioning a public dialogue to engage a diverse group and understand what public views and considerations are on SRM.
Professor Louise Heathwaite, Executive Chair of the Natural Environment Research Council, said: "NERC invests in a wide range of research to tackle, adapt to, and mitigate climate change. The UK's priority is to tackle the root cause of climate change by reducing emissions of greenhouse gases from human activities and adapting to those impacts that are unavoidable.
"However, with the increased interest internationally in solar radiation modification measures, there is a pressing need to consider the impact of SRM approaches to control Earth system temperature. These research projects will analyse these approaches in detail and address ethical and governance considerations."
The studies are part of NERC's Modelling environmental responses to solar radiation management programme.
The projects are:
Advancing holistic risk assessment for measures to address climate change – Imperial College London and the universities of Bristol, Leeds and Exeter.
Stratospheric aerosol injection (SAI) is a potential way to reduce global temperature increases from greenhouse gas emissions by reflecting sunlight. While it might mask some global warming its risks and potential effects, including on global society, are not well understood. This project aims to address that by looking at two main challenges.
First, SAI's effects on (e.g.) droughts, air quality, and extreme weather might differ from those of reducing greenhouse gas concentrations. Research is needed to understand these physical impacts and their global distribution.
Second, studies often focus on SAI's physical effects while neglecting social, political, and economic factors – leading to incomplete risk assessments.
The project proposes a new framework combining risk analysis with Earth system modelling. By focusing on key scenarios and their physical impacts while also exploring how the possibility of SAI might affect future decision making, researchers can better assess its risks and benefits alongside other climate measures – and its potential implications for those measures. This will provide more comprehensive and policy-relevant information for future climate decisions.
MACLOUD (Marine CLOUD Brightening) – the universities of Exeter, Leeds, Reading, Manchester and Oxford.
MACLOUD aims to model the potential of marine cloud brightening (MCB) to combat climate change. MCB proposals involve spraying seawater to create tiny sea-salt particles that brighten clouds, reflecting more sunlight and cooling the planet. However, the effectiveness and impacts of MCB are uncertain.
To understand MCB's effects, MACLOUD will use various models to simulate the process from small-scale aerosol formation to large-scale climate impacts to simulate how aerosols evolve, form cloud droplets, and influence cloud behaviour and weather patterns. The project will also consider different climate scenarios and deployment strategies to assess MCB's potential benefits and risks.
By integrating results from detailed aerosol and cloud models with global climate models, MACLOUD aims to provide a comprehensive understanding of MCB's feasibility and its role in mitigating climate change. The project will also study how MCB might affect critical Earth systems like the Amazon, crop productivity, and sea-ice.
Quantifying efficacy and risks of solar radiation management approaches using natural analogues (QUESTION) – the universities of Birmingham and Edinburgh, and the Center for International Climate and Environmental Research, Norway,
NASA and the UK Met Office have confirmed that 2024 was the first year that global temperatures reached +1.5°C higher than pre-industrial levels. Whilst a temperature rise of 1.5°C for a single year doesn't mean that we have breached our commitments under the Paris Agreement (as global warming is an average over decades), it is a strong warning signal that we are getting closer.
To address this, some countries are considering solar radiation modification (SRM) methods to artificially cool the Earth by reflecting more sunlight back into space, buying time for global decarbonisation.
The main SRM methods are stratospheric aerosol intervention (SAI), which creates a protective aerosol layer, and marine cloud brightening (MCB), which increases cloud reflectivity over oceans.
While these methods could slow warming, their effectiveness and side-effects, such as ozone depletion and altered weather patterns, are uncertain.
The QUESTION project aims to study SRM using natural analogues like volcanic eruptions and changes in ship emissions.
It will address challenges in mimicking SRM effects, separating SRM signals from other factors, and improving climate models. This research will help assess SRM's risks and benefits, supporting informed climate action.
ECLIPSE: Evaluation of Climate Intervention through novel Potential Strategies – the universities of Cambridge, Exeter and Imperial College London.
This research will evaluate the climatic impacts of four solar radiation modification (SRM) approaches, including cellulose nanocrystals (CNCs) for stratospheric aerosol intervention (SAI).
The project will assess these methods across various temperature scenarios, including the critical 1.5˚C goal, analysing their effects on radiative forcing, temperature changes, and associated risks.
Using Earth System Models, the project will explore the cooling potential of each SRM approach. 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 assess the regional cooling effects of Marine Sky Brightening over the Mediterranean Sea. Work Package 3 will evaluate the impact of sea ice flooding on climate dynamics. Work Package 4 will study the effects of CNCs for SRM.
