Policy paper

UK government's view on solar radiation modification technologies (SRM)

Published 29 September 2026

Solar radiation modification (SRM)

SRM is defined as a group of technologies that aim to increase the amount of sunlight reflected into space to counter warming due to increasing greenhouse gas concentrations. SRM is also sometimes referred to as solar geoengineering.

The two most commonly researched SRM techniques are:

• Marine cloud brightening (MCB) - a technique which injects aerosol particles, such as sea salt aerosols, into low-altitude clouds in specific ocean regions, which increases cloud droplet numbers, leading to greater reflection of sunlight
• Stratospheric aerosol injection (SAI) - a technique which injects aerosol particles, or the gases that lead to aerosol formation, into the stratosphere to enhance the reflection of sunlight back into space, cooling the planet

The Royal Society’s 2025 independent review of the evidence base of SRM provides an overview of the potential risks, impacts and uncertainties, and identifies where further research is needed to improve understanding.

The Parliamentary Office of Science and Technology has published a briefing on the governance of SRM research.

The UK Government’s position on SRM

The UK Government does not support the deployment of SRM and does not plan to do so. It does not undertake any form of deliberate weather modification.

The government recognises the need to understand the risks and impacts of SRM. It supports responsible research that advances scientific understanding of those risks and impacts and complies with all domestic and international regulations.

The government’s focus is on tackling the underlying causes of climate change by delivering Net Zero and raising international climate mitigation ambition. The priority is to reduce greenhouse gas emissions from human activities and to adapt to the unavoidable impacts of climate change.

Research into cooling technologies does not reduce the urgent need for increased decarbonisation efforts. There is no substitute for decarbonisation. 

Common misconceptions associated with SRM

SRM is sometimes referred to as ‘geoengineering’.  While SRM is a form of geoengineering, aiming to alter the climate at a regional or global level, it is not a form of greenhouse gas removal because none of the proposed approaches remove greenhouse gases, which are the underlying drivers of climate change.

SRM is often confused with weather modification. Unlike SRM which focuses on cooling the planet for a sustained period, weather modification refers to deliberate actions taken to influence weather conditions over local to regional spatial scales and over shorter timeframes (such as days), as outlined by the World Meteorological Organisation Statement on Weather Modification. The UK government does not undertake any form of deliberate weather modification.

Aircraft contrails are sometimes mistaken for evidence of weather modification or SRM. They form when warm, moist aircraft exhaust fumes mix with cold air at altitude and, under certain atmospheric conditions, can persist and spread out to form cirrus-like clouds before disappearing. There is no deliberate spraying of chemicals in the skies over the UK for climate modification.

There is more information on aircraft contrails.

Publicly funded SRM research

This summarises UK publicly funded programmes for SRM research. The research considers physical science, ethics, risks and impacts of SRM. Most of the research is desk-based with a small number of contained, small-scale field research activities planned.

The Advanced Research and Invention Agency (ARIA) Exploring Climate Cooling Programme

Public spending: £56.8 million

Time period: Ongoing, since 2024

ARIA is an autonomous research and development agency sponsored by the Department for Business, Science, Innovation and Trade (DBIST). The Exploring Climate Cooling programme aims to begin gathering critical missing scientific data to better understand potential Earth cooling approaches (including SAI, MCB and Arctic Sea ice thickening) and their impacts.

The focus is on foundational research to understand fundamental scientific processes, including modelling, monitoring and observation and, where necessary, carefully controlled, small-scale outdoor experiments.

The 5 small-scale field trials announced will be subject to independent environmental impact and legal assessments, which will be made publicly available before any outdoor experiment takes place. The trials will be limited in size and scale, time-bound, and designed so that effects dissipate within 24 hours or are fully reversible.

ARIA is not funding experiments that release toxic materials into the environment, large or sustained field trials, or activities that would contribute to the deployment of these approaches.

The Natural Environment Research Council (NERC)

Public spending: £10.5 million

Time period: 2025 to 2030

The NERC programme aims to better understand the environmental risks of different SRM approaches, using only computer modelling and analysis of historic data. The programme includes a public dialogue to understand public views and considerations on SRM.

The Met Office Hadley Centre Climate Programme (MOHCCP)

Public spending: A small part of £21 million per year funding for this programme is dedicated to SRM

Time period: Ongoing, since 2011

The Department for Energy Security and Net Zero (DESNZ) provides HMG oversight of the MOHCCP, which is funded by DBIST.

A small component of the MOHCCP uses climate modelling to explore the implications of SRM deployment alongside other climate interventions and contributes to international assessments through the Geoengineering Modelling Intercomparison Project (GeoMIP).

Co-CREATE

Public spending: Co-funded by UK Research and Innovation (UKRI) (£868,052) and the European Union

Time period: 2024 to 2026

The Co-CREATE project is examining the governance principles and guidelines for responsible SRM research.