The European Union has opened a €35 million tender for research and coordination aimed at detecting rogue attempts to alter the Earth’s atmosphere by blocking out the sun. Horizon Europe, the EU’s research arm, launched the tender on Tuesday.
The project is an early effort to coordinate action on Solar Radiation Modification (SRM), a nascent and controversial set of technologies that could cool the planet if temperatures reach critical tipping points. Its stated purpose is surveillance and response rather than deployment: the tender excludes field experiments to implement the technologies.
The EU said the work should produce a framework capable of identifying outdoor tests and linking them to those responsible. “This robust monitoring framework should be designed to detect and attribute outdoor experiments and deter potential unilateral deployments by private or state actors.”
The concern is that an experiment by one government or company could affect countries far beyond the place where it began. Reflective particles released into the stratosphere would cross national borders. Concerns exist that state and private actors could conduct unsanctioned regional or global climate experiments, with potentially dangerous side effects.
One proposed approach, Stratospheric Aerosol Injection, would place reflective particles in the stratosphere at an altitude of roughly 15–25 kilometres. The idea has a natural precedent: the 1991 eruption of Mount Pinatubo put millions of tonnes of sulphur dioxide into the stratosphere and lowered global average temperatures by roughly 0.5°C for a limited period.
The tender comes as the UN has warned that global temperatures are set to pass the 1.5 degrees Celsius threshold above pre-industrial levels within the next few years. Without changes to current policies, the UN report said temperatures could rise as high as 2.6 degrees. Wildfires, droughts, hurricanes and severe floods are already occurring with increasing frequency as climate change takes effect.
There are few international agreements to control or monitor unilateral efforts to alter the climate. Some scientists have therefore called for an international non-use agreement on solar radiation modification solutions. In May 2026, environment ministers meeting in Luxembourg said large-scale climate interventions carried significant risks for the climate, environment, security and geopolitics.
Research funding is also expanding. Global funding for SRM research nearly tripled in 2025 from the previous year. Stardust Solutions, an Israeli-American company founded in March 2023, has raised $75 million, including a $60 million financing round led by Lowercarbon Capital. The UK’s Advanced Research and Invention Agency has allocated £56.8 million to its Climate Cooling programme.
The tender’s immediate aim is to build the ability to spot and discourage unilateral action in an area where the effects could extend far beyond the actor responsible.
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