A Bold Experiment: Safely Testing Solar Radiation Modification to Combat Climate Change
The world is grappling with the consequences of rapid warming, with 2024 marking the first full year more than 1.5C hotter than the 19th-century average. Fossil fuel emissions are projected to reach a new high in 2025, and permanent carbon removal technologies are struggling to keep pace with the scale required. However, researchers are exploring an alternative approach: reflecting sunlight away from Earth.
The concept has been around since the 1960s, when Lyndon B Johnson's science advisers proposed it as a means to cool the planet. In reality, our atmosphere already reflects about 30% of incoming sunlight, and increasing this fraction could strengthen the natural heat shield. However, there are concerns about the feasibility and risks associated with stratospheric aerosol injection (SAI), which involves releasing sulfur dioxide into the upper atmosphere.
Some critics argue that SAI is too risky to study, but experts disagree. Careful research can help determine whether a well-governed approach could reduce harm, particularly for vulnerable populations. In fact, it's essential to surface risks and failure modes early, making reckless proposals less likely to gain traction.
To address these concerns, researchers are proposing a phase-gated program for SAI, similar to the clinical trial framework used in medicine. This would involve several stages, including lab work, computer models, and small-scale outdoor experiments. Phase one would involve releasing tiny amounts of sulfur dioxide at specific altitudes, carefully measuring its evolution, and comparing those observations with model predictions.
The goal is not to deploy SAI immediately but to generate real-world evidence, transparently, before a crisis forces our hand. This requires building the necessary tools, rules, and oversight mechanisms now, rather than later. A new project funded by the UK's Advanced Research and Invention Agency (Aria) is working on developing theoretical foundations for determining the minimum scale at which an outdoor experiment could meaningfully reduce key uncertainties.
Ultimately, small-scale experiments can reduce both scientific uncertainties and political risks. The real danger isn't asking the question; it's waiting too long to learn the answer. By pursuing this bold experiment, researchers can help pave the way for a more responsible decision about SAI's use in the future β a future that may never need to reflect sunlight, but one that should be prepared if necessary.
The world is grappling with the consequences of rapid warming, with 2024 marking the first full year more than 1.5C hotter than the 19th-century average. Fossil fuel emissions are projected to reach a new high in 2025, and permanent carbon removal technologies are struggling to keep pace with the scale required. However, researchers are exploring an alternative approach: reflecting sunlight away from Earth.
The concept has been around since the 1960s, when Lyndon B Johnson's science advisers proposed it as a means to cool the planet. In reality, our atmosphere already reflects about 30% of incoming sunlight, and increasing this fraction could strengthen the natural heat shield. However, there are concerns about the feasibility and risks associated with stratospheric aerosol injection (SAI), which involves releasing sulfur dioxide into the upper atmosphere.
Some critics argue that SAI is too risky to study, but experts disagree. Careful research can help determine whether a well-governed approach could reduce harm, particularly for vulnerable populations. In fact, it's essential to surface risks and failure modes early, making reckless proposals less likely to gain traction.
To address these concerns, researchers are proposing a phase-gated program for SAI, similar to the clinical trial framework used in medicine. This would involve several stages, including lab work, computer models, and small-scale outdoor experiments. Phase one would involve releasing tiny amounts of sulfur dioxide at specific altitudes, carefully measuring its evolution, and comparing those observations with model predictions.
The goal is not to deploy SAI immediately but to generate real-world evidence, transparently, before a crisis forces our hand. This requires building the necessary tools, rules, and oversight mechanisms now, rather than later. A new project funded by the UK's Advanced Research and Invention Agency (Aria) is working on developing theoretical foundations for determining the minimum scale at which an outdoor experiment could meaningfully reduce key uncertainties.
Ultimately, small-scale experiments can reduce both scientific uncertainties and political risks. The real danger isn't asking the question; it's waiting too long to learn the answer. By pursuing this bold experiment, researchers can help pave the way for a more responsible decision about SAI's use in the future β a future that may never need to reflect sunlight, but one that should be prepared if necessary.