A new study in Nature—proposes a surprising twist on a controversial climate intervention technique: weakening the greenhouse effect by warming the upper atmosphere.
The research explores stratospheric aerosol injection, in which tiny particles are added to the atmosphere to cool the planet. Traditionally, this has meant using reflective particles in the lower stratosphere to bounce sunlight back into space. Soden, He and colleagues modeled a radically different approach—placing light-absorbing aerosols much higher— around 30 kilometers up.
“At that altitude, the aerosols warm a key layer of the atmosphere where carbon dioxide most strongly influences Earth’s heat balance,” said Haozhe He, a postdoctoral researcher at the High Meadows Environmental Institute at Princeton University, and the lead author of the study. “This added warmth causes the planet to radiate more heat into space, effectively reducing the strength of the CO₂ greenhouse effect without removing any carbon dioxide.
“Our results suggest this could be more than ten times as efficient as conventional methods,” said Soden, a professor in the Department of Atmospheric Sciences at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science. “It’s a completely different physical mechanism, and while it’s still theoretical, it opens the door to new lines of research.”
The authors stress that this concept is far from ready for real-world deployment. Delivering particles to such altitudes poses major engineering challenges, and potential environmental side effects including impacts on the ozone layer, circulation patterns, and ice melt, all of which must be carefully assessed.
The findings underscore the importance of examining all scientifically sound options as part of the climate conversation. “There’s no substitute for cutting CO₂ emissions,” Soden said. “But if we’re going to talk about climate intervention, we need to understand every pathway the physics allows.”
For more information about climate engineering, watch this lecture by Brian Soden, presented at the Rosenstiel School’s Sea Secrets Lecture Series on April 17, 2024.
The study titled, Stratospheric aerosol injection can weaken the carbon dioxide greenhouse effect, was published in the journal Nature Communications Environment & Earth on June 20, 2025.
The authors include He, Soden, Gabriel A. Vecchi and Wenchang Yang of Princeton University.
Funding for the study was provided by the Simons Foundation.
