the story goes, the Earth was formless and empty, and darkness shrouded the surface of the deep. Several millennia later, an independent scientist named James Lovelock started to ponder this primordial arrangement: He imagined a fictional planet called Daisyworld, carpeted with black and white daisies. The pale flowers reflected the sun, while the dusky ones absorbed light and heat. As the sun’s rays grew more powerful, the balance of blossoms shifted, stabilizing the globe’s temperature.
Influenced by Lovelock and Latham’s ideas about maintaining a stable planetary temperature, a small group of retired physicists and engineers from some of the world’s top tech companies gather here every week with the goal of developing a system that can spray seawater from ships to brighten marine clouds. Affectionately nicknamed the Old Salts, many are in their 70s, some well into their 80s.
The overall picture is much dimmer. Using satellite observations, a September 2022 study published in found that aerosols’ cooling effects, including their interactions with clouds, has decreased by 30 percent since 2000. That essentially amplifies the amount of warming from recent carbon dioxide emissions by as much as half, writes Johannes Quaas, a lead author and a climate scientist at Leipzig University.
Increasingly, they warn of irreversible tipping points—like the looming collapse of the Thwaites glacier—that make it urgent to find new ways to control the crisis. Temperatures have increased so much that a September 2022 paper in the journal predicts that critical planetary functions may be disrupted even if emissions are curtailed. “I hope we never have to use marine cloud brightening,” Doherty says, “but I just don’t see us on a pathway to avoiding dangerous levels of climate warming.
How, precisely, this research will transfer from the lab to an intervention on the ocean is still in the early stages of planning. But the idea is that a Goldilocks-calibrated nozzle, capable of spraying just the right size of salt crystal, would continuously run from a boat positioned under a marine cloud. “To do this at scale, you’d need thousands of ships over a large area,” Doherty points out. “But as long as that system keeps working, you’d have a steady supply of seawater.
In 2021, the National Academies produced a second geoengineering report. This time, there was no hesitation: They recommended the US embark on brightening research and laid out a plan for designing and governing the programs. Chris Field, the director of the Stanford Woods Institute for the Environment, who worked on the report, says the planet’s trajectory has made him “much more open to looking at a broader range of options.