Katherine Ricke, a University of California at San Diego sustainability professor, turned to face the roomful of attentive scientists at the American Geophysical Union a few weeks ago. In any other year, she would have been about to break one of climate science’s biggest taboos.
“Geoscientists know very well at this point that solar geoengineering is not a very good substitute for emissions reductions,” she said. “The question that comes next, then, is, Is solar geoengineering a complement to mitigation?”
The answer, she then argued, was yes. While cutting greenhouse gas emissions might bring down the planet’s temperature in the long term, she said, it would not do so immediately. But spraying sulfate aerosols into the stratosphere was pretty cheap, and it could quickly help relieve the planet’s fever. “Solar geoengineering has a rapid but temporary effect on global temperatures, while the effect of emissions reduction is deferred but persistent,” she said.
Ricke went on to ask whether the economics of solar geoengineering made sense — and about its risks. Would it deprive other important efforts of research funding? Probably not. Could it encourage the public to procrastinate on cutting emissions? Maybe yes.
Yet perhaps the presentation’s biggest surprise — for people who have long thought about the issue — was that nobody in the audience of normal climate scientists gasped. Nobody shooed Ricke out of the room or told her that her talk didn’t belong in a session devoted to achieving net zero — that is, to climate mitigation, to reducing carbon pollution, not blotting out its effects.
To get a sense of what American climate scientists are talking about, you can do a lot worse than attending the annual fall meeting of the AGU, where more than 20,000 scientists come to network, present new research, and gossip about their superiors. This year, AGU was held in the cavernous Moscone Center in San Francisco. The arrival of tens of thousands of people immediately broke the city’s post-pandemic downtown; Starbucks ran out of breakfast sandwiches and every restaurant within a quarter mile of the conference site was jammed before the 8:30 a.m. sessions.
AGU is almost always held, for some nonsensical reason, at roughly the same time as the annual United Nations climate conference, and the two events have a lot in common: They are bazaars, free-for-alls, half salon and half trade show, and each way too big for any one person to see. Yet by keen attention to sounds and signals, one can detect a vibe at both events. The vibe of this year’s AGU was clear: Geoengineering is here to stay.
This sincere interest in geoengineering and climate modification represents a broader shift in climate science from observation to intervention. It also represents a huge change for a field that used to regard any interference with the climate system — short of cutting greenhouse gas emissions — as verboten. “There is a growing realization that [solar radiation management] is not a taboo anymore,” Dan Visioni, a Cornell climate professor, told me. “There was a growing interest from NASA, NOAA, the national labs, that wasn’t there a year ago.”
At the highest level, this acceptance of geoengineering shows that scientists have seriously begun to imagine what will happen if humanity blows its goal of cutting greenhouse gas emissions.
Why the sudden embrace of geoengineering? Part of it is that the Intergovernmental Panel on Climate Change has become increasingly insistent that carbon removal is crucial — and opened the door to other once-taboo ideas.
But another part is that climate disasters seem to get bigger and bigger every year, and humanity seems to be growing more and more alarmed about them, yet no country plans to cut emissions fast enough to relieve global warming’s near-term dangers. 2023 was the warmest year in modern human history, but the Paris Agreement’s temperature goals remain far off. “It was always pretty clear that the kind of emissions reduction to stay below 1.5 [degrees Celsius] was never going to happen in any realistic scenario, but there was always a conviction that just by saying it was physically possible, it was going to inspire people into some kind of action,” Visioni said. “2023 has shown this to not be the case.”
Perhaps one more reason is that, for better or worse, geoengineering is already happening. Economists have long argued that stratospheric aerosol injection is so cheap that someone will eventually try to do it. Then, last year, Luke Iseman, a 39-year-old former employee of the startup incubator Y Combinator, claimed to have conducted rogue experiments in western Mexico delivering reflective sulfur molecules to the atmosphere using weather balloons. It’s unclear whether this “move fast and break things”-styled effort actually reflected any meaningful sunlight back into space. What it did do was awaken the Mexican government to a regulatory arbitrage. It responded by banning solar geoengineering.
Yet more serious attempts have been made at bringing geoengineering into the mainstream. In September, the Overshoot Commission, a panel of current and former world leaders — including an influential Chinese adviser and a former Canadian prime minister — recommended that the world begin to seriously study solar geoengineering. And Congress recently mandated that the White House Office of Science and Technology Policy study the technique — although the office’s resulting report also suggested that scientists are still treading carefully around it. Its hilariously curt title: “Congressionally-Mandated Report on Solar Radiation Modification.”
“The way that broader climate intervention has started to move into the mainstream has been kind of astounding,” said Shuchi Talati, a University of Pennsylvania scholar and former Energy Department official. “If you look at AGU of four or five years ago, if there was one [solar radiation management] panel, that was novel,” she told me. But this year, there were more panels and side conversations than ever. “You can feel it in the air that there was more interest.”
Ricke’s was far from the only geoengineering presentation in San Francisco this year. In a packed lunchtime session, Lisa Graumlich, AGU’s president, led a town hall about the organization’s draft proposal on how to research climate intervention ethically. “Are we attempting to play God? Do we have the right to do this? What risks are we willing to accept? Or … do we have the right not to?” Cynthia Scharf, a former UN adviser who helped lead a Carnegie Foundation project on how the world could possibly govern geoengineering, told the room by video conference. The crowd wasn’t exactly rewarded for attending: After every panelist had finished going through their introductions, the audience only had time to ask two questions.
Across the hall, more than 60 people were talking about a different kind of climate intervention. For years, scientists have known that the stability of a few glaciers in West Antarctica could mean the difference between quasi-manageable amounts of sea-level rise this century and a rapid, catastrophic surge. So small groups of glaciologists have now started to ask whether those specific glaciers — such as Thwaites, which holds a quadrillion gallons of water and is larger than Florida — could be engineered or modified somehow to slow their collapse.
Perhaps a berm could be built on the seafloor, in front of each of the glaciers, in order to prevent warm water from eroding them. Or maybe holes could be drilled into the glaciers, allowing the warmth of their subsurface to be vented to the surface. Glacial scientists have already met twice this year — at the University of Chicago and later Stanford — to begin hashing out the idea.
Another approach — using ships to spray ocean water into the atmosphere, thereby brightening clouds and reflecting more sunlight into space — was also the subject of several events. One scholar, Chih-Chieh Jack Chen, showed research suggesting that brightening the clouds over just 5% of the ocean surface could cool the planet enough to meet the world’s temperature targets — but that the climatic ripple effects of doing so might simultaneously raise temperatures in Southeast Asia by even more than what global warming would do alone. Others presented work showing that cloud brightening might accidentally shut down the planet’s westerly trade winds — or even silence the Pacific Ocean’s El Niño oscillation.
Then there were the carbon removal people, who arrived by the tens and who seemed to have graduated to a less controversial (and possibly more remunerative) plane than geoengineering. Most scientists seem to have accepted that carbon dioxide removal, or CDR, will need to happen to at least some degree. “CDR is a given. People don’t even consider it to be geoengineering any more, which is what the CDR people have always wanted,” Visioni told me. A new Department of Energy report, released during the conference, argues that by 2050, the United States might be able to suck 1 billion tons of carbon dioxide out of the atmosphere for a mere $130 billion a year, creating 440,000 jobs. In other scenarios — and not only those sponsored by the federal government — America seems likely to become the keystone of the global carbon removal industry, its vast geological capacity and fossil-fuel expertise giving it a competitive advantage.
In anticipation, venture capital and public-sector cash has surged into carbon removal, creating a corps of CDR startups with one foot in the geosciences and the other in Silicon Valley. Their employees were at AGU too, mingling in full force. “It was interesting how much industry was there — researchers at companies, even heads of companies,” Talati told me. “I’ve never really experienced that at AGU.” Employees from Lithos, Heirloom, Carbon Direct, Stripe, and Additional Ventures all registered for the conference; in what might be an AGU first, scientists and technologists sipped cappuccinos and nibbled pastries during an early-morning confab at the Salesforce Tower, a few blocks from the official conference site. “AGU is not the place where you would have expected to find these kinds of people, even just for CDR, so it’s interesting that they’re there,” Visioni said.
The whole thing presented both a stark contrast and an inescapable mirror to COP28, where oil lobbyists roamed the grounds. Some environmental old-timers grumble that the UN climate conference has transformed from a diplomatic meeting into a trade show. But maybe there is now so much money and interest and public attention directed at the climate problem that any major gathering about it will take on shades of the commercial. There are lots of rich people with huge amounts of money who want to help do something about climate change. At the same time, the United States government is looking like less and less of a long-term reliable partner on climate research. Sooner or later, someone is going to try to do more serious geoengineering than releasing a few balloons in Mexico. Scientists have started preparing for that day. Is that smart? I don’t know. But it seems like a better strategy than feigned ignorance about where we’re headed.
Editor’s note: This story originally misidentified the name of the person who conducted geoengineering experiments in Mexico. We regret the error.
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