After decades of trying to stop Earth from heating up, scientists are exploring how to reverse climate change and maybe even cool the planet back down.

Could clouds be brightened so they reflect more sunlight back into outer space? If lab-grown seaweed is sunk into the ocean, how much carbon dioxide could it absorb? Would drilling holes into glaciers extract enough heat to slow sea level rise?

The University of Chicago positioned itself as a leader in this emergent field — known as geoengineering — after recruiting renowned physicist David Keith to build out a climate engineering program with 10 tenure-track faculty hires and several young researchers.

“We cannot understand (geoengineering) with just a bunch of individual people working on this in an isolated way. We need to bring together a broad group of scholars and students to debate it in a much richer way,” Keith said.

While society is struggling to kick its addiction to fossil fuels, compensating by meddling with Earth’s atmosphere, oceans and land masses has long been viewed as taboo. Many scientists have argued that geoengineering interventions are a distraction from emissions reductions at best and too dangerous to study at worst.

The most controversial, and likely also the fastest-acting method, is shooting aerosols into the sky to deflect the sun’s rays, known as solar radiation management or solar geoengineering.

Physicist Peter Irvine, 39, arrived in Hyde Park last week from London to study solar geoengineering as a research assistant professor on Keith’s team.

The process is anticipated to have a similar effect to massive volcanic eruptions such as the 1815 eruption of Mount Tambora in modern-day Indonesia, which disrupted weather patterns globally for three years. Summer temperatures in Europe were the coldest on record and fog dimmed sunlight in the United States.

But, instead of volcanic ash, man-made aerosols would envelop the world and deflect the sun’s rays. Temperatures worldwide would presumably start dropping within a year.

“Solar radiation management is the only (climate intervention) that could be deployed within a single presidential term,” Irvine said.

But, scientists have historically kept geoengineering at arm’s length out of concern that rich nations and fossil fuel companies would lean on promises of expensive, yet-to-be-developed technology to avoid changing their emissions-intensive practices. Carbon emissions are the root cause of climate change.

However, society is unlikely to cut emissions fast enough to stave off the worst of climate change, experts say. Global emissions must be cut by 45% compared with 2010 levels in the next six years to keep warming at or below 1.5 degrees Celsius. Meanwhile, the world is on track to increase emissions by 9%, according to a 2023 United Nations report.

The International Energy Agency anticipates that total mineral demand for clean energy technologies, from solar panels to EV batteries, will double or quadruple by 2040. Not only is mining emissions-intensive, but it also takes time, which Manon Duret learned while working on sustainability initiatives at British multinational mining company Anglo American.

“I just saw the sheer scale of things: how long it takes to get a permit to build a mine, how long it takes to create a new mine from the ground up,” said the 32-year-old microbiologist. This was her “eureka moment” to join the U. of C. initiative. “It’s not going to happen. We’re not going to decarbonize the world so easily. We need to start looking at other options.”

At U. of C., she will explore the practical hurdles that must be overcome to make geoengineering possible, including material acquisition, transportation and international regulations. Geoengineering is a necessary stopgap while society works on reducing emissions, she said.

Her husband, B.B. Cael, 33, an oceanographer by training, is also joining the initiative to assess the cost, scalability, effectiveness and risks of different geoengineering methods.

The ability to mute man-made climate change is promising to scientists such as Keith, who believes society must weigh its race to reduce emissions against other priorities such as equitable economic development and advancing artificial intelligence. He has been a vanguard in geoengineering since the 1980s, starting one of the first companies to suck carbon dioxide out of the air and leading Harvard University’s research into solar interventions.

“The ethical thing to do is to cut emissions a little more slowly,” Keith said. If scientists can cool the Earth down, society can buy time before hitting a climate tipping point.

While Irvine said he’s certain solar geoengineering would reduce extreme heat, heavy rainfall and sea-level rise, he admits it may also intensify droughts, increase acid rain and thin the ozone layer. These unknowns could affect food production and biodiversity worldwide.

The stratosphere — where the aerosols would be injected — is the home of the thinning ozone layer and has already seen multiple “improbable events” in recent years, said Liz Moyer, the only professor at U. of C. who measures this high level of the atmosphere. While climate change has warmed the layer of the atmosphere closest to Earth’s surface, it has cooled the stratosphere. Large wildfires have also triggered unprecedented chemical reactions in the stratosphere.

Dispatching aerosols would add another element of uncertainty to a place scientists know little about, and soon may even know less about, Moyer said. Within the next decade, as scientists toy with shooting aerosols into the stratosphere, NASA will decommission an aging satellite that has been collecting data on the stratosphere, with no planned replacement.

Moyer likened tampering with this layer of the atmosphere without adequate monitoring to performing surgery without a heart monitor on standby.

“If you’re going to do experimental surgery and you haven’t thought about what kind of technology you would need to monitor the patient, then you’re not thinking about the problem carefully enough for me to trust you with my body,” she said.

Once started, sun-deflecting aerosols must be shot into the sky every couple of years. If stopped, the Earth could experience rapid warming, also known as “termination shock.”

“It’s an enormous burden on the future,” said Raymond Pierrehumbert, a former U. of C. professor who now works at Oxford University. “How do you know these interventions are going to be doable for the next generation? What if there’s a global war, another pandemic?”

He is one of more than 500 scientists who have signed an open letter calling for an international nonuse agreement on solar geoengineering.

The signatories cite concern that there is no adequate governing body to determine fair and effective deployment of a technology that will require coordination between and touch every corner of the planet.

Irvine, however, cautions that ignoring solar geoengineering may increase the risk of it being used irresponsibly.

“The more it’s suppressed, the greater the risk of a single nation or small group of nations pushing ahead independently in desperation,” he said.

The Chinese government has experimented with changing weather patterns for decades. And, last year, the White House released a report identifying knowledge gaps and potential research areas for a federal solar geoengineering research program. There has not been a directive to act on the findings yet.

To date, Silicon Valley has provided a sizable amount of funding for solar geoengineering research. The Harvard research program Keith previously led was funded in part by Bill Gates and Dustin Moskovitz, co-founder of Facebook. Keith’s direct carbon capture company, Carbon Engineering, was also partially funded by Gates before being sold to Occidental Petroleum. Keith no longer has a stake in the company, but its acquisition by the oil conglomerate has resurfaced concerns that geoengineering could be a crutch for the fossil fuel industry.

The U. of C. initiative declined to share its budget and funding sources, except for Outlier Projects, a new nonprofit that says it is “advancing research on nascent ideas with the potential for outsized impact on the climate crisis.” The nonprofit couldn’t be reached for comment.

This year, the Environmental Defense Fund also announced it would be funding solar geoengineering research, a significant endorsement by a mainstream environmental organization that has been an outspoken skeptic of climate-altering interventions.

So far, most research has been limited to computer modeling. While valuable, unforeseen variables are likely to make real-world scenarios more complex. Field research that would begin exploring these complexities has been difficult to get approved. Two high-profile experiments — one in California and another in Sweden — were canceled this year due to local opposition.

Residents, including a Nordic indigenous tribe, expressed passionate concerns about potential impacts on weather patterns.

Keith, who was involved in the Sweden project, has spent his career guided by the conviction that the unknowns are all the more reason to study geoengineering. For decades, he has argued that politicians and the public can only decide whether interventions are worth deploying when armed with rigorous research.

“It’s definitely not an elite club of scientists’ job to decide what the public gets to know or not,” Keith said. “I think that’s deeply unethical.”

Pierrehumbert cautioned, however, that these small-scale field experiments could give false confidence. They’ll answer how to build and deploy the technologies but won’t reveal their effects over time and across the atmosphere. That would require full-scale deployment, he said.

He likens moral queries about solar geoengineering to those around the hydrogen bomb and infectious diseases.

“Scientists have a responsibility not to develop technology that could be threatening and destabilizing,” Pierrehumbert said. “How would you feel about research to develop engineering pathogens like COVID that are deadly and spread rapidly?”

Meanwhile, Moyer finds comfort in a well-established institution such as U. of C. taking a lead in this field. She is worried, however, that civil engineers will be absent from the conversations about climate systems engineering.

“This is a huge civil engineering project,” she said, noting that engineers are trained to account for risk in ways scientists are not.

Although Keith expressed intentions in convening an interdisciplinary team, all hires to date have been in the geophysical sciences department. The university does not have a civil engineering school.

There is one thing all the scientists agree on: The Earth is hotter than it was last year and it will be many years before future generations experience a planet as cool as the one we live in today. If the planet reaches net zero emissions, it will stop heating up, but it won’t cool down.

“It’s not like the climate wasn’t changing and we’re thinking we could make it better than it used to be,” Irvine said. “It’s that the climate is rapidly racing toward a state we’ve never seen before with all sorts of unknown consequences and known consequences that are going to be bad.”

By this logic, scientists have a moral imperative to research and innovate in hopes of staving off the worst of climate change, unless intervening with Earth’s systems more than we already have could present new dangers.

“People make bad decisions when they’re in a panic and it’s justifiable to be in a panic because things are bad and getting worse,” Pierrehumbert said. “But it’s necessary to step back and think, ‘OK, but am I going to do something that’s actually going to make it worse?’” He believes the only viable solution is to eliminate fossil fuel usage globally as quickly as possible.

What if society can’t decarbonize fast enough, though?

Keith fears the day when geoengineering may be the last-resort option that hasn’t been adequately studied: that antidote just beyond reach or — worse — behind a glass case that is smashed out of desperation without a full understanding of the consequences.

Now in his 60s, he sees the U. of C. initiative as a passing of the torch to the next generation to ensure society does not end up in either of these positions.

“In the end, this needs to be global, we need to build a field,” Keith said.

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