Geoengineering Solution Embraces Aircraft to Cool Earth Temps

Slowing climate change might be possible with the help of something long considered a lead contributor: existing jetliners. 

According to new research from the University College of London, the world’s existing fleet of jetliners could be retrofitted to cool global temperatures through stratospheric aerosol injection—a proven concept that has been researched for decades. 

The findings are detailed in “Low-Altitude High-Latitude Stratospheric Aerosol Injection Is Feasible With Existing Aircraft,” recently published in the journal Earth's Future. 

The computerized simulation was completed using the Earth System Model (UKESM1), which is operated by the U.K. government’s meteorological survey service. The study also involved researchers from Yale University, Harvard University, and University of Exeter. 

Nature-inspired 

Jetliners could serve as delivery mechanisms for sulfate aerosols, such as sulfur dioxide, which would reflect sunlight away from Earth and cool the planet. 

The research team concluded that the injection helps cool the planet more efficiently when sprayed at a height of 12.4 miles (20 kilometers).  

Commercial widebody aircraft like the Boeing 777 have a flying limit of 8.1 miles (13 kilometers), but can be retrofitted for stratospheric aerosol injection, though it is not as efficient. 

“When volcanoes erupt and cool the planet, it’s sulfur dioxide [SO₂] that gets injected into the stratosphere naturally during volcanic eruptions. We often use this approach because we have that volcanic analogy,” explained Alistair Duffey, a doctoral student at UCL’s Department of Earth Sciences and the paper’s lead author. 

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When Mount Pinatubo erupted in 1991, it released roughly 10 million tons of SO₂ into the stratosphere and cooled the planet “by maybe half a degree Celsius for a few years,” Duffey said. 

Computerized climate models simulated a Boeing 777F freighter in the stratosphere carrying a payload of sulfur dioxide for atmospheric injection. The researchers found that an existing Boeing 777F could be retrofitted to deliver a payload of 110 metric tons by flying 5.7 sorties per day on average. Injection is more efficient at the poles below 14 kilometers (8.6 miles), and more efficient in the subtropical range over that. 

New jetliners would need to be purpose-built to operate at a 12.4-mile (20-kilometer) height, which would take a decade or more to engineer. However, those aircraft would be more effective at cooling the climate. 

“What we’re imagining is you’d have to take something like passenger aircraft fill it with tanks and use it deliberately to deploy at a higher altitude than typical flights,” Duffey said.

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The computerized simulation doesn’t model new wide-body aircraft, but an existing 777F could be redesigned as a compromise to developing new aircraft.

“You’re still imagining doing some engineering work on those planes to fit them with tanks of SO₂ as much as possible so they can maximize payload capacity for a given altitude,” Duffey noted. 

The compromise 777F design is sub-optimal, with “strongly increased side-effects,” Duffey said.  

“This low-altitude strategy requires three times more injection than high-altitude SAI, and so would strongly increase side-effects such as acid rain,” according to the paper.  

Controversy? 

Stratospheric aerosol injection is not a new idea, as researchers have long known this approach would cool the planet. However, it remains deeply controversial because it could also pollute the environment. 

"There is plenty of evidence that this would effectively reduce climate impacts," Duffey said.  

Despite the work’s potential, Duffey “had death threats after this paper came out from chemtrail conspiracists who believe that we’ve already been doing this for a long time,” he said. “I’ve also given talks where I’ve been interrupted by people who don’t believe climate change exists.”

Chemtrail is a conspiracy theory amplified by social media. Believers think condensation trails left by airliners are deliberately sprayed for nefarious purposes by actors such as governments, according to a 2021 research paper published by the Association for Computing Machinery. 

Duffey took the death threats seriously and discussed his research at length. 

“There is a visceral reaction to the idea of putting particles into the air, but there is plenty of evidence that it would effectively reduce climate impacts,” Duffey said. “No one is doing geoengineering right now. It hasn’t been done at scale before. We’re talking about potential future activities.” 

Agam Shah is a business and technology writer in Phoenix.