The four scientists, who said they have studied climate physics for the equivalent of more than 100 years collectively, published their commentary in response to a Guardian series that declared “it’s time to talk about geoengineering.”
“Let’s talk about it,” they wrote. “And let us start with some simple truths about this cluster of techno-optimistic ‘quick fixes’ which purport to somehow offset our slow progress towards zeroing out planet-warming carbon emissions.”
The researchers — Pierrehumbert, a professor of planetary science at the University of Oxford and a former IPCC lead author; Slingo, formerly chief scientist of the UK Met Office; Mann, a distinguished professor at the University of Pennsylvania and a member of the US National Academy of Sciences; and Masson-Delmotte, a research director at the Climate and Environmental Sciences Laboratory in France and former co-chair of IPCC Working Group 1 — argued that solar geoengineering proposals would put Earth’s climate in a “dangerously precarious state.”
They said a key flaw in the argument for solar geoengineering is the mismatch in timescales between carbon dioxide and proposed interventions. Carbon dioxide, once emitted, remains in the atmosphere for millennia. Solar geoengineering, by contrast, involves injecting substances whose effect decays in a matter of years. The scientists wrote that it would take as long as two decades to build the necessary infrastructure, and that by then the world would be completely reliant on maintaining it.
“If circumstances force the cessation of solar geoengineering,” they warned, there would be a catastrophic “termination shock” as the trapped heat suddenly returns.
The authors argued that the current push for geoengineering research is focused on technology development with “complete disregard for what the damage might be to the planet.” They pointed to the UK’s Aria agency, which is funding a £60 million geoengineering program that they said is being done in collaboration with for-profit companies.
“Even more ominous,” they wrote, is the explicit entry of venture-capital-funded for-profit startups. They highlighted Stardust, an Israeli-US startup that has received more than $60 million in venture capital and whose business model assumes near-term deployment. They also cited Reflect Orbital, which wants to place giant mirrors in low Earth orbit and is currently pitching sales of illumination, but which the scientists said uses identical technology that could be sold as “cooling credits.”
All of this, the authors said, is happening “in the total absence of governance.” They called it “the height of folly to invest in developing the technology — even if we knew what might work — that only serves to enable unrestricted, profit-motivated deployment.”
The scientists concluded by urging a return to the fundamental task: reducing carbon emissions. “When you’re in a climate hole, stop digging … and burning fossil fuels,” they wrote. “It really is, at some level, that simple.”