Re: Carbon Removal Won't Scale Fast Enough
John Nissen
To: the editor of the Financial Times for publication
19/11/2025
The necessity for cooling intervention
Dear editor,
While COP30 focuses on CO2 emissions, the huge danger from Arctic meltdown is being ignored. Five critical “tipping elements” in the Arctic are threatening us: the Arctic sea ice; the Greenland ice sheet; the permafrost with its methane release; the polar vortex and jet stream; and the Atlantic meridional overturning circulation. In each case we are already seeing acceleration towards a point of collapse, threatening catastrophic climate change or sea level rise globally.
The most obvious global threat is from the Greenland ice sheet. If its disintegration is not halted very soon, we could be committed to many metres of sea-level rise in the future, with partial collapse a real danger this century. Even half a metre would be catastrophic for low-lying countries like Bangladesh and Vietnam; several metres would devastate coastal cities and agricultural land worldwide, with incalculable economic consequences.
If the Arctic temperature is to be reduced, the heating power from greenhouse gases and from loss of reflectivity as ice retreats has to be offset by even greater cooling power from solar geoengineering. A rapid temperature reduction is needed to minimise risk from tipping element catastrophe.
In 2012, I and sea ice expert Peter Wadhams testified to the UK Environmental Audit Committee’s inquiry on Protecting the Arctic. We warned that geoengineering was already necessary to save the Arctic—and were openly ridiculed. Since then, Arctic temperatures have risen four times faster than the global average, and the danger from tipping elements has only grown.
We now face a planetary emergency. This justifies the immediate consideration of Stratospheric Aerosol Injection (SAI)—a solar geoengineering technique that mimics the cooling effect of large volcanic eruptions by injecting SO₂ into the stratosphere. Understandably, many find the idea of SAI alarming. But recent research shows that it can be deployed with minimal risk of serious side effects—especially compared to the risks from continued inaction.
SAI is the only scalable technique we currently possess to reduce the Arctic temperature in time to avert catastrophe. Its potential global benefits—to humanity, ecosystems, and the climate system—are immense. What we need now is leadership. Business and industry must step up and support the development pathway to rapid and safe SAI deployment. Without such leadership, we may simply not act in time.
Yours sincerely, etc.
Watch now
Last week, I presented at CDR30’s session on “The Global Heating Emergency: What’s the Plan?” The event brought together the carbon removal community during COP30 to discuss the dramatic acceleration of global temperatures and what an integrated climate response actually requires. My presentation synthesizes much of what I’ve been writing about here—the timeline collapse we’re facing, the reality that the planet is already too hot, and what that means for our climate response toolkit.
The core argument is straightforward: carbon removal is absolutely the long-term solution. The IPCC projects we need 10 billion tonnes removed annually by 2050. I’d argue our goal should really be more like 60 billion tonnes removed every year, but even 10 billion is going to be an astronomical lift. And it has to happen one way or another, because there is no substitute for actually drawing down atmospheric CO₂ if we want to solve this permanently.
But the math doesn’t work. Carbon removal won’t scale fast enough to prevent us from crossing critical tipping points. Today we’re removing single-digit millions of tonnes. Even in optimistic scenarios, meaningful temperature reduction from CDR is a next-century solution, and the tipping points—AMOC collapse, permafrost methane release, coral reef systems—aren’t waiting that long.
Which means we’re going to have to cool the planet down while we scale up removal and drive down emissions. The question isn’t whether we’ll intervene to lower temperatures. The question is whether we’ll do it through deliberate choices made via rigorous democratic governance processes, or whether we’ll do it in desperation after crossing points of no return.
I’m not saying deploy stratospheric aerosol injection tomorrow. I’m saying that accepting “one method has problems, so let’s give up” is not a satisfactory outcome. If SAI proves unfeasible due to governance challenges or unacceptable side effects, then we find other approaches—marine cloud brightening, methane destruction, cirrus cloud thinning, approaches we haven’t thought of yet. We keep looking until we find solutions that manage the tradeoffs, minimize harm, and actually work geopolitically. The physics doesn’t care about our governance challenges. The tipping points don’t wait for us to achieve political consensus.
Carbon removal remains essential—it’s the only permanent solution, the only way to address ocean acidification, the only path that lets us eventually scale back cooling interventions. But in the meantime, we have to figure out how to bring the temperature down. Not as a replacement for emissions cuts and removal, but as a bridge that buys time for those solutions to reach the scale we desperately need.
The presentation walks through this logic: why we’re using the wrong mental model when we focus on annual emissions instead of temperature, why tipping points demand faster action than CDR can provide, and why the carbon removal community is uniquely positioned to advocate for cooling research and governance development.
If you missed the live session, this captures the core argument I’ve been building toward over the past year of writing here.
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