Fwd: ‘Termination shock’: trust our expert warnings on geoengineering’s planetary risks
Robert Chris
Here's the 300 word version.
RobertC
-------- Forwarded Message --------
| Subject: | Re: ‘Termination shock’: trust our expert warnings on geoengineering’s planetary risks |
|---|---|
| Date: | Wed, 24 Jun 2026 13:16:35 +0100 |
| From: | Robert Chris <robert...@gmail.com> |
| To: | guardian...@theguardian.com |
Further to my email yesterday, below is a 300 word version of my letter for your consideration. But first, a few comments.
In the interests of balance, The Guardian might consider giving equal exposure to the contrary arguments to those presented in this Pierrehumbert et al article. There are many other 'experts' who fundamentally disagree with with their position on SRM.
The media needs to distinguish between harms that might arise from gaps in climate scientists' knowledge about the inner workings of the climate system, and harms that might afflict life on Earth if prompt action is not undertaken at sufficient scale while the scientists are busy trying to fill their knowledge gaps. All the research in the world isn't going to help if we don't act.
To claim, as these four do, that emissions reductions are THE answer is little short of scandalous.
I have been studying and writing about geoengineering for more than 20 years. I have always thought it was a crazy idea. I still do. But sadly, it's a crazy idea that has now emerged as an essential part of our response to accelerating global warming. I believe we can make is safe(ish). Indeed, I hope we can because the alternative is very much worse.
There’s no point lamenting our recourse to geoengineering. We're here because of our failure over decades to rein in carbon emissions. We still need to do that but the huge increase in emissions during the last three decades means that the mountain we have to climb is higher, steeper and closer. There is now no plausible reduced emissions pathway that provides sufficient confidence that COCAWKI (see me original draft letter) can be averted.
It's great that you're giving space to this issue. But Pierrehumbert et al are not the only 'experts' in this field.
Here's my 300 word version.
Dear Editor
How can prominent climate scientists (Pierrehumbert, Mann, Slingo and Masson-Delmotte - 19 June) appear in denial about the scale and imminence of climate risk? Focusing on the risks of geoengineering with scant regard for the parallel risks of not geoengineering, is baffling. Of course SRM is risky. The relevant question is: compared to what? No tourniquets for them, they might cause gangrene; no chemotherapy, there may be side effects; no emergency braking, their heads might hit the windscreen.
Modelling evidence is clear: failing to reduce absorbed solar radiation is a high-risk strategy. “Stop digging” is woefully inadequate when the hole is already too deep. There is now no plausible emissions pathway that confidently avoids the imminent destabilisation of the global economy. SRM is an essential adjunct, not a substitute, for rapid decarbonisation.
Scientists typically respond to uncertainty with more research. Yet in a complex adaptive system uncertainty never disappears, nor can we know future human behaviour. Research is important but only action that cools Earth will avert the risk of societal collapse. Our historical failure to act decisively, now makes collapse very plausible.
For millennia we have learned by doing. SRM will be no different: not risk-free, but almost certainly risk-reducing, with iterative testing and rejection of failures.
The public faces a choice: heed a narrow academic caution that offers no workable risk management, or adopt a pragmatic approach grounded in reducing real-world risk.
Finally, Pierrehumbert and friends invoke termination shock, grossly overstating its dangers. It becomes critical only under large cooling - conditions that would reflect an already destabilised world. Their claim that geoengineering is a diversion and deflection assumes we lack agency. If so, perhaps they should consider how we are to “Stop digging”.
If you are under 50, this is urgent. The time to act is now.
Dr. Robert Chris
Associate of the Centre for Climate Repair at Cambridge and a Visiting Fellow at The Open University.
Author of Systems Thinking for Geoengineering Policy: How to reduce the threat of dangerous climate change by embracing uncertainty and failure Earthscan 2015
20 Grove hill House, Tunbridge Wells TN1 1SA
Would you like it sharpened further for rhetorical impact, or softened slightly to improve chances of publication?
Robert
Dear Editor
Re: ‘Termination shock’: trust our expert warnings on geoengineering’s planetary risks 19 June 2026
It is extraordinary that there are prominent climate scientists in denial about the extent and imminence of the risks from climate change. Pierrehumbert, Mann, Slingo and Masson-Delmotte are amongst them. Their focus on the risks of geoengineering, apparently totally unconcerned about the parallel risks from not geoengineering, is mind-boggling. There is no argument that geoengineering is risky. But how risky it is in comparison to the alternatives is a critical question they seem happy to ignore. No tourniquets for them, they might cause gangrene. No pain-relieving medicines or chemotherapy for them, they might have side effects. No emergency braking for them, they might hit their heads on the windscreen.
The starting point for any conversation about intervening to reduce the amount of solar radiation absorbed by Earth’s climate system, which is what the solar radiation modification (SRM) version of geoengineering is intended to do, is what happens if we don’t. Modelling evidence is clear: not reducing absorbed solar radiation is a very high-risk strategy. This crew claim that ‘when you’re in a climate hole, stop digging … and burning fossil fuels. It really is … that simple’. Given that between them they claim to ‘have studied the physics of climate for the equivalent of well over 100 years’ it beggars belief that they are unaware or perhaps merely unconcerned by the robust modelling evidence that there is no longer any plausible future emissions scenario that will prevent global mean surface temperature from rising more than enough to risk widespread societal and ecosystem collapse in the coming decades. That train left the station some time ago. The only trains left are slow ones and if we want high confidence they’ll reach their destination in time to deliver us from climate catastrophe, they need boosters. That’s how to frame SRM; it’s a booster not an alternative. No one promoting SRM claims it’s an alternative to aggressive emissions reductions.
Is a climate change induced collapse certain? Certainly not. But it is certainly plausible. And here we come to the nub of the problem. For climate scientists, risk derives from ignorance. Their response is to do more research. That’s what scientists do, they research. But they don’t act because in complex adaptive systems like Earth’s climate system, there is no stopping point when they can declare that we finally know with high confidence that if we do this, then the result will be that. In part, there is no stopping point because they can never know how future people will behave. Will we reach net zero emissions by 2050 or might it be 2150, or even 2250? This is unknowable and because it’s unknowable they dream up sets of different future scenarios and say that in this scenario, that would happen and in a different scenario something else would happen. But which scenario will be closest to future reality, they have as much idea as the rest of us. This is the academic job preservation plan – more research keeps them employed.
However, more research generally increases risk where it is used as an excuse to not act. Throughout human history we have learnt by doing. The Danyang–Kunshan Grand Bridge in China, the world’s longest bridge, was not the first bridge ever built. The Airbus A350 was not the first machine to take to the skies. We have thousands of years of experience of learning by doing. There is no reason to suppose that technologies to reduce the amount of absorbed solar radiation will be any different. Will they be risk free? Certainly not. But will they be risk reducing, almost certainly because we’ve quite a good record of screening out the trials that fail before they cause too much harm.
But we can be confident that without these technologies the likelihood of catastrophic warming is increased to the point of being very likely. The public and our politicians have a simple choice. Rely on the advice of a small cadre of climate scientists who by their utterings demonstrate that they do not understand how to respond effectively to avert existential risk, or turn to those with experience in assessing real world risks and how to reduce them by the intelligent application of learning by doing.
As to the ‘termination shock’ that features so prominently in their title but receives only a cursory mention in the article, they fail to note that this would only be a significant threat in circumstances where several degrees of cooling were being delivered by the SRM. In this event, the collapse of civilisation as we know it (COCAWKI) would likely already have occurred had the SRM not been there to keep a lid on the warming. To argue, as many do, that the mere existence of SRM would exacerbate the underlying warming by taking the pressure off the need to phase out fossil fuels, what is often misleadingly referred to as ‘moral hazard’, is, in effect, to claim that we have no agency over our communal behaviours. If that’s so, why would fossil fuels be retired even in the absence of SRM? Maybe they won’t be. Certainly, in this regard we’ve not done a brilliant job so far; despite recent stunning growth in renewable energy, fossil fuels still account for close to 80% of global energy supply, a proportion that has hardly changed for decades.
If you’re under 50 you should take this issue very seriously. The accelerating pace of climate change and the lead times to scale the necessary climate interventions to avert COCAWKI mean that the time to act is now.
Dr. Robert Chris
Associate of the Centre for Climate Repair at Cambridge and a Visiting Fellow at The Open University.
Author of Systems Thinking for Geoengineering Policy: How to reduce the threat of dangerous climate change by embracing uncertainty and failure Earthscan 2015
20 Grove hill House, Tunbridge Wells TN1 1SATel: 07976 262808
Tom Goreau
What is your word limit?
Here’s a very quick 277 word edit of your 300 word version, with only one addition, that collapse may be not just plausible, but inevitable (I’ve been rereading Donella Meadows Thinking in Systems, and H.T. Odum’s book on using systems thinking to mimimize disruption and optimize stability in the inevitable crash following overshoot). With a bit more work you can get it down to 250, though it will cramp your elegant style. Have fun, I have to go back to work!
How can prominent climate scientists (Pierrehumbert, Mann, Slingo and Masson-Delmotte - 19 June) deny the scale and imminence of climate risk? Focusing on geoengineering risks with scant regard for parallel risks of not geoengineering is baffling. SRM is risky, but the relevant question is compared to what? Tourniquets might cause gangrene; chemotherapy has side effects; emergency braking causes heads to hit windscreens.
Modelling evidence is clear: failing to reduce absorbed solar radiation is a high-risk strategy. “Stop digging” is woefully inadequate when the hole is already too deep. There are now no plausible emissions reductions that confidently avoids imminent destabilisation of the global economy. SRM is an essential adjunct, not a substitute, for rapid decarbonisation.
Scientists respond to uncertainty with more research. Uncertainty in complex adaptive systems never disappears, nor can we know future human behaviour. Research is important, but only action that cools Earth will avert societal collapse risks. Failure to act decisively now makes collapse very plausible, if not inevitable.
For millennia we have learned by doing. SRM will be no different: not risk-free, but almost certainly risk-reducing, with iterative testing and rejection of failures.
The public faces a choice: heed narrow academic caution that offers no workable risk management, or adopt a pragmatic approach grounded in reducing real-world risk.
Pierrehumbert et al. invoke termination shock, grossly overstating its dangers. It becomes critical only under large cooling - conditions that would reflect an already destabilised world. Their claim that geoengineering is a diversion and deflection assumes we lack agency. If so, perhaps they should consider how we are to “Stop digging”.
If you are under 50, this is urgent. The time to act is now.
Your 300 word version:
--
You received this message because you are subscribed to the Google Groups "Healthy Planet Action Coalition (HPAC)" group.
To unsubscribe from this group and stop receiving emails from it, send an email to
healthy-planet-action...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/da96fefe-74f3-4622-9794-98f1e5def967%40gmail.com.
Douglas Grandt
On Jun 24, 2026, at 9:09 AM, Tom Goreau <gor...@globalcoral.org> wrote: