1.5C: too late to prevent tipping catastrophe without quickly cooling down to 1.0C or below

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John Nissen

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Jul 30, 2025, 6:43:27 AM7/30/25

to Planetary Restoration, Peter Wadhams, David Spratt, Sir David King, Shaun Fitzgerald, healthy-planet-action-coalition, Oren Gruenbaum, Renaud de RICHTER

Hi all,

David Spratt notes the inadequacy of 1.5C [1]. To halt tipping processes, cooling intervention is now urgently required, especially in the Arctic where tipping processes already active could suddenly become irreversible.

An example is the disintegration of the Greenland Ice Sheet which could suddenly become irreversible with the collapse of one or two major glaciers, committing humanity to several metres (or perhaps many metres) of sea level rise.

I am sure Sir David King, mentioned in the blog, realises the dangers arising from Arctic meltdown. He and Shaun Fitzgerald organised the Cambridge Arctic Repair conference at the end of June to study possible solutions.

Stratospheric Aerosol Injection (SAI) is the front runner, because of its available cooling power and potential speed of deployment at scale, unmatched by any other technique. There was a presentation on practical details for SAI deployment using high-flying aircraft.

Cheers John

[1] http://www.climatecodered.org/2025/07/the-15-degrees-climate-advocacy.html?m=1

David Spratt

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Jul 30, 2025, 7:27:31 AM7/30/25

to Nissen John, Planetary Restoration, Peter Wadhams, David King, Shaun Fitzgerald, healthy-planet-action-coalition, Oren Gruenbaum, Renaud de RICHTER

Thanks John,

The full paper is here:

https://www.breakthroughonline.org.au/climateadvocacy2025

With global warming now at 1.5°C and accelerating, a new discussion paper from Breakthrough asks the hard questions: Are we relying on flawed assumptions about system stability and recovery? And what would it really take to restore a safe climate? Exploring the limits of current strategies, it sets out a alternative: a three-lever approach combining zero emissions, large-scale carbon drawdown, and urgent research into direct cooling.

Key messages:

Global warming has reached 1.5°C and the rate of warming is accelerating.
On the present path, Earth will heat by 3+°C. The aerosol “Faustian bargain” means that emissions reductions are unlikely to reduce the rate of warming in the near term.
While much of the climate community remains committed to the 1.5°C Paris goal, this target is fundamentally flawed: it does not represent a safe boundary, will not prevent large-scale Earth system elements passing tipping points, nor does it mark a point of system stability.
Too often, climate strategy has been reduced to a “triage politics” of selecting what to save and what to abandon. Policies of large “overshoot” of 1.5°C make assumptions about the ability to restore Earth systems that are not valid.
Advocates now face difficult questions, including whether a safe climate can be achieved if climate actions involve only the elimination of greenhouse gas emissions.
An alternative goal is a return to the Holocene conditions of <0.5°C.
This demands a three-lever strategy — simultaneously pursuing zero emissions, large-scale carbon drawdown, and research into safe short-term cooling methods.