Re: The number of prospective climate solutions narrows still further

[Dr. Chris Robert]

Hi Sev

I don't seem to have received your message referred to below, perhaps you cold resend it.  But before doing so, could I ask you to reflect on a couple of details that will make it easier for me to put this through WTF.

It's not for WTF to show that any particular amount of fossil fuel emissions reduction, CDR or SRM by any given year is more or less likely.  It can tell you what the algorithms determine would be the global warming impact of any combination of the three, but the 'likelihood' question is about politics, engineering and behaviour change and assessing how they will play out in the future is always going to be a judgement call, not a modelling one. 

What I can tell you is that in the notional boundary case where emissions stop completely in 2026, WTF says that global warming reaches 1.8^oC in the early 2030s and stays there more or less indefinitely.

Where you go from there depends on what outcome you want by when.  For example, still with what is almost certainly an unrealistic zero emissions by 2030, if you wanted to get global warming down to stabilise at +1^oC by 2100 using only CDR, you'd have to start in 2026 and build it to 23GtCO₂yr^-1 by 2036, after which it could be eased back to 1GtCO₂yr^-1 by 2150.  This implies aggregate CDR of ~1330GtCO₂ by 2100 before it begins to tail off rapidly.  Whether that amount of CDR in that time frame is feasible is a political and engineering question.  But given that the starting point here is an almost certainly unrealistic emissions reduction profile, this example is probably little more than academic.

It is also worth noting that in this profile, the aggregate overshoot is 40^oCyears - this is a measure of the excess heat above the 1^oC threshold that would be retained in the atmosphere during the period of overshoot.  The importance of this metric is that while occasional high peak temperatures may cause serious and even irreversible harms, a sustained period of less warming will still melt polar ice caps and mountain glaciers elsewhere, and will still accelerate the whole range of other climate change induced harms, albeit more gradually, at least until they are sufficient to reach some critical tipping points.  A second, and possibly more important judgement call is what would be a 'safe' level for this aggregate overshoot.  Note that in 2025 the aggregate overshoot above a 1^oC threshold is ~7^oCyears and that has been sufficient to provoke the various climate change induced losses already witnessed around the world in terms of floods, droughts, wildfires, seal level surges, crop failures, biodiversity loss, heatwave deaths and so on.  Does aggregate overshoot of 40^oCyears represent an unacceptable risk?  In this regard, it is important to know what your reference level is for the global surface temperature anomaly above pre-industrial, for a stable and sustainable climate system.  If your threshold is 1.5^oC, the aggregate overshoot to date has been <<1^oCyear.

So, when responding to this, can I ask you to be specific about the following:

1. What's your threshold (in ^oC) for warming above pre-industrial, for a stable and sustainable climate system?
2. What level of aggregate overshoot (^oCyears) above this threshold, do you consider to be the absolute minimum that would be acceptable?
3. How quickly do you think, realistically given all the social and political realities of the world as it now is and is likely to be in the coming decades, emissions can be reduced?  I need to know in what year and at what level (GtCO₂yr^-1) emissions will peak, and in what year and at what level they will eventually stabilise?  Will emissions ever get to zero or is there likely to be some minimal level of emissions continuing into the distant future?
4. Similarly, what do you consider to be the most realistic aggressive CDR profile that could be achieved, again starting when, and reaching how many GtCO₂yr^-1 by when?  Remember that this is both capture AND permanent sequestration.

Armed with these expectations, I'll then tell you what WTF assesses to be the global warming impact, and how much SRM, if any, is needed to deliver your chosen acceptable amount of aggregate overshoot.  Please resist the temptation to answer  questions 3 and 4 with what you'd like to see happen, or what you think could happen in a perfect world in which optimal choices were always made, and focus rather on what, given all the constraints in the real world, you consider to be feasible.  This is not the place for hope and optimism, it's the place for hard-headed unsentimental realism.  If it's easier for these answers, give ranges that your gut tells you cover a 95% confidence interval.

If others wish to engage with this, I'd be very happy to process your assumptions if you're struggling to do it yourselves with the shared copy of WTF.

Regards

RobertC

On 26/12/2025 06:07, Sev Clarke wrote:

Hi Herb,

I concur with most of what you say. Only I also believe that a few, small, transparent and targeted experiments could also do a great deal to change both public and scientific opinion to our way of thinking. Thus, I will continue my efforts to make them happen.

In view of this, I hope that RobertC and his collaborators will use his WTF model to show a selection of what combinations of feasible climate interventions could be used to bring us back to something like Holocene conditions within, say, forty years. They might also show those which cannot reasonably achieve this in the required acceptability, time or cost frameworks.

This is what I suggested to RobertC at the beginning of the Xmas break - not expecting a response until much later:

"Regretfully, as I have eschewed Microsoft products except for LinkedIn, I  cannot experiment with it myself. Nonetheless, a screenshot I took of your presentation shows what the combination of my Buoyant Flakes and Nanobubbles would need to do to keep us within 1C of average pre-industrial temperature. If I interpret you correctly, the CDR of 10GtCO2 by 2040 would be a stretch, more likely to be achieved by 2045, but it should be able to be trebled by 2060 to 30GtCO2/yr and beyond. However, when combining the various albedo effects (phytoplankton, bubble, cloud, and maybe ice&snow), the 2.5Wm2 by 2050 goal ought to be achievable by, say, 2047 and be maintainable to 2300 at that rate. 
Keeping the Emissions as you suggest, might you model this for me and send me the screenshot, please?”

If we can use WTF to give us a set of notionally-achievable goals for different combinations of SRM/TRM/CDR/CH4 methods we think have good potential, then could we not take these to philanthropic, industry, and/or individually-concerned governments to see whether they might fund the necessary RD&D - perhaps by way of prize competitions. Such would be an improvement on JFK’s moonshot determination because it: would not require superpower or COP dedication; would additionally specify the means to achieve the aim; and would provide phased objectives - not just a single and fairly distant goal? Best of all, the different combinations would offer us different, and possibly complementing or synergetic, routes to the main objective, not all of which need to succeed.

Regards,

Sev

On 26 Dec 2025, at 2:04 pm, H simmens <hsim...@gmail.com> wrote:

Hi Sev,

My quick thoughts! 

Thanks for your analysis and suggestions. You’ve laid out a number of interesting ideas and perspectives. 

Without necessarily agreeing or disagreeing with what you articulated my own view which I believe is still shared at least in part by Robert C is that a necessary prerequisite to effective climate intervention of any sort still requires a massive Urgent and highly professional advocacy campaign in most every corner of the planet. 

As fast as I can tell there is still not one elected official anywhere on the planet or one high level climate activist in support of climate intervention. I just asked GROK and it confirmed my understanding as expressed in the previous sentence. 

Interestingly the only two activist groups that are mentioned by Grok are OA in Finland and the Chesapeake Climate Action Coalition which is the regional climate activist group that I have close ties with and whose founder and executive Director lives a few minutes from me. 

And neither of those two groups supports safe and effective deployment, just more research. 

Given that reality and given the reality that very few Climate scientists outside of the SRM research community are supportive of intervention (and almost every member of the research community is not actually in support of intervention they’re only supportive of research into intervention) the clear need is to change that dynamic.  (I understand that Jim Hansen may be touring college campuses when he finally finishes his book this spring and what exactly he will say about intervention will be very important.) 

In my view given the urgency and immensely of this challenge we should all be focusing our collective efforts as Robert C and I attempted 2 1/2 years ago to identify people or institutions who can shake loose $10-$50 million or so to fund a highly professional NGO with international reach that can systematically use every sophisticated lobbying and educational technique imaginable to both influence various climate leaders as well as grassroots citizens and activists - Robert C I believe calls this a pincer movement. 

I have made this case on more than one occasion to my colleagues at HPC and on our list and as far as I can tell I have gotten nowhere. 

I am by no means against doing the kinds of analytical work about potential techniques that build on what HPAC and perhaps others have already done as I believe you are suggesting Sev. 

This information is vital to have so then it can be incorporated into a sophisticated international advocacy effort along with Robert C’s WTF model. 

But the primary objective must be to transform intervention from its presence status as emphatically socially disapproved most everywhere to if not widespread social acceptance at least strategically developed social acceptance amongst key decision makers.  

I would say that needs to be done in the next 3 to 5 years at the latest in order to have any opportunity to deploy cooling before tipping points progress too far and derailment risks become too extreme. 

Robert T’s approach of reaching out to big powerful and influential international industries most affected would become one of the strategies employed by this new NGO. 

We can and should talk about institutional arrangements such as an Albedo Accord, a COP Climate Triad accord, the creation of a more muscular version of the Climate Overshoot commission and other options. 

But I would argue strongly that focusing on these downstream issues is putting the cart before the horse. (that is why I am skeptical of the advocacy for a Albedo Accord at this time.)

If and when enough influential leaders in the world community recognize how screwed we are unless we intervene in the climate they will mobilize to exert their influence through whatever set of institutional arrangements they decide on - whether relying on the current institutional landscape and/or by creating new institutional arrangements. 

We also urgently need to lobby to help create this mega NGO that can lobby international institutions, national governments and high wealth individuals to come together to provide funding to accelerate R&D on every promising technique with a goal of having an objective assessment of all possible tools of the Triad to be completed within the same 3 to 5 year period. 

Herb

Herb Simmens
Author of A Climate Vocabulary of the Future

“A SciencePoem and an Inspiration.” Kim Stanley Robinson
@herbsimmens
HerbSimmens.com

On Dec 25, 2025, at 7:54 PM, Sev Clarke <sevc...@me.com> wrote:

Hi Colleagues,

This Swiss RD&D https://cen.acs.org/environment/climate-change/enhanced-rock-weathering-co2-sequestration-climate-change/103/web/2025/12?sc=251224_news_eng_cennews_cen_NonMember&elqE=16321&elqC=9698 downgrades yet another publicised climate solution, Enhanced Rock Weathering or ERW.

DAC and BECCS have already been soundly discounted. Afforestation lacks land, water, timeliness and permanency. SAI has what I believe to be too many downsides. And space-based methods are too fraught, costly and untimely. Heavy adaptation and migration are not solutions, but are just temporary palliatives for the few. Some of the only remaining options with promise are MCB and some other ocean-based ones that chiefly focus on albedo modification - with others addressing the atmospheric methane problem.

Should HPAC, its partners, and possibly RobertT’s upcoming book, consider developing a popularised publication and tool that decried the COP process, and instead promoted a multinational, red team/blue team triad approach to proposed solutions, making use of moderated AI summaries, our collective critical input, and RobertC’s WTF resources for each candidate solution and their more useful temporal combinations? 

What would be some prospective agencies to fund and oversee the effort? Perhaps the G20 https://en.wikipedia.org/wiki/G20 and  https://theconversation.com/the-g20-how-it-works-why-it-matters-and-what-would-be-lost-if-it-failed-251500 but modified to have a permanent secretariat and no veto power? Note, that whilst the US is to be given the next G20 Chair, the two nations of the managing troika, Brazil and South Africa, might outvote the US until there is a beneficial change in the US Administration.

Sev

[John Nissen]

Hi Robert,

What WTF tells you is, I believe, quite wrong:

[Quote] What I can tell you is that in the notional boundary case where emissions stop completely in 2026, WTF says that global warming reaches 1.8^oC in the early 2030s and stays there more or less indefinitely.

No!  That's wishful thinking!  2C will be reached by around 2040, even if emissions were halted in 2026, because of the heating power from legacy CO2 and, increasingly, from lost planetary albedo.  This is confirmed by Hansen in his "Global warming in the pipeline".

CDR cannot realistically reduce temperatures this century, as Peter Fiekowsky would like us to believe. So we are left with SRM.  And only SAI can act quickly and decisively enough for refreezing the Arctic and lowering temperatures globally; though it should be "all hands on deck" with the SAI supplemented/complemented with other cooling and protective measures.

Our main problem is persuading one or more global leaders that it is in their interest and the interest of their people to refreeze the Arctic, when other leaders (e.g. DJT) are intent on exploiting a low-ice Arctic despite the implications of unstoppable sea level rise of many metres and unstoppable reconfigurations of air and ocean circulation, altering climates around the world.  CO2 matters must not get in the way.

With Arctic meltdown halted, planetary restoration is on the cards for our future posterity - and for a peace prize!

Seasonal greetings, John

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[Dr. Chris Robert]

Hi John

I'd be grateful if you could point to the bit in Hansen's Pipeline paper where he confirms that 2C will be reached by around 2040.  There's a lot of dense detail in this paper.  I wouldn't claim to be master of it all, but I don't think it does what you say.

Can you also provide a source for your statement that 'CDR cannot realistically reduce temperatures this century' and detail the emissions scenario(s) that it relates to?  What exactly does 'reduce temperatures' mean?  Lower than than are now?  Lower than they would be without intervention?  Or lower than some other benchmark?  And how much lower than the relevant benchmark do they need to be to be significant?

I know it's Christmas, a time of goodwill to all.  It would be good if you will be temper your passion with a little more precision.  Those on this list are the choir, there's no need to preach to us about decarbonisation not being enough.  We need coherent arguments properly supported by data.  

As to whether WTF is right or wrong, I have no way to confirm that one way or another.  I wasn't among the climate scientists that developed its central logic.  All I can tell you is what it spits out when you feed it with different diets.  If people consider it to be an unreliable suite of algorithms for forecasting global warming, so be it.  Personally, I get some comfort from its provenance and from its wider acceptance within the climate science community.  I also get some comfort from the fact that when it reconstructs the global surface temperature from 1750 to 2024, it comes up within 0.05C of the observational record.  I see no reason to regard 2024 as a turning point after which the climate will follow a radically different dynamic from what it did previously.  That will probably happen at some point when we've triggered enough tipping events, but I don't believe we're quite there yet.  To be clear, I'm not saying that we haven't already triggered some key tipping events, what I'm saying is that the inertia in the climate system is such that even if we have, the phase changes they will in due course deliver, are not yet apparent.

Anyway, in the absence of clear and unambiguous reference to Hansen, or some other recognised authority, I hope you won't mind if I regard your criticism as ill-founded.

Regards

Robert

[Douglas Grandt]

Happy Boxing Day, Robert and John,

Robert, in the attached temperature trends and targets graphic, this footnote (^) may answer your first request:

^Rapid decarbonization would remove SO2 cooling and could cause a doubling of the rate of global warming over the next 25 years as compared to the last 40, see Hansen et al. July Temperature Update: Faustian Payment Comes Due, published 13 August 2021.

John, triggered by Robert’s additional request, perhaps it’s time to update the curves and pertinent footnotes. 

Cheers,

Doug 

Archived at Bit.ly/PRAGfundamentals

Sent from my iPhone (audio texting)

On Dec 26, 2025, at 2:42 PM, Dr. Chris Robert <robert...@gmail.com> wrote:



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[Dr. Chris Robert]

Hi Doug

Try again.  That quote does not appear in the Hansen posting cited.

Regards

Robert

[David Spratt]

The high-emission scenarios in CMIP6, which we are currently tracking, also have 2C by 2040, as illustrated.

Hansen said in November that reality is "close to the extreme RCP8.5 scenario” (https://jimehansen.substack.com/p/warning-this-colorful-chart-is-censored).

With current warming at 1.5C in practical terms, and current decadal rate likely in the range 0.3-0.35C/decade, 2C around 2040 seems locked in given current political inertia and projections from the most recent Production Gap report projecting emissions in 2050 will only be 5-10% lower than at present.

David Spratt

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[Douglas Grandt]

Robert,

Footnote^ is not a Hansen quote. It is an interpretation and description of the curve on the graph.

The actual Hansen quote that is the basis for footnote^ is:

“We should expect the global warming rate for the quarter of a century 2015-2040 to be about double the 0.18°C/decade rate during 1970-2015 (see Fig. 2), unless appropriate countermeasures are taken.”

July Temperature Update: Faustian Payment Comes Due

13 August 2021

James Hansen and Makiko Sato

https://www.columbia.edu/~mhs119/Temperature/Emails/July2021.pdf

There are a variety of interpretations of the number of years of the base period of 40—45—50 (choose one of your liking), including, notably, Inside Climate News: 

The Rate of Global Warming During Next 25 Years Could Be Double What it Was in the Previous 50, a Renowned Climate Scientist Warns

Former NASA climate scientist James Hansen urged Congress decades ago to act on climate change. Now he says he expects reduced aerosol pollution to lead to a steep temperature rise.

By Bob Berwyn

September 15, 2021

How would you graphically represent what Hansen et al. wrote, and how would you footnote the basis of your interpretation?

Best,

Doug

Sent from my iPhone (audio texting)

On Dec 26, 2025, at 3:52 PM, Dr. Chris Robert <robert...@gmail.com> wrote:



Hi Doug

Try again.  That quote does not appear in the Hansen posting cited.

Regards

Robert

On 26/12/2025 20:15, Douglas Grandt wrote:

Happy Boxing Day, Robert and John,

Robert, in the attached temperature trends and targets graphic, this footnote (^) may answer your first request:

^Rapid decarbonization would remove SO2 cooling and could cause a doubling of the rate of global warming over the next 25 years as compared to the last 40, see Hansen et al. July Temperature Update: Faustian Payment Comes Due, published 13 August 2021.

John, triggered by Robert’s additional request, perhaps it’s time to update the curves and pertinent footnotes. 

Cheers,

Doug 

To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/5f23b18c-b53f-40a4-a59c-e5a9985bacf9%40gmail.com.

[Dr. Chris Robert]

Doug & John

That's fine and that doesn't conflict with what I said.  The key words in the Hansen quote are 'unless appropriate countermeasures are taken'.  His comment assumes, as he does in PIpeline, that emissions will continue at much the same rate as they are now, or at least that atmospheric CO2 concentration will remain at its current level.  My observation that WTF shows warming stabilising at ~1.8C is based upon there being such 'countermeasures', namely the more or less immediate elimination of fossil fuel emissions.

Of course, for practical purposes we all know that isn't going to happen. The point about the boundary case in which we have notional immediate zero emissions is that it sets a lowest theoretical limit to decarbonisation (short of that and massive immediate CDR, which isn't going to happen either).  If we know that theoretically decarbonisation literally cannot deliver anything less than +1.8C, it follows that if you want 1.5C or even less, you're going to have to get another string in your bow.  The physics tells us that there is only one other string available, namely, SRM.  QED.

Once the facts force people to come to terms with the emotional blockage that obliges them to rely solely on decarbonisation, then we can begin a sensible discussion of how much SRM, by what means, where and when.  But none of that can start until there's an acceptance that it's necessary.  My whole position on SRM hangs on what I consider to be the one critical obstacle - a flawed belief that SRM might not be necessary.  This is an irresistible impediment to investing at the scale and speed necessary to provide any realistic chance of it being available at scale and in good time for deployment before it's too late.  We will get nowhere with SRM until sufficient numbers of the right people acknowledge that decarbonisation is no longer sufficient and SRM is therefore now necessary.  The details will quickly fall into place once that penny has dropped.

In the meantime, banging on about all the different ways of approaching SRM and responding to all the issues it raises, provide a monumental distraction from discussing the BIG ISSUE, which is that if your objective is to avert the inevitable widespread societal and ecosystem collapse that our current path will entail, DECARBONISATION IS NO LONGER SUFFICIENT AND SRM IS NOW NECESSARY.  Get over it!

WTF tells you all that very clearly.  Here's an example to prove the point.

Emissions peak at 40GtCO₂yr^-1 in 2026 and go to zero in 2027, plus CDR starts in 2026 and goes to 40GtCO₂yr^-1 in 2027 before gradually declining to zero in 2100.  This profile, with no SRM delivers stable warming of +1^oC from 2060 having peaked at +1.7^oC in 2028.  That isn't going to happen either but WTF says that if, by some miracle, it did, that would be the surface temperature impact.

Regards

Robert

[Douglas Grandt]

Robert,

Apologies for inadvertently neglecting to focus attention on the 2040 2°C portion of the extrapolated trajectory to 6.3°C in 100 years (2125) as discussed thoroughly here in 2023, as you will surely recall.

Cheers,

Doug 

Sent from my iPhone (audio texting)

On Dec 26, 2025, at 7:27 PM, Dr. Chris Robert <robert...@gmail.com> wrote:



Doug & John

That's fine and that doesn't conflict with what I said.  The key words in the Hansen quote are 'unless appropriate countermeasures are taken'.  His comment assumes, as he does in PIpeline, that emissions will continue at much the same rate as they are now, or at least that atmospheric CO2 concentration will remain at its current level.  My observation that WTF shows warming stabilising at ~1.8C is based upon there being such 'countermeasures', namely the more or less immediate elimination of fossil fuel emissions.

Of course, for practical purposes we all know that isn't going to happen. The point about the boundary case in which we have notional immediate zero emissions is that it sets a lowest theoretical limit to decarbonisation (short of that and massive immediate CDR, which isn't going to happen either).  If we know that theoretically decarbonisation literally cannot deliver anything less than +1.8C, it follows that if you want 1.5C or even less, you're going to have to get another string in your bow.  The physics tells us that there is only one other string available, namely, SRM.  QED.

Once the facts force people to come to terms with the emotional blockage that obliges them to rely solely on decarbonisation, then we can begin a sensible discussion of how much SRM, by what means, where and when.  But none of that can start until there's an acceptance that it's necessary.  My whole position on SRM hangs on what I consider to be the one critical obstacle - a flawed belief that SRM might not be necessary.  This is an irresistible impediment to investing at the scale and speed necessary to provide any realistic chance of it being available at scale and in good time for deployment before it's too late.  We will get nowhere with SRM until sufficient numbers of the right people acknowledge that decarbonisation is no longer sufficient and SRM is therefore now necessary.  The details will quickly fall into place once that penny has dropped.

In the meantime, banging on about all the different ways of approaching SRM and responding to all the issues it raises, provide a monumental distraction from discussing the BIG ISSUE, which is that if your objective is to avert the inevitable widespread societal and ecosystem collapse that our current path will entail, DECARBONISATION IS NO LONGER SUFFICIENT AND SRM IS NOW NECESSARY.  Get over it!

WTF tells you all that very clearly.  Here's an example to prove the point.

Emissions peak at 40GtCO₂yr^-1 in 2026 and go to zero in 2027, plus CDR starts in 2026 and goes to 40GtCO₂yr^-1 in 2027 before gradually declining to zero in 2100.  This profile, with no SRM delivers stable warming of +1^oC from 2060 having peaked at +1.7^oC in 2028.  That isn't going to happen either but WTF says that if, by some miracle, it did, that would be the surface temperature impact.

Regards

Robert

On 26/12/2025 22:50, Douglas Grandt wrote:

Robert,

Footnote^ is not a Hansen quote. It is an interpretation and description of the curve on the graph.

The actual Hansen quote that is the basis for footnote^ is:

“We should expect the global warming rate for the quarter of a century 2015-2040 to be about double the 0.18°C/decade rate during 1970-2015 (see Fig. 2), unless appropriate countermeasures are taken.”

July Temperature Update: Faustian Payment Comes Due

13 August 2021

James Hansen and Makiko Sato

https://www.columbia.edu/~mhs119/Temperature/Emails/July2021.pdf

<image0.jpeg>

<image1.jpeg>

There are a variety of interpretations of the number of years of the base period of 40—45—50 (choose one of your liking), including, notably, Inside Climate News: 

The Rate of Global Warming During Next 25 Years Could Be Double What it Was in the Previous 50, a Renowned Climate Scientist Warns

Former NASA climate scientist James Hansen urged Congress decades ago to act on climate change. Now he says he expects reduced aerosol pollution to lead to a steep temperature rise.

By Bob Berwyn

September 15, 2021

[Dr. Chris Robert]

Hi Doug

I don't recall these charts but don't take that personally.  I read stuff I wrote last month and don't recall that either!

Looking at the charts afresh, I don't understand them.  There's no legend explaining what the various lines are charting and the reference to 63% of equilibrium temperature after 100 years suggests that this refers to a single emissions pulse and not to a continuous stream of emissions.

However, it was nice to see that you produced this chart on my birthday!

Regards

Robert

[Bruce]

Hi Robert -

As you know I used Google to review the limitations in the Fair model that you use and found that it was not designed to work with extremes (like zero emissions in 2027 or 40 GTCO2 of CCR in 2027). I think it would be helpful for you to explain the sorts of emissions, Cdr, and SRM pathways for which your model likely provides reasonable results .

Cheers!

Bruce

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From: healthy-planet-...@googlegroups.com <healthy-planet-...@googlegroups.com> on behalf of Dr. Chris Robert <robert...@gmail.com>
Sent: Friday, December 26, 2025 7:27 PM
To: Douglas Grandt <answer...@mac.com>
Cc: John Nissen <johnnis...@gmail.com>; Sev Clarke <sevc...@me.com>; H simmens <hsim...@gmail.com>; Robert Tulip <rob...@rtulip.net>; Clive Elsworth <Cl...@endorphinsoftware.co.uk>; healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>; Planetary Restoration <planetary-...@googlegroups.com>; Albert Kallio <albert...@hotmail.com>
Subject: Re: [prag] Re: [HPAC] Re: The number of prospective climate solutions narrows still further

 

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[Dr. Chris Robert]

Hi David

WTF calculates that if we follow the SSP2-4.5 trajectory we'll be at +1.9C by 2040, and if we follow SSP5-8.5, we'll be at +2.0C.  So it seems to be in close agreement with the projections you cited.

The WTF respective warmings to 2100 are +2.8C and +4.9C.  They also seem to be pretty close the corresponding figures in your chart.

All good stuff!  Makes me feel more positive about the quality of WTF's forecasts.  Thanks.

Regards

Robert

[Douglas Grandt]

Robert,

That expanded graphic was created 28 Feb 2023 on my understanding of your meticulous explanation of Hansen’s 10°C “equilibrium temperature” (December 13 preprint Bit.ly/Hansen-arXivDec22), which few, if any of those in the discussion thread understood.

I distributed it in the attached email ⬇️

Cheers,

Doug

Begin forwarded message:

From: Douglas Grandt
Date: Feb 28, 2023 at 9:13PM EST
To: John Nissen 
Cc: Planetary Restoration, healthy-planet-action-coalition, Eelco Rohling, Doug MacMartin, Shaun Fitzgerald, Hugh.Hunt, Monica Morrison, Mike MacCracken, Bruce Melton
Subject: Re: [prag] Re: PRAG meeting Monday 27th February 8 pm UK time

John et al.

I felt a need to put the Hansen 10°C “equilibrium temperature” into perspective with PRAG’s “Trends and Targets for Temperature and CO2e” diagram prompted by an discussion on another thread “ Make Sunsets stimulates more debate over "Geoengineering"- PT Barnum further vindicated!” 

I created the attached hybrid graphic to illustrate what Hansen describes in the December 13 preprint (Bit.ly/Hansen-arXivDec22). Comments posted by RobertC and Ye Tao validate the approximate shape of the dashed red curve that approaches 10°C asymptotically at t = ♾️.

Hansen wrote on page 13, “The e-folding time – the time for surface temperature to reach 63% of its equilibrium response – was about a century.” 

And on page 19, “… equilibrium global warming for today’s GHG level is 10°C” 

[ … without aerosols.]

Visuals help me to understand complicated scientific concepts.

I hope the hybrid diagram helps clarify. 

Cheers,

Doug

P.S.  I dropped off the zoom a bit after 9pm (UK) so I missed the outreach section. FYI, I continue my daily nurturing / building / solidifying sensitive, tenuous and fledgling relationships with Bill McKibben, Michael Mann and Sámi acquaintances from 2016 at Standing Rock—the pace is picking up with the current barrage of news. 

Sent from my iPhone (audio texting)

Sent from my iPhone (audio texting)

On Dec 27, 2025, at 8:13 AM, Dr. Chris Robert <robert...@gmail.com> wrote:



Hi Doug

I don't recall these charts but don't take that personally.  I read stuff I wrote last month and don't recall that either!

Looking at the charts afresh, I don't understand them.  There's no legend explaining what the various lines are charting and the reference to 63% of equilibrium temperature after 100 years suggests that this refers to a single emissions pulse and not to a continuous stream of emissions.

However, it was nice to see that you produced this chart on my birthday!

Regards

Robert

On 27/12/2025 01:56, Douglas Grandt wrote:

Robert,

Apologies for inadvertently neglecting to focus attention on the 2040 2°C portion of the extrapolated trajectory to 6.3°C in 100 years (2125) as discussed thoroughly here in 2023, as you will surely recall.

Cheers,

Doug 

<image0.jpeg>

[Douglas Grandt]

Robert,             ERRATA

Please pardon the typo. The creation date should be February 26, 2023, your birthday apparently 🤩 forgive me 🙏

Doug

Sent from my iPhone (audio texting)

On Dec 27, 2025, at 9:36 AM, Douglas Grandt <answer...@mac.com> wrote:

…

[Tom Goreau]

WHAT, ONLY 100 YEARS?

 

You need to go at least a few thousand years to finish the in-the-pipeline ocean warming, perhaps more if the ocean becomes more vertically stratified and the overturning circulation slows down, plus several millenia more for Antarctica to melt, absorbing solar heat without raising temperature due to the latent heat of melting, only as long as there is ice left to melt.

 

Some 70 meters of sea level rise to go, sooner or later, time will tell how much, because none of these models can be usefully extrapolated that far without  hitting unanticipated non-linear destabilizing feedbacks, such as mass die offs from new diseases and pests or widespread ocean anoxia.

 

From: 'Douglas Grandt' via Healthy Planet Action Coalition (HPAC) <healthy-planet-...@googlegroups.com>
Date: Saturday, December 27, 2025 at 09:36
To: Dr. Chris Robert <robert...@gmail.com>
Cc: John Nissen <johnnis...@gmail.com>, Sev Clarke <sevc...@me.com>, H simmens <hsim...@gmail.com>, Robert Tulip <rob...@rtulip.net>, Clive Elsworth <Cl...@endorphinsoftware.co.uk>, healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>, Planetary Restoration <planetary-...@googlegroups.com>, Albert Kallio <albert...@hotmail.com>
Subject: Re: [prag] Re: [HPAC] Re: The number of prospective climate solutions narrows still further

 

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.
To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/EF331890-136A-40A8-9221-16B983722E5D%40mac.com.

[Dr. Soumitra Das]

I strongly agree with Herb that the most urgent task before us is to engage and lobby governments—especially those with global influence and those already on the front lines of climate impact. Without serious engagement from key governments, I see little chance of achieving any credible global pathway or accord for climate intervention.

At the Healthy Climate Initiative (HCI), this is exactly where we are concentrating our efforts. With very limited resources, we are laying the essential groundwork Herb describes: organizing climate leadership workshops, partnering with local NGOs, convening a Climate Intervention Summit in India, and planning a Global Climate Intervention Conference—alongside carefully designed, small-scale field experiments on sunlight-reflection methods (SRM) to slow glacial melt. At the same time, we are beginning to extend these conversations to neighboring countries across South Asia. The objective is to shift understanding, legitimacy, and confidence among scientists, civil society leaders, policymakers, and decision-makers in regions that are both highly vulnerable and geopolitically consequential.

With the support of funders and partners, we can scale this effort substantially—strengthening advocacy while advancing responsible SRM field research, including MCB and local albedo enhancement, aimed at protecting vulnerable populations from extreme heat. These field experiments are not a substitute for advocacy; they are complementary to it, helping build credibility, confidence, and political seriousness.

Very few organizations are willing to take on the difficult early work of legitimacy-building and sustained government-facing engagement on climate intervention, particularly in the Global South. Yet without this foundation, it is hard to see how larger institutional structures—whether an Albedo Accord or any other framework—can realistically take shape.

This work must succeed. To that end, I am planning to relocate to India next year so I can be more effective on the ground. I would welcome the opportunity to continue thinking together about how we can make this a reality.

Warm regards,
Soumitra

To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/BY3PR13MB4994F97085858F03A52AE62EDDB1A%40BY3PR13MB4994.namprd13.prod.outlook.com.

--

Soumitra Das

Chairman and Executive Director, HCI USA

Chairman, HCI India

https://healthyclimateinitiative.org/

[Michael MacCracken]

Hi Tom--My understanding is that right now what happens as heat is transferred to the deep ocean is that it gets mixed into a quite large mass of deep water to the temperature increase is quite small. So, when this water comes up, the temperature increase would be there, but a good bit smaller than the increment  from where it went down. Now, as you note, the ocean is far from equilibrium. What is your expectation (based, I would presume, on paleoclimatic periods of deep ocean warming) of that the temperature distribution would be at equilibrium? Would we still even have an overturning circulation? If we do, how much warmer might the upwelling water be? Would it be as much warmer as the less-than-global-average-temperature increase that now characterizes low latitude warming?

Best, Mike

To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/BY3PR13MB4994F97085858F03A52AE62EDDB1A%40BY3PR13MB4994.namprd13.prod.outlook.com.

[Tom Goreau]

You’re right, its a small temperature increase in so large a volume, but still an enormous amount of heat to re-equilibrate to the atmosphere when the water comes back up from the abyss.

 

As long as we are on a monotonic atmospheric warming curve, the ocean will continue to warm as fast as the overturning circulation limits it. If we lower atmospheric temperature, it will take a few thousand years for the ocean to cool the new equilibrium, slowly releasing heat as it does.

 

I wouldn’t dare make a hard prediction of how much the air temperature rise would be from regurgitated ocean heat, because upwelling is highly nonlinear and rates uncertain. I’m not a modeler but a hard-core empiricist: wait and see what happens, because it probably won’t be what we expect or hope for.

[Jesper Pedersen]

Dear Colleagues

 

I Hope everyone had a Merry Christmas 🎄
Wishing everyone a prosperous New Year filled with success and growth.
In June, JP ClimaTec attended at the Arctic Repair 2025 Conference at University Of Cambridge, solutions for a warming World, which was very exciting.
JP ClimaTec works continuously on improvements on this climate cooling concept and are looking for collaboration partners in order to build the concept.  

Short information of this climate cooling proposal:

Adiabatic humidification cooling and higher albedo value.
Due to adiabatic humification the air can instantly be cooled from 40 ℃/20% RH to wet bulb temperature 22℃/100 RH,

if 7,5 gram of H2O is evaporated into 1000 grams of air.
Cold air can hold less absolute amount of water vapor gram H2O/ kg dry air than hot air does,

and water vapor itself is actually a greenhouse gas, so the task is to reduce the absolute amount of water vapor in the atmosphere.

See also Molliers diagram.
Air at 22 ℃ can hold 16,5 g H2O, and at 40 ℃ the air can hold 50 g H2O before dewpoint.
If the humidification process is activated in the afternoon,

then it's expected that the temperature the next morning will be lower than without this humidification process.

During the night the water vapor is removed from the air again, the water vapor reevaporates from the soil and provide cooling again the next day,

and result in increased cloud formation, which increases the Earth's albedo, and reflect sunshine.

The energy to operate the fan and pumps, must come from renewables such as wind turbines.  

Benefits of adiabatic water mist cooling and increasement of Earth’s Albedo.
•Helps to increase the velocity of reforestation
•Prevent forest fires
•Reduces the temperature on the planet, to the same temperature as before the pre-industrialization
•Stop the ice melting at the poles
•Stabilize the sea level risen
•Prevent tipping points
•Transform desert areas into fertile farmlands
•Turns sand areas into soil which act as carbon sink
•Helps to rehydrate the Earth, reestablish the biotic pump and small water cycles.

Hopefully 2026 will be the Year where this solar geoengineering concept will be put into operation.

Feel free for questions or comments.

 

All the best.

 

Med venlig hilsen/ Best regards

Jesper Pedersen

CEO-Founder

JP ClimaTec

Phone: +45 20417023

Mail: j...@innochiller.com

Web: www.jpclimatec.com

 

 

[David Spratt]

Regarding time till full warming is realised:

Thermal inertia or Climate response function 

If there is  a pulse of CO2 into the atmosphere, time to realise warming:

Instantaneous 0% of warming realised

10 years 50% "

100 years 60-70% "

500-1000 years 75-80% "

10,000+years 100% "

More at: https://term.sustainability-directory.com/term/climate-response-function

David Spt\ratt

^Rapid decarbonization would remove SO2 cooling and could cause a doubling of the rate of global warming over the next 25 years as compared to the last 40, see Hansen et al.July Temperature Update: Faustian Payment Comes Due, published 13 August 2021.

 

John, triggered by Robert’s additional request, perhaps it’s time to update the curves and pertinent footnotes. 

 

Cheers,

Doug 

 

<image0.jpeg>

 

Archived at Bit.ly/PRAGfundamentals

 

 

Sent from my iPhone (audio texting)

On Dec 26, 2025, at 2:42 PM, Dr. Chris Robert<robert...@gmail.com>wrote:

 

Hi John

I'd be grateful if you could point to the bit in Hansen's Pipeline paper where he confirms that 2C will be reached by around 2040.  There's a lot of dense detail in this paper.  I wouldn't claim to be master of it all, but I don't think it does what you say.

Can you also provide a source for your statement that 'CDR cannot realistically reduce temperatures this century' and detail the emissions scenario(s) that it relates to?  What exactly does 'reduce temperatures' mean?  Lower than than are now?  Lower than they would be without intervention?  Or lower than some other benchmark?  And how much lower than the relevant benchmark do they need to be to be significant?

I know it's Christmas, a time of goodwill to all.  It would be good if youwill be temper your passion with a little more precision.  Those on this list are the choir, there's no need to preach to us about decarbonisation not being enough.  We need coherent arguments properly supported by data.  

As to whether WTF is right or wrong, I have no way to confirm that one way or another.  I wasn't among the climate scientists that developed its central logic.  All I can tell you is what it spits out when you feed it with different diets.  If people consider it to be an unreliable suite of algorithms for forecasting global warming, so be it.  Personally, I get some comfort from its provenance and from its wider acceptance within the climate science community.  I also get some comfort from the fact that when it reconstructs the global surface temperature from 1750 to 2024, it comes up within 0.05C of the observational record.  I see no reason to regard 2024 as a turning point after which the climate will follow a radically different dynamic from what it did previously.  That will probably happen at some point when we've triggered enough tipping events, but I don't believe we're quite there yet.  To be clear, I'm not saying that we haven't already triggered some key tipping events, what I'm saying is that the inertia in the climate system is such that even if we have, the phase changes they will in due course deliver, are not yet apparent.

Anyway, in the absence of clear and unambiguous reference to Hansen, or some other recognised authority, I hope you won't mind if I regard your criticism as ill-founded.

Regards 

Robert

 

On 26/12/2025 19:03, John Nissen wrote:

Hi Robert,

 

What WTF tells you is, I believe, quite wrong:

 

[Quote] What I can tell you is that in the notional boundary case where emissions stop completely in 2026, WTF says that global warming reaches 1.8^oC in the early 2030s and stays there more or less indefinitely. 

No!  That's wishful thinking!  2C will be reached by around 2040, even if emissions were halted in 2026, because of the heating power from legacy CO2 and, increasingly, from lost planetary albedo.  This is confirmed by Hansen in his "Global warming in the pipeline".

 

CDR cannot realistically reduce temperatures this century, as Peter Fiekowsky would like us to believe. So we are left with SRM.  And only SAI can act quickly and decisively enough for refreezing the Arctic and lowering temperatures globally; though it should be "all hands on deck" with the SAI supplemented/complemented with other cooling and protective measures.

 

Our main problem is persuading one or more global leaders that it is in their interest and the interest of their people to refreeze the Arctic, when other leaders (e.g. DJT) are intent on exploiting a low-ice Arctic despite the implications of unstoppable sea level rise of many metres and unstoppable reconfigurations of air and ocean circulation, altering climates around the world.  CO2 matters must not get in the way.

 

With Arctic meltdown halted, planetary restoration is on the cards for our future posterity - and for a peace prize!

 

Seasonal greetings, John

 

 

 

On Fri, Dec 26, 2025 at 5:26 PM Dr. Chris Robert <robert...@gmail.com> wrote:

Hi Sev

I don't seem to have received your message referred to below, perhaps you cold resend it.  But before doing so, could I ask you to reflect on a couple of details that will make it easier for me to put this through WTF.

It's not for WTF to show that any particular amount of fossil fuel emissions reduction, CDR or SRM by any given year is more or less likely.  It can tell you what the algorithms determine would be the global warming impact of any combination of the three, but the 'likelihood' question is about politics, engineering and behaviour change and assessing how they will play out in the future is always going to be a judgement call, not a modelling one. 

What I can tell you is that in the notional boundary case where emissions stop completely in 2026, WTF says that global warming reaches 1.8^oC in the early 2030s and stays there more or less indefinitely.

Where you go from there depends on what outcome you want by when.  For example, still with what is almost certainly an unrealistic zero emissions by 2030, if you wanted to get global warming down to stabilise at +1^oC by 2100 using only CDR, you'd have to start in 2026 and build it to 23GtCO₂yr^-1by 2036, after which it could be eased back to 1GtCO₂yr^-1 by 2150.  This implies aggregate CDR of ~1330GtCO₂ by 2100 before it begins to tail off rapidly.  Whether that amount of CDR in that time frame is feasible is a political and engineering question.  But given that the starting point here is an almost certainly unrealistic emissions reduction profile, this example is probably little more than academic.

It is also worth noting that in this profile, the aggregate overshoot is 40^oCyears - this is a measure of the excess heat above the 1^oC threshold that would be retained in the atmosphere during the period of overshoot.  The importance of this metric is that while occasional high peak temperatures may cause serious and even irreversible harms, a sustained period of less warming will still melt polar ice caps and mountain glaciers elsewhere, and will still accelerate the whole range of other climate change induced harms, albeit more gradually, at least until they are sufficient to reach some critical tipping points.  A second, and possibly more important judgement call is what would be a 'safe' level for this aggregate overshoot.  Note that in 2025 the aggregate overshoot above a 1^oC threshold is ~7^oCyears and that has been sufficient to provoke the various climate change induced losses already witnessed around the world in terms of floods, droughts, wildfires, seal level surges, crop failures, biodiversity loss, heatwave deaths and so on.  Does aggregate overshoot of 40^oCyears represent an unacceptable risk?  In this regard, it is important to know what your reference level is for the global surface temperature anomaly above pre-industrial, for a stable and sustainable climate system.  If your threshold is 1.5^oC, the aggregate overshoot to date has been <<1^oCyear.

So, when responding to this, can I ask you to be specific about the following:

1. What's your threshold (in ^oC) for warming above pre-industrial, for a stable and sustainable climate system?
2. What level of aggregate overshoot (^oCyears) above this threshold, do you consider to be the absolute minimum that would be acceptable?
3. How quickly do you think, realistically given all the social and political realities of the world as it now is and is likely to be in the coming decades, emissions can be reduced?  I need to know in what year and at what level (GtCO₂yr^-1) emissions will peak, and in what year and at what level they will eventually stabilise?  Will emissions ever get to zero or is there likely to be some minimal level of emissions continuing into the distant future?

1. Similarly, what do you consider to be the most realistic aggressive CDR profile that could be achieved, again starting when, and reaching how many GtCO₂yr^-1by when?  Remember that this is both capture ANDpermanent sequestration.

To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/BY3PR13MB4994F97085858F03A52AE62EDDB1A%40BY3PR13MB4994.namprd13.prod.outlook.com.

[David Spratt]

re: Committed warming

The work by Susan Solomon and others around 15 years ago found that if CO2 emissions cease, the future atmospheric warming (due to thermal inertia/climate response function) is roughly offset by the (deep) ocean continue to take down heat, such that the equilibrium  temperature is around about the temperature when emission ceased.  This of course is in a model without aerosols of the non-CO2 well-mixed gases.

Some of the literature…

Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO2

https://bg.copernicus.org/articles/17/2987/2020/

All models conducted an experiment where atmospheric CO2 concentration increases exponentially until 1000 PgC has been emitted. Thereafter emissions are set to zero and models are configured to allow free evolution of atmospheric CO2 concentration. Many models conducted additional second-priority simulations with different cumulative emission totals and an alternative idealized emissions pathway with a gradual transition to zero emissions. The inter-model range of ZEC 50 years after emissions cease for the 1000 PgC experiment is −0.36 to 0.29 ∘C, with a model ensemble mean of −0.07 ∘C, median of −0.05 ∘C, and standard deviation of 0.19 ∘C. Models exhibit a wide variety of behaviours after emissions cease, with some models continuing to warm for decades to millennia and others cooling substantially. Analysis shows that both the carbon uptake by the ocean and the terrestrial biosphere are important for counteracting the warming effect from the reduction in ocean heat uptake in the decades after emissions cease.

Solomon, S., G. Pattner, et al. (2009), "Irreversible climate change due to carbon dioxide emissions", PNAS 106(6): 1704-1709. 10 February 2009.

Climate change from CO2 irreversible for 1000 years after emissions stop. See Fig 1. The severity of damaging human-induced climate change depends not only on the magnitude of the change but also on the potential for irreversibility. This paper shows that the climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop. Following cessation of emissions, removal of atmospheric carbon dioxide decreases radiative forcing, but is largely compensated by slower loss of heat to the ocean, so that atmospheric temperatures do not drop significantly for at least 1,000 years. Among illustrative irreversible impacts that should be expected if atmospheric carbon dioxide concentrations increase from current levels near 385 parts per million by volume (ppmv) to a peak of 450–600 ppmv over the coming century are irreversible dry-season rainfall reductions in several regions comparable to those of the ‘‘dust bowl’’ era and inexorable sea level rise. Thermal expansion of the warming ocean provides a conservative lower limit to irreversible global average sea level rise of at least 0.4 –1.0 m if 21st century CO2 concentrations exceed 600 ppmv and 0.6 –1.9 m for peak CO2 concentrations exceeding  1,000 ppmv. Additional contributions from glaciers and ice sheet contributions to future sea level rise are uncertain but may equal or exceed several meters over the next millennium or longer.

Matthews, H. D. and K. Caldeira (2008), "Stabilizing climate requires near-zero emissions", Geophysical Research Letters 35: L04705.

Current international climate mitigation efforts aim to stabilize levels of greenhouse gases in the atmosphere. However, human-induced climate warming will continue for many centuries, even after atmospheric CO2 levels are stabilized. In this paper, we assess the CO2 emissions requirements for global temperature stabilization within the next several centuries, using an Earth system model of intermediate complexity. We show first that a single pulse of carbon released into the atmosphere increases globally averaged surface temperature by an amount that remains approximately constant for several centuries, even in the absence of additional emissions. We then show that to hold climate constant at a given global temperature requires nearzero future carbon emissions. Our results suggest that future anthropogenic emissions would need to be eliminated in order to stabilize global-mean temperatures. As a consequence, any future anthropogenic emissions will commit the climate system to warming that is essentially irreversible on centennial timescales.

David Spratt

To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/BY3PR13MB499457A7AE5711EF2817742EDDB1A%40BY3PR13MB4994.namprd13.prod.outlook.com.

[Sev Clarke]

Hi Robert,

See my answers below in bold.

On 27 Dec 2025, at 4:26 am, Dr. Chris Robert <robert...@gmail.com> wrote:

Hi Sev

I don't seem to have received your message referred to below, perhaps you cold resend it.  But before doing so, could I ask you to reflect on a couple of details that will make it easier for me to put this through WTF.

It's not for WTF to show that any particular amount of fossil fuel emissions reduction, CDR or SRM by any given year is more or less likely.  It can tell you what the algorithms determine would be the global warming impact of any combination of the three, but the 'likelihood' question is about politics, engineering and behaviour change and assessing how they will play out in the future is always going to be a judgement call, not a modelling one.  Accepted. I judge that social acceptability of the methods will be a combination of ground up, desperation, and top down methods. 

What I can tell you is that in the notional boundary case where emissions stop completely in 2026, WTF says that global warming reaches 1.8^oC in the early 2030s and stays there more or less indefinitely. With our SRM methods we should be able to lower that by 2050.

Where you go from there depends on what outcome you want by when.  For example, still with what is almost certainly an unrealistic zero emissions by 2030, if you wanted to get global warming down to stabilise at +1^oC by 2100 using only CDR, you'd have to start in 2026 and build it to 23GtCO₂yr^-1 by 2036, after which it could be eased back to 1GtCO₂yr^-1 by 2150.  This implies aggregate CDR of ~1330GtCO₂ by 2100 before it begins to tail off rapidly.  Whether that amount of CDR in that time frame is feasible is a political and engineering question.  But given that the starting point here is an almost certainly unrealistic emissions reduction profile, this example is probably little more than academic.

It is also worth noting that in this profile, the aggregate overshoot is 40^oCyears - this is a measure of the excess heat above the 1^oC threshold that would be retained in the atmosphere during the period of overshoot.  The importance of this metric is that while occasional high peak temperatures may cause serious and even irreversible harms, a sustained period of less warming will still melt polar ice caps and mountain glaciers elsewhere, and will still accelerate the whole range of other climate change induced harms, albeit more gradually, at least until they are sufficient to reach some critical tipping points.  A second, and possibly more important judgement call is what would be a 'safe' level for this aggregate overshoot.  Note that in 2025 the aggregate overshoot above a 1^oC threshold is ~7^oCyears and that has been sufficient to provoke the various climate change induced losses already witnessed around the world in terms of floods, droughts, wildfires, seal level surges, crop failures, biodiversity loss, heatwave deaths and so on.  Does aggregate overshoot of 40^oCyears represent an unacceptable risk?  In this regard, it is important to know what your reference level is for the global surface temperature anomaly above pre-industrial, for a stable and sustainable climate system.  If your threshold is 1.5^oC, the aggregate overshoot to date has been <<1^oCyear.

So, when responding to this, can I ask you to be specific about the following:

1. What's your threshold (in ^oC) for warming above pre-industrial, for a stable and sustainable climate system? 1^oC, but preferably 0.5C.
2. What level of aggregate overshoot (^oCyears) above this threshold, do you consider to be the absolute minimum that would be acceptable? Perhaps 17^oCyears, but as a maximum.
3. How quickly do you think, realistically given all the social and political realities of the world as it now is and is likely to be in the coming decades, emissions can be reduced?  If several nations decide that my concepts, including methane-splitting into turquoise hydrogen and graphene co-products, are worth throwing some serious resources at in this decade of the 2020s, then the peak emissions of 45GtCO2/yr should be around 2042 (not much different from those of today, but this assumes that major arctic burps not have occurred in the intervening period. These would make the task much harder, and longer but still not impossible given GHG radiative saturation effects).
   . I need to know in what year and at what level (GtCO₂yr^-1) emissions will peak, and in what year and at what level they will eventually stabilise?  Assume that emissions peak as above and that by 2060 they will stabilise at 15GtCO₂yr^-1 
   Will emissions ever get to zero or is there likely to be some minimal level of emissions continuing into the distant future? No, however for the latter half of this century they could, by our efforts, be more than offset by CDR/ISA.
4. Similarly, what do you consider to be the most realistic aggressive CDR profile that could be achieved, again starting when, and reaching how many GtCO₂yr^-1 by when?  Remember that this is both capture AND permanent sequestration. Permanent sequestration is illusory. The best we can hope for is stabilisation for durations typically between a century and 1.5 millennia, mainly in the forms of dissolved marine bicarbonate, sediments and soil biochar. Realistic aggressive CDR, starting at 2Gt CO2/yr, might commence as early as 2040 using Buoyant Flakes, accompanied later by other nature-based methods. By 2060 overall the CDR growth should amount to 30GtCO2/yr and perhaps 40 by 2075.  

Armed with these expectations, I'll then tell you what WTF assesses to be the global warming impact, and how much SRM, if any, is needed to deliver your chosen acceptable amount of aggregate overshoot.  Rather, please show me what would be the effects of SRM/TRM measures increasing to and stabilising at 2.5W/m2 by 2047, mainly due to the combination of Buoyant Flakes and nanobubbles, but including DMS, MCB+evapotranspiration, and Ice Shield+ SRM methods.  If necessary and with considerable effort, these effects might be increased to 5W/m2. Please resist the temptation to answer  questions 3 and 4 with what you'd like to see happen, or what you think could happen in a perfect world in which optimal choices were always made, and focus rather on what, given all the constraints in the real world, you consider to be feasible.  This is not the place for hope and optimism, it's the place for hard-headed unsentimental realism.  If it's easier for these answers, give ranges that your gut tells you cover a 95% confidence interval. We are in for wild times, where confidence is an unattainable luxury.

If others wish to engage with this, I'd be very happy to process your assumptions if you're struggling to do it yourselves with the shared copy of WTF. Please do process my assumptions and make the results, and modifications thereto, available to HPAC.

Regards

RobertC

Cheers,

Sev

[rob...@rtulip.net]

Hi Soumitra

 

This is all excellent strategy that you outline.  I always appreciate reading your perspective.  The one area where I would suggest a different line is that you have not discussed the role of the private sector.

 

The main argument I am developing in my forthcoming book on the Albedo Accord is that a number of key industries have a strong commercial incentive to support sunlight reflection.  Indeed, they should be thoroughly alarmed about the business risks posed by unchecked warming, and by the inability of carbon action to mitigate these risks.  I believe that lobbying these industries – notably insurance, banking, agriculture, tourism, shipping and energy – is essential to generate the funds needed to lobby governments to accept the urgency of albedo restoration.

 

I am currently reading a book on the Montreal Protocol.  I was reminded that a main reason it has succeeded, with universal ratification and ongoing support, is the strong support it received from Margaret Thatcher and Ronald Reagan.  They are both somewhat demonised in popular leftist memory.  This presents an important lesson.   I have noticed that the climate activist movement has drifted far to the political left, to the point that it is simply ignored by the commercial world.  This is not a tenable situation.  Climate proposals require bipartisan support to succeed, as a key lesson from protection of the ozone layer.  There is no way opposition to fossil fuels will gain bipartisan support in the current polarised political world.  That makes sunlight reflection even more essential.

 

Getting the business community on board with sunlight reflection will require a hard tactical think about carbon policy.  Robert Chris’s superb WTF program indicates, as I read it, that the scale and speed of SRM over the next decades matters enormously to future climate stability, whereas the difference between carbon business as usual and feasible levels of decarbonisation is not going to have much heat impact in the immediate future.  That suggests there is space for a deeper discussion about optimal response mix, opportunity cost, and how carbon action has crowded out sunlight reflection. 

 

For example in Australia, the federal conservative coalition has rejected the slogan ‘net zero by 2050’ on economic and security grounds.  To avoid being tagged as deniers, I have argued that they should support sunlight reflection.  Unfortunately the political domination of climate activism by leftists means this argument is too confusing to get traction.  That is why I see lobbying the business community as an essential precursor to lobbying governments, as a necessary way to get the scale of influence and credibility needed..

 

Please donate to HPAC to build capacity to engage the climate debate.

 

Best wishes for the new year.

 

Regards

 

Robert Tulip

 

[oswald....@hispeed.ch]

Hello Jesper,

 

great to see you here😊

 

On first sight: Injecting 7.5 grams of H20 in 1000 kg of air appears to be a non-scalable engineering task, if you talk about significant global temperature reduction. It might be worth considering in regional application e.g. over the Sahara, but then the wind will blow it out. Also the only large water source in such regions is the ocean, which means the water is salty. Would that work?

 

All in all: Too expensive on first sight… but you are welcome to convince me otherwise!

 

Regards

 

Oswald Petersen

Author of „GeoRestoration – Cool the Climate with Natural Energy“

Atmospheric Methane Removal AG

Lärchenstr. 5

CH-8280 Kreuzlingen

Tel: +41-71-6887514

Mob: +49-177-2734245

https://amr.earth

https://georestoration.earth

https://cool-planet.earth

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[Jesper Pedersen]

Hey Oswald

 

Thank you very much for your response and questions.

The specific design of the evaporator unit, is very similar to the “Air blast sprayer-Orchard sprayer” and “Mist America 360 Patio cooler”, where the purpose is to achieve maximum spray diameter.

The Power Breezer mach 4,0 also uses the difference between the actual temperature and the wet bulb temperature for local cooling purpose.  

Regarding the cooling performance of adiabatic humidification cooling where 7,5 gram of evaporated water can cool down 1000 gram of air with 18 , from 40 to 22 , it hereby only requires 0,42 gram of water to cool down 1000 gram of air with 1 . This is a very efficient cooling method.

 

Lets say the air temperature in the afternoon time is 40 and 20% RH, then the temperature will immediately drop to the dew point, 22 , 100 % RH (Abs. humidity 16,5 g H2O/kg dry air)

During the night the Earth act as a dehumidifier where water vapor is removed from the air, and lets say during the night the air temperature drops from 22 to 10 in the morning, at 10  the absolute humidity is 8,0 g H2O/kg dry air, and 8,5 g is hereby removed from the air, during the night, which will reevaporate into the air again during the next day, and provides a cooling effect again for the climate.

I have calculated that the cooling performance can be up to 3000 kW for each kW input power before the higher albedo value is taken into account (Increased cloud formation)  

 

The most efficient snow cannon on the market can produce snow at +2 , if the air is dry enough before the water evaporates into the air and form snow.

When the air is dry the wet bulb temperature is much lower than the actual temperature, and when water is evaporated into the air,

it’s possible to lower the temperature down to the dew point temperature. This means that the evaporator cannon mounted on top of the wind turbine,

can help to cool down the arctic environment as well.  

 

Michal Kravcik and Anastassia Makarieva have mentioned for many years that rehydrate the Earth, and reestablish the biotic pump will lower the temperature on the Earth, and dried landscape is one of the reasons for global warming.

www.youtube.com/live/dFUUrL2iAos

 

University of Cambridge also tests cooling by fogging concept.

Field experiment test at Great Barrier Reef - Cooling by fogging and MCB

www.youtube.com/watch?v=MxHSCVmUktI&t=140s

 

This series also mention that one solution to handle global warming is wet lands, and a natural cooling solution is explained 6:45 minutes in below video.

Cool The country Building a Biotic Pump

www.youtube.com/watch?v=JGKn2WDaQCY&list=PLUr-ByGbQgAkdA6PQr-lb8z1t4gX3_qHV&index=3&t=568s

 

Salt water can be changed to fresh water using a desalination plant for global irrigation, which of course also cost money.

The cheapest way is harvesting melt water in the mountains and evaporate the water into the air, similar to current snow cannons.

 

I hopes above explanation convinces you that my climate cooling proposal will be an efficient solution to tackle global warming.

 

Feel free everyone for questions or comments to my climate cooling proposal.

 

Thanks in advance.

 

Med venlig hilsen/ Best regards

Jesper Pedersen

CEO-Founder

Phone: +45 20417023

Mail: j...@innochiller.com

Web: www.jpclimatec.com

[H simmens]

Following up on Soumitra’s recent post it’s important to better understand the motivations of those who oppose direct climate cooling. 

There’s not a lot of research that’s been done unfortunately that attempts to answer that question in depth. 

One engaging 15 minute attempt to begin to do so was by Gareth Davies at the CCR Arctic Repair conference earlier this year that a number of those on this list attended. See the link below. 

Gareth points out some of the opposition - we don’t know how much but I suspect it’s considerable - comes from those who rather than being afraid it may fail are afraid it may succeed. 

Succeeding to some may be utterly incompatible with their world view that rebels against intervening with natural processes. Others particularly younger people understandably are fed up with the capitalist world that has permeated the globe and see successful cooling as a means to prop up an ideology and economic system that must be overthrown sooner rather than later. 

The involvement of Silicon Valley, venture capital and caucasian older men from the global north (the HPAC Steering Circle just added its eighth such person - out of nine - the ninth being a caucasian global north woman - earlier this year) is unlikely to assuage most opponents. 

Attempting to change the minds of those with such ideological perspectives is unlikely to be particularly successful. 

Without understanding what I suspect are complex and perhaps often overlapping ideological, economic and scientific reasons for opposing SRM those of us supportive may be aiming our advocacy in the wrong places and with the wrong messages. 

Herb

Herb Simmens
Author of A Climate Vocabulary of the Future

“A SciencePoem and an Inspiration.” Kim Stanley Robinson
@herbsimmens
HerbSimmens.com

Herb Simmens
Author of A Climate Vocabulary of the Future

“A SciencePoem and an Inspiration.” Kim Stanley Robinson
@herbsimmens
HerbSimmens.com

On Dec 27, 2025, at 10:58 AM, Dr. Soumitra Das <mr.soum...@gmail.com> wrote:



To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/CADWMfER3j2LKAeQc1g8uyvFc0HGOXvRBZHe_nBButec%2BMM4ruw%40mail.gmail.com.

[oswald....@hispeed.ch]

Hi Jesper

 

to judge your climate cooling proposal I would need info on what you want to achieve. Let us say you want to cool the global atmosphere by 0.1 °C.

 

• How much energy would this need?
• Is this a continuous effort?
• How much would it cost?

 

Another acceptable measure could be tonnes of CO2e…

 

Regards

 

Oswald Petersen

Author of „GeoRestoration – Cool the Climate with Natural Energy“

Atmospheric Methane Removal AG

Lärchenstr. 5

CH-8280 Kreuzlingen

Tel: +41-71-6887514

Mob: +49-177-2734245

https://amr.earth

https://georestoration.earth

https://cool-planet.earth

 

[Jesper Pedersen]

Hi Oswald

 

Thanks for your additional comments and questions.

Attached please find additional information for my climate cooling proposal.  

 

• How much energy would this need?

To counter act current global warming factor of 3,5 W/m2 which affect the entire surface area of the Earth (513 Mio. Km2) This results in an energy amount which accumulate on the planet to be approx. 1.785.350.000 MW and approx. 100 times higher energy than we consume (620 Exajoule/year).

I have calculated the coefficient of performance for this climate cooling proposal to be approx. 7.570
This means the required installation power to counteract global warming to will be 235.835 MW or approx. 1,2 % of current annual energy consumption of 620 Exajoule equal to 19.600.000 MW

I have calculated that the number of wind turbines which needs to have this evaporator unit mounted on top are approx.. 530.000 Units.  

This calculation, does not consider how the solution affect the biotic pump,

so therefore the real number of wind turbines with additional mist evaporation system, may be much less than estimated in this calculation.

The process also results in reduced altitude of cloud layer, which will improve the Earth’s heat rejection ability, this factor is not taken into account as well.

But this video explains that low altitude clouds has an overall cooling effect: www.youtube.com/watch?v=A9xAG601dG4&t=11s

The good thing with fog, is that the temperature inside the fog is lower than areas without fog, so this means fog don’t trap heat at night as clouds does.

 

Local climate can varies with several degrees in small areas whether it’s inside or outside the fog, at attached images, there is a temperature difference of 1,5 see the dashboard.

 

The heat engine power comparison between a dry surface where the sun shine and a wet surface where the sun shine are not considered as well.

• Is this a continuous effort?
  

• Since this climate cooling affect the biotic pump and reestablish small water cycles in dry areas, it does not necessarily means that this climate cooling solution needs to be in operation for many years ahead maybe only one or two generations of machinery (50 Years).   

 

• How much would it cost?
  

• Based on an machinery cost of 1.000.000 USD/MW, and required installation power 235.835 MW, I have calculated that the total investment cost to counteract global warming will be approx. 235.835.326.500 USD.
  With an expected lifetime for the wind turbine and evaporator unit to be 25 Years, the annual investment cost to maintain the cooling cycle will be approx. 9.433.413.000 USD  

 

Feel free everyone to respond.

Med venlig hilsen/ Best regards

Jesper Pedersen

CEO-Founder

JP ClimaTec

Phone: +45 20417023

Mail: j...@innochiller.com

Web: www.jpclimatec.com

 

[John Ure]

Forgive me for intruding as it were. I follow the debate, and recently was reading 'Engineering and Governing the Climate' by Xavier Landes. My reason for butting in is to announce the publication of my book Climate Change and Carbon Markets, published by Springer Nature. Also available from Amazon from 6th January 2026. The Springer link is at https://link.springer.com/book/9783032076182?utm_medium=catalog&utm_source=sn-bks&utm_campaign=search_tool&utm_content=my_flyer 

Although it does NOT address geo-engineering as such, I hope it does provide a pretty comprehensive review of the issues and problems to be solved.

Contents
Foreword
Chpt 1 - the science of climatology and IPCC scenarios
Chpt 2 - pathways towards the Paris Agreement goals, the IEA and IRENA
Chpt 3 - why neo-liberal economics is simply wrong and climate should be treated as an endogenous factor
Chpt 4 - Public policy towards climate change, including China, India, the EU, UK, USA and Singapore
Chpt 5 - The voluntary carbon market and the future role of Article 6 of the Paris Agreement
Chpt 6 - Green finance and why the UNFCCC model does not work
Chpt 7 - Conclusions, the key importance of MRV (monitoring, reporting and verification) and the need for an International Green Bank (IGB) with an exclusive focus upon the Global South and upon climate and environmental issues

Best wishes for 2026

Fyi: my website is Johnure.net and my Linkedin page with more stuff is 

My Linkedin link is at https://www.linkedin.com/in/john-ure-262655/recent-activity/all/ 

John Ure

To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/EAECBC1E-3867-478C-9D0F-7AF1D7FFA106%40bigpond.net.au.

[oswald....@hispeed.ch]

Hi Jesper,

 

once you say something like you need 530.000 wind turbines, the idea is dead.

We would need 60 (sixty) planes to cool the climate by 0.5 °C…

To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/AM9PR06MB8177540C7829EFC2DD14E161DCBFA%40AM9PR06MB8177.eurprd06.prod.outlook.com.

[Jesper Pedersen]

Hi Oswald

Thank you for your response.

Regarding the number of evaporator units I have calculated to be 530.000 with a required power output of 1,2 MW each.

Worldwide there are already approx. 500.000 Wind turbines, so I would only like to add the humidifier units for future wind turbines.

The power output from each wind turbine, dedicated to supply the humidifier system will only be approx.. 10 % of the total wind turbine power, so there will be plenty of power available to the consumers.

Lets say each humidifier unit including pipe and pumps, will add 15 tons in raw materials to each wind turbine, this means a total raw material needs will be: 15x530.000 = 7.950.000 tons mostly steel which is 100% recyclable.

 

There is another team from The Netherlands working on a similar project www.theglobalirrigationproject.com

www.youtube.com/watch?v=KtQuP8CTPl0

 

A Spanish team also focusing on using the cooling effect between actual temperature and wet bulb temperature to cool the planet, using katabatic cooling tower principle:  

www.oasis-tower.com  

 

Other side effects that will helps to take out CO2 from the atmosphere and thereby reduce the number of required wind turbines:

•Transform desert areas into fertile farmlands
•Turns sand areas into soil which act as carbon sink

Regarding the highly controversial SAI, and number of airplanes, David Keith mentions 100 airplanes in this podcast at 8:50 Minutes.

www.youtube.com/watch?v=jWHb0iEAxGY

I don't know what number of airplanes this is based on, but let us use Pinatubo SO2 amount in 1991 as an example, there was injected 20 Megatons of SO2 into the Stratosphere and cooled the atmosphere with 0,5 degrees over a period of 3 years.

According to AI some researchers  estimates that there annually will be needed  12.000.000 tons of SO2 to cool the planet with  

A Airbus 380 has a cargo capacity of 150 tons which gives number of flights/year of 12.000.000/150 = 80.000 flights/year or 219 flights/day so 219 airplanes would be needed as I see.  

One comments here, all this Stratospheric Injection method proposals as a cooling proposal are also highly questionable, since we annually already inject 125.000.000 tons of SO2 into the atmosphere (troposphere) from human sources, mostly coal burning and fossil fuel burning. Hereby adding an extra 12.000.000 million tons into the stratosphere which is the expected amount that is needed to achieve some cooling, what If that is not sufficient?

 

I have heard that Marine Cloud Brightening as a cooling solution for the Great Barrier Reef, didn’t have the expected cooling effect as expected, but cooling by fog have an impact and that is the solution which there are focusing on now.  

 

According to the World Counts the cost of not acting on climate change are approx. 18.498.039.097.900 USD so a estimated cost of 235.835.326.500 USD or 1,27 % to fix global warming is only a fraction of what is cost of not acting.  

Maybe the cost to fix global warming using this method will be much lower once all factors are included.  

www.theworldcounts.com/challenges/global-warming/cost-of-climate-change

 

Happy New Year from JP ClimaTec.