Invitation to co-sign an open letter supporting applied-science testing and piloting of near-term global climate cooling
Ron Baiman
Dear Colleagues,
We invite you to join us in signing this: Open Letter in Support of Applied-Science Testing and Piloting of Near-term Global Climate Cooling Approaches: (https://docs.google.com/document/d/1-ylFDVmw362TQmKxmmH1_NTlw7k-RHMS/edit?usp=sharing&ouid=116465941111195452408&rtpof=true&sd=true) in which we stress that if we're going to start "shaving the peak" in 2030-2050, as many global climate model geoengineering simulations assume, we need to start working on this now, or, at least, as soon as possible.
As many of you know we have been working on this letter for many months. During this time it has undergone numerous revisions in response to extensive feedback from numerous colleagues - some among the current signatories and some not. We believe at this point that further editing has reached a point of diminishing returns and that it is time to move forward on garnering further support in advance of (hopeful) publication.
We think that this letter could be an important component of the political effort to open the Overton Window that we and our near allies have expanded to include general support for geoengineering "research," but that continues to be firmly shut on the issue of "piloting." The following quote, for example, is from the September 2023 Executive Summary of the Climate Overshoot Commission ( https://www.overshootcommission.org/_files/ugd/0c3b70_bab3b3c1cd394745b387a594c9a68e2b.pdf):
"Countries should adopt a moratorium on the deployment of solar radiation modification and large-scale outdoor experiments that would carry risk of significant transboundary harm, while expanding research, and pursuing international governance dialogues."
We disagree with this formulation as it appears to fail to take into account the ever larger catastrophic climate events that will happen if cooling efforts are not initiated in the very near future. Both "large outdoor" applied-science testing and piloting of near-term global climate cooling approaches need to start now in order to be implemented in the 2030s at the latest.
Most of you are likely familiar with the general HPAC position in favor of urgent climate cooling being implemented as a complementary approach to more aggressive efforts to cut emissions of CO2 and CH4, increase resilience, and initiate efforts to build up Carbon Dioxide Removal.. We believe that our open letter sharpens our call for a credible comprehensive approach to controlling climate change and clarifies the practical implications of the need for adding urgent near-term global cooling to the active set of policy options.
With the global temperature increase poised to speed past the aspirational goal of the Paris Accord, we are asking for your signature in support of countering voices that see efforts to augment and complement emissions reduction with carefully research cooling influences as more risky than continuing toward projected global warming of 2 to even 3°C or more of global warming, as argued, for example, in Siegert et al. (2025), who asserted that
"… further research into these [geoengineering] techniques would not be an effective use of limited time and resources.” [brackets ours].
Finally, this letter is part of a parallel effort by HPAC’s Steering Circle to transmit a position paper with a similar message to IPCC delegations in advance of COP-31, for which, needless to say, broad support for this letter would be helpful.
We encourage you to consider co-signing this letter if you agree with the need to augment COP’s mitigation-focused approach that, while essential to reduce peak warming, is proving insufficient to meet the goals of the Paris Accord, much less pull the world back from likely exceeding an increasing number of irreversible tipping points.
To indicate your concurrence, please send a note to Ron Baiman at rpba...@gmail.com (also copying Michael MacCracken at mmac...@comcast.com). Please include your name as you would like it to appear and your affiliation(s), including other affiliations than just HPAC.
Thank you,
Best,
Ron and Mike
For the Co-Signers
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Ron Baiman
Mike Williamson
Sent: Monday, February 16, 2026 3:14 PM
To: healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>
Cc: Michael MacCracken <mmac...@comcast.net>
Subject: [HPAC] Re: Invitation to co-sign an open letter supporting applied-science testing and piloting of near-term global climate cooling
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Ron Baiman
Oeste
Hi Ron
I would also like to sign. Hope not to be too late.
Franz
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Kevin Lister
Sent: Tuesday, February 17, 2026 12:17 AM
To: Ron Baiman <rpba...@gmail.com>; healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>
Cc: Michael MacCracken <mmac...@comcast.net>
Subject: Re: [HPAC] Re: Invitation to co-sign an open letter supporting applied-science testing and piloting of near-term global climate cooling
Ron Baiman
Dear Colleagues,Thank you again to all who have signed!We now have 30 signatures and just need 12 more to achieve our goal of 42 (see p. 7): https://docs.google.com/document/d/1-ylFDVmw362TQmKxmmH1_NTlw7k-RHMS/edit?usp=sharing&ouid=116465941111195452408&rtpof=true&sd=truePlease consider signing if you haven't yet! The sooner we get to our goal the sooner this will be submitted and (hopefully) published.Best,Ron and Mike
Ron Baiman
Dear Colleagues,Thank you again to all who have signed!
We now have 31 signatures and just need 11 more to achieve our goal of 42 (see p. 7): https://docs.google.com/document/d/1-ylFDVmw362TQmKxmmH1_NTlw7k-RHMS/edit?usp=sharing&ouid=116465941111195452408&rtpof=true&sd=true
Please consider signing if you haven't yet! The sooner we get to our goal the sooner this will be submitted and (hopefully) published.
Also, if you're so inclined, if you could share with colleagues whom you think might be interested this would be most appreciated as we're trying to get to our 42 signature goal asap!
Thank you.
oswald....@hispeed.ch
Hi Ron, Mike,
pls add me to the list of signees,
Regards
Oswald Petersen
Author of „GeoRestoration – Cool the Climate with Natural Technology“
Atmospheric Methane Removal AG
Lärchenstr. 5
CH-8280 Kreuzlingen
Tel: +41-71-6887514
Mob: +49-177-2734245
Von: healthy-planet-...@googlegroups.com <healthy-planet-...@googlegroups.com> Im Auftrag von Ron Baiman
Gesendet: Freitag, 20. Februar 2026 20:24
An: healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>
Cc: Michael MacCracken <mmac...@comcast.net>
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Dave King
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Jim Elsworth
Hi Ron, I am happy to have my name on the list if it is valid. I am not a climate scientist, just a very concerned global citizen and on the mailing list of HPAC. I have written to a number of organizations that proport to be concerned about the climate, to advocate having global cooling (specifically MCB) as an item on the table to be debated. They either ignore me or their automated reply says, de facto, that they are too busy to talk to me. If I need an organization, I regard myself as a member of HPAC, or you could say “Twende”.
Regards
James Elsworth.
To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/DF61B8B4-8B08-4069-8157-86DA2A9AE01F%40camkas.co.uk.
Ron Baiman
Dear Colleagues,Thank you again to all who have signed!
We now have 39 signatures and just need 3 more to achieve our goal of 42 (see p. 7-8): https://docs.google.com/document/d/1-ylFDVmw362TQmKxmmH1_NTlw7k-RHMS/edit?usp=sharing&ouid=116465941111195452408&rtpof=true&sd=true
Please consider signing if you haven't yet! The sooner we get to our goal the sooner this will be submitted and (hopefully) published.
Also, if you're so inclined, if you could share with colleagues whom you think might be interested this would be most appreciated as we're trying to get to our 42 signature goal asap!
Thank you.
Best,Ron and Mike
Ron Baiman
Veli Albert Kallio
To: healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>
Cc: Michael MacCracken <mmac...@comcast.net>
Subject: [HPAC] Re: Invitation to co-sign an open letter supporting applied-science testing and piloting of near-term global climate cooling
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Veli Albert Kallio
Sent: 16 February 2026 23:14
To: healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>
Cc: Michael MacCracken <mmac...@comcast.net>
Veli Albert Kallio
Sent: 27 February 2026 02:51
To: Ron Baiman <rpba...@gmail.com>; healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>
Cc: Michael MacCracken <mmac...@comcast.net>
Subject: Re: [HPAC] Re: Invitation to co-sign an open letter supporting applied-science testing and piloting of near-term global climate cooling
Ron Baiman
Ron Baiman
Ron Baiman
Oeste
Our dry scrubbing and cloud brightening method paper will not be in a
publishable condition soon because it shall also contain the results of
lab research. Hence I will draw back my signation of the open letter.
According to the unsolved termination shock problem the SAI method to my
opinion is too dangerous. The largest extinction catastrophes within the
habitable zones of the Earth probably had their origin in LIP*) events
as the long lasting Siberian Trap Event that darkened sunlight,
increased the greenhouse gas content of the atmosphere and cooled the
surface for many years and destroyed the atmospheres oxidation capacity
by a stratospheric soot, smoke and sulfuric acid haze layer and also
destroyed plant life on the continents and in the sea by this darkness
and probably freezing temperatures on the continents. The catastrophe of
the termination shock followed when darkness ended and the heaven became
blue again: average temperatures did a jump of ~10 °C above average
Temperatures before the volcanic event according to the high levels of
greenhouse gases. This ended in burning down the frozen and dry
vegetation, soil transport into the ocean by land slides, deglaciation
and erosion.
Probably a SAI termination shock will not end in such severe catastrophe
but also bad enough to induce bad influences on global agricuture and
may end in famine-induced deaths.
Hence to propose the SAI method as the best researched main means to
fight the climate warming is a big mistake. Thus, we hope you can wait
with publishing the open letter until we have implanted also the lab
trial results into our dry scrubbing and cloud brightening method paper
and have it in a preprint condition as an alternative to SAI and you can
introduce an abstract about it as an equivalent information about our
method in the open letter you will get also my signification to the open
letter.
Franz
Sander Epema
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Brian von Herzen
I agree. I have already started to soften the language a bit with several suggestions, but we could go further by listing SAI as one of several cooling approaches that must be investigated thoroughly.
Regards,
Brian
Brian von Herzen, Ph.D.
Executive Director, Climate Foundation
http://www.climatefoundation.org/
NASA modeling has determined that carbon levels above 350 ppm are incompatible with sustaining a planet similar to that on which civilization has developed and to which life on Earth is adapted (James Hansen). In April, 2023, the Keeling curve exceeded 422 ppm for the first time in recorded history.
Ron Baiman
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Ron Baiman
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Ron Baiman
Ron Baiman
Oeste
Hi Mike
Your hypothesis about the antipodal asteroid impacts as causes of large igneous province (LIP) volcanic events has been described by Hagstrum (2005). If this hypothesis is right, every LIP event should be accompanied by an impact crater structure with an adjacent strewn field of tektites. Tektites are gravel-sized glass bodies formed from molten terrestrial debris ejected by the meteorite impact. The larger the LIP the larger should also be the meteoritic impactor and the larger should also be the tectites strewn field and the crater diameter.
The End-Permian Siberian Traps event happened ~250 million years ago. Since than continents of our dynamic planet moved or devided, shore lines changed and seafloor sediments disappeared by subduction. Thus, according to our fairly exact knowledge of the continent constellation movement since then the antipode region locality corresponding to the siberian trapps projection on the ancient globe and present position of crater and strewn field remnants should be possible. If the antipodal hypothesis is right this antipodal region to the Siberian Traps region should contain a huge crater signature plus tectite strewn field. Until today these signs have not been localized. This makes it difficult for me to believe in the antipodal hypothesis.
You mention a SAI termination shock heating of 1 to 1.5 °C: contains this calculation result also the consideration of increased atmospheric life times / concentrations of the climate gases and climate gas precursors of methane, carbon monoxide and tropospheric ozone during SAI campain? Did you consider also the reduced Earth albedo from the decreased cumulus- and strato kumulus cloud coverduring SAI campain?
Greetings,Franz
Dear Franz--Fine to pull your name off, but the explanation seems way overstated.
We all agree that what we want is enough mitigation and CDR so the SRM is not necessary. Technologically, we know how to do much of the mitigation (including methane reduction to extent it can be done) --we just have to do it. I'm of the view (perhaps wishful thinking) that this, coupled with the build up of CDR will hopefully keep the peak warming were intervention not used to 2.5 to 3 C, so the termination shock increase will hopefully be at most 1 to 1.5 C. If this is not the case, that is if global warming goes up above 3 C, we're going to be cooked. And as other techniques become available, they can be substituted in if merited--we're not proposing a fixed plan to continue for many decades. It is the intervention that we think needed.
And on the Siberian trap volcanism, major eruptions happen at major faults due to continental drift, etc., Siberian traps and prolonged extensive vulcanism is rather strange. I have a hypothesis that needs exploration and that is it was driven by a major asteroid impact. So, when this happens, seismic waves spread out around the Earth, and they converge at the antipode, and there they would likely sort of tear apart the continental plate and lead to the type of eruptions that you are talking about. I just don't think that is at all a good analog for termination shock of 1 C or so.
And I'll be happy to have methane reduction if that can be done first (I hope you can come to out briefing next Thursday to hear about the research program Spark Climate is doing) and other approaches contributing (getting them to be globally effective I fear will take too long).
Best, Mike
Michael MacCracken
Hi Franz--The impact location that was the antipode of the Siberian traps was right about where the southern Atlantic Ocean started to form, perhaps beginning the splitting of South America from Africa., and then extending up through the North Atlantic and even continuing today. I would also note that impacts in the oceans are not going to show in the same way.
On the issue of changing cloud amounts, there are some limits. Convective clouds form where air is moving up, and in that the same amount of air goes up as comes down, we won't be going to zero convective clouds. And marine stratus clouds form where air is generally coming down and creating a low-altitude inversion. The stratus clouds tend to have a greater effect on planetary albedo and seem to be going down as the surface is warming. Increased water vapor in atmosphere would be expected to be powering increased upward movement. I don't see how we are going to go too far in cloud reduction. Just some reflections, making me think that, along with the relatively low cost of intervention compared to mitigation and accelerating impacts, that the threat of termination shock will be relatively low, and the impacts of going forward without intervention will be much more likely and serious than going forward with intervention.
Best, Mike
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