From Climate Tools to Human Protection: Rethinking Climate Intervention in a Warming World

[Dr. Soumitra Das]

I began to realize that, in debates around SAI, MCB, or CDR, we often lose sight of the primary objective: protecting people from the escalating impacts of climate change.

The central question is not whether SAI or MCB is “right.” It is not mitigation versus adaptation, or CDR versus SRM. We will need all of these tools—and likely different combinations of them—to protect people across regions and over time.

Many of the hardest questions extend beyond science alone. Economics, social acceptance, political feasibility, and governance will ultimately determine what can be deployed—and when. The real challenge is this: how do we protect people in the short and long term while accounting for all these realities?

Even under optimistic assumptions, it will take at least 15–20 years to resolve the scientific, governance, and global coordination questions surrounding potential SAI deployment. During that period, the human costs will continue to mount. Hundreds of millions—potentially far more—will be displaced from their homes. Food and water insecurity will worsen. Heatwaves will claim countless lives. Entire regions may become increasingly difficult—or impossible—to inhabit.

This makes the question unavoidable: what should governments and societies do now? What solutions and policy frameworks should be advanced in the interim? How should governments respond if we tell them that some tools may only be available decades from now? These are the questions that keep me awake.

It is neither realistic nor responsible to ask policymakers to focus narrowly on SAI alone when its potential deployment may still be 15–20 years away. We must offer a coherent package of near-term and long-term solutions—practical, ethical, and politically viable pathways that reduce suffering today while preparing for more ambitious interventions tomorrow.

Over the past decade, an estimated 250 million people—primarily in the Global South—have already been displaced by climate-related impacts. This number is projected to accelerate dramatically, potentially reaching two billion people within the next 20 years. This is not a distant or abstract risk; it is a present and rapidly unfolding humanitarian crisis.

This is why I believe we need a fundamentally different approach—one that is pragmatic, people-centered, and time-aware. I would very much welcome your thoughts on how we should navigate this challenge.

This is precisely what the Climate Intervention Summit is about.

Thank you,

Soumitra

--

Soumitra Das

Chairman and Executive Director, HCI USA

Chairman, HCI India

https://healthyclimateinitiative.org/

[br...@chesdata.com]

“[P]rotect[ing] people in the short and long term while accounting for all these realities” can be done with adaptation strategies.  In the long run SRM will likely be needed.  Since SRM might take decades to implement we first need to convince politicians that SRM research is needed. To do that

1. We need a “detailed” description of the impacts of a temperature increases in 2050 of 1.5℃, 2.0℃, and 2.5℃  (ecosystems collapse, AMOC, sea level rise, carbon feedbacks, Amazon, Arctic sea ice, albedo, etc.)
2. We then need to “reach an agreement” on the maximum “acceptable” temperature increase in 2050
3. We also need to agree on realistic GHG emissions pathways for 2025 through 2050 that includes albedo changes, reductions in land/ocean sinks, feedbacks, etc.
4. If realistic GHG emissions pathways project a temperature increase greater than the maximum “acceptable” temperature increase in 2050 then hopefully politicians can be convinced that SRM research is needed.

 

Bruce Parker

 

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[Douglas Grandt]

Apologies, 

I neglected to include copyholders of the other mentioned concurrent threads …

Doug Grandt 

Begin forwarded message:

From: Douglas Grandt <answer...@mac.com>
Date: December 14, 2025 at 8:58 PM EST
To: robert...@gmail.com, "Dr. Soumitra Das" <soumi...@healthyclimateinitiative.org>, John Nissen <johnnis...@gmail.com>, Herb Simmens <hsim...@gmail.com>
Cc: planetary-...@googlegroups.com
Subject: Re: [prag] From Climate Tools to Human Protection: Rethinking Climate Intervention in a Warming World



Robert, Soumitra, John, Herb et al,

Pondering the two concurrent threads, and merging all the thought expressed, I imagine an “all hands on deck” friendly competitive challenge among the advocates of every plausible means of “protecting people from the escalating impacts of climate change,” as concisely summarized below.

Visually, a horse race or the space race are examples of all-out efforts to win a prize or achieve a priceless goal. 

Not every horse gets the big money, but the best of the best all get something. UK has Grand National, Epsom Derby, Royal Ascot, Cheltenham Gold Cup, etc. and the U.S. has Kentucky Derby, Preakness Stakes, Belmont Stakes, Breeders’ Cup Classic, etc.

J.F. Kennedy aimed for the moon, and set into motion a complex and improbable challenge, which is an example of long-term planning and short term milestones.

What I envision is the all-out effort of a horse race and the complex planning and step-wise deployment that led to the moon landing. Designing and building an AirBus, Boeing 787, NASA Shuttle & I.S.S., SpaceX, new aircraft carrier or nuclear submarine is no less complex, and is done routinely.

P.E.R.T. (Project Evaluation and Review Technique) and Gantt Charts were created to manage seemingly unmanageable projects. The most plausible of the 61 more or less measures so far identified can easily be set up to plan and manage progress independently as well as inter-dependently. No more or less feasible than what NASA and many others have demonstrated.

JFK had the starting gun and funding, then NASA created the plan. Our situation is revered: we must create the plan in order to pitch it to those with the starting gun and funding. An added bonus for us is, stages of governance must be identified in the P.E.R.T. & Gantt charts with milestones for fleshing out and gaining consensus—obviously, there is no time to complete that effort in advance of beginning research & development.

I believe priority number one is to develop a plan that is credible and convincing. Without acknowledging so-called known unknowns and providing for dealing with unknown unknowns, no self-respecting decision maker, billionaire or peer scientist or engineer will give us the time of day.

As a reminder, here’s the timeline between JFK’s speech and the moon landing:

JFK’s Speech: May 25, 1961 - President Kennedy announced to Congress the goal of landing a man on the Moon before the decade’s end.

Project Gemini: The program operated from 1965-1966, with 10 crewed flights launched during this period  . Specifically:

• The first crewed Gemini flight (Gemini III) launched on March 23, 1965 

• The final mission (Gemini XII) launched on November 11, 1966 

Apollo Program: The Apollo program was in development throughout this period:

• Apollo 1 astronauts were killed in a test on January 27, 1967 

• Apollo 10 served as the rehearsal for the moon landing 

• Apollo 11 achieved the moon landing on July 20, 1969 

So in summary: Between JFK’s May 1961 speech and the July 1969 moon landing, Project Gemini operated for about 20 months (March 1965 - November 1966), serving as the crucial intermediate step between Mercury and Apollo. The Apollo program was being developed concurrently and began crewed missions after Gemini concluded, culminating in the successful moon landing.

Source: Claude

Best regards,

Doug Grandt 

Sent from my iPhone (audio texting)

On Dec 14, 2025, at 5:59 PM, robert...@gmail.com wrote:



Hi Soumitra

I have some issues with what you've written below.  No problem with the underlying sentiment or the passion, but I think the framing is a problem.

We should not be talking about 'solutions'.  There is no solution to global warming.  It's a classic wicked problem in Rittel and Webber's terms.  As each intervention attempts to 'solve' it, it will morph into a different problem requiring a different 'solution'.  There's no end point when you can say it's solved.

Climate change and global warming are situations that need to managed, not solved.  While for scientists, the science is all about getting to the 'truth', an in depth understanding of the physical dynamics of the climate system, and how it will respond to this that or the other stimulus, for policymakers it should be about managing risk.  Nothing that will happen in the future can be known with absolute certainty.  Policymakers must weigh the odds that any intervention, including no intervention, will reduce the risk of undesirable outcomes.  Moreover, as the future unfolds, they must continually reassess the situation to decide whether yesterday's policies might be improved in the light of experience, to further reduce the risk of undesirable outcomes, perhaps even undesirable outcomes that hadn't been identified previously.

Frame climate policymaking as a continuous risk management enterprise not as a scientific and engineering problem solving task.

Another reason this is important is that unless people focus on the risks, they won't understand why they need the policies.  We don't buy home insurance because we have a sprinkler system in our house (if you do!) or a fire station round the corner, we buy the insurance because the sprinkler system and the fire fighters will only limit the damage not prevent it.  We buy the insurance because we understand that if our house went up in flames it'd be big deal, even if it wasn't the absolute worst possible fire one could imagine..  We buy the insurance to limit our exposure to a risk that we have thought about and decided that we want to mitigate.

If the focus is on the solutions, the reaction from many will be to ask why they should pay for them.  Isn't that just a solution looking for a problem?  Most people just don't understand how precarious our situation is and how utterly ineffective most government policy responses to it are.  Ignorance really is bliss, until it isn't.

Regards

Robert

On 14/12/2025 21:56, Dr. Soumitra Das wrote:

I began to realize that, in debates around SAI, MCB, or CDR, we often lose sight of the primary objective: protecting people from the escalating impacts of climate change.

The central question is not whether SAI or MCB is “right.” It is not mitigation versus adaptation, or CDR versus SRM. We will need all of these tools—and likely different combinations of them—to protect people across regions and over time.

Many of the hardest questions extend beyond science alone. Economics, social acceptance, political feasibility, and governance will ultimately determine what can be deployed—and when. The real challenge is this: how do we protect people in the short and long term while accounting for all these realities?

Even under optimistic assumptions, it will take at least 15–20 years to resolve the scientific, governance, and global coordination questions surrounding potential SAI deployment. During that period, the human costs will continue to mount. Hundreds of millions—potentially far more—will be displaced from their homes. Food and water insecurity will worsen. Heatwaves will claim countless lives. Entire regions may become increasingly difficult—or impossible—to inhabit.

This makes the question unavoidable: what should governments and societies do now? What solutions and policy frameworks should be advanced in the interim? How should governments respond if we tell them that some tools may only be available decades from now? These are the questions that keep me awake.

It is neither realistic nor responsible to ask policymakers to focus narrowly on SAI alone when its potential deployment may still be 15–20 years away. We must offer a coherent package of near-term and long-term solutions—practical, ethical, and politically viable pathways that reduce suffering today while preparing for more ambitious interventions tomorrow.

Over the past decade, an estimated 250 million people—primarily in the Global South—have already been displaced by climate-related impacts. This number is projected to accelerate dramatically, potentially reaching two billion people within the next 20 years. This is not a distant or abstract risk; it is a present and rapidly unfolding humanitarian crisis.

This is why I believe we need a fundamentally different approach—one that is pragmatic, people-centered, and time-aware. I would very much welcome your thoughts on how we should navigate this challenge.

This is precisely what the Climate Intervention Summit is about.

Thank you,

Soumitra

--

Soumitra Das

Chairman and Executive Director, HCI USA

Chairman, HCI India

https://healthyclimateinitiative.org/

<HCI Logo_reszied.jpeg>

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[Michael MacCracken]

Hi Bruce--I am not sure why you put SRM off when it is the only way to really limit climate change in the near term. The world reached an agreement on maximum temperature change--and it was already higher than it should have been--and it has not lived up to it. What makes you think that this next time will be any different? And how would agreement possibly be reached when it is different for basically everywhere.

And there is an adage sometimes attributed to Yogi Berra but I think really from Neils Bohr--"Prediction is very hard, particularly of the future." What makes you think there could be agreement on a "detailed" description" of your list of items when there are likely tipping points and also changes that have been underestimated and understated in the past?

A colleague I have in the business community points out how it is the scientific community that has trapped the world in seeking high confidence (so there can never be a crack in the building blocks of the pyramid of knowledge). What is taught in business school is to plan to be resilient to low probability/high consequence ("worst plausible") risks--so make sure to be safe from what is inherently uncertain and even unlikely, but conceivable.

There is then also the intergenerational question--there are changes that may not hit while we are alive but where we have made a commitment that could overwhelm future generations, an example being commitment to a rate of sea level rise of, say, a couple of meters per century. Discount rates seem a quite implausible approach when one be heading toward loss of mass from ice sheets, Amazon biodiversity and carbon sink, etc.

Actually, in my view, it is well past time that SRM research should have been well underway.

Best, Mike

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[H simmens]

Bruce,

I agree with much of what Mike has just said. 

However I think you identified something very critical that I have been mystified about for years now. 

And that is the Urgent need to begin to answer the “At what point” question. 

While Paris did answer the question of what temperature we should aim to stay under no one with influence is discussing the question of what current or projected temperature and other impacts should trigger the safe and effective deployment of cooling. 

Of course answering this question requires recognizing the timeline between agreeing to deploy and actual deployment.  Wayne Gretzky is supposed to have said:

“I skate to where the puck is going to be not where it has been.”

I find it astonishing that attempts to provide a framework for answering this existentially critical question are all but nonexistent. 

(I did come across a paper some years back that made an initial attempt but unfortunately I can’t find the paper now. Does anyone know what I’m referring to?)

I think it represents a huge Inexplicable Blindspot on the part of climate leaders activists and climate researchers particularly those in the SRM and tipping points communities. 

I raised this question at the Arctic Repair conference in Cambridge this past summer. The speaker was talking about the fact that Ocean Visions supports SRM research but not deployment. 

I asked her and everyone in the auditorium at what point would her organization or anyone else sitting there (which included many of the leading SRM researchers from around the world) support the deployment of SRM. Predictably the speaker completely avoided answering my question nor did anyone else respond either publicly or privately to me. 

It’s hard for me to imagine a more important discussion yet no one literally no one in authority or at the major NGO’s seems to be interested in beginning to answer it in a organized rigorous and inclusionary manner. 

Herb

5, at 11:01 AM, 'Michael MacCracken' via Healthy Planet Action Coalition (HPAC) <healthy-planet-...@googlegroups.com> wrote:



 

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[Alan Kerstein]

Herb,

To me this is like a fire department receiving a fire alarm and thereupon debating how bad the fire needs to be before they go put it out.

Alan

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[Herb]

Alan,

But the world doesn’t have a fire department with clear unambiguous authority and resources to avoid and extinguish fires. 

Nor is there agreement that there is even the equivalent of water - a safe and effective means to put out fires. 

Nor is there yet agreement that the fire can’t be put out by other means. 

Herb 

Herb Simmens
Author of A Climate Vocabulary of the Future

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

On Dec 15, 2025, at 11:56 AM, Alan Kerstein <alan.k...@gmail.com> wrote:



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[Michael MacCracken]

Hi Alan and Herb--Or as is sometimes said--the horse is already out of the Barn. It seems to me that they may not want to be saying that research on SRM should have started long ago as a complement to the other approaches.

I'd also say, and doing so as a scientist in offering this view, that the scientific community got it wrong from the start, in part prodded by the fossil fuel companies, in essentially advocating for the traditional scientific decision framework of wanting high confidence before any finding is agreed to rather than understanding that, in my non-expert view, major (existential) policy decisions have a history of being better when a precautionary or risk avoidance decision framing is used. We put in huge investments in national defense in the hopes of avoiding the risk of war. Accepting that governments would just accept the scientific findings and promptly change over the established global energy system, and making this presumption seemingly with high confidence--or at least so high that it was viewed as essentially immoral to even talk about SRM--I think will be seen as a serious lapse in judgment that, it is turning out, is not something that many in the field are yet willing to accept.

Mike

[Alan Kerstein]

Herb,

Neither my analogy nor any other analogy is perfect. Since we are critical of people who reject active cooling while proposing alternatives that are no more than magical thinking, let's be careful about magical thinking about a globally legitimated body that will juggle the multitude of intractable uncertainties so deftly as to reach a widely accepted consensus on active cooling so expeditiously as to catalyze the needed actions with the needed alacrity. My gut estimate is that 95% of people who have strong opinions on climate change engage in magical thinking on some aspect of the issue. I'm not optimistic about the possibility of a process for selecting people to be in charge of geoengineering that will produce a team dominated by people drawn from the other 5%.

Alan

[Herb]

Alan,

I’m not optimistic either but it’s really irrelevant whether any of us are optimistic or pessimistic. 

I think groups like ours have to be advocating for rational processes and institutions to be created or designated to address these existential challenges. 

As Robert Tulip has pointed out there are examples of international institutions that have been created or tasked to support, regulate and monitor various international functions and are often reasonably successful in achieving their missions. 

I wonder how many people even sophisticated leaders and decision makers 60 years ago thought that the world would get to at least the first quarter of the 21st century without another nuclear configuration. 

So it can be done however daunting the challenge. 

Why else are we in existence but to use our still minuscule influence to help navigate between no cooling deployment in the coning decades and ineffective - or worse - deployment. 

Herb

Herb Simmens
Author of A Climate Vocabulary of the Future

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

[Alan Kerstein]

I think there is a legitimate difference of viewpoints here Herd. Just as we wisely remain agnostic about the choice among cooling technologies, I think we should be agnostic about governance procedures. Both of these no-go principles potentially broaden the tent under which we gather the cooling advocates. Also, this sharpens the focus on the key challenge of gaining consensus that cooling is essential as a matter of principle and urgent in the face of vanishing acceptable alternatives.

Alan

[robert...@gmail.com]

Alan             

It's nothing like the fire department at all.  Firefighters are paid to do one thing - put out fires and rescue people.  They are totally focussed on that one objective.

Who, in a position to actually make things happen, is totally focussed on sorting out global warming?

Let me take this opportunity to open a discussion on what I think might be a useful metric in this regard - ^oCyears of overshoot.  The metric is a measure of the area under the temperature curve and above the 'acceptable' temperature rise threshold.  For example, if we decide that warming should be no more than 1^oC above PI, and it's above this level for 100 years with an average overshoot of 1.5^oC, then the overshoot value is 150^oCyears.

This metric requires a discussion about where the 'acceptable' threshold should, noting that this is a global threshold, so it has to be a one size fits all answer.  Second, it requires a discussion about how many ^oCyears is an acceptable cumulative total overshoot.  Overshooting by 3^oC for 10 years is probably more acceptable than overshooting by 1^oC for 200 years.  But maybe not.

To put this in perspective, if we use the Paris threshold of 1.5^oC, the overshoot to date has been 0.1^oCyears.  With a threshold of 1^oC, it is 3.2^oCyears.  By contrast, SSP245 delivers 100 and 104^oCyears, respectively to 2100. 

The question we should be considering for any given threshold, is how many ^oCyears of overshoot would be an acceptable policy maximum.  Sea level rise, wildfires, hurricanes and other severe weather incidents from floods to droughts, all of these will be exacerbated by persistent high temperatures.  And again, this is a global metric, so it has to be a one size fits all answer.

How do we decide where the line should be drawn?  How could we devise effective policies in the absence of such a line?

Hitherto, overshoot has been spoken of mostly in relation to the maximum height of the temperature curve above the threshold.  But time is also of the essence.

Is there something here worth developing?

Regards

RobertC

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[Tom Goreau]

Overshooting by 3^oC for 10 years is probably more acceptable than overshooting by 1^oC for 200 years.  But maybe not.

 

Maybe not, heat shock mortality increases exponentially with temperature.

 

 

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[Alan Kerstein]

Robert,

To clarify, I took Herb's reasoning as postulating a fire department and then proposing how it should operate, and I responded on that basis.

Alan

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[Herb]

Alan,

Just as Ron made an important contribution by listing and briefly describing a variety of well-known and not so well-known cooling techniques in the Urgent Cooling paper written by Ron and colleagues (including me ) so too do I think we can add value by summarizing and proposing new approaches to governance for evaluation by world leaders and the climate cognoscenti. 

For example I have suggested the creation of a blue ribbon type Brundtland Commission to evaluate where we are and what is urgently needed (this would be  a much more effective and influential version of the Climate Overshoot that was established a couple of years ago.) 

The governance challenge is in my view and that I think many other observers the most difficult and real obstacle to progress on cooling. 

Yet perhaps because of the make up of our groups the issue has received little attention  in the past four years and not one report or paper of any significance has come out of HPAC or Planetary restoration as far as I can tell. 

It’s not too late to remedy that. The report probably should not recommend a preferred alternative so it can remain agnostic as you recommend. It could advance the discussion by simply making the case why our current institutional structure is not fit for purpose and what some promising alternatives could be and how they might be able to be advanced. 

Herb 

Herb Simmens
Author of A Climate Vocabulary of the Future

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

On Dec 15, 2025, at 1:37 PM, Alan Kerstein <alan.k...@gmail.com> wrote:



[Alan Kerstein]

Herb,

I agree with the substance of your response although I think there is a tradeoff between focus and broadening the aperture to add value. The tradeoff is audience dependent, so there should be tailored messages addressing individual groups.

What led me to trigger this kerfuffle was your proposal that your "At what point?" rhetorical device should be addressed in an "organized rigorous and inclusionary manner." The fact that people deflect from this question reflects its rhetorical efficacy. However, asking for a point criterion for any climate policy transition is a gotcha question in view of the inevitable huge uncertainties involved, which are likely to throw sand in the gears of a group tasked with reaching a policy consensus. There are certainly good opportunities to pose the question, but tasking a committee to answer it is not one of them.

Alan

[Michael MacCracken]

To Robert and Herb, particularly--

On the proposed metric, perhaps what you suggest is a start, but it involves the most innocuous metric for impacts that one could possibly imagine--it averages land and ocean, it averages over a decade or so and so won't catch anything much of extreme events of temperature much less of precipitation, it is of only thermal temperature and does not include a measure of the increasing wet bulb temperature that is probably the key metric for the 75% of the global population that is most vulnerable as they don't have air-conditioning and work mostly outdoors.

I think this also relates to Herb's comment about governance--as poor decision-making as it was, the world community agreed in Paris that 2 C, but preferably 1.5 C were as high as they wanted to have things go considering tipping point risk and more. Just because they have not met this standard (which will condemn many low lying areas and islands to inundation, and most ecosystems to severe disruption--remembering that changes on most land areas tend to be about twice the increase in the global average temperature increase) is no reason to go back and say now how much more are you willing to take. We have a globally agreed value. And as to governance, on the key question of what the temperature level should be set, does anyone want it over 1.5 C, and probably no country wants it back below 0.5 C, so we have a pretty narrow range and our switch is not very precise given variability, volcanic eruptions, etc., so really the main question for now is who is going to step forward and keep it in this range. Sufficient mitigation is not really an option--the more that can be done the better and SRM can be phased down as mitigation succeeds--and we have to start with approaches that are currently viable and then work to generate better or supplementary approaches as we need to. I'd be interested to hear about the other really substantive issues as I think this governance issue has been rather overstated given how the present governance system is failing to get emissions on a strong downward track. I think the the key is getting started and learning and adjusting as time goes on.

And finally, since Robert C released his letter to the Guardian about the reluctance and opposition of the African leaders, here is mine (I held back in case they might want to use mine as they say they want a letter's use to be exclusive--having heard nothing, here are my thoughts:

To the Editor:

With intensifying and health-threatening heat waves in developing nations; with a low prevalence of air-conditioning; with a large fraction of outdoor jobs in agriculture, construction, and transportation; and with the viability of the Sustainable Development Goals ebbing as climate change continues, leaders of African and other low-latitude nations would better be working together to take charge of solar geoengineering (SE) efforts than ruling SE out. Global CO₂ emissions from fossil fuel combustion are at their highest level and, for many reasons, it will inevitably take decades to get to zero—just count up the number of cars, trucks, buses, trains, planes, ships, factories, homes, offices, power plants and more that must be changed. In addition, deforestation occurring mainly in low-latitude nations also needs to be stopped.

All this while, the adverse effects of global warming will keep increasing: heat waves will become hotter and longer; droughts will become more intense; many rainstorms will become be flood-inducing; the likelihood of tropical cyclones becoming more intense will increase; the Greenland and Antarctic ice sheets will become less stable, calving more ice into the oceans and increasing sea level rise. Yes, SE will alter the weather, but generally back toward cooler and more tolerable conditions. Unlike the model simulations that show continuing emissions without SE leading to much more disruptive impacts and likely exceedance of irreversible tipping points, model simulations with SE show reduced warming and disruption. The choice is not SE or not, but between much more disruptive impacts versus moderated, peak-shaving climate change with SE.

The developed nations have widespread air-conditioning and mainly indoor jobs, making them less vulnerable than developing nations. Their technical capabilities may be needed to undertake SE, but it is the developing nations that have a survival-driven interest and so should lead in SE’s governance and deployment.

Michael MacCracken, Ph.D.

Best, Mike

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[robert...@gmail.com]

Here are the letters the Guardian did publish, including one from Hugh Hunt.

Regards

RobertC

[John Nissen]

Hi Soumitra,

I think Mike's letter to the Guardian, good as it is, understates the dangers from tipping point catastrophe in the Arctic.  The Arctic tipping points are close to a point of no return when no amount of cooling intervention can prevent a slide towards absolute catastrophe for 2 billion people or more, and misery for the rest of us.

You write:

"It is neither realistic nor responsible to ask policymakers to focus narrowly on SAI alone when its potential deployment may still be 15–20 years away. We must offer a coherent package of near-term and long-term solutions—practical, ethical, and politically viable pathways that reduce suffering today while preparing for more ambitious interventions tomorrow."

We cannot afford to wait 15-20 years for deployment.  We need to start ramping up SAI deployment on a time-scale similar to the moon-landing as described vividly by Doug Grandt, earlier in this thread.

Cheers, John

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[H simmens]

Mike,

Not sure I understand what you’re saying regarding choice of a metric. 

I certainly am not suggesting or advocating a particular temperature should be the trigger for the use of SRM. 

I would put it this way. 

The overwhelming consensus of climate leaders whether they be scientists activists or decision makers is that  temperatures will increase to well beyond 2° C in the coming decades. And that the impacts will be extreme even catastrophic and potentially existential. And that there is little prospect that the world will dramatically reduce emissions enough to bend the temperature curve down - both because that is technically and politically highly unlikely and because it wouldn’t make much of a difference in temperatures in the next few decades even if it did happen. 

At the same time the overwhelming consensus of scientists activists and decision makers is to reject the use of SRM. 

So we now can clearly see what economists would call the revealed preference of the Climate community. 

So at least implicitly probably 90+ percent of the relevant Climate leadership community is willing to live with temperatures and impacts much more extreme than now being experienced (or at least they are willing to have other people live in those conditions ) rather than taking a chance on SRM. The reasons and motivations why this is the case can be disputed and are no doubt varied but not this reality. 

Therefore it is imperative that efforts involving key respected institutions be organized to create an objective science based inclusive process to bring these multiple stakeholders by discipline geography and otherwise together to attempt to reach something like a consensus that answers the question “ At what point”. 

And the reason again why this is necessary is because there is clearly an overwhelming consensus that the world is nowhere near needing to consider deploying SRM given current and projected conditions and what is known or believed to be known about the risks and rewards of SRM. 

The answer may well be not to use GMST as the primary metric for reasons you have been consistently arguing for years Mike.  

Perhaps it’s a composite of wet bulb temperatures affecting X hundreds of millions of people by Y year, together with a greater than 50% chance of multiple breadbasket failures within x years plus a high likelihood of tropical diseases spreading to X hundred million more people by these years and so forth. Or any number of similar metrics. 

Creating such a process and outcome would then challenge all those adamantly against SRM to justify why they would be willing to have other people suffer at a scale likely in the billions rather than deploy cooling portfolios once they are shown to be acceptably safe and acceptably effective. 

Creating such a process does not guarantee that SRM will be deployed in time. But absent such a process it’s hard for me to imagine a scenario where sufficient social acceptance to allow cooling to proceed will occur in time to avoid existential irreversible planetary calamity. 

And social acceptance however defined is the single most important factor in determining whether and how SRM will be seriously considered by the powers that be. 

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

[Alan Kerstein]

Herb,

The metric that I propose is the fraction of the human population that, on a typical day, is subject to a combination of heat and humidity that would kill a typical person who is not in a climate-controlled venue. This metric should be applied based not on current conditions but on conditions extrapolated as far in the future as would be required for effective climate cooling to be underway. This would incentivize preparatory measures that reduce the extrapolation range. In other words, if you don't like SRM, invest in the long-lead-time preparations that make the case for SRM less compelling so we can wait a while longer to see whether fantasies about ERA efficacy come true.

Alan

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[Michael MacCracken]

I like the idea, though I might focus on the average over say the highest ten days rather than a typical day.

Best, Mike

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