Some highly interesting intricacies to cool down a water planet - we have to understand in how far we can cool down Earth as the oceans will work against it

[Jan Umsonst]

Hi all, here a study complex that is important in terms of what it means to cool down a water planet...

1: Even if we reduce our emissions fast global warming rates will continue for at least a decade. But nothing less should be suspected, so no real surprise here, just a confirmation that there is warming in the pipeline. Fun fact: the argument that zero emissions and declining GHG levels afterward will cancel out warming effects of ongoing ocean warming is theoretical nonsense. It's simple: the first decades continuing ocean heat uptake will happen at the highest rates while declining GHG levels will need decades to reach a substantial effect - hence there is warming in the pipeline the first decades. While the above study would mean that during the first decade high warming rates continue.

"Constraints on Climate Change Stabilization Based on Observations of Earth's Energy Imbalance"; https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL121056

2: Even under GHG stabilization El Ninos will continue to bulb out heat. They could even become 40-80% stronger. This result which will be correct to some extent at least. It means that while we start to cool the climate down substantially, temperature jumps will still frequently happen at least for some time and which will remain massive.

"Deep ocean warming-induced El Niño changes"; https://www.nature.com/articles/s41467-024-50663-9

3: If we stopped our emissions after centuries, the climate started to cool down the oceans will abruptly burb out heat which will lead to comparable warming rates then anthropogenic global warming. The problem with this result is that they speak of deep ocean heat being brought upward by deep convection. We have now also a massive heat accumulation across the first 700m with distinct hot spots where warm water bubbles grow and warm which are also becoming fresher. This whole line of research is still in its infancy hence it's not clear in how far the mid-latitude oceans will release heat when we cool the climate down.

"Southern Ocean Heat Burp in a Cooling World"; https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025AV001700

A worst case scenario: 

Let's say we start global cooling in the mid 30s when we will have reached a temperature niveau above 2°C - could be even 2.5°C if ocean heat uptake rates now accelerate surface warming what we should suspect along with further cloud declines over warmer oceans. In the first decade global warming will continue driven by ocean heat which we will have additionally to cool down. Hence, we could fast end up needing to cool down the climate by more than 1.5 °C just to stat at the 1.5°C temperature level which temperature jumps still happening. 

If we try to cool to such an extent the climate the side effects could be massive while increasing rates of aerosols in the atmosphere will suppress outgoing longwave radiation (OLR) the more we aerolize the atmosphere which will make it harder for the oceans to loose heat to space. This has to be understood: the only way oceans can cool down is via heat loss to the atmosphere, and this heat release would have to be countered by SRM.

Hence, we will have to understand to what extent SRM can cool down the climate against oceans loosing more heat of which more will remain in the atmosphere due to reduced OLR values to space. And for that highly idealized simple model experiments won't do as we would need to simulate current boundary conditions of ocean heat which models are not able to reproduce. Further, models are very bad at deep currents, mixing processes, in part with atmospheric circulation changes, and evaporation parametrizations over the oceans are as well quite simple compared to the complex reality. Hence, maybe we would even need to wait for new high resolution model generations that need much higher computational power than we currently have to understand the above complex.

Just as a reminder that it's not so easy as just to restore Earth's albedo and all is nice and well again. It's not even clear to what extent we can cool the climate down against oceans continuing to warm that try to cool down via heat loss to the atmosphere. As long as we haven't solved these issues we just do not know in how far SRM can work.

Best

Jan 

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[Tom Goreau]

You can see the wide range of model ENSO projections here:

 

https://coralreefwatch.noaa.gov/satellite/analyses_guidance/enso_current_conditions.php

 

 

 

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[Tom Goreau]

To see how all over the place the models are:

 

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[John Nissen]

Hi Jan,

I think you are fundamentally wrong about oceans releasing heat. They have been absorbing heat steadily for millennia, since their mean temperature (at the actual surface) has been significantly lower than the atmosphere's. The problem now is ocean stratification which reduces heat uptake by oceans. This will accelerate global warming as it is a positive feedback. Ouch!

Cheers John 

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[Jan Umsonst]

Hi, 

Tom and me wrote a full article on it, with Kevin Trenberth not denying that we had a strong point so yes I'm aware of it.

Fun fact: another leading expert even wants to help Tom and me to make a review study on it, which I'm not able to do as I like to go too much into the details but Tom and me will deliver - Tom pushes me what I need :D

And that I'm fundamentally wrong is not backed up by science which clearly states that I'm correct. But to what extent will oceans prevent us to cool down the system?

Sadly, opinions are more important than scientific facts - the reason I attached the studies but to no avail...

The question is only to what extent ocean heat will prevent us cooling down the system?

Sure, you can think otherwise but for the physical Earth system our opinions do not matter a bit...

Fun fact: Kevin Trenberth mentioned it himself in a study that our main problem is that we have already too much energy in the system and that SRM will make the problem worse as it suppresses OLR to space, while net zero tackles the problem at its root.

Advocating SRM comes with a great responsibility as if it goes wrong or does not work as planned we just provided another stepping stone on our staircase to extinction.

Therefore, it's especially the SRM community which has to heed the latest science as we have to act accordingly to it.

Further, my argument means essentially that we have to start now solar dimming as we have to prevent the oceans from overheating as otherwise the heat in the oceans will become a roadblock at one point to dim down surface temps as much we will need it.

Further, if you would have read our article on the feedback complex that we missed you would have realized that stratification first shifts ocean heat uptake to shallower depths which supports higher SST which come with a cloud feedback driving first ocean heat uptake to higher levels.

Which then leads to higher rates of latent heat release to the atmosphere. Mid latitudes during winter already becoming operational as a new feedback - studies coming out recently as it is obvious now.

Hence, stratification increases ocean heat uptake and heat loss to the atmosphere which then reduces ocean heat content increases as more is lost to the atmosphere.

So technically it's incorrect that stratification reduces heat uptake ;)

You can ignore the feedbacks, but they won't ignore us...

Best

Jan

[Tom Harris]

Following up on Jan's email, here is the link to the article:

https://drtomharris.substack.com/p/the-great-decoupling-how-ocean-stratification

Tom

[John Nissen]

Hi Jan,

There are graphs showing how much heat is being absorbed by the oceans. This isn't going to suddenly reverse.

Cheers John 

[Jan Umsonst]

Hi John, 

do you really think you can stop a water planet to further heat up if the oceans continue to heat up at such a rapid pace? Hence, SAI needs to massively reduce ocean heat uptake, while the question yet remains of how the heat already in the oceans will react?

In principle this means that before these questions aren't answered to the best of our abilities - high resolution models with historical heat uptake patterns - we should be careful spreading the idea to cool down a water planet is simple as we only need to restore Earth's albedo...

Best

Jan

[Jan Umsonst]

Hi John, I give you another example

Let's say we mange to cool down the Arctic and stabilize the AMOC again - what does that mean? It means essentially that the system starts to pump more heat into the Atlantic and from there to the subpolar Atlantic and Arctic Ocean.

But this heat is sourced from the Southern Hemisphere and tropical Oceans. So can you be sure that an intensification of Northward heat transport won't counter our efforts to cool the Arctic?

Here you see the problem:

I can only repeat myself - before we spread that we can cool down the system easily by restoring Earth's albedo (anyhow not possible as it will be a different one) we should make damn sure that this is really possible to a substantial degree...

Best

Jan 

On 6/13/26 02:28, John Nissen wrote:

[Ron Baiman]

Dear Tom and Jan,

Fantastic work, IMHO (hoping that folks more knowledgeable than me on these topics will give it a look!). 

A couple of (off the top of my head) though thoughts  is that this might be cause for coupling SRM efforts with OTEC to re-enhace ocean mixing while replace forms of human energy (and heat) production in the atmosphere? See quick summary on p. 14-15 of this: https://academic.oup.com/oocc/article/4/1/kgae014/7731760

It also seems to reinforce the point make in Tom's Oct 8 substack that we're probably going to need sunshades  in addition to SAI as part of the longer term effort to avoid going up in smoke as we try to restabilize climate and ecosystems on our poor (for us and current species) planet!

Best,

Ron

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[Michael MacCracken]

Dear Jan--While I'll agree that we need to do additional research, requiring that we do to the "best of our abilities", which I will assume means with high statistical confidence as in the scientific tradition, is likely to take so long it will never be achieved, just as significant uncertainties remain about what will happen if we do not pursue intervention. We are facing a systemic threat that could have exceedingly disastrous consequences and imposing the scientific standard for proof is just not appropriate for deciding what steps to take. Indeed, it has been scientific caution in stating what the threat is that has led to the putting off of appropriate actions. What we need to consider is relative risks of going forward with and without intervention, and I'd suggest the risks of going forward with intervention are likely to be well less than going forward without it.

Best, Mike

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[Alan Kerstein]

Mike,

My understanding is that Jan is commenting specifically on the effect of eventual deployment of SAI that is intended to cool the planet rather than just slow the temperature rise. Any SAI deployment would accomplish the latter well before it produces net cooling, at which point we'll know a lot more about SAI effects and climate dynamics than we know now. So ongoing discussion of longer-term considerations shouldn't detract from the case for the urgent near-term intervention that you mention.

Alan

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[John Nissen]

Hi Jan,

I've read through your joint paper with Tom Harris [1] and I now see where you are coming from.  There are terrifying feedbacks for ocean stratification and the heating of surface water to accelerate global warming.

But you may not know where I am coming from.  I have been studying the Arctic as a critical component of the Earth System, crucial to the operation of the Milankovitch cycles in causing the coming and going of glacial periods.  The Arctic is currently in unmitigated meltdown, and threatens to upset the whole Earth System, with devastating consequences for humanity.

With my insights, I can add another feedback to your list.  With rapid Arctic warming, the temperature gradient from the Arctic to lower latitudes is diminishing.  This gradient provides the energy driving the Rossby waves eastwards round the planet.  With less energy, the waves are tending to stick for longer periods, hence we get longer periods of "stuck weather" which creates greater extremes of heat, flooding and drought. With the sticking weather, winds are reduced, aggravating the situation as you describe in your paper.  Sticking weather can cause Marine Heat Waves.

Our suggested strategy is to cool with SAI, starting with injection at 50-60 latitudes to cool the Arctic and surface water flowing into the Arctic from the North Atlantic, North Pacific and some major rivers in Alaska, Canada and Russia.

The modelling done by Doug MacMartin et al. suggests that the Arctic could be cooled by 2C, injecting a certain amount of SO2 each year for a few decades.  They have tried and failed to find any unmanageable side effects.  Benefits include reversing the trend towards more extremes from stuck weather.

Further cooling by SAI, more globally, could hopefully stem the feedbacks that are currently operating through ocean stratification and reduced cloud cover.

As Mike says, we cannot afford to pursue the precautionary approach of waiting till the science is more certain.  It is certain enough to show that SAI deployment to refreeze the Arctic is extremely urgent and deployment to reverse global warming is almost as urgent. 

Now we need to get on and spread the word to those with power to make things happen.

Cheers, John

[1] https://drtomharris.substack.com/p/the-great-decoupling-how-ocean-stratification