Thoughts on this comment by Jan Umsonst?
H simmens
Author of A Climate Vocabulary of the Future
@herbsimmens
HerbSimmens.com
Jan Umsonst
Hi all,
will finish my overview on the obstacles of climate cooling and then write an E-mail with the link to this text for discussion.
I think it highly important that global cooling is not understood as simply "restoring" Earths albedo and problem solved. If we can't cool down the polar regions substantially global cooling runs into serious issues - e.g. Hemispheric temperature gradients control cloud cover, steer planetary circulation patterns which steer ocean heat uptake, poleward heat transport, blocking patterns, and impact duration's of extreme events.
And that we can cool down the polar regions to the same extent as the lower latitudes is far from certain.
Further, if we do not stop ocean heat uptake solar dimming will loose against ocean heat with time. So to what extent do we have to cool the climate that ocean heat uptake is stopped at any given GHG level?
And if GHG emissions are not stopped SRM will become suicidal if the above can't be solved besides e.g. photosynthesis, carbon sink, spread of toxic algae (e.g. ongoing acidification and oxygen minimum zones), or methane issues.
All the best
Jan
--
You received this message because you are subscribed to the Google Groups "Healthy Planet Action Coalition (HPAC)" group.
To unsubscribe from this group and stop receiving emails from it, send an email to healthy-planet-action...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/5F22A134-B571-4D1B-A6B1-50EFDBCA4D8E%40gmail.com.
-- Jan Umsonst Wallauer Str. 6D, 30326 Frankfurt am Main Tele: 0176 41114523 E-Mail: j.o.u...@gmail.com Performing Vitality: https://performingvitality.wordpress.com/
Michael MacCracken
Hi Herb--Regarding cooling of the Arctic, modeling results show that the relative effectiveness of SAI in high latitudes (so temperature change per unit of injected mass) is greater than at low latitudes. This is because, at least in part, just as when there is warming, the ice-albedo feedback process is activated, and getting more sea ice allows the surface temperature to drop as the sea ice slows the transfer of heat from the ocean up to the surface, and so an inversion can occur. When the surface ends up colder than the atmosphere (because it can radiate heat upward like a black body), the warmer atmosphere will lose heat to the surface by radiation and so also chill down. This will have the effect of tending to increase the equator to pole gradient and the effect of this tends to be increasing the zonal (west to east) strength of the jet stream, reducing the waviness that now leads to periods of warmth in the higher latitudes.
In the low latitudes, without SAI aerosols overhead, the temperature will be pulled down as the excess heat seeks to move poleward, but the temperature drop there will be a good bit (lot?) less than in high latitudes. Yes, there will be somewhat increase heat and moisture fluxes moving northward due to the increased gradient, but not enough to exceed the increasing ability to lose heat as sea ice gets formed and promotes chilling of the high latitude atmosphere. Indeed, if the Arctic were through the SAI process (with judicious injections so that the effect is operating only when the Sun is up), then the heat and moisture flux into the Arctic would drop, cooling it down.
So, I don't agree with the critique that is offered, that is that inducing high latitude cooling will lead to "catastrophic side effects."
Best, Mike
Oeste
Hi Herb,
Air movement and sea currents on our planet are driven by the enegy of sun radiation. Hence any dimming of sun radiation decreases these coupled movement processes. Such dimming effects can easy be studied during sun eclipses and the daily movements of the sun between dawn and noon. The vertical air movement which produces small cumulus clouds during summer time becomes sensitive decreased soon after onset of the eclipse. Even at partly darkened sun the cumulus clouds begin to disappear. This can be noticed by the disappearance of the cumulus clouds. Similar effects happen also during day time: when the sun leaves positions which are nearer to the horizon than to noon position no cumulus clouds develope.
Hence Jan's arguments seem right to me: any dimming including SAI will slow down air movement above the sea and also will weaken the ocean currents which depend on the air movement above the ocean. This dimming effect would also weaken the Brewer-Dobson air movement from equator to the poles which would expand the residence time of the injected SAI aerosol in the stratosphere. Dimming also reduces oxidation chemistry in the atmosphere. Consequences of these chemical effects had been discussed within the group for several times in the past.
Strong SAI effects on the albedo like that of a "nuclear winter" would surely be able to overwhelm any weakened heat transfer reductions between ocean and atmosphere. They would induce cooling of both, troposphere and ocean surface. This may be noticed also from the day-night cycles: during for instance the 12 hours of "nuclear winter" darkness night period the surface temperature decreases by 5 to 10 °C. According to the heat transfer from the warm water surface the nightly darkness period induced temperature decreases above sea are of lower level than above continental solid surfaces.
Franz
Michael MacCracken
Dear Franz--As a veteran of "nuclear winter" studies back in the 1980s, those scenarios absorbed of order 100% of solar radiation about the water vapor greenhouse gas effect, etc. and so caused large cooling (freezing on land for major scenarios). By contrast, the proposed stratospheric aerosol injection to offset GHG-induced warming would reflect back 1% or so of solar radiation in order to offset half of a CO2 doubling, so say from CO2 concentration from 450 ppm to 300 ppm (roughly preindustrial) and more realistically we might want to go from say 475 ppm to 350 ppm, so less than half a doubling, so reflecting a bit less than 1% of solar radation--and for context, clouds of various types block several tens of percent or more of the solar. All dire consequences that you mention are just huge overstatements.
Now, the direct beam would go down more but largely be compensated by diffuse radiation (a general brightening), so it would be a bit problematic for direct thermal energy generation that is based on mirrors reflecting direct solar radiation to the target. Given astronomers usually observe the night sky, the aerosol effect at night would be there but quite small in an absolute sense.
So, please stop talking about nuclear winter as anything close to being analogous--they are totally different.
Best, Mike
Bru Pearce
Fully agree with you Jan.
Thanks for all you work.
Bru
Pearce
E-mail b...@envisionation.org
Mobile +44 7740 854713
The Biosphere Restoration Plan enabled by Empathy Economics
Partisipate with Empathy Coin options
Information contained in this email and any files attached to it is confidential to the intended recipient and may be covered by legal professional privilege. If you receive this email in error, please advise by return email before deleting it; you should not retain the email or disclose its contents to anyone. Envisionation Ltd has taken reasonable precautions to minimise the risk of software viruses, but we recommend that any attachments are virus checked before they are opened. Thank you for your cooperation.
To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/dac24f78-6391-4220-9d97-8e9638d2c97b%40gmail.com.
rob...@rtulip.net
Hi Jan
I don’t think anyone suggests that global cooling can be “understood as simply "restoring" Earths albedo and problem solved.”
However, it may be possible to get broader political consensus on albedo action than on carbon action. That is not to say carbon action is not needed. Rather it is about effective sequencing of political decisions to cut through the current impasse.
Like the Montreal Protocol, a limited Albedo Accord could gain buy-in from industries who reject emission reduction. While not an ideal process, the UN now blocks this vital work on unscientific grounds. Sunlight reflection achieved through an Albedo Accord could stabilise temperature while the more intractable problem of CO2 is solved. Climate subsidy should be determined by cooling return on investment.
The growing resistance to emission cuts will not go away, making the rapid achievement of emission cuts impossible.
And the kicker is that even if emission cuts were possible, they would only affect climate at marginal scale. The carbon problem is about two trillion tonnes of CO2, plus methane etc that humans have added to the air. A five percent cut in world emissions would slow the annual increase of CO2 mass by 0.1%, from business as usual total of roughly 2,000,040,000,000 to climate action total of 2,000,038,000,000 tonnes of CO2 added to the air. Cooling action on tipping points is now prevented by the false rationale that to stop tipping points by cooling the Earth would slow down emission reduction efforts. In the face of tipping points, carbon is not a short term problem.
Regards
Robert Tulip
From: healthy-planet-...@googlegroups.com <healthy-planet-...@googlegroups.com> On Behalf Of Jan Umsonst
Sent: Friday, 3 October 2025 1:41 AM
To: healthy-planet-...@googlegroups.com
Subject: Re: [HPAC] Thoughts on this comment by Jan Umsonst?
Hi all,
To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/dac24f78-6391-4220-9d97-8e9638d2c97b%40gmail.com.