This is quite concerning because aerosols are NOT globaland this issue can not be dealt with using global only models. Indeed Morgenstern finds that models overestimate the effects of aerosols.
Morgenstern, O., 2024: Using historical temperature to constrain the climate sensitivity, the
In our own work, we find that the biggest heating is in the southern hemisphere where there are no aerosols.
Trenberth. K.E., L. Cheng, Y. Pan, J. Fasullo and M. Mayer, 2025: Distinctive pattern of global warming in ocean heat content J. Climate, 38, 2155-2168 https://doi.org/10.1175/JCLI-D-24-0609.1
Here heating is integrated through the ocean, not just surface temperatures.
Certainly aerosols have magnified warming in the northern hemisphere, but there is a LOT more to this.
Hi Dr. Trenberth, the results I get for both Chinese and shipping aerosol emissions changes are pretty near identical to what regionally-resolved ESM runs give. For example, the Chinese aerosol unmasking estimate of 0.06C (0.02C to 0.13C) warming by 2025 was validated by comparing it to the Samset et al. (2025) preprint (https://www.researchsquare.com/article/rs-6005409/v1), which finds a nearly identical best estimate of 0.07C (0.02C to 0.12C) using a large set of simulations from eight different Earth system models.
Thanks Zeke, I am impressed by your work and thorough approach. In our 2025 paper you may note that we refer to the role of the drop in Chinese aerosols and also the change in ship aerosols in the Atlantic in warming. The interactions with clouds, though, are important and not really a solved problem. We do note that the increase in sea surface temperatures appears to be a consequence, consistent with your results. But the heat penetration is not as deep as, and the warming is greater, in the southern hemisphere where aerosols have not played a role, but changes in the atmospheric and ocean circulation have. So there is more to it (as there always is).
"The figure above shows that Chinese SO2 declines were likely responsible for a global temperature increase of around 0.06C (0.02C to 0.13C) between 2007 and 2025, increasing to 0.7C (0.02C to 0.14C) by 2030."
Should it not be?
".... increasing to 0.07C (0.02C to 0.14C) by 2030."
SOx, like ozone, is bad for anything for lungs down here, but what if we injected it straight into the stratosphere or upper troposphere using my patented EZ Surefire Chemtrail® program?
Is there an underlying reason that Hansen's estimate is such an outlier? Is the science sound? Would it be reasonable not to include it in this meta analysis?
Too easy for the doubt, deny, delay crowd to promote aerosols as a good thing for reducing global warming (where they agree raised ghg's do cause warming) as something we should keep burning fossil fuels to sustain, but as well as make other problems, like acid rain, it doesn't reduce the enhanced greenhouse in any way, it (as you say) masks it. Stop the fossil fuel burning that makes sulfate aerosols and the cooling stops but the enhanced greenhouse warming doesn't stop when the CO2 emissions do.
How much controversy and uncertainty about climate change has the cooling effect of aerosols induced, including those 'imminent ice age' concerns as well as simply making enhanced greenhouse warming look like it was 'helpful' in counteracting that cooling? Although to be fair those 1970's global cooling concerns may have ultimately been helpful as that led to raising the profile and funding for the climate science that would go on to demonstrate clearly that global cooling was not going to persist (phew!) but (oh, no!) the reason was that global warming will. CO2 driven warming is the slow and persistent tortoise that overtakes the fast cooling aerosols 'hare', with enough time overtaking even without the hare stopping.
I find it a helpful perspective to keep in mind that the 'fast' cooling effect of sulfurous fossil fuel burning comes first, ahead of the 'slow' enhanced greenhouse.
Dream on! the most significant climate effects for the majority of the Northern Hemisphere has little to do with Carbon. As a matter of fact most climate models still do not consider their effects.
The upper atmosphere is continually invaded by man-made induced huge quantities of water vapor particularly in the upper latitudes of this hemisphere. When you have broken the natural water cycle in the upper reaches of our hemisphere, with many of the largest, now former rivers there, now dammed out of existence for almost 60 years waters impounded for hydroelectricity generation.
A Hemisphere Rewritten
What happens when nearly every northern river is placed under mechanical control?
Using the GRanD database and recent hydrological studies, we’ll map the infrastructural reprogramming of the Northern Hemisphere — and explore how seasonal flows, evaporative rhythms, and atmospheric feedbacks have shifted in its wake.
Russia’s Vapor Clock
Could climate anomalies follow a calendar of dam construction?
From the Kola Peninsula to Krasnoyarsk, we encounter a strange kind of synchrony: fog corridors that appear overnight, warming trends that begin the year a reservoir opens, and step-function changes in snowpack that defy natural variability.
The Quebec–Greenland Connection
Could a winter fog over Quebec help melt the Greenland Ice Sheet?
We follow one corridor of emissions — from the Brisay dam to Kuujjuarapik, and perhaps all the way to Greenland. What changed in 1993, and why did the melt signal shift so dramatically right after?
The Ocean’s Forgotten Diet
If rivers no longer feed the sea, who starves downstream?
Beyond vapor lies another feedback: nutrient interruption. We explore how dams trap silica and starve diatoms — the ocean’s base layer for carbon drawdown — weakening fisheries, collapsing food webs, and destabilizing marine carbon sinks.
Why the Models Missed It
If the signals are real, why don’t our models see them?
We examine how today’s climate models — powerful though they are — leave out certain thermodynamic and ecological loops. We explore the blind spots: vapor injections, nutrient phase shifts, and timing feedbacks too complex (or too localized) to be captured.
System Rewiring, Not Side Effects
What if these aren’t random anomalies, but parts of a single circuit?
This is where the threads converge. Not as chaos — but as a system. We’ll draw the feedback loops connecting reservoirs, vapor, snow, clouds, nutrients, and atmospheric structure — revealing a climate machine we may have rewired without realizing it.
The Test: Undo One Dam
If it’s real, we should be able to test it. Can we?
We propose a live experiment: select a single high-latitude dam, restore its natural flow, and observe the atmospheric and cryospheric response. It’s a hypothesis test — and a call to listen as scientists once again.
A New Vocabulary of Design
If vapor carries memory, how must our engineering evolve?
We close with language, metrics, and thresholds. What would “sustainable hydropower” mean if DOMEs were accounted for? What does feedback literacy demand of us — as designers, as planners, and as stewards of phase-state infrastructure?
What connects fog over Quebec to a starving ocean? Or a melt surge in Greenland to a jetstream gone rogue?
This image won’t answer — but it may begin to ask better questions.
Study it. Sit with it. If something feels off, you might be seeing the very thing the models missed.
We begin soon.
From snowpack collapse to silicate starvation, this diagram maps what official models omit — the possible systemic consequences of vapor-phase engineering across the Arctic north. Not a theory, but a question. Not a conclusion, but a pattern asking to be read.
This is quite concerning because aerosols are NOT globaland this issue can not be dealt with using global only models. Indeed Morgenstern finds that models overestimate the effects of aerosols.
Morgenstern, O., 2024: Using historical temperature to constrain the climate sensitivity, the
transient climate response, and aerosol-induced cooling. Atmos. Chem. Phys., 24, 8105–8123,
https://doi.org/10.5194/acp-24-8105-2024.
In our own work, we find that the biggest heating is in the southern hemisphere where there are no aerosols.
Trenberth. K.E., L. Cheng, Y. Pan, J. Fasullo and M. Mayer, 2025: Distinctive pattern of global warming in ocean heat content J. Climate, 38, 2155-2168 https://doi.org/10.1175/JCLI-D-24-0609.1
Here heating is integrated through the ocean, not just surface temperatures.
Certainly aerosols have magnified warming in the northern hemisphere, but there is a LOT more to this.
Kevin
Hi Dr. Trenberth, the results I get for both Chinese and shipping aerosol emissions changes are pretty near identical to what regionally-resolved ESM runs give. For example, the Chinese aerosol unmasking estimate of 0.06C (0.02C to 0.13C) warming by 2025 was validated by comparing it to the Samset et al. (2025) preprint (https://www.researchsquare.com/article/rs-6005409/v1), which finds a nearly identical best estimate of 0.07C (0.02C to 0.12C) using a large set of simulations from eight different Earth system models.
Similarly, for shipping aerosols all the radiative forcing estimates I'm using come from various different ESM runs (e.g. an 18-member ensemble of CESM2: https://acp.copernicus.org/articles/25/4443/2025/). More details and comparisons with ESM-based studies can be found in the methodology section at the end of the Carbon Brief article: https://www.carbonbrief.org/explainer-how-human-caused-aerosols-are-masking-global-warming/
Thanks Zeke, I am impressed by your work and thorough approach. In our 2025 paper you may note that we refer to the role of the drop in Chinese aerosols and also the change in ship aerosols in the Atlantic in warming. The interactions with clouds, though, are important and not really a solved problem. We do note that the increase in sea surface temperatures appears to be a consequence, consistent with your results. But the heat penetration is not as deep as, and the warming is greater, in the southern hemisphere where aerosols have not played a role, but changes in the atmospheric and ocean circulation have. So there is more to it (as there always is).
Best
Kevin
Nice work. I’ve wondered about the net effect of aerosol reduction and this work gives a good accounting of the range.
There is an error in your text:
"The figure above shows that Chinese SO2 declines were likely responsible for a global temperature increase of around 0.06C (0.02C to 0.13C) between 2007 and 2025, increasing to 0.7C (0.02C to 0.14C) by 2030."
Should it not be?
".... increasing to 0.07C (0.02C to 0.14C) by 2030."
Good catch, should be fixed now.
SOx, like ozone, is bad for anything for lungs down here, but what if we injected it straight into the stratosphere or upper troposphere using my patented EZ Surefire Chemtrail® program?
Thats a complicated subject, but you can find my thoughts here: https://www.theclimatebrink.com/p/the-geoengineering-question
Thanks!
(I still think of carbon dioxide removal via dumping of nutrients to stimulate ocean plankton growth as geoengineering, though.)
Not blinded by pollution.
Is there an underlying reason that Hansen's estimate is such an outlier? Is the science sound? Would it be reasonable not to include it in this meta analysis?
Too easy for the doubt, deny, delay crowd to promote aerosols as a good thing for reducing global warming (where they agree raised ghg's do cause warming) as something we should keep burning fossil fuels to sustain, but as well as make other problems, like acid rain, it doesn't reduce the enhanced greenhouse in any way, it (as you say) masks it. Stop the fossil fuel burning that makes sulfate aerosols and the cooling stops but the enhanced greenhouse warming doesn't stop when the CO2 emissions do.
How much controversy and uncertainty about climate change has the cooling effect of aerosols induced, including those 'imminent ice age' concerns as well as simply making enhanced greenhouse warming look like it was 'helpful' in counteracting that cooling? Although to be fair those 1970's global cooling concerns may have ultimately been helpful as that led to raising the profile and funding for the climate science that would go on to demonstrate clearly that global cooling was not going to persist (phew!) but (oh, no!) the reason was that global warming will. CO2 driven warming is the slow and persistent tortoise that overtakes the fast cooling aerosols 'hare', with enough time overtaking even without the hare stopping.
I find it a helpful perspective to keep in mind that the 'fast' cooling effect of sulfurous fossil fuel burning comes first, ahead of the 'slow' enhanced greenhouse.
Dream on! the most significant climate effects for the majority of the Northern Hemisphere has little to do with Carbon. As a matter of fact most climate models still do not consider their effects.
The upper atmosphere is continually invaded by man-made induced huge quantities of water vapor particularly in the upper latitudes of this hemisphere. When you have broken the natural water cycle in the upper reaches of our hemisphere, with many of the largest, now former rivers there, now dammed out of existence for almost 60 years waters impounded for hydroelectricity generation.
A Hemisphere Rewritten
What happens when nearly every northern river is placed under mechanical control?
Using the GRanD database and recent hydrological studies, we’ll map the infrastructural reprogramming of the Northern Hemisphere — and explore how seasonal flows, evaporative rhythms, and atmospheric feedbacks have shifted in its wake.
Russia’s Vapor Clock
Could climate anomalies follow a calendar of dam construction?
From the Kola Peninsula to Krasnoyarsk, we encounter a strange kind of synchrony: fog corridors that appear overnight, warming trends that begin the year a reservoir opens, and step-function changes in snowpack that defy natural variability.
The Quebec–Greenland Connection
Could a winter fog over Quebec help melt the Greenland Ice Sheet?
We follow one corridor of emissions — from the Brisay dam to Kuujjuarapik, and perhaps all the way to Greenland. What changed in 1993, and why did the melt signal shift so dramatically right after?
The Ocean’s Forgotten Diet
If rivers no longer feed the sea, who starves downstream?
Beyond vapor lies another feedback: nutrient interruption. We explore how dams trap silica and starve diatoms — the ocean’s base layer for carbon drawdown — weakening fisheries, collapsing food webs, and destabilizing marine carbon sinks.
Why the Models Missed It
If the signals are real, why don’t our models see them?
We examine how today’s climate models — powerful though they are — leave out certain thermodynamic and ecological loops. We explore the blind spots: vapor injections, nutrient phase shifts, and timing feedbacks too complex (or too localized) to be captured.
System Rewiring, Not Side Effects
What if these aren’t random anomalies, but parts of a single circuit?
This is where the threads converge. Not as chaos — but as a system. We’ll draw the feedback loops connecting reservoirs, vapor, snow, clouds, nutrients, and atmospheric structure — revealing a climate machine we may have rewired without realizing it.
The Test: Undo One Dam
If it’s real, we should be able to test it. Can we?
We propose a live experiment: select a single high-latitude dam, restore its natural flow, and observe the atmospheric and cryospheric response. It’s a hypothesis test — and a call to listen as scientists once again.
A New Vocabulary of Design
If vapor carries memory, how must our engineering evolve?
We close with language, metrics, and thresholds. What would “sustainable hydropower” mean if DOMEs were accounted for? What does feedback literacy demand of us — as designers, as planners, and as stewards of phase-state infrastructure?
What connects fog over Quebec to a starving ocean? Or a melt surge in Greenland to a jetstream gone rogue?
This image won’t answer — but it may begin to ask better questions.
Study it. Sit with it. If something feels off, you might be seeing the very thing the models missed.
We begin soon.
From snowpack collapse to silicate starvation, this diagram maps what official models omit — the possible systemic consequences of vapor-phase engineering across the Arctic north. Not a theory, but a question. Not a conclusion, but a pattern asking to be read.
Stay with me …
Did Chinese reduction in aerosols cause the California droughts in the mid 2010s?