AI on the Contradiction between Jim Hansen's estimate of "10°C global warming in the pipeline" and mainstream science
Clive Elsworth
At the risk of annoying those who dislike unverified AI answers, I found this one helpful:
[Edited] Can you resolve the difference between Jim Hansen’s estimate of global warming in the pipeline of 10°C above global average pre-industrial temperature and your previous answers from mainstream science?
Warming in the pipeline: Decoding our climate commitment
James Hansen and the scientific contest about accelerated ...
just stop oil – no more oil and gas
Hansen's revolutionary call to action - Just Stop Oil
James Hansen's New Paper and Presentation
The apparent contradiction between Jim Hansen's estimate of "10°C global warming in the pipeline" and mainstream science or my previous answers arises from fundamentally different assumptions about what is meant by "in the pipeline" and the conditions held constant after emissions stop.
1. Hansen's "Global Warming in the Pipeline"
- Jim Hansen and colleagues estimate that, if atmospheric greenhouse gases remain fixed at current levels (around 420 ppm CO₂ and corresponding concentrations of other GHGs) for millennia, and slow feedbacks such as ice sheet loss and long-term albedo changes are allowed to fully operate, the ultimate "equilibrium" global warming is about 10°C above pre-industrial levels (with some reduction, to ~8°C, if we factor in today's aerosol cooling).theclimatebrink+2
- This is not a prediction for the 21st century—but a theoretical maximum if today's forcing persists indefinitely until the slowest components (deep ocean, major ice sheets) equilibrate.
- Hansen assumes "constant atmospheric concentration" (not net zero emissions), meaning future emission would need to exactly balance all natural removal, which does not occur in standard net zero scenarios. theclimatebrink
2. Mainstream/IPCC "Warming in the Pipeline"
- Mainstream climate science (including IPCC assessments and my earlier answers) defines "committed warming" as the additional temperature rise expected after net zero emissions, allowing the carbon cycle to operate freely.
- In these scenarios, when emissions stop, atmospheric CO₂ begins to decline naturally due to uptake by oceans and land, and radiative forcing decreases over time. theclimatebrink
- "Warming in the pipeline" is typically estimated at ~0.2–0.5°C above the temperature at net zero, resulting in stabilization near or slightly above where net zero is reached for multi-decade timescales. juststopoil+2
3. Differences in Feedbacks and Time Frames
- Hansen's 10°C includes both "fast" (water vapor, clouds, sea ice) and "slow" (ice sheets, permafrost methane, biogeochemical, vegetation, long-term albedo) feedbacks, realized over centuries to millennia.
- Standard models focus on fast feedbacks and decades-to-century timescales, predicting stabilization much lower—around 1.5–3°C, depending on emission scenarios, because CO₂ doesn't remain at peak levels indefinitely. cascadeinstitute+2
- Hansen's scenario is intentionally an upper-bound "what if all feedbacks are unleashed with constant greenhouse levels?"—not a forecast given net zero and carbon drawdown.
4. Summary Table
Approach | Assumes CO₂ After Net Zero | Feedbacks Included | Long-term Warming "in the Pipeline" |
IPCC/Mainstream | Declines via carbon sinks | Fast only (decades) | ~0.3–0.5°C beyond net zero temp |
Hansen (10°C) | Held constant for millennia | Fast + Slow (millennia) | Up to 10°C equilibrium |
5. Reconciling the Estimates
- The difference lies in assumptions about the fate of CO₂ after net zero and the time scales and feedbacks considered.
- Hansen's estimate is not inconsistent with current science, but it is a hypothetical scenario assuming CO₂ concentrations locked at today's levels until all feedbacks play out over thousands of years—unlike real-world paths, where negative emissions and carbon sinks would lower atmospheric CO₂ after net zero is achieved. juststopoil+2
- Conventional projections, and my previous answers, reflect expected policy actions (net zero) and natural sinks, addressing policy-relevant warming for the coming century rather than extreme, artificial steady-state scenarios.
Key references:
- The Climate Brink, "Warming in the pipeline: Decoding our climate commitment" (2023)theclimatebrink
- Just Stop Oil, "Hansen's revolutionary call to action" (2024)juststopoil
- Cascade Institute, "Listen to Hansen's warning on climate..." (2023)cascadeinstitute
- Oxford Open Climate Change, Hansen et al., "Global warming in the pipeline" (2023)
- Hansen & Kharecha, "The Acid Test: Global Temperature in 2025" (2025)
- IPCC AR6, Chapter 4, and net zero commitment literature
In essence: Hansen's 10°C in-the-pipeline figure assumes permanent peak greenhouse gas concentrations with all feedbacks realized over millennia, whereas IPCC and conventional answers assume atmospheric concentrations fall after net zero, yielding much less "committed" warming.
My view: Mainstream scientists have a big blind spot on the inertia of the fossil fuel economy.
Clive
Tom Goreau
Long term feedbacks operate over thousands of years, and are generally ignored in IPCC projections, which are intrinsically underestimates of how the real world responds because they include only the short term feedbacks that are well enough understood to predict and not the long ones.
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Robert Chris
To: 'healthy-planet-action-coalition' <healthy-planet-...@googlegroups.com>
Subject: [HPAC] AI on the Contradiction between Jim Hansen's estimate of "10°C global warming in the pipeline" and mainstream science
Clive Elsworth
Robert C
What I found helpful was it summarised the different assumptions made by ‘mainstream scientists’ vs Hansen.
To me, those different assumptions are driven by:
- Mainstream scientists: Who pin their hopes on a near-term net-zero, and in which carbon sinks remain intact. By doing so they disregard:
- the near-term incentives that undermine a near-term net-zero: National security, Energy security, Food security, Cost of capital, etc.
- the enormity of the change of heart needed from a vastly improved public understanding on climate issues.
Reality check: You only need to compare the likelihood of a sensible climate outcome with the likelihood of governments acting to avoid a financial crash – the fundamentals of which are shared far more widely and lucidly and avoidance of which would be far less painful – to be pretty sure that net-zero isn’t going to happen any time soon.
- Hansen: Whose assumptions on greenhouse gas levels are consistent with more plausible policy outcomes (if still over-optimistic). His assumptions thereby provide a more plausible view – of the sort of thing that’s likely to happen to global average temperatures in the coming decades and millennia.
Forgive me if this was already blindingly obvious. I find it useful to summarise the nub of the problem as succinctly as I can.
Of course, the above picture is muddied by moral hazard on one extreme and climate denial on the other, but I think it’s a useful backdrop that explains why cooling is not currently favoured by policymakers. Their inaction is justified by mainstream science, which means they can avoid any public backlash against nasty new policies on weather modification etc. Instead, they play along with the scientists’ pipe dream of net-zero. Those that eschew net-zero simply ignore the dangers of a warming world.
Meanwhile species loss accelerates, tipping points are starting to get crossed, etc. Perhaps what is needed is massive financial losses by the rich and powerful – ASAP.
Clive
Tom Goreau
IPCC’s problem is that it relies on consensus of models (i.e take the average and ignore the outliers, but Hansen et al.’s model is an outlier because it includes more, though not all, of the long-term feedbacks compared to the rest, i.e. it is far more accurate and should be strongly weighted accordingly instead of dismissed).
The models miss so many feedbacks they can’t be trusted when they all, even Hansen et al., consistently underestimate the real climate change sensitivity in the past and in the latest projections.
Since AI is trained on the mass of publications, no wonder it spits back the average opinion, no matter how poorly informed that is. You can see how people on this list are playing AI to give back the answer they want by selectively feeding it information!
That is not a strategy to improve knowledge, but for at the minimum regression to the mean, on the average for trivia, and at worst, mass delusion, of which we seem to have far more than we need almost everywhere!
Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance
Chief Scientist, Biorock Technology Inc., Blue Regeneration SL
Technical Advisor, Blue Guardians Programme, SIDS DOCK
37 Pleasant Street, Cambridge, MA 02139
gor...@globalcoral.org
www.globalcoral.org
Phone: (1) 857-523-0807 (leave message)
Books:
Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase
Innovative Methods of Marine Ecosystem Restoration
On the Nature of Things: The Scientific Photography of Fritz Goro
Geotherapy: Regenerating ecosystem services to reverse climate change
No one can change the past, everybody can change the future
It’s much later than we think, especially if we don’t think
Those with their heads in the sand will see the light when global warming and sea level rise wash the beach away
“When you run to the rocks, the rocks will be melting, when you run to the sea, the sea will be boiling”, Peter Tosh, Jamaica’s greatest song writer
“The Earth is not dying, she is being killed” U. Utah Phillips
“It is the responsibility of intellectuals to speak the truth and expose lies” Noam Chomsky
From:
healthy-planet-...@googlegroups.com <healthy-planet-...@googlegroups.com> on behalf of Clive Elsworth <Cl...@EndorphinSoftware.co.uk>
Date: Wednesday, August 6, 2025 at 8:29
AM
To: 'healthy-planet-action-coalition' <healthy-planet-...@googlegroups.com>
Subject: RE: [HPAC] AI on the Contradiction between Jim Hansen's estimate of "10°C global warming in the pipeline" and mainstream science
Robert C
What I found helpful was it summarised the different assumptions made by ‘mainstream scientists’ vs Hansen.
To me, those different assumptions are driven by:
Mainstream scientists: Who pin their hopes on a near-term net-zero, and in which carbon sinks remain intact. By doing so they disregard:
- the near-term incentives that undermine a near-term net-zero: National security, Energy security, Food security, Cost of capital, etc.
- the enormity of the change of heart needed from a vastly improved public understanding on climate issues.
Reality check: You only need to compare the likelihood of a sensible climate outcome with the likelihood of governments acting to avoid a financial crash – the fundamentals of which are shared far more widely and lucidly and avoidance of which would be far less painful – to be pretty sure that net-zero isn’t going to happen any time soon.
Hansen: Whose assumptions on greenhouse gas levels are consistent with more plausible policy outcomes (if still over-optimistic). His assumptions thereby provide a more plausible view – of the sort of thing that’s likely to happen to global average temperatures in the coming decades and millennia.
H simmens
Issues raised in our paper are relevant to understanding the course of climate change. So, how is it that a small (all-male)[5] clique is able to control the climate research conversation? “
Clive Elsworth
Tom
I’m trying to look from the policymaker point of view, and why they won’t consider cooling interventions. That was the main discussion in our last NOAC meeting.
You are looking from the scientists’ point of view - fair enough. We will always need that.
Clive
Tom Goreau
This very important ruling is negated by the fact that the US, Russia, and China refuse to accept any international Court rulings, making them outlaw nations promoting collapse of global climate for short term greed.
From:
H simmens <hsim...@gmail.com>
Date: Wednesday, August 6, 2025 at 9:28 AM
To: Tom Goreau <gor...@globalcoral.org>
Cc: Cl...@endorphinsoftware.co.uk <Cl...@EndorphinSoftware.co.uk>, healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>
Subject: Re: [HPAC] AI on the Contradiction between Jim Hansen's estimate of "10°C global warming in the pipeline" and mainstream science
Herb Simmens
Author of A Climate Vocabulary of the Future
“A SciencePoem and an Inspiration.” Kim Stanley Robinson
@herbsimmens
HerbSimmens.com
On Aug 6, 2025, at 8:44 AM, Tom Goreau <gor...@globalcoral.org> wrote:
