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Fool us once: the effort to covertly bring RCP8.5 back to climate policy? - C C - Sep 25, 2026
https://rogerpielkejr.substack.com/p/fool-us-once
EXCERPTS: Yesterday’s New York Times featured an op-ed by David Wallace-Wells and Zeke Hausfather — a journalist and climate scientist respectively — both well-known for their commitments to climate advocacy. Normally, yet-another-apocalyptic-op-ed would not be worth commenting on, as they are a dime a dozen.
However, yesterday’s op-ed demonstrates how the new CMIP7 climate scenarios — discussed in detail here at THB — can be used to smuggle the implausibly extreme and retired RCP8.5 right back into discussions of climate science and policy. According to Hausfather, an IPCC AR7 lead author, the IPCC AR7 is going to adopt this strategy as well.
Misuse of RCP8.5 started early and snowballed from there, because no one corrected correctable missteps early on. We should not fall for this again.
The op-ed starts off well enough, asserting accurately: "Projected future warming has fallen quite a bit, and a worst-case emissions scenario known as “RCP8.5” - in which coal use would roughly quintuple by 2100 - is being phased out as implausible."
The op-ed then takes a sharp turn. Wallace-Wells and Hausfather claim: "A new round of forecasts from the climate science community is pretty alarming."
There are no new “forecasts” from the “climate science community.” The IPCC has always carefully explained that it does not forecast the future — appropriately so. It produces projections conditional on scenarios.
Further, the results of earth system model research with such conditional projections incorporating the new scenarios are still a ways off. An assessment of the “climate science community” will have to await the IPCC AR7.
[...] "The high-end warming sometimes described as a 'worst-case scenario' remains very much on the table, too."
That last sentence is a not-so-subtle reference to the climate outcomes that emerged from the retired RCP8.5. How can it be that RCP8.5 is being “phased out” yet its implications remain ”very much on the table”?
Below I show how RCP8.5 is being brought right back into the discussion of climate science and policy via a Trojan Horse that carries a misuse of scenario extensions... (MORE - missing details)
RE: Fool us once: the effort to covertly bring RCP8.5 back to climate policy? - confused2 - Sep 26, 2026
While I find 'The Honest Broker' to be a intelligent commentator I'm not entirely sure of his honesty particularly when it comes to climate change.
Pielke Wrote:can be used to smuggle the implausibly extreme and retired RCP8.5 right back into discussions of climate science
I have neither the will nor the time to follow Pielke down every rabbit hole he finds but I suspect he's found something that works for him that, as far as I can make out, is unrelated to the actual CMIP7.. to the extent that the only person trying to smuggle the retired RCP8.5 back into discussions is Pielke himself.
CMIP7 Wrote:CMIP7’s high scenario comes in remarkably lower [than RCP8.5] at 3.3C (2.6-4.4C) [in 2100].
The downward revision of future emissions in CMIP7 reflects two key changes since RCP8.5 was published back in 2011. First, the plausible baseline of a repeal of current policy has fallen. Cheap solar, wind and batteries, a global plateau in coal use and more than $2tr per year in clean-energy investment mean that a rollback in climate policy would not result in coal deployment levels assumed in the RCP8.5 scenario.
More details .. https://www.carbonbrief.org/explainer-the-cmip7-emissions-scenarios-and-how-they-explore-future-climate-change
RE: Fool us once: the effort to covertly bring RCP8.5 back to climate policy? - Syne - Sep 26, 2026
From the New York Times op-ed:
... Global warming is real, that story goes, but it is turning out to be less frightening than we were told.
There is some truth here. The world has made real climate progress over the past decade, projected future warming has fallen quite a bit, and a worst-case emissions scenario known as “RCP8.5” — in which coal use would roughly quintuple by 2100 — is being phased out as implausible.
But a new round of forecasts from the climate science community is pretty alarming.
...
But because we’re still burning an awful lot of fossil fuel — and because the climate itself may have some surprises in store — harrowing temperature increases remain unnervingly possible. It’s not just that by moving too slowly we’ve lost the opportunity to avoid disruptive climate change. The high-end warming sometimes described as a “worst-case scenario” remains very much on the table, too.
...
RE: Fool us once: the effort to covertly bring RCP8.5 back to climate policy? - confused2 - Sep 27, 2026
Pielke Wrote:The “forecasts” cited in the op-ed to the “climate science community” are in fact produced for a blog post by . . . Hausfather.
The blog post by ... Dr Zeke Hausfather..
Quote:The top of the scenario range has fallen for the first time in four generations of climate modelling. The highest scenarios used in the three previous IPCC assessment cycles all produced around 4.6-4.9C of global warming in 2100, whereas CMIP7’s high scenario only reaches 3.3C and has around half the cumulative CO2 emissions.
In full - https://www.carbonbrief.org/explainer-the-cmip7-emissions-scenarios-and-how-they-explore-future-climate-change
If the highest current estimate [Hausfather/IPCC] is 3.3C .. where are you seeing RCMP8.5 .. predicting 8.5C ??
Pielke does include a bargraph showing CO2 in 2050 at the same level as RCMP8.5 assumed in 2100 .. Source: (surprise!) analysis by Roger Pielke Jr., The 'Honest' Broker .. which would be (partly) why I'm less than convinced of his honesty.
RE: Fool us once: the effort to covertly bring RCP8.5 back to climate policy? - Syne - Sep 27, 2026
Someone seems to be conflating the RCP8.5's prediction of a global temperature increase of roughly 4.3°C to 4.8°C (7.7°F to 8.6°F) by 2100 relative to pre-industrial levels with its prediction of radiative forcing reaching 8.5 watts per square meter (W/m²) of extra trapped heat by the end of the century.
Not predicting 8.5C, predicting a mere 1C higher than the current worst case scenario.
The Representative Concentration Pathway 8.5 (RCP8.5) predicted a global temperature increase of roughly 4.3°C to 4.8°C (7.7°F to 8.6°F) by 2100 relative to pre-industrial levels.
Radiative Forcing: Reaches 8.5 watts per square meter (W/m²) of extra trapped heat by the end of the century.
The worst-case scenario in CMIP7 (the High "H" scenario) projects a preliminary global warming estimate of around 3.5°C above pre-industrial levels by 2100, which is roughly 1°C lower than the extreme CMIP6 worst-case scenario (SSP5-8.5, which peaked near 4.5°C).
Literacy is amazing!
RE: Fool us once: the effort to covertly bring RCP8.5 back to climate policy? - confused2 - Sep 27, 2026
You're partially right .. yes I did assume sane everyone uses centigrade .. 8.5W/m^2 is a coincidence.
If RCP8.5 is debunked .. why is Pielke producing a bargraph showing a the same amount of CO2 in 2050 as RCP8.5 assumed in 2100 .. with (agreed) extreme assumptions?
RE: Fool us once: the effort to covertly bring RCP8.5 back to climate policy? - Syne - Sep 27, 2026
(Sep 27, 2026 01:43 AM)confused2 Wrote: You're partially right .. yes I did assume sane everyone uses centigrade .. 8.5W/m^2 is a coincidence.
If RCP8.5 is debunked .. why is Pielke producing a bargraph showing a the same amount of CO2 in 2050 as RCP8.5 assumed in 2100 .. with (agreed) extreme assumptions?
Do you mean 2150? Still having trouble reading?
Seems obvious that he's showing the similarity to the debunked RCP8.5, showing up 50 years later in the CMIP7. That's the whole point of the article.
RE: Fool us once: the effort to covertly bring RCP8.5 back to climate policy? - confused2 - Sep 27, 2026
Pielke is a fellow of the American Enterprise Institute .. donors include the Charles Koch foundation .. this suggests an interest in climate change denial though to what extent he is paid to promote this is unclear.
https://en.wikipedia.org/wiki/American_Enterprise_Institute
His MO seems to be sniping at others which works for the people who regard him as 'credible' and not so much for people who think he's a shill.
What is unknown is the future concentration of CO2 in the atmosphere.
![[Image: 500px-Mauna_Loa_CO2_monthly_mean_concent...=thumbnail]](https://thumb.wikimedia.org/wikipedia/commons/thumb/c/c5/Mauna_Loa_CO2_monthly_mean_concentration.svg/500px-Mauna_Loa_CO2_monthly_mean_concentration.svg.png?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)
We do know that currently about half of the CO2 we produce annually is absorbed naturally so the level of CO2 in the atmosphere depends not only on the total amount of CO2 produced but over what timescale it is produced... Pielke has assumed 'something' but he doesn't say what... this is the art of obfuscation.
RE: Fool us once: the effort to covertly bring RCP8.5 back to climate policy? - Syne - Sep 27, 2026
I knew a genetic fallacy was incoming. 9_9
When you can't refute what's being said, refute who is saying it or why (appeal to motive fallacy).
RE: Fool us once: the effort to covertly bring RCP8.5 back to climate policy? - confused2 - Sep 27, 2026
Yes, it's complicated. Adding the same amount of CO2 over 150 years won't have the same effect as adding it over 100 years .. hence my point about the final level of CO2 and my aside that the 'honest' broker ignores iit.