Agreed that climate change scenario RCP8.5 is indefensible. One concern is that this acknowledgement will be used as "fuel" to undermine the seriousness of climate change (Trump has already done this). Now that we haved a climate change skeptic designated to head the National Climate Assessment (Dr. Matthew Wielicki), I suspect that all sorts of distoration about the seriouness of cliamte change will be brought into question. This brings me to my request for a future Honest Broker contribution--a thorough assessment of Dr. Wielicki's qualifications.
Roger thank you for this - I’m a farmer in New Zealand and climate change policy or should I say global warming alarmism influenced policy is affecting animal farming in 2 main ways: Firstly the very real problem of nitrate & phosphate leaching into waterways from our basically pasture based production systems conflated with RCP8.5 global warming scenarios is causing forecasts which are basically saying animal production will have to cease over large areas to get NO3 & phosphate leaching down to a sustainable level. If better future scenarios are used then actual practical solutions can be found for the leaching. Secondly NZ joined other first world countries at Kyoto and said it count biogenic methane emissions in its emissions inventory. This was always nonsensical and subsequent studies have shown the carbon cycle of CO2 in the atmosphere used in plant photosynthesis eaten by ruminant animals where some of the carbon eaten is emitted as methane which over around 10 yrs breaks down to CO2 which is used again in the plant photosynthetic process. It has been shown that if animal numbers are stable actual warming from the methane emissions is negligible. Some policy makers still want to tax animal methane emissions which is absolutely counter to increasing NZers economic wellbeing.
I’m not a farmer but I am well aware just how much farming contributes to the economy and while there are endless debates about how to improve our productivity, many farmers are highly innovative as can be seen by the success of firms like Halter and Gallacher.
Frank: Yes, nothing new. Part of the point that I made is that physicists have known about saturation for decades, and, as you've acknowledged, it isn't controversial. Yet that fact is being ignored by policymakers.
The 3.6 W/m2 of radiative cooling to space you noted is about 1.3% of the current total cooling average of about 277 W/m2. That's not completely saturated, but very nearly so after doubling atmospheric CO2 from about 400 ppm to 800 ppm. A tiny output for a massive input. The effect of doubling CO2 again after that will be even smaller as the effect of adding CO2 approaches an asymptotic limit. Conversely, if you remove half the atmospheric CO2, the cooling effect would be much, much larger. So it is quite reasonable for Schildknecht to call that effect saturation.
As for the Modtran prediction you cited, I don't believe that the Modtran model has been validated by the scientific method, i.e., matching Modtran predictions to actual observations. And, the forecast you mentioned seems to be contradicted by the comparative observations cited by Schildknecht. The consensus you cited has its uses, but it must never be allowed to trump the scientific method.
Here’s another model forecast. The MAGICC climate model is widely used for climate policy analysis, the EPA, and IPCC reports. MIT Prof. Richard Lindzen reported that if the U.S. reduced CO2 and other GHG emissions to net zero effective immediately, rather than waiting until 2050, the MAGICC model predicts the cooling effect on global temperatures would only be 0.17° C (0.31° F). A consensus result, but probably not validated by observation either. Still another reason why policymakers should not be using ANY speculative emissions scenarios to wield the force of government against a mostly free people.
Excellent summary. Thanks for bringing the NZ example that has essentially been replicated worldwide. And with similar damaging results.
One comment caught my eye - “Along the way, as mistakes were made, no one spoke up or pointed out the unfolding errors of scenario design and application.” I disagree with this. Those who brought up these mistakes were shouted down, excoriated and some drummed out of their professions.
I’m not sure which is worse - those who knew the flaws in this extreme scenario and pushed it anyway, or those who really believed it. All the while, ignoring the damage being done.
I like to think about sea level rise in terms of more tangible units of inches/decade. Today SLR is a little above 1 inch/decade and supposedly accelerating at about 1/3 inch/decade/decade. For the next few decades, SLR will be negligible compared with tides (a rise of about 1 m twice a day) and storm surges (another 1 m except during the strongest hurricanes). IMO, we will be facing only modest increases in danger for the next several decades. The problem is that some infrastructure is already in significant danger from past mistakes. The tidal basin and mall in Washington DC were built a century ago on fill that has settled two feet while while SLR. That fill buried a creek near the African American Smithsonian museum. Upwelling of water from underground causes flooding in many places in DC.
Speculation about future CO2 emission scenarios should not be a serious concern to policymakers. Physicists who specialize in radiative heat transfer in the atmosphere have long known that the greenhouse effect is effectively saturated above modern levels of atmospheric concentration.
The following is the opening paragraph from a paper entitled, “Saturation of the infrared absorption by carbon dioxide in the atmosphere,” International Journal of Modern Physics B Vol. 34 - 28 October 2020; Author: Physics Professor D. Schildknecht, Universität Bielefeld
“Based on new radiative transfer numerical evaluations, we reconsider an argument presented by Schack in 1972 that says that saturation of the absorption of infrared radiation by carbon dioxide in the atmosphere sets in as soon as the relative concentration of carbon dioxide exceeds a lower limit of approximately 300 ppm. We provide a concise brief, and explicit representation of the greenhouse effect of the Earth’s atmosphere. We find an equilibrium climate sensitivity (temperature increase ∆T due to doubling of atmospheric CO2 concentration) of ∆T ~ 0.5°C. We elaborate on the consistency of results on ∆T with results observationally obtained by satellite-based measurements of short-time radiation-flux versus surface-temperature changes.”
The last sentence notes how the author validated his calculations with scientific observations. That's the so-called scientific method.
The paper explains that the author Schack, referenced above, “an expert on heat transfer in combustion devices, in 1923 had discovered the role played by the interaction of infrared electromagnetic radiation with carbon dioxide, CO2, and water vapor, H2O, in such devices.” In other words, the same German physicist who discovered the greenhouse effect a century ago, argued half a century ago that the greenhouse effect by CO2 is saturated above an atmospheric concentration of 300 ppm. (It is now above 400 ppm.) I’ve found at least three more papers, other than this paper and Schack (1972), that concur and improve on the calculations and comparison with satellite measurements. To my knowledge, the saturation of the greenhouse effect has not been refuted by other physicists, only refined over time.
Some climate scientists claim that the small future ∆T of the greenhouse effect triggers a larger ∆T effect caused by thermodynamic feedback in the atmosphere. Numerous climate models have used feedback theory to predict significantly larger equilibrium climate sensitivity (∆T). However, they have not validated their predictions with scientific observations. Many model predictions, compared to reality, have generally proved to predict significantly higher temperatures than Earth actually experienced over the short term (e.g., 1972 to 2000).
Unlike reliable radiative transfer calculations, climate models rely on parameters that are tuned to describe processes that occur on sub-grid scale such as condensation, precipitation and convection. The vast majority of climate models produce significantly more warming over the historic period and exhibit climate sensitivity to rising GHGs that are too high. Lewis and Curry (2018) calculate an ECS of 1.7 K (1.2-2.7K 90% ci). Consequently, in AR6 WG1, the authors of the chapter on climate sensitivity officially abandoned the use of climate models for estimating climate sensitivity.
Nevertheless, the no-feedbacks warming calculated using forcing from radiation transfer calculations is amplified by water vapor, lapse-rate and cloud feedbacks: Our planet does not behave like a simple gray body. This can best be seen in my favorite paper, Tsushima and Manage (2013).
Due to the asymmetric distribution of land on our planet, global mean surface temperature rises and falls about 3.5 degC every year. For decades, we have been monitoring from space the effect of this warming on the emission of LWR and the reflection of SWR. These observations can be compared with the predictions of climate models. Figure 1B shows that emission of LWR through clear skies increases with warming only about 2.2 W/m2/K, far less than the 3.3 W/m2/K expected for a gray body at 288. This agrees well the predictions of models about the combined water vapor+lapse rate LWR feedback of climate models (the only feedback operating in clear skies). However, models predict positive feedback from cloudy skies while satellites observe a small negative feedback. Models also disagree seriously with each other and observations about SWR feedbacks (which aren't linear with temperature). (Linden and Choi reported similar issues with SWR feedbacks.) Seasonal warming is the result of warming in the NH and cooling in the SH and therefore is different from "global warming", which is least in the tropics and greatest in the Arctic. Linden and Choi were trying to calculate feedbacks from much smaller temperature changes associate with strong El Nino and La Nina events, which aren't "global warming" either. Nevertheless, if climate models can't properly reproduce the feedbacks associated with seasonal warming, they can't be trusted to predict global warming.
Absorption by CO2 is "nearly saturated", but Figure 2 in Schildknecht's paper shows absorption is not saturated on shoulders of the main band. He calculates that the reduction in radiative flux to space upon raising CO2 from 300 to 600 ppm is 2.6 W/m2 (Table 6) BECAUSE absorption isn't saturated. Climate scientists call the slowdown in radiative cooling to space caused by an increase in CO2 (or other GHGs) "radiative forcing". It has been known for decades that most of the radiative forcing from a doubling of CO2 comes from shoulders of the main CO2 band where absorption IS NOT SATURATED. There is nothing new here.
For decades, we have had software packages for doing line-by-line or broadband radiative transfer calculations using Schwarzschild's equation for radiative transfer that are far more sophisticated than the crude EXCEL spreadsheets used by Schildknecht. The best estimate is that globally an instantaneous doubling of CO2 would reduce radiative cooling to space by about 3.6 W/m2, similar to what Schildknecht reports. Even you and I have the ability to do much more realistic broadband or LBL radiative transfer calculations than Schildknecht's with a variety of GHG concentrations, latitudes, humidities, altitudes, CLOUDS, etc. including at the website linked below. Note that as one repeatedly doubles or halves the concentration of CO2, the center of the main band saturates with as little as 50 ppm, but the band gets fatter and fatter up to and past 1000 ppm. Also note that MODTRAN is not a climate model, it is software for performing radiative transfer calculations.
Conservation of energy demands that a slowdown in radiative cooling to space result in planetary warming until a balance is restored between incoming and outgoing radiation. Schildknecht calculates that will require 0.5 degC of warming in Section 3 of his paper, but mistakenly assumes that our planet behaves as "Planck radiator" or blackbody at 293 K. A blackbody at 293 K would radiate 418 W/m2 to space, not the 240 W/m2 we receive from the sun. In Equation 3.3, Schildknecht needed to include an emissivity of 0.57 for a gray body at 293 K. For a gray body in equilibrium with incoming solar radiation (S), S = eoT^4 and dS/dT = 4eoT^3 = 3.3 W/m2/K. For Schildknecht's radiative forcing for doubled CO2 of 2.6 W/m2 gives a warming of 0.79 K. The consensus estimate of 3.6 W/m2 gives the consensus result of 1.1 K for the no-feedbacks warming associated with a doubling of CO2. Therefore, with this correction, Schack is within reasonable agreement with the consensus on the no-feedbacks warming associated with a doubling of CO2. THERE IS NOTHING NEW HERE EITHER, except a poorly refereed paper missing references to consensus estimates.
Water vapor feedback more than doubles the radiative forcing from doubled CO2. If you go to the MODTRAN link and add a temperature offset of 1.1 degC holding relative humidity fixed, you will see that the increase in water vapor associated with 1.1 degC of no-feedbacks warming increases radiative forcing by another 3 W/m2. This produces more warming, more water vapor, amplification, and total warming much higher than the no-feedbacks warming of 1.1 degC.
Roger, the NZ situation is much worse than you have described. The Ministry for the Environment publishes "guidance" (https://environment.govt.nz/publications/coastal-hazards-and-climate-change-guidance/) which, in effect, local councils follow in setting rules for building and land use. By law, councils "must have regard to" this guidance: in principle, they can then set it aside and use better information, but in practice the only legally safe approach is to adopt it. The guidance references SSP5-8.5/RCP8.5 but, for some purposes, uses the 83rd percentile (nearly the top end) of 8.5 rather than the mid-point. This is justified as being "a plausible upper range for RSLR to reflect the deep uncertainties associated with changes to future sea level."
The Ministry is largely staffed by true believers that the world is heading for climate catastrophe. After all, why would anyone who thinks that climate change is real but manageable want a job in such a unit? So this "guidance" will not be rescinded any time soon, even though the politicians are finally having second thoughts, and council rules will not be updated for years after that.
And the insurance companies love it, and have been very much in cahoots with the regulators. The insurance premiums for my near-beachfront home went up 83% from 2023 to 2025, mostly driven by increased estimated risk of coastal inundation later this century (even though the policy covers only the coming year). The two home insurance groups have posted huge profit increases recently; if any reader runs an insurance business, consider opening a branch in NZ - you could make a killing, and we could use the competition.
Cutting edge and timely analysis, Roger. One quibble though. Despite Van Vuuren (2011) and Richard Moss's admonition, the seeds of confusion were planted early.
Riahi et al. (2011) [https://www.researchgate.net/publication/226624305_RCP_85-A_scenario_of_comparatively_high_greenhouse_gas_emissions] is also a seminal RCP8.5 study. Although the authors do not call RCP8.5 "the" baseline scenario, they repeatedly refer to it as "a" baseline — a term they never use in connection with RCPs 2.6, 4.5, or 6.0. They describe RCPs as a "set of greenhouse gas concentration and emissions pathways designed to support research on impacts and potential policy responses to climate change," citing Moss et al. 2010 and van Vuuren et al. 2011a). Riahi et al. describe RCP8.5 as "a baseline scenario with no explicit climate policy, representing the highest RCP scenario in terms of GHG emissions." They never describe RCPs 4.5 or 6.0 as having "no explicit climate policy." The most natural inference is that RCPs 2.6, 4.5, and 6.0 are "potential policy responses to climate change," and RCP8.5 is what happens without "policy responses."
Only two years later, IPCC AR5 similarly misleads readers. The analysis is structured around four RCPs: “one mitigation scenario leading to a very low forcing level (RCP2.6), two stabilization scenarios (RCP4.5 and RCP6), and one scenario with very high greenhouse gas emissions (RCP8.5)” (SPM, p. 29). Ever since the UN Framework Convention on Climate Change (UNFCCC), "stabilization" of greenhouse gas concentrations has been a core objective of international climate policy. The most natural inference, again, is that RCPs 2.6, 4.5, and 6.0 are policy scenarios and RCP8.5 is what likely results when governments do not implement climate policy scenarios.
"These residents are experiencing the unintended consequences of the use of a scenario that scientists built originally for exploratory earth system modeling to inform global climate negotiations turning up in the price of their homes."
I'm not sure these consequences were "unintended". Roger is likely being quite generous in giving the benefit of the doubt to all involved. The more I read about this, the greater my suspicion that this was done on purpose because it was seen as politically useful. The examples you highlight only reinforce this.
I concur, Epaminondas. Note, there are legitimate analytic uses for extreme forcing scenarios. They may reveal potential climate risks not discernible when models are run with realistic forcing trajectories. Alternatively, if models forced with RCP8.5 do not show significant changes in, e.g., tropical cyclones, fire weather, and river floods by 2100 (see https://rogerpielkejr.substack.com/p/what-the-ipcc-actually-says-about), scientists should be skeptical of studies claiming to find such effects at today's much lower forcing levels.
Nonetheless, the propaganda value of misconstruing a high-end, no-policy forcing trajectory as a business-as-usual baseline is too obvious to have escaped the notice of advocacy scientists. That deliberate confusion, for example, was central to EPA's effort to sell policymakers and the public on the Paris Agreement (https://cei.org/blog/rcp8-5-climate-establishment-officially-retires-extreme-scenario-part-ii/).
"The way that I normally use these scenarios is in climate negotiations. It is quite interesting that even these rather abstract scenarios have such consequences as well in daily decisions . . ."
Yeah, right - NOW they are 'abstract', but before the light started hitting these stupidities, they were "oh my god - we're all going to die - next week!". They deliberately created this monstrosity, knowing it would be trumpeted by the complicit media, and then later denied that they knew it would cause real-world harms. I cannot put into words how evil these people have become, all under the guise of 'science'.
"The mistakes made in New Zealand in using RCP8.5 as a scenario depicting an expected future, a forecast even, is understandable as a cascade of confusion and conflicting intent for the role of scenarios in climate research."
They weren't mistakes - they were deliberate efforts to punish New Zealanders for having the audacity to want nice things. Just another "I can be more evil than you can" virtue signaling by 'climate change' activists
"they were "oh my god - we're all going to die - next week!"'
This is a dishonest fabrication unless, by "they" you mean fringe groups whose views have never been particularly influential.
The actual argument promoted by influential people and organizations has been that we may need to take action today to avoid severe consequences much further into the future. That's a very different claim.
"oh my god - we're all going to die - next week!".
<--- That's the view of a few fringe voices. It's not what mainstream climate science has been telling the world. Not even RCP8.5 tells that story.
If you want to oppose the view that we should take pre-cautionary action because it takes too long to adjust in the events that the risks fully materialize, then do so.
Just cut out all the inflammatory and intellectually dishonest "next week" stuff.
“tens of thousands of papers have been published that pair RCP8.5 as a reference scenario with the other RCPs”.
I’m just curious how many thousands of papers have been published based on a “confusion” that made climate change look less bad, as opposed to worse. Maybe… zero? Pure coincidence, I’m sure.
Also interesting if diminishing the value of homes and raising insurance premiums based on the same “confusion” is just an honest mistake or a deliberate strategy. I suppose when you discover that “climate change” burns your pocket, you become more willing to accept high mitigation costs.
"Oh what a tangled web we weave, when first we practice to deceive!"
This ongoing unravelling of "Scenario-gate" may well lead to some future class action lawsuits if material losses can be proven. While VV states RCP8.5 should never have been used the way it has happended, perhaps it is fair to ask how often he warned the climate community of that since 2011?
Also, I think structurally modeling the future produces infinite numbers of journal articles and is pretty much non-falsifiable., while measuring things in the real world takes time and effort (say monitoring over time) and the real world and people can behave in surprising and unpredictable ways…so is there a structural bias in various science communities toward modeling over observing? Economists do this all the time, but as a community they seem to have both skepticism and some humility about projections. Is the climate modeling community somehow culturally different? And why?
In order to have skepticism and humility about projections, you have to have skepticism and humility about the subject matter. Economists get whacked all the time with economic data that challenges their belief system. Most climate scientists are on a crusade, and they KNOW that they are on the right side of history, so they have no such thing as feelings of skepticism and humility.
There might be some economists who don't have skepticism or humility, but I think they are all clustered in a particular area of the field which fails every time it has been tried, but they won't accept those failures as anything other than the need to try it once more, using the right tools and methods.
Like you said, there are subfields of economics that can be different... like the folks who calculated the social cost of carbon.. there is other ecological economics kinds of work that seems to be focused on "if we value the environment properly it will cause people to change policies." Of course, some of these calculations are unprovable, and the timeframes of the predictions long. Perhaps humility has a positive correlation with the timeframe when predictions can be proven wrong. I'm thinking of polling and elections for the political scientists.
Make or declare the most desirable properties around the world unlivable, then buy them up pennies on the dollar—a 20yr global recipe, Blackrock and State Street style
Agreed that climate change scenario RCP8.5 is indefensible. One concern is that this acknowledgement will be used as "fuel" to undermine the seriousness of climate change (Trump has already done this). Now that we haved a climate change skeptic designated to head the National Climate Assessment (Dr. Matthew Wielicki), I suspect that all sorts of distoration about the seriouness of cliamte change will be brought into question. This brings me to my request for a future Honest Broker contribution--a thorough assessment of Dr. Wielicki's qualifications.
"I suspect that all sorts of distoration about the seriouness of cliamte change will be brought into question"
Brought into question a couple of decades ago.
Fortunately, I’ve got a long history of writing here about problems with the NCA
The issues here are not Weilicki or any of his predecessors but the entire structure behind the effort
That said, your comment makes me think about doing a post titled: Why I won’t participate in the US NCA
Fun fact: I wrote my PhD dissertation on the legislation that created the NCA, so I probably know too much 😎
Thank you for your response. I would appreciate hearing your reasons for not chosing to participate in the NCA.
Roger thank you for this - I’m a farmer in New Zealand and climate change policy or should I say global warming alarmism influenced policy is affecting animal farming in 2 main ways: Firstly the very real problem of nitrate & phosphate leaching into waterways from our basically pasture based production systems conflated with RCP8.5 global warming scenarios is causing forecasts which are basically saying animal production will have to cease over large areas to get NO3 & phosphate leaching down to a sustainable level. If better future scenarios are used then actual practical solutions can be found for the leaching. Secondly NZ joined other first world countries at Kyoto and said it count biogenic methane emissions in its emissions inventory. This was always nonsensical and subsequent studies have shown the carbon cycle of CO2 in the atmosphere used in plant photosynthesis eaten by ruminant animals where some of the carbon eaten is emitted as methane which over around 10 yrs breaks down to CO2 which is used again in the plant photosynthetic process. It has been shown that if animal numbers are stable actual warming from the methane emissions is negligible. Some policy makers still want to tax animal methane emissions which is absolutely counter to increasing NZers economic wellbeing.
I’m not a farmer but I am well aware just how much farming contributes to the economy and while there are endless debates about how to improve our productivity, many farmers are highly innovative as can be seen by the success of firms like Halter and Gallacher.
Frank: Yes, nothing new. Part of the point that I made is that physicists have known about saturation for decades, and, as you've acknowledged, it isn't controversial. Yet that fact is being ignored by policymakers.
The 3.6 W/m2 of radiative cooling to space you noted is about 1.3% of the current total cooling average of about 277 W/m2. That's not completely saturated, but very nearly so after doubling atmospheric CO2 from about 400 ppm to 800 ppm. A tiny output for a massive input. The effect of doubling CO2 again after that will be even smaller as the effect of adding CO2 approaches an asymptotic limit. Conversely, if you remove half the atmospheric CO2, the cooling effect would be much, much larger. So it is quite reasonable for Schildknecht to call that effect saturation.
As for the Modtran prediction you cited, I don't believe that the Modtran model has been validated by the scientific method, i.e., matching Modtran predictions to actual observations. And, the forecast you mentioned seems to be contradicted by the comparative observations cited by Schildknecht. The consensus you cited has its uses, but it must never be allowed to trump the scientific method.
Here’s another model forecast. The MAGICC climate model is widely used for climate policy analysis, the EPA, and IPCC reports. MIT Prof. Richard Lindzen reported that if the U.S. reduced CO2 and other GHG emissions to net zero effective immediately, rather than waiting until 2050, the MAGICC model predicts the cooling effect on global temperatures would only be 0.17° C (0.31° F). A consensus result, but probably not validated by observation either. Still another reason why policymakers should not be using ANY speculative emissions scenarios to wield the force of government against a mostly free people.
I don't trust the stats being used, by the climate pro's.
Watching Wimbledon... 'the weather' had me curious.
Yesterday London 110 F 27% humidity
Yesterday 17F variance
Brentford, England (~30 miles west of London
93 F, 25% humidity
Flipped today;
Today London 84 F
Today Brentford 92 F
Temp stations on airport tarmac's, in big city centers..... Generally doesn't match the ~80% of rural weather.... Although today's flip, is odd.
Excellent summary. Thanks for bringing the NZ example that has essentially been replicated worldwide. And with similar damaging results.
One comment caught my eye - “Along the way, as mistakes were made, no one spoke up or pointed out the unfolding errors of scenario design and application.” I disagree with this. Those who brought up these mistakes were shouted down, excoriated and some drummed out of their professions.
I’m not sure which is worse - those who knew the flaws in this extreme scenario and pushed it anyway, or those who really believed it. All the while, ignoring the damage being done.
Good point! I was imprecise — no one *within the official scenario development community*
Roger: In the case of SLR, projected differences between scenarios are relatively small.
SSP2-4.5: +0.20m (0.17-0.26) by 2050 relative to 1995-2014 (likely range)
SSP5-8.5: +0.24m (0.20-0.40) by 2050
a difference of 4 cm (1.6 inches) by 2050
SSP2-4.5: +0.56m (0.44-0.76) by 2100
SSP5-8.5: +0.88m (0.63-1.60) by 2100
a difference of 32 cm (about a foot) by 2100
https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-9/#9.6
I like to think about sea level rise in terms of more tangible units of inches/decade. Today SLR is a little above 1 inch/decade and supposedly accelerating at about 1/3 inch/decade/decade. For the next few decades, SLR will be negligible compared with tides (a rise of about 1 m twice a day) and storm surges (another 1 m except during the strongest hurricanes). IMO, we will be facing only modest increases in danger for the next several decades. The problem is that some infrastructure is already in significant danger from past mistakes. The tidal basin and mall in Washington DC were built a century ago on fill that has settled two feet while while SLR. That fill buried a creek near the African American Smithsonian museum. Upwelling of water from underground causes flooding in many places in DC.
https://www.washingtonpost.com/climate-environment/interactive/2023/dc-low-lying-city-flood-risks/
And all scenarios and projections assume X co2 produces Y temperature.
Just another flawed assumption that I’m not buying.
There are no accidents.
Speculation about future CO2 emission scenarios should not be a serious concern to policymakers. Physicists who specialize in radiative heat transfer in the atmosphere have long known that the greenhouse effect is effectively saturated above modern levels of atmospheric concentration.
The following is the opening paragraph from a paper entitled, “Saturation of the infrared absorption by carbon dioxide in the atmosphere,” International Journal of Modern Physics B Vol. 34 - 28 October 2020; Author: Physics Professor D. Schildknecht, Universität Bielefeld
“Based on new radiative transfer numerical evaluations, we reconsider an argument presented by Schack in 1972 that says that saturation of the absorption of infrared radiation by carbon dioxide in the atmosphere sets in as soon as the relative concentration of carbon dioxide exceeds a lower limit of approximately 300 ppm. We provide a concise brief, and explicit representation of the greenhouse effect of the Earth’s atmosphere. We find an equilibrium climate sensitivity (temperature increase ∆T due to doubling of atmospheric CO2 concentration) of ∆T ~ 0.5°C. We elaborate on the consistency of results on ∆T with results observationally obtained by satellite-based measurements of short-time radiation-flux versus surface-temperature changes.”
The last sentence notes how the author validated his calculations with scientific observations. That's the so-called scientific method.
The paper explains that the author Schack, referenced above, “an expert on heat transfer in combustion devices, in 1923 had discovered the role played by the interaction of infrared electromagnetic radiation with carbon dioxide, CO2, and water vapor, H2O, in such devices.” In other words, the same German physicist who discovered the greenhouse effect a century ago, argued half a century ago that the greenhouse effect by CO2 is saturated above an atmospheric concentration of 300 ppm. (It is now above 400 ppm.) I’ve found at least three more papers, other than this paper and Schack (1972), that concur and improve on the calculations and comparison with satellite measurements. To my knowledge, the saturation of the greenhouse effect has not been refuted by other physicists, only refined over time.
Some climate scientists claim that the small future ∆T of the greenhouse effect triggers a larger ∆T effect caused by thermodynamic feedback in the atmosphere. Numerous climate models have used feedback theory to predict significantly larger equilibrium climate sensitivity (∆T). However, they have not validated their predictions with scientific observations. Many model predictions, compared to reality, have generally proved to predict significantly higher temperatures than Earth actually experienced over the short term (e.g., 1972 to 2000).
Unlike reliable radiative transfer calculations, climate models rely on parameters that are tuned to describe processes that occur on sub-grid scale such as condensation, precipitation and convection. The vast majority of climate models produce significantly more warming over the historic period and exhibit climate sensitivity to rising GHGs that are too high. Lewis and Curry (2018) calculate an ECS of 1.7 K (1.2-2.7K 90% ci). Consequently, in AR6 WG1, the authors of the chapter on climate sensitivity officially abandoned the use of climate models for estimating climate sensitivity.
https://nicholaslewis.org/wp-content/uploads/2018/07/LewisCurry_The-impact-of-recent-forcing-and-ocean-heat-uptake-data-on-estimates-of-climate-sensitivity_JCli2018.pdf
Nevertheless, the no-feedbacks warming calculated using forcing from radiation transfer calculations is amplified by water vapor, lapse-rate and cloud feedbacks: Our planet does not behave like a simple gray body. This can best be seen in my favorite paper, Tsushima and Manage (2013).
https://www.pnas.org/doi/pdf/10.1073/pnas.1216174110
Due to the asymmetric distribution of land on our planet, global mean surface temperature rises and falls about 3.5 degC every year. For decades, we have been monitoring from space the effect of this warming on the emission of LWR and the reflection of SWR. These observations can be compared with the predictions of climate models. Figure 1B shows that emission of LWR through clear skies increases with warming only about 2.2 W/m2/K, far less than the 3.3 W/m2/K expected for a gray body at 288. This agrees well the predictions of models about the combined water vapor+lapse rate LWR feedback of climate models (the only feedback operating in clear skies). However, models predict positive feedback from cloudy skies while satellites observe a small negative feedback. Models also disagree seriously with each other and observations about SWR feedbacks (which aren't linear with temperature). (Linden and Choi reported similar issues with SWR feedbacks.) Seasonal warming is the result of warming in the NH and cooling in the SH and therefore is different from "global warming", which is least in the tropics and greatest in the Arctic. Linden and Choi were trying to calculate feedbacks from much smaller temperature changes associate with strong El Nino and La Nina events, which aren't "global warming" either. Nevertheless, if climate models can't properly reproduce the feedbacks associated with seasonal warming, they can't be trusted to predict global warming.
Richard: Schildknecht's radiative transfer calculations haven't described anything new.
https://arxiv.org/pdf/2004.00708
Absorption by CO2 is "nearly saturated", but Figure 2 in Schildknecht's paper shows absorption is not saturated on shoulders of the main band. He calculates that the reduction in radiative flux to space upon raising CO2 from 300 to 600 ppm is 2.6 W/m2 (Table 6) BECAUSE absorption isn't saturated. Climate scientists call the slowdown in radiative cooling to space caused by an increase in CO2 (or other GHGs) "radiative forcing". It has been known for decades that most of the radiative forcing from a doubling of CO2 comes from shoulders of the main CO2 band where absorption IS NOT SATURATED. There is nothing new here.
For decades, we have had software packages for doing line-by-line or broadband radiative transfer calculations using Schwarzschild's equation for radiative transfer that are far more sophisticated than the crude EXCEL spreadsheets used by Schildknecht. The best estimate is that globally an instantaneous doubling of CO2 would reduce radiative cooling to space by about 3.6 W/m2, similar to what Schildknecht reports. Even you and I have the ability to do much more realistic broadband or LBL radiative transfer calculations than Schildknecht's with a variety of GHG concentrations, latitudes, humidities, altitudes, CLOUDS, etc. including at the website linked below. Note that as one repeatedly doubles or halves the concentration of CO2, the center of the main band saturates with as little as 50 ppm, but the band gets fatter and fatter up to and past 1000 ppm. Also note that MODTRAN is not a climate model, it is software for performing radiative transfer calculations.
https://climatemodels.uchicago.edu/modtran/
Conservation of energy demands that a slowdown in radiative cooling to space result in planetary warming until a balance is restored between incoming and outgoing radiation. Schildknecht calculates that will require 0.5 degC of warming in Section 3 of his paper, but mistakenly assumes that our planet behaves as "Planck radiator" or blackbody at 293 K. A blackbody at 293 K would radiate 418 W/m2 to space, not the 240 W/m2 we receive from the sun. In Equation 3.3, Schildknecht needed to include an emissivity of 0.57 for a gray body at 293 K. For a gray body in equilibrium with incoming solar radiation (S), S = eoT^4 and dS/dT = 4eoT^3 = 3.3 W/m2/K. For Schildknecht's radiative forcing for doubled CO2 of 2.6 W/m2 gives a warming of 0.79 K. The consensus estimate of 3.6 W/m2 gives the consensus result of 1.1 K for the no-feedbacks warming associated with a doubling of CO2. Therefore, with this correction, Schack is within reasonable agreement with the consensus on the no-feedbacks warming associated with a doubling of CO2. THERE IS NOTHING NEW HERE EITHER, except a poorly refereed paper missing references to consensus estimates.
Water vapor feedback more than doubles the radiative forcing from doubled CO2. If you go to the MODTRAN link and add a temperature offset of 1.1 degC holding relative humidity fixed, you will see that the increase in water vapor associated with 1.1 degC of no-feedbacks warming increases radiative forcing by another 3 W/m2. This produces more warming, more water vapor, amplification, and total warming much higher than the no-feedbacks warming of 1.1 degC.
Roger, the NZ situation is much worse than you have described. The Ministry for the Environment publishes "guidance" (https://environment.govt.nz/publications/coastal-hazards-and-climate-change-guidance/) which, in effect, local councils follow in setting rules for building and land use. By law, councils "must have regard to" this guidance: in principle, they can then set it aside and use better information, but in practice the only legally safe approach is to adopt it. The guidance references SSP5-8.5/RCP8.5 but, for some purposes, uses the 83rd percentile (nearly the top end) of 8.5 rather than the mid-point. This is justified as being "a plausible upper range for RSLR to reflect the deep uncertainties associated with changes to future sea level."
The Ministry is largely staffed by true believers that the world is heading for climate catastrophe. After all, why would anyone who thinks that climate change is real but manageable want a job in such a unit? So this "guidance" will not be rescinded any time soon, even though the politicians are finally having second thoughts, and council rules will not be updated for years after that.
And the insurance companies love it, and have been very much in cahoots with the regulators. The insurance premiums for my near-beachfront home went up 83% from 2023 to 2025, mostly driven by increased estimated risk of coastal inundation later this century (even though the policy covers only the coming year). The two home insurance groups have posted huge profit increases recently; if any reader runs an insurance business, consider opening a branch in NZ - you could make a killing, and we could use the competition.
HEADS UP - National Academies webinar "Attribution of Extreme Weather and Climate Events and their Impacts Report Release Webinar" is next Thursday 16 July 1-2 EDT. You can register to attend here - https://events.nationalacademies.org/47024?utm_campaign=34319986-CHPP%20Events&utm_medium=email&_hsmi=427322972&utm_content=427322972&utm_source=hs_email
Or see the NAS web site
Cutting edge and timely analysis, Roger. One quibble though. Despite Van Vuuren (2011) and Richard Moss's admonition, the seeds of confusion were planted early.
Riahi et al. (2011) [https://www.researchgate.net/publication/226624305_RCP_85-A_scenario_of_comparatively_high_greenhouse_gas_emissions] is also a seminal RCP8.5 study. Although the authors do not call RCP8.5 "the" baseline scenario, they repeatedly refer to it as "a" baseline — a term they never use in connection with RCPs 2.6, 4.5, or 6.0. They describe RCPs as a "set of greenhouse gas concentration and emissions pathways designed to support research on impacts and potential policy responses to climate change," citing Moss et al. 2010 and van Vuuren et al. 2011a). Riahi et al. describe RCP8.5 as "a baseline scenario with no explicit climate policy, representing the highest RCP scenario in terms of GHG emissions." They never describe RCPs 4.5 or 6.0 as having "no explicit climate policy." The most natural inference is that RCPs 2.6, 4.5, and 6.0 are "potential policy responses to climate change," and RCP8.5 is what happens without "policy responses."
Only two years later, IPCC AR5 similarly misleads readers. The analysis is structured around four RCPs: “one mitigation scenario leading to a very low forcing level (RCP2.6), two stabilization scenarios (RCP4.5 and RCP6), and one scenario with very high greenhouse gas emissions (RCP8.5)” (SPM, p. 29). Ever since the UN Framework Convention on Climate Change (UNFCCC), "stabilization" of greenhouse gas concentrations has been a core objective of international climate policy. The most natural inference, again, is that RCPs 2.6, 4.5, and 6.0 are policy scenarios and RCP8.5 is what likely results when governments do not implement climate policy scenarios.
"These residents are experiencing the unintended consequences of the use of a scenario that scientists built originally for exploratory earth system modeling to inform global climate negotiations turning up in the price of their homes."
I'm not sure these consequences were "unintended". Roger is likely being quite generous in giving the benefit of the doubt to all involved. The more I read about this, the greater my suspicion that this was done on purpose because it was seen as politically useful. The examples you highlight only reinforce this.
I concur, Epaminondas. Note, there are legitimate analytic uses for extreme forcing scenarios. They may reveal potential climate risks not discernible when models are run with realistic forcing trajectories. Alternatively, if models forced with RCP8.5 do not show significant changes in, e.g., tropical cyclones, fire weather, and river floods by 2100 (see https://rogerpielkejr.substack.com/p/what-the-ipcc-actually-says-about), scientists should be skeptical of studies claiming to find such effects at today's much lower forcing levels.
Nonetheless, the propaganda value of misconstruing a high-end, no-policy forcing trajectory as a business-as-usual baseline is too obvious to have escaped the notice of advocacy scientists. That deliberate confusion, for example, was central to EPA's effort to sell policymakers and the public on the Paris Agreement (https://cei.org/blog/rcp8-5-climate-establishment-officially-retires-extreme-scenario-part-ii/).
The IPCC's decision to make RCP8.5 the de-facto baseline forcing trajectory is the reason the profession published over 57,000 studies using that scenario (https://scholar.google.com/scholar?hl=en&as_sdt=0%2C9&q=RCP8.5&oq=). That (among other biases -- https://cei.org/blog/rcp8-5-climate-establishment-officially-retires-extreme-scenario-part-i/) produced an alarming "consensus." Without a strongly worded disclaimer repeated as frequently as the mantra that "absence of evidence is not evidence of absence," RCP8.5 abuse was predictable.
"The way that I normally use these scenarios is in climate negotiations. It is quite interesting that even these rather abstract scenarios have such consequences as well in daily decisions . . ."
Yeah, right - NOW they are 'abstract', but before the light started hitting these stupidities, they were "oh my god - we're all going to die - next week!". They deliberately created this monstrosity, knowing it would be trumpeted by the complicit media, and then later denied that they knew it would cause real-world harms. I cannot put into words how evil these people have become, all under the guise of 'science'.
"The mistakes made in New Zealand in using RCP8.5 as a scenario depicting an expected future, a forecast even, is understandable as a cascade of confusion and conflicting intent for the role of scenarios in climate research."
They weren't mistakes - they were deliberate efforts to punish New Zealanders for having the audacity to want nice things. Just another "I can be more evil than you can" virtue signaling by 'climate change' activists
"they were "oh my god - we're all going to die - next week!"'
This is a dishonest fabrication unless, by "they" you mean fringe groups whose views have never been particularly influential.
The actual argument promoted by influential people and organizations has been that we may need to take action today to avoid severe consequences much further into the future. That's a very different claim.
"we may need to take action today to avoid severe consequences much further into the future. "
Thank you for proving my point
Eh. This was your point:
"oh my god - we're all going to die - next week!".
<--- That's the view of a few fringe voices. It's not what mainstream climate science has been telling the world. Not even RCP8.5 tells that story.
If you want to oppose the view that we should take pre-cautionary action because it takes too long to adjust in the events that the risks fully materialize, then do so.
Just cut out all the inflammatory and intellectually dishonest "next week" stuff.
“tens of thousands of papers have been published that pair RCP8.5 as a reference scenario with the other RCPs”.
I’m just curious how many thousands of papers have been published based on a “confusion” that made climate change look less bad, as opposed to worse. Maybe… zero? Pure coincidence, I’m sure.
Also interesting if diminishing the value of homes and raising insurance premiums based on the same “confusion” is just an honest mistake or a deliberate strategy. I suppose when you discover that “climate change” burns your pocket, you become more willing to accept high mitigation costs.
"Oh what a tangled web we weave, when first we practice to deceive!"
This ongoing unravelling of "Scenario-gate" may well lead to some future class action lawsuits if material losses can be proven. While VV states RCP8.5 should never have been used the way it has happended, perhaps it is fair to ask how often he warned the climate community of that since 2011?
Also, I think structurally modeling the future produces infinite numbers of journal articles and is pretty much non-falsifiable., while measuring things in the real world takes time and effort (say monitoring over time) and the real world and people can behave in surprising and unpredictable ways…so is there a structural bias in various science communities toward modeling over observing? Economists do this all the time, but as a community they seem to have both skepticism and some humility about projections. Is the climate modeling community somehow culturally different? And why?
In order to have skepticism and humility about projections, you have to have skepticism and humility about the subject matter. Economists get whacked all the time with economic data that challenges their belief system. Most climate scientists are on a crusade, and they KNOW that they are on the right side of history, so they have no such thing as feelings of skepticism and humility.
There might be some economists who don't have skepticism or humility, but I think they are all clustered in a particular area of the field which fails every time it has been tried, but they won't accept those failures as anything other than the need to try it once more, using the right tools and methods.
Like you said, there are subfields of economics that can be different... like the folks who calculated the social cost of carbon.. there is other ecological economics kinds of work that seems to be focused on "if we value the environment properly it will cause people to change policies." Of course, some of these calculations are unprovable, and the timeframes of the predictions long. Perhaps humility has a positive correlation with the timeframe when predictions can be proven wrong. I'm thinking of polling and elections for the political scientists.
Make or declare the most desirable properties around the world unlivable, then buy them up pennies on the dollar—a 20yr global recipe, Blackrock and State Street style
(LaHaina, downtown SFO, FEMA velocity zones, etc ?)