Skip to content

Press Release: Important new paper challenges IPCC’s claims about climate sensitivity

September 20, 2022

By Paul Homewood




London, 20 September – A new paper reduces the estimate of climate sensitivity – the amount of warming expected for a doubling of carbon dioxide concentrations – by one third. The results therefore suggest that future global warming will be much less than expected.
The paper, by independent scientist Nic Lewis, has just appeared in the journal Climate Dynamics. It is an important challenge to the official view of the Intergovernmental Panel on Climate Change (IPCC).
Lewis has critiqued a 2020 assessment of climate sensitivity by Sherwood et al., which strongly influenced the IPCC’s Sixth Assessment Report, in 2021. Lewis commented:
"It is unfortunate that Sherwood et al.’s assessment of climate sensitivity, which underpinned the UN Framework Convention on Climate Change, contained such serious errors, inconsistencies and deficiencies in its methods".
After correcting the Sherwood et al. methods and revising key input data to reflect, primarily, more recent evidence, the central estimate for climate sensitivity comes down from 3.1°C per doubling of CO2 concentration in the original study to 2.16°C in the new paper.
This large reduction shows how sensitive climate sensitivity estimates still are to input assumptions, and that values between 1.5°C and 2°C remain quite plausible.

  • Climate sensitivity represents the long-term global temperature increase caused by a doubling of atmospheric CO2 concentration. There are different measures of climate sensitivity. Both the Sherwood and Lewis papers estimate the so-called ‘effective’ climate sensitivity, which reflects a new equilibrium state projected from centennial changes after a doubling of the CO2 concentration. This measure is considered the most relevant one for predicting climate change in the coming two centuries.
  • Climate sensitivity has always been a very important, but also highly uncertain, parameter in the climate change discourse. Earlier IPCC reports assessed its value as likely to be somewhere between 1.5°C and 4.5°C, with a best estimate of 3°C. However, prompted by the Sherwood paper, the 2021 Sixth Assessment Report moved that range upwards, to 2.5 to 4°C. Although for outsiders this might sound boring, for insiders it was a revolutionary change.
  • Lewis’s corrections and revisions lead to a likely range of 1.75 to 2.7°C, which is not only lower but is also much less uncertain than either the 2021 official IPCC assessment or the very similar Sherwood et al. estimate (2.6 to 3.9°C).
  • Nic Lewis is the lead or sole author of ten peer-reviewed papers on climate sensitivity. He was a participant in the 2015 workshop that kicked off the World Climate Research Programme project that led to the Sherwood et al. 2020 paper, but he was not a co-author of that paper.

Lewis commented:
"The substantial reduction in assessed climate sensitivity upon updating key input data suggests that the increase in the bottom of the climate sensitivity range in the IPCC Sixth Assessment Report was unjustified".
Lewis’s paper is entitled ‘Objectively combining climate sensitivity evidence’. It can be freely downloaded
here. A detailed explanatory article about the paper is available here.

  1. HotScot permalink
    September 20, 2022 12:17 pm

    Lies, errors and omissions don’t matter to the left.

  2. David Coe permalink
    September 20, 2022 12:35 pm

    Not once in either of these papers is the infra-red absorption capabilities of so-called greenhouse gases mentioned. They are after all, supposedly, the key factors and cause of climate change. When the absorption spectra of CO2 and H2O are determined from the HITRAN spectral data base and used to calculate the atmospheric IR absorption it is abundantly clear that CO2 has little impact for two reasons. 1 – Its absorption spectrum is already strongly saturated leaving very little room for further effect. 2- Its spectrum is strongly overlapped by H2O which possesses a much wider and stronger spectrum due to its much higher atmospheric concentration. The data for this can be obtained from the paper “The Impact of CO2 and H2O and Other Greenhouse Gases on Equilibrium Earth Temperatures” at

    And yes I am plugging my own paper, but I have yet to see a clearer explanation for the stupidity and corruption of so called climate science. If I am wrong would someone please point out how and why.

    • bobn permalink
      September 20, 2022 2:03 pm

      Prof Happer agrees with you. Need to dig out his paper but think he estimated (and these things are all estimates and theoretical – none proven) about 1c for a doubling of CO2.
      The paper recently published here on NotAlot oPKT states CO2 in any quantity has a minimal effect
      The scientific ‘consensus’ would seem to be that CO2s influence on climate is so small its not measurable in the real world (only in computer games).

    • Jordan permalink
      September 20, 2022 5:14 pm

      David – to my understanding, the points you are examining are reasonably “settled” in terms of the theory. Higher levels of Climate Sensitivity are not attributed to CO2. Instead the theory of MMGW has to jump a couple of additional levels of abstraction by proposing certain positive feedbacks which supposedly amplify the proposed surface warming effect of CO2.
      To call this a scientific proposition, the whole thing needs to yield to a test which is capable of confirming or refuting these processes, and the better tests should have an element of uniqueness (not open to alternative explanations) and should get down to some degree of detail (not testing some vague aggregate measure which lacks meaning).
      In my view, the best test of MMGW by CO2 is the model prediction of the so-called tropospheric hotspot. This is a pattern of warming which seems to be a feature of all models with a Climate Sensitivity to CO2.
      A test which can refute or confirm whether or not this pattern of warming occurs in the real atmosphere should be an area of scientific interest. And yes, it has been for some time. Various researchers went looking for this pattern, starting around the mid-1990’s. They failed to observe it. They collected more data over decades, they debated vigorously among themselves (competing research groups), but the result stays the same: the pattern is not observed. With the best observations we have today, and following decades of research activity, the MMGW idea is falsified by data.
      It is this which convinces me that the idea of MMGW (by CO2) is a dud. (If new data confirms this pattern of warming, then I will revisit my position.)
      Examining absorption of IR is a nice theoretical exercise, but it has little or no practical purpose in terms of the dynamics of the real atmosphere.

      • Philip Mulholland permalink
        September 20, 2022 6:10 pm

        @David, @Bobn @Jordan.
        Here is another proposition for you all to consider.
        The Greenhouse Effect is due to the action of the Hadley Cell and this action is hiding in plain sight.
        The Application of the Dynamic Atmosphere Energy Transport Climate Model (DAET) to Earth’s semi-opaque troposphere

      • David Coe permalink
        September 20, 2022 6:23 pm

        IR absorption is not just a theoretical exercise, it is at the core of the so called greenhouse effect. If CO2 is incapable of absorbing sufficient further energy warm the earth, it doesn’t matter how many wonderful theories are proposed, the concept of global warming is dead in the water. The IR spectra analysis also shows that the positive feedback due to H2O has minimal effect. At least this is a theory that is easily checked and replicated.

    • norman paul weldon permalink
      September 21, 2022 9:04 pm

      My understanding of absorption spectra being saturated is that this is so at the top of the atmosphere. Maybe at this altitude the added greenhouse gases make no significant difference, but nevertheless the absorption and re-emission becomes more concentrated near the Earth’s surface and that is where the temperature of the atmosphere is significant. If I am correct in my interpretation of the result of the mechanisms involved, does that not mean that you are correct, whilst at the same time the surface temperature rise being caused by greenhouse gases is also correct?

      • David Coe permalink
        September 21, 2022 9:31 pm

        H2O and CO2 are the dominant greenhouse gases. Because of the strength of the absorption spectra most of the radiation absorption occurs in the lower 5000m of the atmosphere. Beyond that point the radiation in the CO2 and H2O absorption bands has been absorbed and reduced to almost zero. Little further absorption can occur. This can be seen in Figure 7 of the paper referred to. Conversely the energy reradiated outwards by the lower atmosphere gets a relatively free pass through the rarefied upper atmosphere through to space. The earth temperature is a function of the radiation equilibrium at the top of the atmosphere.

      • norman paul weldon permalink
        September 23, 2022 7:33 am

        Thanks for your reply, David.
        You have, however, missed my point, probably because I was not clear enough. It is not the balance at the top of the atmosphere I am referring to, it is the distribution of the heat/energy within the atmosphere. With an increase in greenhouse gases, absorption and re-emission takes place closer to the Earth’s surface, the result being warmer surface temperatures and a cooling upper troposphere/stratosphere, both of which are being recorded.
        An excellent example in the ‘real’ world is to note how with clear skies and a windless night, temperatures drop much more sharply during the nighttime when the relative humidity is low. We have excellent examples here on the Latvian coast between Baltic Sea sourced air and that which is derived from Central Russia. With water vapor being the dominant greenhouse gas, the temperature drop will only be a few degrees from the former, but up to 20 degrees from the latter.

      • catweazle666 permalink
        September 23, 2022 3:28 pm

        A old post of mine from elsewhere may be slightly relevant:

        A couple of simple observations are sufficient to debunk the CO2-produced AGW hoax.
        Take two locations in the Equatorial region, one in – say – the Sahara Desert and one in the Amazon rain forest.

        The atmospheric CO2 concentrations between the two will vary only slightly but there will be a very considerable difference in the atmospheric water vapour, so if the CO2 concentration is the primary driver of heat retention in the atmosphere there should be little or no variation between the day time and night time temperatures in the two locations.

        So now let us examine the diurnal temperature variation – day time versus night time – between the two different locations:For the desert, NASA gives a variation of an average of 38°C (day), average of -3.9°C (night), giving a diurnal range of ~42°C.

        For the rainforest, from the site:

        we find: “Diurnal patterns (not seasonal); up to 2.8 C daily temperature range (sometimes greater than seasonal change!)”

        Other estimates from other sources of the respective temperatures agree almost exactly with the above, so it is very clear indeed that compared to water vapour the effect of atmospheric CO2 on the temperature of the surface of the planet is negligible.

      • norman paul weldon permalink
        September 24, 2022 7:24 am

        ‘A couple of simple observations are sufficient to debunk the CO2-produced AGW hoax.
        Take two locations in the Equatorial region, one in – say – the Sahara Desert and one in the Amazon rain forest.’

        The comparison you give is flawed by the complication that there are 2 canopies involved: The forest canopy and the cloud canopy restrict both increase in temperature during the daytime and heat loss at night.

  3. Thomas Carr permalink
    September 20, 2022 12:39 pm

    Off topic, somewhat:
    BBC 4 are now serialising a book at 00.30 hrs and 09.45hrs on their one sided favourite topic of global warming. . What is the word for incorrigible x 2 ?

    • September 21, 2022 12:19 pm

      The word is “desperate”.

    • Jules permalink
      September 21, 2022 12:43 pm

      Seems very odd they are banging on about fens as carbon sinks. Anyone can see that fenland accounts for small areas of land mass. The real carbon sinks are vast phytoplankton blooms in the world’s oceans destined to become chalk and limestone. Seems like what is out of sight is out of mind.

  4. thecliffclavenoffinance permalink
    September 20, 2022 12:53 pm

    Based on observations since 1940, an ECS of more than +1,5 degrees C. is not justified. There has been a small positive feedback from more water vapor in the warmer troposphere, but that’s already included in the ECS.

    And the +1.5 degrees C. ECS assumes all warming since 1940 was caused by CO2, which is only a worst case assumption. Since the effect of CO2 is logarithmic, future increases of CO2 should have a smaller effect than the past increase of CO2, which was already mild and harmless, even if you assume all global warming was caused by CO2. There has been no warming for the past seven years, per UAH data, even as Climate Howlers were more hysterical than ever.

    The “warming” since 1975 was mainly higher TMINs in colder nations during the six coldest months of the year. Think of warmer winter nights in Siberia. That’s a climate emergency? That’s actually good news for the few people who live in Siberia.

    The IPCC / Climate Howler versus Climate Realist arguments are not mainly over the initial effect of CO2. although the IPCC starts with a high estimate.

    The primary debate is over the claimed water vapor positive feedback that allegedly triples the effect of CO2 alone. That theory changes AGW, for which there is evidence, into CAGW, which is imaginary, never seen in observations, even with CO2 levels up to 10x higher than today.

    CAGW is a failed prediction — wrong for the past 50+ years
    Yet that prediction of CAGW is used to justify Nut Zero — the very expensive and infeasible project to make electric grids less reliable.

    • Chaswarnertoo permalink
      September 21, 2022 8:21 am

      Wrong since Einstein disproved Arrhenius in 1917. The insanity staggers me.

      • thecliffclavenoffinance permalink
        September 23, 2022 5:11 pm

        Einstein did no such thing
        If he did, then he was wrong

        Einstein was wrong about many subjects

        Here are five of them:

        Einstein wrote a paper entitled “Why Socialism” and it he stated the following: “I am convinced there is only one way to eliminate these grave evils, namely through the establishment of a socialist economy, accompanied by an educational system which would be oriented toward social goals.”

        Einstein was not a genius on every subject.

  5. September 20, 2022 2:40 pm

    Evaluate these results with the work by Roger Pielke Jr. Climate scientists love to use RCP 8.5 emission scenario which puts way too much CO2 in the atmosphere then treat this as “business as usual”. The emissions over the next 80 years are much more likely to be half to a third this BAU so the RCP value should be between 2.5 and4. Combine that with a lower climate sensitivity and you are looking at warming of 1.5-2 degrees C by the end of the centry. Finally look at Richard Tol’s modeling who published in earlier IPCC reports that economic impact of 2 C warming was actually positive.
    I realize this is all modeling but since politicians seem hellbent on running the world around climate change priorities based on modeling they must surely be learning that the more serious a government is about tackling climate change the bigger detrimental the economic impact of climate change solutions are. Perhaps it’s time to push more rational actions. In fact the pandemic might give them a motto, “flatten the curve” as it will likely be feasible to satisfy climate model and economic scenarios simply by holding worldwide global greenhouse gas emissions flat as the undeveloped and the developing world begins to enjoy the benefits of low cost energy, particularly electricity.

    • Harry Passfield permalink
      September 20, 2022 7:15 pm

      So politicians are not so much ‘hellbent on running the world’ as hellbent on ‘ruining’ the world. It’s not that much different than writing that the world is about to go to Hull.

  6. StephenP permalink
    September 20, 2022 3:07 pm

    I get the impression that there are too many reputations and is too much scientific and financial investment in the global warming scenario (scare-ario?) for anything much to happen soon.
    Although the recent surge in energy prices ma start to make people think again.

    • Cheshire Red permalink
      September 20, 2022 4:36 pm

      This is the correct answer. ^^^^^^

      As to the numbers, ECS has always blown a huge hole in the scare, as they all know so well. Hence in the absence of a definitive number IPCC et al will continue to make numbers up to justify their positions and power-grabs.

      There’s zero chance this racket will be put in the bin in our lifetimes.

  7. September 20, 2022 3:13 pm

    In 1992, the UN Rio Environment Conference declared a rise of 3C was coming and CO2 was the demon causing it. I think in 1992 the figures were a back of an envelope estimate at best, but it was in line with the prognostication of the Club of Rome/WEF. The lie was repeated often enough that it became a truth and the Holy Grail of the Green Blob. What we are now seeing, as Gore would say an inconvenient truth, of there simply not enough necessary mineral resources on earth to make the political “wet dream” of a decarbonized world come true.

    • dave permalink
      September 21, 2022 9:30 am

      When the predictions first came out, they were touted as reassuring – published as being along the lines of, “ONLY a rise of a few degrees, at worst.” What has changed is that it has been found convenient by some interests to initiate a Project Fear about something which is in truth utterly picayune.

      It is easy to gaslight human beings.* Witch Doctors have been doing it since the dawn of time. I suppose the really odd thing is that so many of the ju-ju men end up believing their own B.S.

      * Who recalls that we were solemnly told in the days of the great Brexit Project Fear that from the the day we left ALL aircraft would be grounded and that NO drugs would be available in the hospitals? And that lots of people believed it?

  8. ancientpopeye permalink
    September 20, 2022 4:17 pm

    Who could have possibly suspected this? ‘Experts’?

  9. September 20, 2022 5:03 pm

    Cloud albedo is often forgotten. A mistake IMO.

  10. John Hultquist permalink
    September 20, 2022 5:35 pm

    For 2022, the ppm of CO2 is going to be an average of about 419. A doubling would take us to 838 in 175 years ( 2197 ).
    Can humans cause such an increase? I’ve read it is not possible.

    • September 20, 2022 7:07 pm

      Probably well past saturation point anyway.

    • kzbkzb permalink
      September 20, 2022 7:55 pm

      They mean a doubling since pre-industrial times i.e 2 x 280 ppm

      • John Hultquist permalink
        September 21, 2022 4:01 am

        That’s so last century. They need to catch up.

    • Stuart Hamish permalink
      September 21, 2022 6:49 am

      Humans cannot so much ’cause’ such a speculated increase as contribute to it ….So of course it is “impossible ” …..The anthropogenic ‘causation ‘ notion is like a ‘bad weed ‘ that just keeps coming back

    • Chaswarnertoo permalink
      September 21, 2022 8:24 am

      Not even if we burn all available fossil fuels could this desirable outcome be achieved.

  11. catweazle666 permalink
    September 20, 2022 5:55 pm

    Other estimates of climate sensitivity, however…

    It is interesting to extrapolate the ECS and TCR trend lines forward to 2025 – 2030…

    • Cheshire Red permalink
      September 20, 2022 9:08 pm

      This is a damning graph.

      It reveals that ‘climate science’ actually cannot agree on THE single most important issue. You’d think after 30-odd years and untold billions they’d have got this sorted by now, but nope.

      If they can’t agree (and self-evidently they can’t) then what does this outcome say about The Science, the Theory and The Methods they use?

  12. September 20, 2022 7:11 pm

    Indeed – leads inexorably to somewhere near zero 🙂

  13. Gamecock permalink
    September 20, 2022 8:58 pm

    ‘After correcting the Sherwood et al. methods and revising key input data to reflect, primarily, more recent evidence, the central estimate for climate sensitivity comes down from 3.1°C per doubling of CO2 concentration in the original study to 2.16°C in the new paper.’

    Two decimal places. Impressive!

    BOTH numbers are bullshit, but Lewis gets the annual prize for most ridiculous false precision fallacy.

    • dave permalink
      September 21, 2022 4:25 pm

      “Two decimal places.”

      Interesting. There is actually something more going on. One commonly rounds numbers which are observations, but one does not always round the further numbers arising from arithmetical operations on the observational numbers.

      For example, let us say I weigh one of three sisters and report the result as 124 pounds. In doing this I am adhering to a certain convention in science. I am saying that I am certain about the 1 and the 2 but not about the 4. The 4 could be a 3 or a 5 but not a 2 or a 6. (If I think it could be a 2 or a 6, I would report it as 122 pounds + or – 2.)

      Now I weigh the other sisters and report their weights as 118 and 128.
      The combined weights could be as little as 367 pounds or as much as 373 pounds and the average weight as little as 122.333 (say 122) and as much as 124.33.. (say 125). But the CALCULATED ‘average weight’ IS exactly 123.333… pounds. The convention is not to round this. The scientific community assumes that the reader will understand the nice points of measurement and sampling theory. Probably a rash assumption!

      In fact, the convention with manipulations of numbers is to round only at the end of all of the calculations when, as it were, one returns from the maths to the physical phenomena.

      Returning to reality: I may SAY or IMPLY what I like about my competence as a scientist, but then I may also be an idiot, and not notice that the rather vain 124 pound girl slyly kept one foot on the floor and actually weighs 170 pounds.

  14. Keith Harrison permalink
    September 20, 2022 8:59 pm

    From Clintel interview with William van Wijngaarden, York University, Canada :

    Doubling CO2 from 400 to 800 ppm will increase the temperature by about 1 C. Saturation means the temperature increase depends on the logarithm of the CO2 concentration change. To get an additional 1 C warming, CO2 would need to double again from 800 to 1600 ppm. At the present rate of increase of 2 ppm/year, it would take about 2 centuries to double CO2 to 800 ppm.”

    • September 20, 2022 10:11 pm

      Doubling CO2 from 400 to 800 ppm will increase the temperature by about 1 C.

      The only conceivable chance that would have of being true would be if all other climate factors were stable and unchanging, which they’re not. So these sort of assertions are basically just unhelpful.

      • Keith Harrison permalink
        September 20, 2022 10:30 pm

        Thanks for in depth analysis.

      • Phoenix44 permalink
        September 21, 2022 9:02 am

        Will increase the average of averages of averages by one degree.

        Still no-one can explain how the temperature experienced at any given time at the vast majority of locations is no different from temperatures experienced prior to that time and that’s a problem – except with averages. But reality is not the average of the last ten years compared with the average of a previous 30 year period. That’s human fiction, not reality..

      • September 21, 2022 3:20 pm


        I disagree that these assertions are unhelpful. By assuming that all other climate phenomena are constant, it is possible to determine the effect of IR active gases as a baseline.

        If climatology claims the effects are worse than determined by this analysis, then they have to present evidence to at least the same standard.

        Here is a graphic tool that uses data from the NASA Planetary Spectrum Generator (derived from HITRAN) to compare temperature increase with respect to CO2 concentration from this data, and that predicted by RCP6.0:

        (Note: Water vapour and Lapse Rate feedbacks are included)

    • catweazle666 permalink
      September 20, 2022 10:28 pm

      That’s why they invented “tipping points”!

      • Cheshire Red permalink
        September 21, 2022 9:41 am

        Tipping point = cliff edge = emergency = call to action = policy roll-out = Green Blob wins.

        Meanwhile no worthwhile evidence for any man-made climate tipping point exists, anywhere.

      • Chaswarnertoo permalink
        September 21, 2022 12:54 pm

        Which have never been evidenced.

  15. pardonmeforbreathing permalink
    September 21, 2022 7:17 am

    ONLY “if” CO2 is the driver for which there exists NO statistically significant empirical data only wrong infernal model after wrong infernal model! What about the big shiny thing in the sky?
    Let me remind everyone that a model is an entity produced in the absence of empirical data to approximate possible outcomes. Its output is statistical and not empirical data, and it should under no circumstances be considered as a replacement for such.
    This whole pile of sewage needs to be looked at just like a criminal court case where ONLY facts are admissible.
    Models and their predictions are hearsay and of no value and carry no weight whatsoever.

  16. Coeur de Lion permalink
    September 21, 2022 10:22 am

    The Guidance for Policymakers fronting AR6 has a Hockeystick showing no MWP nor LIA and an enormous uptick in today’s temperature. With unbelievable effrontery this is not part of AR6 working. The sainted Steve MacIntyre on his shows what a fraud it is. Why believe the IPCC at all? I’m a fan of the multiple papers at notrickszone showing ECS numbers well below one degC

  17. James Broadhurst permalink
    September 21, 2022 9:40 pm

    Another press release according to the Times environment editor Adam Vaughan ….. SSE, Amazon and 100 other “big” companies have written to the government asking it to maintain net zero targets etc.

    I can’t find any trace of this. Has anybody seen it?

  18. davidrussell22 permalink
    September 26, 2022 11:38 am

    At this point the CERES data demonstrate that climate sensitivity is on the order of 0.5K, which is immaterial. What I mean is the actual measured temp response at the surface to a W/M2 increase at TOA is half what the theory claims. And as the CERES data include WV feedback, the only thing missing is long term lag, which if you just juice up CERES “over ocean” response to the level of “over land” response adds another couple 10ths of a degree.

Comments are closed.

%d bloggers like this: