New data imply lower climate sensitivity, thus slower global warming

New paper by Nic Lewis and Judith Curry suggests future warming would be a third to nearly half of what the IPCC claims.

A paper just published by the Journal of Climate concludes that high estimates of future global warming from most computer climate simulations are inconsistent with observed warming since 1850. The implication is that future warming will be 30 to 45% lower than suggested by the simulations.

The study estimates climate sensitivity — how much the world will warm when carbon dioxide levels increase* — from changes in observed temperatures and estimates of the warming effect of greenhouse gases and other drivers of climate change, from the mid/late 19th century until 2016.

The paper also addresses previous criticisms of the methodology used, finding that these are unfounded.

Lead author Nicholas Lewis explains,

“Our results imply that, for any future emissions scenario, future warming is likely to be substantially lower than the central computer model-simulated level projected by the IPCC, and highly unlikely to exceed that level.”

He adds,

“Our new sensitivity estimates are slightly lower than those obtained in a predecessor study published several years ago, despite the inclusion of the strong 2015–16 El Niño warming. Importantly, the upper uncertainty bounds of the new estimates are much lower.”


  • The estimates of effective radiative forcing given in the latest IPCC Assessment Report (AR5) are used, extended up to 2016, with recent revisions to greenhouse gas forcing and post-1990 ozone and aerosol forcing estimates incorporated.
  • A median estimate for ECS* of 1.66°C (5–95% uncertainty range: 1.15–2.7°C) is derived using globally-complete temperature data. The comparable estimate for 31 current generation (CMIP5) computer climate simulation models is 3.1°C.
  • One of the chief criticisms of the method used is that it does not allow for the possibility of climate sensitivity varying with time after imposition of forcing, as it does in most CMIP5 models. However, the paper shows that when calculated so as to correctly reflect CMIP5 models’ behaviour, this possible effect is immaterial to either the study’s or CMIP5 models’ median ECS estimates.§
  • A median estimate for TCR* of 1.33°C (5–95%:1.15–1.9°C) is derived using the same data. The comparable estimate for the 31 CMPI5 models is 1.9°C.
  • The estimates of climate sensitivity are remarkably insensitive to the period of analysis chosen (see Figure 1).


Figure 1: Remarkably, estimation of climate sensitivity using the 1927–41 mean gives the same sensitivity estimate as using the 2007–16 mean. Circles show 1872–2016 pentadal-mean changes in net outgoing radiation (cyan pre-1927, blue post-1927) plotted against change in globally-complete surface temperature. The slope of the relationship is inversely proportional to climate sensitivity. Red squares show 15-year means from 1927–41 to 2007–16. Despite the effects of multidecadal internal variability, all the 15-year means lie close to the 1872–2016 pentadal-means regression best-fit line.

  • These median ECS and TCR estimates imply multicentennial or multidecadal future warming under increasing forcing of only 55−70% of the central warming projection using CMIP5 models.
  • It has been suggested in various studies that forcing-efficacy effects (principally, cooling aerosol forcing having a stronger than normal effect), variability in sea-surface warming patterns and temperature estimation issues likely lead to climate sensitivity estimates based on warming over the last circa 150 years being biased low. All these issues are examined in detail in the paper, the conclusion being that very minor or no bias was to be expected when using globally-complete temperature data.

Nicholas Lewis and Judith Curry, 2018: The impact of recent forcing and ocean heat uptake data on estimates of climate sensitivity. Journal of Climate, Early Online Release


Energy budget estimates of equilibrium climate sensitivity (ECS) and transient climate response (TCR) are derived based on the best estimates and uncertainty ranges for forcing provided in the IPCC Fifth Assessment Scientific Report (AR5). Recent revisions to greenhouse gas forcing and post-1990 ozone and aerosol forcing estimates are incorporated and the forcing data extended from 2011 to 2016. Reflecting recent evidence against strong aerosol forcing, its AR5 uncertainty lower bound is increased slightly. Using a 1869–1882 base period and a 2007−2016 final period, which are well-matched for volcanic activity and influence from internal variability, medians are derived for ECS of 1.50 K (5−95%: 1.05−2.45 K) and for TCR of 1.20 K (5−95%: 0.9−1.7 K). These estimates both have much lower upper bounds than those from a predecessor study using AR5 data ending in 2011. Using infilled, globally-complete temperature data gives slightly higher estimates; a median of 1.66 K for ECS (5−95%: 1.15−2.7 K) and 1.33 K for TCR (5−95%:1.0−1.90 K). These ECS estimates reflect climate feedbacks over the historical period, assumed time-invariant. Allowing for possible time-varying climate feedbacks increases the median ECS estimate to 1.76 K (5−95%: 1.2−3.1 K), using infilled temperature data. Possible biases from non-unit forcing efficacy, temperature estimation issues and variability in sea-surface temperature change patterns are examined and found to be minor when using globally-complete temperature data. These results imply that high ECS and TCR values derived from a majority of CMIP5 climate models are inconsistent with observed warming during the historical period.

* Two standard metrics summarize the sensitivity of global surface temperature to an externally imposed radiative forcing. Equilibrium climate sensitivity (ECS) represents the change in temperature to a doubling of atmospheric CO2 concentration once the deep ocean has reached equilibrium. The transient climate response (TCR), a shorter-term measure over 70 years, represents warming at the time CO2 concentration has doubled when it is increased by 1% a year.

† Changes are relative to the 1850–1884 mean (this period has the same mean volcanic forcing as for 1850–2016). All volcanic forcing has been scaled by 0.55 to adjust for its low efficacy [discussed in the paper]. ΔR (= ΔF − ΔN) is estimated by scaling ΔF, based on ΔF and ΔN values for 2007–16.

§ This finding is in line with that in Mauritsen & Pincus 2017.

PDF copies of a version of the accepted manuscript for the paper and its Supporting Information, along with an article giving information about the paper and its findings, is available on Nicholas Lewis’s personal web-site, here. A blog-post version of the article is available at Judith Curry’s web-blog, here. Nicholas Lewis is the sole or lead author of six previous peer-reviewed papers about climate sensitivity.

130 thoughts on “New data imply lower climate sensitivity, thus slower global warming

  1. now just get rid of the made up 2 degrees is going to kill us all
    I predict this paper will not be even seen….and if it is… will be more of consider the source

    • I assume many of the readers here are aware of the list of 75 peer reviewed papers that find low climate sensitivity, shown over at
      I have looked over the list and read through a few papers, but I have not scoured the list, so I can’t say none of the papers have been mischaracterized.
      If we ignore the papers that claim “zero” sensitivity, the next lowest number is 0.02C for 2X CO2. Of course, the IPCC is on the other end of the spectrum and offers several scenarios with much higher sensitivities. If we take 4.5C as one of the higher values and 0.02C as one of the lower values, then the range of climate sensitivity according to peer reviewed science is:
      We can arbitrarily discard some of the values in the tails of the distribution and shrink the range, but I think we are still going to see > 10:1.
      Imagine if in 2018, scientists were still “debating” the charge of an electron, the mass of a proton, or “Big G” – and the range of values being debated was > 10:1. Think of the technologies and products that we wouldn’t have if we didn’t know these things.
      I know climate is a much bigger scientific nut to crack, so not having an answer to sensitivity is understandable. What is not understandable is the level of confidence and conviction exhibited by Climate-Alarmist in the face of this massive range of uncertainty.

  2. Right about the same sensitivity range as Lindzen and Choi, and Monckton, all presumably using different methods to reach a sensitivity estimate quite a bit lower than the IPCC median.

    • Monckton thinks the sensitivity is 0.5°C, but can prove it’s 1.2±0.15°C and 1.45°C is pushing it as far as possible in the “totalitarian direction”.
      I’m not sure how a range of 1.15–2.7°C, with a median estimate of 1.66°C, is about the same.

    • Very close to my calculation of 1.62 based on the specific heat ratio of the differing gases in the atmosphere.

  3. While this is a very significant report, it still assumes a direct monotonic relationship of temperature to CO2. I don’t buy this vast oversimplification of Earth’s climate.

    • Yes! Exactly! Still no recognition of potential negative feedbacks, even though the entire history of life-friendly climate on this planet screams balancing feedbacks.

      • This study is based on actual observations, so it is by definition after the impact of negative feedback

      • I haven’t read the paper, but one of the underlying assumptions of almost any paper on climatology is that the climate is a massively complicated web of positive and negative feedbacks. It’s the total average effect of these feedbacks which is in discussion here.

      • You can’t “average” a chaotically-coupled system. While it may center around an attractor, its behavior at any given time is by nature unpredictable.
        The climate could flip into a cold trend any time now (may already have) and there is no proof anywhere that it can’t.

      • **This study is based on actual observations, so it is by definition after the impact of negative feedback**
        The only observations I see is radiation and temperatures. I think the rest is calculations based on certain assumptions. One day we will get the REAL Climate Sensitivity which will be closer to zero.

      • Although it’s correct to say we can’t confidently predict or average chaotic systems, in practice, we do it all the time.
        Measuring the temperature of of a cup of coffee is averaging the kinetic energy of billions of chaotically colliding molecules.
        Measuring and predicting the time it will take to arrive at your destination is working with the chaotic and unpredictable traffic patterns.
        Although rainfall in any location is an unpredictable result of chaotic interactions, it tends to be reasonably consistent over decades, so your desert tends to stay a desert, and your rain forest tends to stay a rain forest.
        These predictions can be wrong, but the chaos tends to average out, and systems tend to fall into various patterns (attractors) that behave consistently and predictably over various time periods.
        …until they don’t, and you miss your flight.

      • Once you consider that the underlying data was based on temperature records which have been massaged by (screwed with) the Alarmist Team, then the true number will be considerably lower. Could it really be zero?

      • Eustace
        “While it may center around an attractor, its behavior at any given time is by nature unpredictable.”
        I think it is important to point out they are not making predictions, they are analysing the past: that is, putting a range of possible behaviour based on what is known to have happened in the recent past.
        Obviously large excursions from what happened in the past 170 years are possible, in which case researchers alive at that time will develop the work.
        The important work is to put limits, to constrain possibilities, using what information is available. The conclusion strongly constrains the upper limit to less than 1.5 degrees C for a doubling of CO2. The possibility that we could emit that much is unlikely (where would we find it?).
        We do not need the Paris Accord costing $100 trillion is there is no meaningful chance of matching the emission or temperature assumptions. In 100 years we will have electrified and gone nuclear. By then the prophets of doom will be warning that the Earth only has a carrying capacity of 25 billion people unless we farm the rest of the Sahara.

    • Same here. This is a too simple approach that the observed temperature is depending on the CO2 concentration only. There are so many other variables that you must first show that they have no effect. I do not buy this approach. .

    • it would be surprisining if it WASN’T a monotonic relationship. You might want to look up the definition of the term.

      • A monotonic function is either increasing or decreasing across its entire domain. If we plot planetary temperature (range) versus CO2 concentration (domain), has the function always been monotonic? No.

      • To answer the question, we have to control for Albedo, which of course is very important.
        Let’s think about Cretaceous Earth with very high sea levels due to the young oceans not being very deep. 30% of the continental shelves, continental areas are covered by shallow ocean and there is very little landmass at the poles (where snow and sea ice and glaciers can build around).
        Or Snowball Earth at 640 million years ago when super-continent Pannotia is centred over the South Pole with 5 km high glaciers.
        Earth’s Albedo is 24% in the Cretaceous and 40% in the Snowball period. Think about how much solar radiation impacts the Earth in those two scenarios. You can’t solve CO2 sensitivity without controlling for this other extremely important variable.

      • If all other things were held equal, changing CO2 would result in a monotonic change in temperature.
        The problem is that all other things are never equal.

    • “While this is a very significant report, it still assumes a direct monotonic relationship of temperature to CO2. I don’t buy this vast oversimplification of Earth’s climate.”
      Maybe or maybe not but it is another study that helps establish an upper possible range that is much lower than the ones we have been scared with for the past 20 years. It’s not much different than LM’Bs approach in that it shows the Warmist cult that even accepting their premise there is no catastrophic warming coming and therefore it is at worst a simple case of adapting to change as it comes and we don’t have to put the entire world under dictatorial rule to save us all.
      [“LM’B” = ??? .mod]

    • The decent into the LIA temperatures had nothing to do with CO2. Subsequent warming has a non-CO2 component. Teasing out the CO2 component (ECS/TCR) is fraught with uncertainties.

    • Wilhelm Wien’s displacement law relating to black-body radiation energy might suggest an escape hatch from the unquestioned dominance of CO2 in climate The Planck-Einstein relation in quantum mechanics states that a photon’s energy (E) is proportional to its frequency (v), so that energy is expressed by a constant of proportionality (“h” or the “Planck constant”) and frequency
      E = hv.
      Since frequency relates inversely to wavelength (λ), “v” may also be written as the speed of light divided by peak wavelength, or c/λ. Wien’s peak displacement law, also known as the Wien approximation, states that wavelength (λ) for black-body frequencies peaks at a maximum. Wien’s displacement law is
      λ = b/T,
      with T in Kelvins and b the displacement constant (b ≈ 2900×K) applied to the wave¬length. It also determines temperature by wavelength:
      T = b ÷ λ.
      Higher energy high-frequency photons are at shorter wavelengths, so wavelength relates inversely to temperature. Some observations state that the Earth emits its highest energy IR long wave photons at 8-12μm wavelengths, directly through a window to space without interacting with any gases. Whether that is so or not, it shows effect of a few microns’ wave¬length on temperature. By Wien’s law, the 8μm photons exit the atmospheric window at 89°C and 12μm photons exit at -31.7°C, spanning a temperature drop of 120.7 Celsius degrees.
      By comparison, CO2, interacting with infrared radiant energy at a peak 15μm wavelength does so at a -80°C temperature.
      Try it T = 2900 ÷ 15 = 193°K or -80°C
      If that is so, it t raises the question how a gas interacting with radiation at minus 80 Celsius degrees threatens to warm the atmosphere at all. I have never seen this relation discussed at any length, but it seems a promising avenue of inquiry.

  4. Eventually it will be discovered at the earth’s atmosphere is insensitive to CO2 concentrations. Then it will be discovered that atmosphere CO2 concentrations have no affect on atmosphere temperature.
    Ha ha

    • In response to JBom April 14, 2018 8:30 am:
      Until then, we should rename “carbon dioxide”. Its new name should be “carbon obnoxiouside”.
      That or “carbon mojoxide” [you know, mojo, magic, … as in a gas with magical powers in very small concentrations].

    • Yes, high-frequency UV is hot, no contest. The question is about low-frequency IR. It can run pretty cold. Supposing that the one thing the warmists forgot to check when they constructed their imposing edifice was “how hot is this gas running?”
      It looks like the temperature of the low-frequency IR range (13.5-17μm, peak 15μm) where CO2 absorbs and emits, is down around -80°C. I do not believe that a doubling of a -80°C interaction with infrared radiation will double cooling, that’s a preposterous notion. It strikes me that it will simply result in 100% more absorption/emission activity, but as a practical matter, no “heat build-up.” In which case, is there really cause for concern? Has this been a wasted trip?
      As I say, I haven’t had a response from a physicist yet, so I find myself in an uncomfortable minority of one.

  5. I predict that future warming will not be any more than the past 100-200 years of warming. There, you have my non-expert opinion…

    • Greg Woods,
      “I predict that future warming will not be any more than the past 100-200 years of warming. There, you have my non-expert opinion…”
      Since the most basic reasonably accurate weather forecast is that tomorrow’s weather will be the same as today’s, you probably have about a 50/50 chance of being more accurate than any particular climate prediction by a well-funded scientist.
      You should claim half of all their grant monies.

  6. It does take the C of the CAGW hypothesis.
    In effect that would take virtually all the frenzy from the discussions and return man to a course that allows natural gas to resume the downward energy price and pollution fall.
    With that the West can resume the spending on the poor rather than the virtue signally rich.

    • That’s why they drive 1.5K as the C limit of the AGW/CC. They want to keep the C in the horizon, in a Menckenian attempt to control voters.
      It is clear that this alarm was just wrong, but it will take 30 years to admit it.

      • They will never admit it.
        There just will be a new crisis and no evidence that anyone ever talked about CAGW.

  7. I believe the Earth’s temperature is sensitive to CO2 and water vapor, otherwise we would be under a mile of ice. The question really is this: Is the Earth’s climate sensitive to a small change in CO2 levels and the assumed large positive feedback amplification due to increased water vapor resulting therefrom. This would imply a runaway situation which is clearly ridiculous, given the Earth’s history of huge changes in CO2 levels and the fact that we humans have taken millions of years to evolve into beings that can ponder climate change.

    • Sun warms water. Water warms nitrogen/oxygen air. Air flows. Warm air mixes with cold air and gets distributed. … just cool enough on the day side to keep the day side from being an inferno, and just warm enough on the night side to keep the night side from being a frozen hell.
      Maybe CO2 plays a small role in regulating energy flow throughout the greater atmospheric mass. Water vapor plays a big role, as its amazing transformative abilities perform the real magic. CO2 mostly goes along for the ride.

      • The point the theory makes is that CO2 doesn’t undergo phase change in our atmosphere, i.e. CO2 is a non-condensing GHG. Thus its modest GH effect remain near constant through the atmosphere at a given concentration. And the atmosphere is the buffer through which all IR energy (stored in the oceans and land as heat) must pass to get back out to space to balance the energy budget between incoming SW and outgoing LW radiations.
        The alarmist climate modellers must invoke high positive feedback from that additional water vapor as a GHG In this positive feedback assumption they focus mainly on a purely radiative mode of energy transport by which water vapor and CO2 raises. In a pure blue sky climate model (water vapor remains transparent to SW energy) this would mostly work. The fatal flaw of climate models is that water vapor turns to clouds and then to precipitation that they have no hope of modelling on first principles. So the real bugaboo the modellers hate in water is as it phase changes (evaporates, convects heat, and condenses) it transports vast amounts latent heat upwards through the radiative impediments of CO2 (and the other GHGs like methane). And convection and the microphysics of water phase changes are poorly constrained by observation, So the modellers are relatively free to use whatever values for those parameterized processes they feel comfortable with (meets their bias, is another way of putting it.) Thus Cargo Cult Science is born whereby the underlying model paradigm is utterly wrong and can never (except by post hoc cherry-picking mere chance with enough model runs) accurately project the climate response to more CO2.

  8. The Guardian no longer has an Environment section. Presumably articles on environmental issues will now be filed under Science. I don’t know when they changed this, but it couldn’t have been long ago.
    The Guardian used to consider saving the world from global warming as one of its principal mandates. Alarmist columns were a regular feature, and any commenter who dared suggest that the situation might not be as dire as depicted was instantly pounced upon by a pack of thought police, with “Denier!” ringing from the rafters.
    Could The Guardian be backing away from their Chicken Little stance? Or do they not have the budget to commission articles on the environment at the rate that they used to? Or both?

    • Never mind all the scientific arguments, I just knew the CAGW narrative was nonsense when I saw the Guardian espouse it.
      The Guardian – wrong about everything, all the time.

    • The Guardian does still have an Environment section.
      It’s here.
      However, their latest redesign makes navigating the website very difficult.

  9. IMO the central ECS estimate of 1.66 degree C per doubling of CO2 is still too high. On a homeostatic, water world, net feedback effects should be negative, not positive. Thus the actual number ought to be less than the laboratory value of 1.1 to 1.2 degree C.
    The effect of a little more plant food in the air varies geographically. In the hot, moist tropics and over cold, dry Antarctica, the net effect of more CO2 could well be cooling rather than warming.

    • “Thus the actual number ought to be less than the laboratory value of 1.1 to 1.2 degree C.”
      Except this value is also not correct, because there is no greenhouse warming signature with a 1.1C linear surface/atmosphere warming according to the lapse rate, which is how this value is derived.

  10. The temperature hasn’t gone up for 18 years. Doesn’t anybody care about the actual, physical world facts anymore? The very same climate change that people have experienced since there were people is now somehow “catastrophic”!
    Now the planet is cooling and still we hear about sensitivity. This is garbage. What aspect of CO2 heat retention allows for the planetary temperature to go down sometimes?

  11. Here again we see the 100% faulty and clearly default position of so many otherwise nominally skeptical scientists that it is CO2 that warms the ocean.
    The increasing outgoing longwave radiation and change in temperature over time that are used to determine “climate sensitivity” were in reality driven by strong sunlight penetrating into the tropics, energy that spread out into the ocean, causing net warming, when solar activity was high.
    TSI and insolation warm the ocean, and CO2 is a by-product.
    The climate sensitivity concept should be reframed as the temperature forcing performed by solar activity.
    A discussion article about solar climate forcing based on my research is underway.

    • CO2 is indeed the byproduct, and clearly does not cause warming. If it did, there would be no way for the earth to cool down and thus no way for CO2 to be reabsorbed into the oceans. The temperature would have “run away” billions of years ago.
      the concept is ludicrous at first glance.
      It is a political project from the eco- Left to destroy Capitalism and grab power for themselves.

  12. Went and read the thing and the supplemental info. The importance of the new 2018 paper is not the conclusions, which are in the previous range. It is the careful examination of all the warmunist critiques leveled at Lewis and Curry 2014, and Lewis 2015. None of the criticisms matter.

  13. Combine this finding of modest warming (1.5 k / 2xCO2) with the vast benefits to the biosphere of CO2 enhanced fertilization, and it is win-win for us all, including nature.
    Of course the neo-Marxists, the rent-seekers, and the true-believers of the Church of CAGW scriptures point to resource depletion and environmental degradation from mankind’s continued development. The reality is those two negatives are a function of societal wealth. Where natural resources are permanently spoiled are in the economically poorer nations of the world, the same places the Malthusian watermelons want to keep poor. In the developed West, we have the economic resources for remediation of past degradation and technologies and methods to limit future degradation. And as poorer nations become wealthier, birthrates naturally come down.
    Couple all that with reduced need for energy demands heating in temperate and sub-Arctic populations, and the win-win-win becomes all the more apparent, to great consternation of the neo-Marxists wanting a One World Socialism.

  14. Combine this finding of modest warming (1.5 k / 2xCO2) with the vast benefits to the biosphere of CO2 enhanced fertilization, and it is win-win for us all, including nature.
    Of course the neo-Marxists, the rent-seekers, and the true-believers of the Church of CAGW scriptures point to resource depletion and environmental degradation from mankind’s continued development. The reality is those two negatives are a function of societal wealth. Where natural resources are permanently spoiled are in the economically poorer nations of the world, the same places the Malthusian watermelons want to keep poor. In the developed West, we have the economic resources for remediation of past degradation and technologies and methods to limit future degradation. And as poorer nations become wealthier, birthrates naturally come down.
    Couple all that with reduced need for energy demands heating in temperate and sub-Arctic populations, and the win-win-win becomes all the more apparent, to great consternation of the neo-Marxists wanting a One World Socialism.

  15. This is just like what Richard Feynman wrote about in “Cargo Cult Science.”
    Millikan measured the chart on an electron by an experiment with falling oil drops. The result turned out to be slightly wrong. Other scientists did not find the same result, but they did not wish to differ from Millikan, so each result after that differed in only a slight amount. Feynman says that it was a “thing that scientists are ashamed of.”
    This is exactly what has been happening with climate models. They are curve fit to the (poor quality) historical data. If the sensitivity factor found for any given model is too far away from the currently accepted value, the model has been assumed to be wrong. The modeler then “adjusts” the model so that the value is more in line with the consensus. I remember reading a study about this years ago. These sensitivity factor values have been trending down for some time.
    But, why call these “sensitivity factors” when what they really should be called “fudge factors”?

    • Each climate model group is like its own separate island of Cargo Cultists. And world-wide, there are several dozen islands of Cargo Cultist climate modelers. They each have their own fudge factors, tweaked for their own model idealization of ocean-atmosphere dynamics.
      Every 4 years or so, they all get together in big conferences to compare notes on their Cargo Cult science. They call these Intercomparison Projects, and currently number 6 is underway. These conferences of Cargo Cultists modellers they compare whose runway lay-out is best matches the runway of their memories, or whose bamboo control tower might better attract the long-absent cargo planes filled with the wondrous goods they seek.
      Yes, the climate modellers with their supercomputers and truckloads of money to waste are the modern-day penultimate realization of Feynman’s description of Cargo Cult Science.

  16. If the IPCC is on a 5 year cycle and has ~100 climate predictive models then it should be a simple thing to toss out 2/3rds to 4/5ths as fundamentally flawed in time for the next publication.

    • The IPCCas a UN creation is socialist in its very nature. Socialists love group inclusion where everyone gets a participation trophy and no one loses.
      Exclusion (tossed out) is something capitalists and competitors do in their SJW view. In this world view, everyone (all modller groups) are assimilated as long as they all do not resist the consensus. Climatists are very (Star Trek) Borg-like.

    • ” it should be a simple thing to toss out 2/3rds to 4/5ths as fundamentally flawed in time for the next publication.
      They are all fundamentally flawed.. 100%. So by which method do you choose winners and losers? The IPCC and CMIP group decades ago avoided this problem by assimilating everyone who cooperates within the “consensus.”
      Resist and you got crushed in the peer-review publication of your work.

  17. I have a question! At what point may we assume this warming effect to “max. out”? And are we near to a point where additional CO2 just won’t matter? I’m asking because I know that for some green purists, this reduced sensitivity would still be too much.

    • Yup, the effect is logarithmic. Which is why sensitivity is expressed as “per doubling of CO2”. So put that in context for your alarmist friends:
      o We are currently at 400 ppm
      o We are increasing at about 2-3 ppm per year
      o it will take 133 to 200 years to double from where we are now
      o 1.5 degrees spread out over two centuries is slow motion. We can adapt at a teeny tiny fraction of the cost as issues arise. Sewering the economy and sending the entire 3rd world back to the stone age is an insane response. An inhumane response. A useless response.

      • The anthropogenic CO2 doubling, by convention, is taken from the assumed pre-industrial 285 ppm level, or 570 ppm.
        Assuming the annual accumulation rates only modestly accelerate, we will hit 2X CO2 between 2065 and 2085 with 2073-2075 as a central estimate.

      • joelobryan
        The anthropogenic CO2 doubling, by convention, is taken from the assumed pre-industrial 285 ppm level
        Yes it is. Which is a big part of the deception. What has the level in 1750 got to do with ANYTHING? We’re at 400 ppm NOW. It doesn’t MATTER what the levels were in 1750 EXCEPT in order to help calculate sensitivity. If we’re worrying about the future, why in the world would we start with 1750 instead of calculating the effects starting RIGHT NOW?
        I’ll tell you why. Doubling from 285 is WAY easier to do than doubling from 400. So the alarmists wail away about it as if it makes sense to do that. Don’t let them. Neither the temps nor the CO2 level in 1750 have anything to do with what happens in 2018 going forward. The past is the past, we cannot change it, it is NOW and the future starting NOW that we’re either going to mitigate or adapt to. 285 ppm is red herring.

      • Joelobryan
        “The anthropogenic CO2 doubling, by convention, is taken from the assumed pre-industrial 285 ppm level, or 570 ppm.
        Assuming the annual accumulation rates only modestly accelerate, we will hit 2X CO2 between 2065 and 2085 with 2073-2075 as a central estimate.”
        That’s fine too because you are still talking about only 1.6 degrees C from 1870’s to 2065, .8 C of which we have already experienced and no one can actually demonstrate any real negative effects from, however there are 7 Billion people on this planet that are experiencing the benefit of the extra CO2 in the atmosphere and its effect on cultivation yields and hence cheaper more available foods.

      • the 125 ppm delta between then (pre-1850) and today (410 – 285) is already baked into the climate cake.
        You can’t ignore it if you accept the CO2 AGW hypothesis (as most do accept).
        High sensitivity means it will take centuries for that delta of 125 ppm warming to fully realize even if anthropogenic emissions zeroed out today. Low sensitivity means most or all of the warming from that additional forcing has already occurred.

        • And I care about speculation as to what I do today affecting the far richer and vastly more technologically advanced peoples a few centuries from now why?

      • joelobryan
        Low sensitivity means most or all of the warming from that additional forcing has already occurred.
        And since we’ve seen very little warming, we can assume sensitivity is low, there’s diddly squat in the pipe. So let’s take that low sensitivity number and apply it to temps NOW and CO2 NOW and the whole charade starts looking ridiculous. How much of that first 115 can possibly be left in the pipe? 0.2? Less? Spread out over centuries? Who cares?

      • David,
        You seem to be neglecting the game the Climate Alarmist’s play.
        The smarter ones no longer talk about a catastrophe today. It is evident that there is no current climate catastrophe. (Despite the laughable claims by Climate Pope Gore of simply looking out your window and “seeing climate change in action”.)
        They have learned a painful lesson with near-term predictions. Now their climate catastrophes are always in some distant future. They learned near-term predictions (20 years or less) exposed them to the public to be snake-oil sellers they are, Thus they have turned to much longer term predictions of future climate catastrophe, like out to 80+ years, or end of the century stuff which cannot be outright falsified within anyone’s lifetime today. Thus they now can know their fake alarmist predictions will be forgotten to public memory.

        • Hee, hee, hee, …. AR5 had to arbitrarily reduce near-term temperature “projections” by the too-hot models because they couldn’t get their 0.2C/decade increase. I can’t wait for AR6 gymnastics.

  18. Warming causes an increase in CO2. If CO2 also causes warming (even 1/3 or 1/2 of warmists’ inflated guesses), then we would live in a world of wild climate swings. If anything, any warming caused by CO2 is a transient effect that I see little point in worrying about.

    • Perhaps I have missed it but I have not seen any proxy data that shows CO2 leading temperature, it is always temperature leading CO2.

      • The rate of change dCO2/dt is closely correlated with temperature and thus atmospheric CO2 LAGS temperature by ~9 months in the modern data record.
        Best, Allan
        403 875 4830 cel
        Observations and Conclusions:
        1. Temperature, among other factors, drives atmospheric CO2 much more than CO2 drives temperature. The rate of change dCO2/dt is closely correlated with temperature and thus atmospheric CO2 LAGS temperature by ~9 months in the modern data record. The rate of change dCO2/dt vs. temperature plot follows:
        2. CO2 also lags temperature by ~~800 years in the ice core record, on a longer time scale.
        3. Atmospheric CO2 lags temperature at all measured time scales.
        4. CO2 is the feedstock for carbon-based life on Earth, and Earth’s atmosphere and oceans are clearly CO2-deficient. CO2 abatement and sequestration schemes are nonsense.
        5. Based on the evidence, Earth’s climate is insensitive to increased atmospheric CO2 – there is no global warming crisis.
        6. Recent global warming was natural and irregularly cyclical – the next climate phase following the ~20 year pause will probably be global cooling, starting by ~2020 or sooner.
        7. Adaptation is clearly the best approach to deal with the moderate global warming and cooling experienced in recent centuries.
        8. Cool and cold weather kills many more people than warm or hot weather, even in warm climates. There are about 100,000 Excess Winter Deaths every year in the USA and about 10,000 in Canada.
        9. Green energy schemes have needlessly driven up energy costs, reduced electrical grid reliability and contributed to increased winter mortality, which especially targets the elderly and the poor.
        10. Cheap, abundant, reliable energy is the lifeblood of modern society. When politicians fool with energy systems, real people suffer and die. That is the tragic legacy of false global warming alarmism.
        Allan MacRae, Calgary, June 12, 2015
        RE POINT #1 ABOVE:
        Humlum et al reached similar conclusions in 2013 here:
        – Changes in global atmospheric CO2 are lagging 11–12 months behind changes in global sea surface temperature.
        – Changes in global atmospheric CO2 are lagging 9.5–10 months behind changes in global air surface temperature.
        – Changes in global atmospheric CO2 are lagging about 9 months behind changes in global lower troposphere temperature.
        – Changes in ocean temperatures explain a substantial part of the observed changes in atmospheric CO2 since January 1980.
        – Changes in atmospheric CO2 are not tracking changes in human emissions.”
        I suggest that the global warming alarmists could not be more wrong. These are the true facts, which are opposite to their alarmist claims:
        1. CO2 is plant food, and greater atmospheric CO2 is good for natural plants and also for agriculture.
        2. Earth’s atmosphere is clearly CO2-deficient and the current increase in CO2 (whatever the causes) is beneficial.
        3. Increased atmospheric CO2 does not cause significant global warming – regrettable because the world is too cold and about to get colder, imo.
        Regards to all, Allan

      • And it is not ‘the IPCC claims’, but the central estimate of the IPCC. There are a lot of range of estimates in the IPCC reports.

    • Exactly so. Farther down in the article is:

      These median ECS and TCR estimates imply multicentennial or multidecadal future warming under increasing forcing of only 55−70% of the central warming projection using CMIP5 models.

      ie. their climate sensitivity estimates are 30 to 45 percent lower than the central warming projection using CMIP5 models.

  19. (cyan pre-1927, blue post-1927) plotted against change in “globally-complete surface temperature.” (QUOTES MY ADDITION)
    Globally-complete? Excuse me? Surely, I must be missing something because last I checked that is a patently inaccurate statement, considering the large swaths gaps, concentration in urban areas, homogenization, infilling, raw data adjustments, etc. I must be misinterpreting the meaning of “globally-complete”

  20. I would like to see a study of climate sensitivity based on the well sited (per Watts surface station investigation) temperature collecting stations in rural areas.

  21. I do not believe the the paper referenced proves that CO2 has any sensitivity on our climate at all. Maybe I’m miss interpreting the data but what I would be looking for is a departure in sensitivity starting in 1945 when CO2 production increases dramatically. Not the same sensitivity starting in the in the 19th century and running to early ion the 21st century. Where is the estimate for natural warming?
    I would remind all of the work of Dr. Richard Lindzen who estimated the sensitivity of our climate to CO2 at approximately .5 C/doubling.
    I find his work more believable.

  22. This will continue on its present path until such time as CLAWBACKS accompany any actions based on climate models. Warmists are modern day wandering rainmakers making fistfuls of cash off of post-Christian SJW’s.

  23. Climate Sensitivity (ECS) is a bit of a myth. Mainly because water ignores it and provides the reactive mechanism to ensure the the Earth’s temperature remains within a suitable range to ensure continuity of life. It is remarkable that this has been going on for millions of years and we don’t appear to have noticed it. In rough terms say within about 3% of the optimum whatever that is?.
    Mind you water is not very good at keeping us warm; but is very good at making sure we don’t roast. Hence long periods when it is too cold for our liking; interspersed with our current benign circumstances.
    Engineers know how this is done; but scientists seem to be ignoring this, hell bent as the are on matters of radiation, when Enthalpy is the crux of the matter, where temperature is an “also ran” in the dealings with how Enthalpy moves around.
    One fact which needs to be noted here (amongst many others) and that is that at phase change in water the ECS is a big fat Zero. There being a lot of water up there in the atmosphere and the speed at which it operates is a function of the equilibrium balance prevailing. It is a continuing process there in the clouds.
    Don”t expect many will understand what I am talking about.

  24. I hate backward ‘driving’ equations. Let’s call it what it is:
    ΔR = 2.269 ΔT and
    ΔT = 0.441 ΔR
    Because, after all, we are lead to believe that it is the change in outgoing radiation (driven mostly by greenhouse gasses) that drives retained median temperature change, and not vice versa.

  25. Lewis and Curry’s new median estimate for ECS* of 1.66°C (5–95% uncertainty range: 1.15–2.7°C) is consistent with Chris Monckton’s calculation of ECS=1.2.
    It would be a very satisfactory – if somewhat anticlimactic – resolution of the bitter and rancourous climate war to simply coalesce at a physically realistic and observation-consistent lower ECS of this order.

    • Oh but that would put the rent-seekers and the neo-Marxists out of the climate alarm business. Can’t have that.

  26. Well let’s see how much warming we get this year, because its looking like mother nature has moved the NH into cooling mode for this summer. Why do l say this.?
    Because since around 2005 there has been sharp declines in the Eurasian snow extent during May/June.
    Last year bucked that trend, this year am expecting that trend to be busted big time.
    Also am expecting a cooler northern Atlantic this summer. As there is likely to have been alot heat loss from the ice free waters in the NW Eurasian Arctic during March.

  27. It’s interesting that Lewis and Curry get lower estimates than I do in my newly published paper, though mine are not too high either.
    This is a summary of my peer-reviewed paper “On the influence of solar cycle lengths and carbon dioxide on global temperatures” recently published by the Journal of Atmospheric and Solar-Terrestrial Physics (JASTP), available at , or in publicly accessible pre-print form at .
    The paper builds on the work in the 1990’s by Friis-Christensen and Lassen, by adding a CO2 element to their model based on solar cycle lengths (SCLs). By using a linear regression model, statistical significance levels can be measured for these two effects. Using HadCRUT4 as the global temperature series, averaged over 11-year periods starting 4 years before solar cycle maximum, the CO2 variable is hugely significant, as it explains the overall upward trend, while the length of the previous cycle has a 1.3% significance level (more on this below), and this variable explains the wiggles in the graph which is Figure 1 of the paper.
    The upshot of the analysis is an estimate of TCR (Transient Climate Response) of 1.93K, and of ECS (Equilibrium Climate Sensitivity) of 2.22K. Under an assumption of continuing increases of CO2 concentration by 2 parts per million each year, the expected HadCRUT4 anomaly in AD2100 is only 1.1K higher than it was during the period 1996-2006.
    Allowing for the SCLs does make material (but not vast) differences:
    • without them the TCR estimate would be 2.37K instead of 1.93K
    • they explain 37% of the observed warming between 1980 and 2001
    • without them the residual errors significantly differ from the model assumptions
    And now, a few words on the statistics. For “layman” readers the meaning of the 1.3% above is that if there really is no solar effect, then it was an 80 to 1 shot or so against these observations having occurred. Of course, 80 to 1 shots do sometimes happen by chance, but…
    For more mathematical readers, it is worth noting that compared with a lot of climate papers the statistics are pretty rigorous, with quoted significance levels rather than mere correlation values, and distributional tests on the residuals – specifically the Durbin-Watson test, which can detect missed low frequency effects as well as true serial correlation. And there are still papers published which use the bounds on DW significance rather than calculating the exact value as per my thesis of 40 years ago. To allow others to benefit from these calculations, ‘R’ code for them may be found in the SI.
    I intend to add more to this summary in the near future, but for now the bottom line is:
    There is a statistically valid effect from solar cycle variation on global temperature.

  28. These ceteris parabus ( all other factors being equal) studies are all well and good, but there seems to be s lack of awareness by climate researchers of the obvious time limitations on their possible usefulness (centennial scale).
    We know with certainty that during periods in the past, temperatures rose rapidly with low unchanging levels of CO2 or fell during rising levels. Ice cores indicate that rising temperatures preceded rising CO2. Had we nice time series for such periods, we would be unlikely to expend time and money worrying about ECS of CO2 and if we did, we would arrive at ECS figures of colossal values both positive and negative!
    This means certain non-CO2 drivers of T over longer periods greatly overwhelm the clearly modest effect that CO2 may have when the Big Movers are quiet.
    Even with the centennial series, we get 30yr cooling reversals that much of Climate research has spent trying to erase because it’s implications for the mission are too terrible for them to contemplate . Homogenizing is an unfortunate revealing term. You could put the Amazon rain forest through a wood chipper and say we really didn’t change the essentials.
    All climate researchers know this fact but put this CO2 stuff out as if it occupies a central place over earth temperature history.

  29. 1. Note: the myth of “gatekeeping” contrary findings is busted.
    2. Note: Nic and Judith did not have to question known science ( c02 IS a ghg ) to establish a skeptical
    3. Note: They didnt have to slur people and accuse them of fraud to establish a skeptical position.
    4. Note: they didnt have to rely on the weak argument that warming might be caused by “something else”
    5. Note: They established a skeptical position from WITHIN the framework of accepted science.
    6. Note: No need to misrepresent the working done on observations.
    As I explained years ago the most effective way of challenging the science.. is…
    Do science and publish it.
    And to be really effective do it within the framework of existing science.
    no sun nuttery required. No political attacks required. No claims of fraud or hoax required.
    no grade school Monktonesque “we win, you lose” buffonery required.
    Now imagine if ALL the skeptical energy were focused on the problem Nic has been talking about.

    • There is no doubt, Stephen Mosher is a good person. He cares enough about this topic that he comes back here again trying to help the rest of us despite the fact that he gets called out every time he posts.
      Mosher is one the good guys. Trying to make society a better place. He has probably always been this kind of good moral person but also one who has mad skills.
      Now, he hasn’t made a lot of headway with us skeptics. Maybe he is wasting his valuable skills trying to make us understand.
      You know, maybe his logic and math skills could make a lot of money in the stock market instead, building up a cool retirement fund.

      • The correct answer is
        “no one knows what ECS or TCS is”,
        and no one may ever know in our lifetimes.
        But the wild guessing
        ( educated guessing? )
        will never stop.
        I’m happy that the ECS / TCS
        estimates by scientists have been
        in a downward trend for a long time.
        For many years it seemed like
        climate “science” was nothing more
        than extrapolating the warming
        in the 1990s.
        I suppose it still is for the corrupt IPCC,
        whose published numbers are
        apparently carved in stone (since 1979),
        3.0 +/- 1.5 degrees C.,
        and it seems those IPCC numbers
        won’t ever change
        even if Chicago and Detroit
        were covered by ice again,
        like they were 20,000 years ago !
        The best we can do for now is
        to make an assumption
        that ALL warming after 1975
        was caused by CO2,
        to create a worst case
        TCS estimate.
        Unfortunately there are no global
        surface data — too much infilling
        (still true today) and too little
        Southern Hemisphere data (before 1940)
        … but there is near global
        data from weather satellites,
        with far less infilling, which
        are verified by similar data
        from weather balloons.
        The era of man made CO2 is after 1940,
        but we can live without 1940 to 1975 data,
        when cooling was claimed, per surface data.
        All of the known post-1940 warming was
        after 1975.
        Fortunately, we have satellite data
        since 1979 — so we can assume ALL
        warming since 1979 was caused ONLY
        by CO2, and if we so that
        worst case TCS would be about 1.
        And that means CO2 is harmless,
        even in a worst case situation where
        we assume only CO2, and nothing else,
        caused the warming since 1979.
        Once you have that estimate of worst case
        TCS, any complicated attempt to create a “better”
        TCS estimate is likely to be a waste of time,
        especially because there are no accurate global
        temperature data before 1979.
        Some so-called “scientists”
        try to impress people
        by estimating TCS or ECS in
        in tenths or hundredths of a degree C.
        per CO2 doubling = that’s false precision.
        The TCS / ECS wild guessing
        is not likely to stop
        because it serves a purpose:
        — Getting attention for scientists
        who need to publish to justify
        their salary (or their “expertise”).
        A smart scientist would say
        “I don’t know TCS or ECS,
        but it must be low
        because there’s no evidence
        CO2 is harmful, and much evidence
        CO2 is beneficial”,
        … but I don’t hear that much,
        so I have to assume
        there are not that many smart
        scientists out there who are adding
        anything of value to real climate science
        (as opposed to fake climate science,
        where government bureaucrats
        with science degrees play
        computer games all day
        and make wrong climate forecasts
        … for 30 years so far ! ).
        Sometimes the smartest person
        in the room is the one who says
        “I don’t know”, or
        “No one knows
        what TCS or ECS is”.
        My own climate blog
        with over 16,000 page views:

    • 4. Note: they didnt have to rely on the weak argument that warming might be caused by “something else”

      ECS of 1.66 means that the observed warming in the second half of the 20th century was primarily caused by something else. QED

    • Mosh,
      1. One need only be regular reader of Science and Nature to know that Gatekeeping is alive and well.
      2. Lewis and Curry, 2018 maintain the possibility of higher bound of ECS to 2.7 K. Political correct and thus acceptable.
      3. It is Mann who slurs Curry. The push-back from her peanut gallery defenders is justified, as Mann, Jones, et al are proven Liars by any objective assessment. Even you must know they are liars and hucksters.
      4. “something else” is internal dynamical variability of the climate system that even Gavin S. acknowledges the models do not properly capture. No one actually knows what the real warming contribution of CO2 versus internal variability is. The IPCC pulled mostly (or majority) out of their collective ass.
      5. Judith was driven out her faculty position and loss of funding by the “accepted framework”. Nuff said.
      6. The observations (manipulated by infilling and homogenizations) are a separate topic. What is clear is surface temperature data sets do not adequately account for modern day UHI and loss of rural stations.
      And yes, do science (little “s”). It is a method. Not a thing that must be defended like the rent-seeking partisans at the AAAS and Science (big “S” ) would like the public to believe.

    • …sun nuttery…
      This coming from a man who calls svalgaard his go to guy on solar. Hey Mosh, are you aware that your go to guy doesn’t think that the oceans are warming? (you’re gonna look pretty stupid standing next to that guy on climate change judgement day)…

    • Note: Mr. Mosher Wanders in the Weeds and comes up with banalities. He can’t even build straw men well.
      What the hell happened to the Chinese Bitcoin mining equipment venture?

  30. I think we can just accept that people who care about Mother Earth, the animals, and global warming are good people. I mean they are the best of people.
    We note they are very good people and care about the Earth we are leaving to our grandchildren and future generations. The people that care about this are just really good people.
    They are so good that they should volunteer and doing other good things which have more immediate impact.
    Focussing so much of their valuable attention on this very complicated theory about the quantum impacts of the diatomic molecule of CO2 in a gaseous atmosphere is not worth as much as volunteering and donating. They are very good people and they could put this virtue into things that have more impact than the complicated qauntum science theory of CO2.

  31. I believe that the idea that adding CO2 to the atmosphere causes warming is hard coded in which totally begs the question as to whether CO2 causes warming and how bad will that warming be. These simulations are no more than a sophisticated form of make believe. There is no real evidence that CO2 has any effect on climate and plenty of scientific rational to support the idea that the climate sensitivity of CO2 os zero.

    • “plenty of scientific rationale to support the idea that the climate sensitivity of CO2 is zero”.
      But there aren’t many peer reviewed papers which support that statement. The physics of greenhouse gases shows that without water and CO2 the Earth would be a lot (~30K) colder. It is just possible that the interaction of the major GHG water with the minor GHG CO2 totally annihilates the latter. But AFAIK no-one has proved this. Therefore the (wicked) question remains “how much effect does CO2 have?”.
      My paper cited above assumes that the HadCRUT4 temperature record is uncontaminated by UHI and that there is no “natural rebound” from the LIA, both of which, despite what Mosher says, are dubious assumptions. I shall be happy to see papers that establish bounds on both of those two things, and then I’ll be able to refine my model and climate sensitivity which, for now, remains pleasantly lukewarm.

      • R. J. Booth
        If you look at the surface temperature data
        since 1900, there is nothing different
        or unusual in the second half of the 20th century,
        when compared to the first half of the 20th century.
        That’s means there is no evidence
        in the average temperature compilations
        that manmade CO2 (after 1940)
        did anything to the average temperature that
        could not have had natural causes.
        But … if you believe the lab experiments
        showing that CO2 is a “greenhouse gas”,
        then it should cause some warming,
        but if it does, there is no way to
        distinguish between the natural warming trend
        in the first half of the 20th century,
        not caused by CO2, and the similar warming trend
        in the second half of the 20th century.
        So the temperature evidence,
        and I know the data are low quality,
        tell us TCS must be so low that we can’t distinguish
        between one half century with little man made CO2
        and the later half of the same century
        with lots of man made CO2.
        CO2 is at worst harmless,
        concerning night time warming,
        and at best very beneficial
        concerning greening our planet

        • The only way to get high ECS estimates is to play with historical aerosol amounts. Until the IPCC or CMIP organizations demand consistent estimates of historical aerosol forcings, models are bunk.

  32. There is a big problem with this. If it’s true that sensitivities are lower than being used in the models then how can people be frightened into going along with the GW/CC agenda?

  33. There is no need to fool everyone. Just give a few what they want and they will scare the rest.
    Isaac Newton produced almost as much religious writing as went into his Principia. One of the human indelible human traits he noted in his religious notes was the inveterate human fondness for superstition. The ancient Egyptian although lacking the “shoulders of giants to stand on,” like Newton, had a strikingly advanced science, including knowledge that the Sun was a star and that the planets, including Earth, orbited it. They surmised that all other stars had planetary systems, too. The Egyptian educated and priestly classes also had a very abstract religion consonant with their scientific understanding. For commoners, however, the priestly elite provided a multitude of pagan animal gods and relics to worship. In the introductory chapter of his “Heaven and Earth,”
    Ian Plimer called AGW an urban atheistic religion very like a fundamentalism. No doubt it satisfies the need in some people for a superstitious pagan belief, but it also seems to attract people capable of a fanatical devotion bordering occasionally on the psychotic. I imagine any of the skeptical website hosts could exhibit several volumes of hate from their email.

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