1970s-’80s ‘Physics’ Said Doubling CO2 Produced Just 0.2°C – 0.8°C Warming. Then ‘Physics’ Changed.

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Forty to 50 years ago there was “general agreement” in estimates of the resulting radiative forcing (1 to 2 W/m²) and surface temperature change (0.5°C ±0.3°C) when directly doubling CO2 concentrations from 280 to 560 ppm. By the late 1980s the “consensus” estimates doubled to 3.7 W/m² forcing and 1.2°C warming instead. Apparently “basic physics” changed.

It is today considered IPCC-endorsed “settled science” that doubling CO2 concentrations from their preindustrial value (280 ppm to 560 ppm) directly leads to a temperature change of 1.2°C without the alleged positive feedbacks with water vapor and clouds to amplify this warming further.

Image Source: SkepticalScience and IPCC (2001)

As recently as the early 1980s, however, the “general agreement amongst different modelers” put the global surface temperature change resulting from doubling CO2 “between 0.2 and 0.4K.”

Image Source: Schuurman, 1983

In 1984 Andrew Lacis – the scientist who later claimed CO2 is the Earth’s temperature control knob  – co-authored a paper that put the radiative forcing response to doubling CO2 at “only 1 – 2 W/m²” , which is the temperature equivalent of between about 0.2 and 0.8°C.

Image Source: Fung et al., 1984

Again, 1 to 2 W/m² and 0.2 to 0.8°C were the norm for the no-feedback climate sensitivity estimates throughout the 1970s and first half of the 1980s, or before the “consensus” opinion doubled these values in the late-1980s.

Here are some examples.

Newell and Dopplick, 1979 (2x CO2 = 0.8 to 1.5 W/m² or <0.25°C )

Ramanathan, 1981 (2x CO2 = 1.2 W/m² or 0.4°C)

Idso, 1980 (2x CO2 = 2.28 W/m² or ≤0.26°C )

Zdunkowski et al., 1975  (2x CO2 = 0.3 to 0.4°C, 7x CO2 = ~1°C)

Gates et al., 1981 (2x CO2 = 0.3°C, 4x CO2 = 0.48°C)

In the early 1970s, it was also the “consensus” that the spectral band where CO2 exerts its radiative effect is saturated or nearly so, which means diminished warming the more CO2 rises. Thus, multiplying CO2 by a factor of 6 or 8 will still produce less than 2°C warming.

Weare and Snell, 1974 (2x CO2 = 0.7°C, 6x CO2 = 1.7°C)

Rasool and Schneider, 1971  2XCO2 = 0.8°C, 8xCO2 = <2°C

Low climate sensitivity estimates became a problem for those wishing to portray CO2 as much more influential variable. By the mid-1980s it became more and more acceptable to say doubling CO2 produces a forcing of 3.7 W/m² and a warming of 1.2°C. And to this day these values are assumed to be “basic physics.”

Image Source: Seinfeld, 2008
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16 responses to “1970s-’80s ‘Physics’ Said Doubling CO2 Produced Just 0.2°C – 0.8°C Warming. Then ‘Physics’ Changed.”

  1. Richard Greene

    I have carefully compiled and averaged all of the TCR and ECR estimates over the past 50 years, and have the obvious conclusion for readers:

    (1) No one knows exactly what CO2 does in the atmosphere.

    (2) Everyone has an opinion they will usually state with great confidence.

    (3) Sometimes the opinion is stated with hand waving and hysteria, which is very exciting, and tends to be covered in the mass media.

    Meanwhile, everyone has lived with some of the ACTUAL climate change in the past 88 years, as CO2 levels rose from the trough of the Great Depression business slowdown in 1932.

    Even if you data mine, and focus ONLY on the global warming trend since 1975, it is obvious that the warming was mild and harmless, at worst.

    Beneficial warming if you consider where
    and when the most warming has been measured by satellites since 1985:
    The Northern half of the Northern Hemisphere, mainly in the six coldest months of the year, and mainly at night.

    Think of warmer winter nights in Siberia.
    That’s a climate emergency?
    I’d say it was good news.

    Along with good news for everyone:
    Greening of our planet from more CO2 in the atmosphere.

    So reality was pleasant climate change.

    Only the predictions have been for rapid, dangerous climate change — predictions that began in 1957, with oceanographer Roger Revelle.

    So it seems a climate crisis has been coming in 10 or 20 years …
    for the past 64 years !

    Did it get lost on the way?

    Meanwhile, the current climate is wonderful (a little cold in 2021, but hopefully warming will resume), so we should be celebrating the current climate … yet many people are miserable — fearful about the future climate.

    And every bad weather event, which has nothing to do with climate change, scares them even more.

    What’s wrong with these climate alarmists?

    Is there a cure?

  2. ralfellis

    I myself believe that Chinese industrial pollution and resulting ice sheet albedo reductions may play a large role, but the scientists pursuing Dark Ice research have been unable to gain further funding. Nevertheless, the sparse data available does suggest that Arctic ice sheet loss may be due to dust-albedo reductions, which would in turn result in regional insolation absorption and warming across the high northern latitudes. If this is true then mitigating CO2 emissions would be a complete waste of time and money; but very little research is being done in this field because everyone has jumped upon the CO2 bandwagon.

    Ice Sheet and glacial Mass Loss.


  3. oebele bruinsma

    May be this contributes to our understanding of trends in the climate: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7575229/

    1. Richard Greene

      I would like to add that Russian scientists are always interesting, and they do have the most accurate climate model (INM), which over predicts global warming the least

      … but Russian scientists have been calling for a global cooling trend since about 2005.

      From what we know, through 2020, it appears to be yet another wrong climate prediction.

      Of course our planet is either warming, or cooling,
      so there’s always a possibility of being right.

      My own climate predictions, made in 1997, have been 100% accurate:
      January will be cold (Northern Hemisphere)
      July will be warm (N.H.)
      The global average temperature will get warmer,
      unless it gets cooler.

      I have ignored all climate predictions since my own in 1997.
      They seem no better than flipping a coin.
      Maybe worse.

  4. John F Hultquist

    “Apparently “basic physics” changed.”

    I submit this issue isn’t “basic physics” but is more akin to investigating an unknown value of a complex action.
    Many unknows were estimated, and then changed, and changed again as study of the issue continued. The age of Earth is an example. See:

    Basic physics was jolted and subsequently changed when in 1900, the German physicist Max Planck (1858–1947) explained the ultraviolet catastrophe by proposing that the energy of electromagnetic waves is quantized rather than continuous.

  5. Tom Anderson

    Richard Greene: “What’s wrong with these climate alarmists? … Is there a cure?” No, ignorance can be cured, stupidity cannot, nor, apparently, can well compensated mendacity. A lie is a lie whether simple or richly embellished.

    Omitted from the discussion are studies pointing out that on all observed time scales CO2 concentrations FOLLOW temperature change – by 800 years ±200 in the Vostok fossil record, Jaworowski, et al., 1992, and in current time by 9.5 to 12 months in a study by Humlum, O., Stordahl, K., and Solheim, J-E in Global and Planetary Change, v. 107, Aug. 2013, pp. 226–228.

    Causes must precede effects, with no exceptions for doctrinal purity. CO2 causes nothing.

    Further, CO2, like any radiatively interactive substance does not absorb the entire spectrum of solar irradiance. It is a “spectral line absorber and emitter,” responding to set quantum-determined levels of energy, which has long been used for photospecrometric identification of materials.

    Warming? A recent study, simply using Wilhelm Wien’s constant, or Wien’s Approximation, has determined that CO2’s maximum interaction with solar irradiance is that 99.83% of the photons absorbed are around the 15 μm band (13-17μm)at a ~15μm peak wavelength covering a range from ~13μm to ~17μm at 193.13K. that is, peaking at -79.87°C. (Witteman, W.J., “The absorption of thermal emitted radiation by CO2,” April 3, 2020.) It is so stated in Salby, Murry L., Physics of the atmosphere and climate (New York, Cambridge Univ., 2012), p. 213.

    That is 80 Celsius degrees below water’s freezing point. It has been much ado about a god deal less than nothing. How is it we are still debating?

    1. Chris Hanley

      Climate is a complex system with feedback loops, CO2 can be both cause and effect.

      1. Richard Greene

        In the 4.5 billion years of Earth’s history, we ONLY have evidence of strong positive correlation between CO2 levels and the global average temperature from 1975 to 2002, and from mid-2015 to mid-2021. Dates mat vary slightly with different choices of global average temperature compilations.

        Those periods are a tiny percentage of Earth’s history.

        And correlation is not causation.

        That adds up to very little evidence that CO2 is the temperature “control knob”.

        And if you consider the mild, harmless global warming in the past 45 years, there is zero evidence that CO2 levels rising 2 ppm a year are dangerous in any way.

        The declaration of a climate emergency is science-free propaganda.

        We should be celebrating the current moderate, wonderful climate.

        Not spending a huge amount of money to replace a reliable electric grid with an unreliable electric grid powered by sun and wind.

        While ignoring real problems, such as air pollution over Asian cities and one billion poor people with no electricity.

        1. Chris Hanley

          Richard: I don’t believe correlation = causation, nor CO2 is the climate ‘control knob’, nor rising CO2 atmospheric concentration is dangerous, nor that there is currently a climate emergency, nor RE can possibly provide necessary affordable energy for any country at any stage of development.

          1. Richard Greene

            That means you are smart, and not gullible.
            And not a believer in wild guess climate predictions of doom.

            We will have to report you to the authorities
            for climate change re-education.

            To learn that:
            CO2 is a satanic gas — the devil in the sky,

            the IPCC Summary for Policymakers is your bible,

            and John Kerry is your pope.

            You will also learn important “scientific” phrases, such as:

            ” Carbon pollution is killing millions of people”

            “You are a climate denier”

            “You are a science denier”

            “97% of scientists say … ”

            “That prediction is from peer reviewed study published in a prestigious science journal, so it must be right.

            “We are trying to save the planet for the children — don’t you care about children”

    2. Tom Anderson

      Seldom if ever mentioned in the debate is the warming hypothesis’s free pass from the laws of thermodynamics. Physicists appear strangely absent from the debate. It almost entirely surrounds how much a trace gas, by interacting with solar irradiance at its quantum energy levels, can cause an increase of the energy entering it, such that it makes more energy. There was a brief exchange in Anthony Watts’s page about a physicist’s thought experiment of a radiantly active molecule transferring its energy to an a nearby non-radiant molecule, raising it thereby it to an exactly equivalent level of mechanical energy. The discussion that followed wound blindly through every tortured excuse for how CO2s emitted energy transformed somehow to “excite” many more non-radiant neighbors by a supposed necessarily “super-charged” release.

      That is balderdash. The basic premise of the “danger” ignores the First Law of Thermodynamics: No process can create or destroy energy but can merely change its form. Believing otherwise allows leads eventually to “perpetual motion.”

      Good scientists, physicists or not, should know that. CO2 is a TRANSMITTER of energy but not, in any manner or quantity a SOURCE of energy. The sun is our only source of energy (barring trivial geothermal and extraterrestrial contributions). All the other refutations of CAGW, true or not, are welcome, if superfluous.

  6. Tom Anderson

    Needs editing. “leads eventually to.” and “emitted energy is transformed.”

    1. Tom Anderson

      Dear Moderator: I see my comment on the thermodynamic inconsistency of global warming has been removed. That is a great pity. Skeptics will never prevail until they turn to the limits thermodynamic places on any form of heat transfer, because it is suppressed here. Only one website I have ever seen has explored the issue in detail. Its physics, judging from basic texts on the subject confirm what other sites ignore. Only Judith Curry in her Climate Etc. expressed a wish to understand thermodynamics better. Meanwhile our debate is a hopelessly broken record in a ptolemaic universe, with fixed continents.

  7. Derek Colman

    I read an article some time back about a pair of scientists who set out to replicate the work of Svante Arrhenius by carrying out his experiments.They got a result of 0.2K for a doubling of CO2. Doubting that result they repeated it hundreds of times while changing as many things as they could think of, but always getting the same result. They also noted that Arrhenius’s result was the same as for water vapour. Then they approached other scientists for suggestions of better methods and tried them out. Still they got the 0.2K result. I tried to follow it up to find out if their paper was published but drew a blank with Google and Duckduckgo, and also with the original article. The difference I could see was that Arrhenius would have had to make his own CO2, whereas these guys probably bought laboratory grade CO2 which was dry and near 100% pure. Was Arrhenius using CO2 contaminated with water? Compressed air for paint spraying has to have water extracted, so did Arrhenius inadvertently err by not drying his home made CO2?

  8. Weekly Climate and Energy News Roundup #464 – Watts Up With That?

    […] 1970s-’80s ‘Physics’ Said Doubling CO2 Produced Just 0.2°C – 0.8°C Warming… […]

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