Skeptical Science : Climate Sensitivity – Negative

John Cook responded to my “Hokey Stick” post with this comment :

I don’t do any climate sensitivity calculations in this post. I’ve cited Hegerl 2000 which uses proxy data (not instrumental data) over the last 750 years to calculate a best guess climate sensitivity of around 3 degrees C.

Fair enough – let’s test that theory out on Cook’s graph :

First step, we will remove the instrumental data (red) since it isn’t being used.

Now, let’s do the math.

One thousand years ago, CO2 was about 260 ppm. By 1960, it was 317 ppm – a gain of 57 ppm. From Cook’s paleoclimate graph above, temperatures declined about 0.2C over that same period. The climate sensitivity for a doubling of  pre-industrial values (280 ppm) is therefore :

(-0.2 degrees C / 57 ppm CO2) * 280 ppm = -1 C





About stevengoddard

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35 Responses to Skeptical Science : Climate Sensitivity – Negative

  1. glacierman says:

    I knew the sign was negative. Now we have proof. Thanks John.

  2. James Sexton says:

    lol, nice Steve! I thought I was feeling cooler lately!

  3. PJB says:

    Does this mean that we can exhale, now?

  4. Espen says:

    Don’t give the alarmists ideas! I can already see the headlines: “Climate disruption may set off next ice age!”.

    (but you forgot that the CO2 cooling is logarithmic, so the sensitivity is just -0.7!)

  5. J says:

    Hey Steve! Your results are way off. Heres some proof:
    From 1940 to 1970 temperatures fell 0.2K (on the adjusted, homogenized and tortured data). On the same period, CO2 rose from 300ppm to 325ppm.

    5.35 ln (325/300) = 0,43 Watts per sqm
    0.43 Wm-2/-0.2K = -2,15 W/m2K
    Therefore doubling the concentration would cause 1,7K cooling, and propably
    the decline from 40’s was way stronger, so this would represent the lowest
    estimate on global cooling.

    Ice age is ahead!

    • Brendon says:

      Yes well pointed out.

      Steve’s method of calculating sensitivity is flawed because you could pick any two dates between 1000 and 1800 and come up with all sorts of figures.

      And he needs to consider all forcing during the period, not just that of CO2.

      • Brendon,

        You do realize how ridiculous your arguments are.

        1. I’m using the entire data set. That is obviously the most appropriate thing to do in this case.

        2. You are arguing that natural variability is greater than changes in CO2, which undermines everything else you believe about this.

      • MikeA says:

        Crikey Brendon lighten up, it’s only a joke!

  6. If we unhide the decline of Briffa’s tree, we can make it really, really cold!

  7. Airframe Eng says:

    Brendon is apparently ruminating in the corner he painted himself into.

    Will cognitive dissonance lead him to epiphany? Or shall blind faith prevail once again?

  8. Jean Rochefort says:

    “Best guess” sensitivity -1°C.

  9. Lazarus says:

    “I’m using the entire data set. That is obviously the most appropriate thing to do in this case.”

    No it isn’t because the CO2 increase that is the subject of determining sensitivity did not rise evenly over that period of the data set. What you have done is a bit like working out an athletes time for the 100m by starting your stopwatch when he starts to get his kit on.

    Care to do you calculation from the start of the industrial revolution, say around 1800?

  10. Piers Corbyn says:

    The observed data over the last 500, 5000, 5million or 500million years shows that in the real atmosphere and biosphere of the earth CO2 does NOT drive weather or climate; indeed on time scales of around 1000 years CO2 is driven by temperatures – by eg warming oceans emitting more CO2 in a delayed manner. The CO2 climate driver theory is a political scam.
    For evidence – and a bit about WHY CO2 doesn’t do what is claimed (if that matters), see “Global Cooling has…. ” (particularly REDBOLD items in COMMENTS such as Presentation WAnews27) on Climate Realists –

    Thanks, Piers Corbyn

  11. Lazarus says:

    “The CO2 climate driver theory is a political scam.”

    Piers, it is well established and basic physics. Co2 variation changes the thermal properties of air and can be demonstrated with experiments school boys can do. These is no reason to believe that the basic physics shown in these experiments will be different out of the lab. Tyndall, Fourier and Arrhenius were not politicians.

  12. Rob Honeycutt says:

    Steve… Again you’re over simplifying. You are taking a temp proxy and applying it to CO2 as if there were absolutely no other influences on the climate. You are using 1960 as your end date but what you ignore is, for one, aerosol cooling effects of 1940 to 1970. I’d pull your CO2 figures back to at least 1940 or earlier to get a better reading on climate sensitivity. Then after than you need to look at solar influences over that period. And there are going to be very many other factors to include if you really want to get to the truth of the matter.

    • Here is a much better explanation :

    • Rob Honeycutt says:

      Steve… I’m quite familiar with the dynamics of the ENSO. What you are not doing is accounting for the additional heat. You are stating the inter-decadal heat exchanges related to ENSO. You are not addressing the trend that you’re presenting in the chart by relating ENSO to HadCRU.

      • Right now ocean SST’s are well below normal. What caused that?

      • Rob Honeycutt says:

        You’re avoiding my question but I’ll answer. STT’s are doing because we’re in a La Nina cycle. But you’re comparing global temps to the ENSO and suggesting there is a causal relationship. I’m saying in both charts there has to be a mechanism for the increased heat energy.

        So, back to my original question. Where is the heat coming from? What is driving the warming trend in both of these instances? If it’s the sun there has to be increased irradiance and you know over the past 30 years we don’t see a correlation between solar irradiance and warming.

        So what is it? Where is the increased heat energy coming from?

      • Rob Honeycutt says:

        “doing” was supposed to be “going down.”

  13. Mike Davis says:

    There are only 2 sources of heat. Solar and Geothermal!
    Rather than ask where the ENSO gets is heat from you should be wondering what restricts the ENSO from going into a rumaway mode, Either positive or negative. To answer that you would want to research what restricts the PDO from reaching critical mass or the other portion of the Pacific ocean, ocean / atmosphere weather pattern the SOI.
    Searching for those answers is like searching for the Holy Grail, The Elixir of Life, The Fountain of Youth, or The Meaning of Life. Good luck in your journey as there are a lot of false paths that lead to increasing your ignorance.

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