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Back To School For Baroness Verma

October 28, 2014

By Paul Homewood  


All you need to know about the relationship between annual CO2 emissions and global temperatures. 



  1. Joe Public permalink
    October 28, 2014 1:02 pm

    Hi Paul

    Why is the start date the relatively-recent 2001?

    Ed Hawkins’ graph goes back to 1950.

    • October 28, 2014 1:08 pm

      I have picked 2001, as there has been no warming since then.

    • David permalink
      October 28, 2014 4:31 pm

      The view that global surface temperatures rise in lock-step with CO2 over short periods isn’t supported by the IPCC. AR5 SPM states “global mean surface temperature exhibits substantial decadal and interannual variability… trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long term trends.”

      There are several continuous 13-year periods in HadCRUT4 since 1950 during which the rate of temperature rise slowed or cooled, whilst CO2 concentrations grew. However, there is a statistically significant (+99%) correlation between CO2 concentrations and global temperature increase over the long term:

      • October 28, 2014 6:02 pm

        I don’t see any 99% correlation at all. Sure the lines both go up at a similar rate, but that depends on the scale used.

        I note you start from 1958. You would get a totally different result if you went, say, from 1930 to 1975.


        In the meantime, I suggest we suspend all further economy wrecking measures until the temperatures catch up with the model forecasts.

      • David permalink
        October 29, 2014 4:44 pm


        The +99% correlation comes from P (2-sided) correlation analysis. I used the package that comes with Excel (needs to be activated separately). A table of correlation coefficient values determines significance levels based on sample size (n).

        In this case n=677 (Jan 1958-Sep 2014; CO2 ppm vrs HadCRUT4 temp anomaly deg C). The correlation coefficient value where n > 500 is 0.115 at the +99% confidence interval. Since 0.842 is much higher than 0.115, the correlation between CO2 ppm and HadCRUT4 temps since 1958 is significant at +99%.

        That is NOT to say that one causes the other.

      • October 29, 2014 5:14 pm

        And what would you get if you started from, say, 1930?

        (Yes, I know Mauna Loa does not go back that far!)

        Or, for that matter, since 1998?

  2. Retired Dave permalink
    October 28, 2014 2:00 pm

    The Potentate will have to wander around garmentless for quite a while yet.

    The theory of AGW has little other than some circumstantial evidence to back it up and 25 years of no empirical evidence to support it, coupled with much that leads on one to sceptism.

    BUT with constant drip feed of misinformation it will take a good few years yet before sense and science returns.

    A good example of the low level drivel we get is an article in the latest National Trust magazine which recycles the same old melting sea ice as evidence of climate change.

    As for Baroness Verma!! My mother taught me that if you can’t say anything nice………..

  3. John F. Hultquist permalink
    October 28, 2014 4:05 pm

    Retired Dave’s reference to “little other than circumstantial evidence” can be clarified:
    ~~ A. There is the bit about gas of radiative capability with contributions by humans – that’s the “little” part;
    ~~ B. The chart linked to by Joe P. (Ed Hawkins’ graph) does go back far enough to show the “circumstantial evidence”, namely the period from about 1975 to 1999 (+ or – ) when CO2 and temperatures (adjusted and homogenized) rose.

    Paul says “there has been no warming since then.” Thus, a person has to be age 15 to have been alive during “the warming” and 25 or 30 to have awareness of the period.

    This doesn’t get said often enough: Thanks Paul.

    • David permalink
      October 28, 2014 4:56 pm

      Take another look at Ed Hawkins’ graph John. Hawkins produced the IPCC ranges and added the temperature data, which is scaled on the right.

      The CO2 data was added to Hawkins’ graph. It isn’t scaled and gives the impression that there is no correlation between CO2 emissions and temperatures. In fact, they are closely correlated over the longer term (>99% confidence).

      To ‘normalise’ both data sets for a fair graphical comparison, individual vertical axes are required. WfTs does this automatically when you select the ‘normalise’ function for CO2. Note the difference that normalisation makes:

      • David permalink
        October 28, 2014 5:23 pm


        The reason the temperature data appears unrelated to the CO2 data in the Hawkins (really WSJ) graph is that the range in the observed temperature data is just -0.3 to +0.6; whereas the temperature scale rises to 2.0 (because it’s extrapolating temperatures out to 2100). This has the effect of keeping the temperature data low relative to the right hand scale.

        The CO2 line on the other hand uses the whole of the vertical temperature scale, *even though it’s not based on that scale*. This gives the impression that CO2 emissions have risen massively faster than temperatures over the long term, which, when compared on a relative scale, they have not.

      • Retired Dave permalink
        October 28, 2014 5:55 pm

        The fact remains that during the pause of 15 years and counting 25% plus of all the CO2 emitted by man has been added to the atmosphere. This is very inconvenient for the AGW thoery. After all CO2 molecules either absorb and re-rediate heat or they don’t. They can’t hang on to it for a bit and no hot spot as per models anyway.

        GCM assume that CO2 has a close to black body response, but recent lab work suggests that this is far from being the case.

        The work has been published.

        Unfortunately if Dr. Robitaille is right it may invalidate the Stefan-Boltzmann argument refered to in NZrobin’s comment above.

      • David permalink
        October 29, 2014 4:57 pm

        Retired Dave

        I agree that the pause since 2001 requires an explanation. If the IPCC analysis is correct, then warming will pick up again, if it hasn’t already done so; i.e. if the strong warming seen over the past 3 years in all data sets continues.

        I would also agree that many on the warming side were taken aback by the extent of the pause since 2001. Perhaps insufficient consideration was given to the power of natural variability in climate.

        However I think the efficacy of CO2 as a powerful and long lived greenhouse gas in the atmosphere is well established.

      • October 29, 2014 5:24 pm


        There seems to be a lack of understanding of the position of most sceptics here.

        Most accept CO2 has a GHG effect. The whole issue is how much.

        More and more the evidence points to it being much, much less than the IPCC and models have been predicting. As such, there are enormous implications for public policy.

        BTW – when you say “strong warming seen over the past 3 years”, I trust you realise you have just begun from the big La Nina – only saying!

  4. nzrobin permalink
    October 28, 2014 4:48 pm

    Hi Paul, take a look at my recent post at Kiwithinker.
    Cheers from NZ.


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