The Chicken or the Egg?

Climate scientists assert that increasing concentrations of carbon dioxide and other greenhouse gases in the atmosphere have caused and will continue to cause global temperature to increase.  Real world evidence to support this is sadly lacking.

I use CO2 data from NOAA at Mauna Loa and HadSST3  Sea Surface data to compare both over the same period, as oceans cover most of global surface.

There have been 60 years of continued and accelerating CO2 increase.

Figure 1: 60 years of carbon dioxide concentration

CO2 abs trend

Ocean temperatures have also increased:

Figure 2:  HadSST3 Sea Surface Temperature from 1958


While you may note the distinct lack of warming before the mid 1970s, and that although a quadratic trend line fits the data, the increase is not smooth but a series of steps with some large spikes at about the time of ENSO events, climate scientists insist that it is the overall trend that is important.

The following plot appears to support the greenhouse warming theory.

Figure 3:  Global Sea Surface Temperature anomalies as a function of CO2 concentration

SST vs CO2

It seems that nearly three quarters of the temperature change since 1958 can be explained by the increase in CO2 concentration.  This accords with the theory.

But what if we reverse the axes in Figure 3?

Figure 4:  CO2 concentration as a function of Sea Surface Temperature anomalies

CO2 vs SST

It is equally valid to propose that nearly three quarters of the increase in carbon dioxide concentration can be explained by increasing sea surface temperatures, although that is not the point of this exercise.

To determine if CO2 is the cause of increasing temperature, or vice versa, we need to compare SST anomalies and CO2 concentration as a function of time.  If SST and CO2 both change at the same time, we are no further advanced, but if CO2 changes before SST (due to thermal inertia of the oceans), then that would be evidence for CO2 increase being the driver of temperature increase.

Both CO2 concentration and SST anomalies have pronounced trends, so for comparison both datasets are detrended, and the large seasonal signal is removed from CO2 data to calculate monthly “anomalies”.

Remember, it is increasing CO2 which is supposed to cause increasing temperature, not a static amount, so change in CO2 and SST must be our focus.

My measure of change in SST and CO2 is 12 monthly difference: for example January 2000 minus January 1999.  The next plot shows 12 monthly difference in both SST and CO2 anomalies from 1959 to 2018.  (SST is scaled up for comparison).

Figure 5:  12 monthly change in detrended SST and CO2 anomalies

12m chg Hadsst3 co2

SST appears to spike before CO2.  In the next plot, SST data have been lagged by seven months:

Figure 6:  12 monthly change in detrended SST (lagged 7 months) and CO2 anomalies

lagged 7m 12m chg Hadsst3 co2

There appear to be differences in some decades- the lag time varies from four months to eight or nine months.

Here’s the plot of CO2 vs lagged SST:

Figure 7:  12 month change in CO2 as a function of 12 month change in SST, lagged 7 months

lagged 12m SST vs CO2

Correlation co-efficient of 0.57 is not bad considering we are comparing all ocean basins and the atmosphere.

As SST change generally precedes CO2 change by about seven months (sometimes less, sometimes more), there is NO evidence that CO2 increase causes temperature increase.

But we are still left with the increase in CO2 from 1958 while SST paused or decreased for 19 years.

Figure 8:  Sea Surface Temperature and CO2 concentration, 1958-1976

Hadsst and CO2 58 76

While it is difficult to attribute decadal CO2 increase to non-existent SST rise, there is no evidence for CO2 driving temperature increase in this period.

However, plotting 12 month change of CO2 and SST clearly reveals their relationship.

Figure 9: 12 month change in detrended CO2 and SST anomalies

12m chg Hadsst and CO2 58 76

Figure 10: 12 month change in detrended CO2 and SST anomalies, lagged 7 months

lagged 12m chg Hadsst and CO2 58 76

It is clear that 12 monthly change in temperature drives 12 monthly change in CO2 concentration.

The continual rise in CO2 from 1958 to 1976 while SST declined indicates there must be an underlying increase in CO2 unrelated to immediately preceding temperature, but there is definitely no evidence that it causes sea surface temperature increase at any time.


  1. Increase in CO2 concentration is supposed to be the cause of the increase in temperature we see in the SST data (and satellite data).
  2. However, analysis shows that CO2 changes about four to seven months (and longer) after sea surface temperature changes.
  3. Therefore, atmospheric CO2 increase cannot be the cause of surface temperature increase. Real world data disproves the theory.

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7 Responses to “The Chicken or the Egg?”

  1. prcgoard Says:

    What is the precision or statistical error of SST measurements? Recently saw a comment that there is no data for a significant percentage of the oceans – sorry cannot remember the figure. For satellite measurements, does anyone know exactly what is measured? How precise is the calibration?
    Working to a tenth of a degree is close to meaningless!

  2. Geoff Sherrington Says:

    Good comment.
    When you look at the way the 2 traces in the last graph follow each other, you might infer that features of 0.2 unit in amplitude in one trace are matched by similar 0.2 unit changes in the other. It is far from the case that this happens every time, but it happens often enough to induce a sense of causation of one on the other.
    The SST units of deg C before scaling (top graphs) indicate that 0.2 of these units corresponds to about 0.05 deg C in SST. So, if you accept my postulate here so far, there is a rather extraordinary accuracy implied by the matching wriggles. No, I do not buy it. An alternative explanation for Ken’s close lagged match is intelligent design by numbers craftsmen generating HadSST3. Geoff.

    • kenskingdom Says:

      Good morning Geoff, prcgoard:
      Geoff you are correct, I scaled up SST by 4 for easier visual comparison. The accuracy of SST is questionable but HadSST3 is very strongly relied on, so probably “the best we’ve got”, similarly for CO2. If the best they can do disproves CO2 theory, what chance have they got? Every, because they write the script.

  3. John in Oz Says:

    A reference to this post has been sent to Josh Frydenberg with little expectation of a reply.

    I can only hope that the water torture method of constant counter arguments will bring some sense to our politicians.

  4. Andrew Says:

    Great Article. Thanks for these Ken. They really help illuminate different aspects of this issue.

  5. ngard2016 Says:

    Has anyone checked out the Humlum PR study ( 2013)? He used all temp data sets to compare co2 increases to temp trends ( 1980 to 2011) and came to the same conclusion.
    Prof Ole Humlum’s Climate 4 You site has a lot of detailed ongoing study of the climate and it is regularly updated.
    Any comments about this PR study and the lack of response over the last 5 years? Why haven’t even heavy weight Sceptics either criticized or endorsed this study? Why the silence?

    Here’s the Abstract.
    Using data series on atmospheric carbon dioxide and global temperatures we investigate the phase relation (leads/lags) between these for the period January 1980 to December 2011. Ice cores show atmospheric CO2 variations to lag behind atmospheric temperature changes on a century to millennium scale, but modern temperature is expected to lag changes in atmospheric CO2, as the atmospheric temperature increase since about 1975 generally is assumed to be caused by the modern increase in CO2. In our analysis we use eight well-known datasets: 1) globally averaged well-mixed marine boundary layer CO2 data, 2) HadCRUT3 surface air temperature data, 3) GISS surface air temperature data, 4) NCDC surface air temperature data, 5) HadSST2 sea surface data, 6) UAH lower troposphere temperature data series, 7) CDIAC data on release of anthropogene CO2, and 8) GWP data on volcanic eruptions. Annual cycles are present in all datasets except 7) and 8), and to remove the influence of these we analyze 12-month averaged data. We find a high degree of co-variation between all data series except 7) and 8), but with changes in CO2 always lagging changes in temperature. The maximum positive correlation between CO2 and temperature is found for CO2 lagging 11–12 months in relation to global sea surface temperature, 9.5–10 months to global surface air temperature, and about 9 months to global lower troposphere temperature. The correlation between changes in ocean temperatures and atmospheric CO2 is high, but do not explain all observed changes.

  6. ngard2016 Says:

    Prof Ole Humlum’s March 2018 State of the Climate Report is available from the GWPF site. PDF link is available at their summary.
    The 23 year temp pause in the stratosphere seems to have little connection to their AGW theory as well. Certainly there has been a lot of co2 emitted by the developing countries since 1995.

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