CO2 and Temperature

Ken Stewart, April 2011

Surely this has been shown before.  If not, it should have been.  If it has, it bears repeating.

As we all know,  an increase in carbon dioxide concentration leads to an   increase in global temperatures.  Right?

Wrong.  Exactly the reverse.

Now don’t get me wrong. There is a greenhouse effect, whereby greenhouse gases have made the earth’s temperature more than it would be without them.  We are pumping extra carbon dioxide into the atmosphere, so that CO2 levels are steadily increasing.  And temperatures appear to have been rising- certainly atmospheric temperatures have risen since 1979.

However, since carbon dioxide concentration measurements began at Mauna Loa in 1958, temperature has changed before carbon dioxide has.  That’s right, a change in temperature leads to a change in carbon dioxide concentration.

Here’s a graph showing CO2 concentration (reduced to compare with the temperatures) and global mean temperature recorded by UAH.  Red is for temperature, and CO2 concentration is “suitably” black.

Figure 1.

It is plainly obvious that CO2 levels are rising, and temperatures have been rising.  Temperatures fluctuate up an down quite a bit, and there is a regular annual wave in CO2 concentration believed to result from seasonal Northern Hemisphere  biomass growth and dieback.  It seems intuitive that with seasonal temperature rise, trees and grasses grow rapidly, absorbing CO2, and this causes CO2 concentration to fall.  In autumn and winter, as temperatures fall, the rotting biomass releases CO2.

Yet it’s not so simple.  I’ve included a 12 month running mean.  The small reduction in the rise of CO2 can be seen in the early 1990s, and a small lift about 1999-2000.  What could explain these variations?  Variations in energy consumption?

Nope- Mt Pinatubo and the 1998 El Nino.

Here’s a graph of changes in temperature and changes in CO2 concentration.

Figure 2

I calculated the difference in temperature and CO2 between each month and the month preceding, and smoothed the results with 12 month running means, which therefore overlap all seasons.  Remember this represents change in temperature and CO2, not absolute values.  Remember also that this is worldwide, so is not limited to seasonal changes.  Notice that change in temperature occurs before a change in CO2.  There appears to be a lag of from 3 to 9 months, and possibly 12 months, especially marked when there is a rapid change in temperature, and not so rapid for smaller change.  Smaller, slower changes appear to be overshadowed by the large seasonal variation, depending on the timing.

I also compared CO2 with HadcruT temperature data from 1958, the start of the Mauna Loa record, although I am not fond of any surface record because of potential problems with surface station siting and adjustments.  Still, it is a temperature record, and I am not interested in absolute temperature but change.

Figure 3

Again note that after a 3 to 9 month lag behind temperature change, sometimes up to 12 months, CO2 concentration changes.

It has been suggested that the small dip visible in Figure 1, in 2008 (circled), is a response to reduced industrial output from the Global Financial Crisis.  Figure 2 and Figure 3 show that this was not the case, and that the drop in CO2 was a response to lower temperature.

Conclusion:

• Carbon dioxide concentration, while increasing year to year, responds to temperature change after a lag of some months- not the reverse.
• We can predict that the CO2 concentration over the 2011-2012 period will have a smaller increase than normal, following the dropping temperatures.
• Provided that global CO2 output continues at current rates, we should be able to project future CO2 concentration from current temperatures several months in advance, and indeed from trends in the Southern Oscillation Index.
• It should be possible to quantify the relationship between temperature change and CO2 change.

We live in interesting times!

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Can We Predict Future Temperatures? Update

Ken Stewart, 5 April 2011

Updated 15 April, 1 May 2011

[The March 2011 UAH anomaly has come in at -0.1C, which makes the 12 month mean +0.27C.  0.02 out- not too bad!

My prediction for April is +0.23C.]

This is an interim post to flag an upcoming article.  I am working on an hypothesis- still in the “prototype” stage- concerning the relationship between long term SOI values and global temperature anomalies.

As a test of the predictive capability of this hypothesis, I have made an estimate of the running 12 month mean of the global anomalies to March 2011.  The estimate will be checked against the March figure to be announced on the UAH website at http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt in the next few days.

I estimate the 12 month running mean of UAH anomalies will be 0.29.   If this is wrong, I’ll have to rework my calculations.  If right, I will continue to fine tune formulae so as to make further estimates.

Here is the background.

This is the SOI since 1876 inverted, to show the relationship with temperature more clearly.

The inverted values show the SOI, and, this hypothesis will show, temperatures as well, trending down.

The running 12 month mean of SOI values with the UAH figures which begin in 1979.

The strong possibility is that a new 10-12 year cycle of El Ninos will begin after the current La Nina finishes.

The 1979 – 2011 plot clearly shows the 5 to 7 month lag in temperatures.

When the SOI is advanced 7 months, the match is close- but still does not explain the high temperatures of 2010.  (Large volcanic eruptions in 1982 and 1991 depressed temperatures for years afterwards.)

Here is the running mean for a decade of SOI values- 120 months.  The Great Climate Shift of the late 1970s is clearly visible, showing the massive change to predominantly El Nino conditions.  Note also the repeated rise and fall over several decades, and what I call “the many horned beasts” of El Nino peaks (just to be a bit melodramatically Biblical).

I am interested in the apparent lag between these means and global temperatures- between 10 and 12 years.  My hypothesis is that by interacting with current SOI values through thermal inertia of the oceans, decadal means influence global temperature, to the extent that temperatures can be estimated with some accuracy 7 months in advance, and temperature trends for the coming decade can be indicated for a variety of scenarios.

This hypothesis can be tested and refined by comparing with monthly global means, which is why the March UAH anomaly is crucial.

Time will tell.