Wobbly Universe

Over the last million years there have been ice ages with inter-glacials such as we are experiencing now about every hundred thousand years. The amount of CO2 in the atmosphere has moved in step with the temperature oscillations to a large extent, although this pattern has been broken recently. The historical record shows that temperature generally leads CO2 changes. Therefore CO2 is not the cause but the result of climate change.

However with the industrial society we have seen truly dramatic changes in CO2 levels which may well have taken us into new territory as far as cause and effect are concerned. With CO2 having never been outside the range 180 to 290 ppm (parts per million) for some 800,000 years, in just the last century or so it has raced up to 370 ppm. It seems that this change must be due to human action rather than being part of the natural ice age cycles.

The question then remains as to whether CO2 increase really can cause dramatic temperature changes or whether it only works the other way?

Various climatologists have tried to examine this question from a variety of points of view, from the expected physical effects of CO2 in the atmosphere through to whether temperature changes or CO2 changes are leading indicators of the other. Using some of their data I have assembled the following graph.

The upper line in the mauve colour shows the rate of change of CO2 concentration. I have used the change over a 12 month period and plotted it at the centre of that 12 month period. This means that it represents a 12 month centred moving average of the rate of change.

The lower line shows the temperature anomaly. This is the fluctuation of temperature from its average level. It shows what changes are happening in global temperatures from year to year.

It is clear that both graphs have a cycle of about 3.6 years in them. I have marked a regular 3.6 year cycle with green arrows and the two series both peak at the same time as this cycle. We can also see that individual cycles have unique characters which are common between the two series (CO2 and temperature), with for example a much higher sharper spike about 2/3 of the way through, so that we can safely say that the fluctuations are causally connected.

Incidentally, this period is rather close to 1/3 of the Sunspot cycle and appears to be a reflection of the SOI or Southern Oscillation Index, or El Nino cycle.

But which one of CO2 change and temperature fluctuation is causing the other?

If the temperature anomaly is causing increased CO2 production, that would make sense in terms of a chemical reaction formula.

If CO2 were to be affecting temperature, then we would expect the amount of CO2 to affect temperature or the rate of temperature increase, rather than the rate of change of CO2 being related. It makes no sense that when CO2 is increasing the temperature is higher, but when CO2 has reached a peak the temperature is already dropping again. So we can safely say that in the short term, CO2 is not the cause of temperature fluctuations.

Even so, this relationship is a bit mysterious. It makes sense that temperature can affect the rate of CO2 production, but in such a case we might expect that when temperature falls back to the same place the level of CO2 would also fall back to the same place. It does not. There is a continuous addition to CO2 in addition to the fluctuations due to temperature.

Perhaps the continuous extra production of CO2 is due to humans and the fluctuations in step with temperature are due to nature. This seems the likely conclusion of the observed relationship.