22 January 2009
Increasing Atmospheric CO2: Manmade…or Natural?
January 21st, 2009 by Roy W. Spencer, Ph. D.
In fact, it turns out that these large year-to-year fluctuations in the rate of atmospheric accumulation are tied to temperature changes, which are in turn due mostly to El Nino, La Nina, and volcanic eruptions. And as shown in the next figure, the CO2 changes tend to follow the temperature changes, by an average of 9 months. This is opposite to the direction of causation presumed to be occurring with manmade global warming, where increasing CO2 is followed by warming.
From picture (1) This means that most (1.71/1.98 = 86%) of the upward trend in carbon dioxide since CO2 monitoring began at Mauna Loa 50 years ago could indeed be explained as a result of the warming, rather than the other way around.
If natural temperature changes can drive natural CO2 changes (directly or indirectly) on a year-to-year basis, is it possible that some portion of the long term upward trend (that is always attributed to fossil fuel burning) is ALSO due to a natural source?
After all, we already know that the rate of human emissions is very small in magnitude compared to the average rate of CO2 exchange between the atmosphere and the surface (land + ocean): somewhere in the 5% to 10% range. But it has always been assumed that these huge natural yearly exchanges between the surface and atmosphere have been in a long term balance. In that view, the natural balance has only been disrupted in the last 100 years or so as humans started consuming fossil fuel, thus causing the observed long-term increase.
But since the natural fluxes in and out of the atmosphere are so huge, this means that a small natural imbalance between them can rival in magnitude the human CO2 input. And this clearly happens, as is obvious from the second plot shown above!
So, the question is, does long-term warming also cause a CO2 increase, like that we see on in the short term?