Limits to existing quantitative understanding of past, present and future changes to atmospheric carbon dioxide concentration

A presentation by Richard S. Courtney to the Climate Conference held In New York, on 2 to 4 March 2008


This presentation demonstrates that it cannot be known what if any effect altering the anthropogenic emission of carbon dioxide (CO2) will have on the future atmospheric CO2 concentration.

It is commonly assumed that the rise in atmospheric CO2 concentration during the twentieth century (approx. 30% rise) is a result of anthropogenic emissions of CO2 (1,2,3) . However, the annual pulse of anthropogenic CO2 into the atmosphere should relate to the annual increase of CO2 in the atmosphere if one is directly causal of the other, but their variations greatly differ from year to year (4) .

This presentation considers mechanisms in the carbon cycle and uses the model studies of Rörsch, Courtney & Thoenes (2005) (4) to determine if natural (i.e. non-anthropogenic) factors may be significant contributors to the observed rise to the atmospheric CO2 concentration. These considerations indicate that any one of three natural mechanisms in the carbon cycle alone could be used to account for the observed rise. The study provides six such models with three of them assuming a significant anthropogenic contribution to the cause and the other three assuming no significant anthropogenic contribution to the cause. Each of the models matches the available empirical data without use of any ‘fiddle-factor’ such as the ‘5-year smoothing’ the UN Intergovernmental Panel on Climate Change (IPCC) uses to get its model to agree with the empirical data.

So, if one of the six models of this paper is adopted then there is a 5:1 probability that the choice is wrong. And other models are probably also possible.

And the six models each give a different indication of future atmospheric CO2 concentration for the same future anthropogenic emission of carbon dioxide.

This indicates that the observed rise may be entirely natural; indeed, this presentation suggests that the observed recent rise to the atmospheric CO2 concentration most probably is natural. Hence ‘projections’ of future changes to the atmospheric CO2 concentration and resulting climate changes have high uncertainty if they are based on the assumption of an anthropogenic cause.

Download PDF

This browser does not support PDFs. Please download the PDF to view it..

Leave a Reply