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The End of Atmospheric CO2 Growth
Volume 4, Number 35: 29 August 2001

The end is near.  According to a study in the 2 August 2001 issue of Nature, human population growth "is likely to come to an end in the foreseeable future."  How foreseeable?  Try 2070.  This is the conclusion of Wolfgang Lutz of the International Institute for Applied Systems Analysis in Laxenburg, Austria, Warren Sanderson of the Departments of Economics and History at the State University of New York at Stony Brook, and Sergei Scherbov of the University of Groningen in The Netherlands.  On the basis of their latest calculations, which are described in their article and supplementary information available on Nature's world-wide web site, they state that "the median value of our projections reaches a peak around 2070 at 9.0 billion people and then slowly decreases."

So what does "the end of world population growth," as the academics title their paper, have to do with "the end of atmospheric CO2 growth," as we title this editorial?  Just about everything, it turns out, as world population is one of the best predictors of atmospheric CO2 concentration to ever come down the pike, as demonstrated by Idso (1989).  Based on world population and atmospheric CO2 concentration data assembled in his book, for example, augmented by data for 1999 Fig. 1(the year world population reached the six billion mark), we have derived the two predictive relationships portrayed in Figures 1 and 2.

Fig. 1.  Atmospheric CO2 concentration vs. world population based on data presented by Idso (1989) updated to 1999, the year earth's population reached the six billion mark.

Fig. 2 Fig. 2.  Atmospheric CO2 concentration vs. world population based on data presented by Idso (1989) from 1968 onward, including data for 1999.  In our father's original analysis, 1968 was identified as a point of slight departure from the relationship defined by all earlier data and, hence, this relationship probably gives slightly more accurate predictions of the future than does the relationship of Fig. 1.

The linear relationships of each of these figures have been extended to a world population of nine billion people, which is where Lutz et al. calculate the population of the planet to peak in the year 2070, according to the median result of their several projections.  At this population, the relationship of Fig. 1 predicts an atmospheric CO2 concentration of 412 ppm, while that of Fig. 2 predicts a concentration of 421 ppm.  Furthermore, beyond this point in time the relationships of the two figures predict that atmospheric CO2 levels will actually begin to drop, as the planet's population begins to decline.

These conclusions are dramatically at odds with those of the IPCC crowd, who predict far greater concentrations for far greater times to come, but they are far more robust.  The equation derived in Fig. 1, for example, is based on data going all the way back to 1650.  For the last three and a half centuries, it has performed marvelously.  To think it will suddenly cease to apply over the next seven decades is ludicrous.  There may be slight variations ahead; but as the results of Fig. 2 demonstrate, they likely will be so small as to be essentially insignificant.

So who or what are you going to trust?  Unproven predictions based on theoretical models of how the entire earth-ocean-atmosphere system is believed to operate, as best as our present knowledge of these complex and interrelated entities and their numerous sub- and sub-sub-systems allows us to approximate them?  Or the projections of a simple but straightforward empirical relationship based on real-world observations that has a proven track record of providing an excellent representation of atmospheric CO2 concentration for fully 350 years?  We hope we don't have to spell it out for you any more than this, or emphasize any additional words.  It's truly a no-brainer: real-world data always win.  And in this case, it's already happened!

Dr. Craig D. Idso
Dr. Keith E. Idso
Vice President

Idso, S.B.  1989.  Carbon Dioxide and Global Change: Earth in Transition.  IBR Press, Tempe, AZ.

Lutz, W., Sanderson, W. and Scherbov, S.  2001.  The end of world population growth.  Nature 412: 543-545.