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Climate Change of the Twentieth Century: Natural or Anthropogenic?
Barnett, T.P., Hasselmann, K., Chelliah, M., Delworth, T., Hegerl, G., Jones, P., Rasmusson, E., Roeckner, E., Ropelewski, C., Santer, B. and Tett, S.  1999.  Detection and attribution of recent climate change: A status report.  Bulletin of the American Meteorological Society 80: 2631-2659.

What was done
With respect to the current debate over the role that the historical rise in the air's CO2 concentration may or may not have played in the modest global warming of the past century, the authors state that "the burden is clearly on the scientific community to demonstrate that their computer scenarios for future climate are realistic."  They then proceed to analyze and discuss this issue.

What was learned
After carefully considering the problem from many different angles, the authors conclude that (1) "there has been to date no completely convincing demonstration that the anthropogenic effects predicted by advanced climate models have been unambiguously detected in observations," (2) "given the large model uncertainties and limited data, a reliable weighting of the different factors contributing to the observed climate change cannot currently be given," and (3) "the current state of affairs is not satisfactory."

What it means
We feel that language of this sort, especially from some of the major contributors to the Intergovernmental Panel on Climate Change report that concluded - with respect to the global warming of the past century - that "the balance of evidence suggests a discernible human influence on climate," indicates the weakness of that conclusion, which the authors of this paper now say "admirably summarizes the present ambivalent scientific consensus."  Clearly, their statements are so tortured that there can be no doubt that whatever the consensus statement is supposed to mean, the balance of evidence does not meet the authors' stated criterion at the start of their paper that "the burden is clearly on the scientific community to demonstrate that their computer scenarios for future climate are realistic."  Hence, we agree with them when they state that "the current state of affairs is not satisfactory."  And we also agree with them that until this situation is corrected, there will be some, as they put it, "who will use it as an excuse for considering remedial action."  Their own analysis, therefore, would seem to argue against the adoption of the Kyoto Protocol and any other like measures at the present time.

Reviewed 15 February 2000