Retorts

CO₂ Controversy

Dr de Freitas's article [Viewpoint, May] is remarkable for the sheer absence of anything other than opinion to support the claims that he is making. It would be indulging him too much to analyse his article in detail, but I believe his credibility would be increased by satisfactory responses to the following points:

(1) Could he please supply a listing of the "great number of eminent atmospheric scientists who are now speaking out"? I would be interested then to carry out a literature search on their peer refereed publications to see if Dr de Freitas' claim is correct.

(2) I believe, having seen some of the results, that the latest GCMs do a remarkably accurate job of predicting climate. Would Dr de Freitas care to comment on the latest results from the model developed by the British Meteorological Office?

(3) I had not realised that CO₂ alone was the basis for taking strong action on greenhouse gases. Perhaps Dr de Freitas would care to provide documentary evidence of his assertion?

(4) "... the main greenhouse gases are gases that have always had a role in global climate processes, with concentrations in the past rising above and falling below present levels." Some evidence from Dr de Freitas on rises above the present levels, together with climate temperatures at the time, would be most useful. I would prefer not to have data from 100 million years ago, which is highly suspect and applies to a very different continental distribution than today and rather different levels of solar insolation. Back about 200,000 years will be quite sufficient.

(5) "The impact is likely to be far greater than any change caused by global warming." Can we have some data, please, together with source. I can readily supply peer refereed economic estimates suggesting that the converse point of view is more credible.

I see no point in going on with more criticism.

P Waring, Wainuiomata

Dr Chris de Freitas replies:

P. Waring will be aware that the piece to which she or he refers was not an article but a summary "Viewpoint" limited to a maximum of 1,500 words. Detailed discussion with referencing was not possible. My summary responses to her/his questions are as follows.

1) R.C. Balling, H.W. Ellsaesser, S.B. Idso, R. Lindzen, P.J. Michaels, R. Pielke, M. Garstang, L.S. Gandin, J.A. McGinley, W.E. Reifsnyder, S.F. Singer, etc. (I have a list of 40 other eminent atmospheric scientists).

2) The recent UKMO does indeed perform a lot better than the older GCMs, but to call it "accurate" is exactly the sort of exaggerated (inaccurate) claim to which I refer in my commentary. But assuming for argument's sake that it is at last a reliable model, why were the results of the earlier models so credulously accepted?

3) The IPCC says so.

4) See: L. Franzen (Ambio, Vol. 23, p.300, 1994); A. Logo and S. Brown (Vegetatio, Vol 68, p. 83, 1986); B. Sellwood, G. Price and P. Valdes (Nature, Vol. 370, p. 453, 1994).

5) See: C.R. de Freitas ("The greenhouse crisis: myths and misconceptions". Area, 23, 1, 11-18, 1991); W.E. Reifsnyder ("A tale of ten fallacies: the sceptical inquirer's view of the carbon dioxide/climate controversy". Agricultural and Forest Meteorology, 47, 349-371, 1989); S.F. Singer ("Benefits of global warming". Society, March/April, 33-40, 1992).

C R de Freitas, University of Auckland