G.J. Kukla, R.K. Matthews & J.M. Mitchell, Quaternary Research, 2, 261- 9, 1972: "The end of the present interglacial"

Quaternary research, volume 2, number 3, 1972 is devoted to the topic "The end of the present interglacial", and is thus a very useful source for these discussions. Kukla, Mathews and Mitchell were the guest editors for this volume. Footnote 2 provides a good summary of ideas at that time amongst this research community:

Variation in research stategy amongst the various authors deserve explanatory note. Many authors of this volume consider the precise causitive mchanism of climate change to be poorly understood at present. Their conclusions and predictions are therefore based on empirical recognition of parallels in time series data for climatic indicators between past interglacials and the recent warm interval (cf. Emiliani). Indeed, many articles simply draw conclusions concerning past events and leave it for the reader to imply that similar events may be anticipated in the future (cf. Mathews, Kennett and Huddlestun, this volume). On the other hand, some authors consider the cause of the glacial-interglacial climate cliamte [sic] change to lie in the changing geographic distribution of insolation (the so-called Milankovitch mechanism). These authors base their conclusions and predictions, at least in part, upon comparison between the calculated variations in insolation and the palaeoclimatic evidence (cf. Kukla and Kukla, or Mitchell).

These two different approaches to research on climate change must run their own courses until such time as the validity of general theories is well demonstrated. Indeed, testing of general theories with empirical geologic data is possibly the largest contribution which geologists can make to research on future climatic change.

Perhaps the most interesting thing to note from this is that the Milankovitch hypothesis had not been generally adopted by this time.

Also, I think that they are being careless with their use of the word "prediction" here; I think the individual authors of the volume are more careful.

The editorial begins with a discussion of the cooling trend then prevalent; then on p. 263 we find "When comparing the present with previous interglacials, several investigators showed that the present interglacial is in the final phase ... and that if nature were allowed to run its course unaltered by man, events similar to those which ended the last interglacial should be expected soon, possibly within the few next centuries."

The signs pointing to an end appear to be vegetation changes, such as the decline of elms. I don't know about that stuff. In passing, note that they use "soon" to include "within the few next centuries", probably because they are geologists.

Towards the end, they write:

"...the basic conclusion to be drawn from the discussions in this section is that the knowledge necessary for understanding the mechanism of climate change is still lamentably inadequate".

Honesty compells me to include, however, the rather contradictory conclusion (b) from the conference summary: "Global cooling and related rapid changes of environment, substantially exceeding the fluctuations experienced by man in historical times, can be expected within the next few millenia; perhaps even centuries."

From my (brief) reading of the conference papers I consider this statement a bit odd; given time and encouragement I might search a bit harder. For example, the first paper by Emiliani says

"Thermal, CO2 and aerosol pollution pollution produce contrasting effects... Their relative magnitudes are poorly understood and the net effect is unknown ... even in sign. In the absence of man, the present hypsithermal [interglacial] should be ending... Mans activiety may either precipitate this new ice age or lead to substantial or even total melting of the ice caps...".

So, no certainty there, and definitely no predictions.

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