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.

The papers, and the editorial, are not entirely self-consistent (as is to be expected) and selective quotation could be used to support any number of viewpoints. Here I will try to give an accurate account of the intent of the volume (this will be slightly difficult, as I have no intention of reading the entire thing), as quote as much as my weary fingers allow.

This is a revised version; read the original if you want to see the changes. The revision occurred after the brief return to fame of this volume when it was quoted by Berger and Loutre in Science in 2002. I'll comment on B+L at the end.

Structure of the volume

The November 1972 of Quaternary Research was devoted to papers presented at a conference held in January, titled "The present interglacial: how and when will it end?". It says "the papers in this volume are an outgrowth of the working conference". Kukla, Mathews and Mitchell were the guest editors for the volume.

The contents are:

261-269: Editorial: Kukla, Mathews, Mitchell
270-273: Quaternay Hypsithermals: Emiliani
274-282: Interglacial and postglacial climates: the pollen record: Wright
283-302: Climatology of a glacial cycle: Fairbridge
303-314: past and present glaciological reponses to climate in eastern baffin island: Andrews, Barry, Bradley, Miller, Williams
315-322: Appraisal of the future climate of the holocene in the rocky mountains: Richmond
323-326: Diatom evidence bearing on the holocene in the south atlantic
327-334: Holocene interglacial in central europe and its land snails: Lozek
335-226: Freshwater ostracods in holocene cycle: Absolon
337-340: Holecene interglacial migrations of mammals and other vertebrates: Shultz
341-349: When will the present interglacial end?: Morner
350-354: Northeast atlantic post-eemian palaeoceanography: a predictive analog of the future: Mcintyre, Ruddiman
355-362: The significance of calcium carbonate oscillations in eastern equatorial atlantic deep-sea sediments for the end of the holocence warm period: Hays, Perruzza
363-367: Climatic record in north atlantic deep-sea core v23-82: comparison of the last and present interglacials based on quantitative time series: Sancetta, Imbrie, Kipp, Mcintyre, Ruddiman
368-373: Dynamics of the ocean-cryosphere system: barbados data: Matthews
374-383: End of the last interglacial in the loess record: Kukla and Koci
384-395: Abrubt climatic change at 90,000 BP: faunal evidence from the gulf of mexico cores: Kennett and Huddlestun
396-398: Speculations about the next glaciation: Dansgaard, Johnsen, Clausen, Langway
399-400: The salinity of the north atlantic ocean and the next glaciation: Weyl
401-408: Antarctic ice surges: Hollin
409-411: On climate change: Stuiver
412-424: Insolation regimes of interglacials: Kukla and Kukla
425-435: Atmospheric particles and climate: can we evaluate the impact of mans activities?: Schneider
436-445: Natural breakdown of the present interglacial: Mitchell

Context and Summary

Remember: lots of things we now know weren't available then. There was no Vostok core clearly showing 4 previous glacial periods with a nice 100kyr cycle (they had a 100kyr core from Greenland). Hayes et al (see main page) didn't come till 1976. Etc.

What they had was: a 20-ish year cooling trend (which we now know looks best in the northern hemisphere); a belief that previous interglacials were 10kyr-ish long; a conciousness that human activities might be changing the climate (for warm or cold was unclear, though guesses towards warmth were more common); and a belief that human activities might be vulnerable to cliamte change and perhaps they ought to care.

Remember also: these people are mostly geologist-types (the editorial says the conference was for "paleontologists, sedimentologists, stratigraphers, and palaeoclimatologists") and they don't mean what you might expect by things like "soon" and "brief".

Summarising the thing is difficult. Footnote 2 (which covers 1/3 of the first page of the editorial, and looks to me suspiciously like it was inserted at a late date for balance) seems to me to provide 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. 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...".

More from Emiliani below. Now read on, if you can bear it...

The papers

Some of the papers are very short - a page or 2 - and speculative: eg:

Speculations about the next glaciation: Dansgaard, Johnsen, Clausen, Langway: which presents a bit of data, and says (of a previous return to glaciation) "...[milankovitch or] are we faced with more or less accidental events, such as ice surges or intense volcanic activity, that trigger a full glaciation, if the insolation conditions favour such development? Is mans present activity equivalent to such an accidental event?".

Thats somewhat typical: there are more questions than answers, in the tedious old cliche.

Quaternay Hypsithermals: Emiliani

E begins by pointing out (his fig 1) that pre-1950, people thought there had been 4 major glaciations in the last 1Myr, separated by long interglacials. After C^14 and O^18/O^16 dating, people realised the truth, ah ha!: (1) T oscillated between interglacial max and glacial min more regularly, about 50kyr period (2) glacial and interglacials relatively short (10-30kyr each) (3) except for core stage 3, max's were about equal as were mins (4) interglacial maxes were less than 10kyr long.


This is wrong in two key points, as currently understood: glacial cycles are about 100kyr long; and the interglacials are shorter than the glacials.

E follows this with (his italics): "This latter conclusion [ie, (4)] is of immediate concern because the present warm interval has already lasted close to 10,000yr".

Interglacials (he likes to say, "Hypsithermals", meaning temperature peaks, but obviously no-one else could remember it) he estimates as 10% of the last 425kyr.

So... he's wrong, but thats not our main concern: we're interested in the state of knowledge then. Trying to predict, he says:

"...the hypsithermals represent a precarious balance [this is an odd thing to say] which can last only a relatively short period of time before more normal, lower temperatures are reestablished.

...mans interference with the heat budget... is assuming alarming proportions (SMIC 1971; Matthews et al., 1971). Thermal, CO2, and aerosol pollution produce contrasting effects... Their relative magnitudes are poorly understood and the net effect is unknown, not only in magnitude but even in sign. In the absence of man, the present hypsithermal [interglacial] should be ending (Emiliani, 1971)... Mans activiety may either precipitate this new ice age or lead to substantial or even total melting of the ice caps... and subsequent sea level rise. Needless to say, both phenomena, either one of which is now a distinct possibility, would lead to catastrophic environmental stresses. It is clear, then, that the present, precarious climatic balance must be stabalised. It is also clear that, in order to achieve this goal, the climatic history of the past half million years must be studied in much greater detail and the effect of human activity on cliamte must be assessed with quantitative precision."

So... his conclusion is that something will happen "soon" (but thats a geologists soon, not an everyday soon), but he doesn't know what, so we'd better study more to find out.

Atmospheric particles and climate: can we evaluate the impact of mans activities?: Schneider

Schneider will be familiar to regular readers of sci.env and the ice age controversies. In this paper he returns to the particulate loading theories of the famous 1971 R+S paper (see main page) but is less definite. The 1971 paper is very briefly referenced ("Particles, on the other hand, could decrease the temperature of the Earth's surface by screening out part of the incoming solar beam and thus raise the albedo (or reflectivity) of the Earth - thereby decreasing the amount of solar energy absorbed by the Earth (McCormick and Ludwig, 1967; Rasool and Schneider, 1971; Yamamoto and Tanaka, 1971)."), but this is preceeded by "The effect of increased CO2 is well-known to be an increase in the temperature of the Earth's surface by an enhancement of the 'greenhouse effect' (Manabe and Wetherald, 1967)".

He also notes that some (Bryon, 1968) think particulates are resp for cooling obs, and could lead to more [thats for DL].

He says "This paper will attempt to summarize the 'state of the art' concerning the question of atmospheric aerosols and climate..." which means it isn't going to try to balance that against CO2 warming.

The conclusions aren't terribly exciting... (1) Obs of inc in aerosol in NH; but obs still v unsatisfactory (2) global-av models indicate that inc aerosol could sig inc albedo; but better data req etc (3) better gcms needed. No exclamation marks, sorry.

Incidentally, there is a ref to a tech comment by Charlson, Harrison and Witt (Science, 1972, 175, 95-6) and reply by R+S, probably about vert dist of aerosol, that I haven't read. Go on someone, read it.

Content by WMC