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The ice age is coming, the sun is zooming in
Engines stop running and the wheat is growing thin
A nuclear error, but I have no fear
London is drowning-and I live by the river

See londonsburning.org
for full lyrics.

Context | Other references | Other, unsorted | Comments? | Updated 2005/02/09 Misc non-science papers | Silly stuff

A note for new visitors

Was an imminent Ice Age predicted in the '70's? No

If you can find me a reference saying otherwise, I'll put it here.

A couple of the SCOPE reports (13 and 27, from memory) are worth a look. NEW! [2005/01] RealClimate post - this may be a slightly more comprehensible intro to this subject.

NEW! [2004/11/10] National Geographic, 1976

[2004/07/09] Flohn, 1979, Quat Res

[2004/04/20] A climate book by H H Lamb (or bits of one)

[2004/01/02] Short note on the 1970 SCEP report.

[2004/02/07] Misc stuff from non science journals (so far only holds a newsweek 1975 article).

[2004/01/02] Short note on the 1970 SCEP report.

[2003/08/26] World Climate Conference, 1979 (esp Hare).

[2003/08/08] Kukla and Matthews, Science, 1972.

[2003/06/17] Stephen Schneider, The Genesis Strategy (I've only just got round to uploading it)

[2003/05/03] Howorth, 1905

[2003/04/16] G.J. Kukla, Nature, 253, 600-3, 1975: "Missing link between Milankovitch and climate"

[2002/09/26] Quaternary Research, 1972: "The end of the present interglacial"

[2002/04/25] Some notes from Imbrie&Imbrie, 1980

[21/12/2001] Asimov: from a lecture in 1974

[04/09/2001] Lowell Ponte: the cooling. An analysis

[04/09/2001] A look at chapter 16 of Imbrie and Imbrie: Ice ages: solving the mystery

[30/06/2001] Review of the not-very famous US National Academy of Sciences 1975 Report

[28/06/2001] An article by Alison George, based on a talk I gave, in the Grauniad, or I have archived it here. Its not actually terribly clear: some time I must rant about journalists...

To clarify a little: I am interested in "Was an imminent Ice Age predicted in the '70's by scientists, in scientific journals?". That means articles in scientific journals and reputable books. I am not particularly interested in what appeared in the popular press or on TV and do not intend to discuss it here (but see context), since I do not regard these as reliable sources for scientific information.

Note that many of the oh-there-was-an-ice-age-predicted type articles tend to focus on non-science articles for their sources: newsweek, for example. This is cheating on their part. Newsweek isn't science, of course. If newsweek was quoting peer-reviewed journals, then they should go back to those.

We also need to know what we mean by "imminent". Since the question arises in the context of the greenhouse gas/climate change debate, "imminent" is a timescale comparable to greenhouse-type timescales: ie, the next century or so. See below for my take on long-term predictions.

Comments, clarifications and corrections to this page are welcome see comments or mail wmc@bas.ac.uk.

If you think you have a new reference that may be interesting, please send it to me. I don't guarantee to check it out immeadiately: you will need to have patience. However, I will list all outstanding references below:
Just in: these 2 both mention a 1972 letter, amongst other things. Interesting! I haven't read them properly yet.

  1. http://www.meteohistory.org/2004polling_preprints/docs/abstracts/reeves&etal_abstract.pdf
  2. http://www.weizmann.ac.il/ESER/People/yinon/courses/climate_variability_lecture.pdf (seems to be dead; the wayback machine obliges)

The purpose of this page is to provide a counter to the mythology that "journals were stuffed full of articles predicting an imminent ice age in the '70's". An article by the John Birch Society seems to be an example of the kind of thing [oops, they've changed the page! I should have copied the old one... happily, JS points me to: the web.archive.org's archive of it] (see also "The New Australian", or http://www.ff.org/library/whatsnext.html [local cache]), and it even appears in milder form in the 1999 Reith lectures. The relevance of this claim is that "greenhouse sceptics" are fond of claiming that "all scientists" were predicting cooling a decade ago and now they've switched to warming. However, closer probing reveals few of these articles.

The argument has two very seperate strands: the "orbital-forcing" strand, wherein the cooling was to occur as a result of variations in the Earths orbit around the sun, and the "aerosols" strand, which supposed cooling in response to a massive increase in the aerosol loading of the atmosphere. In fact there is a variant of the first idea, rapid climate change during interglacials, see Flohn, 1979.

Let me say now that I have no quarrel with the large volume of perfectly sensible scientific literature that examines the Milankovich hypothesis and the probable connection between orbital forcing and past glaciations. The coincidence of the periods of the orbital forcing and the ice ages seems so close that (in common with received opinion on this subject) I believe that orbital variations have caused the ice age timing over the last, say, 3 Myr. Hays et al, Science, v194, #4270, p1121, 10/Dec/1976 is an excellent paper on this subject (see below). It is worth pointing out, though, that although the coincidence in timing virtually compels belief in the connection, there is still a problem in that the strongest response (at 100 kyr) corresponds to the weakest forcing, and as far as I am aware this problem has not been resolved. Nor do I take issue with the contention that, in the absence of anthropogenic forcing, it is natural to predict a gradual return to ice age conditions in the future (though quite how long that might be is uncertain. The "all interglacials last 10 kyr" (or 12, or whatever) idea is wrong. Various sources (Loutre and Berger) say that due to the predicted orbital configurations, the prediction (in the absence of anthro forcing) is for this interglacial to last 50 kyr or more. Jan Hollan has a page showing some nice graphs about that at http://amper.ped.muni.cz/gw/articles/html.format/orb_forc.html. What I do assert, though, is that predictions for the immediate future (immediate in this context being the next few centuries) need to include anthropogenic forcing from CO2 increases in order to be meaningful, and that people were aware of this in the 1970's. Simple efforts to combine anthropogenic and Milankovich forcings are confounded by the problem mentioned above, and I believe (no ref. available) that current radiative forcing from CO2 release already exceeds that from Milankovich forcing. Any attempt, made in the light of todays knowledge, to predict the likely course of climate for the next several thousand years would need to include an assumption/prediction/model of future CO2 levels, which at the moment seems impossible over that time span.

I have been reminded of the following posts: Cooling vs. Warming by Robert Parson in 1993 and Re: control the climate by Michael Tobis in 1995. My summary of the first of these posts is (shamelessly ripped from the post itself): everyone agreed that CO2 emissions could produce warming and that particle emissions could produce cooling, but that lack of information precluded any definite conclusions about which was more important. The second is harder to summarise (why not just read it?) but suggests that predictions of cooling were made by observational paleoclimatologists rather than physical climatologists and were based on dubious and non-physical arguments. Franz Gerl reminds us that a report to the Carter administration in 1980 predicted warming.

The following paragraph is cut from the Cato Insitute. Its by Richard Lindzen, generally considered a skeptic. I wouldn't agree with all of (especially the tone ;-) but its description of the cooling scare as "minor" and "the scientific community never took the issue to heart, governments ignored it" is good.

Many studies from the nineteenth century on suggested that industrial and other contributions to increasing carbon dioxide might lead to global warming. Problems with such predictions were also long noted, and the general failure of such predictions to explain the observed record caused the field of climatology as a whole to regard the suggested mechanisms as suspect. Indeed, the global cooling trend of the 1950s and 1960s led to a minor global cooling hysteria in the 1970s. All that was more or less normal scientific debate, although the cooling hysteria had certain striking analogues to the present warming hysteria including books such as The Genesis Strategy by Stephen Schneider and Climate Change and World Affairs by Crispin Tickell--both authors are prominent in support of the present concerns as well--"explaining'' the problem and promoting international regulation. There was also a book by the prominent science writer Lowell Ponte (The Cooling) that derided the skeptics and noted the importance of acting in the absence of firm, scientific foundation. There was even a report by the National Research Council of the U.S. National Academy of Sciences reaching its usual ambiguous conclusions. But the scientific community never took the issue to heart, governments ignored it, and with rising global temperatures in the late 1970s the issue more or less died. In the meantime, model calculations--especially at the Geophysical Fluid Dynamics Laboratory at Princeton--continued to predict substantial warming due to increasing carbon dioxide. Those predictions were considered interesting, but largely academic, exercises--even by the scientists involved.

Here are two references dug out by the IceAgePredictors, representing the two strands mentioned above.

Taking them in order of appearence:

JD Hays, J Imbrie and NJ Shackleton, Science, v194, #4270, p1121, 1976/12/10

This paper is actually rather noteworthy in the annals of science, a seminal study linking orbital forcing to the periodicities found in ocean cores. But that doesn't protect it from being abused by sceptics.

The article was shamelessly misquoted to support the assertion that an "immenent" iceage was predicted. Actual reading of the article (an action not performed by those who cited it) shows that: it hedges its predictions by saying that these would be the tendencies in the absence of human perturbation of the climate system, that it predicts glacial conditions in 20,000 years time and that it predicts (again, assuming no human influence) a cooler trend over the next several thousand years (not glaciation within this timespan).

Its worth quoting the entirety of the section dealing with "future climate" to demonstrate this point fully. It is:

Future climate. Having presented evidence that major changes in past climate were associated with variations in the geometry of the earth's orbit, we should be able to predict the trend of future climate. Such forecasts must be qualified in two ways. First, they apply only to the natural component of future climatic trends - and not to anthropogenic effects such as those due to the burning of fossil fuels. Second, they describe only the long-term trends, because they are linked to orbital variations with periods of 20,000 years and longer. Climatic oscillations at higher frequencies are not predicted.

One approach to forecasting the natural long-term climate trend is to estimate the time constants of response necessary to explain the observed phase relationships between orbital variation and climatic change, and then to use those time constants in the exponential-response model. When such a model is applied to Vernekar's (39) astronomical projections, the results indicate that the long-term trend over the next 20,000 years is towards extensive Northern Hemisphere glaciation and cooler climate (80).

And thats it.

Rasool and Schneider, Science, July 1971, p 138, "Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate"

The claims and counter-claims that were posted are here. The article investigates effects of large CO2 and aerosol perturbations. Large enough aerosol increases lead to large temperature drops, whereas even large CO2 increases "only" lead to changes of 2 oC. There is some discussion of likely aerosol or CO2 increases.

While I'm here, note that "opponents" of Schneider generally mention "a paper by Schneider" and rarely report that he was the second author. Presumably this is because demonising Rasool wouldn't serve their purposes. Alternatively, it may be because few people have actually read the paper, and rely on secondary sources for information (including authorship) about it.

The article does not predict the future climate of the Earth. It does attempt to predict the climate sensitivity to CO2 and aerosol forcings. The predicted CO2 sensitivity would now be regarded as rather low (and a footnote points out that at the same time other authors found sensitivities three times as large). A second footnote points out that the sort of model used (a 1-d radiative model) is only suitable for examining the effects of small perturbations about current climate values (a qualification that applies to many models nowadays, too), but fails to note the inherent contradiction with the title of the paper.

The concluding section contains some guesses towards future aerosol levels. Quoting: "Even if we assume that the rate of scavenging and of other removal processes for atmospheric dust [generally & confusingly used interchangably with aerosol in the article (WMC)] particles remains constant, it is still difficult to predict the rate at which global background opacity of the atmosphere will increase with increasing particulate injection by human activities. However, it is projected that man's potential to pollute will increase 6 to 8-fold in the next 50 years. If this increased rate of injection... should raise the present background opacity by a factor of 4, our calculations suggest a decrease in global temperature by as much as 3.5 oC. Such a large decrease in the average temperature of Earth, sustained over a period of few years, is believed to be sufficient to trigger an ice age. However, by that time, nuclear power may have largely replaced fossil fuels as a means of energy production."

Other people have other takes on this paper: John Daly is the most obvious. It is worth pointing out that Dalys page contains several mistakes - for example, he claims that "This means that Schneider's conclusions would be just as valid today". Daly is perfectly well aware that the Schneider paper uses incorrect (a fact of 3 too low) values for CO2 sensitivity, rendering the conclusions invalid in the light of todays science - he just doesn't choose to put that fact onto the page.

GoogleWatch: a sample of some usenet posts about this paper: must add more sometime:

  1. July 2002
  2. Sept 1997
  3. Dec 1997 (*read this one*!)

An interesting point arises:

people critise R+S for being hopelessly, laughably wrong. Clearly their estimates of the aerosol increase were wrong, but I know of no source showing that their scientific analysis of the response of climate to increased aerosol was wrong.

I've raised this point in sci.environment on occaision. The best response I've had is a ref to a comment by Gast in a succeeding issue of Science. But his point doesn't address my question above. Gast notes that dT is linear in aerosol, as far as he can see, and that R+S's figures, being logarithmic, are misleading. But this has no relevance to the numbers R+S produce. Gast also (probably correctly) points out that anthro aerosol is only 1/5 of the total, and hence an 8x increase in anthro aerosol wouldn't increase the total by 8x but 2-4x, thus reducing R+S's numbers. But again this is irrelevant to the science that R+S is presenting. So the question remains: when R+S say that and increase in (total) aerosol by a factor of 8x would leading to cooling of ?3.5K? and this could lead to a new ice age, is that wrong or not? Was is rebutted soon after, more recently, or not at all?

[Don Libby attempted to use results from the IPCC SAR, see here which were very tentative, but might be read to indicate that R+S weren't too far wrong.]

ps: to show that R+S weren't as far out on a limb as often asserted, note that the letter following Gast broadly supports R+S's numbers.

This point was discussed in some detail in the thread Global warming is happening. That is the scientific judgment in sci.environment.

Other references

US National Academy of Sciences 1975 report

B J Mason, QJRMS, 1976

N Calder, Nature, 1974

M K Miles, Nature 1978

J Gribbin, Cliamtic Change, 1978

G.J. Kukla, R.K. Matthews & J.M. Mitchell, Quaternary Research, 1972

H. Flohn, Quaternary Research, 4, 385-404, 1974, "Background of a geophysical model of the initiation of the next glaciation".

Quotes from "Climatic Change and Variability"

subtitled "a southern perspective", based on a conference at Monash U, Melbourne, Australia, 1975. Eds: Pittock et al, CUP, 1978.

This book gives some indication of the flavour of thought at the time of the conference it reports.

From section 8.2 Possible future climatic trends: a panel discussion.

Flohn: ...the probability of a transition to the type of climate leading to an ice age in the next 100y is less that 1%, but that the possibility of large-scale human interference with the climatic system is much larger. It is a question of how much man contributes to the state of the climate we have. If one deals with the matter from the viewpoint of energetics one comes to the result that the sum of man-made interference with this system is of the order of 10% of the energy which is converted in the climatic fluctuations we have experienced in the last 100 or 200 y. The sum of these man-made effects (perhaps this is a controversial matter) should tend, generally speaking, to warming of the atmosphere... Now if we allow man's interference with climate to increase exponentially as it has doe in recent years, we sooner or later come to a stage where this 10% rises to 100% resulting in continuous warming ... this would be a really dangerous situation ... My feeling is that if man's interference with the climatic system is uncontrolled for some decades, together with uncontrolled growth of energy use, sooner or later during the next century the warming will overwhelm natural factors which usually produce cooling.

Chapell: ... in regard to future climatic trends, as long as other particularly important factors such as N atlantic temperature, and also the factors of pollutants and dust components of the atmosphere, remain about as they are, the Milankovitch kind of prediction is that glaciation is not on in the next 70,000 years, because we are moving into a period of low orbital eccentricity of the kind not seen for about 700,000 years. Shackleton: I would like to dispute you conclusion to the extent that at no time in the last 3 million years has any interglacial lasted significantly longer than 10 or 12 ky. Chappell: Knowing the records I agree absolutely and thats why I prefixed my "prediction" with a quailifying clause ... but I insist that the modulation of the glacial record so closely parallels the orbital processes that it must play an important part.

There is more but thats a flavour. Judge for yourself.

2003/05/02. V2.0. Unify scattered copies. Check links. Give version number.
2004/02/07. V2.01. Move to wmconnolley.org.uk.
2004/02/07. V2.1. Add
Misc non science, to hold the 1975 newsweek article.
2005/01/05. V2.2. Various changes, lastly to expand Hays et al. Put under RCS.

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