You've heard it before, at dinner parties, from taxi drivers, from commenters on the intertubes: "Global warming? Pah! I remember they were talking about global cooling when I was a lad." As Peterson, Connolley, and Fleckthe, the authors of "The Myth of the 1970s Global Cooling Scientific Consensus" [1] explain: "the following pervasive myth arose: there was a consensus among climate scientists of the 1970s that either global cooling or a full-fledged ice age was imminent." But was it true? No.

(Note: The author, William Connolly, writes the Stoat blog on ScienceBlogs, and has pimped his article there, as well as kindly making the PDF available.)

The test of the veracity of that claim is the content of the published literature. The authors worked their way through JSTOR (an online archive of numerous journals), along with back issues of Nature, and the American Meteorological Society's own archives. Any scientific consensus on global cooling would swiftly become apparent by both the abundance of papers on the topic, and the frequency with which they were cited.

And it turned out that there did seem to be a broad consensus in the 1970s... behind global warming. Not that there weren't a few papers discussing the next ice age as well, but these were few and far between, and need to be put into context. During the 1960s and 70s, improvements in our ability to date prehistoric ice movements reawakened interest in the theories of Serbian geophysicist Milutin Milankovitch, who proposed that regular changes in the eccentricity of the Earth's orbit could account for the sequence of ice ages. Thus, there was considerable interest at the time in predicting when the next ice age might come, but these researchers were looking thousands of years into the future. In terms of what was happening to the climate right now, the consensus behind global warming was already getting pretty solid 30 years ago.

So where does this myth come from? From a research point of view the results I've described above are pretty uninteresting - I already knew that suggestions a 1970s scientific consensus was concerned about an impending Ice Age were nonsense. More interesting to me are the ways the authors suggest that the myth has been propagated.

The first culprit as ever seems to have been the media, and the authors took a look at a number of popular science articles of the period. Never one to let annoying little details like "context" stand in the way of a good story, the media published headlines like "Brace yourself for another Ice Age", and Time magazine is quoted referring to "the harbinger of another ice age": the former refers to predictions of an ice age in several thousand years time, and the latter names only one scientist, who is quoted as saying that any cooling trend is likely to be temporary.

So media exuberance counts for some of it, but of course with any discussion of climate science we soon stumble into the climate lobby, the conspiracy theorists and denialists, and so it should come as no surprise to find that a lot of the articles trying to perpetuate this myth have done it by quote mining research with the sort of selectivity you'd find on Conservapedia. As the authors bemoan:

"Underlying the selective quotation of the past literature is an example of what political scientist Daniel Sarewitz calls 'scientization' of political debate: the selective emphasis on particular scientific 'facts' to advance a particular set of political values [2]. In this case, the primary use of the myth is in the context of attempting to undermine public belief in and support for the contemporary scientific consensus about anthropogenic climate change by appeal to a past 'consensus' on a closely related topic that is alleged to have been wrong"

The authors give a typical example, and anyone reading here familiar with lobbying materials on climate science from places like JunkScience.com will be aware of hundreds of similar cases.

"In a 2003 Washington Post op-ed piece, former Energy Secretary James Schlesinger quoted a 1972 National Science Board report as saying, 'Judging from the record of the past interglacial ages, the present time of high temperatures should be drawing to an end... leading into the next glacial age'."

Now, even if you didn't know what the original report really said, the fact that the Energy Secretary is quoting from a report that is 31 years old is a big clue that perhaps the scientific basis for his comment is a little bit shakey. In fact, the very next words in the report are "...some 20,000 years from now. However, it is possible, or even likely, that human interference has already altered the environment so much that the climatic pattern of the near future will follow a different path."

You don't accidentally cut off a quote mid-sentence. The Energy Secretary must have known that he was lying, and he and others are helped in this by the general inability of the media to place scientific research in an appropriate context. Fortunately though, thanks to the efforts of people like the authors of this paper, this is yet another climate myth facing extinction.

[1] Thomas C. Peterson, William M. Connolley, John Fleck (2008). The Myth of the 1970s Global Cooling Scientific Consensus Bulletin of the American Meteorological Society, preprint (2008) DOI: 10.1175/2008BAMS2370.1 (PDF)

[2] D SAREWITZ (2004). How science makes environmental controversies worse Environmental Science & Policy, 7 (5), 385-403 DOI: 10.1016/j.envsci.2004.06.001