Conservatives like to point out that in the 1970’s there was supposedly a great deal of concern about “global cooling” and the possibility of a new ice age. They like to refer to this to imply that scientists are a bunch of idiots and frequently get things wrong. The implication is that if they were so off base in the 1960’s regarding the possibility of “global cooling,” they’re most likely off-base now with claims of global warming. It’s a nice argument but is completely untrue.
Here’s the basic story of “global cooling.” My details are taken largely from a paper published by the American Meteorological Society called The Myth of the 1970’s Global Cooling Scientific Consensus, which is available at: http://journals.ametsoc.org/doi/pdf/10.1175/2008BAMS2370.1]
As noted previously, scientists have understood since the 1890’s that adding carbon based gases, particularly carbon dioxide or CO2, to the atmosphere would lead to increased atmospheric temperatures.
But in the 1950’s and 1960’s the amount of smog and visible pollutants (known as aerosols) were becoming a major concern. Some scientists suggested that the amount of pollution could block solar ration and potentially lead to the cooling of the planet. Just as a day is cooler when it is cloudy than when it is sunny because the clouds block the solar radiation, perhaps smog would have the same effect.
In the late 1960’s a few scientists published articles in peer reviewed journals and gave talks at climatology meetings presenting these ideas. But this was, based on an analysis in the AMS paper, a distinctly minority view.
Unfortunately the story was picked up by the “main stream media” and Newsweek published a story in 1975 called “The Cooling World.” The New York Times also published two articles discussing the possibility of global cooling. The Times, unlike Newsweek, did note that this was far from a consensus view on the impact of pollution on the environment. In fact, as noted above, it was the decidedly minority view. There is a chart on page 9 of the paper (Fig 1, pg. 1333 of the original Journal article) that shows the number of papers on global warming versus papers on the possibility of cooling in the peer reviewed journals. There was one article discussing the possibilities of global cooling in 1967, two in 1971, and one in ’74. ‘76, and ’77. In contrast, there was 1 warming article in ’65, ’67, ‘69 and 1971. There were two in 1970, 4 in ’71, 3 in ’74, 7 in both ’75 and ’77, 4 in ’76, 8 in ’78 and 5 in 1979. All total for the period, there were 7 cooling articles, 44 warming articles, and 20 that discussed issues of climate change but were neutral as to whether the overall climate may warm or cool.
Climatologist debated the issue, analyzed the data, and found it lacking. The “debate” over “global cooling” in the late 1960’s and early 1970’s took place in scientific journals, and shows how science works. An idea is proposed, and then it is analyzed and written about in journals. If facts support the idea it becomes consensus science. If facts don’t support it, it gets dropped. This is precisely what happened with the scientific discussion of global “cooling.”
Global cooling was proposed in the mid-1960’s as a plausible idea, but climatologists and other scientists analyst the information and determined that it was incorrect. The idea was dropped by climate scientists. Unfortunately the fact that the debate, or actually only part of the debate, became public, gave the general public the sense that there was disagreement or discord in the science. Nothing could be further from the truth. The “debate” over the possibility of global cooling shows that science works.