What We Knew in ’72

March 20, 2014

I made the video above, “What We Knew in 82”, after discovering video of a talk given at Sandia Labs in 1982, by Dr. Mike MacCracken, then a senior researcher at Livermore Lab, and involved in DOE research on climate. The point of the piece was how much was known that long ago about the expected changes in climate due to man-caused greenhouse forcing.

Most people probably don’t know that the physics behind global warming was nailed in the 1950s by military research undertaken to produce the first generation of heat-seeking missiles – described below in a clip from Richard Alley’s “Earth: An Operator’s Manual” –

Now,  Dana Nuccitelli describes a paper in a major journal from 1972 that contains remarkable predictions made with the still-very-young science.


Dana Nucittelli in the Guardian:

John Stanley (J.S.) Sawyer was a British meteorologist born in 1916. He was elected a Fellow of the Royal Society in 1962, and was also a Fellow of the Meteorological Society and the organization’s president from 1963 to 1965.

A paper authored by Sawyer and published in the journal Nature in 1972 reveals how much climate scientists knew about the fundamental workings of the global climate over 40 years ago. For example, Sawyer predicted how much average global surface temperatures would warm by the year 2000.

“The increase of 25% CO2 expected by the end of the century therefore corresponds to an increase of 0.6°C in the world temperature – an amount somewhat greater than the climatic variation of recent centuries.”


Remarkably, between the years 1850 and 2000, atmospheric carbon dioxide levels did increase by very close to 25 percent, and global average surface temperatures also increased by just about 0.6°C during that time.

Sawyer also discussed several other important aspects of the Earth’s climate in his paper. For example, he addressed the myth and misunderstanding that as a trace gas in the atmosphere, it may seem natural to assume that rising levels of carbon dioxide don’t have much impact on the climate. Sawyer wrote,

“Nevertheless, there are certain minor constituents of the atmosphere which have a particularly significant effect in determining the world climate. They do this by their influence on the transmission of heat through the atmosphere by radiation. Carbon dioxide, water vapour and ozone all play such a role, and the quantities of these substances are not so much greater than the products of human endeavour that the possibilities of man-made influences may be dismissed out of hand.”

Indeed, over the past four decades, human carbon dioxide emissions have continued to increase more or less exponentially, and about half has continued to remain in the atmosphere with the other halfaccumulating in natural reservoirs. The carbon dioxide being absorbed by the oceans has contributed to the problem of ocean acidification, sometimes referred to as “global warming’s evil twin.”

Climate scientists also had a good idea how quickly carbon dioxide levels in the atmosphere would continue to rise as a result of human activities.

“Bolin has estimated that the concentration of carbon dioxide will be about 400 ppm by the year 2000. A recent conference put the figure somewhat lower (375 ppm).”

The latter prediction at the referenced 1971 conference on “the Study of Man’s Impact on Climate” turned out to be quite accurate. In 2000, atmospheric carbon dioxide concentrations were measured at about 370 ppm.

In his paper Sawyer discussed the predicted impacts resulting from a continued rise in atmospheric carbon dioxide. He noted that directly “it might make some vegetation grow a little faster,” which is generally true, although the situation is complicated. Sawyer noted that rising carbon dioxide levels would cause an increased greenhouse effect, and the associated warming would lead to more evaporation and more water vapor in the atmosphere. As a greenhouse gas itself, that rise in water vapor would act to further amplify human-caused global warming.

“…if world temperatures rise due to an increase in carbon dioxide, it is almost certain that there will be more evaporation of water–the water vapour content of the atmosphere will also increase and will have its own effect on the radiation balance.”

Sawyer referenced a 1967 paper by Manabe and Wetherald, who had calculated that a doubling of atmospheric carbon dioxide would by itself cause approximately 1.3°C global surface warming, but that warming would be amplified by a further 1.1°C due to rising water vapor concentrations if the relative humidity were to remain constant. Observations have indeed unequivocally shown that water vapor strongly amplifies human-caused global warming, for example as found in a 2009 study by Andrew Dessler and Sun Wong from Texas A&M University.

Sawyer also discussed that melting ice and snow in a warming world would act to amplify global warming, but suggested that increasing cloud cover might dampen global warming and act to regulate the global climate. However, recent research has shown that clouds may actually weakly amplify global warming as well. Sawyer also understood that significant global warming would cause changes in weather and wind patterns around the world.

All in all, Sawyer’s 1972 paper demonstrated a solid understanding of the fundamental workings of the global climate, and included a remarkably accurate prediction of global warming over the next 30 years. Sawyer’s paper was followed by similarly accurate global warming predictions by Wallace Broecker in 1975 and James Hansen in 1981.

This research illustrates that climate scientists have understood the main climate control knobs for over four decades. Perhaps it’s about time that we start listening to them.

The “..in the 70s they predicted an Ice Age” canard is sacred to climate deniers, of course, and I made this video early on to take that one apart. As the piece above shows, it was even shakier than I described below.

33 Responses to “What We Knew in ’72”

  1. omnologos Says:

    1. Please list John Abraham’s literature on past and present impacts of climate change

    2. The 1972 consensus on a cooling world is in the “Myth” article linked above. Just remember, one needs be honest and not expand it to the whole decade.

    Ps always surprised by the naivety of proclaiming one’s limping horse the winner, actually the “killer” of the competition

    Pps I am not a Monckton follower, before the usual stupid journo who reads these comments jumps in claiming otherwise 🙂

  2. Attempts at revisionist history are a good point to review the real history. There are so many that predicted warming, you have to go back to Svante Arrhenius in the late 1890s. The scientific predictions of AGW are as ageless as the myths and canards against it. Add Wallace Broecker to a library of scientific AGW predictions.

    • omnologos Says:

      It’s exactly to combat revisionism that dates are so important and we should stop talking about decades as if opinions were monolithic therein.

      For example in 1961 UNESCO hosted a Symposium on Climate Change. The proceedings are available online as ARID ZONE RESEARCH XX (I can provide a link if there’s any serious interest).

      The speakers mentioned a “reversal of the preceding [warming] climatic trend” with “downwards trends in temperature” as “significant from a physical point of view”. J Murray Mitchell, Jr said that the warming up to 1940 had been “planetary in scope” but wasn’t sure the “net cooling” since then was global as well.

      The concluding lecture spoke about a “warming up of large parts of the world from the middle of the nineteenth century”, but “this increase in temperature has recently declined”. Sounds like not much as changed 😉

      The American Meteorological Association also had a similar meeting in 1961, actually a 5-day conference described by Walter Sullivan of the NYT in an article titled “SCIENTISTS AGREE WORLD IS COLDER – but climate experts meeeting here fail to agree on reasons for change” (Jan 30, 1961)

      From the article’s text it looks like the conference was very lively with a lot of heated exchanges. Sullivan mentions CO2 and the greenhouse effects as “one of the chief concerns of climatologists in recent years”, plus aerosols, although the data available at the time didn’t clearly indicate that CO2 had contributed more than “some of the warming observed during the early decades of this [XX] century”.

      IMHO the historical facts are pretty clear, and anybody muddling them for example trying to delete from the record the fact the scientists agreed at some specific point in time that the world was getting colder, even if some of them expected the world to eventually get warmer because of CO2, is a denier of the worst sort.

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