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In doing some work yesterday, I ran across an article in The Bulletin of the American Meteorological Society from July 2008. The reason I stumbled across it:  it's number 1 in the list of top 20 viewed articles on the American Meteorological Society (AMS) website. The title: "The Myth of the 1970s Global Cooling Scientific Consensus".

One of the biggest pieces of misinformation about climate research from the past is that there was a period where many experts believed that we were heading to a new ice age, and that global cooling would result in reduced crop yields, and serious famine.  The truth to be found in the meteorological and climate journals from that time is a little bit different. Follow me below.

The title of the article, "The Myth of the 1970s Global Cooling Climate Consensus", by Thomas Peterson of the National Climate Data Center (Asheville NC), William Connolly of the British Antarctic Survey, National Environmental Research Council (Cambridge UK), and a journalist, John Fleck from the Albuquerque Journal, pretty much tells it all, along with the highlight shown at the top, directly beneath the title:

There was no scientific consensus in the 1970s that the Earth was headed into an imminent ice age. Indeed, the possibility of anthropogenic warming dominated the peer-reviewed literature even then.

The article content begins with a discussion of a presentation before the American Academy for the Advancement of Science (AAAS) in 1972 by Reid Bryson, one of the pioneers of climate research, urging that resources be used to study possible anthropogenic impacts upon the climate system. The first dim outlines of what would become known as "climate change" and "global warming" were beginning to be discerned:

  • We'd just found out about rising levels of CO2 from Mauna Loa and Antarctica observations that started in 1957
  • The first simple climate models were indicating that increasing CO2 levels would result in warming
  • Newly constructed temperature time series temperature were indicating a cooling that started in the 1940s
  • Scientists were looking at aerosols as a possible cause of this cooling.

Bryson in a 1974 article in Science, further outlined the requirements for climate investigation by posing 4 questions:

i) How large must a climate change be to be important?
ii) How fast can the climate change?
iii) What are the causal parameters, and why do they change?
iv) How sensitive is the climate to small changes in the causal parameters?

These are clearly the important questions to ask, and much of the work has been done since they were posed, using increasingly sophisticated climate models; reconstructions of past climates, including the composition of the atmosphere; and study of the many internal and external elements that impact the climate system. The authors of this article pose a fifth question; why, when scientists were actively working on answering these questions during the rest of the 70s, did this global cooling myth take hold, and continue to this day?  

Climate Truth in Peer-Reviewed Journals vs. Truthiness in Popular Literature

I think it's safe to say that part of the answer lies in the desire of those who benefit from the carbon-based/energy extraction industries began to see the writing on the wall, and decided to fight tooth and nail against the scientists doing this work. In fact, a strategy was decided on that was strikingly similar to that used by the tobacco industry, as medical and health scientists began to find evidence that smoking was a leading cause of lung cancer and heart disease, among other things. This link has been diaried here a number of times, including here and here.  But I digress.

It turns out that, as seems to be typical of the right wing, they use the media and even original research, to create a story through misquotes, out of context quotes, and downright lies (see below). The first side bar in the article lists some of the vehicles for perpetuating the global cooling consensus climate myth. Included are the usual suspects:  Pat Michaels, Fred Singer, and so on.

A second sidebar discusses popular (as opposed to peer-reviewed) literature from the '70s that popularized the notion of a scientific consensus on global cooling.  The article itself states, in reference to such literature (emphasis added):

When the myth of the 1970s global cooling scare arises in contemporary discussion over climate change, it is most often in the form of citations not to the scientific literature, but to news media coverage. That is where U.S. Senator James Inhofe turned for much of the evidence to support his argument in a U.S. Senate floor speech in 2003 (Inhofe 2003).

In fact, Inhofe in the same speech uses a partial quote found in a the Washington Post op-ed page (Schlesinger 2003) to make a point that was pretty much the opposite what was intended in a report from the National Science Board. Here's the actual truth:

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" (Schlesinger 2003). The quote repeatedly appeared other places in the political debate over climate change, including the floor of the U.S. Senate where Inhofe (2003) followed
up that quote by stating, "That was the same timeframe that the global-warming alarmists are concerned about global warming."

But what did the report say? Note from the quote above, which I've put in bold, what wasn't included, and MY emphasis in italics:

Judging from the record of the past interglacial ages, the present time of high temperatures should be drawing to an end, to be followed by a long period of considerably colder temperatures leading to the next glacial age 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. (National Science Board 1972).

The report actually goes on to name uncertainties in determining the net effect of human activities such as deforestation and dust and aerosol addition (cooling through albedo changes) and carbon fuel burning (warming through increased opacity of the atmosphere to long-wave radiation), volcanism, and other factors.  Certainly there is no consensus on cooling indicated in this writing from 1972.

The True Consensus: Weaving together elements of climate science

One of the first mentions of global warming as a possible threat appeared in a report prepared by the President's Science Advisory Committee for Lyndon Johnson on anthropogenic atmospheric pollution in 1965 included mention of CO2 and the potential warming affect of increasing concentrations. During the 1960s through middle 1970s, isolated groups of scientists who would later join together to create the "climate science enterprise" were learning about pieces of what would turn out to be part of the global warming puzzle.

The separate threads include:

  1. Atmospheric chemistry and the anthropogenic contribution to greenhouse gas increases
  2. The effect on atmospheric scattering and reflectivity of aerosols (both human-made and naturally occurring)
  3. The behavior of land-based ice sheets and polar sea ice in response to climate change
  4. The relationship of past CO2 levels to temperature, and the mechanisms by which those levels changed (obtained from ice cores from Greenland and Antarctica)
  5. The amplitude and speed of past climate changes detected in the ice core and other records
  6. Coupling of the earth, atmosphere, oceans, and ice in a unified climate model, with physical processes that accurately reproduce the effects of clouds, precipitation, aerosols, radiative transfer at solar and terrestrial wavelengths
  7. The effect of solar insolation variations (including the impact of variations in the earth's orbit and axial tilt) on earth's climate

and I'm sure there are some additional items I've missed.

The physical processes behind the link between long-wave-absorbing gases in the atmosphere and global warming are pretty well understood. Those ice cores have shown us that past CO2 levels have been directly correlated with temperature; the argument that CO2 slightly lagged temperature in the past does not disprove it as a cause of global warming, since other processes, primarily changes in earth's orbit, were the proximate cause back then, not CO2 levels. As we know well, that is certainly not the reason for it now, and CO2 levels are now higher than at any time over the past million years or more. What's saving us so far is the thermal inertia of both the oceans and the existing land and sea ice.

It has also become clear that sudden changes in climate on the order of years or at most a century have occurred in the past. One of those, the so-called "Younger Dryas" after the end of the previous glacial maximum, likely was caused by a collapse of the global ocean circulation caused by a sudden influx of lighter, fresh water into the area near Greenland from ice sheet melt over North America. Currently, land ice loss in the Northern Hemisphere has caused enough concern for the U.S. Department of Defense to study U.S. security impacts of sudden climate shifts that might occur from a collapse of the Gulf Stream, resulting from a slowdown in the global ocean circulation.

Work with the radiative effects of aerosols has helped to explain the temporary cooling noted from the 1940s to the 1970s, because of their reflective properties. Once included, the temperature patterns noted in nature were more faithfully reproduced in climate models. Work continues on the effect of clouds on global warming, and the uncertainty introduced by our imperfect understanding has been reduced accordingly.

The impact of other greenhouse gases such as ozone (absorbs both short- and long-wave radiation) has been implicated in other unexplained observations, such as the cooling in parts of Antarctica.  The chloro-fluorocarbons used for air conditioning depleted ozone, resulting in abnormally low levels and allowing more terrestrial/long-wave radiation to escape to space in the Antarctic regions because they radiate at colder temperatures than the Arctic (as low as −60 to −80°C rather than the -40°C in the Arctic).

Climate modeling continues to improve, as does our understanding of past climates both through reconstructions of past climates through use of all kinds of proxies such as tree-rings, C-14 and O-18 isotopes, sea and lake sediment contents, fossil pollen records, and so on.

The Tale of a Table and Two Graphics

Back to the myth of the scientific consensus on global cooling; the authors did a study of peer-reviewed articles and citations of them from 1965 through 1979. For the citations, they extended the period to 1983.  Below is a table of articles over that time, reproduced as a graphic. They are broken down by year, into "global cooling", "neutral", and "global warming" categories, based on the conclusions that were drawn in the article. Note the preponderance of global warming articles, especially later in the period; that was interesting a time when the U.S. suffered through 3 consecutive much colder than normal winters (1976-77 through 1978-79).


It's clearer to look at a graphic of the same information from the article, shown below. Individual years' data are shown with bars (color coded blue for global cooling, yellow for neutral, red for global warming). There were 44 articles concluding that global warming was a concern, versus 20 neutral articles and only 7 with global cooling. More than 1/2 of the cooling articles were written before 1972, while more than 1/2 of the warming articles were written after 1975.


The number of citations shows even a more striking story.  The year in the graphic is when the article was written, not when the article was cited later under peer-review.  Citations for articles concluding global cooling is a problem numbered about 350, neutral about 400, and that global warming is a problem about 2050. More than half the global warming citations were after 1974, almost all of the cooling citations were before 1971.



The idea that there was a consensus in the scientific community that global cooling was soon to occur was false; if anything, a consensus was beginning to be reached that global warming was the problem. The false notion has been promulgated and funded mostly by those with a vested interest in sowing confusion in the service of continuation of what the Intergovernmental Panel on Climate Change (IPCC) calls "business as usual". Business as usual, according to climate models, will increase global temperatures somewhere between 1.1°C (2°F) and 6.4°C (11.5°F).

Unfortunately, we've already most likely built in what an ensemble of climate models has shown to be about a 2°C planetary warming even if we were to stop adding CO2 tomorrow.  Many changes that have been observed, especially in sensitive regions such as the Arctic, that have been faster than have been predicted by climate models, which in spite of what some believe, actually tend to be conservative in there estimates of impacts on the climate of changes in the climate system.

Misunderstandings, both unintentional and intentional, have been used to "cloud" the issue of anthropogenic global warming for the general public. And short-term changes in climate, such as the cooler summer we had this year in the eastern and north-central part of the U.S. and the snowy winters across the north the last couple of years, have been used to mislead the public as to the reality of global warming and its causation, mainly, US.

It seems unlikely that the political and economic will exists to make the requisite changes. I hope I'm wrong; perhaps the recent low solar activity will buy us a few more years to get our collective act together. Unfortunately, it seems to take a huge catastrophe to get human beings to act, and sometimes, we don't act properly when it comes.  Just consider our response to 9/11. And even then, this particular huge catastrophe may be too much for us to recover from without massive loss of life.

I guess there's always HOPE. :-)

Originally posted to billlaurelMD on Sun Sep 27, 2009 at 08:41 PM PDT.

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