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The Global Cooling Myth
One of the charges that you may hear, which is intended to cast doubt on the reliability of climatologists and global warming, is that in the 1970s scientists were warning about global cooling and an impending ice age. This turns out to be mostly a myth.
Last September the American Meteorological Society (AMS) published an article in their bulletin called, "The Myth of the 1970s Global Cooling Scientific Consensus" (pdf), that explains the basis for this myth. The short version is that there had been some cooling since 1940 (see below). Climate science (which looks at long-term trends, not short-term weather) was a relatively immature science and some scientists were grappling with how aerosols could be responsible for the cooling. At the same time, other scientists were beginning to understand the pattern of long-term ice age fluctuations and predicted that on a geological time scale (i.e. thousands to tens of thousands of years), and ignoring human activities, the Earth should be heading for another ice age.
These factors combined with unusually severe winters in 1972 and 1973 and other fears of food shortages and so forth, and resulted in some hype in the mainstream media and increased public consciousness. In actuality, the effect of anthropogenic CO2 emissions was also being considered by scientists and there were already predictions of a warming trend. In fact a 1965 report by the President's Science Advisory Committee noted recent data on CO2 emissions and expressed concern about the potential for its warming effect on the climate.
The article points out that references to global cooling doom from the 1970s are usually drawn from popular publications such as Newsweek rather than the scientific literature of the time. In fact the authors did a literature search and categorized scientific publications according to whether they supported cooling, warming, or remained neutral. The following figure summarizes their results (click to enlarge):
These data suggest that the notion that climate scientists (as a group) were warning of impending cooling only to reverse course and push warming, is false.
To finish, here is the global mean temperature from 1880 to 2007. The 1940s cooling is evident, as well as the overall warming trend.
Source: NOAA, Climate of 2007 Annual Report
12 comments:
I just remember the guys preaching gloom and doom, not a scholarly consensus about the prediction that we would all freeze.
Now Greenland gets two growing seasons a year.
I remember the phrase "nuclear winter" being used a lot. Maybe that image created by Cold War politics -- even the phrase "Cold War" itself -- is why it seems that global cooling was talked about more than you say it was? Because my [fallible] memory really is that when I was in high school in the 70s, we were always hearing that we were headed toward a cold future.
Myth? I read the news magazine articles at the time. Sounds like they're trying to rewrite history.
Note: I'm too young to have personal memories of this.
Ardis,
Good point. Nuclear winter is a justified fear because the smoke, dust, etc put up into the atmosphere would block sunlight. Volcanoes or asteroids of sufficient size could cause a similar problem. (I'm sure you know that volcanoes appear to have been responsible for the 1816 "year without summer".) Though the article didn't mention it, I'll bet that the cold war fed into the worries as well.
However, I don't think any of that contradicts the claims of the article. Popular worries, or even scientific worries about dramatic circumstances such as nuclear winter, are a separate issue.
Anonymous,
You may have read the news magazines, but you don't seem to have read my post.
"The article points out that references to global cooling doom from the 1970s are usually drawn from popular publications such as Newsweek rather than the scientific literature of the time."
On nuclear winter, Colby Cosh wrote for the National Post:
"In his last great public controversy, created in 1983 by his espousal of the 'nuclear winter' hypothesis, he [Carl Sagan] went beyond the merely science-ish and flirted with positive treason against rationality.
"The nuclear winter -- every child of the Cold War will recall the terrifying phrase -- was a climate effect that Sagan and others claimed to have teased from the crude computer models of the day. Sagan argued that even a limited, local exchange of tactical nuclear weapons could create enough airborne debris to reduce temperatures by dozens of degrees worldwide, immediately and for months. The hypothesis fit snugly with Sagan's pre-existing political stance in favour of universal disarmament. He published his first paper about the subject in a popular magazine and held a televised conference before any peer-reviewed material had a chance to appear.
"He continued to expound the gospel even as improved modelling showed that the likely effect would be closer to 'nuclear autumn.' But his fancies came to an end in 1991 when he warned Western governments that ignition of the Kuwaiti oil fields by Saddam Hussein would be certain to induce the equivalent of nuclear winter. When Saddam lit the match, it was only Sagan's prestige that fell to below zero. In his 1996 book The Demon- Haunted World, he all but acknowledged that his own 'baloney detector' had suffered interference from his personal politics."
link
I vaguely remember that one of the big names pushing global cooling in the 70's is also one of the big global warming doubters.
Anyone remember the name?
I found it. It was Reid Bryson. Bryson was in the news again because of Tipler discussing him in that awful blog post last week.
Ok, stupid question from the non-science guy, but I was young in the late 80s and we didn't have cool and we had a different kind of warming we called "a whole in the ozone layer". What ever happened to that?
Matt, by coincidence I saw a talk on ozone today. Ozone is good high up in the atmosphere, where it blocks some UV light, but bad down lower where life is.
Having said that, I don't really know a lot about the subject. You can read wikipedia as well as I can.
I do remember the discussions on global cooling in the 70s. Didn't we give up our aerosol cans over that concern?
I have two big issues with the global warming theater. First, how much is done by man, versus other issues (bovine belching, solar warming, etc)? Second, why is it necessarily bad if the earth warms up? Didn't the last Little Ice Age (ca 1300) teach us that it is cooling that kills species in droves, and brings plagues? Global cooling wiped out the Viking/Norse settlements in Greenland. 10,000 years ago, the Ice Age wiped out vast numbers of species.
Meanwhile, prior to the Little Ice Age, things were warm enough for England to grow quality grapes for wine that competed well with France's vinyards.
Personally, I think the global warming fears are projected on us by the French, who fear losing their competitive edge against Britain in the wine and tourism industries.
Rameumpton, I hate to break it to you, but aerosol cans are still readily available. You've suffered needlessly.
I did read your blog posting. Poorly written.
Did you read the magazine articles from the 70's reporting global cooling? Or did you just hear about them? Scientists were the ones making claims of cooling. They were wrong, but we're supposed to believe the current scientists who promote global warming? It's BS. I attended a scholarly scientific conference where a representative from the National Atmoshperic and Oceanic Administration presented a paper refuting global warming.
Looks like another method to contol us and make money. Al Gore sells carbon offsets. Self serving.
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