-- The supposed "global cooling" consensus among scientists in the 1970s — frequently offered by global-warming skeptics as proof that climatologists can't make up their minds — is a myth, according to a survey of the scientific literature of the era.
The '70s was an unusually cold decade. Newsweek, Time, The New York Times and National Geographic published articles at the time speculating on the causes of the unusual cold and about the possibility of a new ice age.
But Thomas Peterson of the National Climatic Data Center surveyed dozens of peer-reviewed scientific articles from 1965 to 1979 and found that only seven supported global cooling, while 44 predicted warming. Peterson says 20 others were neutral in their assessments of climate trends.
The study reports, "There was no scientific consensus in the 1970s that the Earth was headed into an imminent ice age.
"A review of the literature suggests that, to the contrary, greenhouse warming even then dominated scientists' thinking about the most important forces shaping Earth's climate on human time scales."
"I was surprised that global warming was so dominant in the peer-reviewed literature of the time," says Peterson, who was also a contributor to the United Nations' Intergovernmental Panel on Climate Change 2007 report.
Scientific reports in the past decade, most notably the U.N. panel's Nobel Prize-winning efforts, have warned that human activities are warming the planet by increasing the release of heat-trapping "greenhouse" gases into the atmosphere.
Skeptics have argued that climate change is cyclical, not fueled by the burning of fossil fuels — coal, oil and natural gas. Peterson notes in the study that concerns over the frigid 1970s subsequently became representative of scientific division over global warming.
That was an unusually cold decade, especially the later years, across the Northern Hemisphere. In the USA, the winters of 1977-79 were three of the 11 coldest since the recording of temperatures began in the 1890s, according to climate center data. The winter of 1978-79 remains the coldest on record in the USA.
Just as it's hard for people today to think much about global warming in the dead of winter, it was also hard for the public – and the media – to focus on a warming world, while at the same time enduring some of the coldest winters on record.
However, as Peterson notes in the paper, "even cursory review of the news media coverage of the issue reveals that, just as there was no consensus at the time among scientists, so was there also no consensus among journalists."
Some have doubts about the new survey. "The paper does not place the late '70s in its climatic context," says Pat Michaels, a senior fellow in environmental studies at the Cato Institute in Washington, D.C.
"The temperature records we had at the time showed a very sharp cooling from the mid-'40s to the mid-'70s," Michaels says. "And scientists attempted to explain that as a consequence of the pollution that was preventing solar radiation from reaching the surface.
"At the time, scientists thought the cooling effect of pollution was greater than the warming effect of carbon dioxide," Michaels adds. "They were attempting to explain the dramatic cooling of the '70s."
But Robert Henson, a writer at the National Center for Atmospheric Research and author of The Rough Guide to Climate Change, says: "This is an important part of science history, and Peterson and his co-authors have done a great job of excavating it.
"People have long claimed that scientists in the 1970s were convinced a new ice age was imminent. But in fact, many researchers at the time were already more concerned about the long-term risks of global warming."
Along with Peterson, the study was also authored written by William Connolly of the British Antarctic Survey and John Fleck of The Albuquerque Journal. The research will be published in the Bulletin of the American Meteorological Society.