Media Influences: Ice Age Predictions
Media Influences: Ice Age Predictions
In the 1970s, scientific opinion hesitated briefly between the possibility that the world was facing an Ice Age or a period of warming. The claim that scientists falsely predicted a new Ice Age is often made in an effort to discredit the contemporary scientific consensus that global warming is real. However, no unequivocal claims of an impending Ice Age were made in the scientific literature, and it was never the consensus view of scientists that the world was about to undergo major cooling. Some mass media outlets, selecting and exaggerating scientific statements about the possibility of global cooling, did issue alarmist reports about imminent cooling.
Historical Background and Scientific Foundations
In the 1930s, British engineer Guy Stewart Callendar (1898-1964) analyzed surface temperature records dating
WORDS TO KNOW
AEROSOL: Particles of liquid or solid dispersed as a suspension in gas.
CALLENDAR EFFECT: Global warming due to atmospheric carbon dioxide released by burning fossil fuels. Named after Britsh engineer Guy Stewart Callendar (1898–1964), who proposed in the 1930s (erroneously) that weather records already showed such warming.
FOSSIL FUELS: Fuels formed by biological processes and transformed into solid or fluid minerals over geological time. Fossil fuels include coal, petroleum, and natural gas. Fossil fuels are non-renewable on the timescale of human civilization, because their natural replenishment would take many millions of years.
FOURTH ESTATE: The media. The term dates to eighteenth-century France, where political power was supposedly assigned to three “Estates” or groups, namely the clergy, nobles, and commoners. Some commentators suggested that the press was so powerful (through its ability to sway opinion) that it might be considered a fourth Estate. The term “fourth estate” implies media independence, which does not always exist: state- and corporate-controlled media usually serve as extensions of the power groups that own them, not as independent forces.
GREENHOUSE GASES: Gases that cause Earth to retain more thermal energy by absorbing infrared light emitted by Earth's surface. The most important greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and various artificial chemicals such as chlorofluorocarbons. All but the latter are naturally occurring, but human activity over the last several centuries has significantly increased the amounts of carbon dioxide, methane, and nitrous oxide in Earth's atmosphere, causing global warming and global climate change.
MILANKOVITCH FORCING: Increases or decreases in the amount of thermal energy being absorbed by Earth's climate system governed by Milankovitch cycles, that is, regularly repeating variations in Earth's climate caused by shifts in its orbit around the sun and its orientation (i.e., tilt) with respect to the sun.
SULFATE AEROSOLS: Tiny airborne particles (aerosols) containing sulfur that form from gases emitted to the atmosphere by oceanic phytoplankton, the burning of fossils fuels (especially coal), and volcanoes. Sulfate aerosols have a cooling effect on climate, though not enough to reverse the warming effect of greenhouse-gas emissions. About eighty percent of sulfate aerosols come from human activities such as coal-burning and copper smelting.
back to the nineteenth century and concluded that the world was warming. The temperature data were ambiguous and ever-changing, however, and the Callendar effect, as it was called, was widely disputed over the next several decades.
Climate science began to mature in the 1950s through the 1970s as mathematical models of the effects of aerosols (small particles suspended in the atmosphere) and carbon dioxide (CO2) began to be developed. Scientists knew that human beings were putting both aerosols and CO2 into the atmosphere by burning fossil fuels, but found it difficult to predict whether this would cause warming or cooling; sulfate aerosols, the dominant type, cause cooling by scattering sunlight back into space, while CO2 warms climate by causing Earth to retain energy. Moreover, a cooling trend had actually occurred in the Northern Hemisphere from the 1940s to the 1970s.
Based on cautious scientific statements that global cooling had been observed and might possibly continue, some popular media made alarming proclamations about an imminent Ice Age. For example, the news magazine Newsweek ran a story titled “The Cooling World” on April 28, 1975, which stated that “the world's climate seems to be cooling down.” The article also claimed that meteorologists were “almost unanimous in the view that the trend will reduce agricultural productivity for the rest of the century”—a frightening prospect. However, the scientific literature of the day never predicted an imminent Ice Age. The scientific consensus view during the 1970s was that scientific knowledge was still too incomplete to allow climate forecast. This changed from about 1980 onward, as the science solidified. By 1990, a consensus had emerged that global warming due to human-released greenhouse gases was happening. Decades of subsequent science have confirmed this view.
Impacts and Issues
See-sawing popular media claims about climate change, and especially media accounts of a coming Ice Age in the 1970s, have been cited by climate change skeptics in an effort to undermine the credibility of global warming. These claims seek to discredit present-day science by pointing to the past exaggerations of newspapers.
An example of this use of 1970s Ice Age predictions is conservative pundit George Will's statement in 2004 that “30 years ago the fashionable panic was about global cooling.” Will urged his readers to remember “yesterday's discarded certitudes” so that they will be “wholesomely skeptical of today's.” He cited articles from mass media that spoke of global cooling, but quoted only one from the scientific literature, namely the 1976 Science magazine article “Variations in the Earth's Orbit: Pacemaker of the Ice Ages,” by J. D. Hays, John Imbrie, and N. J. Shackleton.
Will claimed that Hays and colleagues “warned about ‘extensive Northern Hemisphere glaciation.’” However, others have noted that Will took the quote out of context. Specifically, the scientists spoke explicitly of how natural climate forces would operate “in the absence of human perturbation of the climate system” and made no predictions about the near future. Rather, they said that considering orbital factors alone (Milan-kovitch forcing), “the long-term trend over the next 20,000 years is towards extensive Northern Hemisphere glaciation and cooler climate.” Thus, the scientists made no panicky claims that an Ice Age was about to strike.
IN CONTEXT: ASTRONOMICAL INFLUENCE ON ICE AGES
By the beginning of the twentieth century, astronomers had identified three factors that almost certainly are major contributors to the amount of solar radiation that reaches Earth's surface and, hence, Earth's average annual temperature. These three factors are Earth's angular tilt, the shape of its orbit around the sun, and its axial precession.
The first of these factors, angular tilt, is the angle at which Earth's axis is oriented to the plane of its orbit around the sun. This angle slowly changes over time, ranging between 21.5 and 24.5 degrees. At some angles, Earth receives more solar radiation and becomes warmer, and at other angles it receives less solar radiation and becomes cooler.
The second factor, the shape of Earth's orbit around the sun, is important because, over long periods of time, the orbit changes from a nearly circular to a more elliptical (flatter) shape. As a result of this variation, Earth receives more or less solar radiation depending on the shape of its orbit. The final factor, axial precession, is a wobble in the orientation of Earth's axis to its orbit around the sun. As a result of axial precession, the amount of solar radiation received during various parts of the year changes over very long periods of time.
Between 1912 and 1941, the Yugoslav astronomer Milutin Milankovitch developed a complex mathematical theory that explained how the interaction of these three astronomical factors could contribute to the development of an ice age. His calculations provided approximations of the occurrences of ice ages during Earth history.
The assumption that scientists widely agreed on global cooling in the 1970s is widespread, although that was not the case. For example, prestigious British sociologist Anthony Giddens claimed in his 1999 Reith Lecture that “only about 25 or so years ago, orthodox scientific opinion was that the world was in a phase of global cooling.”
Another prominent speaker who has made frequent references to past ice-age predictions is Senator James Inhofe (R-OK). In a speech on the Senate floor in September 2006, Inhofe, who has called global warming a “hoax,” argued that “Since 1895, the media has alternated between global cooling and warming scares during four separate and sometimes overlapping time periods…. From the 1950s until the 1970s they warned us again of a coming ice age. This makes modern global warming the fourth estate's fourth attempt to promote opposing climate change fears during the last 100 years.”
Others contend that media coverage of global warming science for over a decade has presented a falsely balanced picture of scientific opinion, often giving equal weight to the opinions of a small minority of global-warming skeptics, while failing to communicate that the overwhelming majority of scientists agree that global warming is real.
In any case, the faults or virtues of popular media do not affect the scientific evidence itself. Today's scientific consensus that humans are causing global climate to change, as illustrated in a 2007 report by the Intergovernmental Panel on Climate Change (IPCC), is based on decades of work and thousands of studies, and is historically unprecedented.
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Hays, J. D., et al. “Variations in the Earth's Orbit: Pacemaker of the Ice Ages.” Science (December 10, 1976).
Will, George. “Global Warming? Hot Air.” The Washington Post (December 23, 2004).
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“Inhofe to Blast Global Warming Media Coverage in Speech Today on the Senate Floor.” U.S. Senate Committee on Environment and Public Works, September 25, 2006. <http://epw.senate.gov/public/index.cfm?FuseAction=PressRoomPressReleases&Content Record_id=7ce43ec4-41a8-4c1f-a881-b9c4e361cd89&Issue_id=87c0c861-7e9c-9af9-71bf-36f732341882> (accessed October 28, 2007).
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