Living in the Greenhouse
By Andrew C. Revkin
Published: October 5, 2003
OF GLOBAL WARMING
By Spencer R. Weart.
228 pp. Cambridge, Mass.:
Harvard University Press. $24.95.
EUREKA moments are rare in science. Achievements like the deduction of DNA's structure etch our imagination precisely because they are exceptional. In most fields, research is more akin to climbing a mist-shrouded mountain of unknown dimensions. Climate science, perhaps above all, has been a perpetual ascent toward understanding. A major achievement so far is a broad consensus that beginning in the industrial era humans, by burning ancient buried stores of carbon-rich coal and oil, have liberated billions of tons of heat-trapping greenhouse gases, warming earth.
Debate persists over the extent of human-driven warming and what to do about it. But recognition that in a short span our species has nudged the thermostat of a planet remains a momentous, and sobering, finding.
''The Discovery of Global Warming'' describes the intellectual journey toward that conclusion, with all of its false starts, flawed hypotheses, inventiveness and persistent uncertainties. It reveals the effort as one of the great exercises in collective sleuthing, with pivotal insights provided by experts in fields as varied as glaciology, physics and even plankton paleontology. Charting the evolution and confirmation of the theory, Spencer R. Weart, director of the Center for the History of Physics of the American Institute of Physics, dissects the interwoven threads of research and reveals the political and societal subtexts that colored scientists' views and the public reception their work received.
In many instances, he writes, researchers were pursuing knowledge for other purposes and only later were their data used to determine if humans had influenced the climate. He notes that much of the oceanographic and polar research that eventually helped point to human-driven warming was paid for by the United States Navy and other government agencies that were eager to exert American hegemony during the cold war.
The narrative starts with the 150-year-old notion that some trace gases are transparent to sunlight but opaque to infrared radiation, the radiant energy that pulses from a sun-warmed sidewalk long after dusk. This insulating property of the atmosphere prevents the planet from turning into an iceball. Weart uses excerpts from pivotal papers to let us glimpse the thinking of climatology's pioneers. Thus, in 1862, John Tyndall, a British researcher, wrote about infrared radiation, ''As a dam built across a river causes a local deepening of the stream, so our atmosphere, thrown as a barrier across the terrestrial rays, produces a local heightening of the temperature at the earth's surface.''
As the Industrial Revolution accelerated, scientists soon figured out that emissions of heat-trapping gases from burning coal and other fossil fuels might intensify that natural ''greenhouse effect.'' Chief among these gases was carbon dioxide. One omission from Weart's book is a prescient phrase written in 1896 by Svante Arrhenius, a pioneering Swedish chemist: ''We are evaporating our coal mines into the air.''
Still, the human contribution to climate was presumed to be far outweighed by the great cycles of ice ages revealed in fossil and geological records. The puzzle of those cycles remained the prime quarry of Arrhenius and others and has still not been completely solved.
A warm period in the 1930's brought the first specific predictions that humans could alter the climate, but then things cooled down for a few decades and the possibility of a human influence remained a fringe notion. (Later, Weart explains, it was shown that the temporary cooling could also have been caused by humans -- through the release of vast sun-reflecting plumes of sulfates and other tiny pollution particles in the industrial boom after World War II: one human emission was canceling out another until clean-air laws began removing the cooling veil.)
Weart next focuses on the great burst of geophysical research starting in the 1950's, when data started showing for the first time that humans were indeed changing the atmosphere. He describes how individual scientific obsessions, like Charles David Keeling's preoccupation with creating a precise record of carbon dioxide concentrations, produced vital puzzle pieces.
Increasingly, scientists working in the field began to express unease. In a 1957 paper noting that the oceans could not act as a perpetual sponge for carbon dioxide, Roger Revelle, an oceanographer at the Scripps Institution of Oceanography near San Diego, summed things up: ''Human beings are now carrying out a large- scale geophysical experiment.'' Other experts noted an unnerving aspect of the situation: the experimenters were inside their test tube. According to Weart, however, all that had been proved then was ''the possibility of global warming.'' It took another 40 years of data gathering, computer simulations and debate before an international panel of climate experts concluded in 2001 that ''most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.''
He describes how the battle between environmental groups and industries dependent on coal and oil intensified steadily as climate science became more conclusive. But that science, he emphasizes, will never offer a perfect forecast; the atmosphere, with complex links to the sun and oceans, will long remain a source of surprises. In fact, climate science will probably remain easily misconstrued by alarmists of all stripes -- both environmentalists eager to stoke public fears and antiregulatory activists and politicians fearful of any impediment to unbridled enterprise.
''The Discovery of Global Warming'' does cut through much of the persistent hype surrounding the issue. Weart has also set up a Web site, www.aip.org/history/climate, that adds many layers of detail to the scientific chronology.
In a short final chapter called ''Reflections,'' Weart offers his personal ideas on the best course of action to limit risks from warming while avoiding big economic disruptions. But he leaves a deeper discussion of the politics of global warming to others, sticking with his strengths as a historian.
He warns that society should not expect science to answer the biggest question of all: how much should be invested now either to curb emissions or gird for change. Like a flickering compass needle, science offers a trajectory toward truth, but not a recipe for dealing with it.