Living in the Greenhouse

By ANDREW C. REVKIN

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.

To be continue in other article...

(Jakarta, Senin 19 February 2008, 10.32 pagi)

Re-publish by Jacob Paradox from link (www.nytimes.com)