million. By 1970 it had risen to 325 parts per million, and by 1990 it would reach 354 parts. Fitted on a graph, this rising line became known as the Keeling Curve. Based upon the trend that Keeling had identified, the carbon dioxide in the atmosphere would double around the middle of the twenty-first century. But what could increasing carbon mean for climate?
The International Geophysical Year provided a kind of an answer, if at least by analogy. Until then the planet Venus had been the province of magazines like Astounding Science Fiction. But now scientists began to understand from the IGY study of Venus what the greenhouse effect could mean in its most extreme form. With higher concentrations of greenhouse gases in its atmosphere, the surface of Venus was hellishly hot, with temperatures as high as 870°F. Venus would eventually become a metaphor for climate change run amuck.16
Year after year, Keeling pursued his measurements, working doggedly with his small team, improving the accuracy, meticulous in details, building up the register of atmospheric carbon. Revelle was to look back on Keeling’s work as “one of the most beautiful and important sets of geochemical measurements ever made, a beautiful record.” At Scripps, Keeling was known for his obsessional interest in his subject. Once the chemist Gustaf Arrhenius was rushing his pregnant wife, who was going into labor, to the hospital. Keeling flagged the car down on the Scripps campus and launched into an intricate discussion of some challenge of carbon dioxide measurement. Finally, after his wife signaled that she was not going to be able to hang on much longer, Arrhenius interrupted. “I’m sorry,” he said. “We’re going to have a baby now.” He added, “In a few minutes.” At that point, Keeling finally realized what was going on and waved them off.17
Keeling’s work marked a great transition in climate science. Estimating carbon in the atmosphere was no longer a backward-looking matter aimed at explaining the mystery of the ice ages and the advance and retreat of glaciers in past millennia. It was instead becoming a subject about the future. By 1969 Keeling was confident enough to warn of risks from rising carbon. In 30 years, he said, “if present trends are any sign, mankind’s world, I judge, will be in greater immediate danger than it is today.”
As a result of Charles Keeling’s work on atmospheric carbon, the littleknown Callendar Effect gave way to the highly influential Keeling Curve. Keeling’s work became the foundation for the modern debate over climate change and for the current drive to transform the energy system. Indeed, Keeling’s Curve became “the central icon of the greenhouse effect”—its likeness engraved into the wall of the National Academy of Sciences in Washington, D.C.18
“GLOBAL COOLING” : THE NEXT ICE AGE?
During these years concern was rising about climate change, but for a variety of reasons. Some in the national security community worried about climate change as a strategic threat: they feared the Soviet Union would alter the climate, either intentionally for military advantage or accidentally, as a result of diverting rivers or such “hare-brained” ideas as the proposal to dam the Bering Straits.19
The implications of Keeling’s work on carbon were beginning to seep into the policy community. A 1965 report on “environmental pollution” from President Lyndon Johnson’s Science Advisory Committee included a 22-page appendix written by, among others, Revelle and Keeling. It reiterated the argument that “by burning fossil fuels humanity is unwittingly conducting a vast geophysical experiment” that almost certainly would change temperatures.
KEELING’S CURVE: ATMOSPHERIC CO2 LEVELS
Measured at Mauna Loa Observatory
PREHISTORIC CO, LEVELS
Data from Antarctic ice cores
Source: NOAA Earth System Research Laboratory, Carbon Dioxide Information Analysis Center
In 1969, picking up on this and other research, Nixon White House adviser (and later senator) Daniel Patrick Moynihan wrote a memo arguing that the new Nixon administration “really ought to get involved” with climate change as an issue. “This very clearly is a problem” and “one that can seize the imagination of persons normally indifferent to projects of apocalyptic change.” The research, he said, indicated that increasing CO2 in the atmosphere could raise the average temperature by seven degrees by 2000 and sea levels by ten feet. “Good-bye New York,” he said. “Good-bye Washington, for that matter.” He had one piece of good news, however: “We have no data on Seattle.”
Yet these early statements notwithstanding, at least as much of the discussion was about global cooling as about global warming. As the deputy director of the Office of Science and Technology wrote back