Temperature Rising - A Scientist, His Work and a Climate Reckoning

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“It took a lot of work to maintain this attractive gap,” Ralph Keeling recalled, but he said his father believed “that was just the right way to do it, and if you didn’t do that, you were cutting corners. It was a moral breach.”

Dr. Keeling was a punctilious man. It was by no means his defining trait — relatives and colleagues described a man who played a brilliant piano, loved hiking mountains and might settle a friendly argument at dinner by pulling an etymological dictionary off the shelf.

But the essence of his scientific legacy was his passion for doing things in a meticulous way. It explains why, even as challengers try to pick apart every other aspect of climate science, his half-century record of carbon dioxide measurements stands unchallenged.

By the 1950s, when Dr. Keeling was completing his scientific training, scientists had been observing the increasing use of fossil fuels and wondering whether carbon dioxide in the air was rising as a result. But nobody had been able to take accurate measurements of the gas.

As a young researcher, Dr. Keeling built instruments and developed techniques that allowed him to achieve great precision in making such measurements. Then he spent the rest of his life applying his approach.

In his earliest measurements of the air, taken in California and other parts of the West in the mid-1950s, he found that the background level for carbon dioxide was about 310 parts per million.

That discovery drew attention in Washington, and Dr. Keeling soon found himself enjoying government backing for his research. He joined the staff of the Scripps Institution of Oceanography, in the La Jolla section of San Diego, under the guidance of an esteemed scientist named Roger Revelle, and began laying plans to measure carbon dioxide around the world.

Some of the most important data came from an analyzer he placed in a government geophysical observatory that had been set up a few years earlier in a remote location: near the top of Mauna Loa, one of the volcanoes that loom over the Big Island of Hawaii.

He quickly made profound discoveries. One was that carbon dioxide oscillated slightly according to the seasons. Dr. Keeling realized the reason: most of the world’s land is in the Northern Hemisphere, and plants there were taking up carbon dioxide as they sprouted leaves and grew over the summer, then shedding it as the leaves died and decayed in the winter.

He had discovered that the earth itself was breathing.

A more ominous finding was that each year, the peak level was a little higher than the year before. Carbon dioxide was indeed rising, and quickly. That finding electrified the small community of scientists who understood its implications. Later chemical tests, by Dr. Keeling and others, proved that the increase was due to the combustion of fossil fuels.

The graph showing rising carbon dioxide levels came to be known as the Keeling Curve. Many Americans have never heard of it, but to climatologists, it is the most recognizable emblem of their science, engraved in bronze on a building at Mauna Loa and carved into a wall at the National Academy of Sciences in Washington.

By the late 1960s, a decade after Dr. Keeling began his measurements, the trend of rising carbon dioxide was undeniable, and scientists began to warn of the potential for a big increase in the temperature of the earth.

Dr. Keeling’s mentor, Dr. Revelle, moved to Harvard, where he lectured about the problem. Among the students in the 1960s who first saw the Keeling Curve displayed in Dr. Revelle’s classroom was a senator’s son from Tennessee named Albert Arnold Gore Jr., who marveled at what it could mean for the future of the planet.

Throughout much of his career, Dr. Keeling was cautious about interpreting his own measurements. He left that to other people while he concentrated on creating a record that would withstand scrutiny.

John Chin, a retired technician in Hawaii who worked closely with Dr. Keeling, recently described the painstaking steps he took, at Dr. Keeling’s behest, to ensure accuracy. Many hours were required every week just to be certain that the instruments atop Mauna Loa had not drifted out of kilter.

The golden rule was “no hanky-panky,” Mr. Chin recalled in an interview in Hilo, Hawaii. Dr. Keeling and his aides scrutinized the records closely, and if workers in Hawaii fell down on the job, Mr. Chin said, they were likely to get a call or letter: “What did you do? What happened that day?”

In later years, as the scientific evidence about climate change grew, Dr. Keeling’s interpretations became bolder, and he began to issue warnings. In an essay in 1998, he replied to claims that global warming was a myth, declaring that the real myth was that “natural resources and the ability of the earth’s habitable regions to absorb the impacts of human activities are limitless.”

Still, by the time he died, global warming had not become a major political issue. That changed in 2006, when Mr. Gore’s movie and book, both titled “An Inconvenient Truth,” brought the issue to wider public attention. The Keeling Curve was featured in both.

by NYtimes