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Charles David Keeling, 77; Scientist Linked Humans to Increase in Greenhouse Gas

June 24, 2005|Thomas H. Maugh II | Times Staff Writer

Charles David Keeling, the climate scientist whose precise, meticulous measurements of carbon dioxide in the atmosphere for nearly half a century warned humans that we are changing the composition of the global atmosphere, has died. He was 77.

Keeling suffered a heart attack Monday while hiking with one of his sons near the family's summer home in Montana, according to a spokesman for the Scripps Institution of Oceanography, where he spent virtually his entire professional career.

Keeling's studies showed that the atmospheric concentration of carbon dioxide -- a so-called greenhouse gas that traps energy from sunlight and prevents it from radiating back into space -- has been rising steadily since the onset of the Industrial Age, and he linked that growth conclusively to the increased consumption of fossil fuels, which release carbon dioxide when they are burned.

The graph showing that increase, known as the Keeling curve, is one of the best-known anywhere. "During the early 1990s, it was said that the only scientific data on display at the White House was [the Keeling curve]," said Ralph Cicerone, president of the National Academy of Sciences.

Politicians and scientists may disagree over whether the increased carbon dioxide concentrations are causing the planet to heat up, but no one questions the accuracy of Keeling's data and its link to human activities.

Even President George W. Bush, who has repeatedly discounted the possibility of global warming, recognized the importance of Keeling's work by awarding him the National Medal of Science in 2002. In April, Keeling received the Tyler Prize for Environmental Achievement, the most prestigious award for environmental research.

Keeling's records of carbon dioxide concentrations "are the single most important environmental data set taken in the 20th century," said Charles F. Kennel, the director of Scripps. "Dave Keeling was living proof that a scientist could, by sticking close to his laboratory bench, change the world."

Keeling began his career as a postdoctoral fellow at Caltech, where he conceived and built the first instrument to measure the concentration of carbon dioxide in atmospheric samples. He was entering uncharted territory. Estimates of the amount of the gas in the air ranged from 150 parts per million to 450 ppm. Most researchers, moreover, assumed that because the atmosphere was well mixed, the concentration showed little variance, even from year to year.

Using his new device, Keeling camped at Big Sur State Park for three weeks, measuring carbon dioxide. He concluded that the gas was present at about 310 ppm, significantly above the 280-ppm level measured in ice cores from the 19th century.

Roger Revelle, then-director of Scripps and one of the founders of the International Geophysical Year of 1957-58, lured him to Scripps and put him in charge of measuring carbon dioxide levels. In 1958, Keeling established a base 2 miles high on Mauna Loa volcano in Hawaii, well above the world's pollution, which might have skewed the measurements, and began measuring gas levels day by day.

What he found astonished scientists throughout the world.

By 1960, he had shown that carbon dioxide exhibited strong seasonal cycles, with a variation of as much as 3% over the course of the year.

The highest levels are reached in late winter in the Northern Hemisphere. The onset of spring causes a sharp reduction as plants begin growing, soaking up carbon dioxide to fuel their increased mass. The lowest concentration coincides with the end of the growing season. As the plants begin decaying, releasing their stored carbon dioxide back into the air, concentrations begin rising again until they reach a peak before the new growing season.

The cycle coincides with seasons in the Northern Hemisphere because that is where the bulk of the world's land surface is.

Keeling measured "the breathing of the world," said Jonathan Weiner in his book, "The Next One Hundred Years."

As the measurements continued at Mauna Loa and other, newer sites, Keeling observed an average growth in carbon dioxide concentrations of about 1 ppm per year, reaching nearly 380 ppm now. Most scientists attribute that growth to consumption of fossil fuels by industry and in automobiles.

Keeling's work required persistence. In the early 1960s, the National Science Foundation stopped supporting his studies, calling them "routine" and unworthy of funding.

Later, other government agencies attempted to usurp his measurements. In 2004, Keeling explained the conflict in simple terms: "You set up a dry-cleaning establishment, and somebody comes along and decides he wants a dry-cleaning establishment, and the best way is to get rid of yours."

With help from his friends at Scripps and in Washington, Keeling prevailed. Today, his monitoring station on Mauna Loa sits next to a similar installation operated by the National Weather Service.

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