Charles David Keeling, 77, the world's leading authority on carbon dioxide in the atmosphere, died of a heart attack June 20 at his summer home in Hamilton, Mont., after a short hike.

Dr. Keeling, a climate scientist at the Scripps Institution of Oceanography since 1956, was the first to measure carbon dioxide in the atmosphere on a continuing basis, and he was primarily responsible for providing data that alerted the world's scientists to the extremely serious implications of global warming for life on earth.

The graphic record of this research is named the Keeling Curve, and it is considered the basic document of global warming research. It shows that carbon dioxide has been rising at a rate of about 3 percent a year since Dr. Keeling began measuring it from a pristine-air weather station on Mauna Loa in Hawaii in 1958.

The accumulation of carbon dioxide and a related change in its isotopic composition result mainly from the worldwide burning of fossil fuels, Dr. Keeling's research and other scientific studies indicate. An overwhelming proportion of climate scientists say that the increase in carbon dioxide contributes to ozone depletion, glacial meltdown and desertification of farmland, among other changes.

Eleven science academies, including the National Academy of Science, quoted Dr. Keeling's work this month as they called on world leaders to acknowledge that the threat of climate change is escalating and needs to be addressed.

Scripps director Charles F. Kennel called Dr. Keeling's research "the single most important environmental data set taken in the 20th century. Dave Keeling was living proof that a scientist could, by sticking close to his bench, change the world."

Ralph Cicerone, the incoming president of the National Academy of Sciences, said in an interview that Dr. Keeling was so meticulous that he resisted efforts to connect his research with global warming until about 15 years ago, when the accumulating data convinced him that human activity was responsible for ecological changes.

"It's been virtually impossible to criticize his results because he thought of everything," Cicerone said. "His precision was so unbelievably beautiful."

"Keeling is one of the few people who's responsible for the fact that the scientific community was awakened to the need to study global warming before it's too late," said Spencer Weart, director of the Center for the History of Physics of the American Institute of Physics in College Park. "If he had not done [this research], it probably would not have been done until 20 years later."

Dr. Keeling went on to discover that the difference between the high and low amounts of carbon dioxide in the air each year has been increasing and that the average growing season in the Northern Hemisphere is as much as a week longer, perhaps as a result of global warming.

President Bush awarded him the 2001 National Medal of Science, and three months ago, Dr. Keeling received the Tyler Prize in Environmental Achievement, considered the world's top environmental award.

Dr. Keeling was born in Scranton, Pa. He graduated from the University of Illinois, and he received a doctoral degree in chemistry from Northwestern University in 1954. He was a postdoctoral fellow at the California Institute of Technology when he was recruited to work on the problem of increasing carbon dioxide in the atmosphere, which scientists were beginning to consider.

A lifelong outdoorsman, he had taken some measurements while camping at Big Sur on the central California coast, but with Scripps backing, he began a 50-year record of carbon dioxide measurements from atop a two-mile-high mountain in Hawaii and at Little America in Antarctica. His first samples showed that carbon dioxide made up of about 315 of every 1 million molecules in the air. The count is now about 380 parts per million. Tests of polar ice show that for several thousand years before the industrial era began, about 1800, atmospheric carbon dioxide accounted for between 275 and 280 parts per million.

Dr. Keeling often had to struggle for money to continue his research, and finances caused the only gap in his Hawaiian research, three months in 1964. He had to abandon his Antarctic research for years.

Weart, who published an online history of the scientific discovery of global warming (at, said Dr. Keeling made such a pest of himself in government circles that several agencies, unable to completely cut off funding, attempted to wrest control of his project. Slowly, as his data accumulated and other scientists replicated his work and began similar studies, the importance of the research became clear.

He was a member of the National Academy of Sciences and the American Academy of Arts and Sciences. He was a fellow of the American Association for the Advancement of Science and the American Geophysical Union. Dr. Keeling, an accomplished musician, nearly chose a career in music over science.

He is survived by his wife of 50 years, Louise Keeling of La Jolla, Calif., and Hamilton; five children; and six grandchildren.

Charles David Keeling's work alerted scientists to the growing risk of global warming.