Qualla: Keeling Curve

Keeling Curve: Introduction

Thu, 12 Mar 2026 00:00:00 GMT

It is probably the most important graph in the history of climate science, and it began with a man who was obsessive about accuracy. In March 1958, Charles David Keeling set up an infrared gas analyzer at Mauna Loa Observatory in Hawaii and began measuring the concentration of carbon dioxide in the atmosphere with a precision that no one had previously attempted. Within two years, his data showed two things: the atmosphere breathed with the seasons, and it was accumulating CO2 year after year. That upward-sloping, sawtooth line became known as the Keeling Curve, and it has not stopped rising in more than six decades of continuous measurement.

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Keeling Curve: Before the Curve

Thu, 12 Mar 2026 00:00:00 GMT

The idea that carbon dioxide levels in the atmosphere might be changing was not new when Keeling arrived on Mauna Loa. In 1938, the British engineer and amateur meteorologist Guy Stewart Callendar compared CO2 measurements taken at Kew between 1898 and 1901, which averaged 274 pa...

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Keeling Curve: The Perfectionist on the Volcano

Thu, 12 Mar 2026 00:00:00 GMT

Keeling, a researcher at the Scripps Institution of Oceanography at UC San Diego, had spent years perfecting his measurement techniques at sites ranging from Big Sur near Monterey to the rain forests of Washington's Olympic Peninsula and high mountain forests in Arizona. He under...

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Keeling Curve: The Shape of a Warning

Thu, 12 Mar 2026 00:00:00 GMT

The Keeling Curve reveals two stories at once. The first is seasonal: CO2 concentrations drop by about six parts per million from May to September as Northern Hemisphere vegetation absorbs carbon through photosynthesis during spring and summer, then rise again through fall and wi...

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Keeling Curve: Four Hundred Parts Per Million

Thu, 12 Mar 2026 00:00:00 GMT

On May 9, 2013, the daily mean CO2 concentration at Mauna Loa crossed 400 parts per million for the first time in the history of the measurement program. Paleoclimate estimates suggest that CO2 had not reached this level since the mid-Pliocene epoch, two to four million years ago...

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Keeling Curve: A Father's Work, a Son's Inheritance

Thu, 12 Mar 2026 00:00:00 GMT

Keeling supervised the Mauna Loa measurements until his death in 2005, fighting throughout his career for the funding to maintain what he knew was an irreplaceable record. Gaps in the data would have been permanent, and the curve's power lies precisely in its continuity: nearly s...

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