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American Chemical Society honors measurement set at NOAA observatory
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American Chemical Society honors measurement set at NOAA observatory

Atmospheric CO2 record at Mauna Loa named National Historic Chemical Landmark

The American Chemical Society will designate the Keeling Curve – a long-term record of rising carbon dioxide in the planet’s atmosphere -- as a National Historic Chemical Landmark in a ceremony April 30 at NOAA’s Mauna Loa Observatory in Hawaii.

In March 1958, on a remote mountain slope at a newly established U.S. Weather Bureau observatory, the late geochemist Charles David Keeling of Scripps Institution of Oceanography, UC San Diego, began taking measurements of carbon dioxide in the atmosphere. In the years that followed, the systematic measurements Keeling started have become the most widely recognized record of mankind’s impact on the Earth, linking rising levels of carbon dioxide from man’s burning of fossil fuels to the warming of the planet. He passed away in 2005.

“The Keeling Curve is an icon of modern climate science,” said Thomas J. Barton, Ph.D., immediate past president of the American Chemical Society. “Dave Keeling’s meticulous research provided scientifically credible evidence that has proved critical to understanding and addressing human impacts on our environment. Keeling recognized in 1960 that fossil fuels are driving global atmospheric change, which presents serious challenges for Earth and its people. The global impacts of climate change are what make Keeling’s work so important, and so celebrated, today.”

Keeling had been seeking key locations to continuously measure carbon dioxide in the atmosphere with a new analytical tool called an infrared gas analyzer. Harry Wexler, director of research at the U.S. Weather Bureau, the predecessor to NOAA’s National Weather Service, suggested he conduct tests at the bureau’s Mauna Loa observatory.

"The Mauna Loa CO2 record changed how we view the world. It proved for the first time that humans were altering the composition of air globally, and it thereby legitimized the concern over human-caused climate change." — Ralph Keeling, Scripps scientist and son of Charles Keeling

Set up in 1956, the Mauna Loa observatory offers a unique location 11,135 feet above sea level and far from most human influences to monitor sunlight and air. The NOAA observatory continues today as a cornerstone of NOAA’s Global Greenhouse Gas Reference Network, measuring a range of greenhouse gases, ozone depleting gases, air pollutants and the sun’s radiation. NOAA scientists take continuous measurements from Mauna Loa and more than 70 sites around the world. These high-quality data provide vital environmental intelligence for understanding global weather and climate.

The work of Charles David Keeling and the partnership that he formed with NOAA continues today.Keeling’s son Ralph Keeling now leads the Scripps CO2 Group. The Mauna Loa site is among 10 locations from the South Pole to Alaska at which air samples are regularly collected in flasks for analysis for the Scripps CO2 Group.

A second ceremony on June 12 to unveil a plaque marking the National Historic Chemical Landmark designation will take place at Ritter Hall on the Scripps campus, the site of Keeling’s lab where the current Scripps CO2 Group operations continue today.

"This plaque is a great tribute to all the people who worked tirelessly over the years to sustain these detailed measurements,” said Ralph Keeling. "The Mauna Loa CO2 record changed how we view the world. It proved for the first time that humans were altering the composition of air globally, and it thereby legitimized the concern over human-caused climate change."

“From our early days as Survey of the Coast and the U.S. Weather Bureau, NOAA has used a network of observational tools to keep a finger on the pulse of our changing planet,” said Richard W. Spinrad, NOAA’s chief scientist. “Charles David Keeling’s visionary research has been an instrumental tool in our ability to monitor, observe, and record the rise of carbon dioxide in our planet’s atmosphere and the implications that has on the Earth’s overall health.”

At the April 30 ceremony, NOAA will also honor the five U.S. Weather Bureau and NOAA scientists who carried out the day-to-day continuous measurements of carbon dioxide on Mauna Loa from 1958 to the present.

The first monthly average carbon dioxide reading at Mauna Loa was 315.7 parts per million (ppm) in March 1958. Evidence later obtained from polar ice showed prehistoric concentrations from 180 ppm to 280 ppm. Concentrations have continued to rise. In March 2015, the latest full month measured, the monthly average was 401.5 ppm.

The American Chemical Society established the National Historic Chemical Landmarks program in 1992 to recognize seminal events in the history of chemistry and to increase awareness of the contributions of chemistry to the well-being of society. Other subjects recognized through this program have included the development of synthetic plastics, the discovery of penicillin, and the work of notable figures such as Rachel Carson, Joseph Priestley and George Washington Carver. For more information about the program, visit

The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 158,000 members, ACS is the world’s largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.

NOAA’s mission is to understand and predict changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Join us on Twitter, Facebook, Instagram, and our other social media channels.

For more information, please contact Monica Allen, director of public affairs for NOAA Research, at 301-734-1123 or by email at

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