News•June 12, 2015

Iconic Keeling Curve Designated a Landmark

Landmarks are generally thought of as tangible, physical things, usually involving plaques and lots of marble. But a newly named landmark recognizes something more amorphous: the steady rise of carbon dioxide in the atmosphere that envelops the planet and that is steadily heating the globe.

The American Chemical Society has named the graph that charts that rise — called the Keeling Curve, so named after the scientist who began the CO2 measurements — as a National Historic Chemical Landmark.

“The Keeling Curve is an icon of modern climate science,” Thomas J. Barton, the most recent past president of the ACS, said in a statement. The recognition that CO2 levels were building in the atmosphere thanks to human activities underpins the science of global warming.

Before Charles Keeling began his measurements atop Hawaii’s Mauna Loa volcano in 1958, accurate, continuous measurements of CO2 in the atmosphere had proved difficult to get. But Keeling’s measurements elegantly revealed both the seasonal cycle of atmospheric CO2 — driven by the collective exhale and inhale of Northern Hemisphere plants — as well as a steady year-after-year rise.

Keeling’s program continues today, run by his son, Ralph Keeling. Since the measurements began, CO2 levels have risen from about 310 parts per million to 400 ppm (preindustrial levels were about 280 ppm). That benchmark was first reached in May 2013, and each year since the 400 ppm mark has been passed earlier and earlier in the year, and CO2 levels have stayed over that mark for longer and longer. It will likely be only a couple year until CO2 levels are permanently above 400 ppm.

The amount that carbon dioxide levels have risen since the dawn of the Industrial Revolution has caused Earth’s average temperature to rise by 1.6°F since the beginning of the 20th century. That temperature rise could nearly double by the end of this century if greenhouse gas emissions aren’t curbed, according to the most recent report from the Intergovernmental Panel on Climate Change.

“The Mauna Loa CO2 record changed how we view the world,” Ralph Keeling said in a statement. “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.”

The importance of the Keeling Curve is now recognized with, yes, a plaque, placed at the site of Keeling’s lab on the San Diego campus of the Scripps Institution of Oceanography.