Keeling CurveThe Keeling Curve is a graph that depicts the amount of carbon dioxide in Earth’s atmosphere every day since 1958. It shows the ongoing increase in carbon dioxide in the atmosphere, alongside the seasonal variation in CO2 levels.
The curve is named after Charles David Keeling, who began the monitoring program in 1958. He was the first person to make regular measurements of carbon dioxide in Earth’s atmosphere. Keeling received the National Medal of Science for his work in 2001 and oversaw the project until his death in 2005. His son Ralph, a geochemist at UC San Diego, has taken over stewardship of the project. Daily measurements, in parts per million, are taken from the Mauna Loa Observatory by the Scripps Institution of Oceanography at UC San Diego. There have only been breaks in the daily measurements twice, in 1964 due to a funding shortage, and in 2022 due to a volcanic explosion.
The Keeling Curve is the longest uninterrupted instrumental record of atmospheric CO2 and is regarded as “the most unique and perhaps the most important dataset in earth science.” Scientists consider the Keeling Curve a foundational piece of evidence in the consensus that human activity is the main driver of climate change. The curve demonstrates that greenhouse gases are rising in the atmosphere alongside the rise in fossil fuel emissions. The data is often compared to the prehistoric carbon dioxide concentrations from air bubbles trapped in ice cores.
More than just a piece of scientific evidence, the curve is a figure in its own right. Physicist and science historian Spencer R. Weart described the graph as “the central icon of the greenhouse effect,” in his book The Discovery of Global Warming. Climate scientist and activist Michael Mann—known for his own famous “hockey stick graph”—said “the Keeling Curve is truly iconic because it tells a simple story… that human activity is having a profound impact on Earth’s environment.”
The current atmospheric carbon measurement and all previous readings can be found at https://keelingcurve.ucsd.edu.
©2026 ClimateLit (Henry Carnell)
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