Description

The Keeling Curve is a graph of the annual variation and overall accumulation of carbon dioxide in the Earth's atmosphere based on continuous measurements taken at the Mauna Loa Observatory on the island of Hawaii from 1958 to the present day. The Mauna Loa Observatory was chosen because of its remote location in the middle of the Pacific Ocean far from major pollution sources. Its elevation at over 11,000 feet (3400 meters) also results in a more representative carbon dioxide reading for the whole atmosphere as opposed to lower levels directly affected by carbon dioxide input. 

The seasonal variations that result in the “sawtooth” graph appearance are due to seasonal vegetation cycles. Atmospheric carbon dioxide levels go down throughout the late spring and summer as plant leaves emerge ingesting and storing the atmospheric carbon. As leaves fall off in the fall and winter, the decomposing leaves release the carbon back into the atmosphere.

The curve is named after Dr Charles David Keeling who started the observations in 1958.

Atmospheric carbon dioxide concentrations at since 1958 [Source: wikicommons, Authors: Dr Peiter Tans and Dr Ralph Keeling, January 2019]

Significance of the Keeling curve

Keelings measurements showed the first significant evidence of rapidly increasing carbon dioxide levels in the atmosphere.