In March of 1958, Dr. Charles David Keeling begins regularly measuring the amount of carbon dioxide in the atmosphere from the Mauna Loa Observatory in Hawai'i. Over the ensuing years, his research will reveal what is now known as the Keeling Curve: a graph of continuously-taken measurements showing the rapid accumulation of carbon dioxide.

Previously, scientists had not regularly measured the amount of carbon dioxide in Earth's atmosphere. As part of the International Geophysical Year, an international scientific project that took place between 1957 and 1958, Keeling received funding to conduct monitoring at Mauna Loa and at the South Pole. Some colleagues questioned why sustained monitoring was necessary, but Keeling was steadfast in his desire to take detailed and continuous measurements. Though budget cuts forced him to abandon the South Pole monitoring in the 1960s, the Mauna Loa testing continues to this day.

On a micro level, the curve zig-zags due to the imbalance in the amount of vegetation in the Northern and Southern Hemispheres - there is more land in the Northern Hemisphere and therefore more plants to "breathe out" oxygen in the Northern summer, lowering CO2 levels, which rise again in the Northern winter. Over many years, however, a stark and undeniable picture has emerged. Keeling's data points form a curve that is steadily increasing, incontrovertible evidence that the amount of CO2 in the atmosphere is rising over time. As other scientists began to study atmospheric carbon dioxide, a greenhouse gas, a consensus emerged that levels were rising to problematic levels. The recognition of this fact, made possible by Keeling, was one of the earliest and most important steps in mankind's awakening to the reality of climate change.