This activity analyzes a figure showing the atmospheric carbon dioxide concentration from 1958 to 2016.

Records from polar ice cores show that the natural range of atmospheric CO₂ over the last 800,000 years was 170 to 300 parts per million (ppm) by volume. In the early 20th century, scientists began to suspect that CO₂ in the atmosphere might be increasing beyond this range due to human activities, such as burning fossil fuels and making changes in land use. At that time, however, there were no clear measurements of this trend. In 1958, Charles David Keeling began measuring atmospheric carbon dioxide at the Mauna Loa Observatory on the big island of Hawaii. This figure is a graph of the observatory’s measurements over time, which is now called the Keeling Curve.

The “Educator Materials” document includes a captioned figure, background information, graph interpretation, and discussion questions. The “Student Handout” includes a captioned figure and background information.