The following interactive displays trends in CO₂ concentrations (averaged monthly) from 11 locations around the world (see the station globe below). Many factors influence global and local CO₂ concentrations, including the carbon cycle, the distribution of forests (especially forests near the poles that experience strong seasonality), and the mixing of air masses between and within each hemisphere. Notice how the seasonal amplitude of atmospheric CO₂ has recently increased at the high latitudes in the Northern Hemisphere.

The globe below shows the locations of the CO₂ measuring stations. Only stations that are checked on the interactive graph are shown.

This data comes from the Scripps Institute of Oceanography CO₂ Program, which was started by Charles Keeling. The first measurements began in 1957 at La Jolla, California and at the South Pole, and in 1958 at Mauna Loa Observatory in Hawaii. The Mauna Loa CO₂ record represents one of the most important scientific works of the 20th century and is known as the Keeling Curve. Mauna Loa is an ideal long-term monitoring site due to its remote location far from continents and its lack of vegetation.

The Scripts CO₂ program was expanded during the 1960's and 1970's to include an array of stations between the Arctic and Antarctica. To gain further insights, see the animation Carbon Dioxide Pumphandle 2019 by NOAA.