The Keeling Curve is the measurement of CO2 in the Earth's atmosphere. As we burn fossil fuel or damage "Carbon sinks" we increase that number. The Keeling curve is at the root of much of the science of global warming. It goes up over time because of the release of fossil Carbon, and it wiggles up and down at shorter time scales for other reasons. For example, the curve drops during the Northern Hemisphere summer because the plants on the north side of the globe take in some of the CO2 and make it temporarily into plant tissue. During the northern winter the reverse happens. (There is a lot more land in the Northern Hemisphere).
Anyway, the Keeling Curve is now a movie! And you can watch it for free here: