Carbon dioxide gets a lot of grief these days. It's the main cause of the global warming that's already damaging coral reefs, ice caps, and coastlines. But for eons, life survived on Earth because natural processes kept CO2 levels within limits, preventing the planet from getting either too cold or too hot.

Originally released by Knowledgemotion, 2018. Streaming video file encoded with permission for digital streaming by Infobase on February 21, 2020.