By Patrick Cullis, CIRES and NOAA scientist

Every year in September, as the Sun returns to the sky above the South Pole after six months of darkness, a chemical reaction happens high in our atmosphere as human activity combines with natural phenomena to destroy part of our protective ozone layer. In the last episode of this animated series, Casper and Peggy learn about the ozone hole and what scientists are doing to help it heal from the damage we did to it. Watch Part 4 to learn how the ozone hole forms above Antarctica and the measurements NOAA and CIRES scientists do to track it.

Video by Patrick Cullis/CIRES (Cooperative Institute for Research in Environmental Sciences) and the NOAA Global Monitoring Laboratory