C-Learn is a simplified version of the C-ROADS simulator. Its primary purpose is to help users understand the long-term climate effects (CO2 concentrations, global temperature, sea level rise) of various customized actions to reduce fossil fuel CO2 emissions, reduce deforestation, and grow more trees. Students can ask multiple, customized what-if questions and understand why the system reacts as it does.

The activity follows a progression that examines the CO2 content of various gases, explores the changes in the atmospheric levels of CO2 from 1958 to 2000 from the Mauna Loa Keeling curve, and the relationship between CO2 and temperature over the past 160,000 years. This provides a foundation for examining individuals' input of CO2 to the atmosphere and how to reduce it.