This Flash-based simulation explores the relationship between carbon emissions and atmospheric carbon dioxide using two main displays: (1) graphs that show the level of human-generated CO2 emissions, CO2 removals, and the level of CO2 in the atmosphere, and (2) a bathtub animation that shows the same information as the graphs. The bathtub simulation illustrates the challenges of reducing greenhouse gas concentrations in the atmosphere.

Students consider why the observed atmospheric CO2 increase rate is only ~60% of the CO2 loading rate due to fossil fuel combustion. They develop a box-model to simulate the atmospheric CO2 increase during the industrial era and compare it to the historic observations of atmospheric CO2 concentrations. The model is then used to forecast future concentrations of atmospheric CO2 during the next century.

This set of activities is about carbon sources, sinks, and fluxes among them - both with and without anthropogenic components.