This animation is based on a supercomputer climate simulation that shows two different sources of atmospheric carbon dioxide — fires (biomass burning) and massive urban centers known as megacities. Scientists are using climate models like this one — called GEOS-5 (Goddard Earth Observing Model, Version 5, created at NASA’s Goddard Space Flight Center) — to better understand how carbon dioxide moves around Earth’s atmosphere and how carbon moves through Earth’s air, land and ocean over time. Rising carbon dioxide levels in the atmosphere are driving Earth’s ongoing climate change. This animation shows a five-day period in June 2006. The model is based on real emissions inventory data and is then set to run so that scientists can observe how the greenhouse gas behaves in the atmosphere once it has been emitted.