Geologic carbon sequestration (GCS)—injecting carbon dioxide deep underground, beneath impermeable caprock—promises to be a powerful tool in the mitigation of climate change. Although natural accumulation of carbon dioxide underground and the oil industry’s successful engineered disposal of carbon dioxide suggest that GCS is safe, public concern continues about injected carbon dioxide causing air or groundwater contamination. This project will develop a model for analyzing, quantifying, and monitoring the risk of GCS. This methodology will inform decisions about initiating carbon sequestration projects and maintaining them safely. Making GCS more cost-effective and reliable will reduce the amount of carbon dioxide in the atmosphere, promoting a sustainable climate and cleaner environment.