Hear the details of one approach under consideration as a potential solution to the growing concerns regarding greenhouse gases during the farewell presentation of the 2008 NGWREF Darcy Lecture. Anthropogenic emissions of carbon dioxide have increased atmospheric concentration of carbon dioxide by about 35 percent during the past 200 years. The current concentration, at about 385 ppm, represents the highest carbon dioxide concentration in the last 500,000 years. Projected future emissions will lead to doubling of preindustrial carbon dioxide concentration within the next 50 years. Carbon capture and storage, or CCS, is one option that could reduce or reverse this trend. The "geological storage" version of CCS involves capture of carbon dioxide before emission into the atmosphere and subsequent injection of the carbon dioxide into deep geological formations. Injection of carbon dioxide into deep formations leads to a multiphase flow problem that may involve important mass exchange between phases, nonisothermal effects, and complex geochemical reactions.