Bryan Killett is a physicist working on the Gravity Recovery And Climate Experiment (GRACE) for NASA's Jet Propulsion Laboratory. GRACE is a joint mission of NASA and the German Aerospace Center which collects satellite data to learn about Earth's changing gravity field, specifically the high frequency changes associated with ocean tides. As the high tide comes in, more water is present, so gravity in that location is temporarily strengthened. These changes are detected with GRACE and used to improve ocean tide models. Dr. Killett provides the open source (GPLv3) code used to process GRACE data on his home page. Bryan has agreed to take a break from measuring gravity fields and answer your questions about GRACE and the climate changes it has revealed. Feel free to ask as many as you like but please confine your questions to one per post.