The U.S. famously declined to sign the Kyoto Protocol on climate change, but yesterday it jumped on the bandwagon of another effort to control global warming: a research program dedicated to exploring technologies for capturing and storing carbon dioxide. Such technologies, collectively known as carbon sequestration, seek to keep CO2 out of the atmosphere through storage innovations, rather than through limiting emissions. At a three-day conference convened by the Bush administration in McLean, Va., the U.S. signed on to the research program along with representatives of other industrialized and developing countries, including the E.U. nations, Canada, Australia, Russia, Japan, China, and India. Environmentalists attending the conference applauded the commitment to investigating carbon sequestration but said that technological innovations must go hand-in-hand with mandatory emissions limits.