(although most CFCs/HCFCs are also potent greenhouse gases on a molecule-for-molecule basis). These species are measured at a number of global monitoring stations, which operate under the authority of international programs such as the Advanced Global Atmospheric Watch program, and various other national programs. A number of manned/semiautonomous stations make measurements of these gases in situ, and flask samples are also collected at other stations and returned to base laboratories for periodic analysis – an approach only possible for the nonreactive, long-lived species under consideration.