A $23 million project that introduced energy-efficient lightbulbs to two Mexican cities has become the first to be verified as actually reducing greenhouse-gas emissions. The pilot project took place under U.N. guidelines and Trygve Larsen of Det Norske Veritas, the Norway-based international verification foundation that certified the effort, said it can serve as a model to help formalize the system of international emissions credit trading called for under the Kyoto Protocol. The World Bank planned and supervised the project, which helped cut the equivalent of 171,168 tons of carbon dioxide from 1995 to 1998.