A system for cooling an environmentally sealed enclosure. The system includes an air channel extending generally vertically from a top surface of the enclosure to a bottom surface of the enclosure, at least one interior heat sink forming a barrier between the air channel and an interior portion of the enclosure, a fan disposed in the air channel and adapted to force air to flow through the air channel, and a plenum proximate the air channel to duct exhaust air away from the enclosure, wherein air flowing through the air channel cools the enclosure. A method employs the system.