Lester Machta (February 17, 1919 – August 31, 2001) was an American meteorologist, the first director of the Air Resources Laboratory (ARL) of the National Oceanic and Atmospheric Administration.

[2][3] In 1948 Harry Wexler hired Machta to join the United States Weather Bureau as Chief of the Special Projects Section, which later became the Air Resources Laboratory.

Machta used the more realistic Brewer-Dobson model of atmospheric circulation, showing that radioactive fallout would reach the ground sooner and be concentrated in the populated mid-latitudes, and thus produce much greater health risks.

The GMCC program incorporated the already existing Mauna Loa and South Pole Observatories operated by Charles David Keeling, whose long-term measurements of atmospheric carbon dioxide would eventually be recognized as essential for the study of global warming[11] Machta meanwhile became an expert on stratospheric ozone, publishing numerous scientific papers on the subject while overseeing the United States network of Dobson ozone spectrophotometers.

After his official retirement as its director in 1989, Machta continued to do research at the Air Resources Laboratory until shortly before his death from leukemia on August 31, 2001, at the Georgetown University Hospital.