Global Methane Biogeochemistry

Methane is the most abundant hydrocarbon in the atmosphere. It plays important roles in atmospheric chemistry and the radiative balance of the Earth. Methane has been studied as an atmospheric constituent for over 200 years. A 1776 letter from Alessandro Volta to Father Campi described the first experiments on flammable ‘air’ released by shallow sediments in Lake Maggiore. This chapter attempts to summarize our current knowledge of the global methane budget, our understanding of physical and microbiological controls on CH 4 sources and sinks, and how well models are representing these processes.