Methane is a powerful greenhouse gas produced both naturally and through human activities. It was first discovered by Alessandro Volta in 1776 who noticed bubbles rising from a pond and found that these bubbles could be ignited with a naked flame. Methane has a relatively short lifetime in the atmosphere, most molecules having been destroyed within 10 years of their release. However, the concentration of methane actually affects its own atmospheric lifetime. The primary mechanism for its destruction is by reaction with hydroxyl radicals (OH-), the greater the concentration of methane the more the reductive power of the atmosphere (the supply of hydroxyl radicals) is reduced. If this feedback is included, then the true atmospheric lifetime of methane extends to about 12 years.