CH₄, a colorless, odorless, flammable, greenhouse gas. It is the simplest of all hydrocarbons with a formula of CH₄. Methane is released naturally into the air from anaerobic environments such as marshes, swamps, and rice fields, and from symbiotic microbes in the guts of ruminant animals (such as cattle, sheep, and camels), and sewage sludge. Methane is released from methane producing bacteria (methanogens) that live in these anaerobic places. Methanogens in termite guts are the source of methane released by termites. The discovery that termites may be a significant source of atmospheric methane is attributed to work by Patrick Zimmerman and his research group members at the National Center for Atmospheric Research in Boulder Colorado (see reference immediately below and papers in the scientific literature). Ice core data from the European Project for Ice Coring in Antarctica show that present atmospheric concentrations of CO₂ and CH₄ are the highest in the past 800,000 years as determined in the so-called Dome C ice core.