Using novel isotopic studies, scientists have identified the most important processes responsible for changes in natural methane concentrations over the transition from the last ice age into our warm period. The study shows that wetland regions emitted significantly less methane during glacial times. The glacial/interglacial changes in atmospheric methane concentrations are quite drastic. Glacial concentration were on average 350 ppbv (part per billion by volume) and increased to approximately 700 ppbv during the last glacial/interglacial transition. During the last centuries human methane emissions artificially increased methane concentrations to approximately 1750 ppbv.