In climatology, the so-called "8.2-kiloyear event" was a sudden decrease in global temperatures that occurred approximately 8,200 years before the present (BP), that is, c. 6,200 BC. It defines the start of the Northgrippian age in the Holocene epoch. Milder than the Younger Dryas cold period before it but more severe than the Little Ice Age after it, the 8.2-kiloyear cooling was a significant exception to general trends of the Holocene climatic optimum. During the event, atmospheric methane concentration decreased by 80 ppb, an emission reduction of 15%, by cooling and drying at a hemispheric scale.