title: Unexpected changes to the global methane budget over the past 2000 years.
abstract: We report a 2000-year Antarctic ice-core record of stable carbon isotope measurements in atmospheric methane (delta13CH4). Large delta13CH4 variations indicate that the methane budget varied unexpectedly during the late preindustrial Holocene (circa 0 to 1700 A.D.). During the first thousand years (0 to 1000 A.D.), delta13CH4 was at least 2 per mil enriched compared to expected values, and during the following 700 years, an about 2 per mil depletion occurred. Our modeled methane source partitioning implies that biomass burning emissions were high from 0 to 1000 A.D. but reduced by almost approximately 40% over the next 700 years. We suggest that both human activities and natural climate change influenced preindustrial biomass burning emissions and that these emissions have been previously understated in late preindustrial Holocene methane budget research.
authors.affiliation: Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA. d.ferretti@niwa.co.nz
authors.forename: D F
authors.initials: DF
authors.lastname: Ferretti
authors.forename: J B
authors.initials: JB
authors.lastname: Miller
authors.forename: J W C
authors.initials: JW
authors.lastname: White
authors.forename: D M
authors.initials: DM
authors.lastname: Etheridge
authors.forename: K R
authors.initials: KR
authors.lastname: Lassey
authors.forename: D C
authors.initials: DC
authors.lastname: Lowe
authors.forename: C M
authors.initials: CM
authors.lastname: Macfarling Meure
authors.forename: M F
authors.initials: MF
authors.lastname: Dreier
authors.forename: C M
authors.initials: CM
authors.lastname: Trudinger
authors.forename: T D
authors.initials: TD
authors.lastname: van Ommen
authors.forename: R L
authors.initials: RL
authors.lastname: Langenfelds