Unexpected Changes to the Global Methane Budget over the Past 2000 Years

We report a 2000-year Antarctic ice-core record of stable carbon isotope measurements in atmospheric methane (δ13CH4). Large δ13CH4 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.), δ13CH4 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 ∼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.

[1]  K. Holmgren,et al.  Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data , 2005, Nature.

[2]  Giuseppe Etiope,et al.  New Directions: GEM—Geologic Emissions of Methane, the missing source in the atmospheric methane budget☆ , 2004 .

[3]  W. Ruddiman,et al.  The Anthropogenic Greenhouse Era Began Thousands of Years Ago , 2003 .

[4]  D. Hallett,et al.  A 1000-year record of forest fire, drought and lake-level change in southeastern British Columbia, Canada , 2003 .

[5]  K. Gajewski,et al.  Holocene biomass burning and global dynamics of the carbon cycle. , 2002, Chemosphere.

[6]  J. Lelieveld,et al.  A 1°×1° resolution data set of historical anthropogenic trace gas emissions for the period 1890–1990 , 2001 .

[7]  M. Andreae,et al.  Emission of trace gases and aerosols from biomass burning , 2001 .

[8]  W. Sturges,et al.  Changes in the global atmospheric methane budget over the last decades inferred from13C and D isotopic analysis of Antarctic firn air , 2001 .

[9]  Georg Guggenberger,et al.  The 'Terra Preta' phenomenon: a model for sustainable agriculture in the humid tropics , 2001, Naturwissenschaften.

[10]  J. Lelieveld,et al.  Simulation of preindustrial atmospheric methane to constrain the global source strength of natural wetlands , 2000 .

[11]  M. Manning,et al.  The trend in atmospheric methane δ13C and implications for isotopic constraints on the global methane budget , 2000 .

[12]  Dirk Verschuren,et al.  Rainfall and drought in equatorial east Africa during the past 1,100 years , 2000, Nature.

[13]  D. Etheridge,et al.  A history of δ13C in atmospheric CH4 from the Cape Grim Air Archive and Antarctic firn air , 1999 .

[14]  J. Jouzel,et al.  Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica , 1999, Nature.

[15]  Yuhang Wang,et al.  Anthropogenic forcing on tropospheric ozone and OH since preindustrial times , 1998 .

[16]  D. Etheridge,et al.  Atmospheric methane between 1000 A.D. and present: Evidence of anthropogenic emissions and climatic variability , 1998 .

[17]  G. Ren.  Pollen evidence for increased summer rainfall in the medieval warm period at Maili, northeast China , 1998 .

[18]  M. Legrand,et al.  High northern latitude forest fires and vegetation emissions over the last millennium inferred from the chemistry of a central Greenland ice core , 1998 .

[19]  M. Manning,et al.  The 1991–1992 atmospheric methane anomaly: Southern hemisphere 13C decrease and growth rate fluctuations , 1997 .

[20]  M. Anderson.  Prehistoric anthropogenic wildland burning by hunter-gatherer societies in the temperate regions: A net source, sink, or neutral to the global carbon budget? , 1994 .

[21]  S. Subak.  Methane from the House of Tudor and the Ming Dynasty: Anthropogenic emissions in the sixteenth century , 1994 .

[22]  D. Woodcock,et al.  The burning of the New World: the extent and significance of broadcast burning by early humans. , 1994, Chemosphere.

[23]  T. Swetnam.  Fire History and Climate Change in Giant Sequoia Groves , 1993, Science.

[24]  C. M. Stevens,et al.  The Isotopic Composition of Methane in Polar Ice Cores , 1988, Science.

[25]  M. Khalil,et al.  Atmospheric methane in the recent and ancient atmospheres Concentrations, trends, and interhemispheric gradient , 1984 .

[26]  J. Houdaille.  Native (the) population of the Americas in 1492 , 1978 .