The source of what seems to be an anomalous increase in atmospheric methane concentrations about 5,000 years ago compared to methane levels during previous interglacial periods has puzzled researchers. Possible explanations for the rise in methane levels include very early agricultural activity. Climate and wetland simulations of global methane levels over the last glacial cycle now suggest that the increase in methane concentrations can be explained by natural changes in the Earth's orbital configuration, with enhanced emissions in the Southern Hemisphere tropics linked to precession-induced modification of seasonal precipitation
- Joy S. Singarayer
- Paul J. Valdes
- David J. Beerling