[1] This study presents a new hypothesis to explain the observed variation of CH4 and dC-CH4 over the last millennium. It was originally proposed that the observed minimum of dC-CH4 prior to the start of industrialization is caused by a large shift in biomass burning emissions between 1400 and 1700 A.D. According to our new hypothesis, however, the dC-CH4 minimum is the first sign of the global...
