Large changes in biomass burning over the last millennium inferred from paleoatmospheric ethane in polar ice cores

Biomass burning drives changes in greenhouse gases, climate-forcing aerosols, and global atmospheric chemistry. There is controversy about the magnitude and timing of changes in biomass burning emissions on millennial time scales from preindustrial to present and about the relative importance of climate change and human activities as the underlying cause. Biomass burning is one of two notable sources of ethane in the preindustrial atmosphere. Here, we present ice core ethane measurements from Antarctica and Greenland that contain information about changes in biomass burning emissions levels (defined as the 1997–2016 CE period of global satellite records of biomass burning). In contrast, the CH4 stable isotope record (δ13CH4) indicates that biomass burning emissions remained near their LIA minimum until about 1850 CE, when emissions began their rise to modern levels.