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 since 1000 CE (Common Era). The biomass burning emissions of ethane during the Medieval Period (1000–1500 CE) were higher than present day and declined sharply to a minimum during the cooler Little Ice Age (1600–1800 CE). Assuming that preindustrial atmospheric reactivity and transport were the same as in the modern atmosphere, we estimate that biomass burning emissions decreased by 30 to 45% from the Medieval Period to the Little Ice Age. The timing and magnitude of this decline in biomass burning emissions is consistent with that inferred from ice core methane stable carbon isotope ratios but inconsistent with histories based on sedimentary charcoal and ice core carbon monoxide measurements. This study demonstrates that biomass burning emissions have exceeded modern levels in the past and may be highly sensitive to changes in climate.

生物质燃烧推动温室气体，强迫气候的气溶胶和全球大气化学的变化。从工业化前到现在的千禧年时间尺度上，生物质燃烧排放物变化的幅度和时间，以及气候变化和人类活动作为根本原因的相对重要性，都存在争议。在工业化前的大气中，生物质燃烧是乙烷的两个重要来源之一。在这里，我们介绍了南极洲和格陵兰岛冰芯乙烷的测量值，其中包含有关自公元1000年以来（公共时代）生物质燃烧排放量变化的信息。在中世纪时期（公元1000-1500年），乙烷的生物质燃烧排放量比今天高，在凉爽的小冰河时期（公元1600-1800年）急剧下降到最低。假设工业化前的大气反应性和运输与现代大气中的相同，我们估计从中世纪到小冰期的生物质燃烧排放量减少了30％至45％。生物质燃烧排放量下降的时间和幅度与根据冰芯甲烷稳定碳同位素比推断的时间和幅度一致，但与基于沉积木炭和冰芯一氧化碳测量的历史数据不一致。这项研究表明，过去生物质燃烧的排放量已超过现代水平，并且可能对气候变化高度敏感。生物质燃烧排放量下降的时间和幅度与根据冰芯甲烷稳定碳同位素比推断的时间和幅度一致，但与基于沉积木炭和冰芯一氧化碳测量的历史数据不一致。这项研究表明，过去生物质燃烧的排放量已超过现代水平，并且可能对气候变化高度敏感。生物质燃烧排放量下降的时间和幅度与根据冰芯甲烷稳定碳同位素比推断的时间和幅度一致，但与基于沉积木炭和冰芯一氧化碳测量的历史数据不一致。这项研究表明，过去生物质燃烧的排放量已经超过了现代水平，并且可能对气候变化高度敏感。