Large changes in biomass burning over the last millennium inferred from paleoatmospheric ethane in polar ice cores
Large changes in biomass burning over the last millennium inferred from paleoatmospheric ethane in polar ice cores
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DOI：
10.1073/pnas.1807172115
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发表时间：
2018-11
期刊：
影响因子：
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通讯作者：
M. R. Nicewonger;M. Aydin;M. Prather;E. Saltzman
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文献类型：
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作者：
M. R. Nicewonger;M. Aydin;M. Prather;E. Saltzman
生物质燃烧通过直接排放气溶胶、温室气体和化学反应气体影响气候系统。关于过去生物质燃烧的变化存在不确定性和争议，因此很难在目前的气候模型中确定生物质燃烧的气候敏感性。这项研究提出了新的测量乙烷在空气中被困在极地冰芯。结果表明，生物质燃烧排放量在中世纪时期（1000-1500 CE）超过了现代水平，但在小冰期（1600-1800 CE）期间大幅下降，表明生物质燃烧对前工业时代气候的敏感性。生物质燃烧和气候之间的这种积极反馈可能使社会气候目标难以实现。生物质燃烧推动温室气体、气候强迫气溶胶和全球大气化学的变化。关于从工业化前到现在的千年时间尺度上生物质燃烧排放量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，存在争议。生物质燃烧是工业化前大气中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的冰芯乙烷测量结果，其中包含了自公元1000年以来生物质燃烧排放量变化的信息。在中世纪时期（公元1000-1500年），生物质燃烧产生的乙烷排放量比现在高，在较冷的小冰期（公元1600-1800年）急剧下降到最低值。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，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从冰芯甲烷稳定碳同位素比推断的一致，但与基于沉积木炭和冰芯一氧化碳测量的历史不一致。这项研究表明，生物质燃烧的排放量在过去已经超过了现代水平，可能对气候变化高度敏感。
Significance Biomass burning influences the climate system through direct emissions of aerosols, greenhouse gases, and chemically reactive gases. There is uncertainty and controversy regarding variations in past biomass burning, making it difficult to establish the climate sensitivity of biomass burning in current climate models. This study presents new measurements of ethane in air trapped in polar ice cores. The results indicate that biomass burning emissions exceeded modern levels during the Medieval Period (1000–1500 CE) but then decreased substantially during the Little Ice Age (1600–1800 CE), indicating the sensitivity of biomass burning to climate during the preindustrial era. Such positive feedbacks between biomass burning and climate may make it difficult to achieve societal climate goals. 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.