PNAS:气候变化与野火频率

摘要 : 美国怀俄明大学科研人员报告了在气候变化与野火的频率和严重程度之间的一种联系。

美国怀俄明大学科研人员报告了在气候变化与野火的频率和严重程度之间的一种联系。近几十年来，美国已经数次出现了其美国历史上规模的一些最大型的野火，但是人们仍然不清楚气候变化对野火规模和频率的影响贡献。研究过去气候变化对野火的影响可能为关于未来野火风险的预测提供约束条件。John Calder及其同事重建了过去2000年里美国科罗拉多北部的一个10万公顷区域的野火历史。这组作者根据该研究区域12个湖泊的沉积物中的木炭积累推测了过去的野火。在大约1200年前到1100年前的中世纪气候异常期(MCA)的早期，当时平均温度大约比之前的世纪高0.5摄氏度，野火频率是过去420年的260%。在中世纪气候异常期(MCA)的开始，估计每个世纪这些地点的83%被烧，相比之下在中世纪气候异常期(MCA)之前和之后的数字分别是50%和33%。然而，野火频率在温度变冷之前的很长时间就急剧下降了，这可能是由于燃料可用度的变化。这些结果提示了在一个变暖的气候与野火频率增加之间的一种联系，如果温度持续上升，野火可能变得更加频繁。

原文链接：

Medieval warming initiated exceptionally large wildfire outbreaks in the Rocky Mountains

原文摘要：

Many of the largest wildfires in US history burned in recent decades, and climate change explains much of the increase in area burned. The frequency of extreme wildfire weather will increase with continued warming, but many uncertainties still exist about future fire regimes, including how the risk of large fires will persist as vegetation changes. Past fire-climate relationshiPS provide an opportunity to constrain the related uncertainties, and reveal widespread burning across large regions of western North America during past warm intervals. Whether such episodes also burned large portions of individual landscapes has been difficult to determine, however, because uncertainties with the ages of past fires and limited spatial resolution often prohibit specific estimates of past area burned. Accounting for these challenges in a subalpine landscape in Colorado, we estimated century-scale fire synchroneity across 12 lake-sediment charcoal records spanning the past 2,000 y. The percentage of sites burned only deviated from the historic range of variability during the Medieval Climate Anomaly (MCA) between 1,200 and 850 y B.P., when temperatures were similar to recent decades. Between 1,130 and 1,030 y B.P., 83% (median estimate) of our sites burned when temperatures increased ∼0.5 °C relative to the preceding centuries. Lake-based fire rotation during the MCA decreased to an estimated 120 y, representing a 260% higher rate of burning than during the period of dendroecological sampling (360 to −60 y B.P.). Increased burning, however, did not persist throughout the MCA. Burning declined abruptly before temperatures cooled, indicating possible fuel limitations to continued burning.

doi: 10.1073/PNAS.1500796112

作者：W. John Calder

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