Attribution of the Australian bushfire risk to anthropogenic climate change
Attribution of the Australian bushfire risk to anthropogenic climate change
复制标题
DOI：
10.5194/nhess-2020-69
复制
发表时间：
2020-03
影响因子：
4.6
通讯作者：
G. J. van Oldenborgh;F. Krikken;S. Lewis;N. Leach;F. Lehner;K. Saunders;M. van Weele;K. Haustein;Sihan Li;D. Wallom;S. Sparrow;J. Arrighi;Roop Singh;M. V. van Aalst;S. Philip;R. Vautard;F. Otto
中科院分区：
文献类型：
--
作者：
G. J. van Oldenborgh;F. Krikken;S. Lewis;N. Leach;F. Lehner;K. Saunders;M. van Weele;K. Haustein;Sihan Li;D. Wallom;S. Sparrow;J. Arrighi;Roop Singh;M. V. van Aalst;S. Philip;R. Vautard;F. Otto
抽象的。2019年最后几个月和2020年1月发生的灾难性森林火灾影响了澳大利亚，这引发了人为气候变化在多大程度上加剧了这些火灾的风险的问题。为了回答澳大利亚东南部的这个问题，那里的火灾特别严重，影响到了人类和生态系统，我们使用了一个基于物理的火灾天气指数，即火灾天气指数；对高温和干旱的长期观测；以及11个最先进的大型气候模型组合。我们发现，自1979年以来，第五代欧洲中期天气预报中心(ECMWF)大气再分析(ERA5)的火灾天气指数出现了较大的趋势，模式中的火灾天气指数至少有30%的较小但显著的增长。因此，我们发现，气候变化导致了这样一个极端火灾季节的天气诱导风险更高。这一趋势主要是由极端气温的增加推动的。与之前的分析一致，我们发现，由于长期变暖的趋势，极端高温的可能性至少增加了2倍。然而，目前的气候模型高估了可变性，往往低估了这些极端情况的长期趋势，因此极端高温发生的可能性的真实变化可能更大，这表明火灾天气风险增加的原因是保守的估计。我们既没有发现极端的年度干旱，也没有发现火灾季节最干燥的月份，即9-2月。然而，观测结果显示，年平均有微弱的干燥趋势。在2019/20季节，7月至12月干旱的一半以上是由印度洋偶极子和南环空模式创纪录的偏移造成的，这些因素在这里的分析中包括在内。这项研究揭示了2019/20年森林大火事件的复杂性，一些(但不是所有)驱动因素显示出人为气候变化的印记。最后，研究报告对各种脆弱性和暴露因素进行了定性审查，每个因素都发挥了作用，以及增加或减少丛林大火总体影响的危险。
Abstract. Disastrous bushfires during the last months of 2019 and January 2020 affected Australia, raising the question to what extent the risk of these fires was exacerbated by anthropogenic climate change. To answer the question for southeastern Australia, where fires were particularly severe, affecting people and ecosystems, we use a physically based index of fire weather, the Fire Weather Index; long-term observations of heat and drought; and 11 large ensembles of state-of-the-art climate models. We find large trends in the Fire Weather Index in the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) Atmospheric Reanalysis (ERA5) since 1979 and a smaller but significant increase by at least 30 % in the models. Therefore, we find that climate change has induced a higher weather-induced risk of such an extreme fire season. This trend is mainly driven by the increase of temperature extremes. In agreement with previous analyses we find that heat extremes have become more likely by at least a factor of 2 due to the long-term warming trend. However, current climate models overestimate variability and tend to underestimate the long-term trend in these extremes, so the true change in the likelihood of extreme heat could be larger, suggesting that the attribution of the increased fire weather risk is a conservative estimate. We do not find an attributable trend in either extreme annual drought or the driest month of the fire season, September–February. The observations, however, show a weak drying trend in the annual mean. For the 2019/20 season more than half of the July–December drought was driven by record excursions of the Indian Ocean Dipole and Southern Annular Mode, factors which are included in the analysis here. The study reveals the complexity of the 2019/20 bushfire event, with some but not all drivers showing an imprint of anthropogenic climate change. Finally, the study concludes with a qualitative review of various vulnerability and exposure factors that each play a role, along with the hazard in increasing or decreasing the overall impact of the bushfires.