The 2019/20 Australian black summer bushfires were particularly severe in many respects, including its early commencement, large spatial coverage, and large number of burning days, preceded by record dry and hot anomalies. Determining whether greenhouse warming has played a role is an important issue. Here, we examine known modes of tropical climate variability that contribute to droughts in Australia to provide a gauge. We find that a two-year consecutive concurrence of the 2018 and 2019 positive Indian Ocean Dipole and the 2018 and 2019 Central Pacific El Niño, with the former affecting Southeast Australia, and the latter influencing eastern and northeastern Australia, may explain many characteristics of the fires. Such consecutive events occurred only once in the observations since 1911. Using two generations of state-of-the-art climate models under historical and a business-as-usual emission scenario, we show that the frequency of such consecutive concurrences increases slightly, but rainfall anomalies during such events are stronger in the future climate, and there are drying trends across Australia. The impact of the stronger rainfall anomalies during such events under drying trends is likely to be exacerbated by greenhouse warming-induced rise in temperatures, making such events in the future even more extreme.

中文翻译：

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印度洋偶极子和中太平洋太平洋地区的厄尔尼诺现象连续两年连续发生，这为2019/2020年澳大利亚“黑色夏季”丛林大火作了前提

2019/20年度澳大利亚黑色夏季丛林大火在许多方面特别严重，包括早期爆发，大空间覆盖和大量燃烧天数，随后是创纪录的干热异常。确定温室效应是否起了重要作用。在这里，我们研究了导致澳大利亚干旱的热带气候变化的已知模式，以提供一个量表。我们发现，2018年和2019年的正印度洋偶极子以及2018年和2019年的中太平洋厄尔尼诺现象连续两年同时发生，前者影响澳大利亚东南部，而后者影响澳大利亚东部和东北部，这可能解释了该现象的许多特征。火灾。自1911年以来，这种连续事件仅在观测中发生过一次。使用历史和照常排放情景下的两代最新气候模型，我们表明，此类连续并发的频率略有增加，但此类事件期间的降雨异常在未来的气候中更为强烈，而且整个澳大利亚都有干燥趋势。在这种趋势下，干旱趋势下降雨异常现象的影响可能会因温室效应导致的温度升高而加剧，从而使未来的此类事件更加极端。