Arctic amplification decreases temperature variance in northern mid- to high-latitudes
Arctic amplification decreases temperature variance in northern mid- to high-latitudes
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DOI：
10.1038/nclimate2268
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发表时间：
2014-07-01
影响因子：
30.7
通讯作者：
Screen, James A.
中科院分区：
文献类型：
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作者：
Screen, James A.
可以说，气候变率的变化比平均气候的变化对社会和生态系统更为重要，特别是当它们转化为极端变化时（1-3）。人们普遍认为，人类引起的气候变化将导致更加不稳定和极端的天气，这一点也日益引起人们的关注(4)。某些类型的极端天气的频率和/或严重程度有所增加（5-7），部分原因是平均气候的变化，但也是由于变率的变化（1-3,8-10）。尽管平均气候变暖，但在过去十年中，北半球中纬度地区表面上出现了大量高影响的极端寒冷事件（11）。一种解释是北极放大效应——北极比低纬度地区变暖更大（12），与海冰和积雪减少有关——正在改变极地急流，增加温度变化（13-16）。然而，这项研究表明，近几十年来，北半球中高纬度地区的亚季节性冷季温度变率显著降低。这在一定程度上是因为北风和与之相关的寒冷天气比南风和温暖天气变暖得更快，因此北极放大作用减少了亚季节温度变化。以前将北极放大与极端天气增加联系起来的假设引发了大气环流的动力变化（11,13-16），这些变化在目前的观测中很难探测到（17,18），在未来也高度不确定（19,20）。相比之下，亚季节冷季温度变率的减少，与本文提出的机制一致，在观测记录中可以检测到，并且在21世纪气候模式模拟中非常稳健。
Changes in climate variability are arguably more important for society and ecosystems than changes in mean climate, especially if they translate into altered extremes(1-3). There is a common perception and growing concern that human-induced climate change will lead to more volatile and extreme weather(4). Certain types of extreme weather have increased in frequency and/or severity(5-7), in part because of a shift in mean climate but also because of changing variability(1-3,8-10). In spite of mean climate warming, an ostensibly large number of high-impact cold extremes have occurred in the Northern Hemisphere mid-latitudes over the past decade(11). One explanation is that Arctic amplification-the greater warming of the Arctic compared with lower latitudes(12) associated with diminishing sea ice and snow cover-is altering the polar jet stream and increasing temperature variability(13-16). This study shows, however, that subseasonal cold-season temperature variability has significantly decreased over the mid-to high-latitude Northern Hemisphere in recent decades. This is partly because northerly winds and associated cold days are warming more rapidly than southerly winds and warm days, and so Arctic amplification acts to reduce subseasonal temperature variance. Previous hypotheses linking Arctic amplification to increased weather extremes invoke dynamical changes in atmospheric circulation(11,13-16), which are hard to detect in present observations(17,18) and highly uncertain in the future(19,20). In contrast, decreases in subseasonal cold-season temperature variability, in accordance with the mechanism proposed here, are detectable in the observational record and are highly robust in twenty-first-century climate model simulations.