Xu Tongtong, Newman Matthew, Capotondi Antonietta, Stevenson Samantha, Di Lorenzo Emanuele, Alexander Michael A
NOAA Physical Sciences Laboratory, Boulder, CO, USA.
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA.
Nat Commun. 2022 Dec 1;13(1):7396. doi: 10.1038/s41467-022-34934-x.
Marine heatwaves (MHWs)-extremely warm, persistent sea surface temperature (SST) anomalies causing substantial ecological and economic consequences-have increased worldwide in recent decades. Concurrent increases in global temperatures suggest that climate change impacted MHW occurrences, beyond random changes arising from natural internal variability. Moreover, the long-term SST warming trend was not constant but instead had more rapid warming in recent decades. Here we show that this nonlinear trend can-on its own-appear to increase SST variance and hence MHW frequency. Using a Linear Inverse Model to separate climate change contributions to SST means and internal variability, both in observations and CMIP6 historical simulations, we find that most MHW increases resulted from regional mean climate trends that alone increased the probability of SSTs exceeding a MHW threshold. Our results suggest the need to carefully attribute global warming-induced changes in climate extremes, which may not always reflect underlying changes in variability.
海洋热浪（MHWs）——极其温暖且持续的海面温度（SST）异常，会造成重大的生态和经济后果——在近几十年里在全球范围内有所增加。全球气温的同步上升表明，气候变化影响了海洋热浪的发生，而非仅仅是自然内部变率引起的随机变化。此外，长期的海温变暖趋势并非恒定不变，而是在近几十年里升温更快。在此我们表明，这种非线性趋势自身就可能看似增加了海温变率，进而增加了海洋热浪的频率。利用线性逆模型在观测数据和CMIP6历史模拟中分离气候变化对海温均值和内部变率的贡献，我们发现，大多数海洋热浪的增加是由区域平均气候趋势导致的，这些趋势本身就增加了海温超过海洋热浪阈值的概率。我们的结果表明，有必要谨慎地归因于全球变暖引起的极端气候的变化，这些变化可能并不总是反映变率的潜在变化。
