学术中气爱：PNAS最新！我国的减排加剧了太平洋另一边的一系列极端热浪_风闻

自2010年以来，东北太平洋发生了多次破纪录的极端暖海表面温度（SST）事件（也称暖斑或海洋热浪）。研究表明，东北太平洋SST在过去100余年间并未对温室气体强迫导致的全球变暖有显著响应。但是自2010年代以后，东北太平洋SST增暖呈现出显著加速的趋势，并带来了多次极端暖异常事件。现在，研究者们指出了这一现象一个令人惊讶的原因：中国在遏制空气污染方面的成功。中国海洋大学王海副教授等人近日发表在《美国国家科学院院刊》（PNAS）上的研究文章指出：2010年至今中国工厂和发电厂排放的气溶胶（硫酸盐等微小空气颗粒）急剧下降，似乎加剧了太平洋另一边的一系列极端热浪，推动了这些热浪期间温度上升的30%。

中国迅速下降的气溶胶排放量明显可见

从2013年底少数破纪录的热浪中的第一次袭击了阿拉斯加附近的北太平洋开始，这些温暖的“斑点”在过去十年中发生了四次，有时会比正常水平高出2°C以上。它们引发了整个海岸的有毒藻类大量繁殖，导致数千头座头鲸失踪死亡，清空阿拉斯加鳕鱼渔民的渔网，并在北美海滩上留下饥饿的海鸟尸体。

气溶胶可以像小镜子一样，将阳光反射回太空并减少到达地球表面的数量。上个月的一篇文章指出（链接附后补充），在2001年至2019年期间，更清洁的空气可能是导致全球变暖的热量增加的40%的原因。在2006年至2017年期间，中国二氧化硫的排放量减少了70%，而二氧化硫在大气中反应形成的硫酸盐颗粒就是气溶胶的成因之一。研究人员使用了十几个计算机模型，以了解这两个现象是否可能相互关联。计算机模拟显示，人为气溶胶排放变化则在2010年前后分别减缓和加剧了增暖的幅度。这说明与温室气体强迫的长期增暖效应不同，人为气溶胶强迫对海洋增暖速率的影响主要反映在年代际的调整上。

明显变暖的东北太平洋

因此，要减缓海洋长期增暖及其带来的灾害，温室气体的减排是“治本”之法，而人为气溶胶排放的变化则是精准预估和应对要考虑的重要因素之一。本研究揭示了人为气溶胶排放变化的大尺度气候效应，为理解人类活动影响海洋提供了新的视角，同时也为未来气候变化预估提供了重要理论依据。

论文信息：

Hai Wang, Xiao-Tong Zheng, Wenju Cai, Zi-Wen Han, Shang-Ping Xie, Sarah M. Kang, Yu-Fan Geng, Fukai Liu, Chuan-Yang Wang, Yue Wu, Baoqiang Xiang, Lei Zhou. (2024). Atmosphere teleconnections from abatement of China aerosol emissions exacerbate Northeast Pacific warm blob events. Proceedings of the National Academy of Sciences of the United States of America, 121 (21): e2313797121.

Atmosphere teleconnections from abatement of China aerosol emissions exacerbate Northeast Pacific warm blob events

Hai Wang , Xiao-Tong Zheng  [email protected], Wenju Cai, , and Lei Zhou

Significance

The period of 2010 to 2020 has witnessed the warmest Northeast Pacific (NEP) sea surface temperatures ever recorded, with several prolonged extreme ocean warming events. Though year-to-year internal climate variability may partially explain the appearance of these events, why they occurred dramatically more frequent remains elusive. We find that the rapid aerosol abatement in China triggers atmospheric circulation anomalies beyond its source region, driving a substantial mean surface warming in the NEP, which provides a favorable condition for extreme ocean warming events. Our findings provide an important insight into the mechanisms of the North Pacific ocean-atmosphere changes, highlighting the need to consider the exacerbated risks arising from a reduction in anthropogenic aerosol emissions in assessment of climate change impacts.

Abstract

During 2010 to 2020, Northeast Pacific (NEP) sea surface temperature (SST) experienced the warmest decade ever recorded, manifested in several extreme marine heatwaves, referred to as “warm blob” events, which severely affect marine ecosystems and extreme weather along the west coast of North America. While year-to-year internal climate variability has been suggested as a cause of individual events, the causes of the continuous dramatic NEP SST warming remain elusive. Here, we show that other than the greenhouse gas (GHG) forcing, rapid aerosol abatement in China over the period likely plays an important role. Anomalous tropospheric warming induced by declining aerosols in China generated atmospheric teleconnections from East Asia to the NEP, featuring an intensified and southward-shifted Aleutian Low. The associated atmospheric circulation anomaly weakens the climatological westerlies in the NEP and warms the SST there by suppressing the evaporative cooling. The aerosol-induced mean warming of the NEP SST, along with internal climate variability and the GHG-induced warming, made the warm blob events more frequent and intense during 2010 to 2020. As anthropogenic aerosol emissions continue to decrease, there is likely to be an increase in NEP warm blob events, disproportionately large beyond the direct radiative effects.