In 2012, extreme anomalous climate conditions occurred around the globe. Large areas of North America experienced an anomalously hot summer, with large precipitation deficits inducing severe drought. Over Europe, the summer of 2012 was marked by strong precipitation anomalies with the UK experiencing its wettest summer since 1912 while Spain suffered severe drought. What caused these extreme climate conditions in various regions in 2012? This study compares attribution conclusions for 2012 climate anomalies relative to a baseline period (1964–1981) based on two sets of parallel experiments with different model configurations (with coupling to an ocean mixed layer model or with prescribed sea surface temperatures) to assess whether attribution conclusions concerning the climate anomalies in 2012 are sensitive to the representation of air-sea interaction. Modelling results indicate that attribution conclusions for large scale surface air temperature (SAT) changes in both boreal winter and summer are generally robust and not very sensitive to air-sea interaction. This is especially true over southern Europe, Eurasia, North America, South America, and North Africa. Some other responses also appear to be insensitive to air-sea interaction: for example, forced increases in precipitation over northern Europe and Sahel, and reduced precipitation over North America and the Amazon in boreal summer. However, the attribution of circulation and precipitation changes for some other regions exhibits a sensitivity to air-sea interaction. Results from the experiments including coupling to an ocean mixed layer model show a positive NAO-like circulation response in the Atlantic sector in boreal winter and weak changes in the East Asian summer monsoon and precipitation over East Asia. With prescribed sea surface temperatures, some different responses arise over these two regions. Comparison with observed changes indicates that the coupled simulations generally agree better with observations, demonstrating that attribution methods based on atmospheric general circulation models have limitations and may lead to erroneous attribution conclusions for regional anomalies in circulation, precipitation and surface air temperature.

2012年，全球各地发生了极端异常的气候条件。北美大片地区夏季异常炎热，大量降水不足导致严重干旱。在欧洲，2012年夏季的降水异常强烈，英国经历了自1912年以来最潮湿的夏天，而西班牙则遭受了严重的干旱。是什么导致了2012年各个地区的极端气候条件？本研究基于两组具有不同模型配置（与海洋混合层模型耦合或具有规定海面温度的平行实验）的平行实验，比较了相对于基线期（1964-1981年）的2012年气候异常的归因结论，以评估归因是否关于2012年气候异常的结论对海-气相互作用的表示很敏感。建模结果表明，在冬季和夏季，无论是冬季还是夏季，大尺度地表温度（SAT）变化的归因结论通常都是可靠的，并且对海-气相互作用不太敏感。在南欧，欧亚大陆，北美，南美和北非，尤其如此。其他一些响应似乎也对海-气相互作用不敏感：例如，北部和萨赫勒地区的降水被迫增加，而北方和夏季亚马逊地区的亚马逊地区的降水被迫减少。然而，其他一些地区的环流和降水变化的归因表现出对海-气相互作用的敏感性。包括耦合到海洋混合层模型在内的实验结果表明，在北方冬季，大西洋地区的NAO样环流响应为正，东亚夏季风的变化较弱，东亚的降水量较小。在规定的海面温度下，在这两个区域会出现一些不同的响应。与观察到的变化进行比较表明，耦合模拟通常与观察结果更好地吻合，