HadCM3 Model data used in the article "Disentangling the causes of the 1816 European year without a summer" by Schurer, Andrew; Hegerl, Gabriele; Luterbacher, Juerg; Broennimann, Stefan; Cowan, Tim; Tett, Simon; Zanchettin, Davide; Timmreck, Claudia

Abstract: The European summer of 1816 has often been referred to as a “year without a summer” due to anomalously cold conditions and unusual wetness, which led to widespread famines and agricultural failures. The cause has often been assumed to be the eruption of Mount Tambora in April 1815, however this link has not, until now, been proven. Here we apply state-of-the-art event attribution methods to quantify the contribution by the eruption and random weather variability to this extreme European summer climate anomaly. By selecting analogue summers that have similar sea-level-pressure patterns to that observed in 1816 from both observations and unperturbed climate model simulations, we show that the circulation state can reproduce the precipitation anomaly without external forcing, but can explain only about a quarter of the anomalously cold conditions. We find that in climate models, including the forcing by the Tambora eruption makes the European cold anomaly up to 100 times more likely, while the precipitation anomaly became 1.5-3 times as likely, attributing a large fraction of the observed anomalies to the volcanic forcing. Our study thus demonstrates how linking regional climate anomalies to large-scale circulation is necessary to quantitatively interpret and attribute post-eruption variability. The Model data consists 50 HadCM3 Model simulations with volcanic forcing for the period 01/12/1814 to 01/12/1816. The dataset is divided into atmosphere monthly mean and ocean monthly mean files. With each containing 24 monthly values for each of the 50 simulations. The files are in the UK Metoffice pp format. This can be read using the iris python package: https://scitools.org.uk/iris/docs/latest/ Example_script.py is an example of a simple python script which reads the model data.

摘要：1816年欧洲夏季因异常寒冷和异常潮湿常被称为“无夏之年”，导致广泛饥荒与农业歉收。其原因通常被假设为1815年4月坦博拉火山爆发，但这一关联此前尚未得到证实。本文应用最先进的事件归因方法（event attribution methods），量化火山爆发与随机天气变率对该极端欧洲夏季气候异常的贡献。通过从观测数据和未受干扰的气候模型模拟（unperturbed climate model simulations）中选择与1816年观测到的类似海平面气压模式（sea-level-pressure patterns）的相似夏季，我们发现环流状态无需外部强迫（external forcing）即可重现降水异常，但仅能解释约四分之一的异常寒冷状况。我们发现，在气候模型中纳入坦博拉火山强迫（volcanic forcing）后，欧洲寒冷异常发生的可能性提升至100倍，降水异常可能性提升1.5至3倍，观测到的异常大部分可归因于火山强迫。本研究由此证明，将区域气候异常与大尺度环流相联系，对于定量解释和归因火山喷发后的气候变率至关重要。模型数据包含50组HadCM3模型模拟结果，时间范围为1814年12月1日至1816年12月1日。数据集分为大气月均值文件和海洋月均值文件，每组模拟包含24个月度值。文件采用英国气象局（UK Metoffice）的pp格式，可通过iris Python包读取：https://scitools.org.uk/iris/docs/latest/。Example_script.py是读取模型数据的简单Python脚本示例。