Abstract. The climate in the Northern Hemisphere (NH) of the mid-6th century was one of the coldest during the last two millennia. The onset of this cold period is attributed to the volcanic double eruption event in 536 and 540 Common Era (CE) based on multiple paleo-proxies. Recently, there has been a debate about how long lasting and cold this volcanic induced cold period actually was. To better understand this, we analyze new transient simulations over the Common Era and enhance the representation of mid 6th to 7th century climate by additional ensemble simulations covering 520–680 CE. We use the Max Planck Institute Earth System Model and apply external forcing as recommended in the Paleo Model Intercomparison Project, Phase 4. After the four large eruptions in 536, 540, 574, and 626 CE, a significant surface climate response up to 20 years is simulated. The Northern Hemisphere 2 m air temperature, and precipitation decreases up to 2 K, and 0.2 mm day⁻¹, respectively, and sea ice area increases up to 1.5 x 10¹² m². The global ocean heat content decreases drastically by 1.5 x 10²³ Jm⁻¹, which is significant for 30–40 years, and does not totally recover during the entire study period. The surface maps reveal atmospheric circulation changes with a hemispheric dipole pattern and land see contrast in the first two years after the eruptions. Poleward of ∼ 45° N higher sea level pressure and a decrease in hydrological variables occur, accompanied by a land see contrast, with decreased values over land and an increase in values over the ocean, which is especially pronounced for evaporation during boreal summer. During boreal winter, a positive North Atlantic Oscillation develops in the first year after (three out of the four) large eruptions. Analysing underlying mechanisms in the North Atlantic reveals that complex interaction between sea-ice expansion, changes in barotropic streamfunction and meridional overturning circulation leads to a reduction in the ocean heat transport, which then further enhances sea ice expansion impacting NH surface climate up to 20 years. Temperature records reconstructed from tree-rings in the NH agree well with the model simulations and show a similar ∼20 year cooling after the eruptions. A century of surface cooling starting in the mid-6th century, as shown from local tree-ring records from the Alps and Altai, does not occur in our volcanic climate model simulations, nor in the NH tree-ring compilation.

中文翻译：

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6至7世纪中叶，是否有火山在北半球引起了持久的降温？

摘要。6世纪中叶，北半球（NH）的气候是最近两千年来最冷的气候之一。此寒冷时期的开始归因于536和540 Common Era（CE）基于多个古代理的火山双喷发事件。最近，关于这个火山诱发的寒冷时期实际上持续多长时间和寒冷的争论一直存在。为了更好地理解这一点，我们分析了普通时代的新瞬态模拟，并通过覆盖520-680 CE的其他整体模拟来增强6至7世纪中期气候的表示。我们使用Max Planck Institute地球系统模型，并按照古模型比对项目第4阶段的建议应用外部强迫。在536、540、574和626 CE发生了四次大喷发之后，模拟了长达20年的显着地表气候响应。北半球的气温为2 m，降水量减少至2 K，每天减少0.2 mm^-1分别增加，海冰面积增加到1.5 x 10 ¹²  m ²。全球海洋热含量急剧下降1.5 x 10 ²³  Jm ^-1，有效期为30-40年，并且在整个研究期间并未完全恢复。地表图显示，大气环流以半球形偶极子模式变化，喷发后的头两年土地形成对比。海拔升高约45°N，并出现水文变量降低，同时出现陆地对比，陆地上的值下降，海洋上的值增加，这在北方夏季尤为明显。在寒冷的冬季，大爆发（四分之三）后的第一年，北大西洋涛动就出现了。对北大西洋的潜在机制进行分析后发现，海冰膨胀之间的复杂相互作用 正压流功能的变化和子午倾覆环流的变化导致海洋热传递的减少，进而进一步增强了海冰的膨胀，影响了长达20年的NH表面气候。从新罕布什尔州的树木年轮重建的温度记录与模型模拟非常吻合，并显示出喷发后约20年的降温。从阿尔卑斯山和阿尔泰当地的树年轮记录可以看出，从6世纪中叶开始的一个世纪的地表冷却在我们的火山气候模型模拟或NH树年轮编制中都没有发生。从新罕布什尔州的树木年轮重建的温度记录与模型模拟非常吻合，并显示出喷发后约20年的降温。从阿尔卑斯山和阿尔泰当地的树年轮记录可以看出，从6世纪中叶开始的一个世纪的地表冷却在我们的火山气候模型模拟或NH树年轮编制中都没有发生。从新罕布什尔州的树木年轮重建的温度记录与模型模拟非常吻合，并显示出喷发后约有20年的降温。从阿尔卑斯山和阿尔泰当地的树年轮记录可以看出，从6世纪中叶开始的一个世纪的地表冷却在我们的火山气候模型模拟或NH树年轮编制中都没有发生。