European summer temperatures since Roman times
European summer temperatures since Roman times
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DOI：
10.1088/1748-9326/11/2/024001
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发表时间：
2016-02-01
影响因子：
6.7
通讯作者：
Zerefos, C.
中科院分区：
文献类型：
--
作者：
Luterbacher, J.;Werner, J. P.;Zerefos, C.
在评估当今气候异常、将其归因于潜在强迫并从长期角度说明其频率和严重性时，空间背景至关重要。最近的国际倡议扩大了高质量代理记录的数量，并开发了新的统计重建方法。这些进展使更严格的区域过去的温度重建，反过来，评估气候模型的政策相关的，时空尺度的可能性。在这里，我们提供了一个新的代理为基础的，每年解决的，空间重建欧洲夏季（6月至8月）温度场回到755 CE的基础上贝叶斯分层模型（BHM），连同估计欧洲平均温度变化自公元前138年以来的基础上BHM和复合加缩放（CPS）。我们的重建比较独立的仪器和代理人为基础的温度估计，但建议在夏季温度变化的幅度比以前报道的更大。CPS和BHM的重建都表明，世纪欧洲夏季的平均温度与前几个世纪（包括公元1世纪、2世纪、8世纪和10世纪）没有显著差异。第一个世纪（在BHM也是第十个世纪）甚至可能比第二十个世纪稍微温暖，但差异在统计上并不显著。每50年与1951年至2000年期间的比较揭示了类似的模式。然而，最近的夏天在过去两千年的背景下异常温暖，并且在两次重建中都没有超过过去30年（1986-2015 CE）欧洲夏季平均温度的30年期。与气候模式模拟的合奏比较表明，重建的欧洲夏季温度变率在850-2000 CE期间反映了内部变率和外部强迫的变化在多个年代际时间尺度上。对于泛欧温度，我们发现重建和模型模拟与高端估计的太阳总辐照度之间的协议稍好。中世纪时期，近代和小冰期之间的温度差异在重建中比模拟大。这可能表明膨胀的变化的重建，缺乏敏感性和过程的变化，外部强迫模拟欧洲气候和/或低估的百年和更长的时间尺度上的内部变化。
The spatial context is criticalwhen assessing present-day climate anomalies, attributing them to potential forcings and making statements regarding their frequency and severity in a long-term perspective. Recent international initiatives have expanded the number of high-quality proxy-records and developed new statistical reconstruction methods. These advances allow more rigorous regional past temperature reconstructions and, in turn, the possibility of evaluating climate models on policy-relevant, spatiotemporal scales. Here we provide a new proxy-based, annually-resolved, spatial reconstruction of the European summer (June-August) temperature fields back to 755 CE based on Bayesian hierarchical modelling (BHM), together with estimates of the European mean temperature variation since 138 BCE based on BHM and composite-plus-scaling (CPS). Our reconstructions compare well with independent instrumental and proxy-based temperature estimates, but suggest a larger amplitude in summer temperature variability than previously reported. Both CPS and BHM reconstructions indicate that the mean 20th century European summer temperature was not significantly different from some earlier centuries, including the 1st, 2nd, 8th and 10th centuries CE. The 1st century (in BHM also the 10th century) may even have been slightly warmer than the 20th century, but the difference is not statistically significant. Comparing each 50 yr period with the 1951-2000 period reveals a similar pattern. Recent summers, however, have been unusually warm in the context of the last two millennia and there are no 30 yr periods in either reconstruction that exceed the mean average European summer temperature of the last 3 decades (1986-2015 CE). A comparison with an ensemble of climate model simulations suggests that the reconstructed European summer temperature variability over the period 850-2000 CE reflects changes in both internal variability and external forcing on multi-decadal time-scales. For pan-European temperatures we find slightly better agreement between the reconstruction and the model simulations with high-end estimates for total solar irradiance. Temperature differences between the medieval period, the recent period and the Little Ice Age are larger in the reconstructions than the simulations. This may indicate inflated variability of the reconstructions, a lack of sensitivity and processes to changes in external forcing on the simulated European climate and/or an underestimation of internal variability on centennial and longer time scales.