Separating Forced from Chaotic Climate Variability over the Past Millennium
Separating Forced from Chaotic Climate Variability over the Past Millennium
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DOI：
10.1175/jcli-d-12-00826.1
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发表时间：
2013-09-01
影响因子：
4.9
通讯作者：
Phipps, Steven J.
中科院分区：
文献类型：
--
作者：
Schurer, Andrew P.;Hegerl, Gabriele C.;Phipps, Steven J.
对过去气候的重建显示，过去千年中温度变化显着，中世纪气候异常（MCA）期间相对温暖，小冰河时期（LIA）相对寒冷。过去千年的多模型模拟与北半球年平均温度的广泛重建一起使用，将公元 850 年至 1950 年的气候变化分为外部强迫和内部气候变化的组成部分。人们发现，无论代理重建如何，外部强迫都会对长期温度变化产生显着影响，特别是从 1400 年开始。然而，仅在 MCA 上，仅在所考虑的大约一半的重建中可以检测到强迫的影响，并且模型中对强迫的响应无法解释在一些重建中看到的 1000 CE 左右的温暖条件。检测分析的残差用于估计独立于气候模型的内部变异性，并且发现最近观测到的 50 年和 100 年半球温度趋势远远大于任何内部生成的趋势，即使使用 MCA 上的大残差也是如此。研究发现，太阳输出的变化和火山爆发是 1400 年至 1900 年气候变化的主要驱动因素，但首次发现温室气体变化对 1600 年至 1800 年寒冷条件的显着影响。代理重建往往显示出比模型模拟的更小的受迫响应。研究表明，这种差异至少部分可能与重建和模型模拟之间对大型火山喷发的响应差异有关。
Reconstructions of past climate show notable temperature variability over the past millennium, with relatively warm conditions during the Medieval Climate Anomaly (MCA) and a relatively cold Little Ice Age (LIA). Multimodel simulations of the past millennium are used together with a wide range of reconstructions of Northern Hemispheric mean annual temperature to separate climate variability from 850 to 1950 CE into components attributable to external forcing and internal climate variability. External forcing is found to contribute significantly to long-term temperature variations irrespective of the proxy reconstruction, particularly from 1400 onward. Over the MCA alone, however, the effect of forcing is only detectable in about half of the reconstructions considered, and the response to forcing in the models cannot explain the warm conditions around 1000 CE seen in some reconstructions. The residual from the detection analysis is used to estimate internal variability independent from climate modeling, and it is found that the recent observed 50- and 100-yr hemispheric temperature trends are substantially larger than any of the internally generated trends even using the large residuals over the MCA. Variations in solar output and explosive volcanism are found to be the main drivers of climate change from 1400 to 1900, but for the first time a significant contribution from greenhouse gas variations to the cold conditions during 1600-1800 is also detected. The proxy reconstructions tend to show a smaller forced response than is simulated by the models. This discrepancy is shown, at least partly, to be likely associated with the difference in the response to large volcanic eruptions between reconstructions and model simulations.