Climate and carbon-cycle variability over the last millennium
Climate and carbon-cycle variability over the last millennium
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DOI：
10.5194/cp-6-723-2010
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发表时间：
2010-01-01
影响因子：
4.3
通讯作者：
Marotzke, J.
中科院分区：
文献类型：
--
作者：
Jungclaus, J. H.;Lorenz, S. J.;Marotzke, J.
气候研究的一项长期任务是区分人为气候变化和自然气候变率。完成这一任务的一个先决条件是了解气候和碳循环的外部驱动因素和内部可变性的相对作用。在这里，我们提出了在过去1200年的第一个合奏模拟与一个全面的地球系统模型，包括一个完全互动的碳循环。应用最新的重建外部强迫，包括最近的低振幅估计的太阳变化，合奏模拟再现温度演变与重建的范围一致。20世纪的变暖趋势与所有工业化前的趋势相比都很突出。火山爆发对于解释小冰期等工业化前气候的变化是必要的;然而，只有最强烈的、重复的火山爆发才会导致冷却趋势，这种趋势与所有集合成员的内部变化显著不同。模拟的大气CO2浓度在前工业时代表现出稳定的碳循环，其百年变化略小于观测记录。早期的土地覆盖变化对大气中CO2浓度的影响很小。我们提供了一个基于模型的量化的敏感性（称为伽马）的全球碳循环的温度为各种气候和强迫条件。我们诊断的强迫强度和时间尺度上的一个明显的依赖伽马，从而提供了一个可能的解释，在观测估计的不同部分的上个千年的系统性差异。
A long-standing task in climate research has been to distinguish between anthropogenic climate change and natural climate variability. A prerequisite for fulfilling this task is the understanding of the relative roles of external drivers and internal variability of climate and the carbon cycle. Here, we present the first ensemble simulations over the last 1200 years with a comprehensive Earth system model including a fully interactive carbon cycle. Applying up-to-date reconstructions of external forcing including the recent low-amplitude estimates of solar variations, the ensemble simulations reproduce temperature evolutions consistent with the range of reconstructions. The 20th-century warming trend stands out against all pre-industrial trends within the ensemble. Volcanic eruptions are necessary to explain variations in pre-industrial climate such as the Little Ice Age; yet only the strongest, repeated eruptions lead to cooling trends that differ significantly from the internal variability across all ensemble members. The simulated atmospheric CO2 concentrations exhibit a stable carbon cycle over the pre-industrial era with multi-centennial variations somewhat smaller than in the observational records. Early land-cover changes have modulated atmospheric CO2 concentrations only slightly. We provide a model-based quantification of the sensitivity (termed gamma) of the global carbon cycle to temperature for a variety of climate and forcing conditions. We diagnose a distinct dependence of gamma on the forcing strength and time-scales involved, thus providing a possible explanation for the systematic difference in the observational estimates for different segments of the last millennium.