Historical and idealized climate model experiments: an intercomparison of Earth system models of intermediate complexity
Historical and idealized climate model experiments: an intercomparison of Earth system models of intermediate complexity
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DOI：
10.5194/cp-9-1111-2013
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发表时间：
2013-01-01
影响因子：
4.3
通讯作者：
Zhao, F.
中科院分区：
文献类型：
--
作者：
Eby, M.;Weaver, A. J.;Zhao, F.
历史和理想化气候模型实验都是使用各种中等复杂性的地球系统模型（EMIC）进行的，作为政府间气候变化专门委员会第五次评估报告的社区贡献的一部分。历史模拟从公元 850 年开始，一直持续到 2005 年。标准模拟包括太阳光度、地球轨道结构、二氧化碳、额外温室气体、土地利用以及硫酸盐和火山气溶胶的强迫变化。尽管工业化前全球地表气温的模型有很大不同，但与观测到的趋势相比，20 世纪地表气温和碳吸收的总体趋势得到了相当好的模拟。陆地碳通量在模型之间显示出比海洋碳通量更大的变化，并且最近的陆地通量似乎被略微低估。最近模拟的气候趋势或气候碳反馈可能被高估，导致土地碳损失过多，或者二氧化碳和/或氮肥施肥导致的碳吸收被低估。使用长达数千年的理想化 2 x 和 4 x CO2 实验来量化标准模型特征，包括瞬态和平衡气候敏感性以及气候碳反馈。 EMIC 的值通常落在大气环流模型给出的范围内。七个额外的历史模拟，每个包括一个指定的强迫，用于评估不同气候强迫对整体气候和碳循环响应的贡献。地表气温的响应是各个强迫的线性总和，而碳循环响应显示某些模型的土地利用变化和二氧化碳强迫之间的非线性相互作用。最后，上个千年模拟的前工业化部分用于评估历史模型碳气候反馈。考虑到特定的强迫，EMIC 倾向于低估根据古气候重建估计的中世纪气候异常和小冰河时期之间地表气温和二氧化碳的下降。这反过来可能是由于气候系统内的非受迫变化、温度和二氧化碳重建的不确定性、用于驱动模型的强迫重建的错误或模型中某些过程的不完整表示造成的。考虑到本研究中使用的强迫数据集，这些模型计算了工业化前时期的重要土地利用排放量。这意味着在估计古气候重建的气候碳反馈时可能需要考虑土地利用排放。
Both historical and idealized climate model experiments are performed with a variety of Earth system models of intermediate complexity (EMICs) as part of a community contribution to the Intergovernmental Panel on Climate Change Fifth Assessment Report. Historical simulations start at 850 CE and continue through to 2005. The standard simulations include changes in forcing from solar luminosity, Earth's orbital configuration, CO2, additional greenhouse gases, land use, and sulphate and volcanic aerosols. In spite of very different modelled pre-industrial global surface air temperatures, overall 20th century trends in surface air temperature and carbon uptake are reasonably well simulated when compared to observed trends. Land carbon fluxes show much more variation between models than ocean carbon fluxes, and recent land fluxes appear to be slightly underestimated. It is possible that recent modelled climate trends or climate carbon feedbacks are overestimated resulting in too much land carbon loss or that carbon uptake due to CO2 and/or nitrogen fertilization is underestimated. Several one thousand year long, idealized, 2 x and 4 x CO2 experiments are used to quantify standard model characteristics, including transient and equilibrium climate sensitivities, and climate carbon feedbacks. The values from EMICs generally fall within the range given by general circulation models. Seven additional historical simulations, each including a single specified forcing, are used to assess the contributions of different climate forcings to the overall climate and carbon cycle response. The response of surface air temperature is the linear sum of the individual forcings, while the carbon cycle response shows a non-linear interaction between land-use change and CO2 forcings for some models. Finally, the preindustrial portions of the last millennium simulations are used to assess historical model carbon-climate feedbacks. Given the specified forcing, there is a tendency for the EMICs to underestimate the drop in surface air temperature and CO2 between the Medieval Climate Anomaly and the Little Ice Age estimated from palaeoclimate reconstructions. This in turn could be a result of unforced variability within the climate system, uncertainty in the reconstructions of temperature and CO2, errors in the reconstructions of forcing used to drive the models, or the incomplete representation of certain processes within the models. Given the forcing datasets used in this study, the models calculate significant land-use emissions over the pre-industrial period. This implies that landuse emissions might need to be taken into account, when making estimates of climate carbon feedbacks from palaeoclimate reconstructions.