Quantifying uncertainties of permafrost carbon-climate feedbacks
Quantifying uncertainties of permafrost carbon-climate feedbacks
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DOI：
10.5194/bg-14-3051-2017
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发表时间：
2017-06-22
期刊：
影响因子：
4.9
通讯作者：
Krinner, Gerhard
中科院分区：
文献类型：
--
作者：
Burke, Eleanor J.;Ekici, Altug;Krinner, Gerhard
陆面模型JULES（联合英国陆地环境模拟器，两个版本）和ORCHIDEE-MICT（动态生态系统中的组织碳和水文），每个都有一个修订的永久冻土碳的表示，耦合到气候异常的全球影响综合模型（IMOGEN）中等复杂性气候和海洋碳吸收模型。IMOGEN计算大气中的二氧化碳（CO2）和当地的月表面气候与陆地大气CO2通量交换从JULES或ORCHIDEE-MICT给定的排放情景。这些模拟包括与变暖世界中永久冻土碳变化相关的反馈。IMOGEN-JULES和IMOGEN-ORCHIDEE-MICT都是受历史和三种替代未来CO2排放情景的影响。这些模拟是基于CMIP 3（耦合模型相互比较项目第3阶段）使用的22个不同的地球系统模型（ESM），针对不同的气候敏感性和区域气候变化模式进行的，使我们能够在永久冻土碳气候反馈的背景下探索气候不确定性。使用了与三种代表性浓度路径相一致的三种未来排放情景：RCP2.6、RCP4.5和RCP8.5。为了量化永久冻土碳反馈对气候变化的影响，需要进行有和没有冻结碳过程的成对模拟。到2100年，永久冻土碳反馈的额外变暖是全球平均温度变化（Delta T）的0.2%至12%，到2300年是Delta T的0.5%至17%，这些范围反映了陆地表面模型，气候模型和排放途径的差异。作为Delta T的百分比，冻土碳反馈对低排放情景（RCP 2.6）的影响大于对高排放情景的影响，这表明在评估重大缓解和稳定情景时应考虑冻土碳。陆面模型之间的结构差异（特别是土壤碳分解的代表性）被认为是一个更大的来源的不确定性比气候响应的差异。永久冻土碳系统的惯性意味着永久冻土碳响应取决于变暖的时间轨迹以及变暖的绝对量。我们提出了一个新的政策相关指标-冻结碳停留时间（FCRt）年-可以从这些复杂的陆地表面模型，并用于量化永久冻土碳响应给定的任何途径的全球温度变化。
The land surface models JULES (Joint UK Land Environment Simulator, two versions) and ORCHIDEE-MICT (Organizing Carbon and Hydrology in Dynamic Ecosystems), each with a revised representation of permafrost carbon, were coupled to the Integrated Model Of Global Effects of climatic aNomalies (IMOGEN) intermediate-complexity climate and ocean carbon uptake model. IMOGEN calculates atmospheric carbon dioxide (CO2) and local monthly surface climate for a given emission scenario with the land-atmosphere CO2 flux exchange from either JULES or ORCHIDEE-MICT. These simulations include feedbacks associated with permafrost carbon changes in a warming world. Both IMOGEN-JULES and IMOGEN-ORCHIDEE-MICT were forced by historical and three alternative future-CO2-emission scenarios. Those simulations were performed for different climate sensitivities and regional climate change patterns based on 22 different Earth system models (ESMs) used for CMIP3 (phase 3 of the Coupled Model Intercomparison Project), allowing us to explore climate uncertainties in the context of permafrost carbon-climate feedbacks. Three future emission scenarios consistent with three representative concentration pathways were used: RCP2.6, RCP4.5 and RCP8.5. Paired simulations with and without frozen carbon processes were required to quantify the impact of the permafrost carbon feedback on climate change. The additional warming from the permafrost carbon feedback is between 0.2 and 12% of the change in the global mean temperature (Delta T) by the year 2100 and 0.5 and 17% of Delta T by 2300, with these ranges reflecting differences in land surface models, climate models and emissions pathway. As a percentage of Delta T, the permafrost carbon feedback has a greater impact on the low-emissions scenario (RCP2.6) than on the higher-emissions scenarios, suggesting that permafrost carbon should be taken into account when evaluating scenarios of heavy mitigation and stabilization. Structural differences between the land surface models (particularly the representation of the soil carbon decomposition) are found to be a larger source of uncertainties than differences in the climate response. Inertia in the permafrost carbon system means that the permafrost carbon response depends on the temporal trajectory of warming as well as the absolute amount of warming. We propose a new policy-relevant metric - the frozen carbon residence time (FCRt) in years - that can be derived from these complex land surface models and used to quantify the permafrost carbon response given any pathway of global temperature change.