Carbon-concentration and carbon-climate feedbacks in CMIP6 models and their comparison to CMIP5 models
Carbon-concentration and carbon-climate feedbacks in CMIP6 models and their comparison to CMIP5 models
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DOI：
10.5194/bg-17-4173-2020
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发表时间：
2020-08-18
期刊：
影响因子：
4.9
通讯作者：
Ziehn, Tilo
中科院分区：
文献类型：
--
作者：
Arora, Vivek K.;Katavouta, Anna;Ziehn, Tilo
本文分析了CO2比工业化前值以1%年（-1）（1pctCO2）的速率增加的完全耦合模拟和生物地球化学耦合模拟的结果，以量化碳浓度和碳气候反馈参数的量级，这些参数分别测量海洋和陆地碳库对大气CO2浓度变化和由此引起的全球气候变化的响应。结果基于最新的第六次耦合模式比对项目（CMIP6）的11个综合地球系统模型，并与第五次耦合模式比对项目（CMIP5）的8个模型进行了比较。陆地（平均+/-标准差= 0.97 +/- 0.40 PgC ppm(-1)）和海洋（0.79 +/- 0.07 PgC ppm(-1)）的碳浓度反馈强度相当，而陆地（-45.1 +/- 50.6 PgC°C-1）的碳-气候反馈强度约为海洋（-17.2 +/- 5.0 PgC°C-1）的3倍。正如现有研究中所看到的那样，这两种反馈的强度在陆地上比在海洋上的不确定性要大一个数量级。与CMIP5模式相比，11个CMIP5模式的这些值及其分布没有显著变化。对于包含氮循环表示的陆地模型，反馈参数的绝对值较低。本文考虑的11个CMIP6模式对累积排放的瞬态气候响应（tcree）为1.77 +/- 0.37°C EgC(-1)，与CMIP5模式（1.63 +/- 0.48°C EgC(-1)）相似，但模式范围有所缩小。在忽略生物地球化学耦合模拟中的微小温度变化时，简化了基于1pctCO2模拟的全耦合和生物地球化学耦合配置的反馈参数表达式。通过对反馈参数的这些简化表达式的项进行分解，可以深入了解海洋和陆地碳循环模型之间响应不同的原因。
Results from the fully and biogeochemically coupled simulations in which CO2 increases at a rate of 1 % yr(-1) (1pctCO2) from its preindustrial value are analyzed to quantify the magnitude of carbon-concentration and carbon-climate feedback parameters which measure the response of ocean and terrestrial carbon pools to changes in atmospheric CO2 concentration and the resulting change in global climate, respectively. The results are based on 11 comprehensive Earth system models from the most recent sixth) Coupled Model Intercomparison Project (CMIP6) and compared with eight models from the fifth CMIP (CMIP5). The strength of the carbon-concentration feedback is of comparable magnitudes over land (mean +/- standard deviation = 0.97 +/- 0.40 PgC ppm(-1)) and ocean (0.79 +/- 0.07 PgC ppm(-1)), while the carbon-climate feedback over land (-45.1 +/- 50.6 PgC degrees C-1) is about 3 times larger than over ocean (-17.2 +/- 5.0 PgC degrees C-1). The strength of both feedbacks is an order of magnitude more uncertain over land than over ocean as has been seen in existing studies. These values and their spread from 11 CMIP6 models have not changed significantly compared to CMIP5 models. The absolute values of feedback parameters are lower for land with models that include a representation of nitrogen cycle. The transient climate response to cumulative emissions (TCRE) from the 11 CMIP6 models considered here is 1.77 +/- 0.37 degrees C EgC(-1) and is similar to that found in CMIP5 models (1.63 +/- 0.48 degrees C EgC(-1)) but with somewhat reduced model spread. The expressions for feedback parameters based on the fully and biogeochemically coupled configurations of the 1pctCO2 simulation are simplified when the small temperature change in the biogeochemically coupled simulation is ignored. Decomposition of the terms of these simplified expressions for the feedback parameters is used to gain insight into the reasons for differing responses among ocean and land carbon cycle models.