Emulating atmosphere-ocean and carbon cycle models with a simpler model, MAGICC6-Part 2: Applications
Emulating atmosphere-ocean and carbon cycle models with a simpler model, MAGICC6-Part 2: Applications
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DOI：
10.5194/acp-11-1457-2011
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发表时间：
2011-01-01
影响因子：
6.3
通讯作者：
Raper, S. C. B.
中科院分区：
文献类型：
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作者：
Meinshausen, M.;Wigley, T. M. L.;Raper, S. C. B.
耦合大气-海洋环流模式（AOGCMs）和碳循环模式的相互比较对于激发我们当前的科学知识来预测未来气候是重要的。解释这种相互比较面临着重大挑战，尤其是因为不同的模型被不同的强迫因素所强迫。这里，我们将展示使用MAGICC6的仿真方法如何解决此类问题。在另一篇论文（Meinshausen et al., 2011a）中，我们展示了如何对复杂性较低的碳循环-气候模型MAGICC6进行校准，以相当精确地模拟这些更复杂模型的全球汇总特征。在此基础上，我们在这里检查耦合模型相互比较项目的第三阶段结果（CMIP3）。如果考虑CMIP3中单个aogcm遗漏的强迫因子，这将使SRES A1B下从工业化前时代到2100年的总体平均温度变化减少0.4℃。然而，尽管21世纪的轨迹存在一些差异，但1980 - 1999基期（IPCC AR4报告）到2100年的结果差异可以忽略不计。在本研究的第二部分，我们考虑了在即将到来的IPCC第五次评估报告的CMIP5相互比较中将要调查的新的RCP情景。对于最高情景，即RCP8.5，相对于工业化前水平，我们预计到2100年升温中值约为4.6摄氏度，到2300年将超过7摄氏度。对于最低RCP情景，RCP3-PD，根据我们的AOGCM和碳循环模型模拟，到2100年相应的升温约为1.5摄氏度，到2300年降低至1.1摄氏度左右。在规定CO2浓度并考虑碳循环的不确定性时，RCP8.5和RCP3-PD在21世纪的隐含累积CO2排放量分别为1881 GtC （1697 ~ 2034 GtC， 80%的不确定性范围）和381 GtC （334 ~ 488 GtC）。最后，我们评估了为什么IPCC AR4中使用的MAGICC先前版本（4.2）在21世纪的变暖幅度比CMIP3平均值高出约10%的原因。我们发现，强迫差异和使用从理想化的高强迫运行推断的略高的气候敏感性是造成这种差异的主要原因。
Intercomparisons of coupled atmosphere-ocean general circulation models (AOGCMs) and carbon cycle models are important for galvanizing our current scientific knowledge to project future climate. Interpreting such intercomparisons faces major challenges, not least because different models have been forced with different sets of forcing agents. Here, we show how an emulation approach with MAGICC6 can address such problems. In a companion paper (Meinshausen et al., 2011a), we show how the lower complexity carbon cycle-climate model MAGICC6 can be calibrated to emulate, with considerable accuracy, globally aggregated characteristics of these more complex models. Building on that, we examine here the Coupled Model Intercomparison Project's Phase 3 results (CMIP3). If forcing agents missed by individual AOGCMs in CMIP3 are considered, this reduces ensemble average temperature change from pre-industrial times to 2100 under SRES A1B by 0.4 degrees C. Differences in the results from the 1980 to 1999 base period (as reported in IPCC AR4) to 2100 are negligible, however, although there are some differences in the trajectories over the 21st century. In a second part of this study, we consider the new RCP scenarios that are to be investigated under the forthcoming CMIP5 intercomparison for the IPCC Fifth Assessment Report. For the highest scenario, RCP8.5, relative to pre-industrial levels, we project a median warming of around 4.6 degrees C by 2100 and more than 7 degrees C by 2300. For the lowest RCP scenario, RCP3-PD, the corresponding warming is around 1.5 degrees C by 2100, decreasing to around 1.1 degrees C by 2300 based on our AOGCM and carbon cycle model emulations. Implied cumulative CO2 emissions over the 21st century for RCP8.5 and RCP3-PD are 1881 GtC (1697 to 2034 GtC, 80% uncertainty range) and 381 GtC (334 to 488 GtC), when prescribing CO2 concentrations and accounting for uncertainty in the carbon cycle. Lastly, we assess the reasons why a previous MAGICC version (4.2) used in IPCC AR4 gave roughly 10% larger warmings over the 21st century compared to the CMIP3 average. We find that forcing differences and the use of slightly too high climate sensitivities inferred from idealized high-forcing runs were the major reasons for this difference.