On the climatic influence of CO2 forcing in the Pliocene
On the climatic influence of CO2 forcing in the Pliocene
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DOI：
10.5194/cp-19-747-2023
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发表时间：
2023-03
影响因子：
4.3
通讯作者：
Lauren E. Burton;A. Haywood;J. Tindall;A. Dolan;D. J. Hill;A. Abe‐Ouchi;W. Chan;D. Chandan
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作者：
Lauren E. Burton;A. Haywood;J. Tindall;A. Dolan;D. J. Hill;A. Abe‐Ouchi;W. Chan;D. Chandan
抽象的。了解上新世的主要气候压力，对于评估上新世作为我们变暖未来的类比的有用性至关重要。在这里，我们实施了一种新的但简单的线性分解方法来评估上新世模式比较项目第二阶段(PlioMIP2)集合的七个模式中二氧化碳强迫的相对影响。产出被称为“FCO2”，显示了二氧化碳在上新世气候变化中所占的比例。FCO2方法的准确性首先通过与以前用于评估PlioMIP1集合中地表气温驱动因素的能量平衡分析进行比较来评估。在这一评估之后，首次应用FCO2方法来了解上新世海表温度和降水的驱动因素。CO2是上新世地表气温(全球平均FCO2=0.56)、海表面温度(全球平均FCO2=0.56)和降水(全球平均FCO2=0.51)的最重要的强迫。这三个气候变量之间的各个模式之间的范围是一致的，模式在最重要的强迫符号上总体上表现出很好的一致性。我们的结果提供了迄今为止最完整的上新世气候驱动因素的空间视图，并对数据模型比较和未来使用上新世作为类比具有一定的意义。CO2被发现是最重要的强迫，这加强了上新世作为一个很好的古气候模拟的作用，但区域尺度上的非CO2强迫(例如，高纬度的地形和冰盖强迫)的显著影响提醒我们，它并不完美，这些额外的影响因素不容忽视。当认为上新世处于准平衡状态时，与目前经历的瞬时变暖相比，这种比较更加复杂。
Abstract. Understanding the dominant climate forcings in the Pliocene is crucial to assessing the usefulness of the Pliocene as an analogue for our warmer future. Here, we implement a novel yet simple linear factorisation method to assess the relative influence of CO2 forcing in seven models of the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble. Outputs are termed “FCO2” and show the fraction of Pliocene climate change driven by CO2. The accuracy of the FCO2 method is first assessed through comparison to an energy balance analysis previously used to assess drivers of surface air temperature in the PlioMIP1 ensemble. After this assessment, the FCO2 method is applied to achieve an understanding of the drivers of Pliocene sea surface temperature and precipitation for the first time. CO2 is found to be the most important forcing in the ensemble for Pliocene surface air temperature (global mean FCO2=0.56), sea surface temperature (global mean FCO2=0.56), and precipitation (global mean FCO2=0.51). The range between individual models is found to be consistent between these three climate variables, and the models generally show good agreement on the sign of the most important forcing. Our results provide the most spatially complete view of the drivers of Pliocene climate to date and have implications for both data–model comparison and the use of the Pliocene as an analogue for the future. That CO2 is found to be the most important forcing reinforces the Pliocene as a good palaeoclimate analogue, but the significant effect of non-CO2 forcing at a regional scale (e.g. orography and ice sheet forcing at high latitudes) reminds us that it is not perfect, and these additional influencing factors must not be overlooked. This comparison is further complicated when considering the Pliocene as a state in quasi-equilibrium with CO2 forcing compared to the transient warming being experienced at present.