Potential Problems Measuring Climate Sensitivity from the Historical Record
Potential Problems Measuring Climate Sensitivity from the Historical Record
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DOI：
10.1175/jcli-d-19-0476.1
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发表时间：
2020-03-01
影响因子：
4.9
通讯作者：
Dessler, Andrew E.
中科院分区：
文献类型：
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作者：
Dessler, Andrew E.
本研究探讨了从历史时期变暖推断出的平衡气候敏感性（ECShist）与气候系统真实ECS （ectrue）之间的潜在偏差。本文主要关注两个可能导致这些数量差异的因素。首先是历史时期内部变率的影响：我们的历史气候记录只是无限可能的轨迹之一，这些不同的轨迹可以产生比平均ECShist低0.3 K到高0.5 K（5%-95%置信区间）的ECShist值。因为这种扩散是由于非强迫的可变性，我把它称为非强迫模式效应。这里分析的模式中的这种非强迫型图效应可追溯到海冰损失的非强迫变率，它影响反照率反馈，以及对流层变暖的非强迫变率，它影响短波云反馈。由于今天的短暂变暖模式与2xCO(2)平衡时的变暖模式之间的差异，还存在强迫模式效应，导致ECShist偏离ectrue。在地表变暖延迟的地区（南大洋、东太平洋和格陵兰岛附近的北大西洋），当平衡接近时，变暖模式的变化导致低层云反馈增强。这种强迫模式效应导致ECShist比ECStrue平均低0.2 K（类似于8%）。这两种模式效应共同产生的净效应可以使ECShist的估计值比ECStrue低0.5 K。
This study investigates potential biases between equilibrium climate sensitivity inferred from warming over the historical period (ECShist) and the climate system's true ECS (ECStrue). This paper focuses on two factors that could contribute to differences between these quantities. First is the impact of internal variability over the historical period: our historical climate record is just one of an infinity of possible trajectories, and these different trajectories can generate ECShist values 0.3 K below to 0.5 K above (5%-95% confidence interval) the average ECShist. Because this spread is due to unforced variability, I refer to this as the unforced pattern effect. This unforced pattern effect in the model analyzed here is traced to unforced variability in loss of sea ice, which affects the albedo feedback, and to unforced variability in warming of the troposphere, which affects the shortwave cloud feedback. There is also a forced pattern effect that causes ECShist to depart from ECStrue due to differences between today's transient pattern of warming and the pattern of warming at 2xCO(2) equilibrium. Changes in the pattern of warming lead to a strengthening low-cloud feedback as equilibrium is approached in regions where surface warming is delayed: the Southern Ocean, eastern Pacific, and North Atlantic near Greenland. This forced pattern effect causes ECShist to be on average 0.2 K lower than ECStrue (similar to 8%). The net effect of these two pattern effects together can produce an estimate of ECShist as much as 0.5 K below ECStrue.