Toward a New Estimate of "Time of Emergence'' of Anthropogenic Warming: Insights from Dynamical Adjustment and a Large Initial-Condition Model Ensemble
Toward a New Estimate of "Time of Emergence'' of Anthropogenic Warming: Insights from Dynamical Adjustment and a Large Initial-Condition Model Ensemble
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DOI：
10.1175/jcli-d-16-0792.1
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发表时间：
2017-10-01
影响因子：
4.9
通讯作者：
Terray, Laurent
中科院分区：
文献类型：
--
作者：
Lehner, Flavio;Deser, Clara;Terray, Laurent
人为气候变化出现的时间是围绕未来气候预测进行风险评估的一个关键指标。然而，内部气候变率削弱了准确说明气候变化何时从背景参考状态出现的能力。现有的努力，探索出现时间的不确定性，明确探讨了内部大气环流变异的作用。在这里，一个动态调整方法的基础上构建的循环类似物是用来提供新的估计出现的时间在北美和欧洲的人为变暖从本地和空间聚集的角度来看。在消除内部大气环流变率的影响后，在北美和欧洲，人为变暖的出现平均在冬季提前20年，在夏季提前10年。动态调整使北美和欧洲冬季出现变暖的陆地面积百分比分别增加约30%和15%（夏季为10%和5%）。使用一个大的合奏模拟与气候模型，证据表明，热力学因素相关的积雪，海冰和土壤水分的变化是重要的驱动力，其余的不确定性出现的时间。变异性的模型偏差导致低估（北美为13%-22%，
Time of emergence of anthropogenic climate change is a crucial metric in risk assessments surrounding future climate predictions. However, internal climate variability impairs the ability to make accurate statements about when climate change emerges from a background reference state. None of the existing efforts to explore uncertainties in time of emergence has explicitly explored the role of internal atmospheric circulation variability. Here a dynamical adjustment method based on constructed circulation analogs is used to provide new estimates of time of emergence of anthropogenic warming over North America and Europe from both a local and spatially aggregated perspective. After removing the effects of internal atmospheric circulation variability, the emergence of anthropogenic warming occurs on average two decades earlier in winter and one decade earlier in summer over North America and Europe. Dynamical adjustment increases the percentage of land area over which warming has emerged by about 30% and 15% in winter (10% and 5% in summer) over North America and Europe, respectively. Using a large ensemble of simulations with a climate model, evidence is provided that thermodynamic factors related to variations in snow cover, sea ice, and soil moisture are important drivers of the remaining uncertainty in time of emergence. Model biases in variability lead to an underestimation (13%-22% over North America and