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arXiv 2207.06110physics.ao-phmath.DS
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气候响应和敏感性:时间尺度和后期临界点

Climate Response and Sensitivity: Timescales and Late Tipping Points

Robbin Bastiaansen, Peter Ashwin, Anna S. von der Heydt

摘要:

气候响应指标用于量化地球对大气CO2人为变化的气候响应。平衡气候敏感性(ECS)就是这样一个度量标准,它测量了对CO2加倍的平衡响应。然而,无论是在其估计和使用,这些指标的气候响应的线性假设,虽然它是已知的,特别是对于较大的强迫水平,响应可以是非线性的。这样的非线性响应可以响应于较大的扰动而立即变得可见,或者可以仅在长的瞬态之后变得明显。在本文中,我们说明了一些潜在的问题和警告时,估计ECS从瞬态模拟。我们强调的方式,非常慢的时间尺度可能会导致不良的估计ECS,即使有似乎很好的适合在中等时间尺度的线性响应。此外,这种缓慢的时间尺度可能会导致与系统的非线性相关的后期突然响应(“后期临界点”)。我们说明了这些想法,使用模拟的全球能源平衡模型与动态的CO2。我们还讨论了估计ECS的全球气候模型的影响,强调它可能仍然很难作出明确的声明所需的模拟时间达到平衡。

英文摘要:

Climate response metrics are used to quantify the Earth's climate response to anthropogenic changes of atmospheric CO2. Equilibrium Climate Sensitivity (ECS) is one such metric that measures the equilibrium response to CO2 doubling. However, both in their estimation and their usage, such metrics make assumptions on the linearity of climate response, although it is known that, especially for larger forcing levels, response can be nonlinear. Such nonlinear responses may become visible immediately in response to a larger perturbation, or may only become apparent after a long transient. In this paper, we illustrate some potential problems and caveats when estimating ECS from transient simulations. We highlight ways that very slow timescales may lead to poor estimation of ECS even if there is seemingly good fit to linear response over moderate timescales. Moreover, such slow timescale might lead to late abrupt responses ("late tipping points") associated with a system's nonlinearities. We illustrate these ideas using simulations on a global energy balance model with dynamic albedo. We also discuss the implications for estimating ECS for global climate models, highlighting that it is likely to remain difficult to make definitive statements about the simulation times needed to reach an equilibrium.

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