Natural unforced variability in global mean surface air temperature (GMST) can mask or exaggerate human-caused global warming, and thus a complete understanding of this variability is highly desirable. Significant progress has been made in elucidating the magnitude and physical origins of present-day unforced GMST variability, but it has remained unclear how such variability may change as the climate warms. Here we present modelling evidence that indicates that the magnitude of low-frequency GMST variability is likely to decline in a warmer climate and that its generating mechanisms may be fundamentally altered. In particular, a warmer climate results in lower albedo at high latitudes, which yields a weaker albedo feedback on unforced GMST variability. These results imply that unforced GMST variability is dependent on the background climatological conditions, and thus climate model control simulations run under perpetual pre-industrial conditions may have only limited relevance for understanding the unforced GMST variability of the future.

中文翻译：

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全球变暖的幅度和机制随变暖而变化

全球平均地面气温（GMST）的自然不受强迫的变化会掩盖或夸大人为造成的全球变暖，因此非常需要对这种变化有完整的了解。在阐明当今非强制性GMST变率的大小和物理成因方面取得了重大进展，但仍不清楚这种变率如何随着气候变暖而改变。在这里，我们提供的建模证据表明，在温暖的气候下，低频GMST变异性的幅度可能会下降，并且其发生机理可能会发生根本性的改变。特别是，气候变暖会导致高纬度地区的反照率降低，这会导致非强制GMST变率的反照率反馈变弱。