Arctic sea ice has declined precipitously in both extent and thickness over the past four decades; by contrast, Antarctic sea ice has shown little overall change, but this masks large regional variability. Climate models have not captured these changes. But these differences do not represent a paradox. The processes governing, and impacts of, natural variability and human-induced changes differ markedly at the poles largely because of the ways in which differences in geography control the properties of and interactions among the atmosphere, ice, and ocean. The impact of natural variability on the ice cover is large at both poles, so modeled ice trends are not entirely inconsistent with contributions from both natural variability and anthropogenic forcing. Despite this concurrence, the coupling of natural climate variability, climate feedbacks, and sea ice is not well understood, and significant biases remain in model representations of the ice cover and the processes that drive it.

中文翻译：

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北极和南极海冰变化：对比，共性和原因。

在过去的40年中，北极海冰的范围和厚度都急剧下降。相比之下，南极海冰的总体变化很小，但这掩盖了较大的区域变化。气候模型尚未捕捉到这些变化。但是这些差异并不代表悖论。自然变化和人为变化的控制过程及其影响在极点上显着不同，这在很大程度上是因为地理差异控制着大气，冰和海洋的特性以及它们之间的相互作用的方式。自然可变性在两个极点上对冰盖的影响都很大，因此模拟的冰层趋势与自然可变性和人为强迫的贡献并不完全矛盾。尽管有这样的共识，但自然气候变异性，气候反馈，