The Arctic is rapidly warming and experiencing tremendous changes in sea ice, ocean and terrestrial regions. Lack of long-term scientific observations makes it difficult to assess whether Arctic changes statistically represent a ‘new Arctic’ climate. Here we use five Coupled Model Intercomparison Project 5 class Earth system model large ensembles to show how the Arctic is transitioning from a dominantly frozen state and to quantify the nature and timing of an emerging new Arctic climate in sea ice, air temperatures and precipitation phase (rain versus snow). Our results suggest that Arctic climate has already emerged in sea ice. Air temperatures will emerge under the representative concentration pathway 8.5 scenario in the early- to mid-twenty-first century, followed by precipitation-phase changes. Despite differences in mean state and forced response, these models show striking similarities in their anthropogenically forced emergence from internal variability in Arctic sea ice, surface temperatures and precipitation-phase changes.

北极正在迅速升温，并且在海冰，海洋和陆地地区经历了巨大的变化。由于缺乏长期的科学观察，很难评估北极的变化是否从统计学上代表了“新的北极”气候。在这里，我们使用五个耦合模型比较项目5类地球系统大型集合模型来展示北极如何从占主导地位的冰冻状态过渡，并量化海冰，空气温度和降水相中新兴的北极新气候的性质和时间（雨与雪）。我们的结果表明，北极气候已经出现在海冰中。在二十一世纪初至二十世纪中叶，气温将在具有代表性的浓度路径8.5情景下出现，随后是降水阶段的变化。