Abstract Climate feedbacks have been found to strongly impact the observed amplified Arctic warming. However, Arctic amplification is modeled with a wide spread which partly arises from intermodel differences of the various feedbacks. To explain the spread in modeled Arctic warming, feedback uncertainties and their origins are investigated in 13 climate models in an experiment with abruptly quadrupled CO2. While intermodel differences in the cloud feedback, being strongest in the Tropics, have been found to determine the spread of global mean effective climate sensitivity, we find that in the Arctic the cloud feedback is not responsible for the spread of Arctic warming as its contribution is too small. Instead, the spread of Arctic warming is explained by differing estimates of surface albedo and Planck feedbacks which show the largest intermodel differences. Our results indicate that these uncertainties not only arise from different degrees of simulated Arctic warming but also are partly related to the large differences in initial sea ice cover and surface temperatures which contribute to the increased spread in estimated warming compared to lower latitudes. Further investigations of feedback dependencies to the base state are needed to constrain the impact of initial uncertainties and to obtain robust results. The most significant distinction between models is the sign of the total feedback parameter. While all models investigated here simulate a negative global mean total feedback, only half of them also show negative Arctic feedbacks which implies that Arctic local feedbacks alone suffice to stably adjust Arctic surface temperatures in response to a radiative perturbation. The other half exhibits positive total Arctic feedbacks indicating local runaway systems which need to be balanced by decreased meridional heat transports. Whether or not a model features such a behaviour depends upon the strength of the simulated positive surface albedo versus the negative Planck feedback.

中文翻译：

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气候模型对北极总辐射反馈的符号存在分歧

摘要 已发现气候反馈对观测到的北极变暖产生了强烈影响。然而，北极放大模型的范围很广，部分原因是各种反馈的模型间差异。为了解释模拟的北极变暖的扩散，在 CO2 突然增加四倍的实验中，在 13 个气候模型中研究了反馈不确定性及其起源。虽然已经发现云反馈的模式间差异（在热带地区最强）决定了全球平均有效气候敏感性的传播，但我们发现在北极，云反馈不应对北极变暖的传播负责，因为它的贡献是太小。反而，北极变暖的蔓延是通过对地表反照率和普朗克反馈的不同估计来解释的，这表明模型间差异最大。我们的结果表明，这些不确定性不仅来自不同程度的模拟北极变暖，而且部分与初始海冰覆盖和表面温度的巨大差异有关，与低纬度地区相比，这些差异导致估计变暖的扩散增加。需要进一步研究对基态的反馈依赖性，以限制初始不确定性的影响并获得稳健的结果。模型之间最显着的区别是总反馈参数的符号。虽然这里研究的所有模型都模拟了负的全局平均总反馈，其中只有一半还显示出北极负反馈，这意味着仅北极本地反馈就足以稳定调整北极表面温度以响应辐射扰动。另一半表现出积极的总北极反馈，表明局部失控系统需要通过减少的经向热传输来平衡。模型是否具有这种行为取决于模拟的正表面反照率与负普朗克反馈的强度。