On September 15th 2020, Arctic sea ice extent (SIE) ranked second-to-lowest in history and keeps trending downward. The understanding of how feedback loops amplify the effects of external CO2 forcing is still limited. We propose the VARCTIC, which is a Vector Autoregression (VAR) designed to capture and extrapolate Arctic feedback loops. VARs are dynamic simultaneous systems of equations, routinely estimated to predict and understand the interactions of multiple macroeconomic time series. The VARCTIC is a parsimonious compromise between full-blown climate models and purely statistical approaches that usually offer little explanation of the underlying mechanism. Our completely unconditional forecast has SIE hitting 0 in September by the 2060's. Impulse response functions reveal that anthropogenic CO2 emission shocks have an unusually durable effect on SIE -- a property shared by no other shock. We find Albedo- and Thickness-based feedbacks to be the main amplification channels through which CO2 anomalies impact SIE in the short/medium run. Further, conditional forecast analyses reveal that the future path of SIE crucially depends on the evolution of CO2 emissions, with outcomes ranging from recovering SIE to it reaching 0 in the 2050's. Finally, Albedo and Thickness feedbacks are shown to play an important role in accelerating the speed at which predicted SIE is heading towards 0.

翻译：2020年9月15日,北极海冰度(SIE)位居历史第二位至下方,并一直呈下降趋势。对反馈环状如何扩大外部二氧化碳压力效应的理解仍然有限。我们提议VARCTIC(VARTIC),这是一个旨在捕捉和外推北极反馈环的矢量自动回归(VAR),这是动态的同步方程系统,定期估算以预测和理解多种宏观经济时间序列的相互作用。VARCTIC(SIE)是全传气候模型和通常很少解释基本机制的纯统计方法之间的一个模糊的折中妥协。我们完全无条件的预测是2060年代的9月SIE(SIE)打击了0。内断层反应功能显示,人为二氧化碳排放冲击对SIE(VIE)具有不寻常的持久影响。我们发现阿尔贝多和特克内反馈是主要的振荡渠道,通过它来影响SIE(SIE)在短中运行。此外,有条件的预测分析显示,SIE(SIE)未来路径在20世纪50年代的加速度反馈将最终取决于SIE(SIE)到S-H)的预测结果。