Multi-centennial internal variability in the North Atlantic could drive additional warming over Europe

Europe has experienced abnormal warming over the recent decades. Model-based studies highlight that multi-centennial internal variability of the North Atlantic can strongly affect European temperatures. However, the limited availability of high-resolution proxy records has hindered observational assessment of the existence and amplitude of such variability in the real climate system. Here, we compile annual-to-decadal proxy-based Holocene reconstructions, instrumental observations, and climate model simulations to demonstrate the existence of this multi-centennial variability mode and quantify its amplitude. We show that this mode is closely tied to the internal variability of the Atlantic Meridional Overturning Circulation. Its temporal evolution explains part of the observed 20th century variability, and a shift towards a positive phase in the late 1990s can explain the recent amplified warming over Europe. When its amplitude is constrained by observations, this internal variability may enhance anthropogenic warming in Northern Europe by up to 30% over 2000–2035. The existence of multi-centennial natural variability in the North Atlantic is demonstrated over the last millennia by compiling proxy data. This variability mode will potentially amplify northern Europe warming by up to 30% over 2000-2035.