Impact of El Nino Southern Oscillation on European climate

El Nino-Southern Oscillation (ENSO) is arguably the most important global climate pattern. While the effects in the Pacific-North American sector and the tropical regions are relatively well understood, the impacts on the circulation in the North Atlantic-European sector are discussed more controversially. Studies from the past 10 years demonstrate that ENSO does affect European climate. However, some of the effects undergo a seasonal modulation or are nonlinear. The signal can be modified by other factors and might be nonstationary on multidecadal scales, contributing to a large interevent variability. Here I review observational and model-based evidence for ENSO's effect on European climate and discuss possible mechanisms, also including troposphere-stratosphere coupling. The paper ends with a schematic depiction of the effects and a discussion of their relevance with respect to our scientific understanding of the climate system and of their relevance for seasonal climate forecasts.