Abstract

El Niños are periods of warming of equatorial ocean surfaces in the Pacific. This lecture discusses variable teleconnections and possible effects of El Niño on North Atlantic/European regional climates. Two different types of El Niños (the Central Pacific, or CP, and the East Pacific, or EP) result in remarkably different European winter temperature anomalies, specifically weak warming during EP and significant cooling during CP El Niños. We propose a tropospheric bridge as the mechanism primarily responsible for the establishment of a negative NAO phase and of associated cold European winters. As global warming scenarios project an increase in the frequency of CP El Niño events, the distinctive nature of this mechanism implies that the probability of cold European winters may increase as well in future decades.