The weather of 1740, the coldest year in Central Europe in 600 years

Abstract. The winter 1739/40 is known as one of the coldest winters in Europe since early instrumental measurements began. Many contemporary sources discuss the cold waves and compare the winter to that of 1708/09. It is less well known that the year 1740 remained cold until August and again in October, and that negative temperature anomalies are also found over Eurasia and North America. The 1737/40 cold season over northern midlatitude land areas was perhaps the coldest in 300 years, and 1740 was the coldest year in Central Europe in 600 years. New monthly, global climate reconstructions allow addressing this momentous event in greater detail, while daily observations and weather reconstructions give insight into the synoptic situations. Over Europe, we find that the event was initiated by a strong Scandinavian blocking in early January, allowing the advection continental cold air. From February until June, high pressure dominated over Ireland, arguably associated with frequent East Atlantic blocking. This led to cold air advection from the cold northern North Atlantic. During the summer, cyclonic weather dominated over Central Europe, associated with cold and wet air from the Atlantic. The possible role of oceanic influences (El Niño) and external forcings (eruption of Mount Tarumae in 1739) are discussed. While a possible El Niño event might have contributed to the winter cold spells, the East Atlantic blocking is arguably unrelated to either El Niño or the volcanic eruption. In all, the cold year of 1740 marks one of the strongest, arguably unforced excursions in European temperature.