Iberia in 1816, the year without a summer

The year 1816 was characterized by unusual weather conditions, in particular, by a cold and wet summer season (‘year without a summer’) on both the European and North American continents. The eruption of Tambora, an active stratavolcano, on the Island of Sumbaya (Indonesia) in April 1815 has been identified as the main driving force for the strong 1816 temperature anomaly. This climate anomaly has been relatively well studied in central Europe, France, Scandinavia and the United Kingdom. The unusual unsettled weather and climate at mid-latitudes in 1816 and 1817 had major socioeconomic impacts, particularly in terms of a poor yield of agricultural production, malnutrition and consequentially an increased potential for diseases and epidemics. The Iberian Peninsula was also affected by the intense climate anomalies during those years. Documentary sources describe the impact that the cold and wet summer of 1816 had on agriculture, namely the bad quality of fruits, delayed ripening of vineyards and cereals. It is within this context that we stress the relevance of recently recovered meteorological observed data, from 1816 onwards, for stations located in Portugal (Lisbon) and also for a longer period for the Spanish stations of Madrid, Barcelona and San Fernando-Cadiz. We have compared observed (station-based) and large-scale reconstructed seasonal temperature anomalies computed for the winter and summer seasons after the eruption (1816–1818). There is qualitative agreement between the two independent data sets, though some stations partly indicate stronger departures from the long-term averages for single years compared to neighbouring grid points. In particular, all available stations reveal a cold summer of 1816, mainly in July and August. In comparison to the 1871–1900 reference period, those two months were 2–3 °C cooler, close to what has been reported for central Europe. We also discuss the regional climate anomalies for those years (1816–1818) using independently reconstructed atmospheric circulation fields.