The Northern Hemisphere

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Eighteen Hundred and Froze to Death In 1816, sections of the northern hemisphere experienced a “year without a summer.” The average summer temperatures across the northeastern United States, Canadian Maritime Provinces and much of Europe were colder than any other year in the previous 600 years, with the exception of the summer of 1601. The estimated mean surface temperature anomaly for the northern hemisphere in 1816 is -0.51 K. In Europe, temperatures averaged 1-2 C cooler than was typical of the surrounding years, and there was also an increase in precipitation. The most common explanation for this climate anomaly is that it was caused by the 1815 eruption in Indonesia of Tambora, “the largest known eruption in history.” The summer of 1816 also occurred during a period of reduced solar activity, known as the Dalton Minimum, which may have contributed as well. Fig. 1. “Reconstructed surface temperature anomalies computed from latewood density in tree rings for summer 1816. Source: based on data in Briffa et al. (1998)” The map above shows the areas affected most, determined through the use of dendrochronological data (derived from tree rings). Geneva In addition to dendrochronological data, there is also an instrumental record for 1816 and the surrounding years. In Geneva, Switzerland, there is a record of twice-daily weather observations made from 1799 to 1821 without change in instruments or location. The report includes “measurements of air temperature
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