Maximum Latewood Density Analysis Solves Long‐Standing Mystery Between Temperature Reconstructions and Historical Records.

Edwards et al. (2022, https://doi.org/10.1029/2021pa004386) take tree ring samples from Scots pine trees in Sämtland, Sweden, and analyze them to reconstruct the summer temperatures for 1783. The maximum latewood density data for 1783 are low, suggesting cooler temperatures. The authors conclude that anatomical anomalies in their samples resulted from acidic damage caused by the Laki haze, a dry and sulfuric smelling fog emitted by the Laki fissure in Iceland during its eruption, which lasted from 8 June 1783 to 7 February 1784. This finding resolves a long‐standing discrepancy between historical documents that indicate an unusually warm summer in 1783 and temperature reconstructions based on tree rings that often suggested a cooler summer. The paper by Edwards et al. (2022, https://doi.org/10.1029/2021pa004386) thereby shows the potential of interdisciplinary collaborations: Only by studying historical records does it becomes apparent that the summer was not cold but warm. Historical records indicate further that the Laki haze also affected the vegetation in other parts of Europe, such as England, the Low Countries, and Germany. Further study of tree rings to reconstruct the temperature of other regions is desirable. Plain Language Summary: Edwards et al. (2022, https://doi.org/10.1029/2021pa004386) collected tree samples from Sämtland in Sweden to study their rings, specifically those rings pertaining to their maximum latewood density. The analysis, focusing on the period from 1768 to 1798, has shown that the anatomy of the latewood of these trees was anomalous for the year 1783. The authors propose that this was caused by the acidic, dry fog produced by the Laki eruption in Iceland. This eruption released very large volumes of sulfur dioxide and other volcanic gases into the atmosphere, which traveled widely across the northern hemisphere. Because the acidic fog changed the anatomy of the trees, their rings were no longer suitable to read the temperature for the summer of 1783 accurately. These tree rings seemed to indicate that it was cold, but historical records strongly suggest that the summer was, in fact, very warm. Natural scientists and historians can only reach such conclusions when they work together. Key Points: The findings by Edwards et al. (2022) resolve a discrepancy between historical documents and tree ring‐based temperature reconstructionsWithout an analysis of the historical records that show a warm summer, this discrepancy would not have become apparentHistorical records reveal other areas (Low Countries, Germany) also experienced vegetation damage and have potential for further studies [ABSTRACT FROM AUTHOR]