CAMBRIDGE, MASSACHUSETTS—According to a Science Magazine report, archaeologist Michael McCormick of Harvard University and glaciologist Paul Mayewski of the University of Maine say a volcanic eruption in Iceland in A.D. 536 could have been responsible for the fog and drop in temperatures reported in medieval records from Europe, the Middle East, and parts of Asia. Previous studies had linked such changes in climate to cataclysmic volcanic eruptions, but it had been thought the eruption in A.D. 536 might have taken place in North America. McCormick, Mayewski, and their colleagues conducted an “ultraprecise analysis” of slivers of ice from a core taken from a Swiss glacier in 2013, which allowed them to pinpoint the occurrence of storms and volcanic eruptions, as well as levels of lead pollution over the past 2,000 years. The chemical composition of two microscopic particles of volcanic glass, located in a section of the ice core dating to the spring of 536, resembled volcanic rocks from Iceland. Vulcanologist Andrei Kurbatov of the University of Maine said the next step is to look for particles from the volcano in lakes in Europe and Iceland. For more on evidence of past volcanic eruptions, go to “Pinpoint Precision.”