Japanese priests recorded centuries-worth of climate data

Since at least 1443, Shinto priests living on the edge of Lake Suwa have recorded the date when the lake freezes. Across the globe in 1693, Finnish observers began noting the annual timing of the Torne River's spring ice breakup. Scientists recently analyzed these records and found that ice was forming later in the year, thawing earlier, and the cycles in both places were tied to atmospheric CO₂ concentrations. National Geographic