John Magnuson, an ecologist at the University of Wisconsin-Madison, was introduced to the Japanese and Finnish data in the 1990s, when he convened an international group of scientists to compare ice records from across the Northern Hemisphere. Only recently, however, did Magnuson team up with ecologist Sapna Sharma of Toronto’s York University for a more detailed analysis of the very longest records. Magnuson, Sharma and their colleagues arranged for translations of the notations—some of which were made on fragile rice paper—consulted experts about local conditions, and, in the case of the Lake Suwa data, struggled to decode a calendar that not only differed from the Western calendar but varied depending on which shrine was using it. “It was a truly interdisciplinary project,” says Sharma.