Every historian knows about the Rosetta Stone, which had an ancient Egyptian text carved on it in three different scripts, two of which had long resisted translation. The ability to cross-correlate the scripts—to calibrate their alphabets—opened up a huge body of knowledge to scholars. Climate researchers, as well as archaeologists and geologists, look for similar natural records that allow us to calibrate different yardsticks of time. A paper published in the journal Science unveils a superb “document” of conditions during the last 53,000 years in a single place: Japan’s remarkable Lake Suigetsu.