Scientists are poring over the diaries of 17th century Swiss monks and Parisian physicians for data to help judge changes in Europe’s climate, the AP reports. Piecing together records from things as disparate as military campaigns and cherry blossom festivals dispels any doubt that the Earth is heating up, according to climate historian Christian Pfister. Last winter was Europe’s warmest in 500 years, Pfister says.
Anecdotal evidence from surviving documents—the monks record a January so cold the communion wine froze in its chalice; a late harvest because "there was hardly ever a really warm day"—fills in the blanks before thermometers were standardized in the 19th century. And concerns about global warming have transformed what Pfister says was once a "wallflower science" into a dynamic discipline.