Britain’s The Guardian newspaper recently reported that the journals of Henry David Thoreau have been recruited to glean crucial insights about global warming. Thoreau, a studious amateur naturalist, recorded the date of first spring-time blooms for a wide variety of plants in his native New England. But comparing Thoreau’s observations with more recent data, Boston University researchers have concluded that today’s flowers are blooming about 10 days earlier – powerful evidence that the Earth’s temperature is rising.

“We had been searching for historical records for about six months when we learned about Thoreau’s plant observations,” Richard Primack, a biology professor at Boston University, told The Guardian. “We knew right away that they would be incredibly useful for climate change research because they were from 150 years ago, there were so many species included, and they were gathered by Thoreau, who is so famous in the United States for his book, Walden.”