The Smithsonian reports [2] further evidence of climate change comes from Walden Pond, where plants in 2012 bloomed earlier than ever before recorded - and records go back to 1852, when Henry David Thoreau kept track:
"We were amazed that wildflowers in Concord flowered almost a month earlier in 2012 than they did in Thoreau’s time or any other recent year, and it turns out the same phenomenon was happening in Wisconsin where Aldo Leopold was recording flowering times," lead author Elizabeth Ellwood of Boston University said in a statement. "Our data shows that plants keep shifting their flowering times ever earlier as the climate continues to warm."
Via Jason Mihalko [3].