Washington, D.C.'s famous cherry trees are primed to burst in a perfect pink peak about the end of this month. Thirty years ago, the trees usually waited to bloom until around April 5.
In central California, the first of the field skipper sachem, drab little butterflies, was fluttering about on March 12. Just 25 years ago, that creature predictably emerged there anywhere from mid-April to mid-May.
And sneezes are coming earlier in Philadelphia, Pennsylvania. On March 9, when allergist Donald Dvorin set up his monitor, maple pollen was already heavy in the air. Less than two decades ago, that pollen couldn't be measured until late April.
For biologists, these trends are a worrying sign of the ominous effects of global warming.
The fingerprints of human-caused climate change are evident in seasonal timing changes for thousands of species on Earth, according to dozens of studies and last year's authoritative report by the Nobel-prize winning Intergovernmental Panel on Climate Change.
More than 30 scientists told The Associated Press how global warming is affecting plants and animals at springtime across the country, in nearly every state.
"The alarm clock that all the plants and animals are listening to is running too fast," Stanford University biologist Terry Root said.
Visible From Space
Spring officially arrives on the vernal equinox, which this year occurred today at 1:48 a.m. Eastern time.
But biological timing, known as phenology, has sped up considerably as the world has warmed on average in recent years.
Phenology data goes as far back as the 14th century, when people began tracking the harvest of wine grapes in France. The considerable amount of information shows that while there is a change in the timing of fall, the change is biggest in spring.
In the 1980s in particular there was a sudden, big leap forward in spring blooming, scientists noticed. And spring keeps coming earlier at an accelerating rate.