In 95 percent of the physical systems and 90 percent of the living systems, the changes are consistent with the predicted effects of a warming climate, according to the researchers.
The team then used statistical analyses to compare the trends to global and continental temperature changes and found a strong link.
"It is very unlikely for there to be any other reason for those linkages, other than the human influence on the temperature," said Cynthia Rosenzweig, a scientist at the NASA Goddard Institute for Space Studies in New York and lead author of the study.
At the continental scale, the link was strongest in North America, Asia, and Europe. Central and South America, Africa, and Australia lack sufficient data for a robust correlation, she noted.
Rosenzweig, Root, and colleagues from nine other institutions report their findings in tomorrow's issue of the journal Nature.
David Inouye is a biologist at the University of Maryland in College Park who has worked at the Rocky Mountain Research Laboratory in Colorado to document the earlier arrival of spring.
He was not involved with the new paper, which he said is a "major contribution" to making a connection between human-induced warming and observed changes.
Inouye has not yet made a direct link in his own work, but based on the findings of other researchers, he said, "I can assume there is a link there."
Call for Action?
Roger Pielke, Jr., is a political scientist and professor of environmental studies at the University of Colorado at Boulder.
He said via email that the new study would likely be "used promotionally to advocate for a greater pace of action of mitigation and/or adaptation" to climate change.
But whether such a strategy is effective, he added, is debatable.
"I would probably lean toward thinking that such use of these studies can have a numbing effect on the public."
Root, the Stanford University study co-author, said the message from the analysis is more of the same but worth noting because it highlights the need for adaptation to a warming world.
"Any time we can get people to notice that global warming is affecting us right now is good," she said.
"What we're doing is finding a lot more instances of it."
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