There was a close relationship between temperature shifts between 1970 and 2004 and changes in plants, animals and the physical world, such as the retreat of glaciers and the water level in desert lakes, the study found.

"When you look at all of the glaciers and all of the snowpack and all of the birds laying eggs earlier and all of the plants having spring earlier across a continent, then we see we can detect anthropogenic signals," said Cynthia Rosenzweig of NASA's Goddard Institute for Space Studies.

They worked to rule out observed changes that could have been caused by other factors besides anthropogenic climate change.

Building on research done to support findings reported in 2007 by the UN's Intergovernmental Panel on Climate Change, Rosenzweig and her co-authors brought together nearly 30,000 sets of data about biological and physical changes around the world, and then matched that up with a detailed database of global temperature change.

PENGUINS, POLAR BEARS AND POLLEN

"We overlay those two global datasets and then we do a spatial pattern analysis globally about the co-location of significant temperature trends and observed changes consistent with warming," Rosenzweig said in a telephone interview. "We see that those are strongly co-located."

The link between human-caused global warming -- generated by industrial and vehicle emissions of carbon dioxide to produce a temperature-boosting greenhouse effect -- and observed biological and physical changes is very strong, she said.

On a global scale, the correlation is more than 99 percent between the two factors; on a continental scale, she said, the correlation if very likely between 90 and 99 percent.

Going continent by continent, here are some observed changes in the natural world attributable to climate change, according to the study:

NORTH AMERICA: Earlier plant flowering of 89 species from American holly to sassafras; intraspecific predation, cannibalism and declining population of polar bears; earlier breeding and arrival dates of birds including robins and Canada geese.

EUROPE: Glacier melting in the Alps; changes in 19 countries of leaf-unfolding and flowering of such plants as hazel, lilac, apple, linden and birch; early pollen release in the Netherlands; long-term changes in fish communities in Upper Rhone River.

ASIA: Greater growth of Siberian pines in Mongolia; earlier break-up and thinning of river and lake ice in Mongolia; change in freeze depth of permafrost in Russia; earlier flowering of gingko in Japan.

SOUTH AMERICA: Glacier wastage in Peru; melting Patagonia ice fields contributing to sea-level rise.

AFRICA: Decreasing aquatic ecosystem productivity of Lake Tanganyika.

AUSTRALIA: Early arrival of migratory birds including flycatchers and fantails; declining water levels in Western Victoria.

ANTARCTICA: 50 percent decline in population of emperor penguins on Antarctic Peninsula; retreating glaciers.