BEIJING, Dec. 3 (Xinhuanet) -- Earth's tropical belt is moving toward the poles at a speed faster than expected, another sign of global climate change, scientists reported.

The climate research, published Sunday in the scientific journal Nature Geoscience, shows that the tropics have expanded a couple hundred miles over the past quarter century. That may broaden the area affected by hurricanes and change precipitation patterns in subtropical regions, the study said.

"Remarkably, the tropics appear to have already expanded -- during only the last few decades of the 20th century -- by at least the same margin as models predict for this century," said the scientists.

The researchers using four different meteorological measurements forecast the tropic belt would spread by about 2 degrees of latitude north and south of the Equator by the end of the 21st century.

Geographically, the tropical region is a wide swath around Earth's middle stretching from the Tropic of Cancer to the Tropic of Capricorn. But climate scientists define the tropic band by what happens on the land, in the water and in the air, and that is what is changing, the study said.

Climate scientists have long predicted a growing tropical belt toward the end of the 21st century because of man-made global warming. But what has happened in the past quarter century is larger and more puzzling than initially predicted, said Dian Seidel, the author of the study.

"They are big changes," she said. "It's a little puzzling."

Tropical temperatures are warm, and it rains a lot, with little seasonal or day-to-day change. The subtropics, by contrast, are generally dry. If the warm, wet tropical climate is spreading poleward, the dry subtropic climate may head for the poles too.

This change may bring more storms to the temperate zone and drier weather to parts of the world that are already dry.

(Agencies)