Global warming may be pushing the jet streams toward the Earth's poles, widening the area where hurricanes may form, scientists at the Carnegie Institution's Department for Global Ecology found.

A study of the high altitude, high-speed winds from 1979 to 2001 found that their positions are changing over time, with the potential to affect weather for half the globe, the Stanford, California-based department said in a statement. The study will be published tomorrow in Geophysical Research Letters, the journal of the Washington-based American Geophysical Union.

Jet streams are migrating poleward at 19 kilometers (12 miles) a decade in the Northern Hemisphere, the researchers found. Because the winds inhibit storm formation, their movement away from the sub-tropical zones where hurricanes are typically born may result in more frequent and more powerful storm systems, according to the researchers.

"At this point we can't say for sure that this is the result of global warming, but I think it is,'' Ken Caldeira, a co-author of the study, said in the statement, dated yesterday. "I would bet that the trend in the jet streams' positions will continue. It is something I'd put my money on.''