By Jeff Franks

NEW ORLEANS, April 6 (Reuters) - Natural changes in ocean currents are to blame for increased Atlantic hurricane activity in recent years, not man-made global warming as many scientists believe, hurricane forecaster William Gray said on Friday.

"I think the whole human-induced greenhouse gas thing is a red herring," Gray said in a speech at the National Hurricane Conference.

Gray, whose annual forecasts for the hurricane season are closely watched, said the Earth has warmed the past 30 years, but that it was due to flucuations in ocean currents. He predicted a cooling off period would begin in five to 10 years as the currents change again.

"I see climate change as due to the ocean circulation pattern. I see this as a major cause of climate change," Gray told the meteorologists and emergency management specialist who attend the annual conference.

The Atlantic had destructive hurricane seasons in 2004, when four major hurricanes struck Florida, and 2005 when Katrina and Rita badly damaged the U.S. Gulf Coast.

In 2005, there were a record 28 named storms and 15 hurricanes, but last year was much calmer with 10 tropical storms and five hurricanes.

This year, Gray's forecasting team is predicting an active season with 17 named storms, nine of which will become hurricanes.

Periods of intense Atlantic hurricane activity are not unusual and follow the change of a key Atlantic Ocean current that shifts every 30 years or so to bring warmer ocean waters that encourage hurricane formation, Gray said.

He said carbon dioxide levels in the Earth's atmosphere have increased, but periods of hurricane activity preceded the build-up of the gas, which is blamed for warming and is the byproduct mostly of fossil fuel burning.

The changing ocean current "goes back for hundreds of thousands of years," Gray said. "These are natural processes. We shouldn't blame them on humans and CO2."

Gray said the Atlantic current appears to change because of a rise and fall in water salinity.

The combative professor dismissed the work of scientific colleagues who have linked global warming and increased hurricane activity, saying they were simply seeking grant money.

"You've heard a lot of foolishness over the last few years," said Gray.

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