Records show the AMO was cool from 1900-1925, warm from 1926-1969, cool from 1970-1994 and warm since 1995.
Climatologists look at those dates and realize a generation of Americans is virtually blind to the true threat of hurricanes, having never experienced a major hurricane firsthand, at least until last year's four Florida hurricanes.
"During the time when so few hurricanes hit North America, we as a society framed decisions about land use, construction standards and other aspects of our lives around the shores of the Atlantic Ocean and Gulf of Mexico," wrote FIU's Willoughby last fall. "Built into those plans was the unstated assumption that hurricanes would continue to stay away from our shores as they had for the last third of a century."
Another expert said the hurricane seasons of the 1940s, in the heart of the last AMO warm phase, would stun today's Floridians.
"Imagine variations of 2004 occurring every year for 10 years," said Roger Pielke Jr., a University of Colorado professor who studies risk and has written a book about hurricanes.
Moreover, some researchers say records for the 1940s and earlier may undercount that era's storms because reconnaissance flights and hovering satellites still were in their infancies.
"We don't know what was going on out in the middle of the ocean," Willoughby said.