The surge in tornado frequency and severity in recent years should be a “wake-up call” that storm patterns may be returning to historic levels, said Lou Gritzo of insurer FM Global. “If you look back to the 70s and even to the 50s, you see a number of events that were significantly greater,” Gritzo, FM Global’s manager of research, said today at an insurance conference sponsored by Advisen Ltd. in New York. “The return to normal in terms of events should really be a wake-up call.”