As we mentioned a few days ago, although the argument that global warming is increasing the intensity of hurricanes is becoming more accepted, there's still a great deal of dispute over whether climate disruption is increasing the frequency of hurricanes. Human records aren't terribly helpful for more than a couple of hundred years at most, and hurricanes don't leave permanent and identifiable marks on the environment... or do they?

University of Tennessee, Knoxville researcher Claudia Mora and her team think they've found the key to unlocking a record of past hurricanes. It turns out that hurricanes have a strong tendency to deplete the air of Oxygen-18 (or 18O), a rare isotope of Oxygen. The rain that falls from hurricanes has measurably less 18O in the water; this is "recorded" in the rings of late-season-growth trees such as Georgia Pines. By measuring the 18O in the tree rings, Mora and team were able to positively identify every hurricane that hit the region over the past century, and have mapped out a tropical cyclone record going back 277 years. They claim to have spottier information going back to 1450 AD.

More details on this research will be released tomorrow at the Earth System Processes 2 conference in Alberta, Canada.