The Silver Lining of Disaster

There aren’t many reasons to consider a volcanic eruption a positive event, but if results from recent research by Amato Evan of the University of Virginia are confirmed, residents of hurricane-prone areas, at least, may have a new reason to welcome volcanoes. Evan studied the effects of two major volcanic events–the 1982 discharge of El Chichón and Mount Pinatubo’s eruption in 1991–on Atlantic hurricane activity. He found that hurricane frequency and intensity both decreased by about 50% in the year following the eruptions, as compared to the year preceding the eruptions. Smaller decreases were still detected two and three years after the eruptions.
The finding is not entirely surprising. Major volcanic eruptions can expel large amounts of sulfur dioxide into the stratosphere; the gas then reacts with water to form sulfuric acid aerosols, which reflect light and absorb radiation, cooling tropical ocean waters while warming the lower stratosphere. The combination of these changes would be expected to dampen the frequency, duration, and power of hurricanes, which thrive on the temperature contrast between the sea surface and the atmosphere high above.
Evan’s study (subscription only) runs into complications that will need to be addressed before the volcano-hurricane link is accepted. For instance, both the El Chichón and Mount Pinatubo eruptions were also followed by strong El Niño events, which by themselves are expected to suppress hurricane activity. (On the other hand, some research suggests that El Niños can be caused by volcanic eruptions.) Further study of the dynamics in play is necessary.
Convincing people on the coasts that hurricanes themselves are a positive force in their lives may be a bit more difficult. At the annual Governor’s Hurricane Conference in Florida last week, however, attendees looked back at the 20-year legacy of 1992’s Hurricane Andrew with mixed feelings. While it is still the costliest disaster in the state’s history, the storm brought about many significant positive changes. For one, the state government revised emergency management funding so that each county could have a full-time emergency manager on staff. The institutionalization of emergency plans and outreach to residents has paid off repeatedly in subsequent hurricanes. Hurricane Andrew also led to stiffer enforcement of building codes and rethinking of the ways buildings must withstand high winds.
All in all, the silver lining of disaster isn’t great consolation, but the conference, like Evan’s research, gives hope for continued improvement in hurricane forecasting, preparedness, and response.