Report: Hurricanes’ Power Shifts to Poles
As the Earth’s oceans have warmed over the past three decades, the staging grounds for destructive hurricanes have crept toward the poles, according to a study by three of the world’s leading tropical weather experts. This could be the first “robust” signal that the buildup of greenhouse gases from human activity is influencing tropical storms, the authors said.
Identifying a firm connection between hurricane activity and man-made global warming has proven elusive. The 2013 Intergovernmental Panel on Climate Change report stated there was “low confidence” in any link between observed changes in tropical storms and human activity.
The new study, published online in the journal Nature on Wednesday, analyzed where tropical storms around the world reached peak intensity between 1982 and 2012. It found that the location of maximum storm strength leaped poleward about 33 miles per decade in the Northern Hemisphere and 38 miles per decade in the Southern Hemisphere.
“The absolute value of the latitudes at which these storms reach their maximum intensity seems to be increasing over time, in most places,” said Kerry Emanuel, a professor at the Massachusetts Institute of Technology and co-author of the paper. “The trend is statistically significant at a pretty high level.”
The authors — James Kossin of the National Oceanic and Atmospheric Administration, Emanuel and Gabriel Vecchi of NOAA — linked the storm shift to an expansion of the Hadley Cell, an atmospheric circulation pattern that transports heat from the tropics to the mid-latitudes and drives the easterly trade winds. In other words, the tropics are occupying a larger area. The expansion “is likely due largely to human influences” — the heating effect of increasing greenhouse gas concentrations, the study said.