Global warming is causing destructive hurricanes to attain their peak strength and move farther away from Earth's equator with each passing year, a study by tropical weather researchers indicates.
This move toward the Earth's poles could be the first concrete evidence of a link between climate change caused by human activity -- the emission of greenhouse gases into the atmosphere -- and the behavior of hurricanes, the researchers say.
Analyzing where global tropical storms reached their peak strength from 1982 to 2012, weather scientists found the center of maximum strength in the Northern Hemisphere moved northward around 33 miles in each of the two decades, and the Southern Hemisphere saw a storm shift toward the South Pole of about 38 miles in each decade.
"The absolute value of the latitudes at which these storms reach their maximum intensity seems to be increasing over time, in most places," study co-author Kerry Emanuel of MIT says. "The trend is statistically significant at a pretty high level."
Major coastal regions in the mid-Atlantic and Northeastern U.S states could face significant impacts with the shift in storm strength locations in the Northern Hemisphere, the study authors warn, as any changes in the position where a storm makes landfall could have potentially profound impacts on property and life.
The two-decade analysis was deemed necessary because hurricane activity can vary significantly from year to year due to the complexity of the atmospheric cycles that drive them.
Human influences on climate change, and therefore on storms only become apparent over a few decades at least.
The Atlantic hurricane season of this year, beginning July 1, is predicted to be somewhat quiet, with AccuWeather forecasting four hurricanes and 10 named storms, as compared with previous years' average of six hurricanes and 12 named storms.
A developing El Niño condition and warm ocean temperatures in equatorial Pacific is expected to create wind shear in the tropical Atlantic hostile to hurricane development that should keep the numbers down, the forecasters said.
Still, the move toward the poles and a possible link with human activity needs additional long-term studies.
"Now that we see this clear trend, it is crucial that we understand what has caused it -- so we can understand what is likely to occur in the years and decades to come," says co-author Gabriel Vecchi, a scientist with the National Oceanographic and Atmospheric Administration.
The study was published in the journal Nature.