Powerful Hurricanes Most Dangerous Closer to Poles

A new study shows that powerful hurricanes have been migrating towards the north and south poles, now where they are most dangerous.

Over the last 30 years storms have been veering away from the tropics and further towards the north and south extremes, hinting that climate change may be affecting weather systems.

The report, published Wednesday in the journal Nature, says that these tropical cyclones - known as hurricanes or typhoons - are moving poleward at a rate of about 33 miles per decade in the Northern Hemisphere and 38 miles per decade in the Southern Hemisphere.

In order to track these storms' paths over recent years, researchers used international data from 1982 to 2012. They then marked the peak intensity of each of the storms in order to see whether the hurricanes were traveling further afield.

"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, an MIT professor, said in a news release. "The trend is statistically significant at a pretty high level."

While there are regional differences in the poleward movement of cyclones, the fact that every ocean basin other than the northern Indian Ocean has experienced these changes makes scientists believe that it is a global phenomenon.

"We think, but have not yet been able to establish, that this is connected to independently observed poleward expansion of the Hadley circulation," Emanuel said, referring to the large-scale pattern of global winds.

In recent years the Hadley circulation has moved more towards the Earth's poles. This has caused wind shear - which inhibits cyclone formation - to increase in the tropics and decrease in the polar regions. This means that it's more difficult to form cyclones, and so their incidence has diminished. However, their intensity may be increasing.