Scientists from Massachusetts Institute of Technology used data collected by the US National Oceanic and Atmospheric Administration to chart the peak intensity of tropical storms between 1982 and 2012. They found that in the Northern Hemisphere, the storms are moving polewards at a rate of 53 kilometres per decade, and in the Southern Hemisphere, at a rate of 61 kilometres per decade.
‘The absolute value of the latitudes at which these storms reach their maximum intensity seems to be increasing over time, in most places,’ said one of the study’s authors, Kerry Emanuel. ‘The trend is statistically significant at a pretty high level.’
The study’s results also appeared to be consistent with a warming climate, he said. ‘It may mean that the thermodynamically favourable conditions for these storms are migrating poleward.’
According to Emanuel, ocean temperatures of 28–30°C are ‘ideal for the genesis of tropical cyclones and as that belt migrates poleward, which surely it must as the whole ocean warms, the tropical cyclone genesis regions might just move with it. ’
The study found regional differences in the amount of movement of cyclones, but because every ocean basin other than the northern Indian Ocean has experienced the change. the researchers suggest that this ‘migration away from the tropics is a global phenomenon’.
This story was published in the July 2014 edition of Geographical Magazine