Tropical cyclones moving poleward

Tropical cyclones are reaching maximum intensity farther from the equator and closer to the poles, according to a study published in the journal Nature on Wednesday. Over the last 30 years, the peak of these powerful and destructive storms has migrated poleward at the rate of about half a degree of latitude -- some 56 kilometres (35 miles) -- per decade, they said. The shift is highest in the northern and southern Pacific and southern Indian Ocean. There was no evidence of a shift in North Atlantic hurricanes or northern Indian Ocean cyclones, nor of any change in the global frequency of these storms, the researchers found. The implications are far-reaching, according to the paper. It means that regions that were once considered to be relatively cyclone-safe may become more exposed. Regions closer to the equator, though, may run less risk of being hit -- but could experience water stress where they depend on rainfall from these storm systems. "Any related changes to positions where storms make landfall will have obvious effects on coastal residents and infrastructure," said the paper. The evidence comes from data collected from 1982 to 2012 by the United States' National Oceanic and Atmospheric Administration (NOAA). The scientists used as their benchmark the location for each storm's peak intensity, rather than its starting point or duration, which can be hard to establish accurately. The shift coincides with a period when global warming stepped up a gear and Earth's tropical belt, whose warm seas fuel hurricanes and typhoons, expanded. "As that belt migrates poleward, which surely it must as the whole ocean warms, the tropical cyclone genesis regions might just move with it," said Kerry Emmanuel, a professor at the Massachusetts Institute of Technology (MIT) who co-authored the paper. "But we have more work to do to nail it down."