Tropical storms, usually found near the equator, may be moving toward the poles, new research shows. This trend could bring damaging storms to temperate regions. Many of these areas are poorly-prepared to deal with these storms, some of which can be severe.
Storms have been drifting toward the poles in the last three decades, damaging regions well away from where they formed.
The National Oceanic and Atmospheric Administration (NOAA) led an investigation of how the paths of tropical storms may migrate over time. Researchers discovered storms are reaching peak strengths an average of 35 miles (one-half a degree) further away from the equator every 10 years. This change in latitude is consistent in both the northern and southern hemispheres.
"The poleward trends are evident in the global historical data in both the Northern and the Southern hemispheres, with rates of [33 and 39 miles] per decade, respectively, and are statistically significant. When considered together, the trends in each hemisphere depict a global-average migration of tropical cyclone activity away from the tropics at a rate of about one degree of latitude per decade," researchers wrote in the article announcing their findings.
Jim Kossin, a NOAA scientists assigned to the University of Wisconsin-Madison directed the investigation. The data suggests that as storms become more severe and dangerous in temperate regions, the storms may become less common in the tropics.
"We've identified changes in the environment in which the deep tropics have become more hostile to the formation and intensification of tropical cyclones and the higher latitudes have become less hostile," Kossin reported in a press release. "'This seems to be driving the poleward migration' of storm intensity."
The trend was more pronounced in the Pacific than in the Atlantic. Kossin believes this may be due to additional forces at work in the Atlantic, mitigating the global trend away from the equator. These include ocean currents that could affect storms, as well as reduced levels of aerosol emissions in that region. Tropical storms in the Atlantic only account for about 14 percent of the total number of such events worldwide.
Investigators believe global warming may be partly to blame for the change in course for the storms. Increasing temperatures, they theorize, may be expanding tropical regions.
In addition to climate change, this expansion of tropical regions may be caused particulates in the air and depletion of stratospheric ozone. Both of these effects are due to human actions.
Study of the movement of tropical storms was detailed in the journal Nature.
