Tropical cyclones have been moving farther from the equator, which means they are shifting toward inland populations. Researchers from the National Oceanic and Atmospheric Administration (NOAA) led a study that found the maximum intensity of these tropical cyclones has been shifting poleward. Nature is expected to publish a study entitled The Poleward Migration of the Location of Tropical Cyclone Maximum Intensity this week.
When researchers discuss the maximum intensity of these cyclones moving toward the poles, they are essentially saying that they are moving away from the equator, even away from the tropics. This movement toward the inland coastal regions has been recognized and reported by scientists since 1980. The shift equates to 35 miles of movement into both the northern hemisphere and the southern hemisphere per decade.
It seems that regions closer to the equator may now be at reduced risk for these tropical cyclones, while infrastructure and populations in the more inland coastal regions are expected to be at a higher risk. Devastating results can take place for both regions. Regions in the tropics actually depend on rainfall from these tropical cyclones, to help replenish their water supply. The coastal cities and the areas more inland will now be subject to flooding, and high winds as the hurricane passes over the region; for which, they are not prepared to handle. Bill Rankin, a Yale University historian, is concerned that a larger number of people in the northern area will be in greater danger; thus, this shifting of typhoons toward the inland populations is of growing concern. This does not mean that there cannot or will not be severe tropical storms in what has always been known as the tropics, it appears that the trend of these storms are gravitating further from the equator and toward more coastal inland areas. All being subject to changing weather pattens.
There has not been any indication that the peak intensity of Atlantic tropical cyclones has shifted at all in the past 30 years. Only about 14 percent of the total number of tropical cyclones worldwide are located in the Atlantic. The Indo-Pacific region, however, has shown the greatest migration in the South Indian Oceans, as well as the northern and southern Pacific. Jim Kossin, a scientist with NOAA, has tremendous confidence in NOAA’s studies, as they have pinpointed the location where the hurricane reaches its maximum intensity, and can therefore be expected to give reliable results.
Another phenomenon which is being studied independently from the typhoons’ poleward migration is the rate at which the tropics are expanding, by definition away from the equator and toward the poles. Scientists are becoming more convinced that the two phenomena are connected. Although there are clear trends, studies to understand the cause will require deeper investigation. According to Kossin, speculation could be attributed to climate change, ozone depletion, particulate pollution, greenhouse gases, and all by-products of human activity, which means it could be a conglomeration of a bit of all of it. Another pertinent question to ask is if there is a primary factor.
Gabriel Vecchi, another scientist with NOAA, has said that it is NOAA’s mission to conserve and manage the coastal and marine sources through understanding changes in the Earth’s environment. To do so will require a comprehensive study from the depths of the ocean to the surface of the sun. Hugh Willoughby, another hurricane professor, feels that the most essential link has to do with global warming. Kerry Emanuel believes it is consistent with warming oceans. Regardless of what is causing these phenomena of the tropical expansion and migration of typhoons toward the poles, it is confirmed that these tropical cyclones are shifting toward the more populated, coastal inland areas.
By Jill Boyer-Adriance