A NOAA-led study finds that over the past 30 years, the location where tropical cyclones reach maximum intensity has been shifting toward the poles in both the northern and southern hemispheres at a rate of about 35 miles, or one-half degree of latitude, per decade.
According to the study—published recently in the journalNature—the amount of poleward migration varies by region. The greatest migration is found in the northern and southern Pacific and South Indian Oceans; there is no evidence that the peak intensity of Atlantic hurricanes has migrated poleward in the past 30 years.
Many other studies are showing an expansion of the tropics over the same period. The expansion of the tropics has been observed independently from the poleward migration of tropical cyclones, but both phenomena show similar variability and trends, strengthening the idea that the two phenomena are linked. Scientists have attributed the expansion of the tropics in part to human-caused increases of greenhouse gases, stratospheric ozonedepletion, and increases in atmospheric pollution. However, determining whether the poleward shift of tropical cyclone maximum intensity can be linked to human activity will require more and longer-term investigations.
As tropical cyclones move into higher latitudes, some regions closer to the equator may experience reduced risk, while coastal populations and infrastructure poleward of the tropics may experience increased risk. With their devastating winds and flooding, tropical cyclones can especially endanger coastal cities not adequately prepared for them. Additionally, regions in the tropics that depend on cyclones' rainfall to help replenish water resources may be at risk for lower water availability as the storms migrate away from them.