The location where a tropical storm reaches it’s maximum intensity has been shifting toward the poles in both the northern and southern hemispheres over the past 30 years, according to a new study to be published in Nature.

The exception to that appears to be Atlantic Ocean storms, which includes tropical storms that make it to Louisiana, according to a news release from the National Oceanic and Atmospheric Administration.

According to researchers with NOAA, the location of the maximum intensity has moved toward the poles at about 35 miles per decade. The rate is not consistent around the world with the greatest rates found in the northern and southern Pacific and South Indian Oceans.

However, there’s no evidence that Atlantic Ocean storms have experienced similar migration, NOAA researchers said.

“Historical intensity estimates can be very inconsistent over time, but the location where a tropical cyclone reaches its maximum intensity is a more reliable value and less likely to be influenced by data discrepancies or uncertainties,” Jim Kossin, the paper’s lead author, said.

Kossin is a scientist with NOAA’s National Climatic Data Center stationed at the NOAA Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin, Madison.

The cause of this shift isn’t known, but it is occurring over the same time that scientists are seeing an expansion of the tropics, attributed in part to increases in greenhouse gases and air pollution. However, it will take more research to determine a cause in the tropical storm intensity shift.

“Now that we see this clear trend, it is crucial that we understand what has caused it — so we can understand what is likely to occur in the years and decades to come,” Gabriel Vecchi, scientist at NOAA’s Geophysical Fluid Dynamics Laboratory and coauthor of the study, said.