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The strength of a tornado has a significantly larger effect than population on the number of casualties, according to new research from Florida State University.

The study, recently published in the journal Geophysical Research Letters, examined all tornado casualties – death or injury as a direct result of a tornado – in the Lower 48 states from 2007 to 2015.

“We brought in external data and estimated tornado energy based on tornado area, median wind speeds and the magnitude of those storms,” said lead author Tyler Fricker, a doctoral student in the FSU Department of Geography.

(MORE: Your Odds of Being Hit by a Tornado)

Researchers used a regression model and found that doubling the energy dispersed by a tornado yields a 33 percent increase in the casualty rate, while doubling the population in a tornado's path only increases the casualty rate by 21 percent.

“It’s somewhat surprising because we’re led to believe it’s just a problem with exposure – the more people in the way, the more casualties,” said James Elsner, chair of the FSU Department of Geography and co-author of the study.

The research team also concluded that population density within a tornado's path typically decreases with stronger twisters. This inverse relationship is likely the case because the stronger the tornado, the larger its area, which increases the likelihood of it passing through lower-population areas.

Additionally, the strongest tornadoes with the potential for producing widespread damage tend to occur in areas where population density is lower, such as the Plains and Midwest regions.

(MORE: Your Average Tornado Risk By Month)

The team recognizes that climate change may potentially impact future storms. Elsner believes global warming could lead to fewer storms, but when they do form, they could be much stronger.

“It’s not just about human activity and the exposure problem,” Elsner said. “It’s also about the problem that these storms might change in the future. Through this research, we’ll have some way of understanding if they do change, how many more casualties we can expect.”

The chance of being killed by a tornado today is less than it was 30 years ago, Elsner added. This is largely due to more lead time, better National Weather Service warnings and increased awareness of the threat.

Nevertheless, Fricker plans on conducting further research to identify which parts of the United States can expect higher rates of casualties.

“If we can identify certain areas that are more susceptible to casualties, the next step is to think about what’s actually happening at the surface,” Fricker said. “What are the socio-economic and demographic variables that are present in those areas that are affecting tornado casualties?”

Poverty levels, education levels and even race could be used to determine the number of casualties, according to the study.

“We want to try to understand this,” Elsner said. “I think the National Weather Service does a great job in warning people, but perhaps some people need to be warned a different way, at a different time of day. There are different ways to communicate the threat. In the future, I think the weather service will able to use that information to pinpoint their watches and warnings even better.”

(MORE: The History of 'High Risk' Severe Weather Outlooks)

In the meantime, you should have a dependable method of getting severe weather watches and warnings, whether through local media, NOAA weather radio, social media or a smartphone or tablet app. If using an app, make sure your phone and app settings are such that you can be awakened from a sound sleep.

Know where to take shelter if a warning is issued. If you live in a mobile home, find out if your mobile home park has a safe shelter underground, or find somewhere else where you can take shelter ahead of time.

Brian Donegan is a digital meteorologist at weather.com. Follow him on Facebook and Twitter.

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