Over the past few years, there have been an unusually large number of tornadoes hitting the United States.

According to a new research study done at Florida State University, these tornadoes are one of the side effects of climate change, and as climate change continues, there will be an increasing frequency and intensity of tornadoes in the country.

The study was published in Climate Dynamics, written by Professor James Elsner. He said that there are fewer tornadoes forming than average, but the tornadoes that do form are increasingly strong and dense. This means that although there may be fewer individual days when tornadoes happen on average, when they do form there may be three or four tornadoes forming at once in an area, instead of one or two tornadoes in the past. In 1971, for example, there were 187 tornado days. In 2013 there were only 79 tornado days. Elsner says that because of this, many weather researchers ignored the effect global warming had on tornadoes.

However, Elsner was not convinced. He did a deeper examination of the data and found that although fewer tornado days were happening, each day had more intense weather.

"We may be less threatened by tornadoes on a day-to-day basis, but when they do come, they come like there's no tomorrow," Elsner said.

There is some good news: the area of the United States where tornadoes occur does not seem to be growing. However, the tornado season in those parts of the country are still deadly, and may be growing even more deadly as global warming continues to rack up the intensity of the storms. Elsner warns that scientists can no longer ignore the relation between global warming and tornadoes.

"I think it's important for forecasters and the public to know this," Elsner said. "It's a matter of making sure the public is aware that if there is a higher risk of a storm, there may actually be multiple storms in a day."

According to statistics from the NOAA, the 2011 tornado season had 550 fatalities. The number of tornado fatalities had been declining fairly steadily through the 1970s and 1980s as advances in tornado warning technology was developed, but there were several sharp increases in fatalities since the 2000s. This year so far there have been 43 tornado-related fatalities in the US.

The paper was cowritten with researcher Thomas H. Jagger, a former worker at Florida State University, and meteorologist Svetoslava Elsner.