Tornadoes are touching down in clusters more often than 50 years ago, according to a new study, NBC News reported. On some days, the U.S. has seen more than 30 twisters. However, there are fewer days on which tornadoes occur, according to the study published Thursday in the journal Science. While it's clear that tornadoes are changing, there is no strong evidence that climate change is to blame, according to the study’s lead author.
