“Tornadoes are currently on a frightening upswing.” That could have been written yesterday — but was written 12 years ago, by your columnist, in the November 8, 1999 issue of The New Republic.

The onslaught of tornadoes is not some sudden, unexpected bolt out of the blue. I wrote about tornadoes a dozen years ago because 1998 and 1999 were terrible years for tornadoes. Now three of the last 12 years have been terrible for tornadoes, and the 1950-2010 trend isn’t so great either.

This spring’s tornado activity has been awful. At least 116 people died in Joplin, Missouri, on Sunday during an unusually strong and large tornado. A portion of Tuscaloosa, Alabama was destroyed by a tornado last month. Many tornadoes hit the Ozarks region in April. There were 875 confirmed tornadoes in April, triple the previous April high of 267, in 1974. So far 481 Americans have been killed by tornadoes this spring.

In recent decades, the installation of a Doppler radar warning system in tornado-prone areas has tended to reduce fatalities — sirens get people’s attention. But even 24 minutes of warning, which Joplin received on Sunday, may not be sufficient for a tornado that was a hard-to-believe half a mile across. (The touch-down part of a tornado is rarely more than 100 yards wide.) More disturbing tornado facts are here.

Weather patterns include random variation: some recent years have been mild for tornadoes. Before this spring, the worst tornado sequence in U.S. annals came in 1953, when atmospheric greenhouse gas levels were lower than today. Nevertheless, there are reasons to think tornadoes are a harbinger of climate change.