Environment

A new study looks at clusters of tornadoes, like those that hit the Southeast this week. They are costly in lives and insurance payouts.

Climate scientists say the conditions that might produce more or stronger tornadoes are spreading along with a warmer atmosphere. But there's no sign so far that this is happening. New research finds that when tornadoes occur in clusters, as they often do, those clusters contain more tornadoes than ever. And we're also seeing more clusters with especially powerful tornadoes.