Mohamed El-Erian on why he thinks the market mood has changed

"What we're seeing is something very simple: the market mood has changed," Mohamed El-Erian, economic advisor at Allianz and Gramercy and president at Queens College, Cambridge, told CNBC's "Squawk Box" Monday. "It's no longer whether yields are going higher, but when is the move too big? That's what the market is trying to figure out."