NEW YORK (AP) — Europe’s economy sputters, oil prices plunge and stocks start swinging wildly. Wall Street’s long dormant “fear index” now predicts more turbulence ahead.

The Chicago Board Options Exchange’s volatility index, known as the VIX, doubled over the past month: from 12 to 26. Although that’s nowhere near the 80 reached in the financial crisis, the recent spike means traders are bracing for more big jumps and steep drops.