I"m not too worried about China's economy losing some momentum, or even the economic, political and other brushfires in the emerging markets. At least not individually. But together, they are a pattern that is spooking the market, and nowhere does that fear become more manifest than in the price of "Doctor" copper.
They call this metal "Doctor Copper" because it takes the pulse and temperature of the global economy. Right now, Doctor Copper is a bit concerned. The real worry will set in if copper breaks its recent uptrend.