Bank of America's Michael Hartnett is back with another controversial note overnight, reminding readers that "it ain't a normal cycle" for one overarching reason: central banks.

As Hartnett explains, the catalyst for bull in equity and credit markets since 2009 was the "revolutionary monetary policy of central banks" who, since Lehman, "have cut rates 679 times and bought $14.2tn of financial assets." And, once again, he warns that this central bank “liquidity supernova” is coming to an end, as is "the period of excess returns in equities and corporate bonds, as is the period of suppressed volatility."

His best trade recommendation?

"Buy gold."