Jeremy Grantham says this may be the 4th major market bubble of his career

Renowned investment manager Jeremy Grantham poses on a balcony at his Rowes Wharf office in Boston.
Lane Turner | The Boston Globe via Getty Images

Investor Jeremy Grantham is growing more and more sure that the U.S. stock market's rebound amid the coronavirus pandemic is forming a bubble that is ignoring reality and will end up hurting many people.

 "My confidence is rising quite rapidly that this is the fourth 'Real McCoys' bubble of my investment career," Grantham, co-founder of GMO, told CNBC's Wilfred Frost on Wednesday in an interview which aired on "Closing Bell." "The great bubbles can go on for a long time and inflict a lot of pain."

The previous three bubbles Grantham referred to were Japan in 1989, the tech bubble in 2000 and the housing crisis of 2008.