Jeremy Grantham, a famed investor with a track record of identifying market bubbles, said the downturn today is worse than the tech bubble of 2000, calling stocks to at least double their losses. "The other day, we were down about 19.9% on the S & P 500 and about 27% on the Nasdaq. I would say at a minimum, we are likely to do twice that," the co-founder of GMO told CNBC's Kelly Evans on " The Exchange " Wednesday. "If we are unlucky, which is quite possible, we would do three legs like that and it might take a couple of years as it did in the 2000s." Grantham is a widely followed investor and market historian, known for predicting the 2008 bear market and the burst of the dot-com bubble in 2000. He has been warning of extreme speculative activities in the market since the depth of the pandemic "This bubble superficially looks very much like 2000, focused on U.S. tech and led by the Nasdaq going to incredible highs," Grantham said. The technology sector has been at the epicenter of the market turmoil this year, especially hitting unprofitable firms and richly valued software names. The tech-heavy Nasdaq Composite is sinking deeper into a bear market in the face of rising rates, off about 29% from its all-time high. Still, the 83-year-old investor said there are some key differences to the two bubbles. In 2000, the sell-off was concentrated in U.S. stocks, while other assets like bonds, commodities and housing held up well, Grantham said. "We are really messing with all of the assets. This has turned out historically to be very dangerous," he said. "The combination of stocks and housing proved quite dangerous. We would have a severe recession." At the beginning of 2022, Grantham issued a dire warning , saying the end of "bubble extravaganza" was coming and called for stocks to drop 45%.