"If there's anybody in this whole business who calls a spade a spade, everyone would say that person is Jeremy Grantham," says John Bogle, an investing legend and the founder of mutual-fund giant the Vanguard Group. "He pulls no punches and is one of the top two or three individuals in this business. He's a straight shooter in a business where that's not a customary characteristic."

It's not cheap to profit from Grantham's market wisdom, unfortunately: The price of poker to be a GMO client, most of which are institutions, is a minimum $10 million. But for the rest of us, GMO also
subadvises a number of mutual funds available to the general public through Evergreen Investments, John Hancock Funds, and the Vanguard Group.

Grantham isn't just a market geek, though the messy stacks of data on his desk might give that impression. He also has some amusing personal quirks, like his obsession with textiles (he collects everything from old Uzbek bridal embroideries to ­fifteenth-century swaths of Venetian velvet).

But if there's one thing he's dead serious about, it's the world's casual ignorance of coming environmental crises. Much like his approach to the markets, he's peering long-term at what's heading down the pike, and he doesn't necessarily like what he sees. Grantham, who has started a foundation for environmental protection with his wife, Hannelore, isn't sure enough people are paying attention.

"It just seems obvious to me," he says. "This is where we live, so why mess it up? We're the richest society ever, so we need a version of the Manhattan Project to protect the environment. What we're facing is serious - and irreversible."

Playing Defense: Surviving and Thriving in a Downturn