More signs that the movement to stop global warming has run out of gas emerged yesterday as Bill McKibben, the 350.org founder and Keystone XL pipeline opponent, announced that he was hanging up his hat.

The surprise retirement capped a hectic week for the environmental movement, during which one leader after another declared they were giving up on the cause.

“I’m bone-tired and written out. It’s time for the planet to take care of itself,” McKibben told a crowd of supporters who were sweating in the freakish early-spring heat wave that has rolled across much of the U.S. “I’m going skiing. Uh, make that water-skiing.”

As he spoke, volunteers were shutting down the offices at 350.org, filling a giant dumpster in the street outside. “It was a good fight,” one recent Middlebury College graduate said. “But we lost, and now we’re just giving up.”

On Monday, food-movement leader Michael Pollan caused a stir by unveiling a radically new formulation of his famous seven-word “Food Rules.” The new version? “Eat everything. Wherever it’s from. Pack Tums.” Pollan was later spotted at a McDonald’s near his Berkeley home, dipping Chicken McNuggets in Creamy Ranch sauce.

Tuesday, Al Gore abandoned a lifetime of climate-change activism as he assumed a new position as global chairman of BP. “Sometimes you just have to go with your gut,” the vice president explained in an interview on Fox. Did the move mean Gore aimed to reduce carbon emissions by working inside the system? “No,” he answered. “It’s really just a sell-out.”

Actor Mark Ruffalo announced Wednesday he’s ending his long fight against fracking in the Delaware River Valley to focus on his film career. “Look, The Avengers is coming out in a few months, I play the Hulk, I have my own action figure,” he said. “Upstate New York is fine for ‘critical favorites’ and ‘art-house darlings,’ but I’ve finally made the big time. I’ll probably move to Brentwood or somewhere else where I don’t have to worry about my water catching on fire.” Ruffalo urged Delaware River Valley residents to “stay strong” and “keep up the fight” to keep fracking out of the Marcellus Shale.

Naomi Klein, the progressive journalist who spent the past year covering Occupy Wall Street and crusading against business rapacity, announced Thursday that she was joining Goldman Sachs as a senior director. “Corporations are people, too,” she explained to a reporter, before disappearing into a black limousine.

Meanwhile, Rachel Maddow vanished mysteriously from her scheduled book-tour appearances last week. After repeated no-shows for public events, her office would offer no explanation, meeting all questions with the same response: “That’s classified.” One MSNBC colleague said she’d heard Maddow had turned in her resignation to take a new job as spokesperson for Academi, the private-security service formerly known as Xe formerly known as Blackwater. But this report remains unconfirmed.

Van Jones, the green-jobs activist who was hounded out of his White House job in 2009 by the right, used a promotional event for his new book outside of a shuttered Solyndra plant in Fremont, Calif., to announce his new gig: partnering with Republican guru Karl Rove in a new firm, Rove and Jones, offering campaign consulting services for conservative candidates who want to reach communities of color.

At the conservative Heartland Institute, long known for its climate-denialism, a spokesman said, “We don’t know what the hell is going on, but whatever it is, we’re quite certain that human activities are not responsible.”