Vermont's own globetrotting, carbon-fighting climate activist Bill McKibben cropped up on national television again last night, this time in a repeat visit to the Colbert Report. By way of snappy introduction, Colbert — eyes gleaming gleefully — had this to say of his visitor: "My guest Bill McKibben believes in global warming... so I'm going to deny that he exists."

McKibben was talking up the latest effort by 350.org and a coalition of environmental advocates to block the controversial Keystone XL pipeline. He's has been making headlines in his crusade to stop the proposed pipeline, which would carry oil from Canadian tar sands to Gulf of Mexico refineries. In August, McKibben was arrested in front of the White House at the beginning of a massive series of civil-disobedience protests undertaken by the environmental movement. The two-week sit-in led to the arrests of 1253 protestors and ended in what environmentalists considered a victory: In January the Obama administration denied a permit for the project.

Then, yesterday, came this bad news: On Monday afternoon, Senate Republicans filed an amendment to the transportation bill that would authorize the Keystone XL pipeline. Once again, environmentalists rallied in opposition to the project, which has inspired what some observers call a "too rare unity" in the movement. They set a goal to gather 500,000 signatures on an anti-pipeline petition in 24 hours — then blew that goal out of the water in seven hours instead.

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Colbert, in usual fashion, wrung his hands over McKibben's environmentalist agenda — and McKibben took the ribbing gracefully, cracking a smile when Colbert, eyebrows waggling, explained earnestly, "Everything we're extracting from the ground is natural, right? It's all natural. That oil is 100 percent certified organic."

At the end of the nearly five-minute spot, Colbert grudgingly asked where the loyal Colbert Nation might foolishly sign the anti-Keystone petition, then eyed the camera. Wagging a finger at viewers at home, Colbert sternly admonished: "Do. Not. Do. It."

The petition is still live at 350.org.

Image courtesy Wikipedia.