Comedian Stephen Colbert hosted environmental activist Bill McKibben Tuesday evening to talk about his fight against the Keystone XL Pipeline.

McKibben expressed how Senate Republicans are trying to reviving the pipeline bill by placing it as an amendment in the Senate’s transportation bill. With that, McKibben mentioned how his site, 350.org, started another petition against the bill.

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“We launched a 24 hour drive to collect half a million message to the Senate,” McKibben. “In fact we blew by that half million by six hours.”

For McKibben’s efforts, Colbert labeled him “a troublemaker.”

WATCH: Video from Comedy Central, which was broadcast on February 13, 2012.