Editor’s Note: Each week we cross-post an excerpt from Katrina vanden Heuvel’s column at the WashingtonPost.com. Read the full text of Katrina’s column here.

In April 2009, as the political right was finding its voice in the tea party, South Carolina Republican Rep. Bob Inglis was making the case for a carbon tax. “I’m a conservative. I believe in accountability,” he said. “Global warming is not a matter of belief. It’s a matter of facts.” He added, “We don’t want to be a party of deniers.”

Most of his party disagreed. A year later, Inglis was trounced in a Republican primary, his staunchly conservative record proving insufficient to overcome this heretical deviation. On the surface, it may appear that little has changed in the intervening years. But cracks are appearing in the climate change deniers’ defenses. Today, the movement to seriously address global warming is gaining unlikely supporters, a potential preview of the tectonic shift to come.

Last month, six major oil and gas companies based in Europe, including BP and Royal Dutch Shell, wrote a letter officially endorsing an international price on carbon. “Climate change is a critical challenge for our world,” they declared. “The challenge is how to meet greater energy demand with less [carbon dioxide]. We stand ready to play our part.” In the short term, these companies stand to benefit from carbon pricing, which would shift demand away from coal. But even if their position is partially self-serving, it’s an important declaration, and one that deeply undercuts the climate change deniers’ arguments. Even oil companies, we can now say, believe climate change is real—and admit it’s something they are causing.

Read the full text of Katrina’s column here.