California- This week, Congress held its first hearing on the landmark IPCC report on climate change. That report concluded that global warming is “unequivocal” and human activity is the main driver, “very likely” causing most of the rise in temperatures since 1950.

During the hearing, Rep. Dana Rohrabacher (R-CA) — one of the 87 percent of congressional Republicans who do not believe in man-made global warming — questioned the authors of the report about a period of dramatic climate change that occured 55 million years ago. “We don’t know what those other cycles were caused by in the past. Could be dinosaur flatulence, you know, or who knows?’

Presumably, Rohrabacher was referencing a period known as the Paleocene-Eocene Thermal Maximum. Then, as in now, “sharp rises in temperature were initiated and driven by large spikes in greenhouse gases. … It took over 100K years for the ocean, atmosphere, and temperatures to return to their previous state. The result was a mass extinction event that took millions of years to recover from.” But scientists believe that massive methane releases from the ocean floors — not dinosaur farts — were the cause.

In sharp contrast to Rohrabacher, Speaker Nancy Pelosi (D-CA) delivered an opening statement recommending mandatory caps on global warming pollution and calling out conservatives for rejecting science. “For twelve years, the leadership in the House of Representatives stifled all discussion and debate of global warming. That long rejection of reality is over, to the relief of Members on both sides of the aisle.”

ROHRBACHER: So, whether or not how dramatic this change will be, or is, what it’s caused by, are things that honest people, I think, can disagree with, and I really personally, having been a journalist, the first thing I was always cautioned by when someone was claiming, well, everybody is on my side, or everybody says this, or there is a total consensus, almost always when people said that to me over my years as a journalist, it wasn’t true. It was that there were honest people who disagreed and significant disagreement on such issues. We don’t know what those other cycles were caused by in the past. Could be dinosaur flatulence, you know, or who knows? We do know the CO2 in the past had its time when it was greater as well. And what happened when the CO2 was greater since then and now? There have been many cycles of up and down warming. So with that said, I think that we’ve had a great discussion today.