The quarterly study’s authors, Aaron M. McCright of Michigan State University and Riley E. Dunlap of Oklahoma State, suggested climate had joined abortion and other explosive, intractable issues as a mainstay of America’s hardening left-right gap.

“The culture wars have thus taken on a new dimension,” they wrote.

Al Gore, for one, remains upbeat. The former vice president and Nobel Prize-winning climate campaigner says “ferocity” in defense of false beliefs often increases “as the evidence proving them false builds.”

In an AP interview, he pointed to tipping points in recent history — the collapse of the Berlin Wall, the dismantling of U.S. racial segregation — when the potential for change built slowly in the background, until a critical mass was reached.

“This is building toward a point where the falsehoods of climate denial will be unacceptable as a basis for policy much longer,” Gore said. “As Dr. Martin Luther King Jr. said, ‘How long? Not long.'”