The rush to "save the planet" cannot accommodate any doubt, or it loses the panicked momentum necessary for a retooling of modern economic life.

Climate alarmists conjured a world where nothing was certain but death, taxes and catastrophic global warming. They used this presumed scientific certainty as a bludgeon against the skeptics they deemed "deniers," a word meant to have the noxious whiff of Holocaust denial.

All in the cause of hustling the world into a grand carbon-rationing scheme. Any questions about the evidence for the cataclysmic projections, any concerns about the costs and benefits were trumped by that fearsome scientific "consensus," which had "settled" the important questions.

A funny thing happened to this "consensus" on the way to its inevitable triumph, though. Its propagators have been forced to admit fallibility. For the cause of genuine science, this is a small step forward; for the cause of climate alarmism, it's a giant leap backward. The rush to "save the planet" cannot accommodate any doubt, or it loses the panicked momentum necessary for a retooling of modern economic life.

Phil Jones is the director of the Climate Research Unit at the University of East Anglia, a key "consensus" institution that has recently been caught up in an e-mail scandal revealing a mind-set of global-warming advocacy rather than dispassionate inquiry. Asked by the BBC what it means when scientists say "the debate on climate change is over," the keeper of the flame sounded chastened. "I don't believe the vast majority of climate scientists think this," Jones said. "This is not my view. There is still much that needs to be undertaken to reduce uncertainties, not just for the future, but for the ... past as well."

Jones discussed the highly contentious "medieval warming period." If global temperatures were warmer than today back in 800-1300 A.D. — about a thousand years before Henry Ford's assembly lines began spitting out automobiles — it suggests that natural factors have a large hand in climate change, a concession that climate alarmists are loath to make. Jones said we don't know if the warming in this period was global in extent since paleoclimatic records are sketchy. If it was, and if temperatures were higher than now, "then obviously the late 20th century warmth would not be unprecedented."

Jones also noted that there hasn't been statistically significant warming since 1995, although the cooling since 2002 hasn't been statistically significant either.

All of this is like a cardinal of the Catholic Church saying the evidence for apostolic succession is still open to debate.

The other main organ of the climate "consensus" is the U.N.'s Intergovernmental Panel on Climate Change. It won the Nobel Peace Prize for its 2007 report, which turns out to have been so riddled with errors it could have been researched on Wikipedia. It said Himalayan glaciers would melt by 2035, warned that global warming could reduce crop yields in Africa by 50 percent by 2020, and linked warming to the increased economic cost of natural disasters — all nonsense.

These aren't random errors. As former head of the IPCC, the British scientist Robert Watson notes, "The mistakes all appear to have gone in the direction of making it seem like climate change is more serious by overstating the impact."

Too many of the creators and guardians of the "consensus" desperately wanted to believe in it. As self-proclaimed defenders of science, they should have brushed up on their Enlightenment. "Doubt is not a pleasant mental state," said Voltaire, "but certainty is a ridiculous one." The latest revelations don't disprove the warming of the 20th century or mean that carbon emissions played no role. But by highlighting the uncertainty of the paleoclimatic data and the models on which alarmism has been built, they constitute a shattering blow to the case for radical, immediate action.

In The Boston Globe, MIT climate scientist Kerry Emanuel marshals a new argument for fighting warming: "We do not have the luxury of waiting for scientific certainty, which will never come." Really? That's not what we were told even a few months ago — before climate-alarmism acknowledged doubt.

Rich Lowry can be reached via e-mail: