Early tomorrow morning the IPCC will release its long-awaited, already-leaked, consensus-reaffirming report on climate change science. There will be a predictable frenzy of spin, and sniping, and grousing about how the media are handling the story, but the bottom line is going to be clear, which is that scientists are more certain than ever — with their conclusion now at the 95 percent confidence level — that human activity is the major cause of the global warming seen in the past century. Over at the AP, ace science writer Seth Borenstein has a smart piece explaining that 95 percent confidence is the gold standard for scientific research.

From Seth’s story:

“The president of the prestigious National Academy of Sciences, Ralph Cicerone, and more than a dozen other scientists contacted by the AP said the 95 percent certainty regarding climate change is most similar to the confidence scientists have in the decades’ worth of evidence that cigarettes are deadly.”

I don’t hear many people saying that cigarettes are benign. But we do still hear people deny that global warming is happening. Indeed the issue has gone in the past decade from being relatively non-ideological, with a growing bipartisan consensus that this was a real phenomenon (remember McCain campaigning for president in 2007 with a vow to do something about global warming), to one sharply polarized along partisan lines. This is a  case study in what Yale professor Dan Kahan calls “cultural cognition.”

The fact that the atmospheric warming has flattened out in recent years doesn’t negate the long-term trend, nor portend an era of global cooling. The cause of this “pause” in the atmospheric warming is unknown, and seems most likely to be a temporary phenomenon, since we keep pumping CO2 and other greenhouse gases into the atmosphere at a steady clip. One possibility is that the oceans are absorbing more of the heat than they have in the past, though that remains conjectural. At Wonkblog, my colleague Brad Plumer has a thoughtful discussion of the warming pause and explains why it’s not a reason for complacency. [Update: Here’s Brad’s preview of tomorrow’s report.]

Now, Oswald. Right, I put that in the headline — trying, devilishly, to snare innocent readers out there who type “global warming and Lee Harvey Oswald” into a search engine. But also, I read the excellent Ron Rosenbaum piece in Smithsonian on the Zapruder film. Ron works his way steadily into some heavy epistemological territory, discussing the resilience of conspiracy theories, the indestructibility of doubt, and what you might call the fog of reality. Errol Morris has a better metaphor for the theories about the JFK assassination: “The labyrinth to nowhere.”

“The implication is that all is uncertainty, that we’ll never know who killed Kennedy or why to any degree of certainty,” Rosenbaum writes.

(Actually, I’m in the “case closed” camp when it comes to who did it — Oswald. Somewhere at the bottom of a desk drawer I have some jibber-jabber I wrote on that back in the day. Oh, wait, here it is.)

Rosenbaum, in studying that Zapruder film, and its grisly and gut-wrenching Frame 313, touches on a basic fact about reality: It does not necessarily become clearer as you look closer. (To Rosenbaum’s eye, it appears that Kennedy was shot from the front — from the direction of the grassy knoll. But medical examiners who looked at the autopsy photos and X-rays concluded he was shot from the rear — from the direction of Oswald’s perch on the 6th floor at the Texas School Book  Depository.)

The elusive nature of reality is seen in climate science as well. The eternal quest for “consensus” isn’t really how science works, because scientists tend to be wary of absolutes and consider most knowledge to be provisional. We can be certain that we’ll always have to cope with some level of uncertainty. But that’s no reason to sit around in a befogged stupor, doing nothing.