The effect could be enormous. If scientists now predict that the earth will warm less, and less quickly, than earlier thought — and also concede that the planet has not warmed at all in the last decade or so — the position of the environmental activists, and groups like Organizing for Action, will be significantly weaker. They’ll have a harder time arguing for drastic and immediate action.

The downgrading of the warming threat, writes the Journal, “points to the very real possibility that, over the next several generations, the overall effect of climate change will be positive for humankind and the planet.” It will be hard to argue for a doomsday scenario on the basis of that.

But after more than a decade of increasingly frantic predictions, the activists will not fold their tents and go home. “The climateers have been doing vigorous ‘battle space preparation’ ahead of the report,” says Steven Hayward, a conservative scholar who writes frequently about the politics and science of global warming. “They’re priming the media to say ‘we’re still doomed,’ even though the case for doom has been badly eroded over the last couple of years.”

Given how deeply the IPCC is invested in the issue — it shared the Nobel Peace Prize with Al Gore in 2007 — there’s little doubt the report will give environmental activists at least something to work with.