What’s behind the shameless demagoguery and character assassination being heaped on climate change “deniers”? What’s behind the chilling calls for “Nuremberg trials” for dissenting scientists? Why has the green rhetoric escalated to lynch-mob proportions?

“A certain shock treatment is needed,” says James Hansen, head of NASA’s Goddard Institute for Space Studies, to the New York Review of Books, “but it would best be delivered with a two-by-four as a solid whack to the head of politicians who remain oblivious to fundamental physical facts.”

British writer George Monbiot is even more severe. “[E]very time someone dies as a result of floods in Bangladesh, an airline executive should be dragged out of his office and drowned.”

History is repetitious. Most of the people being shouted down aren’t even guilty as charged. Almost every scientist I know will tell you that the planet is warmer than it was, and that the burning of fossil fuel has certainly contributed to the warming of recent decades.

The science is pretty simple. For a variety of physical reasons, increased atmospheric carbon dioxide should disproportionately warm the winter (which it has), as well as continental regions in the mid-to-high latitudes (which it has, with the exception of Antarctica), and cool the global stratosphere (which it has). Hard to deny.

What’s bugging the mob isn’t “denial” at all — that’s just a catchy label designed for maximum smear impact — it’s the implications of what has been observed.

It’s easy to show that the warming of the last three decades presages a very modest warming for the technologically foreseeable future, and that no policy will do anything to alter the warming trajectory we are on enough to measure its effect in a lifetime.

Billions of taxpayer dollars have been spent developing a host of computer models to study how climate changes as carbon dioxide concentrations increase. The problem is, not surprisingly, that different models produce different rates of warming. But, in ensemble, the models have an interesting behavior: they indicate that once human warming is established by increasing greenhouse gases, the warming tends to take place at a constant rate.

As there is a “wisdom of crowds,” there is also a “wisdom of models.” It’s been known for years that a collection of weather forecasting models tends to do better over time than any individual model. The same should apply to climate models, and to their collective behavior, which is a constant-rate warming.

So all one has to do is establish a greenhouse warming, and then demonstrate that indeed it has been constant since it started in the mid-1970s (which it has been, at 0.18 degrees Centigrade per decade), and you know the rate of future warming. Unless, of course, all that modeling work is just dead wrong. And that’s the truth that has people so exercised.

In fact, the merging of observed and modeled warming forces the conclusion that 21st-century warming will be near the low end of a much larger range (from 1.4 to 5.8 degrees Centigrade) projected by the United Nations in its 2001 compendium on climate change.

Then there’s the problem of what to “do” about this warming. In fact, we have been “doing” something all along: adapting to it. Consider what’s going on in North American cities. They warm up, with or without global warming, thanks to all their concrete and blacktop. As cities have warmed in recent decades, heat-related mortality has dropped significantly. Why? Because heat waves became common, and people learned how to live with them. Our hottest cities have the lowest numbers of heat-related deaths. The only major city in which they are increasing is chilly Seattle, and, as it continues to warm, mortality will drop.

Aren’t we just moving heat-related death to more northern cities with global warming? No. The world tends to run out of cities north of 60 degrees of latitude. It’s not an accident that almost all of Canada’s population lives within 100 miles of the U.S. border.

For the sake of argument, though, assume that all the urban warming resulted from greenhouse-gas changes. What could have been done about it? The answer is simple: nothing. There are no known technologies that would have significantly altered their temperature trajectories.

Nor will such technology exist for the foreseeable future. Sure, governments can “encourage” us to buy hybrid cars. But the beaters we trade in simply move down the economic chain. Net emissions rise.

There also isn’t any viable legal instrument that will significantly alter the rate of warming. The Kyoto Protocol, which is pretty much moribund, would reduce surface warming by 0.07 degrees Centigrade every fifty years, an amount too small to measure. Kyoto failed because, by and large, no nation could meet its modest emission reduction targets.

That’s what’s being denied by those who call everyone they disagree with “deniers.” Here are the hard facts: Unless you stipulate that the behavior of all those climate models is wrong, you are forced to conclude that future warming will be modest and there really isn’t anything you can do about it. Anyone who refuses to acknowledge this is in denial, which, of course, explains the frustration and hyperbole of the mob, now calling for assault and murder.

Where, incidentally, is the outrage?