The more general form of this question has bedeviled us for the better part of the last century: how do laymen (and policy makers) evaluate technical scientific problems? In the case of global warming, the relevant experts are mostly a small group of environmental and atmospheric scientists, and by now they pretty unanimously believe that global warming is real and that it is at least partly the result of human activity. So how do you argue with that? There are two possibilities:

  • On scientific grounds. Unfortunately, this is nearly impossible for a layman, and there are virtually no scientists left in the relevant disciplines who believe the opposite side anymore.

  • On non-scientific grounds. That is, the scientists are exaggerating or lying for some political reason.

Earlier this week Jonah Goldberg of NRO made a valiant attempt at the latter. In an argument more commonly associated with academic postmodernists, he contends that environmental scientists are little more than a teenage social group, and in order to be part of the clique they have to toe the line on global warming:

Robert Nisbet writes that more scientists probably have been stopped from pursuing research because “of defiance of conventional wisdom in America since World War II with its accompanying bureaucratization and politicization of science than existed in the whole of the world in Galileo’s day.”

Unfortunately, despite a strained and ultimately wrongheaded attempt at an analogy to Galileo’s problems with the pope, Goldberg profoundly misunderstands how science works. It’s true that scientists, like anyone, can become overly attached to their theories and refuse to listen to criticism. But new researchers are constantly entering the field, and while many surely become quickly socialized, the best of them would like nothing more than to turn conventional wisdom on its head. Young scientists challenging the assumptions and theories of their older colleagues is as old as, well, Galileo. The fact is that if all of them agree about global warming, it’s most likely because global warming is real.

But is the risk overblown? Does it matter if sea levels rise an inch per decade? Maybe, maybe not. But there are some serious ? though hard to quantify ? risks that counsel caution. The North Atlantic Conveyor, for example, is a part of the Gulf Stream that cycles warm water east to Europe and warms the continent. It is exquisitely sensitive to increased concentrations of freshwater caused by melting glaciers, and there is evidence that it can shut down quickly when a tipping point is reached, lowering temperatures in Europe enough to make Germany more like Siberia than Pennsylvania. And “quickly” means that it could happen over the course of a few years, not centuries.

Will it ever happen? Nobody knows for sure, but it is a catastrophic enough possibility that it seems prudent to take it seriously. Unless, of course, you’ve decided that scientific opinion is simply a vast lefty conspiracy. That’s what creationists think about the entire community of biologists, it’s what tobacco companies thought about cancer researchers, and increasingly it’s what conservatives think of atmospheric scientists. It’s not good company to keep.

POSTSCRIPT: If you like graphs and charts, the guys at eRiposte have a whole bunch of them here. Read ’em and weep.