The following guest blog is by Holman Jenkins, a Wall Street Journal columnist and member of the WSJ editorial board, in response to a blog (here) by Stuart Gaffin, a climate researcher at Columbia University who is a regular contributor to these pages. Thomson Reuters is not responsible for the content — the views are the author’s alone.

By Holman Jenkins

Several of my emailers in response to my WSJ column were also perplexed what I meant when I wrote that climate science has managed to yield on the most important issue -– namely mankind’s actual impact on the climate — only a “negative finding.” In fact, clarification appears in the next sentence: Science hasn’t been able to how “an increase in the atmosphere’s component of CO2 is impacting our climate, though the most plausible indication is that the impact is too small to untangle from natural variability.”

I use “science” here to mean what most people mean by science: systematic study of the world in hopes of drawing reliable conclusions. I use “climate” the way everyone uses “climate.” Mr. Gaffin seems to read “climate” as “atmosphere” and my statement as suggesting we know nothing of any kind about how the atmosphere might behave in response to rising CO2 levels. But that’s not what I said. I’m talking about what everyone actually cares about, whether the net result is a warming climate that will continue to warm in detriment to the presumed interests of humanity.

I don’t need to rehearse how much of current claims about a human contribution to warming are based on climate models. Many scientists have pursued actual empirical results (i.e. from the world, not from computer models) to show the human contribution, but results have been maddeningly elusive or indeterminate. Speaking for myself, that’s information I would very much like to have — I would not impose large, costly adjustments on society based simply on predictions of computer simulations created by scientists eager to affirm their intuitions about climate and CO2.

But there’s no satisfying people like Mr. Gaffin that skepticism is not a willful resistance to their metaphysical certainty. Here we verge on the real source of my dissatisfaction with, and even distrust of, many of the self-appointed spokesmen for climate science, who seem to be engaged in a collective exercise of begging the most important questions.

Mr. Gaffin cites some (uncited) authority that “current research [has] concluded with 90% confidence that current warming is due to human activities.” I assume he’s referring to the UN’s IPCC, but he doesn’t say. Those double “currents” are peculiar as well -– since warming is “currently” not taking place by the most relied-upon temperature records (i.e. current research). I suppose, though, he can define “current” however he wants.

But here’s my larger gripe: How much more useful it would be if climate scientists could say (for instance) that the warming experienced in the 20th century coincided in systematic fashion with rising man-made CO2 levels and is unprecedented in the behavior of earth’s climate. How much more helpful if they could show that past climate history yields strong evidence that previous warming episodes were caused by rising CO2 levels.

How much more helpful if they could say this or that particular feature of climate warming accords precisely with what is known about CO2’s behavior in the atmosphere and is inconceivable in the absence of rising CO2.

That Mr. Gaffin instead relies on unnamed authorities supplying faux-certain probabilities that a factual proposition is true is an example of everything wrong with much public presentation of climate science (and richly ironic since Mr. Gaffin’s whole objection to my column is that it  expresses uncertainty about the human role in climate change.)

In a pedantic quibble, Mr. Gaffin also complains that I refer to mankind’s contribution to rising CO2 levels. To be as pedantic as Mr. Gaffin but more accurate, “contribution” allows for a human contribution in a range of 0% to 100%. More importantly, presumably he knows that the atmosphere isn’t a sealed container and that the oceans, volcanoes and biosphere all play a role in CO2 levels.