Paul Krugman needs a course in remedial reading. That’s the conclusion to be drawn from his New York Times column last Friday, in which he called my NR cover story “Scare of the Century” part of a “disinformation campaign” about climate change.

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Krugman writes that, “as evidence that global warming isn’t really happening,” I offer “the fact that some Antarctic ice sheets are getting thicker.” I did indeed note the thickening of Antarctic ice—about which, more in a moment—but I never claimed “that global warming isn’t really happening.” Rather, I wrote that “global average temperature has risen by about 1 degree Celsius or less since the late 1800s.” No serious person on either side of the global-warming debate questions this. Nor do serious commentators doubt that human activity, by increasing atmospheric concentrations of carbon dioxide, contributes to global warming. I acknowledged all of these points.

What’s in contention, scientifically, is how much of the warming we’ve seen so far is a consequence of human activity (as opposed to natural climate variation), and how much warming human activity will cause in the future. The policy debate focuses on how dangerous the warming is, what we can do to stop it, and whether doing so is worth the economic price we would pay. My article considered these questions, addressing in particular the oft-repeated claim that man-made global warming will melt the polar ice caps, raise sea levels, and flood the coasts. If Krugman wishes to know what I actually wrote instead of putting words in my mouth that are flatly contradicted by what I wrote, he is welcome to go back and read my article.

But let’s consider the one claim Krugman specifically addresses: that “some Antarctic ice sheets are getting thicker.” His counterargument is that Curt Davis—whose study of Antarctic ice I cited—is displeased with the way the Competitive Enterprise Institute has used his work in television ads about global warming. “[Davis] points out,” writes Krugman, “that an initial increase in the thickness of Antarctica’s interior ice sheets is a predicted consequence of a warming planet, so that his results actually support global warming rather than refuting it.”

I have not seen the TV ads, and cannot say whether they distort Davis’s work. My article does not. Not only did I acknowledge that the planet has gotten warmer, but I explained that warmer water around Antarctica’s coasts has likely caused “more surface evaporation, making for higher humidity and more precipitation” in the continent’s interior. Of course, the fact that warmer temperatures are causing greater snowfall proves neither that this phenomenon is harmful nor that human activity is the primary cause of it. I offered a variety of reasons to think that 1) the ice caps aren’t melting fast enough to produce a threatening rise in sea levels and 2) the melt we are seeing can be explained largely as a result of natural climate variation. Krugman offers no response to any of this.

Studying Davis
Concerning the Curt Davis study, let me make a few additional points now lest someone else falsely accuse me of misrepresenting his work. Davis has three objections to the way his study has been cited in the TV ads. One is the complaint Krugman mentions, and to which I’ve just replied.

The second—as summarized by a press release from his university—is that the study “only reported growth for the East Antarctic ice sheet, not the entire Antarctic ice sheet.” Davis used satellites to measure changes in the surface elevation of about 70 percent of the Antarctic ice sheet between 1992 and 2003. He then calculated how much ice the areas he was looking at had gained or lost during that period. He found that about 7.3 million square kilometers of the East Antarctic ice sheet were rising by about 1.8 cm per year—which amounts to roughly 45 billion metric tons. That’s enough to lower global sea levels by 0.12 millimeters per year. In the context of discussing the snowfall-driven ice build-up, I cited those figures without specifying that they applied only to East Antarctica. But anyone who wishes to accuse me of leading readers astray should note that, when you add in the study areas that lost ice, you still find that the total area—about 8.5 million square kilometers—gained an average of 1.4 cm per year in elevation. That’s about 41.7 billion cubic tons—enough to lower sea levels by 0.1156 millimeters per year. Discerning readers will note that this rounds up nicely to . . . 0.12 millimeters, the number I used. Some distortion.

Davis’s third objection to the TV ads is that the study only noted growth “on the interior of the ice sheet” and “did not include coastal areas, . . . which are known to be losing mass.” These losses “could offset or even outweigh the gains in the interior areas.” But Davis’s study also didn’t look at a large section of the ice sheet around the South Pole, owing to the fact that the satellites’ orbits prevented them from “seeing” there. (For a map showing Davis’s study area, go here and scroll down the page.) Since this unstudied area lies in the ice sheet’s interior, it almost certainly gained ice over the course of the study, and would accordingly have offset the (also unmeasured) coastal loss. (The study notes that its estimate of ice build-up is “conservative” for this very reason.) Of course, guesses about what was happening in the areas Davis didn’t study are just that—guesses. They do not change what we know: that the vast majority of the ice sheet was, on balance, growing between 1992 and 2003.

In any case, the paragraph following my mention of Davis’s work cited a more recent study providing evidence that there has been a net loss of ice in Antarctica over the past three years. This is something I surely would not have done had I decided to ignore facts that presented obstacles to my argument. Indeed, I gave evidence to think that both Greenland and Antarctica are presently losing ice. The point of my article was never to deny this, but rather to argue that we cannot say with certainty that the loss is either a serious threat or primarily the result of human activity.

Who’s Thinking?
So much for Krugman. Equally baseless criticisms of my piece have come from the liberal web publication Think Progress, which says that my article contains “several serious errors and omissions” and that I am guilty of “distorting evidence” and “mislead[ing my] readers.” Think Progress accordingly published a “debunk” that is nothing of the sort. Let’s consider it point by point.

In response to my claim that “there is wide disagreement about the extent to which carbon-dioxide emissions are responsible for the warming we’ve seen so far,” Think Progress says that the U.S. Climate Change Science Program has “concluded that humans are driving the warming trend through greenhouse gas emissions, noting that ‘the observed patterns of change over the past 50 years cannot be explained by natural processes alone.’” It also says that “Science Magazine [sic] analyzed 928 peer-reviewed scientific papers on global warming” and found that “not a single one challenged the scientific consensus the [sic] earth’s temperature is rising due to human activity.”

May I encourage whoever wrote the “debunk” to familiarize himself with the meaning of the word “extent.” As I have already explained, nothing in my article denied that human activity is causing global warming to one degree or another. What I said was that there is no agreement about “the extent to which” human activities, as opposed to natural processes, are to blame. What Think Progress says about the U.S. Climate Change Science Program and the Science analysis of peer-reviewed papers does nothing to settle that question.

Think Progress also quotes a 2002 EPA report saying that warming “has been particularly strong within the past 20 years” and is “due mostly to human activities.” But one EPA report does not settle the scientific question, nor does it prove that scientists regard the question as settled. The report acknowledges uncertainties about the extent of natural climate variation and the ability of models to simulate climate change, but Think Progress doesn’t bother to quote those parts. Moreover, the report’s comments about the role of human activity in global warming are based on the Intergovernmental Panel on Climate Change’s models, which have long made unrealistic assumptions about the degree to which human activity is increasing atmospheric CO2 concentrations. Accordingly, they have tended to overpredict warming. (Patrick Michaels of the University of Virginia notes that the IPCC’s input is 41 percent higher than the observed rate of CO2 increase, and that even NASA scientist James Hansen—who in many ways embodies the alarmist view on warming—has said that the IPCC’s assumptions may be “unduly pessimistic.”)

Next, Think Progress criticizes me for saying that, “when it’s not even clear that the warming we’ve seen is hurting us—many argue that it’s a boon, citing its benefits to agriculture and its potential to make severe climates more hospitable—such draconian solutions [as implementing the equivalent of 30 Kyoto Protocols, which one scientist has suggested,] should be unthinkable.” It notes a 2001 IPCC report finding that climate change’s “negative health impacts are anticipated to outweigh positive health impacts.” But—again—the IPCC models make unrealistic assumptions about the speed of climate change, and should not form the basis of predictions of how bad future warming will be. In any case, my article did not rule out the possibility that climate change will have harmful consequences in the future; what I said was that it isn’t clear whether the consequences have been harmful so far. Even if warming is predominately the result of human activity, and even if its harms will outweigh its benefits, the question is whether it will be bad enough to justify the economic castration that significant greenhouse-gas reductions would require. Think Progress offers no reason at all to think that it will.

Think Progress also objects to the way I cite a study by Ola Johannessen. Using satellites, Johannessen measured changes in the surface elevation of the Greenland ice sheet’s interior and found that it was gaining ice. Think Progress’s response is to quote realclimate.org as saying that “Johanessen et al. were not able to measure all of the coastal ranges. Indeed, the thinning of the margins and growth in the interior Greenland [sic] is an expected response to increased temperatures and more precipitation in a warmer climate. These results present no contradiction to the accelerated sliding near the coasts.” My article, however, acknowledged ice loss near the coasts. My point was simply that ice gain in the interior should be subtracted from loss at the coasts if we want to have a realistic picture of how much ice Greenland is losing.

The next objection is to my claim that, “if today’s temperatures are causing Greenland’s coastal ice to slide into the sea, it must have been positively galloping there 80 years ago.” As evidence, I cited a study forthcoming in Geophysical Research Letters which finds that temperatures in Greenland were as warm in the early 20th century as they are today, and that the rate of warming back then was nearly twice as fast. That’s noteworthy because these temperature changes happened too early to be attributed to the burning of fossil fuels. Greenland was warm back then for reasons that had nothing to do with us—and somehow the ice caps survived. Think Progress’s utterly irrelevant reply is that the last three decades “have seen a sharper rise in global air temperature than any other period since at least 1860” (italics mine). Global averages are of course less than illuminating about the effect of climate change on particular regions. When talking about Greenland, it is generally useful to talk about Greenland.

Finally, Think Progress makes the same objection concerning Curt Davis’s study that Paul Krugman did, and to which I’ve already replied.

In light of all this, it would be easy to accuse Paul Krugman and Think Progress of “distorting evidence,” “misleading readers,” and engaging in a “disinformation campaign.” I decline to return their favor. But I will permit myself the modest suggestion that, in the future, they strive to have the slightest idea what they are talking about.

—Jason Lee Steorts is deputy managing editor of National Review.