The Institute for Advanced Study, which has played host to such luminaries as Albert Einstein and Kurt Gödel, is holding a series of talks to celebrate the birthday of another one of its famous faculty: Freeman Dyson. Dyson made important contributions to a huge variety of fields and gave us the concept of the Dyson Sphere. The talks in his honor covered many of the fields that Dyson influenced. Here, we'll describe the talk by physicist William Happer.

As a physicist, William Happer is best known for laying the groundwork for adaptive optics, the method of reading the atmosphere's distortions so that telescopes can correct for them. This approach has revolutionized ground-based astronomy, allowing some observatories to produce images that rival those taken from space. These days, his research focuses on the quantum states of atoms and electrons.

Most people know of Happer for entirely different reasons. He's on the board of the George C. Marshall Institute, a conservative think tank that has attacked mainstream climate science (another member of the board is Roy Spencer, who takes a similar stance). Rather than critiquing the field in the scientific literature, Happer has generally focused on writing op-eds in The Wall Street Journal. Given that he was slated to speak to an audience of scientists at a science-focused event, I was curious to see what sort of talk he would give.

In many ways, Happer gave three different talks. And his strange mix of approaches left me wondering if any of the three should be taken seriously.

Al Gore and serious-sounding science

Happer started out his talk with an extended riff on Al Gore. Apparently, whoever handled the graphics for one of Gore's book covers took the liberty of photoshopping some clouds out of its photo of the Earth in order to make it look more appealing. To Happer, this was evidence that Gore was untrustworthy when it comes to climate change. As his time on the podium wore on, the irony of this suggestion loomed large.

Happer moved on from there without explaining why Gore made an appearance at all, quickly switching gears and beginning to talk about science. He focused on the recent slowdown in warming, concluded that "something is seriously wrong with the models," and went on to describe what he thinks the problem is. In his mind, it all comes down to the spectrum of infrared light absorbed by carbon dioxide.

When it absorbs light, CO 2 converts that energy into various types of motion in the form of vibrations and by the flexing of its chemical bonds. Each one of these possible forms of motion, along with the combinations of two or more types of motion, creates an individual line of absorption in the infrared. Add in things like the Doppler effect—CO 2 gas contains molecules in motion, which absorb light above and below the typical lines—and everything starts to blur together. The end result is a large and complex band of absorption.

Most of this band doesn't matter, according to Happer. Parts of it absorb so strongly that the average photon at these energies doesn't even get a meter before being absorbed. Others overlap with parts of the spectrum that are absorbed by water vapor. Here, Happer almost seemed to be arguing that CO 2 can't contribute to the greenhouse effect at all, but he then went on to point to a small shoulder of its spectrum where CO 2 matters. Happer assured the audience that this is where it can drive some greenhouse warming. To an extent, at this point in his talk, Happer seemed surprisingly OK with the consensus.

The issue he has is that there is more than one way to calculate the absorption profile, and Happer is convinced that most climate models use the wrong one—one that overestimates the amount of absorption in the critical region where CO 2 's absorption matters. And because of this, the models will overestimate the amount of warming that additional carbon will produce.

The wheels come off

If Happer ended there, he would have made what appeared to be a compelling, scientific-sounding argument. But the floor was then opened for questions, and Happer used his answers to give a completely different presentation—one riddled with errors and sloppy rhetoric.

When asked what has caused the warming, Happer admitted that some of it comes from CO 2 , but he then listed some other things he deemed more important. Happer noted that the periods when temperatures increased most rapidly correspond to one phase of an ocean current cycle called the Pacific Decadal Oscillation, but he didn't explain how an oscillation, which involves things returning to their original state, could possibly send temperatures in one direction. He then claimed temperatures "correlate very well" with cosmic ray data, when in fact they do not.

After relying on these correlations, Happer was asked about Richard Muller's work with the Berkeley Earth project, which found that the best correlation for modern temperatures was with CO 2 . "In a word, it's junk," Happer stated. "He needs to make a prediction that is actually observed."

The strange statements extended beyond climate. Repeated studies have shown that ocean acidification will harm a variety of species and may already be causing problems for shellfish. Yet Happer claimed that tripling carbon dioxide "doesn't do anything" to ocean life. Rather than saying that burning fossil fuels has been a net positive for many societies, Happer dismissed concerns with a blanket statement. "I don't think there's any evidence that fossil fuels have harmed anyone," he said. Even though the Earth has entered and exited stable "snowball" states, Happer said that the concept of climactic tipping points is "something dreamed up to make people panic right away."

And somewhere in all of this, Happer dropped a whopper: "If you look back at history, temperatures have never correlated with CO 2 ."

For added measure, he took one last shot at Al Gore and then dismissed all of climate science. He said it has abandoned skepticism and is "a religious cult."

Severe foot wounds

All of this is a shame. Happer initially recovered from his original, gratuitous attacks on scientists to make what appeared to be a skeptical argument that seemed solidly based in science. But the rapid-fire burst of misrepresentations and blatantly false statements left me wondering if the apparently scientific arguments he made were just as faulty. After all, the method he dismissed, creating Voigt profiles, appears to be used in a number of different areas of science.

Afterward, I got in touch with someone who knows a bit about both the physics and the climate models themselves—Ellie Highwood at the University of Reading. I described Happer's argument to her to get her response. "I'm not convinced by this at all," she said. In more detail:

As carbon dioxide increases in the atmosphere, a greater proportion of the energy trapped by further increases is indeed trapped by the edges of the main lines. However, even if there are differences in the treatment in the edges of the lines, I would think that these would only become important at very large carbon dioxide concentrations and would not make a big difference in the forcing either in the historical simulations or the future ones.

As expected, this is also a fairly convincing, science-based argument. Given that it wasn't packaged with a bunch of blatantly false statements, it seems all the more convincing.