At the heart of science is an essential tension between two seemingly contradictory attitudes -- an openness to new ideas, no matter how bizarre or counterintuitive they may be, and the most ruthless skeptical scrutiny of all ideas, old and new. This is how deep truths are winnowed from deep nonsense. Of course, scientists make mistakes in trying to understand the world, but there is a built-in error-correcting mechanism: The collective enterprise of creative thinking and skeptical thinking together keeps the field on track.
-- Carl Sagan, The Fine Art of Baloney Detection, Parade, February 1, 1987
There is a lot of information in that quote, really. The part at the end, that scientists cam make mistakes in their attempt to understand the world, is what I want to point out today. Further, it seems to be common for older scientists to become mistaken, and I think for many of them it is that they become locked into that ruthless skepticism that Sagan refers to, but lose part of their openness. We discussed this in depth with Freeman Dyson, who seems to have an emotional reaction to climate change that fires up his skepticism and closes down his openness.
Another example seems to be George Kukla, a renowned scientists from Columbia University. Kukla is best known for his tremendous work in paleoclimate, where his specialty has been in exposing the role that orbital variation plays in changing climate [see bio]. Kukla is now emeritus at Columbia, but is a "special research scientist" at Lamont-Doherty Earth Observatory, and appears to be marginally involved with some ongoing research. Though less visible than Dyson, or less credible people like Pat Michaels or Fred Singer, Kukla has been a skeptic of anthropogenic climate change. He is often quoted (or liberally paraphrased) as believing that variations in sunlight are causing the current global warming, which will turn toward a new ice age in the future.
I just read a 2007 interview with Kukla [link] in Gelf Magazine. I urge you to check it out. Somehow I ended up there after watching a short video clip from Letterman [link] in which Kukla appears. In the interview, Kukla seems to present evidence that the current warming is very similar to warming during previous interglacial periods that then transitioned to glacials. However, there are several points of fact that are misrepresented. For example, Kukla says
The knowledgeable climate students know that the global climate works in cycles. The relatively short cycles happen to be about 60 to 80 years long, out of which one half goes up and the other half down. Right now the Northern Hemisphere appears to be at the turning point of the warming branch. Just wait!
Well, there certainly are cycles in climate, but the "short cycles" of 60-80 years are certainly not well quantified or understood. In fact, I know of no compelling evidence for periodicity in this range. There is a lot of interest in "decadal variability" in the climate system, which could certainly be a source of noise in the spectrum around 60-80 years, but is unlikely to be a cycle by any sort of sensible definition of the word. The second part of the quote above, that the northern hemisphere is now turning from warming to cooling, is likely to be shown false very shortly. This is really just a regurgitation of the common climate change denier tactic of using insignificant short-term trends to say something that is false. We can only hope that Kukla is around in a few more years to see the results.
Here's another quote from the interview:
What happened then was that the shifting sun warmed the tropics and cooled the Arctic and Antarctic. Because the tropics are so much larger than the poles, the area-weighted global mean temperature was increasing. But also increasing was the temperature difference between the oceans and the poles, the basic condition of polar ice growth. Believe it or not, the last glacial started with "global warming"! The shifts of solar orbit today are about two to three times weaker than in the last glacial, or by the way, in the last 400,000 years. So, on that basis, we have little to worry.
In this we see Kukla's motivation: he is so enraptured by the astronomical theory of climate change, that he has closed his mind to other forms of climate change. This is his downfall on this topic, for some reason he can't see the vast difference between past climate change and current global warming. He's still not nearly as severe an offender as other skeptics, though. He recognizes important aspects of anthropogenic activity, but somehow ignores them. He also sees, as he says above, that changes in sunshine are very small right now, and later in the article he even acknowledges that, "No doubt that we have about 10,000 or even possibly 20,000 years still ahead before the major ice advance can start." This implicitly means that there are very different timescales involved, but this just isn't enough for Kukla. Above, he also says that a sign of the oncoming ice age is a warming tropics and cooling poles. However direct observation shows that the polar regions are now warming twice as fast (at least in the Arctic, more mixed in the Antarctic) as the globe as a whole. This should be a red flag, but to the true believer, it is evidence against the common thinking.
Okay, you are getting the idea, and I don't want to beat up on this guy, so just one more quote, showing again that Kukla almost accepts the current thinking:
The CO2 certainly has an influence. For instance, it appears that already now, with still relatively low concentrations, it may have a significant warming impact on the night [temperature] minima. And because the usual way to determine the daily mean is as the average of the daily minimum and maximum, here we go! But it is difficult to be sure: more clouds can do the same.
So he clearly says that people are changing climate, yet then he says they aren't. If you are confused about what Kukla believes, then I think you join a long list that probably also includes Kukla himself.
Again, let me stress that George Kukla has made impressive and important contributions to our understanding of paleoclimates. All I am saying is that his current opinions about global warming seem to be somewhat off the mark. My opinion is that he has become fixated on the astronomical theory of climate change to such a degree that he can no longer tolerate the rational arguments for anthropogenic climate change, which are founded in basic science and backed up by direct observation. Like quite a lot of scientists who are, well, let's just say "getting up there in years," he has developed an emotional response to the current science that can not be defended by scientific arguments. I hope he comes around at some point.