Posted on 25 February 2011 by dana1981
Skeptical Science readers may recall my recent post in response to Roy Spencer, explaining How We Know Recent Global Warming Is Not Natural. The article has spread around quite extensively, including re-posts and associated articles at TreeHugger and Climate Progress, and some less prominent sites such as "skeptic" Lubos Motl's blog. Knowing that Motl has a physics background, I was interested to see if he could produce a knowledgeable critique of my arguments. Alas, upon reading his blog post, I was immediately disappointed.
The blog post started out on a low note. Consistent with his previous treatment of John Cook, Lubos immediately launched into an inaccurate description of my personal background, with a few childish insults peppered in for good measure. Not a good sign, but sadly, Motl managed to continue downhill from there. What followed was a Gish Gallop of Moncktonian proportionsTM.
The sheer volume of scientifically absurd statements following the introductory unpleasantries would take significant effort to debunk, and, to be blunt, simply doesn't warrant the effort. However, one particularly egregious error seemed to stick out like a sore thumb. Responding to my discussion of the "fingerprints" of man-made global warming, Motl argued that one critical fingerprint was missing: the tropical troposphere 'hot spot'.
Anthropogenic the Hot Spot is Not
As thingsbreak has just discussed in a guest post, the tropical troposphere hot spot is not an anthropogenic fingerprint. As John Cook has previously explained, when the surface warms, there's more evaporation and more moisture in the air. This decreases the adiabatic lapse rate - there's less cooling aloft. This means warming aloft is greater than warming at the surface. This amplified trend is the hot spot. It's all to do with changes in the lapse rate, regardless of what's causing the warming. If the warming was caused by a brightening sun or reduced sulphate pollution, you'd still see a hot spot. Contrary to Motl's claims, the hot spot is neither an anthropogenic fingerprint, nor a construct of climate models. It is an expected result of any surface warming, based on fundamental atmospheric physics.
The Not-So-Missing Hot Spot
The supposedly 'missing hot spot' can mean two things. It could mean the planet is not warming, but we have many other lines of evidence that the planet has warmed over the past 30 years. The other thing this could mean is that the hot spot is devilishly difficult to pin down.
As thingsbreak discussed in his guest post, the presence or lack of a tropical troposphere hot spot is not cut and dried. On short timescales, the data are in relatively good agreement with theoretical and modeling expectations regarding the hot spot. There is less certainty about the presence of the hot spot over longer timescales, but several recent studies indicate that the tropical troposphere is warming in a manner consistent with climate models. I highly recommend reading the guest post for the details on this subject. The long and short of it is that there's no physical reason why we should observe a hot spot on short but not long timescales, and newer studies indicate that the long-term hot spot may be there, so the seemingly 'missing hot spot' may very well be a consequence of problematic data.
Upon noticing Motl's error, I decided to engage in a discussion on the subject in his blog comments. Surely someone with Motl's physics background would readily realize and correct the mistake. Again, disappointment ensued. Motl quickly admitted that the hot spot is not specifically anthropogenic, but continued to insist that it is a construct of climate models, and thus if it is not present, the models are "falsified" and "dead". I politely attempted to explain the physics behind the hot spot, and for my trouble, Motl deleted my comments, banned me from commenting on his site, and again insulted me personally. On top of that, most of the comments from his readers (his Motl-ey Crew, if you will) followed his example with nothing more than petty insults. It was a disappointing display of a complete lack of willingness to engage in intellectual discourse. I have to admit, I was rather stunned at being banned from a site for doing nothing more than posting four polite comments pointing out an obvious error made by its author.
Regardless, the main point remains that the hot spot is not an anthropogenic fingerprint. Motl mirrored the biased perspective in the NIPCC report which we are examining as part of Prudent Path Week. The NIPCC report has an entire sub-section devoted to fingerprints, and yet it only discusses one - the tropical troposphere hot spot, with no mention of the many actual anthropogenic fingerprints which have been observed (I listed ten in this rebuttal). Instead, the NIPCC focuses on the one fingerprint which may be missing, even though it's not anthropogenic in origin! What form of "skepticism" is this, which ignores the inconvenient scientific data?
At least Motl does one better, mentioning a few real fingerprints in his blog post. Unfortunately he makes completely physically wrong statements regarding each one. Just as one example, Motl claimed that my statement that nights would warm faster than days as a result of an increased greenhouse effect (also known as 'decreasing diurnal temperature range' - the difference between daily maximum and minimum temperatures) was backwards. In fact, he described it as a "breathtakingly stupid mistake".
However, Motl is wrong. As I discussed in my article, greenhouse gases make more of a difference in nighttime temperatures. And this physical reality is not even remotely controversial. In fact, Svante Arrhenius correctly predicted that increasing atmospheric greenhouse gases would cause nights to warm faster than days over a century ago, in 1896:
"The geographical annual and diurnal ranges of temperature would be partly smoothed away, if the quantity of carbonic acid was augmented."
I suppose misunderstanding the physics behind the fingerprints is better than simply ignoring them, but before expending the time to refute a climate science article, one should first take the time to understand the relevant underlying physics. Especially if one has a background in physics. This sort of behavior is unfortunately all too common among those who wish to be considered "skeptics". They substitute their "common sense" for scientific research, and if the scientific experts say something which conflicts with their beliefs, the "skeptics" assume it's the experts who are wrong. Unfortunately, "common sense" when based on ignorance will usually lead to wrong conclusions, and assuming that it's the experts who are incorrect is unwise.
Those like Motl and the NIPCC who wish to be considered skeptics must amend their behavior. An honest skeptic does not run away and hide from intellectual discourse. An honest skeptic does not ignore the data which he finds inconvenient, or form absurd conclusions rather than make the effort to understand the underlying science. A real skeptic should behave as scientists do: examining all available evidence and discussing it in an open manner.
This string of events has illustrated the need for civil and unhindered discussion, which we'd like to remind all of our readers to pursue, lest the possibility of a common ground from the debate be lost. There are legitimate climate uncertainties worth discussing, but we must all first be willing to acknowledge, understand, and engage in open discourse about them.
Skeptical Science readers, let's please show the Motl-ey Crew how honest skeptics behave, and keep the comments civil and on-topic.