When the climate alarmist is struggling to make his case, he tends to reach for either the ad-hominem argument or some other rhetorical technique from the depths of the propagandist armoury.
Readers will recall the Bjorn Stevens paper on aerosols, which I suggested at the time gave alarmism "one helluva beating", as indeed it does. My headline seemed to amuse others and it was echoed by James Delingpole at Breitbart, his article later reproduced at Fox News.
The inevitable response was a statement by Stevens that sought to calm the troubled waters, suggesting that unidentified parties were claiming that it was the end of the global warming hypothesis. This was a fairly obvious straw man argument, but one that was sufficiently robust for Scientific American, which has now picked up the story in rather embarrassing fashion.
The guts of the article, by Gayathri Vaidyanathan, is an attempt to discredit Lewis by implying he has misinterpreted the study:
The misinterpretation of Stevens' paper began with Nic Lewis, an independent climate scientist. In a blog post for Climate Audit, a prominent climate skeptic blog, he used Stevens' study to suggest that as CO2 levels double in the atmosphere, global temperatures would rise by only 1.2 to 1.8 degrees Celsius. The measure is called "climate sensitivity."
It then suggests that Stevens has criticised Lewis:
[Stevens] took the unusual step, for a climate scientist, of issuing a press release to correct the misconceptions. Lewis had used an extremely rudimentary, some would even say flawed, climate model to derive his estimates, Stevens said.
I think it's fair to say that the misconceptions are all in the head of the article's author.* The "flawed" and "rudimentary" model has of course been endorsed and used by almost every important scientist working in the area of climate sensitivity. Sure it's simple, but for models that is generally a good thing. In fact a glance at the author list for the famous Otto et al climate sensitivity paper reveals the presence of one B. Stevens! There is no doubt in my mind that Ms Vaidyanathan has been doing some rather ugly twisting of Steven's words here.
And as if to emphasise that she doesn't know what she is talking about either, we have her startling statement about the scientific evidence on climate sensitivity.
When scientists use temperature records from the 20th century to constrain sensitivity, they get low values. When they use records stretching many millenia, painstakingly assembled from trees and other proxies that contain imprints of past climates, they get values toward the higher end of the IPCC range of 1.5 to 4.5 C.
A cursory glance at the IPCC's figures for paleo studies shows that they span the range from 1-6°C, and it goes without saying that there is not mention of the fact that the IPCC also noted that climate sensitivity estimates based on conditions over recent millennia may well not reflect the value of climate sensitivity in today's climate.
What a shambles. What an indictment of "Scientific" American.
[* corrected]
Bishop Hill
The SciAm piece has now been amended to remove the insinuation that Lewis misinterpreted Stevens' paper. The allegation that people have been saying that the paper kills off global warming completely remains.
Bishop Hill
Unless I am mistaken it has now reverted to the original text. I'm confused...
