“Loehle on Hoffman et al and CO2 trajectories” Anthony Watts learns that the “National Council for Air and Stream Improvement, Inc.” forestry lobby group has funded a paper by Craig Loehle in Atmospheric Environment, a ‘low-impact‘ air pollution journal.
Loehle whips up some arbitrary equations that seem to be equally good at matching historical atmospheric CO2 concentrations as the IPCC’s, so clearly nothing can be concluded from the IPCC’s ‘scary’ predictions.
Simple equations make such smooth curves! (Loehle, 2010. Fig. 3)
The IPCC’s predictions based on physical and chemical atmospheric science. That’s more relevant than pulling numbers out of thin air and pretending you’ve studied something in its scientific context. This is looks like statistical game-playing to me.
Wott's Up With That? 
“Statistical game-playing” is the kindest thing one could call it. As so often with WUWT, it’s difficult to tell if they are lying or just massively ignorant, but they completely ignore the fact that WE KNOW HOW MUCH CO2 WE ARE RELEASING. Considering we also know how much atmosphere there is, projecting future CO2 levels has nothing to do with curve-fitting. It’s a function of how much carbon we burn (in the best case, ignoring positive feedbacks), and we know there’s no “saturation” curve to that.
You obviously don’t know much about Atmos Env, nor atmospheric sceince. It is hardly a “low impact” Journal, and for most serious atmospheric scientists it is very highly regarded and widely subscribed to.
[Perhaps you’re right, but their “impact factor” is 2.89, whereas Nature is 30.98. Also, this is an “air pollution” journal with no apparent reputation in climatology. Do you have any argument with the content of the paper? – Ben]
Well since you ask, “The IPCC’s predictions based on physical and chemical atmospheric science” actually are based on CO2 projections as well as, of course, the GCM’s. I have no problem with the Loehe paper, that simply points out that the current projections of CO2 concs are based on dodgy equations. Without doing the calcs myself (and I have better things to do like learning McTell’s Statesboro Blues, cant get the alternating thumb right!) I would say that the IPCC’s projections are probably over-estimated. But then again, projecting out to 100 yrs is fairly unreliable, since the model calibration was for such a short time. Overall tho there is nothing wrong with the paper as far as I can see. Cheers
The projection the IPCC uses is NOT based on physics. It is an extrapolation of the CO2 rise trend which results from burning fossil fuels and deforestation. They fancy it up with the Bern carbon cycle model but end up with exactly a simple exponential equation as a fit to the data. No real physics in spite of the window dressing they give it. Hope this clarifies the point of the paper.
[Thanks for your comment, but I’m still left wondering how your projections were selected. As you suggest, the IPCC projection is extrapolated from the historical rates at which we have actually released carbon and the expected future emissions. Is there a reason why we should take your paper’s alternate projections seriously, or are they just arbitrary mathematical counter examples? – Ben]
My point was simply that the extrapolation the IPCC did is under-determined by the data, and very different models that fit the data equally well exist. They took historical trends of “actually released” but just fit a model to it (constant doubling time).
By the way, NCASI is NOT a lobbying organization. We do research for the wood products industry such as how to measure pollutants, surveys of endangered species, toxicology, etc. You can check our list of thousands of publications in the peer-reviewed literature (and my 120 pubs).
[I agree that “lobbying” is the wrong characterization, but their purpose is to serve the wood products industry. The NCASI would be unlikely to pursue research that didn’t support that industry… – Ben]