Some of you accuse me from time to time of being sarcastic. It being the Christmas season, I will refrain the temptation to be sarcastic and present instead some sayings from Rasmus (Benestad), courtesy of our friends at realclimate, all conveniently taken from only one thread. There is much food for thought here. There is something inspirational in almost every phrase. I eagerly await more pearls.
atmospheric and oceanic tides are well-established now, and explained in terms of physics.
I can easily predict that the summar will be warmer than current (winter) conditions…
Science (here used in a wider meaning including engineering) has also formed our culture and enabeled you guys to read this blog.
I wouldn’t know much about hair growth products, but I am convinced that the field of meteorology is well-established and the forecasts useful.
Here is a reason why meteorologists do not use statistical models for weather forecasts. When you travel by plane, the aviation authority depends on good forecasts for your safety. Statistical models are not adequate. You really need to include the physics!!!
These are aspects the medical profession does not understand in every detail due to their baffling complexity, but medical doctors nevertheless do a very good job curing us for diseases, and shrinks heal our mental illnesses.
Continue reading →
I mentioned in connection with GCMs and Ice Ages, that the CO2 cycle was presently regarded by the leading paleoclimatologists as mysterious. This was contested by Lars Kamel, who observed that cold water dissolved more CO2 and did not see why there was a problem. Here I’m merely reporting what I’ve read and do not present any independent judgement. My source was Archer et al [Rev Geophys, 2000], an authoritative source who stated clearly that changing solubility did not account for changing levels as follows:
Because CO2 is more soluble in colder water, colder sea surface temperatures could lower pCO2. However, the magnitude of the glacial cooling can account for only a small fraction of the observed pCO2 drawdown.
They observed the following in respect to attempts to explain the CO2 cycles:
in spite of the clear importance of pCO2 as an amplifier or even a primary driver of the glacial cycles, and the additional motivation provided by the threat of future climate change, we remain ignorant of the mechanisms responsible for the glacial/interglacial CO2 cycles…. We conclude that in spite of the importance of understanding the natural carbon cycle, the solution to the mystery of the glacial/interglacial CO2 cycles still eludes us.
My surmise is that the mechanisms proposed in Archer et al [2000] are not included in GCMs – and if included, are all pretty speculative. Pause and reflect a little: here are effects which are said to have explanatory power for such small matters as whether we’re entering or exiting an Ice Age, but are (probably) not in GCMs. Here are some extended excerpts with no commentary. Continue reading →
Benestad at realclimate here, against Cohn and Lins, argues that their use of time series methods more advanced than Benestad’s IID, somehow offended against the laws of physics, "pitching statistics against physics" – plus other gems. It has to be read to be believed. Now white noise (equivalent to Benestad’s IID, independent identically distributed residuals) has a distinctive horizontal spectrum, while red noise has spectra sloping down and to the right. Before proclaiming that it is against the "laws of physics" for temperature data to have autocorrelation properties, one thinks that Benestad might have examined some actual spectra of temperature and temperature proxy series (rather than exclusively relying on GCM output), to determine whether his IID assumption applies.
As I mentioned before, the redness of geophysical series was remarked upon as long by Mandelbrot. The references in Cohn and Lins [2005] are clear and Benestad would profit from reading these articles. Another interesting recent discussion is Pelletier [PNAS, 2002], who not only shows redness in both temperature and temperature proxy data, but proposes a physical mechanism which could account for the power law properties of the series. I don’t have any views on whether Pelletier’s theory is right or wrong, but it is interesting. Equally important is the mere fact that the series have distinctive power law properties – since the measurements have power law properties, such power law behavior is obviously not against the "laws of physics" (contra realclimate), but a valid topic of inquiry. If GCMs do not capture this power law behavior, as they seem not to do, based on Benestad’s account, then possibly the GCMs are at fault, rather than the data. Continue reading →
I’ve tried to stay away from discussing GCMs where my knowledge is limited, but everyone seems to want to discuss them, so, against my better judgement, I’m posting up some thoughts. asked some people at AGU about whether GCMs could model getting into and getting out of ice ages. In some treatments, the presence or absence of ice sheets appears as an independent forcing, which seems to be peeking at the hand a little when you’re trying to explain ice ages. CO2 fluctuations are integral to current glacial modeling, but there doesn’t seem to be any agreed explanations for glacial/interglacial CO2 cycles. Continue reading →
Cohn and Lins [GRL 2005] , engagingly titled “Nature’s Style: Naturally Trendy”, questions whether recent trends in temperature can be classified as statistically significant, if considered from a more general perspective, including stochastic processes other than white noise. Some of the issues will be familiar to readers of this blog, although the treatment in Cohn and Lins is obviously different. Cohn and Lins has prompted a reaction from Rasmus Benestad, a prominent proponent of the bizarre assumption of identical independent distributions (I.I.D.) in climate statistical testsing, who accuses Cohn and Lins at realclimate here of attempting to "pitch statistics against physics". Amusingly, Benestad argues that "fairly stable" climate is evidence against Cohn and Lins, with the URL supposedly showing "fairly stable" climate being – wait for this – MBH. Continue reading →
When I was thinking about spurious regression and ARMA(1,1) here , I mentioned a paper by Ai Deng [2005], which I found interesting. Deng has noted up this mention at his website as follows
Click here to visit a web blog hosted by Steve McIntyre that contains some interesting discussions about Ferson et al. (2003) and this paper from the perspective of Climatology.
Compare his discussion of spurious regression to (say) Benestad’s neolithic ruminations at realclimate about independent identically distributed errors. Even if you can’t fully appreciate the arguments, you can readily appreciate the difference in quality.
Regular correspondent David Stockwell has set up a new blog and has posted an interesting comment on Briffa, about which he says:
Have become interested in checking out dendroclimatology from the ENM point of view – particularly evaluating the model used for functional responses of alpine trees to temperature. All studies in Briffa et al. 2001 (figure below) invariably use a linear model, OLS fit of the proxy to temperature be it tree ring width (TRW) or density (MXD). It is of course not possible for tree growth to increase indefinitely with temperature increases – it has to be limited. The obvious choice for a more accurate model of tree response is a sigmoidal curve.
Drop in on him and say hello
.John A adds: I’ve added David Stockwell’s blog and Luboà…⟠Motl’s Reference Frame to the “Weblogs and Resources” link in the sidebar
Raymond Pierrehumbert at realclimate has recently posted on climate sensitivity, citing Hegerl et al. [2003] approvingly. As less weight is being put on Hockey Team arguments, more weight is being put on these detection and attribution arguments. Maybe I’ll put a few inquiries out for data and methodology on these studies. For now, I’ll point out again how large the residuals are for Hegerl et al [2003]. There is no digital data available, but visually it seems impossible that there is anything like 57% explained variance. I’m recycling here part of a post made last February on this study, when climateaudit wasn’t as active as now (although it was already starting to get a lot of hits.) Continue reading →
Obviously one of the major themes of the M&M articles is the remarkable lack of robustness of MBH98. Bürger and Cubasch, hot off the press at GRL, asks the following question:
whether or not the MBH98 and relative approaches are robust, including the predictor selection issues as argued by McIntyre and McKitrick [2005a], is the subject of the current study.
They conclude:
Without a model error estimate and without techniques to keep it small, it is not clear how these methods can be salvaged to become robust.
They cite both our 2005 articles approvingly. Continue reading →
There is a long article in Volkskrant dated Dec. 10, 2005, in which journalist Martin van Calmhout, among other things, expressed his consternation at seeing an English translation and discussion of a previous article on Mann on climateaudit within a half day of publication (see here). We’ll try to be equally prompt this time. Here’s a tentative translation together with Dutch pdf here. I’ll update the translation as some of our Dutch speakers chip in. There are a few missing paragraphs still as my attention to this wandered after a while. For reference, there is machine Dutch-English at http://www.altavista.com, which I used here together with a little editing (I know no Dutch, but am used to the word inversions from similar translations from German and that’s the basis of my editing.) Update: Andre has sent in a corrected version, which I altered slightly for English style.
If I’ve understood the article correctly, he damns us with faint praise as follows:
Nevertheless they are amateurs. But the people talking here appear to know every comma of Mann’s work and to have checked all his references. You could not deceive them with some vagaries about greenhouse gas effect.
Later, he falsely accuses us of being bought and paid for by ExxonMobil, which seems somewhat inconsistent with the previous suggestion of "amateur" status. At climateaudit, we do not wear kneepads. Continue reading →
Climate Audit 
A Shout Out to David Stockwell
Regular correspondent David Stockwell has set up a new blog and has posted an interesting comment on Briffa, about which he says:
Drop in on him and say hello
.John A adds: I’ve added David Stockwell’s blog and Luboà…⟠Motl’s Reference Frame to the “Weblogs and Resources” link in the sidebar