Guest post by Frank Lansner
IPCC – How not to compare temperatures – if you seek the truth.
There are numerous issues discussed intensely when it comes to IPCC-illustrations of historic temperatures, here for example the illustration from IPCC Third Assessment Report:
Fig 1. Taken from IPCC TAR
In short we have heard of problems with 1) the Mann material, 2) the Briffa material, 3) The cherry picking done by IPCC to predominantly choose data supporting colder Medieval Warm Period, 4) Problems joining proxy data with temperature data mostly obtained from cities or airports etc, 5) Cutting proxy data of when it doesn’t fit temperatures from cities, 6) Creating and Using programs that induces global warming to the data and finally 7) reusing for example Mann and Briffa data endlessly (Moberg, Rutherford, Kaufmann, AR4 etcetcetc).
But, as I believe another banal error needs more attention:
8) Wrong compare.
Imagine for a moment that none of the above mentioned problems 1) – 7) has any impact and then lets just focus on the comparing itself. The data of the proxies suffer from 2 impacts:
A) “Technical averaging” – Impact of many series of date summarized.
Check out what happens when summarizing many datasets of temperatures, an example, the cooling episode 8200 years ago:
Fig 2.
Data taken from: http://wattsupwiththat.com/2009/04/11/making-holocene-spaghetti-sauce-by-proxy/
The white graph with the red squares are the resulting average graph: More temperature sets added together tends to flatten the average. Notice for example how many datasets certainly has a down peak between 8000 and 9000 years ago, but the timing for these datasets are slightly off, and so the down peak is almost gone.
So, to some degree we can expect multi proxies to yield an averaged overall graph.
B) “Direct averaging” – on top of the technical averaging, the data series are often averaged further to some degree using 30, 40 and 50 years Gaussian filters.
The result of averaging by A) and B) is, that the variability of the IPCC graphs on a decadal ´timescale are limited to just tenths of a degree K. But in reality, if there where any real temperature peaks on decadal time scale in the Medieval period, we will would not see these much in the typical data series IPCC shows.
Is this a problem?
Well, it certainly becomes a problem if these “super averaged” data are compared with data that is NOT quite as “super averaged”. And this faulty compare is just what IPCC do.
IPCC “Super averaged” data from proxies, are typically compared to “Observed” temperatures, that is, recent temperatures not at all submitted to the same degree of averaging.
Technical averaging – type A) – is to some degree not happening for observed temperatures, so how about type B), the direct averaging, filtering?
Well, For the IPCC graphis shown in fig 1 above, the IPCC text says: “All series were smoothed with a 40-year Hamming-weights lowpass filter, with boundary constraints imposed by padding the series with its mean values during the first and last 25 years.”
Explanation: If your data ends in year 2000, then the last genuine 40-year averaged/filtered point on the graph would be a point for 1980 with average of 1960-2000 near +0,2K anomaly. But the IPCC graph for observed temperatures ends at +0,43 K around year 2000. This more resembles the normal five years average of GISS year 2000 data:
Fig 3. Giss temperatures illustrated in year 2001.
So for IPCC/Mann etc. to get a year 2000 temperature as high as +0,43K, they must have used just normal 5 yr avg. A longer average period would yield lower temperature for the last year.
So, when IPCC wrote “with boundary constraints imposed by padding the series with its mean values during the first and last 25 years.” – they mean: “We don’t use 40 year average/filter in the last 25 years…!”
So the bottom line is: IPCC compares “super averaged” temperatures of the medieval period with a peak in modern temperatures only submitted to 5 years average.
IPCC basically compares a peak in temperatures in recent years with super averaged medieval data where peaks are more suppressed to conclude how much it is warmer today than in the MWP.
This is a problem !
From this illustration it appears that the peak after 1998 to some degree appears related to the big El Nino 1998 peak, here from appinsys:
Fig 4.
So, where there no El Nino peaks in the medieval period that could have affected the compare with recent temperatures? Yes, there where: http://co2science.org/articles/V12/N5/C2.php
So we have every reason to believe that there where also temperature peaks in the medieval period – peaks that just might resemble the recent El Nino Peak.
So no excuse for the IPCC to compare a modern temperature peak with medieval average temperatures.
This is banal, of course, and even IPCC must have been aware of this, one should think.
Here: An illustration where the single year 2004 for observed temperature data explicitly is used in comparison with the super averaged medieval temperature data.
Fig 5. (from here)
Cheers!
Figure 5 is from Wikipedia, not the IPCC or a peer-reviewed scientific publication. The data used to construct the lines has been smoothed with a 5-year Gaussian filter, so the 2004 datapoint technically shouldn’t be plotted on the same graph with smoothed data, unless it has been smoothed also. However, we all know that temperature in the past decade hasn’t risen appreciably, so the distortion introduced included unsmoothed data with smoothed data probably isn’t worth complaining about.
The problem with Figure 2 is that it contains no information about uncertainty in the time coordinate. If the data is +/-500 years, then the troughs could coincide. If the data is +/- 50 years, then the troughs can’t overlap (unless a systematic dating error occurred, which is difficult to detect). On the other hand, these lines may represent warming and cooling in different geographic regions of the globe as the last Ice Age ended. In the absence of other evidence, there is no reason to assume that all temperature trends around the globe must move synchronously.
I agree that the instrumental temperature data in Figure 1 doesn’t look like it has been subjected to a 40 year filter with ends of series padded with the mean of the previous 25 years. It looks like it has been smoothed by a method which continues the trend (reflection). Unfortunately, the instrumental data Mann used is for only the Northern Hemisphere and your Figure 3 is for Global Temperature.
There is a huge problem with Figure 1 that was identified by von Storch. http://www.sciencemag.org/cgi/content/abstract/306/5696/679
Von Storch created a millennium of temperature data with a computer model and then created artificial proxy data (tree ring) from that temperature data. Then he added no noise or realistic levels of noise to the proxy data before analyzing it with Mann’s method. He found that the amplitude of the natural variations in the reconstructed temperature was reduced by a factor of 2 (no noise) to 4 (realistic noise) compared with the original data. This explains why the shaft of the original hockey stick is so straight with no trace of an MWP or LIA. There is absolutely no justification for plotting instrumental temperature (with full variation) on the same graph as reconstructed temperature (with suppressed variation). Reconstructions done since von Storch have been done with alternative methods that preserve the amplitude of natural variation.
Frank–the geologic evidence for the MWP and LIA has an extensive literature that has been around for decades. It shows up especially well in the glacial record, which has been well documented by former glacier margins, pollen records from peat bogs, isotope measurements from ice cores, tree rings (not the kind that Mann et al. use!), historic records, and on and on. It’s so well established that geology classes for decades have taught it as beyond any reasonable doubt.
Don
Don Easterbrook (07:48:29) :
When geologists first saw the Mann et al. curve, we all just laughed because of the solid geological evidence for the Medieval Warm Period and Little Age published in hundreds of papers for decades. Our conclusion was that either the trees that Mann and others used were not sensitive enough to record climate changes or else it was a total fraud. The Climategate emails showed us the answer to that question. Instead of endless arguing over the details of their bogus curves, it would make more sense to just go to the geologic evidence which shows beyond reasonable doubt the Mann et al. curves are worthless.
”
This comment i find very interesting indeed. I recently here on WUWT made an analysis of MWP temperature results. I compared results before and after IPCC changed opinion in 2001, and found a huge difference in results before and after 2001 when IPCC published the Mann graph:
http://wattsupwiththat.com/2010/03/10/when-the-ipcc-disappeared-the-medieval-warm-period/
Don Easterbrook, you here confirm that we had a consensus PRO a warmer MWP. If you can add any information on this issue I would be very interested.
The thing is, if IPCC in 2001 acted against the consensus back then, this is one of the strongest signals, that IPCC has an agenda that is not entirely scientific.
Is it possible to “prove” that we had a solid MWP-consensus until year 2000?
K.R. Frank Lansner
Speaking of Dr. Easterbrook, he provided an update to our interview of two years ago.
Enjoy…
http://www.gather.com/viewArticle.action?articleId=281474977336370
Ralph (12:06:07) :
P.S. Note to mods – ‘effect’ is the noun and ‘affect’ is the verb, you had it A over T.
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At the risk of making a fool of myself, and to defend the mods, I will wade into the tangled issue of effect vs affect.
Effect is both a verb and a noun: as a verb it denotes the activity of getting something done: “Through his strenuous activity he effected the appropriate transformations…” As a noun it denotes the results of some action: “The effects of the storm were devastating”.
Affect is also both a verb and a noun. As a verb it has several meanings: one indicates putting on a false front or projecting an emotion: eg: “He affected surprise at the results.” It also indicates an emotion induced in the recipient: “The accusation of lying affected her deeply.” Also, as a verb it can indicate that there were consequences to an action or event: “The hail affected the crops.” As a noun affect is used in psychology to talk about the affects of mental illness. Since the use of affect as a noun is more obscure, it is probably safer to argue that affect is primarily a verb.
mike roddy (11:19:46) :
“I stand by my prior comments.
The notion that mathematicians (McIntyre) weathermen (Watts, Bastardi) or economists (Lomborg) understand data better than the climatologists who developed it makes no sense whatsoever. Developing temperature reconstructions requires a lot more than knowledge of algebra. ect….”
Mike, you’re almost there!!! You’re correct, I suppose temp reconstructions do require more knowledge than base algebra. However, you can’t get to temp reconstructions without properly applying algebra, especially in regards to averaging and understanding what a set and a subset is. That is the beauty of mathematics. The rules and laws that govern math don’t change, regardless of the desire of the outcome.
Do you even bother to consider the implications of hiding the decline? IT MEANS IT DOESN’T MATCH!!! They found one particular point in time where they could “meld” the lines together to make them appear as one. (now think of sets and subsets)
Turns out, the chemistry and physics properties of mercury are not related to the biological and botanic properties of tree rings. So, and I’m going out on a limb here, but I don’t believe they belong in the same graph, much less on the SAME LINE!!! Strange, I know, but there it is.
OT, but a masterpiece written by the ever formidable Mike Roddy:
http://www.buffalobeast.com/?p=1237
gt (18:49:39)
Thank you for blowing Mike out of the water with that link.
In the light of his emotional committment we cannot take anything he says as a serious attempt to understand the science.
Stephen Wilde (00:27:47) :
gt (18:49:39)
Thank you for blowing Mike out of the water with that link.
I’ll echo that.
Mr. Roddy’s evidently never been much a fan of reasoned dialogue…
mike roddy (08:39:54) :
“IPCC compared average temperatures for MWP and the present, not an average in one case and a peak in another. Your claim here lacks merit.
“On a more general note, you are asking us to believe temperature reconstructions put together by amateurs, rather than the ones carefully developed and peer reviewed by hundreds of specialists at NOAA, NASA, CRU, and others. It’s beside the point that your data is not correct. It is unworthy of consideration.
“Historical temperature reconstruction, including those for recent decades, is a highly technical and detailed process, requiring extensive training. Questioning the basic expertise and integrity of those who develop these global temperature charts for international organizations is not credible, and is unsupported by actual scientific evidence.”
—…—…
Rather, and what is actually true, is the following:
On a more general note, you are asking us to believe temperature reconstructions put together by amateurs, rather than the ones carefully developed and peer reviewed by hundreds of specialists at NOAA, NASA, CRU, and others. It’s entirely to the point that their data and their conclusions are not correct. They are unworthy of consideration at any level by any organization.
Historical temperature reconstruction, including those for recent decades, is a highly technical and detailed process, requiring extensive training and an open review policy rather than the amateurish, technically flawed and totally undocumented biased methods of the few so-called specialists in propaganda at NOAA, NASA, CRU, and others..
Questioning the basic expertise and integrity of those who develop these global temperature charts for international organizations is essential – because they are attempting to use their biases and propaganda to control the world’s energy supplies and economic policies to the harm of all, and their biases and illogical fallacies are completely unsupported by actual scientific evidence.
One more thing:
When you use 40-year filterup to 1975, then the temperature peak around 1940 is seriously suppressed.
Both before and after 1930-40 peak temperatures where considderably lower, and thus the 40-year filter has indeed done the job to : HIDE THE DECLINE
And perhaps this was indeed Mike´s Nature trick? To hide the decline?
Then after 1975, peak can be seen since no 40-yr filter applied.
“there where” should be “there were”
“where there..?” should be “were there…?”