by Steve McIntyre
For the benefit of new readers, we discussed some aspects of the “trick” at Climate Audit in the past. Obviously, the Climategate Letters clarify many things that were murky in the past. On the left is a blowup of IPCC 2001 Fig 2.21 showing where the Briffa reconstruction (green) ends. More on this below.
Figure 1 below is the original graphic showing the MBH98-99, Jones et al 1998 and Briffa 2000 temperature reconstructions. I think that it’s fair to say that this graphic gives a strong rhetorical impression of the proxy reconstructions all going up throughout the 20th century, lending credibility to the idea that the “proxy” reconstructions would also be responsive to past warm periods – and obviously not giving any “fodder to the skeptics” by revealing the divergence between the Briffa reconstruction and temperatures.
Figure 1. IPCC 2001 Comparison of warm-season (Jones et al., 1998) and annual mean (Mann et al., 1998, 1999) multi-proxy-based and warm season tree-ring-based (Briffa, 2000) millennial Northern Hemisphere temperature reconstructions. The recent instrumental annual mean Northern Hemisphere temperature record to 1999 is shown for comparison.
While the digital version of the Briffa reconstruction has only become available in the past few days, Briffa 2000 (cited in the caption to IPCC Fig 2.21) did show the decline as shown in Briffa 2000 Figure 5 shown below (with its original caption). This series obviously goes down at the end (as does a related series in Briffa et al 1998, referred to by Gavin Schmidt.) What Gavin didn’t discuss is how you get from the version below to the IPCC version.
Figure 2. Briffa 2000 Figure 5 An indication of growing season temperature changes across the whole of the northern boreal forest. The histogram indicates yearly averages of maximum ring density at nearly 400 sites around the globe, with the upper curve highlighting multidecadal temperature changes… The LFD curve indicates low-frequency density changes produced by processing the original data in a manner designed to preserve long-timescale temperature signals (Briffa et al., 1998c). Note the recent disparity in density and measured temperatures discussed in Briffa et al., 1998a, 1999b). Note that the right hand axis scale refers only to the high-frequency density data.
Gavin Schmidt stated that everything was “in plain sight”. Regular CA readers are used to watching the pea under the thimble. There is no mention in the IPCC report of the deletion of Briffa reconstruction data after 1960. Nor is there any mention of the deletion in the IPCC reference (Briffa 2000) nor, for that matter, in the article cited by Gavin Schmidt (Briffa et al 1998). These articles report the divergence, but do not delete it. (Briffa et al 2001 does delete the post-1960 values.)
Not only was the deletion of post-1960 values not reported by IPCC, as Gavin Schmidt implies, it is not all that easy to notice that the Briffa reconstruction ends around 1960. As the figure is drawn, the 1960 endpoint of the Briffa reconstruction is located underneath other series; even an attentive reader easily missed the fact that no values are shown after 1960. The decline is not “hidden in plain view”; it is “hidden” plain and simple.
Figure 3. Blowup of IPCC Figure 2-21.
Previous discussion of these issues is at Climate Audit here here here and more recently by Jean S here. Jean S and UC report at CA that the puzzling end point properties can be replicated by replacing actual proxy data after 1960 with instrumental data and then smoothing (truncating back to 1960) – exacerbating the problem. (I haven’t personally confirmed this, but Jean S and UC are extraordinarily skilled analysts and know this material as well as I do.) Jean S:
In order to smooth those time series one needs to “pad” the series beyond the end time, and no matter what method one uses, this leads to a smoothed graph pointing downwards in the end whereas the smoothed instrumental series is pointing upwards — a divergence. So Mann’s solution was to use the instrumental record for padding, which changes the smoothed series to point upwards as clearly seen in UC’s figure (violet original, green without “Mike’s Nature trick”).
Jean S then drolly quoted Mann:
No researchers in this field have ever, to our knowledge, “grafted the thermometer record onto” any reconstruction. It is somewhat disappointing to find this specious claim (which we usually find originating from industry-funded climate disinformation websites) appearing in this forum.
The Climategate Letters contain a very interesting discussion between Mann, Jones, Briffa, Karl and Folland worrying that showing the discrepancy would provide “fodder to the skeptics”. More on this tomorrow.
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“Briffa 2000 Figure 5 An indication of growing season temperature changes across the whole of the northern boreal forest. The histogram indicates yearly averages of maximum ring density at nearly 400 sites around the globe, with the upper curve highlighting multidecadal temperature changes…”
They selected 1-3 trees that fit the dogma. No random sample technique in this shoddy experiment. They also loaded or weighted the correlations in their fortran formula. Enron style reporting. Enron did not report liabilities. These people didn’t report warm temps.
They “padded” the numbers
Am I just a purist, or is all this Climate “science” absolute pure junk? It’s like plotting everyone’s social security number or driver’s license numbers, averaging them and adding colors to the graph at the end. (And being paid trillions of dollars for the effort!)
I strongly recommend the book The Long Summer by Brian Fagan to anyone who wants a qualitative reality check on past temperature changes. Global temperatures may or may not have remained largely constant but climate has undergone gross changes over large areas for centuries at a time – changes that would affect any tree rings.
I particularly like the picture on page 193 of the book which I can only describe. It shows the position of the northern edge (ecotone) of the Mediterranean climate zone in Europe/North Africa from 1200 BC to 900 AD. North of this zone has UK style temperatures – cool and wet. The ecotone changed position, running through Sicily and the middle of the Mediterranean from 1200 to 300 BC, as far north as the north coast of France and Germany from 300 BC to 300 AD, and then as far south as the north coast of Africa from 500 AD to 900 AD. The Roman Empire waxed and waned with extent of the Mediterranean climate zone and ended in the Dark Ages.
The hockey stick gang have never shown any apparent awareness of the huge amount of archaeological and other evidence in favor of a constantly changing climate.
dfbaskwill (07:04:40) :
Am I just a purist, or is all this Climate “science” absolute pure junk?
Is it junk?
Using tree rings is more like palm reading and astrology. The African Deserts and the massive asian deserts are excluded. Antartica offers no tree ring data. We know there are several variables that influence tree growth. Why not use whale blubber thickness instead of temp readings for the Pacific Decadal Osscilation readings?
What I see in this mess-we have thrown Billions at a non-problem, or at the very least a minor one, when there are other more pressing problems. People and Children dying due to disease, lack of sanitation etc. Yet the Kleptocrats of the U.N. want US to be poorer and colder too….
dfbaskwill (07:04:40) :
Am I just a purist, or is all this Climate “science” absolute pure junk?
YES.
In plain sight?
In some places such tricks are called false advertising.
OT
Here we go again.
http://www.telegraph.co.uk/topics/weather/6672631/British-winter-to-be-milder-says-Met.html
dfbaskwill: “Pure junk” … all of this work is an attempt to create a mathematical model that “matches” the observed data in such a way that it has predictive power into the future. That is the idea at least. What actually happened is that these folks are paid through grant funding to come up with a pre-determined conclusion. You see, grants are awarded to accomplish certain things. I have written grants and won grant funding so I have experience with them. The predetermined conclusion is “Show evidence of human-caused global warming”. So, off they go. It’s not “trillions” of dollars however, but enough for a comfortable living.
Anthropogenic Global Warming Virus Alert
http://www.thespoof.com/news/spoof.cfm?headline=s5i64103
The errors introduced from all of these “reconstructions” indicate such a large range how could any conclusion be drawn from the large amount of data attempted to show the entirety of the earth’s system or systems?
The scientific community needs to air their dirty laundry and expose this fraud for what it is. The IPCC should take responsibility and push the reset button for the world has been scammed by the political class.
I’ve been following with great interest this last week since FOI2009 was set free and I’ve read many opinions and comments re the whole sorry affair. I won’t even begin to properly understand it all in the scientific sense but I wonder will anything change or is the AGW super tanker going to be too far advanced to be stopped? What’s likely to actually happen?
OT but important:
The science museum poll: http://www.sciencemuseum.org.uk/proveit.aspx
It was 5360 for, 7831 against three hours ago
it is 5370 for 7833 against now
Seems that skeptics have stopped taking the poll, or that schoolchildren are urged to enthusiastically support it. With the hits this blog is getting nowadays, maybe some people who were not aware of the poll would like to go and vote.
But we’re told “trick” was just a colloquialism used between scientists exchanging views. I’m very confused. Why do the facts disagree with what these climate scientists say?
I see the Met Office are pinning their hopes on another mild winter for the UK. Best go get myself an extra thick winter coat then.
As requested, I’ve put together a YouTube version of the ClimateGate Who’s Who video. You can find it here:
I suspect Steve M has missed part of the trick.
The full caption in IPCC is and note very carefully the last sentence which should be read whilst keeping in mind Prof. Jones public statement after the leak.
“Figure 2.21: Comparison of warm-season (Jones et al., 1998) and annual mean (Mann et al., 1998, 1999) multi-proxy-based and warm season tree-ring-based (Briffa, 2000) millennial Northern Hemisphere temperature reconstructions. The recent instrumental annual mean Northern Hemisphere temperature record to 1999 is shown for comparison. Also shown is an extra-tropical sampling of the Mann et al. (1999) temperature pattern reconstructions more directly comparable in its latitudinal sampling to the Jones et al. series. The self-consistently estimated two standard error limits (shaded region) for the smoothed Mann et al. (1999) series are shown. The horizontal zero line denotes the 1961 to 1990 reference period mean temperature. 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.”
http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/069.htm
That last sentence grossly under-specifies the data processing method and leaves large questions on what precisely was done and to what. This includes the short dataset problem.
According to the Jones statement (in WUWT article) after being caught red handed, it was a 50 year filter on the 1000 year data series but he omitted to say what was done to the instrumental data. Was it processed the same or wasn’t it?
Was the 25 years mentioned above applied to 1961 – 1998 or to 1880 – 1998 or not at all, what zero, how long a filter and so on.
Is this critical? Yes very.
I cannot see how sensible filtering of the instrumental temperature data can lead to such a high data point for 1998 based on data up to 1998.
The effect of fully working low pass filtering is a massive reduction in the amplitude of fast data movement.
Honesty demands the same processing on all data.
Try it. It’s worse than we thought.
It might help to create an illustration of the trick “in action”, with both the padded data and the original data at the end, and the smoothing window centered on the truncation point, and the two different smoothed graphs produced. No need to show it for all the graphs in Figure 1, a single one will suffice. Also, it would be better to just show the 20th century only.
The point to get across is that smoothing caused the false data to spill over into the real proxy data before the truncation point.
Don’t mean to order anyone around, would do it myself if I had the data…
Re: the choice of green as the colour representing the “amended” data. A chance this is deliberate? A fair number of people are red-green colour blind and would thus be unable to distinguish this line from the red one. Just a thought.
There was a letter to the editor (Nature, I think) a few years ago lamenting the choice of colours used in conference presentation graphics that made it really difficult for people with colour-blinded to tell what was going on. They also provided a link to a site with a pdf and a PowerPoint presentation that demonstrates how to get around it (what kinds of colours are best). It opened my eyes to this issue.
The Mann’s image comes to mind where he is hugging the tree ring. Except this time he is chewing the edges of the tree ring, “hide the decline”.
Mann said that during the Medieval Warm Period some parts of the world are as warm as today while other parts are cooler. Yet tree rings in an area like Yamal are used as a proxy to help calculate past temperatures.
Am I seeing this correctly? What gives?
From the UK Daily Telegraph:
http://www.telegraph.co.uk/earth/copenhagen-climate-change-confe/6672875/Whos-to-blame-for-Climategate.html
I’m happy to go with the Met Office forecast of a “milder than average” winter which, readers will note, they are ascribing to an El NIno event. Let’s wait and see, shall we? If El Nino does develop and the European winter does turn out to be above average, am I allowed to shoot the first warm-monger who tells me it is due to “climate change”, please?
The science museum poll: http://www.sciencemuseum.org.uk/proveit.aspx
It was 5360 for, 7831 against three hours ago
it is 5370 for 7833 against now
– Anna I suspect the votes for have been adjusted to show the variance that should be there, say fudge it by artificially adding an extra vote for every real vote based on what they assume should be happening. They have to hide the decline! after all it would be a travisty if the real results didn’t back them up!
” is the AGW super tanker going to be too far advanced to be stopped?”
Years ago there was a huge passenger ship that was deemed to be unsinkable. It was named the Titanic.
@David S
I hope in my heart that the truth will out but twenty years have gone into this AGW theory….
The Titanic DID sink and I hope this leak has holed the vessel terminally……..
@ur momisugly Lee (07:31:24)
I think you are on to a very good political question. We cannot hope to get satisfaction in this area because politics is not about truth, but persuasion. However, science is supposed to be a search for truth, and I will be satisfied if this perversion of science by Mann, Jones, et al is exposed and prosecuted within the scientific community. For the sake of the integrity of science, these charlatans should have their reputations and credibility decisively revoked.
Politically speaking, the AGW train left the station years ago with science playing the role of a useful fool. Science will not derail this train. Only politics will, in my view.