The very first sentence of the Marcott et al (which is getting heavy press) abstract says:
Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time.
Okay, let’s have a look at the claim. First this graph from the publication:
![marcott-A-1000[1]](http://wattsupwiththat.files.wordpress.com/2013/03/marcott-a-10001.jpg?quality=83)
Seems reasonable when you look at that data, right? But let us examine a well known reconstruction from GISP2 ice core data in Greenland. Here’s a section from Dr. Richard Alley’s reconstruction:
Now here is a simple scaling of the Marcott et al graph to get an approximate match for the temperature and time scales:
Note that this is just a simple visual comparison, with a rough match of the data for time and temperature scales – it isn’t intended to be anything else.
The full un-cropped Alley GISP2 plot can be seen below:
In my overlay above, the Marcott et al graph full time scale on the x axis is 2000 years, and its temperature full scale on the y axis is two degrees C. The scaled overlay to the Alley GISP2 plot is a reasonably close match to the GISP2 plot scale units. The centerlines don’t match, but they can’t with this sort of comparison.
The idea here is simply to compare magnitudes of the data on the same time scale.
Clearly, the GISP2 data has greater magnitudes in the past 1500 years, and at longer time scales, the GISP2 temperature reconstruction dwarfs the magnitude of the Marcott et al temperature reconstruction. Dr. Don Easterbrook has a good synopsis of GISP 2 temperature reconstruction magnitude on WUWT here.
This simple visual comparison suggests that their “unprecedented” claim for the 1500 years BP is unlikely to hold up when examined against other reconstructions. As they say in the big leagues, more study is needed.
Marcott et al alludes to the warmer temperatures of the past in this paragraph:
Our results indicate that global mean temperature for the decade 2000–2009 (34) has not yet exceeded the warmest temperatures of the early Holocene (5000 to 10,000 yr B.P.). These temperatures are, however, warmer than 82% of the Holocene distribution as represented by the Standard5×5 stack, or 72% after making plausible corrections for inherent smoothing of the high frequencies in the stack (6) (Fig. 3). In contrast, the decadal mean global temperature of the early 20th century (1900–1909) was cooler than >95% of the Holocene distribution under both the Standard5×5 and high-frequency corrected scenarios.
Perhaps this weekend when I have more time, either I can do a proper plot of the data in a similar fashion to see how well they match when plotted side-by-side in the 1500 year time frame. Unfortunately I have other work to do today, so I can’t at the moment, and I’m traveling again tomorrow. Posting will be light.
A couple of things:
1. How long have thermometers, accurate to 0.5 degrees, been available? Less than 150 years?
EVERYTHING before that is proxy / assumed data.
2. Is there ANY data, proxy or otherwise, that takes into account continental drift / tectonics in general?
3. Has Greenland ALWAYS been where it currently sits?
4. Has the Gulf Stream ALWAYS flowed the way it is supposed to?
5. Has Antarctica ALWAYS been where it now is and permanently covered in ice and snow? NO is the correct answer to both of those. Ditto Australia.
6. What was the “climate” when Africa and South America were actually joined together?
7. Did sunstroke kill all the wooly mammoths in Siberia?
Caleb says:
March 8, 2013 at 1:47 pm
“It is as if you came out with a paper that said that George Washington didn’t exist ”
And George, of course, does exist:
http://ncwpics.com/ncw/wp-content/gallery/george/george-619-014.jpg
I couldn’t resist. It has been a long week.
bmcburney says:
March 8, 2013 at 3:32 pm
“So, contrary to his publicity package, it is not the case that Marcott has proven that current temps are unprecedented in the last 11k years. Rather, Marcott has shown only that IF present temps continue for another hundred years THAT event would be unprecedented in past 11k years.”
You write: “IF present temps continue” . . .
. . . but I think you mean something else. Maybe referring to the rate of increase, say from 1976 to 1998, or at the rate proposed in one of the scenarios produced by the UN IPCC. It is my understanding that at the present time (16 or so recent years) the global average temperature is not rising.
Other than that, I had the same thought you have expressed.
Sorry but the graphs overlaid as such in nonsense.
To be true, the “Science” report’s period for computing the ‘anomaly’ is nonsense, i.e. the
thundering herd of “Human” ‘Global’ ‘warming chooses their ‘anomaly period’ as is needed
to generate what they desperately need in their minds to be perceived by the general public
in order to generate ‘hysteria’ among the general public.
The whole exercise of “Human” “at the center of the Universe” ‘Global’ warming, from a cherry
picked set of 73 locations, is nonsense.
Time to bailout of AAAS subscription and membership: same goes for the AGU (i.e. Its no
longer about Geophysics at all).
Clearly what we are arguing about are the following:
1. The validity of the ‘proxies’ used in the new study.
2. The global coverage of those proxies.
3. Whether Greenland data matches world data, assuming the proxies used for that to be accurate?
What can, however, be seen, from the Greenland data is that a 1.5 – 2.0C rise in rapid time can occur, followed by an equally rapid descent some years later.
The caterwauling alarmists never seem to discuss that, do they?
Boring, Watts you compare apple with pears. If you take GIPS2 you have to compare not Globally, you have to look @ur momisugly 30N-90N-Stack of this Studie. You looked there, you can see the actual temperature of 30N-90N is nearly 1K lower that Holocene-Max.
Now, dont forget arctical aplification of warmin/cooling
In this sence, the Studie ist plausibel
Also should be notet, that we the last couple years have claim the Minoan-Warming
http://wattsupwiththat.com/2011/11/10/new-study-shows-temperature-in-greenland-significantly-warmer-than-present-several-times-in-the-last-4000-years/
Bill Illis says:
March 8, 2013 at 5:17 pm
Funny they didn’t use the famous GISP2 temperature proxy. Famous that is.
You know what, only 1 of the proxies used (out of 73 of them) show anything like the 0.6C spike at the end of the chart (which is 1940).
Theonly proxy which has this is Agassiz-Renland ice cores (dO18 calibrated to borehole thermometry again).
So, this reminds me of the 1 tree in Briffa’s reconstruction.
Its like I said, this is from Oregon State University. So the more you look, the more of this you will find.
So basically marcott has data points once every 150 years and them compares a temperature record of 100 years to this? Anyone else see the issue there? It is physically impossible to do that. The entire statement of unprecedented warming is just retarded.
Has anyone else noticed that in the plots where Mann 2008 is overlaid on the new reconstruction, the high-frequency noise in the line jumps up exactly at the start of the overlay? Could Mann 08 have been the actual ‘secret ingredient’ in the proxy roster that creates the end-spike?
That’s pure speculation – I don’t know. Perhaps someone with access to the paywalled part could see if it’s mentioned?
Same data? check.
Same playing with error bars? check.
Same manipulation of recent record? check.
If you divide the daily sunspot numbers by 90 and then subtract it from the CET daily maximum, the period from 1897 to 1997 has a flat trendline. Or you can divide the yearly total by 32000 and subtract it from the yearly maximum temperature for the same result.
It pains me to see how you overlay plots incorrectly. Ugh.
You are comparing regional (greenland temps) to a global average temperature reconstruction. This is inherently wrong. You should explicitly explain this to your devoted fans who may think what you’ve done is correct. If, say, we had a bunch of publications discussing temperatures in Chicago vs. Florida vs. global averages. Each was by a different author. Would it be accurate to compare all of the temperatures and then say the author’s must be lying because see how they disagree.
@youarewrongagain, using many proxies means that there are a lot of data that will cancel out each other. That is why GISP2 data are moving so wild compared to the bundle of datasets of the underlying study. Adding a pike of measured temperatures at the end is the finishing touch for another hockeystick. Nullius in Verba, you are right.
@ur momisugly Bruce, spreading at the mid Atlantic ridge is about 4cm/y, so you can calculate that for the period of let’s say the last glaciation that ended 12,000 years ago, Greenland must have shifted longitudinally by 240m from the ridge center during this period. As for Australia, Antarctica, even if the East Pacific Ridge spreading is faster around 15cm/y, here again the change of respective positions during the period would be negligible.
“You are comparing regional (greenland temps) to a global average temperature reconstruction.”
Yes, and that’s exactly the sort of comparison that should be made in order to understand what is going on. People are aware of certain previous reports about the Holocene Optimum, when new information comes along that appears inconsistent with it, you investigate. First you isolate the point of apparent conflict. You check the data. You check the sources. You find out exactly what it means, how it was processed, what it assumes, what its error bars look like, you find out how they were calculated, you consider other data sets, other hypotheses, and you keep digging until you get a satisfactory explanation.
That might result in discovering a flaw in the new information, or you might discover a flaw in your old information, or you might find out that you had previously misunderstood one or both and the appearance of a conflict is expalinable. Any way it goes, you make progress.
As you say, a global average is not the same as a local average. But the fact that the two can be so different implies that the behaviour is not uniform globally, which is an interesting new fact you have learnt. It reminds you that global averages don’t tell you anything about local climate changes, which is where people directly experience it. It opens up new questions, like where did the warming occur, and how can you get drastic warming in one place and none at all in another, and are the proxies really reporting temperature reliably, and what does the averaging process do to the fine details, and what does it mean for all the high-frequency details to be lost, and is it valid to mix data with different frequency behaviours in different parts of the record?
As a result of asking such questions, we now know that many of the assembled proxies don’t show any temperature change over the Holocene, that if these are accurate that the global average was smaller than the local effects in many places, that the up-tick at the end appears to be some sort of illegitimate splice of modern Mannean data that doesn’t appear in any of the 73 proxies. It isn’t a confirmation of Mann’s hockeystick if it includes Mann’s hockeystick as an input. It isn’t a confirmation that either the size or speed of the modern peak is unprecedented if any such spikes and peaks would be smoothed out. It isn’t evidence that local climate changes – the sort people will actually experience – are or will be unprecedented when global is so different to local.
But it is quite true, as we’ve said several times now, that the disagreement of the average with the individual contributors like Greenland isn’t an inconsistency or error – not that Anthony said anywhere that it was; in fact he cautioned against jumping to conclusions.
Now see if you can find any of those media sources who said this showed global warming is unprecedented in 11,300 years acknowledging any of their errors.
fascinating to compare with David Stockwell’s 2006 article on generating hockey sticks from time series with red noise: (h/t Shub at BH for the link)
Reconstruction of past climate using
series with red noise, David Stockwell, March 2006
See the non-empirical hockey stick graph at Stockwell’s article linked above….. it’s a statistical artifact, like the fundamental uber-graphic for all hockey sticks of certain methodologies…. Stockwell says it’s basically encoded into the statistical treatment of proxies (unless presumably better care is taken to avoid biasing the results).
And then, there’s the large, unshielded, somewhat erratic, fusion reactor around which the planet appears to orbit.
Bruce says:
March 10, 2013 at 2:55 pm
And then, there’s the large, unshielded, somewhat erratic, fusion reactor around which the planet appears to orbit.
No, Bruce, that fusion reactor is extremely stable.
On the one hand we have statements by the foremost Scientific Organizations in the World, including the AAAS, the NAS, American Meteorological Society and the American GeoPhysical Union that the evidence for Anthropogenic Climate Change is compelling and that there is a scientific consensus; in this forum we have many strong statements claiming it’s bunk. A Science article reports 13950 peer-reviewed articles support the Scientific consensus, 0.17% raise some question about it’s validity. It doesn’t seem the deniers have science on their side.
Warren,
The IPCC is a political organization not a scientific organization and their job is to sell MMGW to The World. The problems started with Michael Mann’s “Hockeystick” Graph which is sheer rubbish but because it threatened a disaster the newspapers rubbed theirs hands with glee and duly kicked of the Mannmade Global Warming scam. Don’t underestimate the effect of a media campaign.
We are still recovering from the Little Ice Age and the temperature has been going up steadily for approx 200 years (and could continue for some years more).
Looking backwards for the last 2500 years we had the:
* Little Ice Age ~(1550-1850 AD)
* Medieval Warm Period ~(950-1250 AD)
* Dark Ages Cool Period ~(700-900 AD)
* Roman Warming Period ~(200 BC-600AD)
See: Temperatures of the Past Six Millennia in Alaska
http://www.nipccreport.org/articles/2011/jan/25jan2011a7.html
However, that does not mean we should carry on as if nothing is happening.
The World will to run out of fossil fuels and all avenues should be explored to find alternatives.
I strongly object to is the way that the IPCC campaign is distorting research funds so that anyone wanting to research a subject that might go against MMGW will be denied grants, and causing millions of dollars to be wasted on Carbon Credit schemes.
However no single temperature record from anywhere can prove or disprove global warming, because the temperature is a local record, and one site is not the whole world
Zctek, are the AAS, NAS, American Meteorological society, and American Geophysical Society all political as well? Is the peer review process that’s yielded 99.8% of 13,950 papers affirming Anthropogenic Climate Change also political? By your standard, we can’t count on relativity, evolution, or in fact, any of today’s Science.
:
Warren, Do you believe that Michael Mann’s “Hockey Stick” is a true representation of the last 2,500 years of temperature/climate? That is the lynch-pin of the IPCC’s policy.
There is a mixture of good and bad science. It is what the IPCC chooses and does with it that’s wrong.
[Try re-writing the comment, while avoiding the deliberate “denier” pejorative insult. Mod]