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.
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The trick is the “filter.”
Seth is propagating the story: http://www.pddnet.com/news/2013/03/recent-heat-spike-unlike-anything-11000-years
Every time I see one of these “studies” I think we have finally reached the pinnacle of stupidity, but then there’s another.
[snip – if you have a valid criticism, post it, snark helps nobody -mod]
Anthony
I think it might be a good idea to look at your “years before present” they look rather out of alignment to me.
Richard
REPLY: That was done for a reason, so that the Y axis scales would both be visible. Note that I said “rough” alignment. – Anthony
Reblogged this on If You Voted For It — You Own It and commented:
Nevada County’s local left is promoting the Marcott etal Study, and this is reblogged is to provided for some perspective for the more rational thinkers.
Now that the original hockey stick graph (and it author) cannot be ignored as anything other than a joke.
We now bring you… the new hockey stick, Hockey stick 2!
I’m assuming Marcott et al are still tacking on the thermometer record for 20th/21st century temperatures. If so, then there is still the apples/oranges comparison of thermometer and paleoclimatoligical records, where the statisical methods used to generate the paleo record wash out the short term variations that the thermometer records captures.
I also cannot see that the error bars 10K years ago will be the same as 500 years ago.
Ooh, look – they’ve got rid of the MWP. Again. Do they really think people will forget if they keep trying that trick?
I posted this on the earlier Marcott thread, but it may be more appropriate here. Apologies.
—
I’ve had a quick look at the data, and it seems to be a mixture of different behaviours.
One set of five series shows a peak around 9k years ago, a dip from 7k-3k and a rise to the present day.
http://i49.tinypic.com/lbogh.jpg
Another set of around thirty five series shows pretty much of nothing. It looks like random noise.
http://i49.tinypic.com/t68r4x.png
And the third set of around twenty series shows the holocene optimum we know, with a peak around 2 C warmer than today.
http://i47.tinypic.com/2uylqh3.png
(There were a few others that didn’t cover a long enough interval to make a proper comparison, I think.)
The ‘Holocene Optimum’ series have been mixed in with a bunch of ‘random noise’ series and some ‘Holocene dip’ series which has the effect of bringing the Holocene peak down to below a degree. All they have to do then is paste the instrumental temperature series on the end. (Note, the end spike is not in any of the 73 series.)
Of course, that might be saying that the Holocene peak did not occur everywhere, and that in many places the temperature didn’t change, which is how they’re interpreting it. You would need to look at the individual data sources to tell.
Whether the Holocene Optimum was global or not, it’s definitiely very naughty to splice on the instrumental record and talk about anything being ‘unprecedented’. The proxy data smooths anything going on at less than 300-3000 years (figure S18 in the SI). Apples and oranges.
I also noted from their map that most of their sites seemed to be on or near the coast. A maritime climate might not necessarily reflect changes in either ocean or continental climates.
This may also be an apples/oranges comparison. IF it is generally true that north-polar temperatures fluctuate more than global averages (as currently appears to be case), then an additional vertical scaling adjustment might need to be applied, even to make a qualitative match, and this would tend to reduce the high temperature fluctuations of the ice core data w.r.t. the global pollen reconstruction. Is there not a comparable global reconstruction over a longer time span that the comparison can be made with?
What might be truly unprecedented is if the Holocene DOES NOT have from 1 to 3 strong thermal excursions right at it’s typical 1/2 precession age end.
http://wattsupwiththat.com/2012/03/16/the-end-holocene-or-how-to-make-out-like-a-madoff-climate-change-insurer/
The way temperatures have been “homogenized” in the past 100 years (do I hear a “model” echo?), they can’t honestly be compared to deterministic temperatures from ice cores. That’s like comparing apples and oranges.
So Marcott is right–his bunch of CAGWs only look at models and their models are designed to show that the last 100 years have the largest spike. I’m glad he took the time to tell us.
Marcott should have added that caveate to his statement; had he looked at the Ice Core data (which some alledge is smeared by diffusion so it’s undoubtedly less pronounced that reality), such a daring accuasation couldn’t have been made.
(How dare any of you look at anything but models…)
When is ‘present’? The acronym BP [before present] normally means before 1950 so that the time axis stays fixed.
“if you have a valid criticism, post it, snark helps nobody -mod”
One study compares local temperature response at an acknowledged labile location (Greenland).
The other study compares global temperature response.
Apples and oranges.
Then again (to his credit) Mr. Watts stated:
” 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.”
It is a rough match of data measuring 2 different metrics which would be expected to be different.
Seth’s article is everywhere, as opposed to the report, which is behind a paywall. So, this comment is informed by the former. They claim that the dramatic turnaround in temperature began about 100 years ago, which inspired two thoughts.
One is that temperature was amazingly sensitive to CO2 concentration, but became much less so as time went on. (Interesting physics) Two is that it’s a good thing the industrial revolution halted the increasingly rapid slide into the next ice age. Maybe Watt saved civilization
The last datapoint of the Alley data is 1855, there’s been some warming since then.
Both could be right.
GIPS2 is a history from one location with a couple of proxies for temp.
Marcott uses one or more different proxies, from 73 ice and sediment core monitoring sites around the world [Exactly how much overlap in time between site samples? How noisy are the proxies?]
It might be a better representation than a Greenland ice core. In fact, it ought to be better. Whether it really is better is the open question. Mann sampled from more than one location, too, but the proxy is very noisy and the sample weighting preposterous.
Marcott may have done better, but getting a pay-walled paper in just under the wire for IPCC AR5 does not add to the paper’s credibility.
You do know that a number of Greenland ice cores are among the proxies used by Marcott et al, right? Its not that surprising that localized variability (especially in high-latitude areas) would be much higher than in global reconstructions.
utterly misses the point.
1. The Marcott analysis has a time resolution of around a century.
2. The marcott analysis is “global”
The ice core has much better resolution. That means it has a better chance of picking up high frequency variation. marcotts proxies are basically “smooths”
As an analogy if you took an average of say san francisco over a year suppose you had an answer of 55F on an annual basis. Then somebody came along and said “Hey on labor day it was 75!!!. well DUH!, one is a annual smooth and the other is a high frequency spike
For the spatial issue, imagine Anthony Posted CRN average for the US and said “the average was 76F” and imagine some warmist said ‘ hey, it was 95F in new mexico”
in both cases the person who cites higher frequency data to counter lower frequency claims is really OFF TOPIC. and the person points to high temps in new mexico to counter Anthony’s claims about a US average is also OFF topic.
In short. you cannot refute a spatial average ( Anthony says the US is 76F) by citing a point measurement ( LA was 92! anthony must be wrong ) and you cannot refute a low frequency measure ( the annual SF temp is 55F) by citing a high frequncy measure ( Sat, sept 5th at 1PM was 81F).
What you can do, is read Rhode closely. Then respond
Oh and here is another thing to ponder: Imagine the Holocene was warmer than they suggest.
That would imply a more sensitive climate since the change in forcing between Holocene and LIA isnt particularly big.
I see Michael Mann’s “endorsements” peppered all over some of the breathless news accounts of the study. That alone should raise suspicions.
http://i.imgur.com/s19MOMd.jpg
Scale and time are so important. Perhaps this needs labeling “Your so called hockey stick is here”? What is actually stunning is only a 3 degree fluctuation over 10k years. So I would say that as soon as man arrived in numbers, everything got fixed, so everyone, pat yourselves on the back. If Man and CO2 were involved, they were the fix, not the cause. It is also very obvious that civilization on earth is much more at risk of freezing to death.
link to abstract at top is busted
Perhaps Marcott et al confused the temperature data from their rectal thermometer and mixed the signals during an illness and drug induced deluded analysis? It seems likely that their intellectual grasp of reality is rather lacking and this would be a plausible mistake.
/sarc
Using the full extent of the Marcott graph + GISP: http://img703.imageshack.us/img703/9075/marcottgisp.jpg