First of all, please accept my apologies for not posting for so long. I have been writing a paper based on some research, and have been working 7 day weeks on it for a long period. It is a challenging piece of work, with some results which undermine a body of theory. In order to get it published I have had to be more thorough, and go into depth that would not normally be required, and still it will be a fight to get it published. This is the nature of challenging the orthodoxy.
On the other hand, if you write something that is in line with the orthodoxy it is relatively easy to publish, even if the standard of the work is not very impressive. This brings me to the subject of this post, which is the Marcott et al (2013) paper, with the abstract as follows:
Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time. Here we provide a broader perspective by reconstructing regional and global temperature anomalies for the past 11,300 years from 73 globally distributed records. Early Holocene (10,000 to 5000 years ago) warmth is followed by ~0.7°C cooling through the middle to late Holocene (<5000 years ago), culminating in the coolest temperatures of the Holocene during the Little Ice Age, about 200 years ago. This cooling is largely associated with ~2°C change in the North Atlantic. Current global temperatures of the past decade have not yet exceeded peak interglacial values but are warmer than during ~75% of the Holocene temperature history. Intergovernmental Panel on Climate Change model projections for 2100 exceed the full distribution of Holocene temperature under all plausible greenhouse gas emission scenarios.
I typed in the word ‘Marcott’ into Google News search, and the first headline that greeted me said ‘We’re Screwed: 11,000 Years’ Worth of Climate Data Prove It’. I don’t think it is possible to be more ‘alarmist’ than this. The article is found in the Atlantic, and the article lifts the following diagram from the Marcott et al paper:
The article goes on to say that:
Back in 1999 Penn State climate scientist Michael Mann released the climate change movement’s most potent symbol: The “hockey stick,” a line graph of global temperature over the last 1,500 years that shows an unmistakable, massive uptick in the twentieth century when humans began to dump large amounts of greenhouse gases into the atmosphere. It’s among the most compelling bits of proof out there that human beings are behind global warming, and as such has become a target on Mann’s back for climate denialists looking to draw a bead on scientists. [emphasis added]
The article goes on to propose that the Marcott et al paper vindicates Michael Mann’s long discredited hockey stick chart. The hockey stick chart of Mann has always been a key plank of the alarmist argument, as it is the ‘evidence’ that the warming that took place in the 20th century was unprecedented; it was the ‘smoking gun’. In particular, it removed two key elements from the temperature record, which were the medieval warm period, and the little ice age which followed in the wake of the medieval warm period. In a post in Climate etc., Rud Istvan explains it thus:
The MWP has progressively ‘disappeared’ over the course of the IPCC reports. FAR and SAR showed it to have been much warmer than the present—and nothing to do with CO2. By TAR the MWP was gone, leading to the hockey stick controversy and climategate.
While the MWP did not completely disappear in this new paper, it turned into a <0.1°C blip colder than 1961- 1990. This is quite curious. The MWP was not a blip for the entire northern hemisphere, as illustrated by this figure adapted from a 2010 paper by Ljungvist.
The diagram referenced is given below:
As is evident in the Atlantic article, the media bandwagon has started rolling on the findings of Marcott et al, but the problems are already starting to appear. The data used for the paper was made available (which is certainly a positive), but this has allowed others to look closely at the findings. For example, at Suyts blog, Hank ‘discovered that only nine of the 73 proxies contained data that extended to 1950. Of those nine, only two contained data that extended to 2000′ [and] Starting at 1,500 before present (BP), I graphed the nine proxy datasets. And here’s what I got:’
The hockey stick is not apparent, and this is why:
This new 73 proxy study has alarmists convinced that this is an independent verification and vindication of Mann’s hockey stick. It isn’t. The hockey stick blade at the end of the reconstruction is resulting from an adjustment of the proxy data to agree with Mann’s treemometer study. That, or it is an outright splice of Mann’s data directly.
Inevitably, Steve McIntyre, who played a key role in discrediting the Mann hockey stick, has weighed in. In what Bishop Hill calls an ‘astonishing’ post, McIntrye observes that:
Marcott, Shakun, Clark and Mix did not use the published dates for ocean cores, instead substituting their own dates. The validity of Marcott-Shakun re-dating will be discussed below, but first, to show that the re-dating “matters” (TM-climate science), here is a graph showing reconstructions using alkenones (31 of 73 proxies) in Marcott style, comparing the results with published dates (red) to results with Marcott-Shakun dates (black). As you see, there is a persistent decline in the alkenone reconstruction in the 20th century using published dates, but a 20th century increase using Marcott-Shakun dates. (It is taking all my will power not to make an obvious comment at this point.)
The graph comparing the two is given below:
There is plenty more to the critical analysis of the work, for example the absence of the hockey stick in Marcott’s thesis, or the lack of resolution of the proxy data. As a headline from Wattsupwiththat put it, ‘Tick, tick, tick – how long will the new Marcott et al hockey stick survive?‘ My purpose is not to review the many gaping holes appearing in the Marcott et al paper but to consider why this paper has appeared now. The first point to note is that the data was released with the paper. This is important, as it is an admission that hiding data is no longer acceptable practice. However, this presents a problem for alarmists who present questionable work; they are damned if they do not release the data and damned if they do.
As the data comes under increasing scrutiny, it is becoming very apparent that this paper is extremely problematic, and that the conclusions trumpeted by alarmist media sit upon extremely shonky foundations. The authors, unless very naïve, must have been aware that there paper would not hold up to close scrutiny. However, in having a paper accepted in the peer reviewed literature, they have managed to potentially reinstate the hockey stick – and this might now appear in the next IPCC report. In publishing this work, the authors may have sacrificed their credibility to some degree, but in doing so, they have gained membership of the faction in climate science that dominates the literature (see here for why this matters).
The publication of this paper has been important for the alarmist position as the science of climate change, and the alarmist position, is bumping up against the harsh wall of reality. In particular, the models that are so important in the alarmist case are having trouble with the recent stall in warming; they cannot explain it. There is a very good summary of the problems created by the stall in a report issued by the Global Warming Policy Foundation, written by David Whitehouse. This is from the executive summary, but I recommend reading the whole report (about an hour to read):
The standstill observation was first made in 2006; the global annual average temperature had not increased for the previous five years, even though many climate scientists, and the media, were talking about an ever-warming planet powered by strong anthropogenic global warming. The initial debate was couched in cautious scientific terms but, because it ran counter to popular opinion, many dismissed it and questioned the motives of those pointing out these observational facts. But to the amazement of many, and the obvious annoyance of some, as the years passed all the major global temperature datasets showed no warming throughout the first decade of the 21st century and beyond. As this report shows, as the statistical significance of the standstill increased, the debate about its potential importance grew among many branches of science, even though many prominent scientists and institutions, and almost all of the media, were steadfastly looking the other way.
The problem for the alarmist position is that, as David Whitehouse points out, even some of the most prominent alarmists such as Hansen are now having to accept the reality of the stall, albeit they are using various dubious methods to deflect attention away from it. When crying that the world is heading for catastrophe, it is more than a little problematic when the world does not conform to the narrative. As such, it becomes ever more important to shift focus away from the harsh reality of the evidence that contradicts the narrative, and refocus attention on something that might support the narrative.
Perhaps I am wrong, but it is possible that Marcott et al have made ‘a pact with the devil’ (just a metaphor!). In return for creating the right narrative, they join a privileged elite of alarmist climate scientists, but do so at the cost of selling their scientific souls as the price. They have provided a paper which may be highly questionable, appears not to stand up to scrutiny, but have provided the material that is needed by both the media and IPCC to continue an alarmist narrative – in the face of evidence that is increasingly problematic for the alarmist case. In career terms, Marcott et al may have won from this. Their future work will undoubtedly be looked upon kindly by the gatekeepers of climate science.
However, only Marcott et al know their own motives, and I can only speculate on them here. On the one hand, there is a possibility (and one I would like to believe, even if I do not) that they think their paper is ‘sound’ but, in light of the problems in the paper, and the way it has been presented this would be hard to believe. On the other hand there is the possibility they made the trade-off. I can only wish that the former is true, because the latter is just depressing.
Note: The new batch of climategate emails are starting to cause a new stir. I am very pleased that the use of the emails has (so far) been cautious, and attention has been given to preventing non-climate science related emails being kept out of the public domain. We will undoubtedly find some interesting new insights as the tedious task of going through the emails progresses.
Marcott, S. A., J. D. Shakun, et al. (2013). “A Reconstruction of Regional and Global Temperature for the Past 11,300 Years.” Science 339(6124): 1198-1201