Once again, Mann has claimed that he can obtain a “reliable long-term record” without tree ring data, a claim that, as previously noted, is eerily reminiscent of a similar untrue claim made 10 years ago.
Ten years ago, we could not simply eliminate all the tree-ring data from our network because we did not have enough other proxy climate records to piece together a reliable global record,” said Michael Mann, associate professor of meteorology and geosciences and director of Penn State’s Earth System Science Center. “With the considerably expanded networks of data now available, we can indeed obtain a reliable long-term record without using tree rings.”
The first thing to look at is always the data. Basketball scouts look at dozens of prospects, so climate scientists should be able to look at 33 proxies. I’ve plotted all 33 proxies in a consistent format below. I’ve highlighted the 950-1100 MWP period and the modern period in the graphics below and standardized all proxies on 1400-1800, choosing this period to avoid incorporating the two extreme periods: I think that this highlights the proxies of interest quite well. As an experiment, I’ve made the proxies into a flash-gif (Thanks to Anthony for advising me on software.) I’ll make a few comments below and plan to continue examining this data.
Figure 1. These are arranged more or less by longitude going east around the world. x-axis dates are Years AD with 950-1100 and 1850-1980 highlighted. y-axis SD units are based on native proxy units standardized on 1400-1980.
Press Release vs Article
The above comments were from the press release. Now look at the article (not available at the time of the press release.) Using CPS methods (which should be sufficient to recover any actual signal), Mann says that a “skilful reconstruction” is possible only back to AD1500 – not even the AD1400 of MBH98, conceding the 15th century period in dispute in our articles. However, Mann then triumphantly announces that he can get a “skilful reconstruction” using a new and improved Mannomatic – in this case, an “EIV method” together with other opague Mannian multivariate operations, a method that you can’t read about in Draper and Smith or other statistics texts. The statistical authority for the method is, needless to say, another Mannian article. Mann et al:
The skill diagnostics (Fig. 2; see also Dataset S4) for the validation experiments indicate that both the CPS reconstructions (with the screened network) and EIV reconstruction (with the full network) produce skillful NH land reconstructions back to A.D. 400. When tree-ring data are eliminated from the proxy data network, a skillful reconstruction is possible only back to A.D. 1500 by using the CPS approach but is possible considerably further back, to A.D. 1000, by using the EIV approach. We interpret this result as a limitation of the CPS method in requiring local proxy temperature information, which becomes quite sparse in earlier centuries. This situation poses less of a challenge to the EIV approach, which makes use of nonlocal statistical relationships, allowing temperature changes over distant regions to be effectively represented through their covariance with climatic changes recorded by the network.
A skillful EIV reconstruction without tree-ring data is possible even further back, over at least the past 1,300 years, for NH combined land plus ocean temperature (see SI Text). This achievement represents a significant development relative to earlier studies with sparser proxy networks (4) where it was not possible to obtain skillful long-term reconstructions without tree-ring data.
There is something eerily similar to an observation in MBH98, where Mann noted in passing that conventional methods had been “ineffective”, but the Mannomatic was just the ticket. Of course, no one then knew exactly what a Mannomatic was (no mention of Mannian principal components or bristlecones), but climate scientists and IPCC loved the answer.
Largely because of the inhomogeneity of the information represented by different types of indicators in a true ‘multiproxy’ network, we found conventional approaches (for example, canonical correlation analysis, CCA, of the proxy and instrumental data sets) to be relatively ineffective. Our approach to climate pattern reconstruction relates closely to statistical approaches which have recently been applied to the problem of filling-in sparse early instrumental climate fields, based on calibration of the sparse sub-networks against the more widespread patterns of variability that can be resolved in shorter data sets. We first decompose the twentieth-century instrumental data into its dominant patterns of variability, and subsequently calibrate the individual climate proxy indicators against the time histories of these distinct patterns during their mutual interval of overlap.
Are we seeing the same thing once again? A new Mannomatic?
A Few Comments on the “Proxies”
I identified 33 non-tree ring proxies with that started on or before 1000 – many, perhaps even most, of these proxies are new to the recon world. How were these particular proxies selected? How many proxies were screened prior to establishing this network? Mann didn’t say. (Mann SI Figure S8 plots 18 of these series (ones going back to 818) – readers should consult this as well.)
One’s first impression is that there isn’t a common signal in this data.
The proxies with the loudest modern warm period “signal” – a Finnish lake sediment, are said by the author to have been contaminated by non-climatic modern disturbance. Mann notes in the SI, referring specifically to these 4 series:
we also examined whether or not potential problems noted for several records (see Dataset S1 for details) might compromise the reconstructions.
This smacks all too much like his attempt to “adjust” the bristlecone data, concocting an “adjustment” that didn’t affect the results. The logical course of action when an author notes such disturbance is simply not to use the data. There are dozens of other unused series. In Mann’s SI Figure 7, he argues that the presence/absence of 7 problematic series doesn’t “matter”. So why use them? And why use 4 of them? It’s definitely fishy.
One of the Socotra Island series has a huge modern increase, not present in another Socotra series – this data needs to be examined. The Agassiz ice core series also has a big difference: it also had a lot of leverage in Moberg.
I’ve already examined the Curtis Punta Laguna data and Mann’s version does not match the public archive. I’ll discuss this separately.