Today’s post in my series about Michael Mann is going to be a bit different in that it “doesn’t matter.” I’m not going to discuss anything central to Mann’s results or arguments. Instead, I’m just going to discuss Mann being incompetent in his work.
You should remember Mann’s reconstruction used 415 different data series. Approximately 300 were combined via a method he called Principal Component Analysis (PCA), reducing them to 31 proxies. Another 81 series were used directly as proxies. That gave a total of 112 proxies.
As you should also remember, only 22 of those proxies extended back to 1400 AD. We’ve already discussed how two of those 22 proxies, the most important ones, were inappropriate for Mann’s purposes. I won’t revisit them. Instead, I’ll look at some of the other 20.
We can find a list of the proxies which extended back to 1400 AD here. The first four are quelc1-o18.dat, quelc1-accum.dat, quelc2-o18.dat and quelc2-accum.dat When we look at the file describing the various series used in the paper, we see those series were described:
Quelccaya Ice Core summit Ice O-18 (air temp) 14S 71W 470 Thompson 1982 " " Ice accumulation precip " " 488 " " Core 2 Ice O-18 (air temp) " " 744 " " " Ice accumulation precip " " 744 "
There are a couple of obvious questions here. First, why are four of the 22 proxies that extend back to 1400 AD all from the same location? One of the primary reasons to use something like PCA is to prevent over-sampling areas. That purpose is defeated if many proxies you don’t use PCA on are from a single location.
Second, why are two of them listed as precipitation proxies? Are we to believe precipitation proxies should be used to reconstruct temperatures? I have to assume so. That’s the only explanation I can see for three more proxies from that period: seprecip-nc.dat, seprecip-sc.dat and seprecip-ga.dat. If the “precip” in there names isn’t obvious enough, here are their descriptions:
Southeast U.S-N. Carolina Dendro ring widths precip 36N 80W 1005 Stahle et al 1988 Southeast U.S-S. Carolina Dendro ring widths precip 34N 81W 1005 " Southeast U.S-Georgia Dendro ring widths precip 33N 83W 1005 "
That’s five proxies explicitly stated to be precipitation proxies. ~25% of the proxies that covered Mann’s entire period don’t measure temperatures at all. Combined with the two we’ve previously discussed, some ~30% of his 1400 data was inappropriate. That value goes up to ~35% if we don’t oversample Quelccaya (located in the Andes mountains).
It gets weirder if we look at the full, 112 proxy roster. In addition to the proxies mentioned above, it lists floresc.dat, redsea-o18.dat, chiriq-o18-ann.dat, and java.dat. These are described:
Burdekin River Coral-fluorescence Precip/Runoff 20S 147E 1746 Lough 1991 Red Sea Coral-O-18 SST/Precip 29.5N 35E 1788 Heiss, 1994 Gulf of Chiriqui, Panama Coral-O-18 Precip 7.5N 81W 1708 Linsley et al, 1994 Java Dendro ring widths precip 8S 113E 1746 Jacoby & D'Arrigo 1990
Three of the four are listed as precipitation proxies, and a fourth is listed as both a sea surface temperature and precipitation proxy. We won’t count that fourth one. That puts us up to eight different precipitation proxies used to reconstruct temperatures.
Three more are found when we look at the output of PCA applied to the “Stahle Oklahoma” network. It’s listed as giving three PCs, pc01.out, pc02.out and pc03.out. These three PCs were derived from 14 individual series. Here are the descriptions of the first three:
Neosho R. OK Dendro ring widths precip 37N 94W 1681 Stahle & Cleaveland 1993 Keystone Res. OK " " 36N 96W 1613 " Canadian Res OK " " 35N 98W 1682 "
That pattern continues. That means those three PCs were precipitation proxies. That puts us up to 11. Eleven out of 112 proxies used by Michael Mann were stated to be precipitation, not temperature, proxies.
But there’s more. Another 11 proxies listed prec-1820-01.dat, prec-1820-03.dat, prec-1820-04.dat… prec-1820-12.dat. One would naturally think those are precipitation proxies, putting our count up to 22. However, that misses out on an important point. Those 11 are described under the section, “LONG INSTRUMENTAL DATA”:
Station Precipitation " precipitation 12.5N 82.5E 1813 " " " " 17.5N 72.5E 1817 " " " " 37.5N 77.5W 1809 "
The eight I don’t show are in the same form. What this shows is those 11 proxies aren’t just measures of precipitation, they’re instrumental records. It’s difficult to understand how one does a paleoclimatic reconstruction while using instrumental data. As though that’s not weird enough, if you check the latitude/longitude listings of these series, 10 of the 11 values aren’t even close to the correct locations.*
In any event, that puts us up to 22 precipitation proxies, 11 of which are instrumental. The next set of proxies to examine are temp-1820-01.dat-temp… 1820-05.dat, temp-1820-07.dat, temp-1820-09.dat… temp-1820-13.dat. These eleven proxies are listed under the same “LONG INSTRUMENTAL DATA” header (I’m showing only the first three):
Station temperature gridded average surf air temp 42.5N 92.5W 1820 Jones & Bradley 1992 " " " 47.5N 2.5E 1757 " " " " 47.5N 7.5E 1753 "
These are all temperature measurements done by man. That is, Mann used 11 instrumental temperature series to help reconstruct temperatures. There’s also another series (england.dat) which is mostly instrumental data, but we won’t consider it here. Instead, we’ll just leave the count as 22 precipitation proxies and 22 instrumental series, 11 of which overlap.
If you believe a temperature reconstruction should be made with temperature data, you must conclude 22 of Mann’s 112 (20%) proxies were inappropriate. If you believe a paleoclimate reconstruction should be made with data taken from nature, not from manmade measurements, you must conclude 22 of Mann’s 112 (20%) proxies were inappropriate. If you believe both, feeling paleoclimatic temperature reconstructions should be made with temperature data taken from nature, you must conclude 33 of Mann’s 112 (29%) proxies were inappropriate.
And that’s a minimum, gotten if we don’t even look at any of the data or sources.
*A description of the error and how it happened can be found in this post. That post also shows the same error was repeated in a 2007 paper Mann authored. That’s remarkable as the error was pointed out to him multiple times between 1998 and 2007.