Replies

LOL, sorry, no rhetoric and I have no qualms about admitting that I don’t know (that is the start of all wisdom).

Thanks for the comment on vectors, however it was not really all that useful. So if I can describe the process as I understand it. Mann took the instrumentation data and decomposed it into it main components of variability (the Eigen vectors). He then used the proxy series and analyzed these in terms of the components of variability. This gave him the influence of each component.

You then said “Apparently Mann used just nine locations out of all the available data, just 5 for North America.”

No, that is not correct. First, it depends on which paper you are talking about. In his 98 paper that looked at the global temperature he used over 100. In his 99 paper he looked at just the Northern Hemisphere and he used 12 since that is all that were available. However the first 3 were actually the 3 principle components of the 28 tree series for North America so if you consider these as well there are almost 40.

In regards to your list of potential problems with tree rings, these are taken into account. I have explained why there were just 12. In regards to CO2 enhancement, if you have read his paper you will see that he has dealt with CO2 enhancement. He also looks at solar output and checks his data series for dependence. He then removes these “non-climatic” factors from his series.

I don't think your explanation is all that different from mine. What good is a "component of variability" if it is not or can't be measured? I should have mentioned the fact that averaging the vectors gives the influence of each component.

Your comment about CO2 and sun intensity seem plausible (I haven't read Mann's explanation) since they would probably not affect the proxy measurements as much as the climate itself and local affects like cloudiness (to throw another one at you). Mann's 98 paper starts with the LIA so it is not really very useful. Don't you find it interesting that to extend the previous 6 centuries to 11 he had to discard a lot of data? It was certainly available to other researchers as pointed out in Soon's paper.

The biggest problem is your hypothesis on this thread that the climate changes were local to the North Atlantic. That local variation is not addressed by Mann with corresponding warming in other parts of the planet during the same time.

You then said "Apparently Mann used just nine locations out of all the available data, just 5 for North America." No, that is not correct. First, it depends on which paper you are talking about. In his 98 paper that looked at the global temperature he used over 100

Downloaded the Mann-1998 data. The record is as he stated: a large warmup from the LIA. Unfortunately this record starts with the LIA. The other problem is appending measurements from 1981 through 1998 onto the end of the graph containing proxy measurements. Surface temperature measurements (with a documented 0.1 to 0.15 warm bias) are not the same as proxy measurements! The reason is the proxy temperatures measurements are a different kind of measurement which will reflect cold and warm extremes differently. That makes it impossible to say how much warmer the 80's and 90's were to other decades measured by proxies. The evidence is obvious in the data: where they overlap, the proxy and measured temperatures do not match up very well.