Calibrating Imperfection?

The Taymyr Peninsular in Siberia has a reasonably long Russian Larch tree ring proxy compiled by Jacoby and gang which is dated 2006 and archived on the NOAA paleo site. The series ends in 1970 because Jacoby and gang determined that the proxy diverged from temperature starting in that date.

Ostrov Dikson is a small Russian town located on an island at the west side of the Taymyr Peninsular. It has an airport and a temperature record starting in 1918. There are three data points for the March through May average that are missing. I interpolated those for the average of the preceding and following values just for the spread sheet.

Using the period of overlap, 1918 to 1970, I shifted the Ostrov series so that the average of the overlap period aligned with the Taymyr data. The yellow mean for Taymyr and the green mean for Ostrov are shown on the chart.

The mean for Ostrov Dikson from 1970 to present is shown in red and is approximately 0.6 degrees higher than the 1918 to 1970 mean. The full series mean of Taymyr in blue, is about 0.4 degrees lower than the 1918 to 1970 mean.

The best average growth rate for the Taymyr series is near the 1918 to 1970 mean, with 1918 to 1950 being close to the optimum growth rate for the series. That should indicate than the period between 1918 and 1950 to 1970 should be the near the optimum conditions, temperature, precipitation etc. for the type of tree.

This chart shows the entire period of the Taymyr tree ring series.

Above I have added the central England temperature centered on the 1918 to 1970 period so that all three series have a common base line. The match, considering trees are not thermometers is pretty good. With the CET series add, there are periods were temperatures above the mean correspond with reduced tree growth and period where when temperatures are below the mean there is reduced tree growth. While the tree rings series do not provide a great deal of temperature information, they do have potential to provide more information about what is average global temperature, at least as I interpret the data.

Note: the CET data is also March through May.