I just learned something today which has left a sick feeling in my stomach. I learned how the latest Mann et al hockey stick graph was created. So you don’t have to read the paper HERE, I’m going to summarize the result.
This time Mann avoided all the tree ring reconstructions from the old hockey stick because of a problem with what is termed Divergence. Divergence means the data don’t correlate well in recent times (last 130 years). Scientists know that a high percentage of trees “temperature” data don’t fit well when compared to the warming trend of earth – measured data. To sort the data, they correlate the data, which is very noisy and doesn’t look like a temperature measurement at all by measuring its statistical significance to the 130 year measured temperature record. Data which doesn’t match to a minimal extent with current temperatures is rejected. The remaining data sets are averaged together (often using very strange techniques) to create a final signal.