Stephan and Rachit cored lots of trees, to estimate weather in past years. In a cold climate, near the tree line, a tree will generally grow more if the weather is warm than if it is cold, though lots of other things affect it too. Still, if you check lots of trees over a wide area of very cold land, other factors will probably average out, and the rate of growth,the width of the tree rings, will largely indicate temperature. And Stephan and Rachit cored a lot of trees, over a lot of very cold land, while being attacked by hordes of ravenous mosquitoes.
Yet somehow, strange to report, only about a tenth of the trees they cored were used to construct a hockey stick graph. Most of their data was quietly buried as unwanted, but leaked in the climategate files documents/briffa-treering-external/stepan. Recently Climate Audit took a look at this neglected data.
Why, you may ask, were some trees included and other trees, the vast majority of the trees, not included?
Climate Audit constructs a graph of growth. The red line is the growth rate of the small set of trees the Anthropogenic Global Warmists chose to use for their hockey stick of doom. The black line is growth rate for all of the trees that Stephan and Rachit cored while fighting off mosquitoes, including the vast majority of trees which the the Warmists somehow chose to not use.
What the real data showed
Observe that the red line, the cherry picked trees, show something dramatic and unusual happening in the twentieth century, especially the late twentieth century, show something like a hockey stick. The unselected trees, the vast majority of the trees, show a slight warming trend over centuries, but no more so in the twentieth century than in any other century.