>>73680
https://www.prospectmagazine.co.uk/magazine/the-case-against-the-hockey-stick
>Of course, there is other evidence for global warming, but none of it proves that the recent warming is unprecedented. Indeed, quite the reverse: surface temperatures, sea levels, tree lines, glacier retreats, summer sea ice extent in the Arctic, early spring flowers, bird migration, droughts, floods, storms—they all show change that is no different in speed or magnitude from other periods, like 1910-1940, at least as far as can be measured. There may be something unprecedented going on in temperature, but the only piece of empirical evidence that actually says so—yes, the only one—is the hockey stick.
>A retired mining entrepreneur with a mathematical bent, McIntyre asked the senior author of the hockey stick graph, Michael Mann, for the data and the programs in 2003, so he could check it himself. This was five years after the graph had been published, but Mann had never been asked for them before. McIntyre quickly found errors: mislocated series, infilled gaps, truncated records, old data extrapolated forwards where new was available, and so on.
>Not all the data showed a 20th century uptick either. In fact just 20 series out of 159 did, and these were nearly all based on tree rings. In some cases, the same tree ring sets had been used in different series. In the end the entire graph got its shape from a few bristlecone and foxtail pines in the western United States; a messy tree-ring data set from the Gaspé Peninsula in Canada; another Canadian set that had been truncated 17 years too early called, splendidly, Twisted Tree Heartrot Hill; and a superseded series from Siberian larch trees. There were problems with all these series: for example, the bristlecone pines were probably growing faster in the 20th century because of more carbon dioxide in the air, or recovery after “strip bark” damage, not because of temperature change.
>This was bad enough; worse was to come. Mann soon stopped cooperating, yet, after a long struggle, McIntyre found out enough about Mann’s programs to work out what he had done. The result was shocking. He had standardised the data by “short-centering” them—essentially subtracting them from a 20th century average rather than an average of the whole period. This meant that the principal component analysis “mined” the data for anything with a 20th century uptick, and gave it vastly more weight than data indicating, say, a medieval warm spell.