From the Philadelphia Inquirer in a piece that actually covers the science, unlike many other stories by clueless folks writing for other clueless folks-
[Mann’s Nature] paper incorporated the tree rings, ice cores, corals, and a number of other “proxies” into a kind of formula that could approximate the world’s temperature as it fluctuated over the last 1,000 years.
Also included in the graph were real temperature measurements, starting in the mid-1800s and continuing to the present.
Others before Mann had reconstructed the historical Medieval Warm Period and the Little Ice Age that gripped the world during the 1700s, but Mann’s paper was the most complete to date and revealed the influential graph that became known as the hockey stick.
Many scientists were sounding the alarm over human-generated climate change well before that graph appeared.
Critics also pointed to the phrase “hide the decline” in an e-mail written by Jones. That, said Mann, referred not to a decline in measured temperatures but to a decline reflected in a certain kind of tree-ring measurement that relies on wood density.
For reasons researchers still can’t explain, those wood measurements track neatly with temperatures from the late 1800s to the 1960s. After that, they show temperatures going down while the thermometers show the opposite.
Scientists have been discussing this “divergence” problem in the open for years.
Opinions differ among scientists as to the importance of the divergence problem, but most say there’s enough other evidence to support the hockey stick. One exception is MIT’s Richard Lindzen.
“Anyone familiar with these issues would say these [e-mails] explicitly refer to falsification and rigging of data.” Lindzen said the failure of the proxies to reflect temperature trends in the last few decades is a real problem. If the proxies don’t align with temperatures for the last 30 years, he said, how can we rely on them to tell us what the temperatures were for the last 1,000?
In the late 1990s, [North] said, “people were running up and down the halls of Congress waving these graphs and saying the Earth was about to burn.”