Alarmism about global warming has been dealt yet another body blow, as the so-called “settled science” gets some unsettling data.  Anthony Watts of Watts Up With That (hat tip: John Hinderaker of Powerline) reports on a new study of tree ring data indicating the long term trend has been cooling for the last two millennia:

 As the international team of researchers from the Czech Republic, Finland, Germany, Greece, Sweden and Switzerland describes it, this history depicts “a long-term cooling trend of -0.30°C per 1,000 years over the Common Era in northern Europe” (see figure below). Most important of all, however, they note that their temperature reconstruction “has centennial-scale variations superimposed on this trend,” which indicate that “conditions during Medieval and Roman times were probably warmer than in the late 20th century,” when the previously-rising post-Little Ice Age mean global air temperature hit a ceiling of sorts above which it has yet to penetrate.

This is, in Watts’ words, “more real-world evidence for the fact, that there is nothing unusual, unnatural or unprecedented about the Earth’s current level of warmth.” In fact, if anything we are now cooler than through most of known history.

Of course, tree ring data is a proxy for temperature data. But if warmists wish to cricize this study on that basis, they open a Pandora’s Box, because tree ring data is at the heart of the infamous “hockey stick” used to such great effect to launch the entire fraud.