A recent National Academy of Sciences study was commissioned to determine the accuracy of the temperature measurements oft-cited by other reports and articles concerning global warming. At issue was whether or not the methods of measuring temperature (tree rings, varves, etc) were accurate enough to determine that the Earth is at it’s hottest. Here’s the brief:

There is sufficient evidence from tree rings, retreating glaciers, and other “proxies” to say with confidence that the last few decades of the 20th century were warmer than any comparable period in the last 400 years, according to a new National Research Council report. There is less confidence in reconstructions of surface temperatures from 1600 back to A.D. 900, and very little confidence in findings on average temperatures before then.

To illustrate what they’re saying, I’ve modified the standard global warming graph just a bit:

This is a fairly damning report for those who think that the earth is merely entering a high point in some sort of natural temperature cycle (whether it be biochemical or sun-output-related). FYI: It takes 11 years for the Sun to go from its solar minimum to its solar maximum.