One of the cherished canards of the Deniers is a mythical Global Warming of medieval times,
warmer than today.
But what does the Science say?
Early models of climate over the last thousand years relied heavily on the data collected by H.H. Lamb, an imminent and careful researcher, who collected tree ring and other historical data over several decades.
Lamb's data was flawed only in that it was geographically limited. The early graphs that showed a large "Medieval Warming" hump reflected a bias toward the northern atlantic region.
Nonetheless, the Medieval Warming meme has shown surprising durability in the Denier portfolio.
When later, more widely collected data showed that the warming hump was an artifact, the scientists that produced it were widely vilified.
The National Academy of Science review of the matter was critical of both camps, but broadly confirmed that the Medieval hump was exaggerated in earlier graphs.
Subsequent research has confirmed and extended the so called "Hockey stick" configuration, showing marked warming in the last 150 years.