Thursday, January 31, 2008
This graph of global temperature has recently been published:
Using data from eighteen 2000-year-long proxy temperature series from all around the world that were not developed from tree-ring data (which provide significant interpretive challenges), the author (1) smoothed the data in each series with a 30-year running mean, (2) converted the results thereby obtained to anomalies by subtracting the mean of each series from each member of that series, and then (3) derived the final mean temperature anomaly history defined by the eighteen data sets by a simple averaging of the individual anomaly series, a procedure that he rightfully emphasizes is "transparent and simple."
.... "the mean series shows the Medieval Warm Period (MWP) and Little Ice Age (LIA) quite clearly, with the MWP being approximately 0.3°C warmer than 20th century values."
Loehle notes that "the 1995-year reconstruction shown here does not match the famous hockey stick shape," which clearly suggests that one of them is a poorer, and the other a better, representation of the truth. Because of its simplicity and transparency, as well as a host of other reasons described in detail by Loehle -- plus what we have learned since initiating our Medieval Warm Period Record-of-the Week feature -- it is our belief that Loehle's curve is by far the superior of the two in terms of the degree to which it likely approximates the truth.
I love the qualification of "superior" as being only in terms of its truth. That is a scientist not a PR man speaking.
Note that this takes no account of records from weather stations which, a century ago were in open country & are now in the middle of towns, which seems to be the explanation for alleged recently recorded rises.
Coincidentally an article in the New York Times says that those who died during the Black Death were largely already weak.
This was reported by Jerry Pournelle & led me to remember that the period of the Black Death was at the end of the Medieval Warming Period, though prior to the Little Ice Age, when temperatures had fallen to pretty much where they are now. He published my comment & added (in italics) his own.
If the Black Death mainly killed the already weak it suggests that it was an inevitable result of decreased crop production caused by the end of the Medieval Warm Period. We know that there had been a major population rise during the warm period.
But we all know there wasn't an actual Medieval Warm and there couldn't have been a population expansion. Anyway it was the Gulf Stream, and the Greenland Colonies were tiny, and the Inuit don't really have stories of the times when they were reindeer herders. It's all an illusion.