Latest Data from Mann Undermines His Assertions

A review at CO2science.org of the latest paper by Michael Mann reconstructing historic temperatures (Geophysical Research Letters 30) casts doubt on his continued assertion that the data prove that the warmth in recent decades is unprecedented.

A graph available on the web site (http://www.co2science.org/journal/2003/v6n34c4.htm) reconstructed from Mann’s data shows that, “The end point of their reconstructed global mean temperature history is not the warmest period of the prior 1800 years. In fact, their treatment of the data depicts three earlier warmer periods: one just prior to AD 700, one just after AD 700 and one just prior to AD 1000.”

The review goes on, “The globe only becomes warmer in the 20th century when its measured temperatures are substituted for its reconstructed temperatures. This approach is clearly unacceptable; it is like comparing apples and oranges. If one has only reconstructed temperatures from the distant past, one can only validly compare them with reconstructed temperatures from the recent past.”