The Hockey Schtick:
A new paper from SPPI and CO2 Science reviews the scientific literature on historical temperature trends in China and concludes, “the results of these several studies demonstrate that the so-called unprecedented warmth of the late 20th century is simply a myth, as far as China is concerned. The apparent great warmth of this period in this particular part of the world appears to have been but a common manifestation of naturally-induced and regularly-recurring conditions similar to those that have been experienced in prior millennia. These results also serve as a testimony against those who would deny the existence of an extensive (hemispheric or global) Medieval Warm Period and Little Ice Age, as well as an extensive Roman Warm Period and Dark Ages Cold Period, and cyclical climate changes in general.”
Controversy abounds over the temperature history of the earth, particularly that of the past one to two millennia. The original debate was sparked by the papers of Mann et al. (1998, 1999), which challenged the long-accepted view that there was nothing unusual about earth’s climatic history subsequent to the inception of the Industrial Revolution; and it prompted the Intergovernmental Panel on Climate Change (IPCC) to disavow their original representation of the temperature history of the Holocene (Houghton et al., 1990), where several periods of time prior to the inception of the Industrial Revolution were depicted as having experienced temperatures that were higher than those of the latter part of the 20th century.