Donald Prothero, a geologist and (official) skeptic, has written an article about the Marcott hockey stick, but mentioning its less illustrious forebear as well. While there is obviously quite a lot one can say about Marcott's work, I thought it best to address myself to the section on Mann. This was as follows:
The chief legitimate scientific criticism about the original “hockey stick” paper (so-called because it shows climate as nearly a straight trend through the past 1000 years, culminating in a sharp bend upward in the past 200 years, like the blade of a hockey stick) was that Mann and colleagues generated a composite curve of actual observed global temperatures (the last 150 years or so), with older records from tree rings, ice cores, and a few other data sources. Since all these recorders measure global temperature differently, it is always a challenge to calibrate them properly so they yield a single consistent climate curve. However, NONE of these attacks on the data of Mann et al. (1998) contradict the fact that the sharp rise in temperatures in the past 200 years is real, or that it is much more rapid than any climate change we could detect from these data sources over the previous 1000 years.
As readers here will no doubt realise, this is about as wrong as it's possible to be in three sentences, so I submitted a comment as follows:
Your paragraph on the original hockey stick is not even close to being correct. The overlaying of instrumental temperatures on the proxies was a minor talking point – it merited a paragrah in my book.
The major criticisms related to use of proxy data that were known to contain a non-climatic signal and the use of an ad-hoc statistical technique that overemphasised hockey stick shaped series in the dataset and the fact that it failed standard statistical verification tests.
The point that none of the criticisms of the hockey stick refuted the idea that temperatures have risen sharply in the last 200 years is a surprising thing to say, given that the hockey stick shows temperatures rising only from the year 1900. However, that wasn’t what the hockey stick paper or the criticisms of it were about anyway (why would you need proxies to tell you about 20th century temperatures?). What was in dispute was whether the medieval warm period was warmer than today.
These words were deemed too horrible for the sensitive Skepticblog readers and my comment has not appeared.
Dr Prothero is, it seems, a man who would rather duck the possibility of being confronted with his errors.