The UnAustralian

Saturday, March 15, 2003
 
A New Low in Climate Pseudoscience: Part 1

At the request of Ken Parish, I've looked into a long article by global warming skeptic John Daly titled "The `Hockey Stick': A New Low in Climate Science".

I'll start by summarising Daly's piece. Sadly, it isn't easy to summarise, given the large amount of vitriol and insults which are scattered throughout the work, but I'll do my best. Daly starts by reproducing a figure from the IPCC 1995 report showing temperature change over the last 1000 years. In particular, there is a medieval warm period (700 - 1300 AD), and a little ice age (1560 - 1830 AD). He then gives some more details about the warming and cooling, and speculates that the temperatures changes are solar induced. He believes (incorrectly) that this facts pose a major problem for climatic scientists, and makes two statements:

1) If the Medieval Warm Period was warmer than today, with no greenhouse gas contribution, what would be so unusual about modern times being warm also?

2) If the variable sun caused both the Medieval Warm Period and the Little Ice Age, would not the stronger solar activity of the 20th century account for most, if not all, of the claimed 20th century warmth?

However, now he presents a paper by Dr Michael Mann and co-workers (Mann, 1999) stating "...in one scientific coup overturned the whole of climate history" (ignoring that the same authors had used exactly the same technique in a paper published the year before (Mann, 1998)). As Daly states "Using tree rings as a basis for assessing past temperature changes back to the year 1,000 AD, supplemented by other proxies from more recent centuries, Mann completely redrew the history, turning the Medieval Warm Period and Little Ice Age into non-events, consigned to a kind of Orwellian `memory hole'".

Daly now starts to critique the paper, initially stating "At that point, Mann completed the coup and crudely grafted the surface temperature record of the 20th century (shown in red and itself largely the product of urban heat islands) onto the pre-1900 tree ring record. The effect was visually dramatic as the 20th century was portrayed as a climate rocketing out of control. The red line extends all the way to 1998 (Mann's `warmest year of the millennium'), a year warmed by the big El NiƱo of that year".

He pretends that the Mann paper was a bloodless coup in the climate sciences and was rapidly accepted by the mainstream science (and fully accepted by the time the IPCC wrote their 2001 report).

Daly now presents a number of reasons as too why tree-rings are poor climate indicators, and then states "[t]o disprove the `Hockey Stick', it is sufficient to merely demonstrate conclusively the existence of the Medieval Warm Period and/or the Little Ice Age in proxy and/or historical evidence from around the world".

Next Daly presents 14 exhibits (regional studies) which indicate the existence of a medieval warm period, and small ice age.

The next section (titled "The Science that Lost its Way") doesn't concern the scientific techniques and interpretations used, so I'll ignore it.

| 4:20 PM