Fair-ish and Balanced-ish
Monday, March 17, 2003
A New Low in Climate Pseudoscience: Part 4
Daly misrepresents the Mann paper quite significantly. If one hadn't read the Mann and co-workers paper, then it would be very easy to get the wrong impression of Mann's work. I will quote Daly while inserting my own comments.
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,
This is untrue. Mann and co-workers used 14 proxies to reconstruct the temperture. Of these, five were from ice cores. All of the proxies went back to at least 1000 AD, not "more recent centuries" as Daly asserts.
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'. From the diagram, the Medieval Warm Period and Little Ice Age have disappeared, to be replaced by a largely benign and slightly cooling linear trend in climate - until 1900 AD.
Once again, this isn't true. Maybe Daly can't see it, but the MWP and Little Ice Age are clearly visable. Or to use the words of Mann and co-workers; "Our reconstruction thus supports the notion of relatively warm hemispheric conditions earlier in the millennium, while cooling following the 14th century could be viewed as the initial onset of the Little Ice Age sensu lato". What the Mann paper does is reduce the magnitude of the MWP and Little Ice Age, and shows that they are considerable smaller than the recent temperture changes.
At that point, Mann completed the coup and crudely grafted the surface temperature record of the 20th century... 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.
Once again, this is untrue. What Mann does is too superimpose the proxy data (which isn't just tree rings, nor does it end at 1900, as Daly asserts) onto the surface temperture records. Rather than grafting the two records together, they are compared with each other. They correlate well.
The red line extends all the way to 1998 (Mann's `warmest year of the millennium') , a year warmed by the big El Niño of that year. It should be noted that the surface record is completely at variance with the satellite temperature record. Had the latter been used to represent the last 20 years, the effect would have been to make the 20th century much less significant when compared with earlier centuries.
This part really confuses me. Mann's temperture reconstructions measure surface temperture, the surface temperture records are also surface based, the satellite temperture records measure tempeture in the upper atmosphere (at least the ones that Daly is referring too do, other satellites show that the earth as a whole is warming). Why you would compare surface temperture records with atmospheric temperture records is beyond me.
As a piece of science and statistics it was seriously flawed as two data series representing such different variables as temperature and tree rings simply cannot be credibly grafted together into a single series.
One again, Daly is wrong. Mann didn't graft the two records together. He compared them with each other.
On short Daly either a) didn't read the Mann paper, or b) lied about it contents.