Overall Results - Climate Change: Identification and Projections - page 94

Figure 8.2. Intervals of confidence (90%)

It is shown by Figures 8.1 and 8.2 that the confidence regions relating to
Jones and Mann are the most reduced. This can be explained by the fact that
the amplitude of the millennium-old variations of the Jones and Mann
reconstruction is the weakest of the four. Hence, mechanically, the output
errors are the lowest, and ultimately, the estimated variances are the
smallest. The opposite reasoning also explains the wider uncertainties from
the Loehle reconstruction. Pushing this reasoning to the limit, a hockey stick
curve with a perfectly rectilinear handle would lead to ranges with a width of
almost zero, which this would clearly not validate the methods used to obtain
this curve.

Figure 8.2 shows that the ranges of confidence estimated for climate
sensitivity are generally incompatible with those of the IPCC, apart from
those which result from the Loehle reconstruction. It also appears that the
upper limit of the IPCC's assumed range is never reached by

the ranges identified, even when they come from Jones and Mann.
According to their data, the lower and upper limits for climate sensitivity
should be reduced to

( S =− 6 C) °

c lim

[ ]

13C − ° .