Geoscience Reference
In-Depth Information
Fig. 5.9
An illustration of the use of regional curve standardization (RCS) on a 'modern' chronol-
ogy and the influence on the shape of the RCS curve exerted by a recent (presumably warming
which have a wide age range and include pith-offset estimates but, after 1920, also show a large
growth increase are used here: (
a
) a simple RCS curve (
thin line
) and the 'signal-free' RCS curve
(
thick line
)and(
b
) the corresponding simple RCS chronology (
thin line
) and 'signal-free' RCS
chronology (
thick line
).
Gray shaded
areas show tree counts
ages, following the signal-free approach can mitigate the localized bias imparted by
climate in the RCS curve without the need for large numbers of earlier subfossil tree
data to 'average' away any modern climate signal.
Even the application of the signal-free technique is not able to mitigate the loss
of the overall slope of the chronology, and a 'modern' chronology must therefore be
considered as having a largely 'arbitrary' slope.
5.6 Examples of Issues that Arise in Various Applications of RCS
In this section, we discuss several examples of previous work, chosen here to illus-
trate 'potential' bias problems that are suggested by the way in which previous
authors have chosen to implement, or could be interpreted as having implemented,
first, simple RCS and then variations of the simple RCS. The three examples are
5.6.1 Inappropriate RCS Definition
maximum-latewood-density (MXD) data aquired from temporally overlapping sub-
fossil and living-tree pine samples from north Sweden. The chronologies spanned
the 1480-year period from AD 501 to 1980. The ring-width RCS curve was built
