Tree-ring variables as proxy-climate indicators: Problems with low-frequency signals

Abstract

In recent years there has been a notable increase in the number of research projects engaged in building supra-long (multi-millennial) tree-ring chronologies. Together with a growing awareness of the potential for anthropogenic climate change, this work is shifting the focus of dendroclimatology. Instead of a more traditional interpretation of tree-ring data in terms of annual-to-decadal timescale climate variability the emphasis is increasingly placed on century timescale changes. We review a number of problems with the interpretation of low-frequency climate change in tree-ring derived data. Perhaps the most significant is the high-pass filtering effect of "standardization" techniques commonly used in chronology construction to remove age-related sample bias in the original tree growth measurement data. These techniques effectively remove low-frequency variability and with it the evidence of long-term climate change. Other forcings may also be 'corrupting' the climate signal in the recent period (that used for calibrating the climate signal). Differences in the origin of the samples or changes in site ecology may also impart an inhomogeneity in the response of tree growth through time, hence violating the fundamental assumption of uniformitarianism that underpins proxy climate research.

Experiments based on blue intensity for reconstructing North Pacific temperatures along the Gulf of Alaska

“…These pooled composite variable datasets, with their greater overall replication, allowed detrending experiments to be performed to ascertain the sensitivity of the final parameter chronologies to different detrending choices. Specifically, RW detrending experiments were performed using (1) STD, negative exponential function or negative or zero-slope linear function detrending via division; (2) NEPT, negative exponential function or negative or zero-slope linear function detrending via subtraction after power transformation of the raw RW data (Cook and Peters, 1997); and (3) RCS, single-group regional curve standardization (Briffa et al, 1996;Esper et al, 2003;Briffa and Melvin, 2011) detrending via division. The regional agealigned curve was smoothed using a cubic smoothing spline (Cook and Peters, 1981) of 10 % of the series length.…”

Regional Summer Temperature Reconstruction in the Khibiny Low Mountains (Kola Peninsula, NW Russia) by Means of Tree-ring Width during the Last Four Centuries

“…This common, site-specific trend can then be used to de-trend the single series. Its advantage is the preservation of low-frequency signals and trends on time scales longer than a few decades (Briffa et al, 1992(Briffa et al, , 1996Esper et al, 2003). For our trees (1) the cambial age from samples with preserved pith was determined.…”

A 1,200-year perspective of 21st century drought in southwestern North America

“…Tree-ring reconstructions of temperature for the Southwest suggest warmer temperatures for at least portions of the medieval period (13,29,(49)(50)(51). These reconstructions usually represent growing-season temperatures and, because of limitations of the paleoclimatic indicators generally do not preserve centennialscale variations (52,53), at least on these regional scales. Along with evidence for multiyear periods of enhanced temperatures approaching 1.0°C during some intervals of the medieval period, records also indicate periods of normal to below average temperatures at other intervals ( Figure 2D).…”