EDITORIAL Divergence pitfalls in tree-ring research

tree-ring data against temperature time series. Such methods are commonly used to transfer ring width, density, or stable isotope measurement from mm, g/mm3, and into degrees Celsius—forming the cornerstone for proxy reconstructions (Cook and Kairiukstis 1990). The specific subject of the Loehle (2009) contribution is on non-linear calibration techniques, which have been considered when proxy data in-dicate inconsistent responses to medium and extreme temperature deviations. Non-linear calibration has a long-standing history in tree-ring research (see Fritts 1976 for an introduction), and variants of non-linear response models have been applied in a variety of tree-ring analyses over the past decades (e.g., Carrer and Urbinati 2001; Fritts 1969; Graumlich and Brubaker 1986; Woodhouse 1999). So, while approaches to tackle non-linear tree-ring/climate associations are relevant when dealing with proxy data, it is, however, the motivation that called for re-attention to these techniques that is of particular interest: the divergence phenomenon (DP) in tree-ring research. DP was first described over a decade ago by Jacoby and D’Arrigo (1995) and since then has been reported from a variety of sites mainly concentrated toward