Climatic reconstructions based on tree-ring isotopic series convey substantial information about past conditions prevailing in forested regions of the globe. However, in some cases, the relations between isotopic and climatic records appear unstable over time, generating the “isotopic divergences”. Former reviews have thoroughly discussed the divergence concept for tree-ring physical properties but not for isotopes. Here we want to take stock of the isotopic divergence problem, express concerns and stimulate collaborative work for improving paleoclimatic reconstructions. There are five main causes for divergent parts in isotopic and climatic series: (1) artefacts due to sampling and data treatment, relevant for dealing with long series using sub-fossil stems; (2) stand dynamics, including juvenile effects mostly occurring in the early part of tree-ring series; (3) rise in atmospheric pCO₂, which can directly influence the foliar behaviour; (4) change in climate, which may modify the isotope–climate causal links; and finally (5) atmospheric pollution, which may alter leaf and root functions. Future paleoclimate research would benefit from interdisciplinary efforts designed to develop further process-based models integrating multi-proxy inputs so as to help identify causes of isotopic divergences and circumvent some of them in inverse applications.

中文翻译：

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同位素发散概述??? 树环同位素不稳定的原因和气候相关性

基于树木年轮同位素系列的气候重建传达了有关全球森林地区盛行的过去状况的大量信息。但是，在某些情况下，同位素和气候记录之间的关系会随着时间的流逝而变得不稳定，从而产生“同位素发散”现象。以前的评论已经彻底讨论了树木年轮物理特性而不是同位素的概念。在这里，我们想对同位素发散问题进行评估，表达关注并激发合作以改善古气候重建。同位素和气候系列中不同部分的主要原因有五个：（1）由于采样和数据处理而引起的假象，与使用亚化石茎处理长系列有关；（2）展位动态，包括主要在树轮系列早期出现的幼年影响；（3）大气层上升p CO ₂，可以直接影响叶的行为；（4）气候变化，可能会改变同位素与气候之间的因果关系；最后（5）大气污染，可能会改变叶和根的功能。未来的古气候研究将受益于跨学科的研究，这些研究旨在开发进一步的基于过程的，集成多代理输入的模型，从而帮助确定同位素发散的原因，并在逆向应用中规避其中的一些问题。