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Evidence for reduced sensitivity of tree growth to temperature has been reported from multiple forests along the high northern latitudes. This alleged circumpolar phenomenon described the apparent inability of temperature‐sensitive tree‐ring width and density chronologies to parallel increasing instrumental temperature measurements since the mid‐20th century. In addition to such low‐frequency trend offset, the inability of formerly temperature‐sensitive tree growth to reflect high‐frequency temperature signals in a warming world is indicated at some boreal sites, mainly in Alaska, the Yukon and Siberia. Here, we refer to both of these findings as the ‘divergence problem’ (DP), with their causes and scale being debated. If DP is widespread and the result of climatic forcing, the overall reliability of tree‐ring‐based temperature reconstructions should be questioned. Testing for DP benefits from well‐replicated tree …