In dendroclimatology the term "Divergence" describes how between late 20th century tree-ring chronologies and regional temperature trends no longer adhere as closely as observed in the past. This presents a central problem to contemporary paleoclimate research. If divergence also occurred during historical warmth, this non-stationary proxy behavior would invalidate all large-scale climate reconstructions integrating tree-ring data. However, none of the hypotheses published over the past two decades could rigorously be tested and explain the problem. The vision is to develop a forward density model and a hemispheric scale tree-ring network to study non-linear growth responses to rapid climate warming and explain divergence using inverse modelling techniques.