Kullman, L. 1998. Tree-limits and montane forests in the Swedish Scandes: Sensitive biomonitors of climate change and variability. Ambio 27: 312-321.
In a review of his personal investigations of "past positional, structural and compositional shifts of tree-limits and upper boreal forests, mainly in the southern Scandes Mountains of Sweden [61-66°N, 12-15°E]," the author concludes that "some exceptionally warm and stable centuries, with high tree-limits and dense montane forests occurred during the Medieval period." He also finds "an episode of warmer climate during the first half of the [20th] century," but notes that "tree-limits and high-elevation forests were far from restored to their medieval levels," which by AD 900-1100 "were situated 80-100 meters higher" than they were about a century ago, i.e., ~1900. And he further adds that "during the past few decades," i.e., during the latter part of the 20th century, there was widespread "rapid cold-induced dieback."