E continua ... a evidência dendroclimática

"Figure 1: Median ring-widths (non-overlapping 50-year means) of upper forest border Pinus longaeva from 3 sites in western North America, plotted on first year of interval (from Salzer et al, PNAS, 2009)"

RealClimate: A Treeline Story: "Some of the highest growing trees in the world are also the oldest—bristlecone pines (Pinus longaeva) from the Great Basin in the western United States (eastern California, Nevada and Utah). The oldest example is more than 4800 years old. Because of their longevity and growth at high elevations (where the growth of trees is generally known to be limited by temperature) bristlecone pines have been of particular interest to dendroclimatologists (paleoclimatologists who study tree rings to reconstruct past climate). Numerous ecological studies carried out at treeline sites all over the world show that temperature imposes a critical limitation on the ability of trees to produce new tissue; mean daily temperatures of 8-9°C are required, so recent warming will have particular benefits for those trees that have managed to eke out an existence for so long, living “on the edge”."

Considero curioso que o famigerado pico do aquecimento medieval não surja de modo significativo naquele gráfico, mas estamos a falar de uma zona localizada nos EUA.