The terrestrial forest ecosystems over circum-arctic region have been experiencing significant warming rates and related environmental changes over several decades. Yet, there is uncertainty how these ecosystems respond to the changes due to an insufficiency of such long term records. In this sense, tree rings (ring width indices: RWI) and remote sensing spectral vegetation indices, such as the Normalized Difference Vegetation Index (NDVI) can provide an advantage (adequate temporal resolution and sufficient duration). Trend and important climatic drivers of RWI and NDVI differed significantly with regions, but the way in which they differed was relatively similar between them. The results then have been used in testing several coupled climate–carbon cycle models.
　In this presentation, we show spatial variations of trend and important climatic drivers for the RWI and NDVI over circum-arctic region. Then, we quantify the extent to which the current version of coupled climate–carbon cycle models reproduced the spatial variations and in case of low reproducibility, clarify the cause.