Ogurtsov M.G., Jungner H., Helama S., Lindholm M., and Oinonen M., 2011. Paleoclimatological evidence for unprecedented recent temperature rise at the extratropical part of the Northern Hemisphere. Geografiska Annaler Series A, 93, 17–26.
Eight, millennial-scale proxy reconstructions of temperature of the Northern Hemisphere were compared to instrumentally measured temperatures. The effect of anomalous reduction in sensitivity over the last decades (divergence) in the tree-ring based records was taken into account. Statistical analyses showed that in the extratropical part of the Northern Hemisphere the time period 1988–2008 was the warmest two decades within the last 1000 years and had a probability of more than 0.70. The established exceptional level of current temperature changes over those areas that were the least disturbed by local anthropogenic impact indicates that over the last two decades the climatic system was perturbed by an additional global-scale forcing factor, which had not operated in the past.