An integral estimation of tree-ring chronologies from subarctic regions of Eurasia

Abstract

Introduction Using the results of climatic models, some authors state that recorded global warming is directly related to the increased concentration of greenhouse gases in the atmosphere caused by the anthropogenic activity. Quantitative estimations indicate an increase in the average annual temperature in Northern Hemisphere by 0.5-0.6C (Mann et al. 1998, Jones et al. 2001). According to calculations based on climatic models, the strongest warming should be observed in the high latitudes of the Northern Hemisphere, with an increase of 34C (Kelly et al. 1982, Budyko and Israel, 1987). However, data obtained from analyses of the radial growth of trees from the sub-Arctic area of Eurasia, an area closely tied to strongest temperature changes, do not show significant changes in climatic conditions (Briffa et al. 1998, Naurzbaev and Vaganov 2000). There is also the unresolved issue of the range of natural climate fluctuations, i.e. the amplitude of near-surface air temperature changes in the high latitudes of the Northern Hemisphere during the Holocene. Tree-ring chronologies serve as a reliable instrument for the reconstruction of natural temperature fluctuations in the high latitudes over millennial time scales. Compared to the other indirect sources of climate information, these tree-ring chronologies have important advantages: Firstly, climatic information is distinctly recorded in annual tree-rings (Briffa et al. 1998, Naurzbaev and Vaganov 2000, Naurzbaev et al. 2001). Secondly, at the northern boundary of the Eurasian forests, trees reach a maximum age of 1216 years and the net of dendro-climatic “stations” evenly distributed over a vast territory of Siberia permits spatial and temporal reconstructions of temperature variation (Vaganov et al. 1999, Sidorova and Gerasimova 2005); and finally dead trees, preserved in permafrost, offer the opportunity of obtaining tree-ring chronologies over longer Holocene time scales (Shiyatov 1986, Vaganov et al. 1996, Vaganov and Naurzbaev 1999, Hantemirov 1999, Hughes et al. 1999, Naurzbaev et al. 2002, Sidorova 2001, 2003, Hantemirov and Shiyatov 2002, Grudd et al. 2002).