Dendroklimatologisk analys av lokalklimat vid Grövelsjön i Dalafjällen

Sammanfattning: Climate on earth is getting warmer, which effects earth’s energy balance and so forth the ocean and atmospheric circulation.  In many sub-polar regions on the northern hemisphere changes due to warming of the climate can be observed. Some examples that already have been observed are shifts in tree line, towards higher altitudes and latitudes, increased ablation of Swedish glaciers and melting of the permafrost on the Siberian tundra. In Sweden climate change scenarios tell us that it will become warmer and that a higher amount of precipitation in form of rain will be an effect from this. To study climate changes in Sweden, transition zones are useful in order to observe changes in distribution of species and animal populations. This study uses tree rings from Scots Pine (Pinus sylvestris L.) that grow at the tree line in Grövelsjön that is part of the mountains in Dalarna County. By measuring the width of the tree rings, a chronology that is representative for July temperature is made over this area. The method is called dendroclimatology and has generally been used to reconstruct past climate for the last 1000 years.  The results of this study show that the tree ring chronology don’t show a clear increase in temperature for the last century, which could have been expected from an area like this. But the result also show that when instrumentally measured temperature were plotted month by month, the only month with significant up going trend in temperature in this area is April. A temperature change in April does not leave a signal in the tree rings because it is too cold for them to grow that early in the season.