Reconstructing Summer Temperatures in Northern Fennoscandinavia Back to A.D. 1700 Using Tree-Ring Data From Scots Pine

Abstract

Estimates of mean July–August temperatures for northern Fennoscandinavia are made back to 1700 using ring width and maximum latewood density chronologies of Pinus sylvestris L. (Scots pine) as predictors. Several prediction models are used and the best results are achieved with a simple two-variable model where climate in year t is estimated as a function of tree growth in years t and t + 1 at each site. The best reconstruction equation accounts for 56% of the temperature variance over a 74-yr fitting period and 45% of the variance over a 39-yr independent verification period. Relatively short-period variability (periods < 10 yr) is better reproduced in the reconstruction than is that at longer wavelengths. The reconstruction indicates that generally cool conditions prevailed across northern Fennoscandinavia around 1716–1724, 1777–1784, 1809–1818, and 1833–1842. Warm periods are reconstructed around 1766–1775 and 1788–1799 and particularly from 1826 to 1831.