Reconstruction of nineteenth century summer temperatures in Norway by proxy data from farmers' diaries.

Proxy data from five farmers' diaries in the More, Dovre and Trondelag regi ons in central Norway were used for climatic reconstruction purposes. The m ethod chosen was "simple linear regression analysis" with the start of the grain harvest (barley or oats) as predictor and summer temperature (May Aug ust) as predictand. Overlapping periods with modern instrumental observatio ns (starting 1858 or later) were used for calibration of the model. The mod el was tested on independent data by establishing the regression on one hal f of the overlapping period and applying the regression on the other half. The standard deviation in the residuals varied from 0.3 degreesC to 0.7 deg reesC and the biases of the mean values from -0.3 degreesC to +0.3 degreesC . Climatic reconstructions were established for the early- and mid-nineteen th century summer temperature, i.e. during the last part of what has come t o be regarded as the "Little Ice Age", in this article considered to end ar ound 1880. By use of the proxy data model, huge inhomogeneities of the "classical" Tro ndheim series were detected, the early nineteenth century part of the serie s evidently being too warm. The inhomogeneity was removed by use of adjustm ent terms. The adjusted series indicates that in the Trondheim region the s ummer temperature during the last part of the "Little Ice Age" phase was ab out 1 degreesC lower than the latest 60 years. This is in serious contradic tion to the classical Trondheim series.