Evaluation of a reconstruction of winter and summer temperatures in the Low Countries, AD 764-1998

A new reconstruction of winter and summer temperatures in the Low Countries (the present-day Netherlands and Belgian Flanders), based upon documentary evidence from AD 764 to 1705 and extended by observations to 1998, is compared with relevant paleo series from the European paleo network. Over the period back to ~1300, and in the range of timescales from annual to centennial, the Low Countries Temperature (LCT) reconstruction is well supported by existing evidence in both seasons. The spectral analysis confirms that the dominant oscillations in the LCT have counterparts in independent data and that most of periodicities characteristic for the instrumental segment of the LCT are preserved in the reconstruction. No inhomogeneity of the variances could be detected over this period of reliable reconstruction in both seasons. Prior to ~1300, the evaluation of the LCT is hampered because of scarcity of independent data. Some support for the LCT on decadal and centennial timescales could still be added in the 12th and 13th centuries; for the earliest three centuries of the reconstruction, however, the independent data are lacking.

Over the last ~700 years, the LCT series exhibit significant season dependent variability on bidecadal and centennial timescales. The seasonality is particularly striking in the 15th century which is on average warm in summer while cold in winter. The 20th century is by far (three standard errors) the warmest century of the last millennium in terms of winter temperatures, while the 13th century is warmest in terms of summer temperatures, but by the narrow margin (one standard error). The coldest centennial period is centered around 1600 in both seasons. The present results place the reconstructed LCT series within the existing paleoclimatic network, and provide insight into variability of temperature in the Low Countries through centuries