Autor: H.-j. Lüdecke, A. Hempelmann, C.o. Weiss

H.-J. Lüdecke, A. Hempelmann, and C.O. Weiss: Multi-periodic climate dynamics: spectral analysis of long-term instrumental and proxy temperature records, Clim. Past., 9, 447-452, 2013, doi:10.5194/cp-9-447-2013, www.clim-past.net/9/447/2013/

Abstract:
The longest six instrumental temperature records of monthly means
reach back maximally to 1757 AD and were recorded in Europe. All six
show a V-shape, with temperature drop in the 19th and rise in the
20th century. Proxy temperature time series of Antarctic ice cores
show this same characteristic shape, indicating this pattern as a
global phenomenon. We used the mean of the 6 instrumental records
for analysis by discrete Fourier transformation (DFT), wavelets, and
the detrended fluctuation method (DFA). For comparison, a
stalagmite record was also analyzed by DFT. The harmonic
decomposition of the above mentioned mean shows only 6 significant
frequencies above periods over 30 yr. The Pearson correlation
between the mean, smoothed by a 15 yr running average (boxcar) and
the reconstruction using the 6 significant frequencies yields r =
0.961. This good agreement has a 99.9% confidence level
confirmed by Monte Carlo simulations. It shows that the climate
dynamics is governed at present by periodic oscillations. We find
indications that observed periodicities result from intrinsic
dynamics.