New Paper Claims 250 Year Climate Cycle

A new paper from Germany purports to demonstrate that the 20th century warming trend can largely be explained by the long-term climate periodicities over the last 2000 years, the most important being a  ~250 year cycle

In a recent paper [1] we Fourier-analyzed central-european temperature records dating back to 1780. Contrary to expectations the Fourier spectra consist of spectral lines only, indicating that the climate is dominated by periodic processes ( Fig. 1 left ). Nonperiodic processes appear absent or at least weak. In order to test for nonperiodic processes, the 6 strongest Fourier components were used to reconstruct a temperature history.

Fig. 1: Left panel: DFT of the average from 6 central European instrumental time series. Right panel: same for an interpolated time series of a stalagmite from the Austrian Alps.

Non-periodic components would include any recent warming due to CO2 which would not be a recurring pattern in the climate.

Fig. 2 shows the reconstruction together with the central European temperature record smoothed over 15 years (boxcar). The remarkable agreement suggests the absence of any warming due to CO2 ( which would be nonperiodic ) or other nonperiodic phenomena related to human population growth or industrial activitiy.

For clarity we note that the reconstruction is not to be confused with a parameter fit. All Fourier components are fixed by the Fourier transform in amplitude and phase, so that the reconstruction involves no free ( fitted ) parameters.

15 year running average from 6 central European instrumental time series (black). Reconstruction with the 6 strongest Fourier components (red).

The dominant frequency in the series is approximately 250 years, and that component is currently at it's maximum point, which would be consistent with a rapid rise in the 20th century, and the current "leveling off" of global temperatures.  Note that the predicted line on the graph to the right now predicts a decline in global temperature.

Thus the overall temperature development since 1780 is part of periodic temperature dynamics prevailing already for ~2000 years. This applies in particular to the temperature rise since 1880, which is officially claimed as proof of global warming due to CO2, but clearly results from the 250 year cycle. It also applies to the temperature drop from 1800 ( when the temperature was roughly as high as today, Fig. 4 ) to 1880, which in all official statements is tacitly swept under the carpet. One may also note that the temperature at the 1935 maximum was nearly as high as today. This shows in particular a high quality Antarctic ice core record in comparison with the central-european temperature records.

Bear in mind, this is not a physical predictive model, it is strictly a statistical model that does not purport to explain the reasons for the variation.  However, for them to be consistent over a long period, they are probably astronomical, either earth orbit changes, or cyclic patterns in the sun.

Expect a furious response from the AGW community.  I guess time will prove who is right in the next 10-20 years.  Original paper can be downloaded here:

www.clim-past.net/9/447/2013/cp-9-447-2013.pdf

Of course, I found this at Watts Up With That.