A new study by Horst-Joachim Lüdecke and Carl-Otto Weiss published in The Open Atmospheric Science Journal earlier this year predicts that global temperatures will cool for the next 30 years. The study uses a large number of proxy data sets to create a global temperature mean they call G7 spanning the last 2000 years. Their harmonic analysis of G7 identifies three significant cycles with periods of ~1000, ~460, and ~190 years. Using these three components alone shows a very strong Pearson correlation of .84 with the 31-year running average of G7. And the three-component curve exhibits all the major temperature extremes of the last 2000 years including the Roman, Medieval, and the current warm periods, as well as the 1450 minimum of the Little Ice Age. The paper also provides new proof that the ~190-year cycle is caused by the sun. The three-component temperature curve further predicts that global temperature will drop from the present to 2050, followed by a slight rise from 2050 to 2130, and a further drop from 2130 to 2200.
Fig. (2) (Color online) Left panels: Temperature records [oC] as anomalies around the mean, of Chr, Bün, McK, Vill-N, Vill-S, Pet, and the composite global record G7. The record of common production rate PC of the cosmogenic nuclides 14C and 10Be, Stei, is depicted in panel row 4, column 2. Right panels: Pertinent Fourier spectra with false-alarm lines of 95% (green) and 99% (red). The period of the strongest peak (generally ~190 year) is given.