FIGURE 2. Spectral analysis of the methane record.
From the following article:
Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years
Laetitia Loulergue, Adrian Schilt, Renato Spahni, Valérie Masson-Delmotte, Thomas Blunier, Bénédicte Lemieux, Jean-Marc Barnola, Dominique Raynaud, Thomas F. Stocker & Jérôme Chappellaz
Nature 453, 383-386(15 May 2008)
doi:10.1038/nature06950
a, Amplitude of orbital periodicities in the methane record for the time ranges 0–400 kyr and 400–800 kyr, using the multi-taper method (MTM) with normalized data. The 19-kyr component is absent at 400–800 kyr because of its statistical non-significance (F-test <0.95, see Supplementary Information). b, Orbital components and residuals (expressed in p.p.b.v. on the centred signal) of the CH4 record over the past 800 kyr. The red line combines the three periodicities. Note that the amplitude of the orbital components and residuals is similar (
200 p.p.b.v.). The residual CH4 signal contains other statistically significant periodicities at 4.8 and 8.7 kyr and another periodicity at 10–11 kyr slightly below the confidence limit, not discussed here.
