“Length of day correlated to cosmic rays and sunspots“. See? Anthony Watts was right all along! It’s the Sun!
Thus, the [rotation of the] Earth (specifically the mantle), is accelerated or slowed according to the fluctuations of cosmic rays under the influence of solar activity through the zonal winds… (original article – in french)
Oh, the variations are on the order of a 10th of a percent. Well, it’s still all natural. The solar kooks come out in full force in the comments.