(a) Explanation for the enigmatic bias (+0.1 ms/cy) that arises when closing the budget of the secular ΔLOD trend based on the sum of tidal friction (+2.4 ± 0.01 ms/cy) and GIA (−0.8 ± 0.1 ms/cy). (b) Origin of the bias determined by accounting for plate tectonics (+0.04 ± 0.02 ms/cy) and changes in the rate of tidal friction under climate change (+0.06 ± 0.01 ms/cy; see Appendix B.3). The shaded gray area shows the range of independent estimates of possible changes in the rate of tidal friction (0.024–0.12 ms/cy), computed based on tidal models (which include the effects of stratification and sea level rise; Appendix A.3).