Supercontinent assembly and breakup can influence the rate and global extent to which insulated and relatively warm subcontinental mantle is mixed globally, potentially introducing lateral oceanic-continental mantle temperature variations that regulate volcanic and weathering controls on Earth's long-term carbon cycle for a few hundred million years. Whereas the relatively warm and unchanging climate of the Nuna supercontinental epoch (1.8-1.3 Ga) is potentially characteristic of thorough mantle thermal mixing, the extreme cooling-warming climate variability of the Neoproterozoic Rodinia episode (1-0.63 Ga), as well as the more modest but similar climate change of the Mesozoic Pangea cycle (0.3-0.05 Ga) are potentially effects of subcontinental mantle thermal isolation with differing longevity. A tectonically-modulated carbon cycle model coupled to a one-dimensional energy balance climate model predicts the qualitative form of Mesozoic climate evolution expressed in tropical sea-surface temperature and ice sheet proxy data. Applied to the Neoproterozoic, this supercontinental control on can drive Earth into, as well as out of, a continuous or intermittently pan-glacial climate, consistent with aspects of proxy data for the Cryogenian-Ediacaran period. The timing and magnitude of this cooling-warming climate variability depends, however, on the detailed character of mantle thermal mixing, which is incompletely constrained. Furthermore, LIP volcanism, the predominant modes of chemical weathering and a tectonically-paced abiotic methane production at mid-ocean ridges can modulate the intensity of this climate change. In marked contrast, for the Nuna epoch, the model predicts a warm and ice-free climate.