Glacialeither

Glacialeither is a neologism used in conversations within paleoclimatology to describe a hypothetical dual-path mechanism governing the onset and termination of glacial states. In this conception, a given glacial phase can emerge through two alternative routes: one driven primarily by external orbital forcing (Milankovitch cycles), and another arising from internal climate variability and feedbacks, such as ocean–atmosphere dynamics and greenhouse gas changes. The term signals a bifurcation in the system's response, where similar external conditions might lead to different climate trajectories depending on the dominant pathway.

The word fuses glacial with either to emphasize the choice between two routes. It is not an established theory; rather, it appears in speculative discussions and scenario-building exercises intended to explore the role of internal variability in glacial cycles.

In a glacialeither framework, models would allow both routes to contribute and test under what conditions one pathway or the other governs. Orbital forcing could still set the seasonal and regional climate context, while internal feedbacks could push the system toward a glaciated state when thresholds are crossed, creating potential bistability and abrupt transitions.

Critics note that without robust empirical criteria, the concept risks overgeneralization. It remains a heuristic device rather than a formal theory, and current evidence favors an important but not exclusive role for orbital forcing in glacial cycles; internal dynamics modulate timing and amplitude. Related topics include Milankovitch cycles, glacial cycles, and climate bistability.