Question

In mid-nineteenth-century glaciology, the prevailing consensus attributed the erratic distribution of colossal boulders across Northern Europe to catastrophic ice-rafting during a universal deluge. While Louis Agassiz famously proposed an alternative—that vast continental ice sheets had physically transported the debris—his hypothesis was initially discounted by contemporaries who cited the apparent absence of a modern physical mechanism capable of generating such continental-scale glaciation. To bridge this conceptual gap, Agassiz’s associate, Edward Forbes, highlighted thermal oscillations recorded in alpine glacier ice cores, arguing that minor thermodynamic shifts could precipitate self-reinforcing ice-sheet expansion. However, recent reassessments by climate historians suggest that Forbes’s thermodynamic calculations relied on flawed barometric measurements, rendering his theoretical bridge an empirical assertion rather than physical proof. Nevertheless, Forbes's intervention proved pivotal: by reframing the debate from speculative catastrophism to quantifiable thermodynamic processes, he forced orthodox geologists to engage Agassiz’s framework on empirical terms, thereby catalyzing the paradigm shift toward modern glacial theory.

Which of the following best describes the rhetorical function of the sentence beginning with 'However, recent reassessments by climate historians suggest' in the context of the overall passage?