With the rise of the Anthropocene concept, matters of temporality and the properties of historical time have become key issues across the humanities. Even though this turn towards integrated human-planetary timescales is relatively recent, it has a longer prehistory in the environmental sciences, where the need to reconcile human and more-than-human times has been a central concern for decades. Environmental temporalities are, in themselves, historical. By utilising concepts from the theory of history, this chapter shows how environmental historians can provide historical texture to the configuration of environmental pasts, presents, and futures. It traces an evolution in postwar climate science whereby the imperative to grapple with the peculiar times of climate change – systemic, entangled, futural, anthropogenic – led to the emergence of practices aimed at mediating, negotiating, and synchronising vastly different temporalities. We identify two central practices – “planetary timekeeping” and “factoring anthropogenic change” – in this process and trace their origins in a wide range of disciplines. The rise of Earth Systems Science gave the impulse to consolidate climatological research around a single time frame. However, histories of climatological temporalities show a more multiple and processual earth system than the spatial integrity of the “globe” or the “planet” might connote.