Transient climate evolution sounds familiar for anyone who thinks about anthropogenic global warming. For Earth’s geological history, it is more common to think in terms of steady states (Warmhouse versus Icehouse, for instance). This tendency is perhaps more frequent among modelers, for it is easier to model a steady state.

I want here to make the case that the evolution of climate during Earth’s geological history is likely not an affair of steady states. Long-term climate is in interaction with interlocked global geochemical cycles (carbon, oxygen, sulfur…) whose processes and characteristic timescales range from seasons to tenths of million years. Earth is rather in a permanent transient evolution between everchanging unbalanced forces.

I will present three examples where a combination of different timescales may have shaped Earth’s climate:

1. the consequences of Pliocene “permanent El Niño” on the silicate weathering carbon sink,
2. the roles of orbital cycles in Cretaceous anoxic events and climate, and
3. the effect of increased sulfide oxidation by mountain uplift on global geochemical cycles and climate.

Lieu
Laboratoire des Sciences du Climat et de l’Environnement (LSCE-IPSL)
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