The initial diversification of animals paralleled some of the most dramatic episodes of climate and environmental change in Earth history. We compiled global Neoproterozoic–early Paleozoic detrital zircon age data to track spatiotemporal variations in continental arc systems to explore the influence of tectonic outgassing of CO2 on these climatic shifts. These data indicate that global continental arc systems were spatially reduced at the onset of the Cryogenian glacial interval, widespread during the Cambrian greenhouse, and reduced during Ordovician cooling. The Cambrian greenhouse was coincident with ecologically stressed conditions, whereas Ordovician global cooling was accompanied by a major biodiversification event. Thus, variation in the continental arc CO2 flux likely played a critical role in major climatic fluctuations, which profoundly influenced early animal evolution.