Ciclo del carbono y climala perspectiva geológica

Resumo

The carbon cycle involves the carbon reservoirs in the Earth system (i.e., lithosphere, hydrosphere, biosphere, atmosphere, and rhizosphere) and the carbon fluxes occurring among them. The capacity of each reservoir and the exchange rates are strongly diverse, and because of this, depending on the considered time perspective, different “cycles” will arise. At time scales of millions of years, carbon fluxes are slow and take place essentially between the lithosphere and the “surface system”, these defining the long-term carbon cycle, notably different to the more popular short-term carbon cycle (time scales of years to centuries) which involves the fast fluxes occurring among the biosphere, the oceans, the soils, and the atmosphere. Between the long- and the short-term cycles, many intermediate-scale situations appear which need of new cycle definitions according to time scales. This review concentrates in the long-term carbon cycle, its controlling mechanisms and its consequences during the environmental history of the Fanerozoic. Also, intermediate time-scale carbon perturbations are considered, as the so-called hyperthermals and the Quaternary glaciations. A firm understanding of the carbon cycles from a geological perspective is critical for understanding and evaluating the global perturbation that the cycle is now experiencing, as well as its future consequences.