  An intriguing problem in climate science is the existence of Earth's glacial
cycles. We show that it is possible to generate these periodic changes in
climate by means of the Earth's carbon cycle as the main determinant factor.
The carbon exchange between the Ocean, the Continent and the Atmosphere is
modeled by means of a tridimensional Lotka-Volterra system and the resulting
atmospheric carbon cycle is used as the unique radiative forcing mechanism. It
is shown that the carbon dioxide (CO$_{2}$) and temperature anomaly curves,
which are thus obtained, have the same first-order structure as the 100 kyr
glacial--interglacial cycles depicted by the Vostok ice core data, reproducing
the asymmetries of rapid heating--slow cooling, and short interglacial--long
glacial ages.
