The crucial stages in the geochemical evolution of the Earth's crust, ocean, and atmosphere could be explained by the assumed low-energy nuclear reactions (LENR) that are triggered by seismic activity. LENR result in the fission of medium-weight elements accompanied by neutron emissions, involving Fe and Ni as starting elements, and C, N, O as resultants. Geochemical data and experimental evidences support the LENR hypothesis. The time series analysis highlighted significant correlation between the atmospheric CO2 growth rate and the global seismic-moment release rate, whereas the trending behavior was in response to the anthropogenic emissions. The fluctuations in the atmospheric CO2 growth rate time series were inexplicable in terms of anthropogenic emissions, but could be explained by the cycles of worldwide seismicity, which massively trigger LENR in the Earth's crust. In this framework, LENR from active faults must be considered as a relevant cause of carbon formation and degassing of freshly-formed CO2 during seismic activity.