Effects of atmospheric composition on apparent activation energy of silicate weathering: II. Implications for evolution of atmospheric CO2 in the Precambrian

The temperature and PCO2 transitions in the Precambrian were finally calculated based on the relationship between ΔHCO2′, T and FCO2 and the greenhouse effects of CO2. The calculated CO2 levels are high enough that the temperature could have been maintained at >0 °C only by CO2 through the Precambrian. The consistent PCO2 estimates from paleosols (fossil weathering profiles) in the literature support the argument. The calculated temperatures suggest that the Earth could have been cool to hot until around the end of Archean and cool to moderate afterwards.