Effects of increased CO2 concentrations on surface temperature of the early Earth

Abstract

One of the major riddles of terrestrial evolution concerns the history of the Earth's surface temperature. Present models of solar evolution indicate that the luminosity was about 25% smaller at the time of formation of the Solar System1. This factor alone would have caused the Earth's surface temperature to be below freezing, yet the geological record indicates that water has flowed on the surface since at least 3,800 Myr ago2. Enhanced levels of CO2 in the atmosphere could have provided the necessary warming to maintain the temperature above freezing. Increased tectonic activity, and a decrease in solubility of CO2 in the oceans, rock weathering, and sediment deposition are processes that have been suggested for these larger amounts of CO2. We show here that large CO2 concentrations are necessary to maintain the early Earth's surface temperature at approximately today's level. If there were a thousand tunes the present atmospheric level (PAL) of CO2 in the atmosphere, the temperature would be 292K, while a 100-fold increase in CO2 concentration yields 284K. The surface warming is highly dependent on the amount of water vapour and clouds, both of which we have little knowledge of for this very early time in the Earth's history.