More "reactive" land surfaces cooled the Earth
Reactivity describes how easily chemical compounds or elements take part in a reaction," explains Friedhelm von Blanckenburg. If there are more non-weathered and therefore more reactive rocks at the surface, these can in total react as extensively chemically with little CO2 in the atmosphere as already heavily weathered rocks would do with a lot of CO2. The decrease in CO2 in the atmosphere, which is responsible for the cooling, can thus be explained without an increased speed of weathering.