concept

Silicate weathering

The slow reaction between carbon-dioxide-bearing rainwater and exposed silicate rock, which turns minerals into dissolved ions and pulls CO₂ out of the atmosphere in the process. What makes it a planetary thermostat is its temperature dependence: warmer rock with more water running over it reacts faster, so a warming world automatically draws down more CO₂ and cools back. The mechanism works on a hundred-thousand to million-year timescale — long enough to hold a climate steady across geological time, and far too slow to help with any disturbance measured in centuries.