Terrestrial planets like Earth have a natural thermostat called carbonate-silicate (Cb-Si) weathering feedback. The Cb-Si feedback is a geochemical cycle that regulates a planet's atmospheric CO2 content over long geological timescales.
When CO2 builds up in the atmosphere, the atmosphere warms. This creates more evaporation and rainfall. Carbonic acid is a weak acid formed in the atmosphere when water combines with carbon dioxide. When a warming atmosphere creates more rain, it also creates more carbonic acid.
Carbonic acid falls on the planet's surface, weathering silicate rocks and removing carbon. The carbon is eventually washed into the sea, where it's taken up in the shells of marine organisms. It falls to the sediment on the ocean floor and is ultimately sequestered back into the crust with help from plate tectonics. The creatures that absorb the carbon into their shells as calcium carbonate play a key role. The carbon in their shells becomes limestone.
This is just the beginning of population-wide characterization of exoplanets and their biotic and abiotic signatures. Instead of looking for the "smoking-gun" signature of life on single worlds, we may be able to detect and identify life through large statistical patterns across numerous worlds. In that case, this work also shows how telescopes with modest observational capabilities can "filter through" the exoplanet population, sparing valuable and expensive observing time on more powerful observatories.