This is a question about residence time for another planet with the following information below:
When we arrive on the second habitable planet, we discover that it is also exactly like Earth, except that each year its volcanoes emit 1000 GtC, and its ocean precipitates 1000 GtC as calcium carbonate. The citizens of this planet had been burning fossil fuels, but after we teach them about the dangers of climate change, they decide to switch entirely to solar power. About how long does it take for their atmosphere to return to its pre-industrial equilibrium value?
Everything else about the planet is identical to earth unless otherwise specified.