Concrete absorbs carbon from co2 in the air. If you were interested in co2 levels you might be able to deduce something from that. I seem to recall that the

Concrete absorbs carbon from co2 in the air. If you were interested in co2 levels you might be able to deduce something from that. I seem to recall that the biosphere 2 project had problems with the fresh concrete absorbing too much co2 inside the sealed structure. https://www.sciencemag.org/news/2016/11/cement-soaks-greenhouse-gases https://www.sciencemag.org/news/2016/11/cement-soaks-greenho...