Hmmm, that answer is pretty retarded!
Carbon dioxide has a solubility of 1.8g/L in water.
Carbon dioxide is leached out of the atmosphere by rain water.
Carbon dioxide is a diprotic acid (pKa1=6.35, pKa2=10.33).
CO2(aq) + H2O <=> H+ + HCO3- pKa1=6.35
HCO3- <=> H+ + CO32- pKa2=10.33