The answer is chemical weathering agent.
Carbon dioxide is soluble in water. Aqueous carbon dioxide reacts with water and gets dissolved in it forming carbonic acid. Carbonic acid is dissociate into bicarbonate (HCO₃⁻ ) and carbonate (CO₃⁻ ⁻ ) by loosing protons. Protons are released into water. Thus, dissolving carbon dioxide is a chemical weathering agent.