We developed an accurate method to calibrate Raman system for measuring the concentrations of dissolved gases in aqueous geo-fluids at high pressure, and determined CO 2 solubility in water at temperatures from 273.15 to 573.15 K and pressures from 10 to 120 MPa. The Raman peak area ratio (PAR) and peak intensity ratio (peak height ratio, HR) of the upper band (at ∼1390 cm −1 ) of CO 2 Fermi dyad to the OH stretching band of water in homogeneous CO 2 solutions were obtained over wide temperature, pressure, and concentration ranges. Pressure and concentration ( m CO 2 ) show little effects on PAR/ m CO 2 and HR/ m CO 2 , while PAR/ m CO 2 increases linearly with temperature from 273.15 to 573.15 K, and HR/ m CO 2 decreases linearly with temperature at a different rate at temperatures below and above 404.45 K. The solubility data obtained from 298 to 523.15 K are consistent with previous experimental and thermodynamic studies. However, predictions from commonly-used thermodynamic models for temperatures below 298.15 K and above 523.15 K substantially deviate from the new measurements, suggesting that new or refined parameters are needed to improve these models. [ABSTRACT FROM AUTHOR]