High-resolution absorption spectra of the <i>a<sup>1</sup>∆<sub>g</sub>←X<sup>3</sup>Σ<sub>g</sub><sup>−</sup></i> O<sub>2</sub> band measured using cavity ring-down spectroscopy were fitted using the Voigt and speed-dependent Voigt line shapes. We found that the speed-dependent Voigt line shape was better able to model the measured absorption coefficients than the Voigt line shape. Total columns of O<sub>2</sub> were retrieved from ground-based high-resolution absorption spectra from four Total Carbon Column Observing Network (TCCON) sites using both Voigt and speed-dependent Voigt line shapes to calculate absorption coefficients. A lower O<sub>2</sub> concentration was retrieved with the speed-dependent Voigt line shape, with the difference increasing as a function of solar zenith angle. CO<sub>2</sub> total columns were also retrieved from the same spectra using a Voigt line shape and speed-dependent Voigt with line mixing. The column-averaged dry-air mole fraction of CO<sub>2</sub> (XCO<sub>2</sub>) was calculated using the CO<sub>2</sub> and O<sub>2</sub> columns retrieved with both line shapes from measurements made over a one-year period at the four sites and compared. The inclusion of speed dependence reduces the airmass dependence of XCO<sub>2</sub>. The TCCON empirical airmass correction factor for XCO<sub>2</sub> derived from a year of measurements from TCCON sites at Darwin, Lamont, and Park Falls for XCO<sub>2</sub> improved from −0.0071±0.0057 to −0.0012±0.0054 when speed dependence was included. XCO<sub>2</sub> retrieved with the Voigt and speed-dependent Voigt line shapes was compared to aircraft profiles measured at 13 TCCON sites. The bias between the TCCON measurements and the integrated aircraft profile measurements was reduced from 0.9897±0.0005 to 1.0041±0.0005 for XCO<sub>2</sub> retrieved with the Voigt and speed-dependent Voigt line shapes respectively. These results suggest that speed dependence should be included in the forward model when fitting near-infrared CO<sub>2</sub> and O<sub>2</sub> spectra to improve the accuracy of XCO<sub>2</sub> measurements.