_{2} is perturbed by collisions with other molecules, the weak spin-forbidden magnetic dipole transition *a*^{1}Δ_{g}←*X*^{3}Σ_{g}^{−} shows a broad continuum absorption underlying the sharp lines. This collision-induced enhancement absorption plays a role in the Earth’s atmosphere and much experimental work has been carried out to measure the binary absorption coefficient with different perturber gases. Recent work on the *v*′=0←*v*=0 band in O_{2}–CO_{2} mixtures yielded a value for the coefficient that was approximately three times that of earlier measurements on O_{2}–N_{2} mixtures. In the present note, we calculate the absorption theoretically assuming that the long-range quadrupole-induced dipole mechanism is dominant. Using experimental polarizability matrix elements of CO_{2} and *ab initio*results in the literature for the quadrupolar transition matrix element for O_{2}, we find good agreement for O_{2}–CO_{2} mixtures without any adjustable parameters. The agreement for O_{2}–N_{2} is less good, and because of the much smaller polarizability of N_{2} than of CO_{2}, we suggest that one has to include a short-range component in addition to the long-range one treated here. We also calculate the binary absorption coefficient for O_{2}–H_{2}O, for which no experimental data are available, and we synthesize the corresponding spectrum for use in atmospheric modeling.