The absorption coefficient in the R-branch of the 4.3 mm CO2 band at temperatures and pressures typical of atmospheric conditions was calculated on the basis of the spectral line wing theory. The results obtained are presented. At some frequencies of interest for remote sensing there is inversion of the temperature dependence which is more pronounced in the case of self-broadening. It is pointed out that the transformed integrand for the spectral intensity of outgoing radiation with an unconventional form of the weighting function associated with dT/dz may be used for temperature retrieval.