A solar photospheric "thermal profiling" analysis is presented, exploiting the infrared (2.3-4.6 µm) rovibrational bands of carbon monoxide (CO) as observed with the McMath-Pierce Fourier transform spectrometer (FTS) at Kitt Peak, and from above the Earth's atmosphere by the Shuttle-borne ATMOS experiment. Visible continuum intensities and center-limb behavior constrained the temperature profile of the deep photosphere, while CO center-limb behavior defined the thermal structure at higher altitudes. The oxygen abundance was self consistently determined from weak CO absorptions (for C/O≡ 0.5). Our analysis was meant to complement recent studies based on 3-D convection models which, among other things, have revised the historical solar oxygen (and carbon) abundance downward by a factor of nearly two; although in fact our conclusions do not support such a revision. Based on various considerations, an ǫ O = 700±100 ppm (parts per million relative to hydrogen) is recommended; the large uncertainty reflects the model sensitivity of CO. New solar isotopic ratios also are reported: 12 C/ 13 C=80±1, 16 O/ 17 O=1700±220, and 16 O/ 18 O=440±6; all significantly lower than terrestrial. CO synthesis experiments utilizing a stripped down version of the 3-D model-which has large temperature fluctuations in the middle photosphere, possibly inconsistent with CO "movies" from the Infrared

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