Longitude profiles of the intensity for CO lines for the Galactic plane. The intensity in each bin represents the average over 5° in Galactic longitude and ±0﹩\fdg﹩5 in Galactic latitude, under the assumption that the emission is dominated by an unresolved line at the Galactic plane. The 2 σ error bars include detector noise and gain uncertainties. There are few measurements in the ﹩l=90^{\circ }﹩ bin, so we caution against overinterpretation of results that are based only on this data point. The transitions are noted on the plots. Note that the CO 7–6 transition plot also contains the C I 2p²:³P₂–³P₁ transition at 370.4 μm.