In this work, we test the hypothesis that clear-sky retrievals may perform as well as full-physics retrievals for very clear scenes. It was found that for simulated OCO-2 measurements, the clear-sky retrieval had errors comparable to those of the full-physics retrieval. For real GOSAT data, the clear-sky retrieval had errors 0–20 % larger than the full-physics retrieval over land and 20–35 % larger over ocean. This work implies that clear-sky retrievals may be more useful than previously assumed.