Atmospheric carbon dioxide (CO2) is a primary greenhouse gas that has persistently increased over the past few decades. It is a major driver of regional and global climate change. Most CO2 sources and sinks are located near the surface. Observations from shortwave infrared sounders loaded on satellite, such as the Greenhouse Gases Observing SATellite (GOSAT) and Orbiting Carbon Observatory (OCO-2) can provide accurate measurements of the column-averaged atmospheric CO2 concentration.