xCO2

XCO₂ is the column-averaged^{[further explanation needed]} of carbon dioxide in the atmosphere, represented in parts per million (ppm). Rather than taking a single observation at the surface, an integration of atmospheric CO₂ above a specific location is observed. The 'X' refers to the observation taking place from a satellite platform. CO₂ observing satellites cannot observe green house gasses directly, but instead average the entire atmospheric column of CO₂. These estimates from satellites need ground truthing to ensure that XCO₂ retrievals are accurate, with an average accuracy from OCO 2 and GOSAT of 0.267 ± 1.56 ppm between September 2014 to December 2016.^[1]

The largest recorded value XCO₂ was recorded during May 2018 over the Northern Hemisphere, with a value of approximately 410 ppm.^[2] These values have been increasing steadily over recent years. Space-based CO₂ measurements are used for climate-level scientific studies such as a further understanding of the El Niño–Southern Oscillation^[3]

• pCO₂
• Carbon dioxide in Earth's atmosphere
• CO₂ observing satellite
• Orbiting Carbon Observatory 2