The OCO-2 Carbon Dioxide (Difference from Global Mean) is a layer that combines OCO-2 XCO₂ (column-averaged dry-air mole fraction) and an estimated daily global trend XCO₂ value that is produced by the National Oceanic and Atmospheric Administration Earth System Research Laboratory Global Monitoring Division (NOAA ESRL GMD). It is calculated from daily averaged CO₂ data from four surface stations and is subtracted from the OCO-2 XCO₂ in order to provide a product that visualizes smaller variations in XCO₂ than the raw XCO₂ product. This is done because increasing atmospheric CO₂ concentrations has resulted in a large range of XCO₂ values over the OCO-2 record.

Carbon dioxide (CO₂) is an odorless, colorless gas and is the fourth most abundant component of dry air (after nitrogen, oxygen and argon). CO₂ is an important greenhouse gas that helps trap heat in the atmosphere. As a part of the carbon cycle, CO₂ can be emitted (e.g. from respiration by plants and soils or from wildfires) or absorbed (e.g. from plant photosynthesis or by dissolving into the oceans). Human activities such as the combustion of fossil fuels and biomass burning are sources of CO₂.

The Orbiting Carbon Observatory-2 (OCO-2) is a three-channel imaging grating spectrometer that collects cloud-free XCO₂ observations continuously over the globe by measuring reflected sunlight in the near-infrared. The OCO-2 Carbon Dioxide parameter is taken from the OCO-2 Level 2 Lite product. OCO-2 makes eight simultaneous, adjacent measurements, each with a spatial resolution of 2.25 km x 1.29 km. These measurements are then mapped onto a 500 m² grid. The repeat cycle for OCO-2 is every 16 days.

References: NOAA/ESRL - Global Greenhouse Gas Reference Network, Data Products and Visualization; Ed Dlugokencky and Pieter Tans, NOAA/ESRL; OCO-2 Carbon Dioxide in GIBS/Worldview