Greenhouse gases (GHGs) in the atmosphere trap infrared radiation from the Earth, warming it up. This is known as the greenhouse effect. The three main long-lived greenhouse gases are carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O). There are many other greenhouse gases, for example, Sulphur hexafluoride (SF₆), and together these have a significant influence on the climate.

Over decades, the temperature of the Earth changes in response to the rate at which energy enters and leaves the Earth system. On shorter time scales, temperature changes are also driven by movements of energy within the earth system. Near-surface temperature is monitored using measurements over land and ocean. Global mean temperature combines temperature measurements over land and ocean, while land air temperature covers land areas only.