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GCOS Essential Climate Variables

The 50 GCOS Essential Climate Variables (ECVs) (2010) are required to support the work of the UNFCCC and the IPCC. All ECVs are technically and economically feasible for systematic observation. It is these variables for which international exchange is required for both current and historical observations. Additional variables required for research purposes are not included in this table. It is emphasized that the ordering within the table is simply for convenience and is not an indicator of relative priority.


GCOS Essential Climate Variables


(over land, sea

and ice)


Surface:[1] Air temperature, Wind speed and direction, Water vapour, Pressure, Precipitation, Surface radiation budget.


Upper-air:[2]     Temperature, Wind speed and direction, Water vapour, Cloud properties, Earth radiation budget (including solar irradiance).


Composition: Carbon dioxide, Methane, and other long-lived greenhouse gases[3], Ozone and Aerosol, supported by their precursors[4].




Surface:[5]        Sea-surface temperature, Sea-surface salinity, Sea level, Sea state, Sea ice, Surface current, Ocean colour, Carbon dioxide partial pressure, Ocean acidity, Phytoplankton.


Sub-surface:  Temperature, Salinity, Current, Nutrients, Carbon dioxide partial pressure, Ocean acidity, Oxygen, Tracers.




River discharge, Water use, Groundwater, Lakes, Snow cover, Glaciers and ice caps, Ice sheets, Permafrost, Albedo, Land cover (including vegetation type), Fraction of absorbed photosynthetically active radiation (FAPAR), Leaf area index (LAI), Above-ground biomass, Soil carbon, Fire disturbance, Soil moisture.


[1] Including measurements at standardized, but globally varying heights in close proximity to the surface.

[2] Up to the stratopause.

[3] Including nitrous oxide (N2O), chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), sulphur hexafluoride (SF6), and perfluorocarbons (PFCs).

[4] In particular nitrogen dioxide (NO2), sulphur dioxide (SO2), formaldehyde (HCHO) and carbon monoxide (CO).

[5] Including measurements within the surface mixed layer, usually within the upper 15m.