The Global Terrestrial Observing Network (GT-NET) is envisaged as a master network system. It has been in development since June 1997, when a meeting of experts on ecological networks established that GT-Net should generate complete and coherent data sets on global terrestrial ecosystems through international research collaboration. This project employs satellite and supporting ground observations to expand tier-5 coverage within the terrestrial observing system's GHOST strategy.

These networks are important in developing the capacity and support to gather the required global data on the terrestrial Essential Climatic Variables which were identified in the GCOS Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC. The 13 ECVs are:

1. River discharge

2. Water use

3. Ground water

4. Lake Levels

5. Snow cover

6. Glaciers and ice caps

7. Permafrost and Seasonally-frozen ground

8. Albedo

9. Land Cover

10. Fraction of absorbed photosynthetically active radiation (fAPAR)

11. Leaf area index (LAI)

12. Biomass

13. Fire disturbance

GTOS is assisting in the coordination of the methodology and standards to ensure data compatibility between the different data producers. In addition, in response to the request of the Conference of Parties (COP) of the UNFCCC, GTOS, in consultation with other international and intergovernmental agencies is developing a framework for the preparation of guidance materials, standards and reporting guidelines for terrestrial observing systems for climate, and associated data and products, taking into consideration possible models.