‘Rapid’ updating of GHG Budgets using satellite observations

The Regional Carbon Cycle Assessment and Processes (RECCAP) Initiative involves significant effort in gathering together models, in situ, airborne and satellite observations to compile regional assessments of the carbon cycle and by synthesis arrive at a global budget. While a major strength is the compilation of assessments by experts in each region, this exercise also takes multiple years to deliver its assessment, and it is not currently practical to deliver annual assessments especially if the Initiative is expanded to include CH₄ and N₂O as has been proposed.

Space-based measurements of atmospheric concentrations of GHG and observations of both terrestrial and ocean carbon cycle process dynamics are increasing in frequency, range, and detail. With the planned launches of key carbon relevant satellites, in the near future, by NASA, ESA and others, Earth Observation (EO) will provide a unique capability to provide a dynamic reconstruction of the carbon cycle at unprecedented scales in space and time.

The largest uncertainties lie in the terrestrial carbon cycle, from the spatial and temporal distribution of Land Use Fluxes, Source-Sink characterization of terrestrial biosphere and land-ocean fluxes, and their temporal dynamics, in particular intra-annual variability. The ESA-NASA Carbon Budget Reconciliation Challenge involves the development of a framework to provide key updates on carbon cycle state and change in the periods between the current and future RECCAP exercises.

Tackling this challenge element requires that the key changes in GHG stocks and fluxes can be captured efficiently by a relatively small number of variables that can be observed from space, that these variables are consistently generated in space and time and that they are produced with a latency consistent with their use to update regional and global budgets. This presentation highlights the planned approach to be taken by ESA and NASA to coordinate efforts in this direction.