• Observations and flux estimates for 2007
• Revised flux estimates for 2000-2006
• Discrete observations (~weekly) from the Commonwealth Scientific and Industrial Research Organization (CSIRO) network of discrete sampling sites in the high southern hemisphere have been added. Sites include Cape Grim, Tasmania, Australia (CGO_02D0); Cape Ferguson, Queensland, Australia (CFA_02D0); Macquarie Island, Australia (MQA_02D0); Mawson Station, Antarctica, Australia (MAA_02D0); Casey, Antarctica, Australia (CYA_02D0).
• Quasi-continuous observations (incorporated as daily afternoon averages) from Southern Great Plains, Oklahoma (SGP_64C3, Lawrence Berkeley National Laboratory) and Egbert, Ontario (EGB_06C0, Environment Canada) have also been included.
• CO2 observations used in CarbonTracker assimilation are now available for download, in netCDF format (one file per site). See details below.
• Enhanced CarbonTracker netCDF products. Optimized 4-D CO2 mole fraction are now available at 3-hourly resolution for the entire time period.

For a complete description about this release and previous releases, please see Version History.

Updated Fossil Fuel emissions: In CarbonTracker, fossil fuel emissions are specified and not optimized by observations. However, changing the imposed fossil fuel fluxes can have an impact on optimized biosphere (and to a lesser extent, ocean) fluxes. Fossil fuel emissions in CT2008 now have seasonal cycle in Eurasia. This change from no seasonal cycle to one with an amplitude of about 15% appears to have had only a very small impact on the optimized fluxes. In Europe, Eurasia Boreal and Eurasia Temperate, annual means are basically unchanged, and the amplitude of the seasonal cycle of the biospheric fluxes has been reduced by less than 5%. [A comprehensive CarbonTracker product evaluation is coming soon.]

New observations: The time span of SGP_64C3 is 2003 and 2004, and EGB_06C3 starts in 2005 and continues through the end of 2007. Based on tests in which SGP_64C3 and EGB_06C3 were added to the CT2007B configuration, both sites influence the cropland/grassland ecoregion within temperate North America by increasing summertime uptake. Annual mean uptake is increased by less than 0.1 PgC/yr for North America. The impact of the CSIRO Southern Hemisphere sites on the optimized fluxes is less pronounced, with all changes less than 0.05 PgC/yr. The biggest changes between CT2007B and CT2008 appear in the Southern Ocean and Australia. [A comprehensive CarbonTracker product evaluation is coming soon.]

Availability of observational data: We are pleased to announce that the observations as they have been prepared for use in the CarbonTracker assimilation system, and the model simulations of those observations are now available for download. Users should understand that these data are NOT the actual measurements, but preprocessed observational constraints. Preprocessing is done on the actual observations mainly to convert them into a form which is more easily simulated by the TM5 transport model. For instance, at sites with quasi-continuous observations, we compute 4-hour average CO2 mole fractions during well-mixed, background conditions. At many sites this corresponds to afternoons from noon to 4pm local time, when the planetary boundary layer is well-established. At some mountain sites, like Mauna Loa and Niwot Ridge, the 4-hour averages are computed at nighttime, when background winds prevail. Another preprocessing step we take is to average duplicate flasks when they are available. Duplicate samples are collected for quality control purposes. In all cases, users interested in analyzing these CO2 mole fractions should contact the original data providers for access to the actual observations. Please refer to Collaborators for contact information.

How do flux estimates from CarbonTracker 2008 compare with previous releases?