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Version History (CT2007B)
Please click here for a comparison of flux estimates derived from the current release and the previous release.

Release Notes for CarbonTracker 2007B
  1. Product
    • Released on 20 December 2007
    • CT2007B flux estimates are available from 2000 through 2006 (the previous CT2007 release covered through 2005)
    • Documentation is updated for CT2007B
    • A flux summary table has been added comparing CT2007 and CT2007B total fluxes
  2. Observations
    • New daytime average data have been added for Sable Island, Nova Scotia, Canada (SBL_06C3, beginning June 2003)
    • New nighttime average data have been added for Niwot Ridge, Colorado, United States (NWR_03C3, beginning August 2005)
    • New nighttime average data have been added for Storm Peak Lab, Colorado, United States (SPL_03C3, beginning September 2005)
    • CO2 mole fractions are now based on flask pair averages rather than the first flask of a pair only.
    • Data for Fraserdale, Ontario, Canada (FRD_03C3) have been reprocessed based on the Environment Canada submission to WMO.
    • Time averaging for FRD_03C3 has been shifted by one hour based on new information about reported times.
    • Time averaging for observatory sites has been changed to exclude erroneous hours for sites close to the international dateline.
    • A few recent flask data points have had their Quality Control flag values revised and are now excluded.
    • LEF data for 2000-2003 is revised based on the use of Licor-1 values rather than Licor-2. Two CO2 sensors were present at the 396m level of LEF, but it was determined that the Licor-1 was more reliable.
  3. Fossil Fuels
    • Fossil fuel estimates in the previous release (CT2007) were based on global emission inventories from CDIAC only until 2002. For 2003 and 2004, global totals were linearly extrapolated using the average percentage increase of the previous 10 years, and for 2005, emissions from 2004 were simply repeated. Spatial patterns were based on linearly interpolated and extrapolated EDGAR emissions estimates for 1995 and 2000. For CT2007B, global totals are used from CDIAC through 2004, and 2005 and 2006 data are extrapolated based on energy consumption statistics from BP for those years. The coarse spatial patterns are now derived from CDIAC and BP country statistics, and only the within country patterns come from EDGAR. Both global totals and regional trends are different, especially after 2002. Please see documentation for more information.
  4. Fires
    • A new GFED v2 release has been implemented and runs to the end of 2006, correcting an issue in which fires for 2005 were not available.
  5. Biosphere
    • The biosphere fluxes are consistent with the new GFED v2 release and complete through the end of 2006.
  6. Ocean
    • Ocean prior fluxes are now based on Jacobson et al. (2007) estimates rather than Takahashi et al. (2002). Please see documentation for more information.
  7. Data Assimilation and Transport Modeling
    • CarbonTracker inverts for 30 ocean regions in CT2007B rather than 11. These finer regions are a superset of the 11 TransCom ocean regions, and can be simply aggregated to the coarser regions.
    • A new ecoregion mask was created with improved land/ocean mask near the coasts, causing shifts in the total area of some coastal ecoregions.
    • In CT2007, the month of December 2005 was run without the 1x1 degree zoom region. For that month, transport was simulated at 3x2 degrees in that region. In CT2007B, the 1x1 zoom ECMWF meteorology was available throughout the end of October, 2006. As a result, the present release has 1x1 degree analysis through October 28, 2006, and 3x2 meteorology for the remaining eight weeks.
    • At the end of 2005, ECMWF changed the vertical resolution in its model from 60 to 91 layers. For use in the TM5 offline transport model, the 60-layer model results are reduced to 25 layers. Similarly, the 91-layer results are reduced to 34. As a result, the transport model has a 25-to-34 level discontinuity at the end of 2005. We have integrated over this transition by interpolating the CO2 fields to the higher resolution, using a mass-conserving algorithm.

Release Notes for CarbonTracker 2007
  1. This is a link to the CarbonTracker 2007 archive.
  2. Released on 28 February 2007.
  3. CarbonTracker 2007 has a number of caveats for the year 2005 listed below. These shortcomings will most likely lead to revised flux estimates for this year in our next CarbonTracker release (2008). Most importantly, we expect the total uncertainty on the 2005 estimate to become smaller even than the estimate of 2004, as more observations become available for assimilation.
  4. The CO2 measurements obtained from the Meteorological Service Canada (MSC) currently go through February 2005. This record will be expanded for CarbonTracker 2008.
  5. The month December of 2005 was run without the United States 1x1 degree zoom region in the transport model. This is due to a change in model resolution in the parent model from ECMWF in February of 2006. We expect future CarbonTracker releases to be able to integrate past this moment in time as we develop the software to deal with this discontinuity.
  6. The 2005 fossil fuel emissions are identical to those used in 2004. Although economic statistics are available to extrapolate the fossil fuel emissions from previous years, we did not include this information in version 2007. We expect better fossil fuel emission estimates for 2005 to be included in CarbonTracker 2008
  7. The 2005 fire emissions are the climatological average of those used in 2000-2004. The new GFED2 release (weekly fluxes through 2005) came out too late to be incorporated in CarbonTracker 2007
  8. Annual mean uncertainties for CarbonTracker 2007 are calculated as the annual average of the 52 weekly estimated covariances. This estimate does not include any temporal covariances in the fluxes which would substantially reduce uncertainty. We feel that until we have implemented a proper mechanism to propagate such information through time, we can not objectively quote the true uncertainty on the annual mean that would result from the assimilation of all the observations. Our current number is supposed to represent a conservative estimate of the real uncertainty to be compared to previous flux estimates.
  9. Uncertainty maps on the fluxes show smaller uncertainties in the tropics than in the extra-tropics. This is counter-intuitive as the tropical carbon cycle is least well understood and most poorly constrained by observations. In recognition of this, CarbonTracker 2007 uses strong covariances on ecosystems in the tropical regions. The variance on each region is lowered to limit the resulting total uncertainty per continent. Since our maps only show variances per region, and not covariances, this fact is not reflected in the mapped product.
  10. Fossil fuel emissions can occur over regions characterized as ocean. This is partly due to real emissions from international shipping, and partly due to emissions occurring in coastal land regions that are assigned to the ocean in our coarse 1x1 degree aggregation scheme. The same is true for fossil fuel emissions over non-optimized regions such as ice, polar deserts, and inland seas. This problem shows up only when aggregating to larger land, ocean, or continental regions for interpretation, but has no influence on the assimilation process itself.