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Version History (CT2007)
2007 - Released on 28 February 2007
General Release Notes for CarbonTracker 2007
  1. 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.
  2. The CO2 measurements obtained from the Meteorological Service Canada (MSC) currently go through February 2005. This record will be expanded for CarbonTracker 2008.
  3. 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.
  4. 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
  5. 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
  6. 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.
  7. 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.
  8. 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.