What's New in CarbonTracker 2007B?
- Observations and flux estimates for 2006
- Revised flux estimates for 2000-2005
- New observations from three sites were added, Sable Island, Nova Scotia (Environment Canada), Storm Peak and Niwot Ridge, Colorado (National Center for Atmospheric Research)
- Several improvements that we feel result in more accurate estimates of fluxes
- CO2 Weather Movies
- Plots of residual (model minus obs) times series for each site
- Expanded CarbonTracker netCDF products. 4-D CO2 mole fraction are now available at 6-hourly resolution, and 1° x 1° fluxes are available at 3-hourly resolution.
For a complete description about this release and previous releases, please see Version History.
New fossil fuel emissions: In CarbonTracker, fossil fuel emissions are specified and not optimized by observations. New global emissions data have recently become available, and we have used them to update and improve our fossil fuel emissions estimates. In addition to updates of the 2000-2004 fossil fuel data, we now rely less upon extrapolation of older inventories. For the entire period 2000-2005, the fossil fuel emissions used in CT2007B are higher than those from CT2007. Additionally, regional trends have changed. Details are available in documentation and release notes. One prominent difference in CT2007B compared to CT2007 is a steepening of the emissions trend in Asia that results in fossil fuel emissions now averaging about 0.75 PgC/yr higher for the period 2003-2005. However, because Temperate Eurasia is not very well constrained by our observations, this increase has very little impact on the fluxes from the terrestrial biosphere. Between 2003 and 2005, the biosphere sink in the Temperate Eurasia region increased by less than 0.05 PgC/yr. In contrast, North American (Temperate and Boreal) biosphere fluxes were affected by changing fossil fuel, but in a somewhat complex way. The previously reported drought in 2002 now appears stronger, with a sink of only 0.1 PgC/yr (instead of 0.3 PgC/yr in CT2007), but other years show larger sinks, keeping the 2000-2005 means roughly the same.
New CO2 measurement sites: In addition to including 2006 data for all the measurement records for sites present in the previous CarbonTracker (CT2007), we have added three new measurement sites: Sable Island, Nova Scotia (from Environment Canada) and two high altitude sites in Colorado -- Niwot Ridge and Storm Peak (from the National Center for Atmospheric Research). For 2006, the impact of adding the Colorado sites is to reduce the total North American sink by about 0.1 PgC/yr.
New ocean flux first guess: The CarbonTracker data assimilation system relies on first guesses of surface fluxes that are then modified to agree with CO2 observations. In places where we have few atmospheric observations, like the tropics and southern hemisphere, these first guess fluxes can be very important. Our new first guess ocean flux fields are based on measurements of carbon in the ocean interior--independent of atmospheric observations--and are a likely improvement over the surface ocean pCO2 climatology used in the CT2007. Details can be found in the updated documentation. Global ocean uptake has increased from about 1.5 PgC/yr (CT2007) to 1.8 PgC/yr (CT2007B) due mostly to the new first guess ocean fluxes. Regional changes are consistent with off-line comparisons of the Takahashi et al. (2002) flux product used in CT2007 and the Jacobson et al. (2007) flux product used in CT2007B. Compared to CT2007, CT2007B is characterized by a smaller high-latitude sink (-.45, down from -.84), more profound temperate latitude uptake (-2.1, up from -1.6), and less tropical outgassing (0.75, down from 0.96). All fluxes are in PgC/yr.
Updated fire emissions: In CT2007, fire emissions for 2005 from the GFEDv2 database were not available when our analysis was performed. As a stop-gap measure, 2000-2004 climatological fire emissions were used for the 2005 calendar year. In CT2007B, GFED fire emission estimates are available for every year including 2006. As a result, the fire emissions in CT2007B are specific for each year in consideration. The effect of changing 2005 fire fluxes from 2000-2004 averages to a year-specific estimate had a notable effects in the Tropical Asia, Tropical South America regions, where estimated fire fluxes increased by 0.11 and 0.17 PgC/yr, respectively. In the Boreal Eurasia region, fire fluxes from fires decreased by 0.10 PgC/yr.
How do flux estimates from CarbonTracker 2007B compare with CarbonTracker 2007?