TABLE 4.4 Potential Improvements in National Emissions Estimates from Atmospheric and Oceanic Measurements and Models

Gas

Major Sectors or Activities

Current Uncertainty for Annual National Emissions

Possible Improvements in 3-5 Years

Uncertainty of Improved Methods

CO2

Large local sources (e.g., cities, power plants)

5

CO2 satellite program, including an OCO replacement, new in situ measurements in cities, and a research program to guide network design and satellite validation

2 (annual)

1 (decadal change)

CO2

Fossil-fuel combustion

4-5

Improved tracer-transport inversion through new observations (14CO2, additional ground stations, OCO replacement) and data assimilation

1-3 (annual)

1-2 (decadal change)

CO2

Agriculture, forestry, and other land-use net emissions

5

Improved tracer-transport inversion through new satellite and in situ observations

5

CH4

Total anthropogenic

3-5

Improved tracer-transport models, new satellite and in situ observations, and improved emission models through research

2-3

N2O

Total anthropogenic

4-5

Improved tracer-transport and emission models, additional observations

3-5

CFCs, PFCs, HFCs, and SF6

Industrial processes

4-5

Gridded inventories, improved tracer-transport inversion, and measurement of correlated variations of gases

2-5

NOTES: 1 = <10% uncertainty; 2 = 10-25%; 3 = 25-50%; 4 = 50-100%; 5 = >100% (i.e., cannot be certain if it is a source or sink). Ranges represent emission uncertainties in different countries (e.g., 1-3 means that uncertainties are <10% in some countries, 10-25% in some, and 25-50% in others). Uncertainty levels correspond to 2 standard deviations.

to optimize trend detection using intensive sampling approaches, (2) to develop easily deployable and cost-effective sampling approaches for a globally extensive ground-based network, and (3) to provide a means for validating satellite measurements in these complex and understudied environments.

  • Extend the international WMO Global Atmospheric Watch network of in situ sampling stations to fill in underrepresented regions globally, thereby improving national sampling of regional greenhouse gas emissions. Expanding the network to increase collection of vertical profiles of greenhouse gases would constrain atmospheric transport and facilitate interpretation of satellite data. The vertical expansion could be done with the cooperation of commercial aircraft and with balloons flown to higher altitudes. Ideally, all major emitting nations and groups of neighboring smaller nations would participate in the cooperative network. The latter may require financial assistance and capacity building to aid the poorest nations that dominate the most undersampled regions.

  • Extend the capability of the existing CO2 sampling network to measure atmospheric 14C. At least one additional U.S. accelerator mass spectrometry laboratory is needed to handle approximately 10,000 new atmospheric 14CO2 samples a year.

  • An interagency group, with broad participation from the research community, should design a research program to develop gridded high-resolution data on U.S. fossil-fuel emissions and HFC, CFC, and PFC emissions. An important component of these maps should be uncertainty estimates that can be used directly in data assimilation programs. To support the research, the National Science Foundation (NSF), NOAA, NASA, and the Department of Energy should expand campaigns to sample the time evolution of tracer fields at high resolution as well as studies that use the data to improve transport modeling of tracers. This research would feed into an international initiative to publish gridded estimates for fossil-fuel emissions, as recommended in Chapter 2.

  • Develop a state-of-the-art carbon data assimilation system that is coupled and/or synergistic with meteorological, land, and oceanographic data assimilation systems for the United States. This would require new approaches for coupling circulation and biogeochemical models and for deriving biogeochemical properties (and hence surface fluxes) from the obser-



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