The North American Carbon Program Plan (NACP)
A Report of the Committee of the
U.S. Carbon Cycle Science Steering Group

Appendix 4b

 Emissions Inventories in the NACP

A program to define the natural components of the cycle will require careful characterization of the human components. Doing so depends on (1) analysis of the spatial and temporal distributions of emissions and (2) understanding how efforts to control carbon flows in one area or for one set of processes will impact the full system. The detailed analyses in the NACP, both forward and inverse approaches, will require refined inventories of anthropogenic emissions of CO2, CH4, and CO, with detailed spatial and temporal distributions of emissions characterized by fuel in order to allow estimation of carbon isotope signatures. We also need a better description of the uncertainties in these values.

We envision that the requisite analyses of emissions would be carried out using a multi-phase strategy. The first phase would involve emissions inventories on the approximate scale of months and U.S. counties. The spatial and temporal distribution of sources is highly variable and later phases will better describe the variability with time of day, day of the week, and weather, for example. We would be interested to know the extent to which these variations can be described with simple algorithms. What are the linkages between human emissions and the climate system?

Validation of emissions estimates will be part of the intensive measurement phase, using the comprehensive suite of gaseous and particulate tracer species available for INTEX and other atmospheric chemistry missions. Emissions from large point sources can be highly variable on small temporal and spatial scales as power plants are taken down for maintenance and adjusted to meet load demand. In the context of specific focused campaigns to understand the functioning of the North American carbon cycle, it is possible to think in terms of human emissions, especially those from large point sources, as a variable that might be manipulated.

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