Challenge

CSIRO At mospheric Research, Aspendale. Victoria and Cooperath v Research, Centre tor Southern Hemisphere Meteorology, Clayton, Victoria. Australia

1. Introduction 245

2. Present Status of Global C-Models 245

3. Global CO;-Measurements 247

4. The global C02-Measuring Network 249

References 252

1. Introduction

The long lifetime and rapid mixing of C02 in the atmosphere provide a large-scale integration of surface fluxes, while, with sufficient measurement precision, signatures of individual surface source or sink regions can still be detected. The three-dimensional Bayesian synthesis inversion technique was introduced into global carbon cycle modeling by Enting et al (1993; 1995). Measurements of atmospheric C02 mixing ratios and stable carbon isotope ratios from globally distributed sampling sites for selected years were interpreted using an atmospheric transport model to determine regional sources and sinks of atmospheric carbon. The inversion process is inherently unstable, and requires additional constraints, in this case the spatial distribution of known sources and sinks, and prior estimates of the surface fluxes. When those prior estimates are independently and rigorously determined, the Bayesian technique provides a promising framework within which the various studies of regional carbon fluxes (and associated process information) can be reconciled with changes in the global atmospheric carbon content. A particular advantage is the potential for systematic treatment of uncertainty in the various components of the inversion. Application of the Bayesian technique to global carbon budgeting is still in the early stages of development.

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