The Use of Inverse Modeling Techniques for Studying Global CH4; Current Status, Limitations, and New Developments

Abstract:

Inverse modelling techniques have been developed over the past decades for studying the global sources and sinks of CH₄, with the primary purpose to use the available atmospheric measurements to obtain improved flux estimates. During this period the global CH₄ growth rate showed large and unexpected variations, providing an excellent test case for the inverse modelling approach. Although estimates from single inversions are difficult to test, for lack of truly independent flux estimates on the scales addressed by the inversion, results of inversion inter-comparisons have made us aware of the size of the challenge. It is difficult to obtain robust estimates beyond the scale of broad latitudinal bands, because of uncertainties in atmospheric transport and limitations in the availability of measurements. Several efforts have been made in the past years to meet the challenge, including the use of different kinds of measurements (tall tower networks, satellites), and modelling approaches (inversion techniques and the use of process models). The aim of this presentation is to provide an overview of those activities, including new directions (new instrumentation, and ways of combining different kinds of data) and the propects they offer for the near future.