Inferring London’s Methane Emissions from a New Urban Measurement Network

Abstract:

Major cities such as London are increasingly taking the lead in efforts to reduce greenhouse gas emissions. To ensure that emission reduction policies are successful, policy makers require accurate knowledge of how emissions change over time. The London GHG project aims to provide "top-down" emission estimates for London, adding a London measurement network to expand upon the UK’s existing national measurement infrastructure. Whilst still not widely used, it is considered good practice to use top-down methods, which are based on atmospheric observations and make use of inverse modelling of atmospheric dispersion, to evaluate existing bottom-up emission inventories reported using socioeconomic data.

A series of in-situ atmospheric concentration instruments are being installed across the Greater London area and will be used to estimate London’s emissions of methane initially, with carbon dioxide emissions to follow. A medium-density urban network provides challenges in instrument calibration and siting, as well as in the development of new modelling approaches to capture the urban environment and link the measurements to policy-relevant emissions estimates. There are also opportunities to link with remote observations of London, including satellite and ground-based FTIR instruments. We present considerations of setting up the new network, and results from the initial instrument installation and model development.