A ground-based remote sensing measurement network designed to infer net emission of CO2 and methane from the City of Edinburgh

Reducing emissions of greenhouse gases (GHGs) from urban areas – currently accounting for 70% of the global budget – are an integral part of the solution to meet net zero targets (IPCC, 2022). As part of the GEMINI+Edinburgh project (GHG Emissions Monitoring network to Inform Net-zero Initiatives +Edinburgh, Kurganskiy et al., 2025) we have developed an observational framework to determine long-term trends in GHG emissions from the City of Edinburgh, Scotland.

To determine these emissions, we use column concentrations of CO₂ and methane retrieved from six EM27/SUN Fourier transform solar absorption spectrometers (“EM27”, Bruker GmbH, Germany) deployed in a ring around Edinburgh with 5 – 8 km separation. The spectrometers use the sun as their open-path source to measure solar radiation (4000 - 12000 cm cm^-1, 0.5 cm^-1 spectral resolution) from which we retrieve column abundances of CO₂, methane, CO, O₂ and H₂O. We apply an upwind-downwind mass balance approach to the data collected from these six spectrometers to estimate city-wide net emissions. Spatial variations in near-surface wind fields are captured by eight automatic weather stations (Vaisala WXT530) and sonic anemometers (Gill WindSonic 75) co-located with each EM27 and on additional tall buildings.

We have developed methods to ensure that GEMINI+Edinburgh delivers long-term (O10 year) and reliable measurements to enable reliable CO₂ and methane emission trends. As delivered, the EM27 is not weatherproof and not designed for long-term outdoor and unsupervised operation. To overcome these challenges, we have encased each instrument in a purpose-built weatherproof enclosure (Karn Scientific Ltd., Edinburgh). We demonstrate the enclosure performance by using co-located measurements from (un)enclosed EM27s during a series of intercomparisons and characterising the effect of the enclosure’s BK7 glass window. We employ a data processing workflow to enable long-term automated operation of the network, including an instrument meta data system, data transfer, processing, quick-look diagnostics plots, and archiving.

 

IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. doi: 10.1017/9781009157926

Kurganskiy, A., Feng, L., Humpage, N., Palmer, P. I., Woodwark, A. J. P., Doniki, S., Weidmann, D., 2025. The Greenhouse gas Emission Monitoring network to Inform Net-zero Initiatives UK (GEMINI-UK): network design, theoretical performance, and initial data. Submitted to Atmospheric Measurement Techniques.