COP26: Verifying Glasgow`s CO2 emissions using ADMS-Urban and measurements
Verification of carbon dioxide emissions is essential to achieving Net Zero and 'keeping 1.5 alive'. Researchers from CERC, Cambridge University, and ACOEM have collaborated on a project to verify CO2 emissions across greater Glasgow by combining measurements and CERC's ADMS-Urban air pollution dispersion model. The ongoing study, using available traffic data and emissions factors, suggests that CO2 emissions from road traffic around the region could be underestimated by up to 20%. These methods could be applied to verify the effectiveness of Net Zero policies for other cities.
From June 2021, fifteen AQMesh pods taking measurements of CO2 and other pollutants at 1-minute resolution have been co-located with Scottish Air Quality Network reference monitors at sites in Glasgow City, West Dunbartonshire, Renfrewshire and South Lanarkshire. From September 2021, two LI-COR reference-grade instruments have also been measuring CO2 at 1-minute resolution at two sites. ADMS-Urban has been applied to calculate hourly CO2 concentrations at the measurement sites for the period of the measurements using NAEI gridded emissions and DfT traffic flows, and allowing for the effects of street canyons. Road emissions within 2km of each monitoring site have been modelled explicitly as road sources; other road emissions have been modelled as 1kmx1km gridded emissions. Hourly background CO2 has been calculated from hourly baselines of the 1-minute AQMesh measurements calculated by the University of Cambridge team.
CERC researchers have applied Bayesian based inversion techniques to combine hourly modelled CO2 concentrations from ADMS-Urban with hourly averaged AQMesh and LI-COR CO2 measurements (top figure). The technique allows for the differences in uncertainties between low-cost sensors and reference monitors, for the uncertainties of the emissions from each source and for correlations between source emissions. The differences between the original and inversion-verified emissions (bottom figure) provide an indication of the accuracy of the original emissions inventory.
The project is funded by NERC and the Scottish Government.