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Measuring London’s Greenhouse Gas Emissions

Daniel Hoare, PGI student, University of Bristol and NPL

Climate change is a big problem, one that is impossible to solve alone. Here’s my view on working to measure London’s greenhouse gas emissions as part of a multi-institute team. 

I’m a PhD student based at the University of Bristol with a CASE studentship from NPL working on the London GreenHouse Gas (LGHG) project. We’re working to measure London’s methane and carbon dioxide emissions, ultimately to be used by London’s climate policy team to make effective progress towards their net-zero goals. We achieve this by combining high-quality atmospheric measurements and start-of-the-art computer modelling. 

This type of problem is complex and requires many experts to work together. As well as my colleagues from the University of Bristol and NPL, I also work along researchers from the Met Office, Cranfield University, the University of Cambridge and Cambridge Environmental Research Consultants.  

Every person provides their own expertise to ensure the project succeeds. First, a network of instruments needs to be set-up and deployed across London to measure local concentrations of methane and carbon dioxide. Next, two different atmospheric models are used to calculate the path the air took before it reached the instruments. Finally, we combine these as inputs in Bayesian models that allow us to estimate emissions across London.  

My own role in this project is being a modeller: designing and running the computational models that describe the air flow in London and allow us to link the measurements we make to emission sources in the city. This requires collecting and processing all the data from my colleagues, and comparing and analysing results with the other modellers in the team.  

As we are approaching the end of the first year of measurements being collected, I am busy finalizing the fine details of my models. The aim is to make the best use of the data available, to get the most accurate emission estimates possible. We also analyse where the uncertainty in our results comes from so that we can make improved estimates in the future.  

Once these estimates are ready, they can be compared to the inventory estimates used in the official annual emission reports to ensure they are as reliable and accurate as possible. This process is considered good practice in the international guidelines and is already used at the national scale with the UK DECC (Deriving Emissions linked to Climate Change) network. The LGHG network will allow us to expand this technique to look at high-resolution, local emissions.  

With long-term funding the network would be able to watch how London’s emissions change over the years, providing vital information to the London government on the effectiveness of their climate policies.  

This technology is currently being showcased in Glasgow for COP26, and a public interface for the data is available at, along with further information on the science. 

If you would like to see more about the role of metrology in supporting climate action decision making, further information is available at the Measurement for our planet website here. Through this programme, NPL is showcasing how metrology is improving confidence in the data upon which policy makers and industry leaders alike will depend, as they develop, implement and monitor climate action strategies. 

22 Oct 2021