GEMINI-UK is a network of ground-based instruments located around the UK that measure carbon dioxide and methane in the atmosphere. They work by observing direct sunlight which the instrument splits into its constituent wavelengths, allowing us to see how much sunlight is absorbed at certain wavelengths by the gases we're interested in – the more of that gas present in the air above the instrument, the more light is absorbed at these wavelengths. The network was set up as part of a wider programme called GEMMA (Greenhouse gas Emissions Measurement Modelling Advancement), which aims to improve estimates of the UK's greenhouse gas emissions using new atmospheric measurements.

We have chosen the GEMINI-UK locations – UK universities, a research institute, and a high school – to give us the biggest uncertainty reduction in our estimates of the UK's carbon dioxide emissions, and use automated weatherproof enclosures that we designed at the University of Edinburgh to allow us to make measurements all year round (as long as we have direct line of sight to the Sun). In this presentation, we describe the measurements we have so far and show how much we think they improve our understanding of the UK's carbon footprint.