Global warming is one of the greatest risks to society worldwide. To prevent stark changes to the Earth’s climate, emissions of the major contributing greenhouse gases, such as carbon dioxide and methane, must be reduced. Levels of carbon dioxide and methane in the atmosphere are at the highest they have been in the past 3 million years and this is mainly attributable to human (anthropogenic) activities. It is necessary to discriminate these anthropogenic sources from natural contributions and discern emissions from different industrial sectors, which can be done by underpinning measurements of stable isotopes of carbon dioxide and methane. This project will fill the existing traceability gap in the measurement of the isotopic composition of carbon dioxide and methane by providing a new infrastructure for delivering gaseous carbon dioxide and methane reference materials and methods. This work is essential to provide governments with the data required to support inventory verification targets and enable pledges of emissions reductions to be demonstrated.