How can we learn about the emissions contributing to climate change and air pollution by making measurements of the atmosphere? In this project, we will measure the emissions of methane and carbon monoxide from different sources using a powerful new measurement technique. Methane is the 2nd biggest cause of climate change. It is produced by many sources including landfills, livestock and natural gas leaks, but its emissions are not very well-known. Carbon monoxide contributes to air pollution and its sources include the burning of petrol in motor vehicles and the burning of wood for home heating.

To address the threats of climate change and air pollution, the UK government and other governments around the world are implementing policies to reduce emissions from human activities. For example, in the UK, methane emissions from landfills decreased over the past few decades because new technologies to capture methane gas from landfills have been introduced and improved over time. To calculate landfill emissions, the government takes accounts of each landfill's size and practices for managing methane emissions. Similar accounting calculations are performed for other types of emissions.

We will measure the amount of radiocarbon in atmospheric methane and carbon monoxide to check the accuracy of these emissions calculations. Radiocarbon is a type of carbon that decays over time, and it is commonly used for estimating the age of materials in archaeology. Because fossil fuels are so old, all of their radiocarbon has decayed away. Therefore, emissions from fossil fuels such as natural gas leaks or petrol combustion will decrease the ratio of radiocarbon to other types of carbon in methane or carbon monoxide. Methane from livestock or landfills, and carbon monoxide produced by biofuel burning, contain radiocarbon because radiocarbon is produced in the atmosphere.

We have developed a new system to make measurements of radiocarbon more efficiently than ever before. We will apply the new system at observation sites in London and in the Atlantic Ocean to measure radiocarbon in atmospheric methane and carbon monoxide. With these measurements, we will be able to tell how much of the methane and carbon monoxide emissions in London and southeast England are coming from fossil fuels or from other sources. This will allow us to evaluate the UK's reported emissions and understand better what changes need to be made to reduce overall emissions.

We will use the measurements in the Atlantic Ocean to study emissions from different sources across the entire globe, and how chemical reactions that destroy methane and carbon monoxide in the atmosphere vary over time. We will use computer simulations of the atmosphere that calculate how emissions move around and where and when the chemical reactions destroying methane and carbon monoxide are the strongest. By comparing our measurements to the computer simulations, we can determine where there may be errors in the reported emissions or in the chemical reactions included in the computer simulations.

This project will provide a unique evaluation of the fossil fuel contribution to methane and carbon monoxide emissions, both globally and in the UK. We will quantify how much the chemical reactions destroying methane and carbon monoxide change year-to-year, which is crucial for avoiding mistaking changes in these chemical reactions for changes in human emissions. With this unique new study on methane and carbon monoxide emissions, we will help to improve the effectiveness of policies being implemented to address climate change and air pollution.