Nuclear observations to improve Climate research and GHG emission estimates (NuClim)

On a light blue background, the eastern part of the North Atlantic is shown: the Azores in the lower quarter on the left and Ireland, Great Britain and Spain/Portugal filling the right third. The landmasses are in a darker blue. On top of the map, blue arrows show a flow field. The main direction is from south west to north east. Between the Azores and the Iberian Peninsula the arrows indicate a swirl so that off the coast of Portugal the direction is towards South. In the foreground a light grey cloud is located in the left half at about the first third of the figure. It has a roughly the size of a quarter of the figure It contains the text "measurements of air masses without human influence" in light blue. Dark blue symbols are arranged around the text within the cloud: barometric pressure, methane, γ, wind, carbon dioxide, particles, carbon monoxide, eddies/swirls, ozone, rain, radon, temperature. The cloud is connected to one of the Azores islands - Graciosa Island - and to the west coast of Ireland - Mace Head - by white-blueish shapes that seem to tunnel towards the locations. In the top left corner the NuClim logo (a light blue wave dampened from left to right with NuClim written on the right part), and, in greys, a hand holding the Earth and one holding a radiation sign are placed. In the right lower corner the credits are given in small, middle-blue font: "Wind data from E.U. Copernicus Marine Service Information (DOI: 10.48670/moi-00181), map data from Natural Earth".

Greenhouse gas concentrations change due to two groups of causes: natural variations and deviations caused by humans. While understanding these two is important for modelling climate change, we currently don't know enough about either of them. This is why the NuClim project aims to measure the natural variations and fill this gap.

The climate change we are experiencing is caused by human activities that are increasing the amount of greenhouse gases in the atmosphere. However, the activities and emissions are neither spatially nor temporally uniform. To really understand the influence of humans, this is crucial information. At the same time greenhouse gases in the atmosphere also vary naturally. Understanding the human effects without understanding the natural variations is impossible. Therefore, determining the baseline for Europe and its natural variations on top of which the human effects work is the aim of this project.

The figure shows a plot with the title "Understanding natural variations helps us identify human impact". It is a stacked area chart where an unspecified value over time. The lower is the natural component and the upper the component caused by humans. The natural component is larger than the component caused by humans for most of the time, however, it creates an irregular baseline on to which the time-varying human caused component is added.

To measure air before it encounters human activities, measurements in NuClim are taken in two remote places: the Azores island Graciosa and Mace Head in western Ireland. Westerly winds from the Atlantic pass these before arriving at the European mainland. At these two stations greenhouse gases and radon are measured. Radon is a radioactive noble gas. It occurs naturally in the environment. As its main sources are on land and it decays within weeks (half-life of about 3.8 days), it tells us whether the air has been in contact with land recently. In this study, it serves as an indicator that the air mass has not encountered land in preceding days and with that has had as little human influence as we can hope for.

Measurements of the ambient gamma dose rate will also shed light on how it changes with different conditions. As it is an important parameter for nuclear surveillance networks and radiological protection, knowing the natural variations for this can be used similarly to the greenhouse gases: differentiating between natural and human-caused changes. In addition, meteorological measurements will indicate how variations correlate with atmospheric conditions, biological surveys will give insight into feedback with plankton and studies of the boundary layer between ocean and atmosphere will investigate how those affect greenhouse gases.