Monitoring and modelling European carbon fluxes using atmospheric observations

Reducing carbon dioxide (CO2) emissions from human activities is becoming increasingly important to achieve the goals set in the Paris Agreement. To monitor progress towards our goals, it is important to quantify anthropogenic carbon emissions. This quantification heavily relies on measurements of CO2 in the atmosphere. Atmospheric CO2 is strongly influenced by the uptake (in summer) and release (in winter) of CO2 by plants. Therefore, the quantification of plant uptake is also of great importance for monitoring anthropogenic carbon emissions. In this thesis, which focusses on Europe, we develop and utilise new methods to make the quantification of CO2 exchange faster and more accurate. We analyse the added value of potential atmospheric CO2 measurement locations and develop a model that can estimate carbon exchange with the atmosphere by plants and human activities with minimal delay, allowing for quick analysis of the events that are important for the carbon cycle, such as socioeconomic changes or anomalous weather. With this model, we have analysed the impact of the 2022 European drought, demonstrating that plants in Europe absorbed significantly less CO2 due to the drought, accumulating to more than the entire annual emissions of the Netherlands. Finally, we develop a method to incorporate measurements of tree growth, along with measurements of CO2 in the air, into our estimates of plant CO2 exchange. With this thesis, we contribute to better monitoring capacity of CO2 emissions and uptake across Europe.