An Atmospheric Perspective on the Northern Hemisphere Carbon Uptake Period: Estimation, Sensitivity, and Temporal Change

This PhD research investigates when ecosystems begin and end absorbing more carbon dioxide than they release, and how these timings have changed over the past two decades. Using long-term atmospheric carbon dioxide measurements, atmospheric transport models, and estimates of carbon exchange between ecosystems and the atmosphere, the research develops methods to identify these changes more reliably. The findings show that carbon uptake is beginning earlier in many northern hemisphere regions, although the changes differ geographically. The research also highlights how atmospheric transport and mixing influence the carbon dioxide signals measured at observation stations, making it difficult to directly link atmospheric measurements to ecosystem changes. These findings contribute to a better understanding of how ecosystems respond to climate change and how reliably atmospheric observations can be used to track these responses.