- The document compares carbon dioxide (CO2) exchange between an urban site in Arnhem, Netherlands and a nearby forest site (Loobos) over daily to annual timescales. - It finds that the amount of carbon absorbed by the Loobos forest in 20 years of measurements is equal to the amount emitted by the center of Arnhem in just one year. - CO2 emissions in Arnhem are explained by traffic intensity and heating degree days, while CO2 uptake at Loobos correlates with incoming solar radiation. Understanding the differences can help analyze and verify city and forest carbon emissions and fluxes.