A lack of information about temporal changes in measurement uncertainties is an area of concern for long-term trend studies of the key compounds which have a direct or indirect impact on climate change. The IAGOS program has measured O₃ and CO within the troposphere and lower stratosphere for more than 25 years. In this study, we demonstrated that the IAGOS database can be treated as one continuous program and is therefore appropriate for studies of long-term trends.