Stationarity properties of per capita CO₂ emissions in the OECD in the very long-run: a replication and extension analysis

We replicate, and extend, Zerbo and Darné's (2019) study examining the stationarity properties of per capita carbon dioxide (CO₂) emissions in the OECD from 1960 to 2014. We first replicate by reproduction their main findings for 25 OECD countries by applying their methods over the same time period that they consider. We then extend the analysis to examine whether CO₂ emissions are stationary in those 25 OECD countries from 1860 to 2014. We confirm Zerbo and Darné's (2019) main conclusion that historical events have induced changes in the trend function of the series and that emission levels are characterized by a non-stationary process. Using a longer timeframe also provides additional insights. Results from unit root testing suggest that not only more recent events, such as the first oil price shock, as highlighted by Zerbo and Darné (2019), but the Long Depression of the nineteenth century, the Great Depression and the two world wars have induced changes in the slope of the series.