Shifting concerns for the EU ETS: are carbon prices becoming too high?

Carbon prices in the EU Emissions Trading Scheme (EU ETS) have risen from around 5 euro per ton of CO2 in 2017 to above 90 euro in 2021. One probable explanation is the cancellation mechanism implemented along with the Market Stability Reserve (MSR) of the EU ETS in 2018. We identify realistic conditions under which the MSR results in truly massive cancellation of emissions allowances, pointing to the steepness of the emissions pathway over time as essential. A flattening of the emissions pathway implies huge reduction in cumulative emissions, suggesting much higher ETS prices. The concerns about too low and 'ineffective' carbon prices may turn into concerns for too high prices. The results have important ramifications for planned revisions of the EU ETS.