This paper studies the feasibility of CORSIA’s carbon neutral growth goal based on verified carbon offsetting. It is motivated by an ongoing general debate about the climate and regulatory integrity of carbon offsetting, thus systematically identifying critical carbon offset characteristics. Using registry data from the largest carbon offset verifiers eligible under CORSIA, we show that the majority of carbon offsets have minor climate integrity. This challenges CORSIA’s neutral growth objective. However, unconditional offset price differentials are only weak signals for climate integrity. To increase environmental effectiveness, a narrower scope of eligibility rules is necessary in order to ensure maximum compliance of projects and strengthen the necessary price effect of carbon offsets. However, it is highly questionable whether there is enough potential supply of offsets to ensure such high integrity, indicating that carbon offsetting should be considered as a transitory measure only.

This paper studies the performance of machine learning predictions for the counterfactual analysis of air transport. It is motivated by the dynamic and universally regulated international air transport market, where ex post policy evaluations usually lack counterfactual control scenarios. As an empirical example, this paper studies the impact of the COVID-19 pandemic on airfares in 2020 as the difference between predicted and actual airfares. Airfares are important from a policy makers’ perspective, as air transport is crucial for mobility. From a methodological point of view, airfares are also of particular interest given their dynamic character, which makes them challenging for prediction. This paper adopts a novel multi-step prediction technique with walk-forward validation to increase the transparency of the model’s predictive quality. For the analysis, the universe of worldwide airline bookings is combined with detailed airline information. The results show that machine learning with walk-forward validation is powerful for the counterfactual analysis of airfares.

Zusammenfassung: Der Luftverkehr ist durch die Maßnahmen gegen die COVID-19-Pandemie besonders stark betroffen. Der Verkehrsrückgang betrug 2020 zum Teil mehr als 90 %. Da die Branche von großer Bedeutung ist, sind besondere staatliche Unterstützungsmaßnahmen sinnvoll, wenn die Pandemie vorbei ist und neues Wachstum einsetzt. Dabei sollten jedoch nicht nur bestimmte Unternehmen unterstützt werden, sondern die Hilfsmaßnahmen sollten auch an bestimmte Kriterien gebunden sein.