We estimate that at peak times, 1.3 million b/d of global jet fuel demand was lost in recent days (see chart). Most of the lost flights – 85% based on rough assessments – will not be delayed but simply cancelled. Assuming that the situation is now resolved quickly, some 18,000 b/d of annual demand growth would be permanently lost, bringing this year’s global growth figures from 1.5% to 1.2%. However, part of this demand would simply be shifted to other transportation modes, with many adventurous stories cruising around how Europeans managed to get home on the weekend in 24h+ odysseys, making use of ferries, trains, buses, rented cars and taxis.
But will this substitution wipe out any CO2 savings? Perhaps not:
However, as the first three listed modes are roughly 3 times less fuel-consuming than planes, and in most cases only the load factor has increased, the lost consumption will not be fully recovered. (So excluding Eyjafjallajokull, there is a positive impact on the CO2 balance:-))
Whether that makes the volcano a net reducer of CO2 emissions is another question.
Volcanic ash could create yet more refining gloom - FT Energy Source