Hot Air is the term commonly given to the part of an Annex I Party's Assigned Amount of emissions that is most likely to be surplus to its needs even without that Party making additional efforts, beyond existing policies in 1990, to reduce its emissions. This surplus is likely to be made available to other Annex I countries through Emissions Trading or JI. Russia and Ukraine are widely seen as having the most 'hot air' to sell.

Source: Europa