The International Civil Aviation Organization (ICAO) finalized an agreement to cap the aviation industry’s CO2 emissions at 2020 levels. Due to the cross-border nature of aviation, this sector, which is responsible for 2 percent of all GHG emissions globally, was excluded from the Paris Agreement in 2015. Although the agreement’s mandatory phase begins in 2027, more than 60 countries will voluntarily participate in the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) beginning in 2021.

CORSIA is a market-based measure capping emissions at 2020 levels. Airlines that exceed the emissions cap can offset their excess CO2 in two ways. Airlines can purchase carbon credits available via allowances, or alternatively acquire and redeem emissions units available through existing UN programmes like the Clean Development Mechanism or REDD. As a result of the measure, an estimated 80 percent of CO2 emissions above 2020 levels will be offset from the international aviation industry. ICAO estimates that airlines will spend 1.4 percent of their international revenues on the CORSIA scheme by 2035.

Despite these estimates, many environmental advocates question the efficacy of the agreement to create net emissions reductions, arguing that carbon offsets alone are insufficient to address the core of aviation emissions. Some argue that the agreement does little to promote decarbonization of the industry over the long-term, as offsets do not encourage development of cleaner airplane technology. In a statement from Transportation & Environment, the group said the agreement falls well short of carbon-neutral growth in 2020 as promised and the lack of clear rules for offsets presents a significant risk to the agreement’s environmental effectiveness. A group of 80 organizations, including Greenpeace and Friends of the Earth International, also expressed concerns about the agreement in a publication, indicating that “Offsetting is widely considered a false solution to climate change because it does not reduce emissions, but merely shift emissions from one sector to another.”