The global market-based measure (GMBM) scheme the International Civil Aviation Organization (ICAO) will take up later this month is not aggressive enough to achieve emissions reduction goals, according to a coalition of environmental organizations. The group called for revisions to the scheme, among them requiring that major aviation countries “publicly commit” to participating.

At its 39^th triennial assembly, which will take place September 27 through October 7 in Montreal, ICAO’s 191 member states will vote on the GMBM scheme as part of a “basket of measures” the aviation sector will undertake to achieve “carbon-neutral growth,” or capping net carbon dioxide (CO2) emissions, by 2020. The ICAO executive committee released a draft of the carbon offsetting scheme in the form of a working paper earlier this month.

The International Coalition for Sustainable Aviation (ICSA) contends that the GMBM scheme as proposed does not adequately address the projected increase in air travel and is not strong enough to help achieve carbon-neutral growth. “Unfortunately, the text that we have now shows that aviation is well off course to meet this target and ICAO’s deadline to adopt this measure is rapidly approaching,” advised Kelsey Perlman, policy officer for land use and aviation with Brussels-based Carbon Market Watch.

During a webcast for invited reporters on September 15, ICSA member organizations summarized their concerns with the GMBM proposal, which is contained in ICAO Working Paper 52. According to Annie Petsonk of the Washington, D.C.-based Environmental Defense Fund, there is an “emissions gap” of about  three gigatons that the GMBM scheme would only partially cover to maintain carbon-neutral growth after 2020.

The forecasted growth in emissions by that time is six gigatons through 2035—more than one gigaton could be reduced by air traffic management efficiencies; another third of a gigaton through a new airplane CO2 standard developed by the ICAO Committee on Aviation Environmental Protection. Technological improvements such as lighter airframes, better performing engines and new certification standards—known as non-market-based measures—might make up another 1.5 gigatons, leaving a balance of three gigatons. The proposed GMBM scheme covers just two-thirds of the balance; the use of biofuels would be needed for the rest, Petsonk said.

As proposed, the carbon offsetting scheme would establish a voluntary “pilot phase” from 2021 through 2023 and a voluntary “first phase” from 2024 through 2026. A second phase from 2027 through 2035 would be founded on mandatory criteria. ICSA argues that major industrialized and aviation nations should publicly commit to join the first two voluntary phases. Further, an opt-out provision that allows states to withdraw from the early GMBM phases “sows uncertainty for airlines” and is inconsistent with emissions-reduction goals, the coalition argues. Nations and regions that want to exceed the scheme’s requirements should be encouraged to do so. And reductions achieved under the GMBM scheme should not be “double-counted” toward other goals.

The Paris Agreement negotiated by 197 countries last December did not cover international aviation emissions, but reducing those emissions will be key to achieving the Paris accord’s goal of limiting the increase in global average temperature to 1.5 degrees C above pre-industrial levels. (Domestic aviation emissions were calculated as part of national greenhouse gas emissions (GHG) under the accord.) Thus far, 27 of the 197 parties, representing nearly 40 percent of global GHG emissions, have ratified the agreement, which requires at least 55 countries representing 55 percent of total emissions to enter force.

International and domestic aviation combined produce 2 percent of global CO2 emissions, which would make the aviation sector the seventh largest emitter if it were a country, said Lou Lenard, senior vice president of climate and energy with the World Wildlife Fund, also based in Washington, D.C. With the expected growth in air travel, aviation will claim 27 percent of the 1.5 degree C “carbon budget” by 2050, he said.

“There is really is a gaping hole in our ability to achieve these global goals from the Paris agreement and that gaping hole is big enough to fly an airplane through—it really is international aviation,” said Lenard.