International Aviation Carbon Limits Finally Coming

After decades of inaction, the international community has put in place carbon pollution constraints for international aviation. The U.N. body that oversees international aviation—the International Civil Aviation Organization (ICAO)—has just adopted a resolution that will require the international aviation sector to offset its emissions growth after 2020. This is an important first step to finally control aviation’s growing carbon pollution.

I started my international climate career 16 years ago trying to get airlines, countries, and ICAO to adopt a “market-based measure” to control aviation’s growing carbon pollution. Unfortunately those efforts ran into too many headwinds at the time. But thanks to the perseverance of many, the world finally has some limits on aviation’s climate pollution. This agreement is a good start to address this sector’s pollution. More will be needed in the coming years to ensure that this sector’s emissions are on the necessary downward trajectory to help ensure that the world achieves the climate goals set out in the Paris Agreement.

The aviation sector is one of the world’s ten largest emitters of greenhouse gas emissions if it were a country. These emissions are projected to increase 3-4 times between 2010 and 2040 if more action isn’t taken (see figure). Unfortunately the Paris Agreement didn’t address international aviation emissions so this new ICAO agreement puts these unregulated emissions under some limitations.

Here are the details of what was agreed:

First phases are voluntary but many countries have already signaled they will opt-in. From 2021-2023, countries would opt-in to the program and offset their emissions growth above their 2020 levels. There would be a second phase from 2024-2026 where countries can also op-in. To date, more than 60 countries have indicated that they will join the program from the outset. This includes many of the countries that have the largest amount of international air travel such as the U.S., Canada, China, Mexico, the European Union, South Korea, Singapore, United Arab Emirates, Japan, and Qatar. According to estimates from EDF about two-thirds of the world’s forecasted cumulative emissions above 2020 levels would be covered by the countries that have signaled they will opt-in during the first phase. Let’s hope that other countries signify that they will join from the outset as airlines outside the system will have trouble arguing for unfettered access to major airports. After all, which country would want to let an unregulated airline use their airport?

System would become mandatory in later phases. From 2027-2035, countries would be required to participate if they have a large share of overall airline traffic (under a set of clearly defined criteria). Least developed countries, land-locked developing countries, and small island developing countries would all be exempt throughout the period. And any country not covered in this mandatory phase could opt-in. All major players will hopefully choose to opt-in to this phase as well. According to estimates from EDF over three-quarters of the world’s forecasted cumulative emissions above 2020 levels would be covered during this later phase based upon the countries that have signaled they will join.

Program can (and should) get tighter over time. Countries agreed to review the program in three years. Given the nature of the climate challenge, I hope that countries use that review as an opportunity to strengthen the targets over time to ensure that aviation’s carbon pollution is on a downward trajectory. This current agreement should be the floor, not the ceiling for the kinds of carbon pollution cuts that the aviation sector makes over the coming years.

Important technical details have to be worked out but the framework is in place to adopt robust rules. There are a couple of important technical details that have to be worked out including what kinds of “offsets” will count. There are provisions in the final agreement that will hopefully guide countries to adopt standards with the necessary rigor to ensure that these emissions offsets are real, measurable, and verifiable. The agreement also included provisions that will make it difficult for countries to count emissions reductions twice—“double-counting”—by counting them towards their Paris targets and also towards their international aviation targets.


This agreement is a good first step to finally control aviation’s growing carbon pollution. It took way too long to get to this point and more will need to be done in the coming years to further control aviation’s carbon pollution, but this agreement puts the aviation sector on notice that it must control its unfettered pollution. 

About the Authors

Jake Schmidt

Managing Director, International program

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