How (& Why) defining a Carbon Budget for the commercial aviation?

Carbon budgets being centric to drive sustainable businesses (see previous post ), let’s try to define what would be a carbon budget for the commercial aviation in line with the COPs objectives (limit temperature rise to +2°C max in 2100 with 66% chance of success)

Assuming the Earth carbon sinks keep its current absorption performance, the world wide CO2 emissions shall not exceed 1170 Gt from 2018 to get a 66% chance to limit the temperature rise to 2°C by 2100 (note 1). It is 844 Gt for the “2050 intermediate” milestone (still starting from 2018)

Setting reduction objectives but what for ?

The ICAO holds the ambition to cut the overall carbon emissions of the commercial aviation by 50% in 2050 compared to 2005 levels (Note 2). While this is an agressive objective, it does not correlate with the overall IPCC target to limit the average temperature rise by 2°C in 2100. On top of this, each nation is excluding the carbon emissions of the international transportations from its respective count and budget.

Therefore, the commercial aviation is left into a grey zone where no one is owning the responsibility of its global emissions and where their reduction target is not linked to the overall objective. One must admit this is not the best start to win the race..

In a recent study, The Shift Project ( took an interesting approach. The Think Tank worked on proposing a carbon budget baseline for the commercial aviation which is aligning with the IPCC objectives. Doing so makes easier to define what the sector can afford and what are the viable options to stay within budget.

Defining a Carbon budget for commercial flights.

The commercial flights were responsible for 2,56% of the world wide Green House Gas emissions in 2018 (see previous post). Considering a faire rule saying that the efforts to be accomplished by the aviation shall be the same of all the others sectors, its budget shall be equal to 2,56% of 1170 Gt CO2. This gives a Not To Exceed amount of 30 Gt CO2 between 2018 and 2100. At current pace (about 1 Gt CO2 per year in pre-covid year of 2019), that budget would be consumed by 2050.

If we translate this 30 Gt budget into a year over year reduction over those 82 years, that means systematically reducing the aviation emission by 3,39% each year. By 2050, the yearly emission of the sector shall not exceed 357 Mt CO2, which represents 33 % of 2018 levels.

Note 3

This is is a huge challenge considering an average traffic growth estimate of 4% per year during same period (note 4).

Innovation will help achieving fuel efficiency gains but not to the needed extent. A combination of holistic measures will have to be deployed together to ensure flying remain possible in our constrained world. Let review the Shift Project study summary (note 3) to apprehend the nature and decarbonation potential of those measures.

Further posts will decrypt those and focus on the associated technical and financial challenges.

More to come…


Note 1: Source Intergovernmental Panel on Climate Change (

Note 2: Source ICAO 2019 Environmental Report

Note 3: Source: The Shit Project “”

Note 4: IATA traffic projection 2019-2039 0f547449c1093239597cc18/pax-forecast-infographic-2020-final.pdf


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