What Is the true CO2 created by flying - welcome to radiative flying

Written by
February 22, 2024
5 min read

The aviation industry is a crucial part of our economy, we rely on planes for everything from imports and exports, to business travel and obviously tourism, and there are approximately 40m passenger flights a year. But the importance of this industry comes with negative effects which continue to affect our climate.

Emissions from flying are a significant contributor to global greenhouse gas and CO2 emissions. Around 2.4% of global CO2 emissions come from aviation, if you then take into account the other gasses released in flying and the water vapor trails produced by aircrafts the aviation industry can be held responsible for 5% of global warming.

Planes release vast quantities of CO2

When it comes down to calculating the CO2 of flying there are many different elements that are taken into consideration that affect how much C02 is released per flight and person; and subsequently how bad each flight is for the environment.

  1. You Thought Only Distance Mattered, Why Height is More Critical

The distance that the plan travels obviously makes a direct impact on how much CO2 is released per flight. But, a less known factor that has to be taken into account when flying is height, which much like distance has a direct warming impact on the planet.

This is due to something known as “Radiative Forcing”, which is what happens when the amount of energy that enters the earth's atmosphere is different from the amount that leaves it. If more radiation is entering the earth than is leaving it, which is what is taking place today due to the enhanced greenhouse gas effect, then the atmosphere will begin to warm up. This is known as radiative forcing because the differences in energy can force changes in the earth's climate.

When planes release contrails (water vapor that freezes around the black carbon particles in the exhaust that we see as white wisps in the sky) up in the sky it worsens the radiative forcing as these contrials trap heat, prevent it from leaving the atmosphere, and warm the air down below.

Marc Stettler a lecturer at Imperial College London found that changing planes altitudes to just 2000 feet higher or lower could reduce contrials warming effects by up to 59%. There are specific conditions that are needed to form contrials, there must be high humidity and low temperatures meaning that they do not form in all areas of the sky. Therefore, when calculating the warming effects and C02 of flights the altitude must be taken into account as if the flight path is through a contrail forming region the warming effects are more severe.

Plane contrails create Radiative Forcing

Domestic flights are those that take place within the UK and for an average passenger the total kg of CO2e per unit is 0.13 per KM per passenger. However, for a flight that flies at an altitude where contrails are created the total kg of CO2e per unit is nearly double at 0.2548/ KM per passenger.

So as an example

London to Edinburgh Return = 0.27 tonnes of CO2e with RF, and 0.14 without.  

For a short haul flight which is those flights within Europe for an average passenger the total kg of CO2e per km without radiative force is 0.08117 but with RF is 0.153.

London to Barcelona Return = 0.18 tonnes without RF, and 0.35 tonnes with RF

Long-haul flights are considered those outside of Europe and without RF for an average passenger it is 0.1028 kg of C02e per km and with RF is virtually doubled, to 0.19309

These numbers show how both the height and a distance of a flight make a big difference when calculating the CO2 of flying.

London to JFK = 1.65 tonnes with RF and 0.87 tonnes without as an “average passenger” (we’ll talk about Class of flight next).

To put that in perspective, if you wanted to plant trees to offset your flight you would need to plant 281 trees to remove the co2 in a year.

So as a word of caution, when you see people state that planting 3 trees would remove the co2 for a long-haul flight, you can,  but it would take 25 years)

If you wanted an immediate solution via a verified carbon credit, it would be around £20 for 1.65 tonnes, via a carbon project.

  1. The Class of the Flight

What this refers to is whether you fly economy, premium, business or first as it was recently discovered that this does in fact have an impact on flight emissions.

The ICCT compiled a report analyzing carbon emissions from aviation in 2013, 2018 and 2019 found that passengers seated in business class are responsible for 2.6 to 4.3 times more emissions than if they fly in economy. This is because seats in the economy section of the aircraft are closer together, offering passengers less room which reduces each economy passenger's personal CO2 as the flight's emissions are divided among all those people sat in economy.

In economy there are lots of people seated in one section of the plane.

Meanwhile in the higher classes they are typically paying to have much more room on their flight which means there are less seats in that section of the plane, the C02 load is divided between less people so the individual load is higher. Additionally, the services that come with these premium services such as kitchens, bars and private lavatories create a larger carbon footprint than those sat in economy.

First class passengers have more space and amenities.

For a first class passenger on a short haul flight, with radiative forcing, the kg of CO2e per unit is 0.227/ km, compared to the average passenger we saw earlier which was 0.153. For a long haul flight in first class with RF it is 0.592 kg of CO2e per km which is more than double an average passenger.

Height and distance and Class are the elements that go into the construction of calculating the CO2 flying and having a deeper understanding of this allows businesses and individuals to understand the impact of their travel and offset it accordingly.

But as a word of caution, don’t be fooled by the low numbers often quoted to make us feel better about flying. The solutions are simple, but they aren’t necessarily as cheap as we’re being led to believe.

A First Class London to New York Flight requires 6.58 tonnes to be accounted for. That’s 1,119 trees that would need to be planted or you can purchase verified carbon credits.

At SKOOT we’ve got the solutions, we all just need to help people understand that we also have a responsibility to be held accountable for our own emissions.

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Written by
February 22, 2024
5 min read