This year felt a little odd (said everyone, everywhere).
I usually fly a lot for work. 2 or 3 times a month. So far this year, no business flights.
I’m torn on this fact. On one hand, I believe such face-to-face interaction with teams is vital (at least to me), on the other I realise I am part of the environmental problem.
As a human, I try and wrestle with my moral conscious. “I’m not as bad a Sarah”, “I don’t take flights for the sake of points“, I tell myself in a weak attempt to justify my flights.
It got me thinking, how do I compare to the average person?
Global Environmental Change (Volume 65, November 2020, 102194) recently released a study titled; The global scale, distribution and growth of aviation: Implications for climate change.
This report used industry statistics, data provided by supranational organisations, and national surveys to develop a pre-COVID understanding of air transport demand at global, regional, national and individual scales.
Whilst I stress these are pre-pandemic estimates (although many suggest air travel will soon bounce back to normal levels).
Some of the processed data detailed in the report is used in this post alongside directly cited data.
% of population that travel
According to IATA (2019), there were 4.378 billion passengers in 2018 (international and domestic). This is not equivalent to trip numbers or individual travellers. Most air trips are symmetrical, i.e. they will involve a departure as well as a return.
As ten percent of all flights involve a transfer, 4.378 billion passengers would thus represent a maximum of 1.99 billion trips.
The share of the global population participating in international air travel is even smaller, as a significant share of all air travel takes place within countries. Domestic air travel included 2.566 billion passengers in 2018, out of this 590 million in the USA, 515 million in China, and 116 million in India (IATA, 2019).
International air travel consequently only comprised 1.811 billion passengers, who are also more likely to move through hubs. On the basis of the conservative assumption that one international trip comprises 2.2 flights (IATA, 2019), some 823 million international trips were made in 2018.
Non flying population
This does not consider that there is a significant share of the population in every country that does not fly, while some air travellers participate in one, two, or multiple trips.
||% non-flying pop est. (2018-2019)
For example, data for the USA suggests that 53% of the adult population do not fly (Airlines for America, 2018). In Germany, 65% of the population do not fly (IFD Allensbach, 2019), while this share is 66% in Taiwan (Tourism Bureau Taiwan, 2019). In the UK, the non-flying share of the population 16 years or older is 59% (DEFRA, 2009).
These national surveys indicate that in high income countries, between 53% and 65% of the population will not fly in a given year. The share of non-fliers is likely larger in low-income, lower-middle and upper-middle income countries. The share of non-fliers is likely larger in low-income, lower-middle and upper-middle income countries.
International multi-trip flyers
An alternative way of calculating the share of the population participating in international air travel is to divide the number of international trips by an average trip number per traveler.
For example, Airlines for America (2018) suggest that the average air traveler makes 5.3 trips per year, with a relatively large share of travellers participating in only one or two trips, and a rather small share accounting for large trip numbers.
Applying the US average of 5.3 trips as an indication of skewed demand, 823 million international trips involved only 155 million unique air travellers, or 2% of the world population (world population of 7.594 billion).
Similarly, for domestic trips, applying this logic, 5.3 trips for the average traveller with 2.566 billion domestic passengers in 2018, means about 6% of the world’s population (456 million) travelled domestically.
Global distribution of aviation fuel use (2019)
||% share of aviation fuel use
|Commercial aviation: Passengers
|Commercial aviation: Freight
There’s some guesswork here, as there is no global data for military operations or private flights.
It has been suggested that military aircraft consumed 22% of US jet fuel in 2008 (Spicer et al., 2009), though a lower recent estimate for the US in absolute numbers is 18.35 Mt CO2 (in 2017; Belcher et al., 2020). In a global estimate for 2002, Eyers et al. (2004) concluded that global military operations required 19.5 Mt of fuel, leading to emissions of 61 Mt CO2, or 11.1% of global emissions from aviation.
For an estimate, the current contribution of military flight to global emissions from aviation is assumed to be 8%. This estimate is uncertain, but highlights the importance of military flight in aviation emissions.
Data on private aviation is equally limited. The global business aviation market is estimated to have included 22,295 jets, 14,241 turboprops, and 19,291 turbine helicopters in 2016 (AMSTAT Market Analysis, 2018). Assuming an average of 400 h of flight time per year for the global fleet of private jets, with an estimate of a 1200 kg/hour fuel use (Gössling, 2019), jet fuel burn was 10.7 Mt in 2016, corresponding to 33.7 Mt of CO2.
Adding the fuel use of turboprops and helicopters, overall emissions from private transport may be in the order of 40 Mt CO2. This would suggest that private aviation accounts for about 4% of global emissions from aviation
At first glance the military and private aviation fuel use might seem low, but considering it on a per passenger basis, this share of fuel is actually comparatively high.
Fuel use Mt CO2 by aviation travel type (2017)
Estimates of global fuel use vary. More recent estimates presented by IATA (2018) suggest that civil aviation – including international and domestic, passengers and freight – emitted 859 Mt CO2 in 2017.
Assuming this is 88% of total consumption (71% passengers + 17% freight), then global fuel consumption in 2017 was 976 Mt CO2.
Therefore, commercial aviation (passengers) contributed 693 Mt CO2 in 2017.
The International Energy Agency (IEA, 2019a) specifies that about 60.4% of this for international aviation (416 Mt CO2), and 39.6% for domestic aviation (277 Mt CO2).
Over the past 20 years, global carbon dioxide (CO2) emissions from fossil fuels and industry have been steadily increasing, and by 2018 reached a record high of 36.6 billion metric tons (Statista).
Looking at all emissions, commercial aviation (passengers) contributed 0.693 Bt CO2 emissions in 2017, which is 1.9% of all global emissions (0.693/36.6).
Thus, 2% of all CO2 emissions (0.693 Bt CO2) are caused by an estimated 6%-8% of the worlds population (from air travel).
In many cases the data in the post considers data reported over different time periods, or uses aggregated data. Being able to access like-for-like raw data would improve accuracy.
823 million international trips involved only 155 million unique air travellers, or 2% of the world population
2.566 billion domestic trips involved only 456 million unique air travellers, or 6% of the world population.
Together, these passengers created 2% of all CO2 emissions.
- Data sources + data used in this post.