Climate footprint from Swedish residents’ air travel

Greenhouse gas emissions from air travel are substantial for high-income countries like Sweden. The established accounting methodology for aviation, which is used for reporting to the UNFCCC, is based on how much fuel aircrafts take on in each country (termed bunker fuels). We have developed a supplementary indicator that includes emissions from the entire trip to the final destination as well as the non-CO2 effects from aviation. In this report we have analysed the trends between 1990 and 2017. The number of trips per person has increased dramatically. Domestic air travel has not increased but international trips have doubled from 0.5 trips per person and year in 1990 to 1.0 trips per person in 2017, an annual increase of 2.9 %. The average distance to the final destination has not increased much during the period since the number of both short and long trips have increased. The average distance is about 2700 km for a one-way trip, which is similar to the distance between Stockholm and Madrid. Emissions per passenger km have decreased by 1.9 % per year on average. In 2017, emissions from air travel were 90 grams CO2 per passenger km, and if the non-CO2 effects are included, these emissions are estimated at 170 grams CO2eq. Even if there is a great deal of uncertainty concerning non-CO2 effects, there is no doubt that such effects exist and that they are not insignificant. We assess that the most reasonable position to take is to be in line with the IPCC report (AR5) and include these effects. We use the most well-established scientific estimate which is, measured in GWP100, that the overall climate impact is approximately 1.9 times higher than the impact of CO2 emissions alone (including the effects of contrails and cirrus clouds for example). True emissions per passenger km obviously vary depending on the distance and aircraft type, etc., but using the same emissions factor for all travel gives a fairly good estimate for most flights. Although long distance trips typically have lower CO2 emissions per passenger km, a larger share of the trip is at a higher altitude and thus causes more non-CO2 emissions per passenger km. The opposite is true for short distance trips where CO2 emissions per passenger km are typically higher due to the energy-demanding ascent but where only a small, or non-existent, share of the flight is at altitudes where the non-CO2 emissions principally arise. As such, these two effects cancel each other out and the resulting CO2eq per passenger km are similar, regardless of the distance. The 170 grams CO2eq can be compared with the emissions from long-distance travel by car, which is about 50 grams per passenger km, based on the average number of persons (3) in each car on long-distance trips. The total emissions from air travel by Swedish citizens was 10 million tonnes CO2eq in 2017, an increase of 47 % since 1990. Emissions from domestic aviation are decreasing and now account for only 7 %, while emissions from international trips have increased and now account for 93 % of the air travel emissions. This increase in emissions occurred during the 1990s. After 2000, emissions have remained on the same level due to the emissions decrease per passenger km having been on par with the increase in passenger km. The greenhouse gas emissions from Swedish inhabitants’ air travel is now about equivalent to Sweden’s emissions from car use. Sweden’s annual emissions from air travel are now about 1.1 tonnes CO2eq per inhabitant, which is about five times higher than the global average.