A new tool developed by researchers at the University of Surrey reveals that common carbon footprint calculators for flights significantly underestimate their climate impact. The Air Travel Passenger Dynamic Emissions Calculator, or ATP-DEC, indicates emissions can be several times higher than figures from tools like those from ICAO, IATA, Google and MyClimate. This finding highlights gaps in how aviation's environmental effects are measured.
Researchers led by Jhuma Sadhukhan at the University of Surrey in the UK have created ATP-DEC, which they say provides a more accurate assessment of flight emissions. In a study published in Communications Earth & Environment, the team compared their calculator to four established ones. For example, a first-class flight from Singapore to Zurich on a Boeing 777 aircraft yields about 3,000 kilograms of CO2 equivalent according to ICAO and IATA calculators, 5,000 kg via Google's Travel Impact Model, and 8,000 kg from MyClimate. However, ATP-DEC estimates over 14,000 kg.
"The numbers are shocking," Sadhukhan said. Her colleague Eduard Goean, also from the University of Surrey and Therme Group in Austria, added, "The impact is considerably higher."
ATP-DEC differs by using historical flight data to model realistic routes, durations, taxiing times and passenger loads, rather than ideal paths. It updates dynamically, incorporating changes like longer routes due to Russia's war on Ukraine, which older calculators overlook. Crucially, it factors in non-CO2 effects such as contrails, nitrogen oxides and water vapour, which can amplify warming beyond CO2 alone. "Contrails, for instance, can have a greater warming effect than the CO₂ emissions from an aircraft," the researchers noted.
Unlike others that apply fixed averages, ATP-DEC varies calculations based on aircraft type, fuel and weather conditions. "They don’t vary with the aircraft, or the fuel conditions, or the external conditions," Sadhukhan explained. "Ours is more comprehensive."
The team plans to release ATP-DEC publicly and launch an app early next year, with quick integration possible for airlines. Responses from calculator providers acknowledge the study's value. An ICAO spokesperson noted their tool avoids multipliers like the Radiative Forcing Index due to lacking scientific consensus. Google's advisor Dan Rutherford called TIM "accurate and transparent," with plans to add contrails. MyClimate's Kai Landwehr welcomed the input and intends updates soon. IATA did not comment.
This comes amid scrutiny of emission offsets, where some schemes fail to deliver promised reductions.