For years, many travelers have relied on online carbon footprint calculators to gauge the environmental impact of their flights. However, a new study suggests these tools significantly underestimate the actual carbon emissions generated by air travel—sometimes by a factor of several times. This means your flying could be considerably more damaging to the planet than you realize.
The Problem with Existing Carbon Calculators
Jhuma Sadhukhan and her colleagues at the University of Surrey in the UK recently compared emissions estimates from four established carbon calculators with a new one they developed. The results were startling. Current calculators often fail to accurately reflect the true climate impact of flying.
Consider this example: a first-class flight from Singapore to Zurich on a B777 aircraft. Established calculators such as those from the International Civil Aviation Organization (ICAO) and International Air Transport Association (IATA) estimated around 3000 kilograms of carbon dioxide equivalent. Google’s Travel Impact Model (TIM) put it at around 5000 kg, while MyClimate estimated 8000 kg. However, Sadhukhan and Goean’s newly created Air Travel Passenger Dynamic Emissions Calculator (ATP-DEC) suggested the actual number was more than 14,000 kg—a substantial difference.
Why the Discrepancy?
The ATP-DEC calculator diverges from existing methods in two crucial ways. Firstly, instead of simply assuming an ideal flight path, it leverages historical flight data to estimate the most probable route, flight duration, taxiing time (before take-off and after landing), and the likely occupancy of the aircraft. These factors significantly influence fuel consumption and, consequently, emissions.
Secondly, and equally importantly, ATP-DEC incorporates a wider range of climate impacts associated with air travel. These include the formation of contrails (condensation trails left by aircraft), nitrogen oxide emissions, and the release of water vapor—all of which can have a warming effect on the atmosphere. Contrails, in particular, can have a more significant warming impact than the carbon dioxide released.
Existing calculators often average values for these factors, failing to account for the specific aircraft, fuel conditions, or external atmospheric conditions. The ATP-DEC is more comprehensive.
The dynamic nature of ATP-DEC—continuously updating past flight data—is also critical. Many airlines have been forced to take longer routes due to Russia’s war in Ukraine, a factor that many current calculators don’t yet account for.
A Wider Effort to Improve Accuracy
The team is planning to make their calculator available to others and are developing an app set to launch early next year. They are also prepared to help airlines integrate ATP-DEC into their operations, although setting up the necessary data feeds could take several weeks or months.
The discrepancies highlight a broader conversation about carbon offsetting programs. While many airlines offer passengers the option to voluntarily offset their flight emissions, some studies have questioned the efficacy of these schemes.
Reactions and Future Directions
ICAO acknowledged that its Carbon Emissions Calculator methodology is detailed on its website but stated that it does not currently quantify the climate change impact of non-CO2 gases due to a lack of scientific consensus.
Dan Rutherford at the International Council on Clean Transportation, an organization that advises Google, emphasized that TIM is an accurate and transparent resource and that Google is continuously working to improve it, including integrating short-lived climate pollutants like contrails.
“We appreciate this study as a valuable addition to the ongoing discussion,” says Kai Landwehr at MyClimate. Uncertainties about the warming effects of, say, contrails mean no method can claim to be absolutely right, but using better and more up-to-date data will enhance accuracy.”
The study underscores the need for more accurate and comprehensive methods for calculating the environmental impact of air travel and prompts a reassessment of how we understand and address the carbon footprint of flying. As scientists gain a better understanding of non-CO2 climate impacts, flight emissions calculators will continue to evolve, ultimately leading to more precise and useful tools for travelers and the aviation industry.
