Global Aviation Emissions Nearly 300 Million Metric Tons Higher Than Reported for 2019, Study Finds

A new study has uncovered that flight-related emissions from 2019 are far higher than reported. Scientists reviewed data for more than 40 million flights in 2019 and calculated the total global aviation emissions to be about 911 million metric tons, well above the 604 million metric tons reported to the United Nations in 2019.

While many countries report emissions to the United Nations following the 1992 international treaty, the United Nations Framework Convention on Climate Change (UNFCCC), developing countries (or non-Annex I countries) aren’t required to submit aviation emissions, based on the treaty. However, some countries can still opt in to reporting their emissions.

So a team of scientists used a high-resolution aviation transport emissions assessment model to review and calculate emissions for 197 countries for 2019. They found that aviation emissions were about 50% higher than the numbers reported to the UN for that year and published their findings in the journal Environmental Research Letters.

“Now we have a much clearer picture of aviation emissions per country, including previously unreported emissions, which tells you something about how we can go about reducing them,” Helene Muri, co-author of the study and a research professor at the Norwegian University of Science and Technology’s Industrial Ecology Programme, said in a statement.

According to the study, the U.S. had the highest aviation-related emissions of any country, both when considering international flights and domestic flights. But the model revealed that China, which did not report its flight emissions to the UN in 2019, was the country with the second-highest emissions, revealing large gaps of data in the reporting.

The model used in the study calculated carbon emissions as well as other pollutants, including nitrogen oxides, sulfur oxides, unburned hydrocarbons, black carbon and organic carbon. It also allows for emissions modeling almost in real-time, which can help track emissions even for countries not required to report.

“I think it very nicely illustrates the potential in this type of work, where we have previously relied on statistical offices and reporting loops that can take a year or more to get this kind of information,” Anders Hammer Strømman, co-author of the study and a professor at the university’s Industrial Ecology Programme, said in a statement. “This model allows us to do instant emissions modeling — we can calculate the emissions from global aviation as it happens.”

According to the International Energy Agency, aviation makes up about 2% of global emissions, and the amount of flight-related emissions needs to decrease to meet net-zero emissions targets by 2050. But the study authors pointed out that about 1% of global emissions linked to aviation are not being reported.

“Our work fills the reporting gaps, so that this can inform policy and hopefully improve future negotiations,” said Jan Klenner, first author of the study and a Ph.D. candidate at the Industrial Ecology Programme.