Frequent flying wipes out Zurich residents’ green gains at home

Air travel remains one of the most carbon-intensive activities, highlighting the growing contradiction between frequent flying and climate goals in Switzerland. Illustration: Kai Reusser / SWI swissinfo.ch

Zurich residents fly more than 10,000 kilometres a year on average. Those flights cause more climate pollution per person than all the heating systems, cars, buses and energy used inside the city combined. 

For years, Zurich officials have touted their city’s climate progress. They say it is on track to reach net zero for territorial emissions by 2040. But outside of the city’s borders, Zurich residents are contradicting these gains. 

According to Zurich’s latest interim climate report (called the Netto-Null-Zwischenbericht) around 16% of residents’ climate footprint is produced within the city of Zurich itself. The remaining 84% comes from indirect, consumption-based emissions generated abroad.

Taken together, these emissions amount to around 11.9 tonnes of CO₂-equivalent per person per year – a roughly 20% increase from 1990. The increase is driven primarily by outside emissions – imported goods and services. Of all these, aviation is the single largest contributor, accounting for roughly 50% more CO2 on average than all of residents’ activities inside the city.

Most of Zurich residents’ climate footprint comes from indirect emissions such as travel, consumption and imported goods rather than emissions produced within the city. Illustration: Kai Reusser / SWI swissinfo.ch

This poses a challenge for local officials. The government is limited in what it can regulate outside of its boundaries, leaving personal action as the primary way to address pollution. 

“Zurich’s climate target is reachable,” says Sascha Nick, a physicist and economist who works on consumption and societal transitions at EPFL, the polytechnic institute in Lausanne. “But they are not going to reach it if they continue doing what they’re doing so far.”

A closer look at Zurich’s footprint

Measured territorially, Zurich’s emissions story looks like a success

Within the city of Zurich, direct emissions have fallen steadily in recent years and are now at around 2.2 tonnes of CO₂ equivalents per person. That puts Zurich in the upper- middle range of European cities with published climate inventories. In comparison, Copenhagen, a city often cited for aggressive climate action, reported roughly one tonne of CO₂ per person in 2024, while Berlin reported around 3.6 tonnes of CO₂ per person in the same year.

“This confirms that our local measures in buildings, mobility and energy are effective,” says Andreas Hauri, a member of Zurich’s city council and head of the Department of Health and Environment.

In the skies above the city, however, the picture is different. In 2024, Zurich residents flew an average of 10,500 kilometres per person – roughly the equivalent of a round-trip flight from Zurich to Dubai each year. That marks an increase of around 600 kilometres over the year before. Emissions from flights rose by roughly 110 kilograms of CO₂-equivalent per resident.

Flying now releases around 3.2 tonnes of CO₂-equivalent per person. This exceeds a similar measurement conducted in Geneva in 2019, which found the per-capita emissions from air travel were 2.3 tonnes on average. It also exceeds what climate science considers compatible with the Paris Agreement. To stay on a 1.5°C pathway, average per-capita emissions from all sources combined would need to fall to around 2.7 tonnes per year by 2035.

The emissions Zurich cannot regulate

City officials say aviation emissions are the result of structural conditions rather than a lack of awareness. Flying is relatively cheap and easily accessible. Zurich residents’ high purchasing power and the city’s international connections amplify the effect.

Unlike buildings, heating systems or cars, flying largely escapes municipal policy provisions. The city can only attempt to limit flying through awareness campaigns and the promotion of alternatives such as international rail and night trains – options that depend largely on national and international investment.

Flying from Zurich to Berlin produces significantly higher greenhouse gas emissions per person than travelling by car or train. Illustration: Kai Reusser / SWI swissinfo.ch

Personal changes could have a sizeable effect. When flying largely stopped during the Covid lockdowns, Zurich residents’ overall climate footprint dipped.

“The Covid years give us a sense of the scale,” Sascha Nick of EPFL says. “They show roughly how far current levels of flying would have to come down if emissions were to fall in a sustained way.”

Nick and his co-authors estimate that aligning air travel with climate goals would require passenger kilometres to fall to levels last seen in the 1980s, when average air travel per person was roughly seven times lower than today.

Efficiency gains in air travel are unlikely to be enough to drop emissions to sustainable levels. More efficient aircraft and increased use of sustainable aviation fuels would not reduce flight emissions to even 1990 levels by mid-century, according to an analysis Zurich officials commissioned.

How Zurich calculates individual emissions

Many cities have residents who fly frequently, but Zurich is among the few cities to produce a measurement that calculates individual carbon emissions so precisely. The city combines direct atmospheric CO₂ measurements with a detailed consumption-based emissions inventory.

As part of the European ICOS Cities research project, scientists at the Swiss Federal Laboratories for Materials Science and Technology (EMPA) installed high-precision sensors around Zurich that measure how much CO₂ the city emits.

Emissions that occur outside the city, so called indirect emissions, are estimated using detailed data on residents’ spending, travel behavior and supply chains.

“Reliable emissions data based on atmospheric observations are crucial to support the city’s net-zero action plan,” says Lukas Emmenegger, who leads Empa’s CO₂ measurement work in Zurich.

Zurich was one of three pilot cities in the ICOS Cities project – alongside Paris and Munich – that helped develop new urban CO₂ monitoring methods. Although the official pilot phase is concluding, researchers involved aim to use the tools and lessons from the project to support other cities in setting up similar monitoring systems.

Why the gap matters

Zurich’s situation shows how local efficiency efforts need to be matched by behavioral changes. 

On a consumption basis, Switzerland ranks among the highest-emitting countries in the world. In 2023, emissions linked to what Swiss residents consume amounted to about 13.3 tonnes of CO₂ per person, placing the country alongside South Korea and Australia, and above Canada, Taiwan and Luxembourg, among other countries. Only a few nations – including the United States and Belgium, as well as several energy-exporting states – recorded higher per-capita consumption emissions. 

For a country that imports much of what it consumes, this imbalance is structural. As territorial emissions fall, emissions linked to what residents consume abroad play an increasingly decisive role in whether Switzerland’s overall climate impact actually declines. 

“Once you focus only on what happens inside the city or the country, emissions can look like they are going down, while the overall impact does not,” Nick says. “At that point, consumption becomes decisive.” 

What is the ICOS Cities project?

ICOS Cities was a European pilot project testing new ways to measure urban CO₂ emissions. 

Zurich, Paris and Munich served as pilot cities, combining atmospheric measurements with emissions inventories. 

The project aimed to develop methods other cities can use, not just city-specific studies. 

The pilot phase has ended, and Zurich plans to integrate the approach into its long-term climate strategy. 

Edited by Gabe Bullard/sb