ANKARA

Greenhouse gas emissions from air travel to UN climate conferences have increased 25-fold over the past three decades as attendance has grown significantly, according to a study published Thursday in Nature.

Researchers estimated emissions generated by official delegates traveling to the annual Conference of the Parties (COP) meetings under the United Nations Framework Convention on Climate Change (UNFCCC).

The analysis examined travel to all conferences from COP1 in 1995 through COP29 in 2024.

The study found that official delegates produced an estimated 710,282 tons of carbon-dioxide-equivalent emissions from air travel over the period.

Emissions rose from 2,959 tons of carbon dioxide equivalent at the first conference to 76,931 tons at the 29th conference.

This represents an increase of about 2,500% over the nearly three-decade period.

The researchers said the increase was largely proportional to the growth in delegate attendance.

A total of 367,747 people attended COP meetings between 1995 and 2024.

Of those participants, 197,566 were official party or observer-state delegates whose travel emissions were included in the analysis.

Attendance and overall emissions reached their highest levels during COP28 in Dubai, UAE.

The Conference of the Parties serves as the main decision-making body of the UN climate convention and brings together governments and other stakeholders to negotiate climate policies.

Major international climate agreements have been adopted at these meetings, including the Kyoto Protocol in 1997 and the Paris Agreement in 2015.

The conferences typically include representatives from governments, UN agencies, non-governmental organizations, businesses, academic institutions, activists, and journalists.

-Transportation with fossil fuels

The researchers said transportation accounts for approximately 15% of global greenhouse gas emissions.

Within the transport sector, aviation is among the most emissions-intensive forms of travel because aircraft rely largely on fossil fuels.

The study estimated emissions using a dataset of conference attendees and global flight-route data.

Researchers calculated emissions per attendee and multiplied those values by the number of delegates from each country to estimate total emissions for each conference.

Both indirect emissions and well-to-tank emissions from fuel production and transport were included in the main analysis.

Indirect emissions include effects associated with water vapor, nitrogen oxides, and contrails produced during flights.

Researchers also conducted sensitivity analyses to evaluate how the results would change if these factors were excluded.

When well-to-tank emissions were excluded, estimated total emissions declined to 632,502 tons of carbon-dioxide-equivalent.

When indirect emissions were excluded, the total fell to 451,136 tons.

Excluding both categories reduced estimated emissions to 373,357 tons.

-Per-person emissions

The study also examined emissions per attendee at individual conferences.

Per-person emissions ranged from 2.77 tons of carbon-dioxide-equivalent at COP9 in Italy to 6.22 tons at COP4 in Argentina.

Higher emissions per attendee were generally associated with conferences located farther from Europe, where many delegates are based.

Conferences hosted in Europe and Central Asia typically recorded lower per-attendee emissions because many participants traveled shorter distances.

Nearly half of all COP meetings -- 14 of the 29 held so far -- have taken place in Europe and Central Asia.

The researchers said that although travel emissions associated with COP meetings are significant, the diplomatic process itself can produce agreements aimed at reducing global emissions.

“Face-to-face interactions play a critical role in international diplomacy,” the study said.

The researchers also noted that implementation of the Paris Agreement “has the potential to avoid exponentially greater emissions than those generated by the conference itself.”

The study found that increasing attendance is the main factor behind rising travel-related emissions from the conferences.

Researchers said future efforts to reduce emissions could include managing the overall scale of participation.

At the same time, they emphasized that participation should remain inclusive and reflect the perspectives of communities most affected by climate change.

Prioritizing participation by climate-vulnerable nations, Indigenous groups, youth, and civil society “can help ensure that the conference remains focused on advancing equitable climate solutions,” the study said.

The analysis relied on attendance records covering COP1 through COP29 and global flight-route data to estimate return air-travel emissions for official delegates nominated by participating countries.

The researchers noted that emissions from conference travel must be weighed against the value of rotating host locations to ensure broad representation in international climate negotiations.