Copenhagen Contrails Conference 25.-26.3. 2025

#CopenhagenContrails

Af/by Poul Kattler, Rådet for Bæredygtig Trafik/Council for Sustainable Transport. For English translation, go down in the document under the solid line!

Se program og oplægsholdere. Se video fra første dag.

Sammendrag

Først takt til organisatorerne, som fik samlet programmet og gennemført denne lidt komplicerede konference. Sammendraget står naturligvis for min egen regning. Vil du læse egentlige noter fra de to dages konference, og fx se uddrag af slides, så fortsæt med at læse her. Sammendrag og noter er udarbejdet både på dansk og engelsk.

Senere undersøgelser end Lee et al (2021) tyder på at ikke-CO2 bidragene ikke ligger i den højeste ende, som Lee viser som ERF = 66,6 mW m-2 eller GWP* på 3,0, men befinder sig i alle nyere studier over de direkte CO2-udledninger. Lee et al er til gengæld det største studie, så vi kan sagtens fortsat referere til dette resultat, men bør pege på at andre, nyere studier har lidt mindre effekt, men dog over CO2 alene. Udover Effective Radiative Forcing (ERF), der viser den aktuelle fysiske virkning, forekommer det rigtigt at benytte GWP*20, som bedst stemmer overens med de klimamål og tidshorisonter, vi er nødt til at operere med, om end at GWP*100 også bruges nogen steder (der får ikke-CO2 til at se mindre alvorligt ud). Det er samlet set en styrke at der nu er en relativ bred anerkendelse af disse ting.

Det er vigtigt at slå fast, at GWP* fortæller hvad der vil ske, hvis flyvning stopper. Men fortsætter flyvning, så er det lige meget med valg af GWP*-metoder, for der vil hele tiden komme nye ikke-CO2 udslip, når disse kortlivede udslip holder op med at virke.

Høj-indkomstlande fylder mest af ikke-CO2 problemet, nemlig 75%. 50% alene fra USA, UK og EU.

Danmark har et ansvar for ikke-CO2 som er over EU-gennemsnittet. Samlet bidrager luftfarten i Danmark med en tredjedel af den danske transportsektors CO2e.  Der er det særlige problem for luftfarten, at andre sektorer i transporten har muligheder for at elektrificere og er allerede i gang med at blive elektrificeret, så flyvningen vil komme til at fylde mere og mere – ganske som andre steder i verden.

Der er uden tvivl gode muligheder for at spare klimaet ved relativt simple omlægninger, så flystriber undgås. Redskaberne er til stede. Men det faktum at det kan opleves som relativt simpelt at reducere luftfartens klimapåvirkning ved at flyve nogle andre ruter, så er det ikke så enkelt i den virkelige verden. Det er farligt at gøre det til et ”easy meal”, som arrangørkredsen havde en tendens til, som kan få politikerne til at blive siddende i lænestolen i stedet for at gøre noget effektivt.

– Som det er med energibesparelser fx ved belysning, at slukke lyset er både det mest simple og det mest effektive. Således gælder det også for flyvningen at de mest effektive klimareduktioner er dem, hvor man undlader at flyve. Som sædvanlig, når det gælder luftfart, er der ingen i rummet, der tør nævne det faktum.

– Det er klogt at tale om hvad industrien OG samfundet er parat til at acceptere, når klimahensyn skal introduceres for alvor for luftfarten. Industrien alene kan måske godt nøjes med at flyve over Atlanten om dagen af hensyn til flystriber (som er en lidt overdrevet konsekvens), men hvad siger passagererne og politikerne? Vi skal hele tiden tage hensyn til, at politikere, erhvervsliv, borgere (fx som turister) stærkt antager at luftfarten ikke kan gøres mindre ”produktiv” uden at det kommer med uacceptable konsekvenser (international mobilitet ses gerne som afgørende parameter fremfor klima).

– I kraft af konferencens overordnede emne om flystriber, så var der ikke meget fokus på de andre ikke-CO2 effekter, som NOX, sod, aerosoler, som T&E og tidligere Stay Grounded har redegjort for. Det giver en ikke uvæsentlig bias. Se T&E’s udmærkede ”læs-let” udgave. https://www.transportenvironment.org/topics/planes/contrails

– Elefanten i rummet var naturligvis om EU’s Emissions Trading System (ETS) skal revideres derhen, hvor ikke-CO2 bliver integreret i ETS og vel og mærke bliver integreret med en pris, der afspejler den egentlige opvarmende effekt. At udgå flystriber mv. må håndteres ligesom brug af SAF og evt. opsamling af kulstof (CCS) som en del af luftfartens omstilling. Det meste af industrien kigger i retning af lovgiverne for at sætte rammer, der kan måles hos økonomidirektørerne. Tror vi at frivillige og individuelle løsninger vil fungere? Nej, det har erfaringerne fra andre brancher tydelig vist. Frivillige ordninger modvirkes også af ekstra omkostninger for brændstof og øget tidsforbrug, som er vigtige modvirkende parametre.

– EU-Kommissionens repræsentant på konferencen viste desværre ikke interesse i at inkludere ikke-CO2 relateret opvarmning i ETS, men er tilfreds med at et system for indberetninger (MRV) heraf netop er indført. Desværre gav konferencen ikke et klart budskab med til EU-Kommissionen om dette med ETS-reform, selvom der var flere lejligheder, hvor det blev bragt på banen.

– Husk på at deltagerne er blandt de grønne dele af luftfarten, af videnskaben og rådgivere, som godt er klar over industriens klimapåvirkning. Det er i sig selv positivt at, problemet er ved at være anerkendt og at der er nogen, der ønsker arbejde med det. Der var faktisk yngre deltagere, der havde fravalgt flyet, da de skulle rejse til København!

– Hvis man politisk gør, som man burde, og hurtigt introducerer økonomiske incitamenter for at reducere flystriber, så vil der sikkert være nogle fly og flyselskaber, der ikke kan eller vil håndtere det, men er det en undskyldning for ikke at gå i gang? Vil systemer og afgifter være 100% fair fra begyndelsen? Det behøver ikke at være fair for hver enkelt flyvning, men så længe at det i det store billede virker, så må detaljerne ikke forhindre at vi gør noget. Reguleringen kan forbedres hen ad vejen. Det svarer til at fiskeriet som i Danmark får en CO2-afgift på brændstof, som ikke alle fiskere kan reagere på – andet ved at betale – men afgiften giver immervæk incitamenter til at ændre noget.

Slides ligger i sin helhed her: Dag 1, dag 2.

---

See program og speakers. See video from the first day.

Summary

First of all, thank you to the organizers, who put together the program and carried out this somewhat complicated conference. The summary is of course at my own expense. If you want to read actual notes from the two-day conference, and see excerpts of slides, continue reading here. Summaries and notes have been prepared in both Danish and English.

Later studies than Lee et al (2021) indicate that the non-CO2 contributions are not at the highest end, which Lee shows as ERF = 66.6 mW m-2 or GWP* of 3.0, but are in all recent studies above the dimension of the direct CO2 emissions. Lee et al is on the other hand the largest study, so we can easily continue to refer to this result, but should point out that other, newer studies have a slightly smaller effect, but still above CO2 alone. In addition to Effective Radiative Forcing (ERF), which shows the actual physical effect, it seems right to use GWP*20, which is best in line with the climate goals and time horizons we need to operate with, although GWP*100 is also used in some places (which makes non-CO2 look less serious). Overall, it is a strength that there is now a relatively broad recognition of these things.

It is important to state that GWP* tells you what will happen if flights stop. But if flying continues, then it does not matter which choice of GWP methods you make, because there will always be new non-CO2 emissions out there when these short-lived emissions stop working.

High-income countries take up the most of the non-CO2 problem, namely 75%. 50% from the US, UK and EU alone.

Denmark has a responsibility for non-CO2 that is above the EU average. In total, aviation in Denmark contributes with a third of the Danish transport sector’s CO2e.  There is a particular problem for aviation that other sectors of transport have opportunities to electrify and are already in the process of being electrified, so aviation will take up more and more space – just like elsewhere in the world.

There are undoubtedly good opportunities to save the climate by relatively simple conversions so that contrails are avoided. The tools are there. But the fact that it can be experienced as relatively simple to reduce aviation’s climate impact by flying some other routes, it is not so simple in the real world. It is dangerous to turn it into an “easy meal”, as the organizers tended to, which can make the politicians stay in the armchair instead of doing something effective.

– As it is with energy savings, e.g. in lighting, turning off the lights is both the simplest and the most effective. Thus, it also applies to aviation that the most effective climate reductions are those where you do not fly. As usual, when it comes to aviation, no one in room dares to mention that fact.

– It is wise to talk about what the industry AND society are prepared to accept when climate considerations are to be introduced for aviation. The industry may be able to fly over the Atlantic during the day for the sake of avoiding contrails (which is a slightly exaggerated consequence), but what do passengers and politicians say? We must constantly take into account that politicians, businesses, citizens (e.g. as tourists) strongly assume that aviation cannot be made less “productive” without it coming with unacceptable consequences (international mobility is often seen as a crucial parameter rather than climate).

– Due to the conference’s overall topic of contrails, there was not much focus on the other non-CO2 effects, such as NOX, soot, aerosols, which T&E and previously Stay Grounded have accounted for. This gives a not insignificant bias. See T&E’s excellent “easy-to-read” version. https://www.transportenvironment.org/topics/planes/contrails

– The elephant in the room was, of course, whether the EU’s Emissions Trading System (ETS) should be revised to the point where non-CO2 is integrated into the ETS and, of course, is integrated with a price that reflects the actual warming effect. Dropping contrails, etc., must be handled, as well as the use of SAF and possibly carbon capture (CCS) as part of the aviation transition. Most of the industry is looking to legislators to set a framework that can be measured by finance directors. Do we believe that voluntary and individual solutions will work? No, experience from other industries has clearly shown this. Voluntary schemes are also counteracted by additional fuel costs and increased time consumption, which are important countervailing parameters.

– Unfortunately, the EU Commission’s representative at the conference did not show interest in including non-CO2 related heating in the ETS, but is satisfied that a system for reporting (MRV) of this has just been introduced. Unfortunately, the conference did not give a clear message to the European Commission about this with ETS reform, although there were several occasions where it was brought up.

– Remember that the participants are among the green parts of aviation, by science and advisors, who are well aware of the industry’s climate impact. It is in itself positive that the problem is being recognized and that there is someone who wants to work with it. There were actually younger participants who had opted out of the plane when they were going to travel to Copenhagen!

– If you politically do as you should and quickly introduce financial incentives to reduce contrails, then there will probably be some planes and airlines that cannot or will not handle it, but is that an excuse not to get started? Will systems and charges be 100% fair from the outset? It doesn’t have to be fair for every single flight, but as long as it works in the big picture, the details must not prevent us from doing something. Regulation can be improved along the way. This corresponds to the fishery getting a CO2 tax on fuel, which not all fishermen can react to – other than by paying – but the tax does provide incentives to change something.

All slides from the presentations will you find here: Day 1, day 2.