REPORT FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT AND THE COUNCIL Updated analysis of the non-CO2 climate impacts of aviation and potential policy measures pursuant to EU Emissions Trading System Directive Article 30(4)
Date: 2020-11-23
Institutions: Directorate-General for Climate Action, European Commission
Subjects: EU Emissions Trading Scheme, EU emission allowance, air quality, air transport, climate change, environmental impact, environmental research, greenhouse gas, reduction of gas emissions, tradeable emission permit

EN 

  EN 

   EUROPEAN COMMISSION  Brussels, 23.11.2020  COM(2020) 747 final  REPORT FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT AND THE COUNCIL Updated analysis of the non-CO2 climate impacts of aviation and potential policy measures pursuant to EU Emissions Trading System Directive Article 30(4)   {SWD(2020) 277 final}  
 
 
UPDATED ANALYSIS OF THE NON-CO2 CLIMATE IMPACTS OF AVIATION 
AND POTENTIAL POLICY MEASURES PURSUANT TO EU EMISSIONS 
TRADING SYSTEM DIRECTIVE ARTICLE 30(4) 

1. Introduction 

As part of the 2017-revision of the EU Emissions Trading System (ETS) regarding aviation, 
the co-legislators tasked the European Commission with presenting “an updated analysis of 
the non-CO2 effects of aviation, accompanied, where appropriate, by a proposal on how best 
to address those effects”, as per Article 30(4) of Directive 2003/87/EC.  

Previous analyses date back to the 2006  Impact  Assessment for the  inclusion of aviation in 
the  EU  ETS  that  examined  the  possibility  of  regulating  oxides  of  nitrogen  (NOx),1  and  the 
2008  study  ‘Lower  NOx  at  Higher  Altitudes:  Policies  to  Reduce  the  Climate  Impact  of 
Aviation NOx Emission’.2 At the time of those analyses, the scientific understanding was not 
considered  sufficiently  mature  to  propose  policies  to  address  these  impacts.  Instead,  since 
2012,  the  EU  ETS  as  the  cornerstone  of  the  EU’s  climate  policy  regulates  solely  carbon 
dioxide  (CO2)  emissions  from  covered  flights,  which,  in  contrast  to  non-CO2  impacts, 
directly correlate with the amount of fuel burned. 

To  fulfil  the  requirement  of  Article  30(4)  of  the  EU  ETS  Directive,  a  report  was 
commissioned by the European Commission to the European Union Aviation Safety Agency 
(EASA).  The  report  captures  the  much-evolved  scientific  understanding,  presenting  an 
updated  analysis  of  the  main  climate  impacts  associated  with  air  traffic,  besides  CO2 
emissions. EASA conducted the work through a project team comprising renowned experts in 
this field from the EU, Norway and UK, covering the whole spectrum of different schools of 
thought  in  the  climate  science  domain.  This  allowed  for  open-minded  discussions  and  the 
consideration of diverging opinions in the analysis of all issues identified. Combined with the 
validation  of  this  work  through  two  peer  reviews,  this  ensured  the  scientific  rigour  of  the 
provided analyses. 

The following guiding research questions structured the work of the experts: 

  What  is  the  most  recent  knowledge  on  the  climate  change  effects  of  non-CO2 

emissions from aviation activities? 

  What factors/variables have had an impact on these effects  - e.g. technology/design, 
operations, fuel, market-based measures? What is the level of that impact? Do these 
factors/variables exhibit trade-offs or interdependencies between different impacts? 
  What  research  has  been  undertaken  on  potential  policy  action  to  reduce  non-CO2 
climate  impacts?  What  are  the  pros  and  cons  of  policy  options  in  terms  of 
implementation? What knowledge gaps still exist? 

The  non-CO2  impacts  assessed  by  the  experts  arise  namely  from  emissions  by  aircraft  of 
oxides  of  nitrogen  (NOx),  soot  particles,  oxidised  sulphur  species,  and  water  vapour.  Their 
net  impact  is  a  warming  effect  on  the  climate,  although  there  are  a  number  of  individual 

1 https://ec.europa.eu/clima/sites/clima/files/transport/aviation/docs/sec_2006_1684_en.pdf 
2 
https://ec.europa.eu/transport/sites/transport/files/modes/air/studies/doc/environment/oct_2008_nox_final_report
.pdf 

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warming and cooling effects from the respective aviation non-CO2 emissions, with trade–offs 
and uncertainties of different degrees. 

The authors note that the scientific understanding on the climate change effects of non-CO2 
emissions from aviation activities has advanced over the last ten years. With regard to these 
impacts,  and  how  to  assess  them  in  terms  of  CO2-equivalent  emissions  metrics,  several 
uncertainties remain and new ones have emerged. The report identifies and evaluates a range 
of policy options as well as research areas to be tackled to address these uncertainties.  

2. Summary of the report’s findings on policies  

The  report  acknowledges  that  there  are  already  a  number  of  measures  in  place  that  also 
contribute  to  reducing  the  climate  impacts  of  aviation  non-CO2  emissions  such  as  EASA 
environmental certification standards for aircraft  engine emissions of NOx and non-volatile 
Particulate  Matter  (nvPM).  Reductions  in  fuel  burn,  and  thereby  CO2  emissions,  from 
improvements in air traffic management through the Single European Sky will also generally 
reduce non-CO2 emissions. 

Possible additional policy options to address non-CO2 climate impacts from aviation assessed 
in  the  report  are  divided  into  three  categories:  financial/market-related,  fuel,  and  air  traffic 
management (ATM), with two options under each of these. In principle, the options could co-
exist with one another.  

The two financial measures analysed consist in a monetary charge levied on aircraft NOx 
emissions  on  one  side  and/or  the  inclusion  of  such  emissions  under  the  EU  ETS  on  the 
other  side.  These  would  further  incentivise  manufacturers  and  airlines  to  reduce  these 
emissions and need to take account of the associated trade-offs. Outstanding research issues 
towards  making  any  such  policies  implementable  include  the  need  to  better  understand  the 
potential  net  cooling  effect  from  aircraft  NOx  emissions  under  certain  future  scenarios  of 
declining emissions of tropospheric ozone precursors from surface (non-aircraft) sources; the 
need  for  an  accurate,  internationally  recognised  methodology  for  estimating  cruise  NOx 
emissions; the need for an appropriate CO2-equivalent emissions metric and time horizon for 
NOx emissions, taking into account the trade-off between NOX and CO2 emissions in engine 
design;  as  well  as  identifying  an  appropriate  level  of  a  charge.  Given  these  outstanding 
research  issues,  the  report  estimates  that  these  financial  measures  could  potentially  be 
implemented in the mid-term, i.e. in 5 to 8 years. 

The  fuel-related  measures  comprise  the  reduction  of  aromatics  within  fuel  (leading  to 
cleaner  fuel  burn  and  reduced  nvPM  emissions)  and  the  mandatory  use  of  Sustainable 
Aviation Fuels (SAF). Both measures target emissions of soot particulates and contrail cirrus 
clouds.  Reducing  aromatics  content  would  require  fuel  producers  to  adapt  their  production 
processes  and  a  system  to  monitor  the  aromatics  content  of  fuels.  Given  a  set  of  research 
issues  that  would  need  to  be  addressed  according  to  the  experts  and  the  preference  for  an 
international  standard,  this  measure  could  potentially  be  introduced  in  the  mid-  (i.e.  5  to  8 
years)  to  long-term  (i.e.  8+  years).  The  mandatory  use  of  SAFs  could  be  implemented 
through an EU blending mandate specifying that a certain gradually increasing percentage of 
the  total  jet  fuel  sold  over  a  set  time  period  would  have  to  be  SAF.  If  well  designed,  this 
should  lead  to  simultaneous  reductions  in  nvPM  and  sulphur  emissions  (though  not  NOx 

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emissions)  and  CO2  emissions.  The  experts  consider  that  this  measure  could  potentially  be 
implemented in the short- (i.e. 2 to 5 years) to mid-term (i.e. 5 to 8 years).  

The  measures  in  the  ATM  category  are  avoidance  of  ice-supersaturated  areas  and  a 
“climate  charge”.  While  optimizing  the  flight  trajectory  to  avoid  ice-supersaturated  areas 
and other regions considered climate-sensitive, would reduce the formation of contrail-cirrus 
clouds,  a  climate  charge  would  address  all  non-CO2  effects  (NOx,  water  vapour,  soot, 
sulphates, contrails).3 As a series of research issues that would first need to be addressed, the 
measure to avoid ice-supersaturated areas could potentially be introduced in the midterm, i.e. 
5  to  8  years,  according  to  the  experts.  Regarding  a  climate  charge,  the  experts  deem  that 
given the broader nature of the measure and the associated "significant" research needed, it 
could potentially be implemented in the long-term, i.e. 8+ years. 

3. Towards policies targeting aviation’s full climate impacts 

The significance of non-CO2 climate impacts from aviation activities, previously estimated to 
be at least as important in total as those of CO2 alone is fully confirmed by the report. This 
results  in  a  need  to  consider  how  to  best  to  address  them  further  to  contribute  to  the  EU's 
climate objectives and the Paris Agreement, complementary to climate action already being 
taken.  This  would  allow  moving  towards  policies  targeting  aviation’s  full  climate  impacts. 
This would also result in co-benefits regarding local air quality. 

However, the complexity of non-CO2 climate impacts relative to CO2 ones and the trade-offs 
between various impacts, poses a challenge to the policy measures analysed in the report and 
summarised  above.  This  report  is  an  important  step  towards  better  knowledge,  both  on  the 
science  and  on  policy  measures  and  the  Commission  will  further  examine  the  measures 
suggested  by  the  experts,  each  with  its  associated  advantages  and  drawbacks.  The  specific 
issues identified in the report need to be addressed in order to take these potential measures 
forward at EU level. Without necessarily being exhaustive, three main dimensions for further 
work could be envisaged: 

First, the scientific consensus indicates that – from measurements at ground and altitude – the 
use of sustainable aviation fuels – be it advanced biofuels or power-to-liquid fuels – reduce 
soot  particulate  emissions.  The  ReFuelEU  Aviation  initiative,  already  announced  under  the 
European  Green  Deal,  aims  to  provide  climate  benefits  through  both  lower  life-cycle  CO2 
emissions  and  lower  nvPM  emissions.  In  addition,  Commission  services  could  further 
explore the possibility to make the current global standard for maximum aromatics content in 
aviation fuels more stringent. 

Secondly, there is a clear need for additional research, to increase knowledge and certainty of 
the various non-CO2 impacts and trade-offs between them. This requires measuring emissions 
at the different stages of flights and related to different types of fuels. Related and of crucial 
importance  are  accurate  factors  that  compare  the  climate  change  impact  of  non-CO2 
emissions to CO2 emissions, due to the different timescales on which these pollutants operate. 
Further research on metrics and time horizons could be used to assess the impact of potential 

3 The concept of a climate charge is to levy a charge on the full climate impact of each individual flight 
(separate from the EU ETS). This makes it the measure with the broadest coverage. 

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policy measures. Horizon Europe provides a suitable platform at EU level for supporting such 
research.  

Thirdly,  increasing  the  efficiency  of  operational  measures,  in  particular  Air  Traffic 
Management  is  key  and  needs  European  coordination.  For  instance,  a  potential  first  step 
towards full optimisation of flight profiles for lower climate impacts could focus on ways to 
avoid  ice-supersaturated  areas  and  the  formation  of  persistent  contrails  over  the  Atlantic 
airspace, in order to complement the work carried out since 2013 in this area.4 An enhanced 
capability  to  predict  accurately  the  formation  of  persistent  contrails  would  be  needed  to 
support the implementation of this policy option.    

In conclusion, the Commission takes note of the findings of the report consolidating the state 
of the art of the climate science on the subject, as well as identifying potential measures to 
address these. The Commission commends the enclosed EASA report as an updated analysis 
of  the  non-CO2  effects  of  aviation  under  Article  30(4)  of  Directive  2003/87/EC,  and  will 
further examine the measures suggested therein. 

4 See, for instance, the project ATM4E at: https://www.atm4e.eu  

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