Emissions of the main air pollutants in Europe

Assessment versions

Published (reviewed and quality assured)

• 13 Oct 2021, 09:32 AM
  - Emissions of the main air pollutants in Europe

Rationale

Justification for indicator selection

No rationale has been identified for this indicator.

Scientific references

• No rationale references available

Indicator definition

This indicator tracks trends since 2005 in anthropogenic emissions of the five main air pollutants — NO_X, NH₃, SO_X, NMVOCs and PM_2.5. All of these pollutants, directly or indirectly, have negative effects on human health, vegetation or ecosystems.

Units

The changes in emissions over time of each main pollutant are given as percentages (%).

Policy context and targets

Context description

Anthropogenic emissions of these air pollutants contribute to air quality problems in Europe. The consequences are adverse health effects caused particularly by PM, and NO₂. PM can be emitted directly into the air (primary PM) or it can be formed in the atmosphere (secondary PM) from airborne precursor substances (NO_X, NH₃, SO_X). Ground-level ozone (O₃) is created from precursor substances (NO₂, NMVOCs, CH₄ and CO) in the atmosphere via photo-chemical reactions and contributes to the formation of secondary PM. Ground-level ozone has negative effects not only on human health, but also on crops and natural ecosystems. In addition, excess deposition of sulphur and nitrogen compounds also lead to disturbances in the functioning and structure of ecosystems, i.e. by causing acidification of soils and waters, and, in the case of nitrogen, eutrophication in nutrient-poor ecosystems such as grasslands.

More detailed summaries of the effects of air pollution on human health and ecosystems are included in the EEA’s indicators ‘Exceedance of air quality limit values in Europe’ (EEA, 2020b) and ‘Exposure of ecosystems to ozone’ (EEA, 2020c).

This indicator supports the assessment of progress towards meeting the national emission ceilings under Directive 2016/2284/EU (EU, 2016) and the Gothenburg Protocol under the 1979 LRTAP Convention (see, for example, EEA, 2020e, 2020g). The 1999 Gothenburg Protocol was amended in 2012 (UNECE, 2021b).

Environment action programmes (EAP) have led the development of EU environment policy since the early 1970s. A new strategy, the clean air programme for Europe, was proposed by the European Commission at the end of 2013 (EC, 2013). Current EU air pollution policy is underpinned by the objectives and long-term goals of, for example, the Seventh Environment Action Programme (7th EAP), which ran until 2020 (EU, 2013). To achieve the objectives of the 7th EAP, EU air pollution legislation has followed a twin-track approach, of implementing both emission mitigation controls and air quality standards. In 2020, the Commission adopted a proposal for a decision on a general EU Environment Action Programme to 2030 (EC, 2020), to continue from the seventh EAP. As part of the European Green Deal (EC, 2019), the EU is revising the Ambient Air Quality Directive, to align air quality standards more closely with the recommendations of the World Health Organization (WHO, 2005).

Internationally, the 1979 UNECE LRTAP Convention (UNECE, 1979) was the first step towards addressing the impacts of air pollution on health and the environment. A centrepiece of this convention is the 1999 Gothenburg Protocol to Abate Acidification, Eutrophication and Ground-level Ozone, amended in 2012 (UNECE, 2021b). The amended protocol set emission ceilings (limits) for the year 2010 and national emission reduction commitments for the emission of the main air pollutants, namely SO_X, NO_X, NH₃ and NMVOCs. It also included reduction commitments for PM_2.5 emissions for 2020. Under the protocol, the critical loads concept was established as a tool for informing political discussions related to damage to sensitive ecosystems (see EEA, 2020c). Critical ozone levels (concentrations) for vegetation were also defined under the LRTAP Convention.

The 1999 Gothenburg Protocol was followed in 2001 by the EU’s NECD, which was repealed by the revised NECD in 2016 (EU, 2016). The original directive introduced legally binding national emission limits for four main air pollutants: SO_X, NO_X, NH₃ and NMVOCs. The directive required that EU Member States had met emission ceilings by 2010 or in the years thereafter, up to the end of 2019, and established emission reduction commitments for 2020-2029 and 2030 onwards for the five main pollutants. The goal of this legislation was to enable the EU to comply with the amended Gothenburg Protocol by 2020, followed by enabling more ambitious emission reductions from 2030 onwards. The human health and environmental objectives defined in the NECD, the Gothenburg Protocol and the EU’s Air Quality Directive (EU, 2008b) are addressed by other EEA indicators (EEA, 2020b, 2020c).

The EU directives currently regulating the ambient air concentrations of the main pollutants are designed to avoid, prevent or reduce the harmful effects of air pollutants on human health and the environment by implementing limit or target values for ambient concentrations of air pollutants. They are:

• Directive 2008/50/EC on ambient air quality and cleaner air for Europe, which regulates ambient air concentrations of SO₂, NO₂ and other nitrogen oxides, coarse particulate matter (PM₁₀) and PM_2.5, lead, benzene (C₆H₆), carbon monoxide (CO) and ozone (EU, 2008b);
• Directive 2004/107/EC relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air (EU, 2004).

In the case of non-compliance with the air quality limit and target values stipulated in EU legislation, air quality management plans must be developed by Member States and implemented in the areas in which exceedances occur. These plans should aim to bring concentrations of air pollutants to levels below the limit and target values. To ensure overall coherence, and consistency between different policies, air quality plans should be consistent (if feasible) and integrated with plans and programmes in line with the directives regulating air pollutant emissions.

Source-specific EU legislation focuses on industrial emissions, road and off-road vehicle emissions, fuel quality standards, etc., by setting emission standards, requiring the use of best-available technology or setting requirements on fuel composition. In addition, several legal instruments are used to reduce environmental impacts from different activities or to promote environmentally friendly behaviour, and these also contribute indirectly to reducing air pollution, as summarised below.

End-of-pipe control in industrial installations:

• Directive 2001/80/EC on the limitation of emissions of certain pollutants into the air from large combustion plants (the LCP Directive) (EU, 2001a): the overall aim of the LCP Directive is to reduce emissions of acidifying pollutants, PM and ozone precursors; it also addresses emissions from large combustion plants, i.e. those with a rated thermal input equal to or greater than 50 MW.

• Directive 2010/75/EU on industrial emissions (integrated pollution prevention and control) (EU, 2010b): this directive targets certain industrial, agricultural and waste treatment installations.

Emission standards for cars:

• The Euro regulations set standards for road vehicle emissions, with the Euro 5 and 6 standards being defined in Regulations (EC) No 692/2008 (EU, 2008a) and No 595/2009 (EU, 2009c). The Communication CARS 2020 (EC, 2012) sets out a timetable for implementation of the Euro 6 vehicle standards in real-world driving conditions, and for the revision of the non-road mobile machinery legislation.

Handling and storage:

• Directive 94/63/EC on the control of volatile organic compound (VOC) emissions resulting from the storage of petrol and its distribution from terminals to service stations (EU, 1994) and Directive 2009/126/EC on Stage II petrol vapour recovery during refuelling of motor vehicles at service stations (EU, 2009b);
• Directive 1999/13/EC on the limitation of emissions of volatile organic compounds (VOCs) due to the use of organic solvents in certain activities and installations (EU, 1999a).

Fuel quality:

• Directive 2012/33/EU amending Directive 1999/32/EC as regards the sulphur content of marine fuels (EU, 2012), Directive 1999/32/EC on the reduction of the sulphur content of certain liquid fuels (EU, 1999b) and Directive 2003/17/EC (amending Directive 98/70/EC) relating to the quality of petrol and diesel fuels (EU, 2003b) regulate fuel quality.

International shipping:

• The International Convention for the Prevention of Pollution from Ships (Marpol) of the International Maritime Organization (IMO) (IMO, 2019) is the main international convention on preventing ships from polluting as a result of operational or accidental causes. Annex VI sets limits on emissions of SO_X, NO_X, VOCs and PM in ship exhausts, and prohibits deliberate emissions of ozone-depleting substances.
• For international shipping, tighter shipping fuel standards and emission standards at IMO/Marpol level resulted in the recent revision of the Sulphur Content of Fuel Directive (EU, 2012).

In addition to the policy instruments outlined above, there are several EU directives that also contribute indirectly to efforts to minimise air pollution. These directives are intended to reduce environmental impacts, including on climate change, and/or to promote environmentally friendly behaviour. Some examples are outlined below.

Agriculture:

• The Nitrates Directive, i.e. Directive 91/676/EEC concerning the protection of waters against pollution caused by nitrates from agricultural sources (EU, 1991), particularly through the implementation of agricultural practices that limit fertiliser application and prevent nitrate losses, aims to reduce agricultural emissions of nitrogen compounds to air.

Energy taxation:

• The Energy Taxation Directive, i.e. Directive 2003/96/EC restructuring the Community framework for the taxation of energy products and electricity (EU, 2003a), establishes minimum taxes for motor fuels, heating fuels and electricity, depending on the energy content of the product and the amount of CO₂ it emits. This directive aims to promote energy efficiency and less-polluting energy products.

Ecodesign:

• The Ecodesign Directive, i.e. Directive 2009/125/EC establishing a framework for the setting of ecodesign requirements for energy-related products, provides consistent EU-wide rules for improving the environmental performance of energy-related products through ecodesign (EU, 2009a), which should benefit both businesses and consumers by enhancing product quality, achieving energy savings and thereby increasing environmental protection. Energy-related products (the use of which impacts energy consumption) include products that use, generate, transfer or measure energy (electricity, gas and fossil fuel). These include boilers, computers, televisions, transformers, industrial fans and industrial furnaces. Some energy-related products do not use energy, but do have an impact on energy use, and can therefore contribute to related savings, such as windows, insulation material, shower heads and taps.
• The Ecodesign Directive is complemented and supported by the Energy Labelling Directive (EU, 2010a) and Directive 2006/32/EC on energy end-use efficiency and energy (EU, 2006).

Targets

National Emission Ceilings Directive (2001/81/EC; amended by (EU) 2016/2284)

The original NECD (EU, 2001b) set pollutant-specific and legally binding emission ceilings for NO_X, NMVOCs, SO_X and NH₃ for each EU Member State. The directive requires Member States to have met the ceilings and interim environmental objectives by 2010 and in the years thereafter (EEA, 2020e). The directive sets specific environmental objectives that address the impacts of acidification and eutrophication on ecosystems, and the harmful effects of ozone on vegetation and human health (see EEA, 2020c).

The NECD was reviewed as part of the clean air policy package (COM/2013). In December 2016, the Council adopted the new directive (Directive (EU) 2016/2284), and reporting under this directive started in February 2017 (EU, 2016). The new directive repealed and replaced the existing EU regime on the annual capping of national emissions of air pollutants, as defined in Directive 2001/81/EC (EU, 2001b). By doing so, it ensures that the national emission ceilings set in the original NECD for 2010 onwards for SO_X, NO_X, NMVOCs and NH₃ are applied until 2020, and it establishes new national emission ‘reduction commitments’, which are applicable from 2020 and from 2030, for SO_X, NO_X, NMVOCs, NH₃ and PM_2.5. The reduction commitments are binding for the period from 2020 to 2029 and from 2030 onwards. In principle, the commitments are indicative for 2025 by a linear emission reduction trajectory. A non-linear reduction trajectory is permissible if it is economically and technically more efficient, and provided that, from 2025, it progressively converges with the linear reduction trajectory.

UNECE Convention on Long-range Transboundary Air Pollution’s Gothenburg Protocol (1999; amended in 2012)

The amended Gothenburg Protocol sets national ceilings (limits) for the emission of the main air pollutants, namely SO_X, NO_X, NH₃, NMVOCs and PM_2.5 (UNECE, 2021b). The EU as a whole has ratified the protocol, and reports emissions to the UNECE (EEA, 2020a).

The target under the amended protocol (UNECE, 2021b) is to ensure that — in the long term and using a stepwise approach that takes into account advances in scientific knowledge — atmospheric depositions or concentrations do not exceed critical loads for the nutrient nitrogen (see EEA, 2020c). Critical levels of ozone for the protection of crops and for the protection of forests have also been defined under the LRTAP Convention, and the critical level for crops is consistent with the EU long-term objective for vegetation (see EEA, 2020c).

The 2010 targets under the NECD and Gothenburg Protocol are included in the EEA’s NECD data viewer (EEA, 2020d) and LRTAP data viewer (EEA, 2020).

Related policy documents

No related policy documents have been specified

Methodology

Methodology for indicator calculation

This indicator is based on national total emissions officially reported to the EEA and the UNECE ‘Co-operative programme for monitoring and evaluation of the long-range transmissions of air pollutants in Europe’ (EMEP) LRTAP Convention. For the 27 EU Member States, the data used are consistent with the emission data reported by the EU in its annual submission to the LRTAP Convention.

Recommended methodologies for emission inventory estimation are compiled in the EMEP/EEA air pollutant emission inventory guidebook (EEA, 2019b). Base data are available from the EEA Data Service (EEA, 2020g) and the EMEP website (CEIP, 2021). Where necessary, gaps in reported data are filled by the European Topic Centre on Air and Climate Change using simple interpolation techniques (see below). The final gap-filled data used in this indicator are available from the EEA’s LRTAP data viewer (EEA, 2020).

References

CEIP, 2021, ‘EMEP Centre on Emission Inventories and Projections’, Centre on Emission Inventories and Projections (https://www.ceip.at) accessed 20 April 2021.

EC, 2012, Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions CARS 2020: Action Plan for a competitive and sustainable automotive industry in Europe, COM/2012/0636 final (EUR-Lex - 52012DC0636 - EN - EUR-Lex (europa.eu))

EC, 2013, Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions — ‘A clean air programme for Europe’ (COM(2013) 918 final).

EC, 2019, Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions The European Green Deal, (COM(2019) 640 final) (EUR-Lex - 52019DC0640 - EN - EUR-Lex (europa.eu)) accessed 02 August 2021.

EC, 2020, Proposal for a DECISION OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL on a General Union Environment Action Programme to 2030, (COM(2020) 652 final) (https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A52020PC0652) accessed 02 August 2021.

EC, 2021, ‘Clean air programme’, European Commission (https://ec.europa.eu/environment/air/clean_air/index.htm) accessed 26 April 2021.

EEA, 2019b, EMEP/EEA air pollutant emission inventory guidebook 2019 — technical guidance to prepare national emission inventories, EEA Report No 13/2019, European Environment Agency (https://www.eea.europa.eu/publications/emep-eea-guidebook-2019).

EEA, 2019c, The European environment — state and outlook 2020: Knowledge for transition to a sustainable Europe, SOER No 2020, European Environment Agency (https://www.eea.europa.eu/publications/soer-2020) accessed 3 September 2020.

EEA, 2020, ‘Air pollutant emissions data viewer (Gothenburg Protocol, LRTAP Convention) 1990-2019’, European Environment Agency (https://www.eea.europa.eu/data-and-maps/dashboards/air-pollutant-emissions-data-viewer-4).

EEA, 2020a, European Union emission inventory report 1990-2018, under the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP), EEA Report No 5/2020, European Environment Agency (https://www.eea.europa.eu/publications/european-union-emission-inventory-report-1990-2018) accessed 15 December 2020.

EEA, 2020b, ‘Exceedance of air quality standards in Europe’, European Environment Agency (https://www.eea.europa.eu/data-and-maps/indicators/exceedance-of-air-quality-limit-2/assessment) accessed 26 April 2021.

EEA, 2020c, ‘Exposure of Europe’s ecosystems to ozone’, European Environment Agency (https://www.eea.europa.eu/data-and-maps/indicators/exposure-of-ecosystems-to-acidification-15/assessment) accessed 26 April 2021.

EEA, 2020d, ‘National Emission Ceilings Directive emissions data viewer 1990-2019’, European Environment Agency (https://www.eea.europa.eu/data-and-maps/dashboards/necd-directive-data-viewer-5) accessed 26 April 2021.

EEA, 2020e, ‘National Emission Reduction Commitments Directive reporting status 2020’, European Environment Agency (https://www.eea.europa.eu/publications/national-emission-reduction-commitments-directive) accessed 26 April 2021.

EEA, 2020f, ‘National Emission Reductions Commitments (NEC) Directive emission inventory data’, European Environment Agency (https://www.eea.europa.eu/data-and-maps/data/national-emission-ceilings-nec-directive-inventory-18) accessed 26 April 2021.

EEA, 2020g, ‘National emissions reported to the Convention on Long-range Transboundary Air Pollution (LRTAP Convention)’, European Environment Agency (https://www.eea.europa.eu/data-and-maps/data/national-emissions-reported-to-the-convention-on-long-range-transboundary-air-pollution-lrtap-convention-15) accessed 16 April 2021.

EEA, 2021, ‘National Emission Reduction Commitments Directive’, European Environment Agency (https://www.eea.europa.eu/themes/air/air-pollution-sources-1/national-emission-ceilings) accessed 26 April 2021.

IMO, 2019, ‘International Convention for the Prevention of Pollution from Ships (Marpol)’, International Maritime Organization (https://www.imo.org/en/About/Conventions/Pages/International-Convention-for-the-Prevention-of-Pollution-from-Ships-(MARPOL).aspx) accessed 26 April 2021.

Norwegian Meteorological Institute, 2010, Transboundary, acidification, eutrophication and ground level ozone in Europe in 2008, EMEP Status Report No 1/2010, European Monitoring and Evaluation Programme (https://emep.int/publ/reports/2010/status_report_1_2010.pdf) accessed 26 April 2021.

UNECE, 1979, Convention on Long-range Transboundary Air Pollution (United Nations Economic Commission for Europe).

UNECE, 2021a, ‘Air’ (https://unece.org/environment-policy/air) accessed 20 April 2021.

UNECE, 2021b, ‘Protocol to Abate Acidification, Eutrophication and Ground-level Ozone’, United Nations Economic Commission for Europe (http://www.unece.org/env/lrtap/multi_h1.html) accessed 26 April 2021.

WHO, 2005, World Health Organisation ‘Air Quality Guidelines Global Update 2005’, https://www.euro.who.int/__data/assets/pdf_file/0005/78638/E90038.pdf, ISBN 92 890 2192 6

Policy references

EU, 1994, European Parliament and Council Directive 94/63/EC of 20 December 1994 on the control of volatile organic compound (VOC) emissions resulting from the storage of petrol and its distribution from terminals to service stations (OJ L 365, 31.12.1994, p. 24-33).

EU, 1991, Council Directive 91/676/EEC of 12 December 1991 concerning the protection of waters against pollution caused by nitrates from agricultural sources (OJ L 375, 31.12.1991, p. 1-8).

EU, 1999a, Council Directive 1999/13/EC of 11 March 1999 on the limitation of emissions of volatile organic compounds due to the use of organic solvents in certain activities and installations (OJ L 85, 29.3.1999, pp. 1-22).

EU, 1999b, Council Directive 1999/32/EC of 26 April 1999 relating to a reduction in the sulphur content of certain liquid fuels and amending Directive 93/12/EEC (OJ L 121, 11.5.1999, p. 13-18).

EU, 2001a, Directive 2001/80/EC of the European Parliament and of the Council of 23 October 2001 on the limitation of emissions of certain pollutants into the air from large combustion plants (OJ L 309, 27/11/2001, pp. 1-21).

EU, 2001b, Directive 2001/81/EC of the European Parliament and of the Council of 23 October 2001 on national emission ceilings for certain atmospheric pollutants (OJ L 309, 27.11.2001, pp. 22-30).

EU, 2003a, Council Directive 2003/96/EC of 27 October 2003 restructuring the Community framework for the taxation of energy products and electricity (OJ L 283, 31.10.2003, p. 51-70).

EU, 2003b, Directive 2003/17/EC of the European Parliament and of the Council of 3 March 2003 amending Directive 98/70/EC relating to the quality of petrol and diesel fuels (OJ L 76, 22.3.2003, p. 10-19).

EU, 2004, Directive 2004/107/EC of the European Parliament and of the Council of 15 December 2004 relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air (OJ L 23, 26.1.2005, pp. 3-16).

EU, 2006, Directive 2006/32/EC of the European Parliament and of the Council of 5 April 2006 on energy end-use efficiency and energy services and repealing Council Directive 93/76/EEC (OJ L 114, 27.4.2006, pp. 64-85).

EU, 2008a, Commission Regulation (EC) No 692/2008 of 18 July 2008 implementing and amending Regulation (EC) No 715/2007 of the European Parliament and of the Council on type-approval of motor vehicles with respect to emissions from light passenger and commercial vehicles (Euro 5 and Euro 6) and on access to vehicle repair and maintenance information (OJ L 199, 28.7.2008, p. 1-136).

EU, 2008b, Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe (OJ L 152, 11.6.2008, pp. 1-44).

EU, 2009a, Directive 2009/125/EC of the European Parliament and of the Council of 21 October 2009 establishing a framework for the setting of ecodesign requirements for energy-related products (OJ L 285, 31.10.2009, pp. 10-35).

EU, 2009b, Directive 2009/126/EC of the European Parliament and of the Council of 21 October 2009 on Stage II petrol vapour recovery during refuelling of motor vehicles at service stations (OJ L 285, 31.10.2009, pp. 36-39).

EU, 2009c, Regulation (EC) No 595/2009 of the European Parliament and of the Council of 18 June 2009 on type-approval of motor vehicles and engines with respect to emissions from heavy duty vehicles (Euro VI) and on access to vehicle repair and maintenance information and amending Regulation (EC) No 715/2007 and Directive 2007/46/EC and repealing Directives 80/1269/EEC, 2005/55/EC and 2005/78/EC (OJ L 188, 18.7.2009, p. 1-13).

EU, 2010a, Directive 2010/30/EU of the European Parliament and of the Council of 19 May 2010 on the indication by labelling and standard product information of the consumption of energy and other resources by energy-related products (OJ L 153, 18.6.2010, p. 1-12).

EU, 2010b, Directive 2010/75/EU of the European Parliament and of the Council of 24 November 2010 on industrial emissions (integrated pollution prevention and control) (OJ L 334, 17.12.2010, p. 17-119).

EU, 2012, Directive 2012/33/EU of the European Parliament and of the Council of 21 November 2012 amending Council Directive 1999/32/EC as regards the sulphur content of marine fuels (OJ L 327, 27.11.2012, p. 1-13).

EU, 2013, Decision No 1386/2013/EU of the European Parliament and of the Council of 20 November 2013 on a general Union environment action programme to 2020 ‘Living well, within the limits of our planet’ (OJ L 354, 28.12.2013, p. 171-200).

EU, 2016, Directive (EU) 2016/2284 of the European Parliament and of the Council of 14 December 2016 on the reduction of national emissions of certain atmospheric pollutants, amending Directive 2003/35/EC and repealing Directive 2001/81/EC (OJ L 344, 17.12.2016, p. 1–31).

Methodology for gap filling

An improved gap-filling methodology was implemented in 2010 that enables a complete time series trend for the main air pollutants (e.g. NO_X, SO_X, NMVOCs, NH₃ and PM_2.5 to be compiled. In cases in which countries did not report emissions for any year, gap filling could not be performed. For these pollutants, therefore, the aggregated data are not yet complete and are likely to underestimate true emissions. Further methodological details of the gap-filling procedure are provided in the European Union emission inventory report 1990-2018 under the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP) (EEA, 2019).

Methodology references

No methodology references available.

Data specifications

EEA data references

• National Emission reductions Commitments (NEC) Directive emission inventory data provided by Directorate-General for Environment (DG ENV)

Data sources in latest figures

Uncertainties

Methodology uncertainty

The use of a gap-filling methodology for countries that have not reported emissions for 1 or more years can potentially lead to artificial trends, but it is considered unavoidable for obtaining a comprehensive and comparable set of emissions data for European countries for policy analysis purposes.

Data sets uncertainty

NO_X emission estimates in Europe are thought to have an uncertainty of about ± 20% (Norwegian Meteorological Institute, 2010), as NO_X is emitted from both fuel burnt and the combustion of air, so emissions cannot be estimated accurately from fuel nitrogen alone. However, because of the need for interpolation to account for missing data, the complete data set used will have a higher degree of uncertainty. The overall trend is likely to be more accurate than individual absolute annual values — the annual values are not independent of each other.

Overall scoring — 1-3; 1 = no major problems, 3 = major reservations:

• relevancy: 1
• accuracy: 2
• comparability over time: 2
• comparability over space: 2.

SO_X emission estimates in Europe are thought to have an uncertainty of about ± 10%, as the sulphur comes from only the fuel burnt; therefore, emissions of SO_X can be more accurately estimated than emissions of NO_X. However, because of the need for interpolation to account for missing data, the complete data set used will have a higher degree of uncertainty. The EMEP has compared modelled and measured concentrations throughout Europe (Norwegian Meteorological Institute, 2010). From these studies, differences in the annual averages have been estimated to be ± 30%, which is consistent with an inventory uncertainty of ± 10% (there are also uncertainties in the measurements and especially in the modelling). The trend is likely to be much more accurate than individual absolute values.

Overall scoring — 1-3; 1 = no major problems, 3 = major reservations:

• relevancy: 1
• accuracy: 2
• comparability over time: 2
• comparability over space: 2.

NH₃ emission estimates in Europe are more uncertain than those for NO_X, SO_X and NMVOCs, largely because of the diverse nature of major agricultural sources. It is estimated that they have an uncertainty of around ± 30% (EEA, 2019b). The overall trend is likely to be more accurate than the individual absolute annual values — the annual values are not independent of each other. 

Overall scoring — 1-3; 1 = no major problems, 3 = major reservations:

• relevancy: 1
• accuracy: 2
• comparability over time: 2
• comparability over space: 2.

Rationale uncertainty

This indicator is regularly updated by the EEA and is used in state of the environment assessments. The uncertainties related to methodology and data sets are therefore important.