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UNECE takes the lead in tackling air pollution issues affecting human health with additional benefits for climate change by reducing black carbon emissions

Published: 15 April 2011


Meeting at the forty-eighth session of the Working Group on Strategies and Review in Geneva this week, countries are considering concrete strategies to reduce black carbon emissions, one of the air pollutants identified by scientists as an important link to climate change because of its role in contributing to global warming.

The United Nations Economic Commission for Europe (UNECE) Convention on Long-range Transboundary Air Pollution is the first international treaty to take steps to curb such emissions, once again leading the way in addressing emerging pollution issues in an ever more complex and interconnected world.

The reduction of black carbon is being targeted through a revision of the Convention’s Protocol to Abate Acidification, Eutrophication and Ground-level Ozone (Gothenburg Protocol), which will now include black carbon as a component of fine particulate matter. The detailed dispositions of the Protocol to include black carbon and determine black carbon emission reduction measures are the subject of negotiations by representatives of Parties to the Protocol this week.

The International Institute for Applied Systems Analysis estimates current anthropogenic emissions of black carbon from the UNECE area at about 800 Gg, which represents about 15% of the world’s total. Nearly 50% of these emissions originate from the United States of America and the Russian Federation, while another 25% is produced by the EU-15.

Black carbon, like ozone, is a so-called “short-lived climate forcer” i.e., a warming agent with a relatively short lifetime in the atmosphere ranging between days and weeks. Reducing levels of such agents in the atmosphere is therefore a means to improve air quality, and thus human health, but also to immediately act on slowing down climate change.

According to the findings of the Ad Hoc Expert Group on Black Carbon discussed by policymakers this week, black carbon emissions in the UNECE region are expected to decline between 2000 and 2020 by about one third, primarily as a result of ongoing implementation of current emission control legislation in the transport sector. However, additional measures could reduce them by another 40% by 2020.

The most important sectors with black carbon mitigation potential are:

  • Residential combustion: Nearly 50% of the remaining mitigation potential for black carbon emissions in the UNECE region is to be found in the residential heating sector. This will become the dominating source of black carbon emissions in most countries in the region by 2020, and cause about half of total emissions. This trend could be even stronger if additional biomass combustion is promoted as a climate policy measure. Mitigation measures include increasing combustion efficiency, for instance via the use of wood pellets (instead of raw wood or biomass) and modern combustion stoves and boilers.
  • Off-road machinery vehicles, such as diesel propelled heavy vehicles used in industry, construction, agricultural and forestry, which have a long lifetime and often are poorly maintained, offer the second largest reduction potential for black carbon emissions in the UNECE region — about 20%. This can be achieved mainly through eliminating high-emitting vehicles and enforcing the Euro VI standards and accelerated introduction of diesel particle filters (DPFs).
  • The Road transport sector can deliver additional reductions through the elimination of high-emitting vehicles (super emitters) and accelerated introduction of DPFs for light duty and heavy duty vehicles, as well as retrofitting of existing vehicles. Overall, in 2020 these measures would account for less than 10% of the total mitigation potential in the UNECE region.
  • Open burning of agricultural waste: An effective ban on this could account for about 10% of the total reduction potential for black carbon emissions.

It should be stressed that these measures cannot replace carbon dioxide reductions, which are indispensable to mitigate long-term climate change.

The current revision of the Gothenburg Protocol with the inclusion of black carbon is scheduled for completion and adoption by December 2011.

In the medium and long term, the UNECE Air Convention will investigate more closely the regional impacts of reducing the levels of tropospheric ozone and its precursors, including methane and carbon monoxide, considering both climate change and air quality/health/agriculture benefits.

Importantly, the solutions implemented by UNECE member States could successfully be replicated in other regions, especially in Asia, where air pollution is a serious and growing concern (emissions of black carbon from China and India alone account for approximately 25%–35% of global emissions, and new estimates indicate that black carbon emissions for China in 2006 have doubled since 2000). Please see

Note to editors

Black carbon is an air pollutant formed through the incomplete combustion of fossil fuels, biofuel and biomass. As a component of fine particulate matter (PM2.5), it is associated with significant adverse health effects, including increased morbidity and mortality from cardiovascular and respiratory conditions and lung cancer. In 2000, the life expectancy loss due to PM2.5 for the UNECE region was 8.3 months on average (8.6 for the EU and 7.7 for countries outside the EU according to a recent report by the International Institute for Applied Systems Analysis (IIASA). Please see, Report_on_Cost_effective_emission_reductions_to_improve_air_quality_in_Europe_in_2010.pdf. This could be reduced to and average of 3.6 months in 2020 (3.5 for EU-27 and 3.8 for non-EU countries) at a cost amounting to 0.01(EU)–0.05(non-EU)% of gross domestic product (GDP) depending on the measures agreed in the revision of the Gothenburg Protocol.

In addition, black carbon contributes significantly to global warming by directly absorbing sunlight and thus warming up the atmosphere, and to regional warming by darkening ice and snow. The contribution to warming of 1g of black carbon seen over a period of 100 years has been estimated to be in a range between 100 to 2,000 times higher that that of 1g of carbon dioxide (CO2) (see Mitigation of black carbon will thus lead to beneficial regional impacts via the reduction of deposits on snow and ice. The positive effects of this action could be especially important in sensitive regions such as the Arctic, which is warming faster than other regions.

Short-lived climate forcers (SLCFs) are substances like black carbon, troposheric ozone and methane that have relatively short lifetimes in the atmosphere ranging between days and weeks (black carbon  and ozone) and up to several years (methane) and which contribute to global warming by absorbing solar radiation. Within SLCFs, methane, tropospheric ozone and black carbon are key contributors to global warming, augmenting the radiative forcing of carbon dioxide by 65% (see

The Expert Group on Black carbon, chaired by Norway and the United States, was established in June 2010. Its mandate was to identify options for potential revisions to the Convention’s 1999 Gothenburg Protocol that would enable the Parties to mitigate black carbon as a component of particulate matter for health purposes while also achieving climate co-benefits. The report of the expert is group is available at:

Ground-level ozone is a toxic pollutant which forms when pollutants from vehicles, power plants, refineries and other sources undergo a chemical reaction in the presence of sunlight. It contrasts with stratospheric ozone, naturally occurring ozone which protects the Earth from ultraviolet radiation. Ground-level ozone has proven severe effects on human health and can damage plants (including cash crops).

The Convention on Long-range Transboundary Air Pollution addresses some of the major environmental problems of the UNECE region through scientific collaboration and policy negotiation. Created in 1979, the Convention is extended by eight protocols that identify specific measures to be taken by Parties to cut their emissions of air pollutants. Parties develop policies and strategies to combat the discharge of air pollutants through exchanges of information, consultation, research and monitoring.

The 1999 Gothenburg Protocol to Abate Acidification, Eutrophication and Ground-level Ozone entered in to force in 2005. The current Protocol sets emission ceilings for 2010 for pollutants such as sulphur, nitrogen oxides, volatile organic compounds and ammonia. The Protocol also sets tight limit values for specific emission sources (e.g., combustion plant, electricity production, and vehicles) and requires best available techniques to be used to keep emissions down. The upcoming revisions will focus upon establishing new targets and including new pollutants in light of recent scientific findings. The Protocol currently counts 26 Parties: Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Finland, France, Germany, Hungary, Latvia, Lithuania, Luxembourg, Netherlands, Norway, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, the former Yugoslav Republic of Macedonia, the United Kingdom and the United States, as well as the European Union.

Ref: ECE/ENV/11/P16

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