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TF HTAP/TFIAM Workshop on Global Air Pollutant Emission Scenarios

11-13 February 2015, International institute for Applied Systems Analysis (IIASA), Laxenburg, Austria

Meeting Agenda

Workshop Objectives:

While substantial efforts have been devoted to global analyses of the emissions of carbon dioxide (CO2) and other long-lived greenhouse gases, air pollutant emissions have received only limited attention in the global context. Past and likely future trends in air pollutant emissions evolve rather differently from those of long-lived greenhouse gases (GHGs), so that superficial extrapolations of GHG trends would lead to misleading conclusions for air pollutant emissions.

In many world regions, the evolution of air pollutant emissions has effectively decoupled from economic growth. Since 1990, air pollutants declined (SO2), stabilized (NOx) or increased slightly (BC, OC and NH3). In the literature, scenarios of future air pollutant emissions span a wide range, mainly due to different assumptions about future environmental policies. While the more recent scenarios agree on declining air pollutants in the next decade, avoiding potential rebounds of emissions in the longer run will require additional policy interventions.

The workshop will review the recent emission scenarios developed for the Task Force on Hemispheric Transport of Air Pollution (HTAP), and compare them with national projections that have been developed in the various world regions. Reasons for differences to global projections will be identified, and assumptions on structural changes, technological improvements and dedicated environmental legislation that lead to these differences will be discussed.  Where available, information on the estimated costs of measures included in the scenarios will be presented and compared.  The workshop will also include a discussion of how global and regional scenarios may be employed in future analyses under the TF HTAP, TFIAM, and other forums to address policy-relevant questions.

Latest HTAP Future Emissions Scenarios

The latest HTAP future emissions scenarios developed by IIASA are available on the HTAP wiki at

Draft recommendations for further work

Presented in Amann, M., Klimont, Z. & Wagner, F., 2013. Regional and Global Emissions of Air Pollutants: Recent Trends and Future Scenarios. Annual Review of Environment and Resources, 38(1), pp.31–55.

  1. A solid understanding of the potential gains from coordinated international action on air pollution would critically benefit from an improved quantification of emissions of specific pollutants (e.g., BC, OC, NH3), source sectors (e.g., international shipping) and world regions (especially fast developing economies). Such activities should be coordinated at the global level.

  2. While there is basic insight into the emissions of energy-related activities, there are large uncertainties in the inventories of nitrogen emissions, especially from agricultural activities. A sharpened focus on ammonia emissions would help to provide a solid knowledge base to counteract the projected steady increase in nitrogen emissions.

  3. As highlighted in the review, air pollutant emissions are critically influenced by the effectiveness of the implementation of dedicated emission control measures. Especially in countries and sectors where institutional arrangements for the enforcement of compliance with existing regulations are only weakly developed, close monitoring of real-life emissions could significantly improve the accuracy of current emission inventories. This applies especially for emissions from mobile sources and industrial activities.

  4. In the future, the development of global emission scenarios must consider the dominating influence of environmental policy decisions about emission controls and address the scope for policy interventions in a more explicit way. This would avoid misleading conclusions about air pollution as a problem that would diminish even in absence of further policy efforts.

  5. Air pollution scenarios should address not only alternative futures for economic development, but also explore alternative institutional and governance regimes. This would widen the range of possible emission developments and highlight the importance of environmental policy interventions.