Air Pollution emission scenarios: RCP4.5

IPCC scenario: RCP4.5

Main assumptions (global)

  • Stabilized radiative forcing at 4.5 W m-2 (approx. 650 ppm CO2-equivalents).
  • Prizing of emissions of greenhouse gases enforced to reduce emissions.
  • Bioenergy production with CO2 capture and geologic storage (net negative CO2 emissions) implemented. Area of forests and dedicated bioenergy crops increased to meet global energy demand.
  • Electric power generation changes from the largest source of emissions to a system with net negative emissions.
  • Increased reliance on nuclear and renewable energy forms such as wind, solar and geothermal.
  • A global population that reaches ~9 billion in 2070 and then gradually declines.


Thomson, A.M., Calvin, K.V., Smith, S.J., Kyle, G.P., Volke, A., Patel, P., Delgado-Arias, S., Bond-Lamberty, B., Wise, M.A., Clarke, L.E. and Edmonds, J.A. 2011. RCP4.5: a pathway for stabilization of radiative forcing by 2100. Climatic Change 109, 77–94. doi:10.1007/s10584--011--0151--4.

Air pollutant emissions in Europe

While emissions of SO2, NOx and CO will decrease significantly in Europe over the coming decades in the RCP4.5 scenario, NH3 and NMVOC are not expected to decrease to the same extent, see Figure 1. For NH3 several European countries are projected to increase their emissions from current levels (not shown).

The RCP scenarios were mainly developed for climate modelling purposes and it has been argued that future air pollutant emissions differ only little among the different RCP scenarios. Figure 1 includes a comparison of the air pollutant emissions in RCP4.5 and RCP2.6 in Europe for a number of key species.

The air pollutant emissions in RCP4.5 have not explicitly considered current European legislation and possible reductions in air pollutant emissions, following various air quality directives to mitigate acidification, eutrophication, and damages to human health. In Figure 2 we compare the RCP4.5 emissions for selected species in the EU-27 countries with recent air pollutant emissions developed for Europe in connection with the revision of the EU Thematic Strategy for Air Pollution. Note that the RCP4.5 data are similar to the Base scenario (current legislation) and that differences between dedicated air pollutant emission scenarios are of the same magnitude as differences between different RCP scenarios.


Amann, M., Borken‐Kleefeld, J., Cofala, J., Heyes, C., Klimont, Z., Rafaj, P., Purohit, P., Schöpp W. and Winiwarter, W. 2012. Future emissions of air pollutants in Europe – Current legislation baseline and the scope for further reductions. TSAP Report #1, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.

Langner, J., Klein, T. and Bergström, R. 2010. Air pollutant emission scenarios for CLEO. Project 1.3. SMHI, Report 1–2010-12-15.

Engardt, M. and Langner, J. 2013. Simulations of future sulphur and nitrogen deposition over Europe using meteorological data from three regional climate projections. Manuscript.

SUDPLAN emission scenarios: 1_e
Figure 1 Temporal evolution of emissions of SO2, NOx, NH3, NMVOC, and CO in a domain roughly encompassing Europe (10ºW, 50ºE, 30ºS, 75ºN) in RCP 2.6 (RCP3) and RCP 4.5. Enlarge Image
SUDPLAN emission scenarios: 2_c
Figure 2 Annual anthropogenic emissions in EU-27 of SO2, NOx and NH3 from RCP4.5 and four different scenarios developed by Amann et al. (2012). Base corresponds to implementation of current legislation. Decarb correspond to an 80% reduction in greenhouse gas emissions in 2050 and concurrent reductions in sulphur and nitrogen emission. MTFR corresponds to Maximum Technically Feasible Reduction and MCE corresponds to Maximum Control Efforts. Units: Gg (SO2, NO2 or NH3) yr-1. Enlarge Image