Influence of future air pollution mitigation strategies on total aerosol radiative forcing

We apply different aerosol and aerosol precursor emission scenarios reflecting possible future control strategies for air pollution in the ECHAM5-HAM model, and simulate the resulting effect on the Earth's radiation budget. We use two opposing future mitigation strategies for the year 2030: one in which emission reduction legislation decided in countries throughout the world are effectively implemented (current legislation; CLE 2030) and one in which all technical options for emission reductions are being implemented independent of their cost (maximum feasible reduction; MFR 2030). We consider the direct, semi-direct and indirect radiative effects of aerosols. The total anthropogenic aerosol radiative forcing defined as the difference in the top-of-the-atmosphere radiation between 2000 and pre-industrial times amounts to −2.00 W/m 2 . In the future this negative global annual mean aerosol radiative forcing will only slightly change (+0.02 W/m 2 ) under the "current legislation" scenario. Regionally, the effects are much larger: e.g. over Eastern Europe radiative forcing would increase by +1.50 W/m 2 because of successful aerosol reduction policies, whereas over South Asia it would decrease by −1.10 W/m 2 because of further growth of emissions. A "maximum feasible reduction" of aerosols and their precursors would lead to an increase of the global annual mean aerosol radiative forcing by +1.13 W/m 2 . Hence, in the latter case, the present day negative anthropogenic aerosol forcing could be more than halved by 2030 because of aerosol reduction policies and climate change thereafter will be to a larger extent be controlled by greenhouse gas emissions. We combined these two opposing future mitigation strategies for a number of experiments focusing on different sectors and regions. In addition, we performed sensitivity studies to estimate the importance of future changes in oxidant concentrations and the importance of the aerosol microphysical coupling within the range of expected future changes. For changes in oxidant concentrations caused by future air pollution mitigation, we do not find a significant effect for the global annual mean radiative aerosol forcing. In the extreme case of only abating SO 2 or carbonaceous emissions to a maximum feasible extent, we find deviations from additivity for the radiative forcing over anthropogenic source regions up to 10% compared to an experiment abating both at the same time.

[1]  E. Roeckner,et al.  The evolution of the global aerosol system in a transient climate simulation from 1860 to 2100 , 2005 .

[2]  R. Dickinson,et al.  Couplings between changes in the climate system and biogeochemistry , 2007 .

[3]  P. Bergamaschi,et al.  European Geosciences Union Atmospheric Chemistry , 2004 .

[4]  J. Penner,et al.  Correction to “Prediction of the number of cloud droplets in the ECHAM GCM” by Ulrike Lohmann et al. , 1999 .

[5]  M. Andreae.  Atmospheric aerosols versus greenhouse gases in the twenty-first century , 2007, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[6]  S. Twomey.  The Influence of Pollution on the Shortwave Albedo of Clouds , 1977 .

[7]  M. Heimann,et al.  Impact of vegetation and preferential source areas on global dust aerosol: Results from a model study , 2002 .

[8]  Jean-Francois Lamarque,et al.  Sea-salt aerosol response to climate change: Last Glacial Maximum, preindustrial, and doubled carbon dioxide climates , 2006 .

[9]  K. Riahi,et al.  Greenhouse Gas Emissions in a Dynamics-as-Usual Scenario of Economic and Energy Development , 2000 .

[10]  M. Tiedtke.  A Comprehensive Mass Flux Scheme for Cumulus Parameterization in Large-Scale Models , 1989 .

[11]  P. Forster,et al.  Impact of an improved shortwave radiation scheme in the MAECHAM5 General Circulation Model , 2007 .

[12]  D. Koch,et al.  Linking future aerosol radiative forcing to shifts in source activities , 2007 .

[13]  Stefan Reis,et al.  Twenty-five years of continuous sulphur dioxide emission reduction in Europe , 2007 .

[14]  A. Watson,et al.  In situ evaluation of air‐sea gas exchange parameterizations using novel conservative and volatile tracers , 2000 .

[15]  R. Betts,et al.  Changes in Atmospheric Constituents and in Radiative Forcing. Chapter 2 , 2007 .

[16]  D. Koch,et al.  Cross influences of ozone and sulfate precursor emissions changes on air quality and climate. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[17]  O. Boucher,et al.  The aerosol-climate model ECHAM5-HAM , 2004 .

[18]  D. Koch,et al.  Air Pollution Radiative Forcing From Specific Emissions Sectors at 2030: Prototype for a New IPCC Bar Chart , 2007 .

[19]  D. Streets,et al.  A technology‐based global inventory of black and organic carbon emissions from combustion , 2004 .

[20]  N. Mahowald,et al.  Change in atmospheric mineral aerosols in response to climate: Last glacial period, preindustrial, modern, and doubled carbon dioxide climates , 2006 .

[21]  U. Lohmann,et al.  Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM , 2007 .

[22]  A. Sterl,et al.  The ERA‐40 re‐analysis , 2005 .

[23]  D. Hauglustaine,et al.  Changes in atmospheric sulfur burdens and concentrations and resulting radiative forcings under IPCC SRES emission scenarios for 1990–2100 , 2005 .

[24]  B. Holben,et al.  Single-Scattering Albedo and Radiative Forcing of Various Aerosol Species with a Global Three-Dimensional Model , 2002 .

[25]  J. Seinfeld,et al.  Impact of nonabsorbing anthropogenic aerosols on clear‐sky atmospheric absorption , 2006 .

[26]  G. Brasseur,et al.  Impact of improved air quality on the future evolution of climate , 2005 .

[27]  G. Müller,et al.  The Scientific Basis , 1995 .

[28]  Kaarle Kupiainen,et al.  Scenarios of global anthropogenic emissions of air pollutants and methane until 2030 , 2007 .

[29]  J. Hansen,et al.  Radiative forcing and climate response , 1997 .

[30]  J. Wilson,et al.  Emission-Induced Nonlinearities in the Global Aerosol System: Results from the ECHAM5-HAM Aerosol-Climate Model , 2006 .

[31]  B. Albrecht.  Aerosols, Cloud Microphysics, and Fractional Cloudiness , 1989, Science.

[32]  D. Shindell.  Climate response to projected changes in short-lived species under an A1B scenario from 2000-2050 in the GISS climate model , 2007 .

[33]  J. Houghton,et al.  Climate change 2001 : the scientific basis , 2001 .

[34]  Alexei G. Sankovski,et al.  Special report on emissions scenarios , 2000 .

[35]  Johann Feichter,et al.  Simulation of the tropospheric sulfur cycle in a global climate model , 1996 .

[36]  Michael Schulz,et al.  Sea-salt aerosol source functions and emissions , 2004 .

[37]  U. Lohmann,et al.  Nonlinear Aspects of the Climate Response to Greenhouse Gas and Aerosol Forcing , 2004 .

[38]  A. Kettle,et al.  Flux of dimethylsulfide from the oceans: A comparison of updated data sets and flux models , 2000 .

[39]  O. Boucher,et al.  Aerosol optical depths and direct radiative perturbations by species and source type , 2005 .

[40]  Thomas de Quincey.  [C] , 2000, The Works of Thomas De Quincey, Vol. 1: Writings, 1799–1820.

[41]  Shian‐Jiann Lin,et al.  Multidimensional Flux-Form Semi-Lagrangian Transport Schemes , 1996 .

[42]  J. Feichter,et al.  Volcanic sulfur emissions: Estimates of source strength and its contribution to the global sulfate distribution , 1997 .

[43]  P. J. Rasch,et al.  Sulfur chemistry in the National Center for Atmospheric Research Community Climate Model: Description, evaluation, features, and sensitivity to aqueous chemistry , 2000 .

[44]  I. Tegen,et al.  Relative importance of climate and land use in determining present and future global soil dust emission , 2004 .

[45]  Tami C. Bond,et al.  Emissions of primary aerosol and precursor gases in the years 2000 and 1750 prescribed data-sets for AeroCom , 2006 .

[46]  J.G.J. Olivier,et al.  Global emission sources and sinks , 2001 .

[47]  J. Wilson,et al.  M7: An efficient size‐resolved aerosol microphysics module for large‐scale aerosol transport models , 2004 .

[48]  E. Maier‐Reimer,et al.  Response of dimethylsulfide (DMS) in the ocean and atmosphere to global warming , 2007 .

[49]  Tami C. Bond,et al.  On the future of carbonaceous aerosol emissions , 2004 .

[50]  J. Kristjánsson,et al.  Condensation and Cloud Parameterization Studies with a Mesoscale Numerical Weather Prediction Model , 1989 .

[51]  U. Lohmann,et al.  Impact of sulfate aerosols on albedo and lifetime of clouds: A sensitivity study with the ECHAM4 GCM , 1997 .

[52]  D. Koch,et al.  Global impacts of aerosols from particular source regions and sectors , 2007 .

[53]  Lennart Bengtsson,et al.  On the potential of assimilating meteorological analyses in a global climate model for the purpose of model validation , 1996 .

[54]  J. Lamarque,et al.  A global simulation of tropospheric ozone and related tracers: Description and evaluation of MOZART, version 2 , 2001 .

[55]  M. Khairoutdinov,et al.  A New Cloud Physics Parameterization in a Large-Eddy Simulation Model of Marine Stratocumulus , 2000 .

[56]  V. Eyring,et al.  Emissions from international shipping: 2. Impact of future technologies on scenarios until 2050 , 2005 .

[57]  D Hauglustaine,et al.  The global atmospheric environment for the next generation. , 2006, Environmental science & technology.

[58]  J. Lelieveld,et al.  Interannual variability and trend of CH4 lifetime as a measure for OH changes in the 1979–1993 time period , 2003 .

[59]  Jean-Francois Lamarque,et al.  Multimodel projections of climate change from short‐lived emissions due to human activities , 2008 .

[60]  M. Schultz,et al.  Trace gas and aerosol interactions in the fully coupled model of aerosol-chemistry-climate ECHAM5-HAMMOZ: 1. Model description and insights from the spring 2001 TRACE-P experiment , 2008 .

[61]  J. Lelieveld,et al.  Simulation of global sulfate distribution and the influence on effective cloud drop radii with a coupled photochemistry sulfur cycle model , 1998 .

[62]  David G. Streets,et al.  Aerosol climate effects and air quality impacts from 1980 to 2030 , 2008 .