The influence of ozone precursor emissions from four world regions on tropospheric composition and radiative climate forcing

Ozone (O3) precursor emissions influence regional and global climate and air quality through changes in tropospheric O3 and oxidants, which also influence methane (CH4) and sulfate aerosols (SO42-). We examine changes in tropospheric composition of O3, CH4, SO42- and global net radiative forcing (RF) for 20% reductions in global CH4 burden and anthropogenic O3 precursor emissions (NOx, NMVOC, and CO) from four regions (East Asia, Europe and Northern Africa, North America, and South Asia) using the Task Force on Hemispheric Transport of Air Pollution Source-Receptor global chemical transport model (CTM) simulations, assessing uncertainty (mean±1 standard deviation) across multiple CTMs. We evaluate steady-state O3 responses, including long-term feedbacks via CH4. With a radiative transfer model that includes greenhouse gases and the aerosol direct effect, we find that regional NOx reductions produce global, annually averaged positive net RFs (0.2±0.6 to 1.7±2 mWm-2/TgN yr-1). Negative net RFs result from reductions in global CH4 (-162.6±2 mWm-2) and regional NMVOC (-0.4±0.2 to -0.7±0.2 mWm-2/TgC yr-1) and CO emissions (-0.13±0.02 to -0.15±0.02 mWm-2/TgCO yr-1). Including the effect of O3 on CO2 via plant growth likely makes these RFs more negative. Net RF impacts extend beyond the reduction region, reflecting concentration changes, where changes in SO42- affect RF locally, O3 regionally to hemispherically, and CH4 globally. The range in SO42- response to oxidant changes across CTMs suggests additional research is needed. The 100-year global warming potentials (GWP100) are 20.9±3.7 for CH4, and across the four reduction regions: -18.7±25.9 to -1.9±8.7 for NOx, 4.8±1.7 to 8.3±1.9 for NMVOC, and 1.5±0.4 to 1.7±0.5 for CO. Global net RF and GWP100 are more sensitive to NOx and NMVOC reductions from South Asia than the other three regions. Regionally-specific GWPs may support the inclusion of O3 precursors in future policies that address air quality and climate change simultaneously.

FRY Meredith;  NAIK Vaishali;  WEST Jason;  SCHWARZKOPF Daniel;  FIORE A. M.;  COLLINS W. J.;  DENTENER Franciscus;  SHINDELL D. T.;  ATHERTON C. S.;  BERGMANN D. J.;  DUNCAN B. N.;  HESS Peter;  MACKENZIE I. A.;  MARMER Elina;  SCHULTZ M.G.;  SZOPA S.;  WILD Oliver;  ZENG Guang; 

2012-07-11

AMER GEOPHYSICAL UNION

JRC67561

0148-0227,   

http://www.agu.org/pubs/crossref/2012/2011JD017134.shtml,    https://publications.jrc.ec.europa.eu/repository/handle/JRC67561,   

10.1029/2011JD017134,