Future impact of traffic emissions on atmospheric ozone and OH based on two scenarios

Abstract

Abstract. The future impact of traffic emissions on atmospheric ozone and OH has been investigated separately for the three sectors AIRcraft, maritime SHIPping and ROAD traffic. To reduce uncertainties we present results from an ensemble of six different atmospheric chemistry models, each simulating the atmospheric chemical composition in a possible high emission scenario (A1B), and with emissions from each transport sector reduced by 5 % to estimate sensitivities. Our results are compared with optimistic future emission scenarios (B1 and B1 ACARE), presented in a companion paper, and with the recent past (year 2000). Present-day activity indicates that anthropogenic emissions so far evolve closer to A1B than the B1 scenario.As a response to expected changes in emissions, AIR and SHIP will have increased impacts on atmospheric O 3 and OH in the future while the impact of ROAD traffic will decrease substantially as a result of technological improvements. In 2050, maximum aircraft-induced O 3 occurs near 80 • N in the UTLS region and could reach 9 ppbv in the zonal mean during summer. Emissions from ship traffic have their largest O 3 impact in the maritime boundary layer with a maximum of 6 ppbv over the North Atlantic Ocean during summer in 2050. The O 3 impact of road traffic emissions in the lower troposphere peaks at 3 ppbv over the Arabian Peninsula, much lower than the impact in 2000.Radiative forcing (RF) calculations show that the net effect of AIR, SHIP and ROAD combined will change from a marginal cooling of −0.44 ± 13 mW m −2 in 2000 to a relatively strong cooling of −32 ± 9.3 (B1) or −32 ± 18 mW m −2 (A1B) in 2050, when taking into account RF due to changes in O 3 , CH 4 and CH 4 -induced O 3 . This is caused both by the enhanced negative net RF from SHIP, which will change from −19 ± 5.3 mW m −2 in 2000 to −31 ± 4.8 (B1) or −40 ± 9 mW m −2 (A1B) in 2050, and from reduced O 3 warming from ROAD, which is likely to turn from a positive net RF of 12 ± 8.5 mW m −2 in 2000 to a slightly negative net RF of −3.1 ± 2.2 (B1) or −3.1 ± 3.4 (A1B) mW m −2 in the middle of this century. The negative net RF from ROAD is temporary and induced by the strong decline in ROAD emissions prior to 2050, which only affects the methane cooling term due to the longer lifetime of CH 4 compared to O 3 . The O 3 RF from AIR in 2050 is Published by Copernicus Publications on behalf of the European Geosciences Union. Ø. Hodnebrog et al.: Future impact of traffic emissionsstrongly dependent on scenario and ranges from 19 ± 6.8 (B1 ACARE) to 61 ± 14 mW m −2 (A1B). There is also a considerable span in the net RF from AIR in 2050, ranging from -0.54 ± 4.6 (B1 ACARE) to 12 ± 11 (A1B) mW m −2 compared to 6.6 ± 2.2 mW m −2 in 2000.

Modeling the present and future impact of aviation on climate: an AOGCM approach with online coupled chemistry

“…This is in agreement with our computations of the quantity of ozone production resulting from these emissions, which is smaller than in previous studies (e.g., Grewe et al, 2002a;Isaksen, 2003;Gauss et al, 2006;Köhler et al, 2008;Cariolle et al, 2009;Hoor et al, 2009;Koffi et al, 2010;Hodnebrog et al, 2012). These studies report zonal ozone increases in the UTLS from 2 to 3 ppvb in Cariolle et al (2009);Olivié et al (2012) to over Thin lines indicate the annual impact of each of the three members of a simulation, and the thick lines indicate the 11-yr running average of the ensemble mean.…”

“…For stratospheric chemistry studies, the number of vertical levels has been increased to 60 (up to 0.07 hPa), 24 of which are in the stratosphere. This represents an improvement with regard to previous studies, especially those that focused on the chemical perturbation caused by aviation emissions (e.g., Hoor et al, 2009;Koffi et al, 2010;Hodnebrog et al, 2012).…”

The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018

“…This change shows that background emissions modify the CH 4 correction factor and further emphasizes the need to have surface and aircraft emissions that simultaneously follow historical pathways. In other studies using the G&S methodology, CH 4 correction factors vary from 0.74 to 1.15 depending on the investigated year (2025 or 2050) and aircraft emission scenario (SRES A1B, B1 and B1 ACARE) (the factor can be larger than 1 if the aircraft emissions are assumed to decrease in the preceding years) ( Hodnebrog et al, 2011 , 2012 ).…”

The global impact of the transport sectors on atmospheric aerosol: simulations for year 2000 emissions

“…The global impact of the transport sectors on atmosphere and climate has been analyzed in several previous publications, e.g., in the ATTICA assessment reports (Sausen, 2010;Fuglestvedt et al, 2010;Lee et al, 2010;Eyring et al, 2010;Uherek et al, 2010). Studies consistently comparing the effects of land-based transport, shipping, and aviation mainly focused on atmospheric gas-phase chemistry, particularly of ozone (Hoor et al, 2009;Koffi et al, 2010;Hodnebrog et al, 2012) or on the RF and climate impacts (Fuglestvedt et al, 2008;Skeie et al, 2009;Balkanski et al, 2010;Myhre et al, 2011;Bauer and Menon, 2012;Olivié et al, 2012). A corresponding analysis on the details of transport-induced global perturbations of specific aerosol compounds, aerosol particle number concentration and size distribution is desirable.…”