ALBERT

Description: To estimate the impact of emissions by road, aircraft and ship traffic on ozone and OH of the present-day atmosphere seven different atmospheric chemistry models simulated the atmospheric composition of the year 2003. Based on newly developed global emission inventories for road, maritime and aircraft emission data sets each model performed a series of five simulations: A base scenario using the full set of emissions, three sensitivity studies with each individual sector of transport reduced by 5% and one simulation with all traffic related emissions reduced by 5%. The approach minimizes non-linearities in atmospheric chemical effects and are later scaled to 100%. The global annual mean impact of ship emissions on ozone in the boundary layer leads to an increase of ozone of 1.2%, followed by road (0.87%) and aircraft emissions (0.3%). In the upper troposphere between 200–300 hPa both road and ship traffic affect ozone by 1.1%, whereas aircraft emissions contribute 0.9%. However, the sensitivity of ozone formation per NOx molecule emitted is highest for aircraft exhausts. The local maximum effect of the summed traffic emissions on the ozone column predicted by the models is 4.0 DU and occurs over the northern subtropical Atlantic. The impact of traffic emissions on total ozone in the Southern Hemisphere is approximately half of the northern hemispheric perturbation. Below 800 hPa both ozone and OH respond most sensitively to ship emissions in the marine boundary layer over the Atlantic, where the effect can exceed 10% (zonal mean) which is 80% of the total traffic induced ozone perturbation. In the Southern Hemisphere ship emissions contribute relatively strongly to the total ozone perturbation by 60%–80% throughout the year (equivalent to 1–1.5 ppbv). Road emissions have the strongest impact on ozone in the continental boundary layer and the free troposphere in summer. They also affect the upper troposphere particularly during northern summer associated with strong convection in mid latitudes. Ozone perturbations due to road traffic show the strongest seasonal cycle in the northern troposphere, and can even change sign in the continental boundary layer during winter. The OH concentration in the boundary layer is most strongly affected by ship emissions, which has a significant influence on the lifetime of many trace gases including methane. Methane lifetime changes due to ship emissions amount to 4.1%, followed by road (1.6%) and air traffic (1.0%).

Description: 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 −2.05 W/m2. In the future this negative global annual mean aerosol radiative forcing will only slightly change (+0.02 W/m2) under the "current legislation" scenario. Regionally, the effects are much larger: e.g. over Eastern Europe radiative forcing would increase by +1.50 W/m2 because of successful aerosol reduction policies, whereas over South Asia it would decrease by −1.10 W/m2 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/m2. Hence, in the latter case, the present day negative anthropogenic aerosol forcing cloud be more than halved by 2030 because of aerosol reduction policies and climate change thereafter will be to a larger extend 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 in the future within a realistic range, we do not find a significant effect for the global annual mean radiative aerosol forcing. In the extreme case of only abating SO2 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.

Description: During the Mediterranean Intensive Oxidant Study MINOS in August 2001, 87 air samples were collected at the ground-based station Finokalia (35°19'N, 25°40'E) on the north coast of Crete and subsequently analysed by GC-MS. The analysis includes various hydrocarbons, organo-halogens, HCFCs and CFCs. These compounds have a wide variety of sources and sinks and a large range of atmospheric lifetimes. We evaluated the characteristics of the sampling site in terms of proximity to individual sources by plotting the measured variability of these species against lifetime. The resulting linear relationship suggests that the sampling site is representative of intermediate conditions between a remote site and one that is in the vicinity of a wide variety of sources. Our analysis of air mass origin and chemical ratios also shows that several distinct anthropogenic sources influenced the atmospheric composition over Crete. Propane observations are compared to a global model to assess the fossil fuel related emission inventory. Although the model reproduces the general pattern of the propane variations, the model mixing ratios are systematically too low by a factor of 1.5 to 3, probably due to an underestimation of the propane emissions from east European countries in the underlying global database EDGAR. Another important finding was that methyl chloroform, a compound banned under the Montreal protocol, showed significant enhancements from background, which were well correlated with CFC-113. This suggests continued use and emission of methyl chloroform by one or more European countries. We also discuss the observed variations of methyl bromide and suggest that the significant peak observed on 12 August 2001 reflects heavy agricultural use as a soil fumigant in Italy.

Description: The atmospheric chemistry general circulation model EMAC has been used to estimate the impact of anthropogenic emission changes on global and regional air quality in recent and future years (2005, 2010, 2025 and 2050). The emission scenario assumes that population and economic growth largely determine energy and food consumption and consequent pollution sources with the current technologies ("business as usual"). This scenario is chosen to show the effects of not implementing legislation to prevent additional climate change and growing air pollution, other than what is in place for the base year 2005, representing a pessimistic (but plausible) future. By comparing with recent observations, it is shown that the model reproduces the main features of regional air pollution distributions though with some imprecisions inherent to the coarse horizontal resolution (~100 km) and simplified bottom-up emission input. To identify possible future hot spots of poor air quality, a multi pollutant index (MPI), suited for global model output, has been applied. It appears that East and South Asia and the Middle East represent such hotspots due to very high pollutant concentrations, while a general increase of MPIs is observed in all populated regions in the Northern Hemisphere. In East Asia a range of pollutant gases and fine particulate matter (PM2.5) is projected to reach very high levels from 2005 onward, while in South Asia air pollution, including ozone, will grow rapidly towards the middle of the century. Around the Persian Gulf, where natural PM2.5 concentrations are already high (desert dust), ozone levels are expected to increase strongly. The population weighted MPI (PW-MPI), which combines demographic and pollutant concentration projections, shows that a rapidly increasing number of people worldwide will experience reduced air quality during the first half of the 21st century. Following this business as usual scenario, it is projected that air quality for the global average citizen in 2050 would be almost comparable to that for the average citizen in East Asia in the year 2005, which underscores the need to pursue emission reductions.

Description: The importance of emission inventory uncertainty on the simulation of summertime tropospheric ozone over China has been analyzed using a regional chemical transport model. Three independent emissions inventories, that are (i) emission estimates from the Emission Database for Global Atmospheric Research (EDGAR) for the year 1995, (ii) a regional emission inventory used in the Transport and Chemical Evolution over the Pacific (TRACE-P) program with emissions for the year 2000 and (iii) a national emission inventory used in the China Ozone Research Program (CORP) with emission estimates for the year 1995, are used for model simulation over a summer period. Methods used for the development of the inventories are discussed and differences in simulated ozone and its precursors with these emission inventories are analyzed. Comparison of the emission inventories revealed large differences in the emission estimates (up to 50% for NOx, ~100% for NMVOC and ~1000% for CO). Application of the different emission inventories in three model simulations showed minor differences in both surface O3 in rather unpolluted areas in China and at higher altitudes (500mbar). In polluted areas, differences in surface O3 are 30-50% between the different model simulations which seem rather small taking into account the large differences in the emission inventories. Additional sensitivity runs showed that the difference in NOx emissions as well NMVOC emissions is a dominant factor which controls the differences in simulated O3 concentrations while the impact of differences in CO emissions is relatively small. Although the CO emission estimate by CORP seems to be underestimated, there is no confidence to highlight one emission inventory better than the others.

Description: To estimate the impact of emissions by road, aircraft and ship traffic on ozone and OH in the present-day atmosphere six different atmospheric chemistry models have been used. Based on newly developed global emission inventories for road, ship and aircraft emission data sets each model performed sensitivity simulations reducing the emissions of each transport sector by 5%. The model results indicate that on global annual average lower tropospheric ozone responds most sensitive to ship emissions (50.6%±10.9% of the total traffic induced perturbation), followed by road (36.7%±9.3%) and aircraft exhausts (12.7%±2.9%), respectively. In the northern upper troposphere between 200–300 hPa at 30–60° N the maximum impact from road and ship are 93% and 73% of the maximum effect of aircraft, respectively. The latter is 0.185 ppbv for ozone (for the 5% case) or 3.69 ppbv when scaling to 100%. On the global average the impact of road even dominates in the UTLS-region. The sensitivity of ozone formation per NOx molecule emitted is highest for aircraft exhausts. The local maximum effect of the summed traffic emissions on the ozone column predicted by the models is 0.2 DU and occurs over the northern subtropical Atlantic extending to central Europe. Below 800 hPa both ozone and OH respond most sensitively to ship emissions in the marine lower troposphere over the Atlantic. Based on the 5% perturbation the effect on ozone can exceed 0.6% close to the marine surface (global zonal mean) which is 80% of the total traffic induced ozone perturbation. In the southern hemisphere ship emissions contribute relatively strongly to the total ozone perturbation by 60%–80% throughout the year. Methane lifetime changes against OH are affected strongest by ship emissions up to 0.21 (± 0.05)%, followed by road (0.08 (±0.01)%) and air traffic (0.05 (± 0.02)%). Based on the full scale ozone and methane perturbations positive radiative forcings were calculated for road emissions (7.3±6.2 mWm−2) and for aviation (2.9±2.3 mWm−2). Ship induced methane lifetime changes dominate over the ozone forcing and therefore lead to a net negative forcing (−25.5±13.2 mWm−2).

Description: The atmospheric chemistry general circulation model EMAC (ECHAM5/MESSy atmospheric chemistry) is used to investigate the effect of height dependent emissions on tropospheric chemistry. In a sensitivity simulation, anthropogenic and biomass burning emissions are released in the lowest model layer. The resulting tracer distributions are compared to those of a former simulation applying height dependent emissions. Although the differences between the two simulations in the free troposphere are small (less than 5%), large differences are present in polluted regions at the surface, in particular for NOx (more than 100%), CO (up to 30%) and non-methane hydrocarbons (up to 30%), whereas for OH the differences at the same locations are somewhat lower (15%). Global ozone formation is virtually unaffected by the choice of the vertical distribution of emissions. Nevertheless, local ozone changes can be up to 30%. Model results of both simulations are further compared to observations from field campaigns and to data from measurement stations.

Description: Sulfur aerosols impact human health, ecosystems, agriculture, and global and regional climate. A new annual estimate of anthropogenic global and regional sulfur dioxide emissions has been constructed spanning the period 1850–2005 using a bottom-up mass balance method, calibrated to country-level inventory data. Global emissions peaked in the early 1970s and decreased until 2000, with an increase in recent years due to increased emissions in China, international shipping, and developing countries in general. An uncertainty analysis was conducted including both random and systemic uncertainties. The overall global uncertainty in sulfur dioxide emissions is relatively small, but regional uncertainties ranged up to 30%. The largest contributors to uncertainty at present are emissions from China and international shipping. Emissions were distributed on a 0.5° grid by sector for use in coordinated climate model experiments.