Abstract. Inventories for global aerosol and aerosol precursor emissions have been collected (based on published inventories and published simulations), assessed and prepared for the year 2000 (present-day conditions) and for the year 1750 (pre-industrial conditions). These global datasets establish a comprehensive source for emission input to global modeling, when simulating the aerosol impact on climate with state-of-the-art aerosol component modules. As these modules stratify aerosol into dust, sea-salt, sulfate, organic matter and soot, for all these aerosol types global fields on emission strength and recommendations for injection altitude and particulate size are provided. Temporal resolution varies between daily (dust and sea-salt), monthly (wild-land fires) and annual (all other emissions). These datasets benchmark aerosol emissions according to the knowledge in the year 2004. They are intended to serve as systematic constraints in sensitivity studies of the AeroCom initiative, which seeks to quantify (actual) uncertainties in aerosol global modeling.

Abstract. A chemistry-transport model (CTM) intercomparison experiment (TransCom-CH4) has been designed to investigate the roles of surface emissions, transport and chemical loss in simulating the global methane distribution. Model simulations were conducted using twelve models and four model variants and results were archived for the period of 1990–2007. All but one model transports were driven by reanalysis products from 3 different meteorological agencies. The transport and removal of CH4 in six different emission scenarios were simulated, with net global emissions of 513 ± 9 and 514 ± 14 Tg CH4 yr−1 for the 1990s and 2000s, respectively. Additionally, sulfur hexafluoride (SF6) was simulated to check the interhemispheric transport, radon (222Rn) to check the subgrid scale transport, and methyl chloroform (CH3CCl3) to check the chemical removal by the tropospheric hydroxyl radical (OH). The results are compared to monthly or annual mean time series of CH4, SF6 and CH3CCl3 measurements from 8 selected background sites, and to satellite observations of CH4 in the upper troposphere and stratosphere. Most models adequately capture the vertical gradients in the stratosphere, the average long-term trends, seasonal cycles, interannual variations (IAVs) and interhemispheric (IH) gradients at the surface sites for SF6, CH3CCl3 and CH4. The vertical gradients of all tracers between the surface and the upper troposphere are consistent within the models, revealing vertical transport differences between models. An average IH exchange time of 1.39 ± 0.18 yr is derived from SF6 time series. Sensitivity simulations suggest that the estimated trends in exchange time, over the period of 1996–2007, are caused by a change of SF6 emissions towards the tropics. Using six sets of emission scenarios, we show that the decadal average CH4 growth rate likely reached equilibrium in the early 2000s due to the flattening of anthropogenic emission growth since the late 1990s. Up to 60% of the IAVs in the observed CH4 concentrations can be explained by accounting for the IAVs in emissions, from biomass burning and wetlands, as well as meteorology in the forward models. The modeled CH4 budget is shown to depend strongly on the troposphere-stratosphere exchange rate and thus on the model's vertical grid structure and circulation in the lower stratosphere. The 15-model median CH4 and CH3CCl3 atmospheric lifetimes are estimated to be 9.99 ± 0.08 and 4.61 ± 0.13 yr, respectively, with little IAV due to transport and temperature.

[1] A synthesis of ground-based measurements and satellite information is described for estimating the amount of monthly averaged biomass burned in year 2000 with a spatial resolution of 1 Â 1 km on a global scale. Emissions of trace gases and aerosols from open biomass burning are estimated from burned areas, fuel load maps, combustion factors, and emission factors. Burned area was quantified by using satellite data in conjunction with a fractional vegetation cover map. To account for spatial heterogeneity in the main types of vegetation within each 1-km grid cell, global fuel load maps have been developed from biomass density data sets for herbaceous and tree-covered land together with global fractional tree and vegetation cover maps. In regions with 40-60% tree cover a relationship between combustion completeness (or combustion factor) in fine fuels and tree cover based on recent field studies is implemented. In regions with <40% tree cover the combustion factor and emissions are related to global satellite-derived data for leaf area index. In regions with >60% tree cover and for coarse fuels in regions with 40-60% tree cover, average values for combustion factors and emission factors from field measurements are used. In addition to biomass burning from open vegetation fires, the emissions from biofuel burning in 2000 are estimated. Our best estimate for the global amount of burned biomass in 2000 is 5613 Tg DM yr À1 , of which 2814 Tg DM yr À1 is associated with open burning and the remainder with biofuels. The total emissions are 2290 Tg C yr À1 (as CO 2 ), 496 Tg CO yr À1 , 32.2 Tg CH 4 yr À1 , 38.0 Tg NHMC yr À1 , 11.5 Tg HCHO yr À1 , 9.2 Tg CH 3 OH yr À1 , 21.7 Tg CH 3 COOH yr À1 , and 38.3 Tg PM 2.5 yr À1 . Our estimates for CO 2 , CO, and CH 4 emissions from open biomass burning combined with estimates of those from biofuel burning are in the range of the estimates constrained by chemical transport models and measurements. Our use of spatially and temporally explicit data and these comparisons to global models support the conclusion that our source map offers improvements in the emission data sets for estimating the global effects of biomass burning.