Abstract. The global methane (CH4) budget is becoming an increasingly important component for managing realistic pathways to mitigate climate change. This relevance, due to a shorter atmospheric lifetime and a stronger warming potential than carbon dioxide, is challenged by the still unexplained changes of atmospheric CH4 over the past decade. Emissions and concentrations of CH4 are continuing to increase making CH4 the second most important human-induced greenhouse gas after carbon dioxide. Two major difficulties in reducing uncertainties come from the large variety of diffusive CH4 sources that overlap geographically, and from the destruction of CH4 by the very short-lived hydroxyl radical (OH). To address these difficulties, we have established a consortium of multi-disciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate research on the methane cycle, and producing regular (~biennial) updates of the global methane budget. This consortium includes atmospheric physicists and chemists, biogeochemists of surface and marine emissions, and socio-economists who study anthropogenic emissions. Following Kirschke et al. (2013), we propose here the first version of a living review paper that integrates results of top-down studies (T-D, exploiting atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up models, inventories, and data-driven approaches (B-U, including process-based models for estimating land surface emissions and atmospheric chemistry, and inventories for anthropogenic emissions, data-driven extrapolations). For the 2003–2012 decade, global methane emissions are estimated by T-D inversions at 558 Tg CH4 yr−1 (range [540–568]). About 60 % of global emissions are anthropogenic (range [50–65 %]). B-U approaches suggest larger global emissions (736 Tg CH4 yr−1 [596–884]) mostly because of larger natural emissions from individual sources such as inland waters, natural wetlands and geological sources. Considering the atmospheric constraints on the T-D budget, it is likely that some of the individual emissions reported by the B-U approaches are overestimated, leading to too large global emissions. Latitudinal data from T-D emissions indicate a predominance of tropical emissions (~64 % of the global budget,

Radiance measurements made by the Advanced Very High Resolution Radiometer (AVHRR) at 1-km (nadir) spatial resolution were used to retrieve cloud optical depth () and cloud droplet effective radius (r eff ) for 31 marine boundary layer clouds over the eastern Pacific Ocean and the Southern Ocean near Tasmania.In the majority of these scenes (each roughly 256 ϫ 256 km 2 in extent) and r eff are strongly correlated, with linear least squares yielding a regression curve of the form r eff ϰ 1/5 . This relationship is consistent with an idealized model of a nonprecipitating layer cloud in which 1) the average cloud liquid water content increases linearly with height at some fraction of the adiabatic lapse rate in a 1 km 2 vertical column, and 2) the normalized horizontal variability of the cloud liquid water path exceeds the variability of a scaled measure of the cloud droplet number concentration. In contrast, other scenes of similar horizontal extent show little or no correlation between retrieved values of and r eff . These scenes include thicker clouds in which precipitation may be occurring, as well as cloud layers with spatially distinct regions of varying r eff .In situ aircraft measurements were made simultaneously with six AVHRR overpasses as part of the Southern Ocean Cloud Experiment. The clouds sampled by these flights were significantly thicker than the typically 200m-thick eastern Pacific stratocumulus, with large vertical and horizontal variability. On five of the six flights, aircraft measurements of the cloud-top effective radius were well matched by the satellite retrievals, and in two of these layers r eff ϰ 1/5 .

An update of in situ Advanced Global Atmospheric Gases Experiment (AGAGE) hydrofluorocarbon (HFC)/hydrochlorofluorocarbon (HCFC) measurements made at Mace Head, Ireland, and Cape Grim, Tasmania, from 1998 to 2002 are reported. HCFC‐142b, HCFC‐141b, HCFC‐22 and HFC‐134a show continued rapid growth in the atmosphere at mean rates of 1.1, 1.6, 6.0, and 3.4 ppt/year, respectively. Emissions inferred from measurements are compared to recent estimates from consumption data. Minor updates to the industry estimates of emissions are reported together with a discussion of how to best determine OH concentrations from these trace gas measurements. In addition, AGAGE measurements and derived emissions are compared to those deduced from NOAA‐Climate Monitoring and Diagnostics Laboratory flask measurements (which are mostly made at different locations). European emission estimates obtained from Mace Head pollution events using the Nuclear Accident Model (NAME) dispersion model and the best fit algorithm (known as simulated annealing) are presented as 3‐year rolling average emissions over Europe for the period 1999–2001. Finally, the measurements of HCFC‐141b, HCFC‐142b, and HCFC‐22 discussed in this paper have been combined with the Atmospheric Lifetime Experiment (ALE)/Global Atmospheric Gases Experiment (GAGE)/AGAGE measurements of CFC‐11, CFC‐12, CFC‐113, CCl4, and CH3CCl3 to produce the evolution of tropospheric chlorine loading.

Abstract.In Observations during the second and third flights indicate that aerosol particles of this size were mixing downward into the boundary layer from the buffer layer while DMS was transported upward. This fortuitous enhancement of aerosol particles in the buffer layer allowed simultaneous use of DMS and aerosol particle budgets to track the bidirectional entrainment rates. These estimates were compared to those from measurements of mean vertical motion and boundary layer growth rate, and from estimates of the fluxes and changes in concentration across the layer interface. In addition, three different techniques were used to estimate DMS emission rates from the ocean surface and showed good agreement: (1) evalulation of the DMS and aerosol mean concentration budgets, (2) seawater DMS concentrations and an air-sea exchange velocity, and (3) the mixed-layer gradient technique.