Abstract. As part of the work of the Economic Commission for Europe of the United Nations Task Force on Emission Inventories, a new set of guidelines has been developed for assessing the emissions of sulphur, nitrogen oxides, NH 3, CH4, and nonmethane volatile organic compounds (NMVOC) from biogenic and other natural sources in Europe. This paper gives the background to these guidelines, describes the sources, and gives our recommended methodologies for estimating emissions. We have assembled land use and other statistics from European or national compilations and present emission estimates for the various natural/biogenic source categories based on these.

[1] Recent studies indicate that plants may be a previously overlooked but significant source of atmospheric CH 4 , though there is considerable disagreement on the mechanism of production. Our work sought to verify that woody deciduous trees grown under inundated conditions had the capacity for transporting CH 4 from an anaerobic subsurface to the atmosphere and to consider if such a source could be important globally. Here, we report results from a greenhouse mesocosm study that indicate significant emissions of anaerobically produced CH 4 transmitted to the atmosphere through broadleaf riparian tree species grown under flooded conditions. Using a leaf area normalized mean emission rate (0.7 ± 0.3 mg cm −2 hr −1 ), results were scaled globally for flooded forest regions and estimated to be 60 ± 20 Tg year −1 , ∼10% of the global CH 4 source. The carbon isotopic composition of CH 4 emitted was found to be significantly enriched compared with expectations (d 13 C ∼ −54‰) and provided an important isotopic constraint on the global source which coincides with the mean of the globally scaled greenhouse-based estimate. Citation: Rice, A.

Collectively, man-made emissions of a few greenhouse gases may cause about the same amount of global warming as increasing carbon dioxide. Among the most potent of these non-CO2 greenhouse gases are the perfluorocarbons that have extraordinarily long atmospheric lifetimes of 10,000 to more than 50,000 yr. We report atmospheric concentrations over two decades, between 1978 and 1997, of the three most abundant perfluorocarbons--CF4, C2F6, and C3F8--and delineate the sources that account for the present abundances and trends. We show that C2F6 and C3F8 are present at only 2.9 and 0.2 pptv, respectively. CF4 is the most abundant perfluorocarbon at 74 pptv (in 1997) of which about 40 pptv are from natural emissions, 33 pptv from aluminum manufacturing, and 1 pptv from the semiconductor industry. The increasing trend of CF4 has slowed in recent years due to the major reductions in the emission rate per ton of aluminum produced. The effect of the falling emission factor is partially offset by increased production and increasing use by the semiconductor industry.