AMAP assessment 2015 : Methane as an arctic climate forcer

What are the current What are current global What are the trends What is the contribution of Related to anthropogenic methane emissions from anthropogenic methane and variability in Arctic historical changes in global emissions characterization/ Arctic terrestrial and emissions, and those of methane concentrations atmospheric methane to Arctic quantification/projection? [...] While the total emissions of methane are fairly to account for approximately 50% of the global total methane well constrained, the division of the total among the individual emissions, while other estimates suggest anthropogenic sources and, in particular, the variability of individual sources emissions may account for over 60% of the global total and the contribution of changes in sources to the [...] Indeed, the sum of the best-guess estimates for each source 1675 from the bottom-up studies yields a global total emission of 680 Tg CH4/y (Table 2.1), which falls outside the uncertainty range of the ‘top-down’ estimate of global total emissions of Rate of change in CH4, ppb/y 554 ± 56 Tg CH4/y derived from the methane abundance Methane growth and estimates of atmospheric lifetime (Prather et al. [...] Uncertainty in the observations used to derive the decrease in In terms of the more recent past, the rate of increase in the microbial emissions (Levin et al.