Use of a process-based model for assessing the methane budgets of global terrestrial ecosystems and evaluation of uncertainty

[摘要] We assessed the global terrestrial budget of methane (CH₄) by using aprocess-based biogeochemical model (VISIT) and inventory data for componentsof the budget that were not included in the model. Emissions from wetlands,paddy fields, biomass burning, and plants, as well as oxidative consumptionby upland soils, were simulated by the model. Emissions from ruminantlivestock and termites were evaluated by using an inventory approach. TheseCH₄ flows were estimated for each of the model's 0.5° × 0.5° grid cells from 1901 to 2009, while accounting for atmosphericcomposition, meteorological factors, and land-use changes. Estimationuncertainties were examined through ensemble simulations using differentparameterization schemes and input data (e.g., different wetland maps andemission factors). From 1996 to 2005, the average global terrestrialCH₄ budget was estimated on the basis of 1152 simulations, andterrestrial ecosystems were found to be a net source of 308.3 ± 20.7 TgCH₄ yr⁻¹. Wetland and livestock ruminant emissions were theprimary sources. The results of our simulations indicate that sources andsinks are distributed highly heterogeneously over the Earth's land surface.Seasonal and interannual variability in the terrestrial budget was alsoassessed. The trend of increasing net emission from terrestrial sources andits relationship with temperature variability imply that terrestrialCH₄ feedbacks will play an increasingly important role as a result offuture climatic change.

[学科分类] 地球化学与岩石