PS 22-17 - Global positive effects of climate change on terrestrial soil CH₄ emissions

Background/Question/Methods

Increased greenhouse gas emissions are causing unprecedented climate change, which is, in turn, altering the production and consumption of methane (CH₄) in terrestrial ecosystems. Previous manipulation experiments have improved our understanding of the impact of climate change on soil CH₄ fluxes; however, these responses varied widely between experiments (including positive, null, and negative responses). At present, it is still unclear in the comprehensive response of soil CH₄ fluxes (that is, methane uptake and emissions) from natural terrestrial ecosystems to various warming and precipitation scenarios. Here, we synthesize 730 observations of in situ soil CH₄ flux data from the past three decades related to temperature and precipitation changes across major terrestrial ecosystems worldwide.

Results/Conclusions

Meta-analysis reveals that warming (ranging from +0.1°C to +11°C) and decreased precipitation (ranging from −60% to −7% of local mean annual precipitation) not only stimulate soil CH₄ uptake from natural uplands but also promote soil CH₄ emission from natural wetlands. Increased precipitation (ranging from +4% to +94% of local mean annual precipitation) also stimulates soil CH₄ emission from natural uplands. Climate change is estimated to add 11.14 ± 0.42 Tg CH₄ yr^–1 as an additional global CH₄ source, with natural uplands and natural wetlands contributing 4.43 ± 0.36 Tg CH₄ yr^–1 and 6.71 ± 0.07 Tg CH₄ yr^–1, respectively. A global positive effect of climate change on CH₄ emissions was mainly attributed to increased CH₄ emissions from natural terrestrial ecosystems. Although an increased CH₄ uptake by forest and grassland soils caused by increased temperature and decreased precipitation can offset some of these additional CH₄ sources, the substantial effect of increased precipitation on CH₄ emissions makes these sinks insignificant. Our meta-analysis strongly suggests that climate change will weaken the natural buffering ability of terrestrial ecosystems on CH₄ fluxes and thus contribute to a positive feedback spiral.