Methane Feedbacks to the Global Climate System in a Warmer World

Abstract Methane (CH 4 ) is produced in many natural systems that are vulnerable to change under a warming climate, yet current CH 4 budgets, as well as future shifts in CH 4 emissions, have high uncertainties. Climate change has the potential to increase CH 4 emissions from critical systems such as wetlands, marine and freshwater systems, permafrost, and methane hydrates, through shifts in temperature, hydrology, vegetation, landscape disturbance, and sea level rise. Increased CH 4 emissions from these systems would in turn induce further climate change, resulting in a positive climate feedback. Here we synthesize biological, geochemical, and physically focused CH 4 climate feedback literature, bringing together the key findings of these disciplines. We discuss environment‐specific feedback processes, including the microbial, physical, and geochemical interlinkages and the timescales on which they operate, and present the current state of knowledge of CH 4 climate feedbacks in the immediate and distant future. The important linkages between microbial activity and climate warming are discussed with the aim to better constrain the sensitivity of the CH 4 cycle to future climate predictions. We determine that wetlands will form the majority of the CH 4 climate feedback up to 2100. Beyond this timescale, CH 4 emissions from marine and freshwater systems and permafrost environments could become more important. Significant CH 4 emissions to the atmosphere from the dissociation of methane hydrates are not expected in the near future. Our key findings highlight the importance of quantifying whether CH 4 consumption can counterbalance CH 4 production under future climate scenarios.