Socioeconomic Costs of Future Wetland Methane Emissions Assessed with the PAGE-ICE Integrated Assessment Model

Wetlands are the largest natural source of atmospheric methane, but the socioeconomic consequences of future wetland CH4 emissions remain poorly quantified. We combined projected wetland CH4 pathways with the PAGE-ICE integrated assessment model to estimate their contributions to atmospheric CH4 concentration, radiative forcing, warming, and socioeconomic damages under SSP1-2.6, SSP2-4.5, and SSP5-8.5. By 2100, wetland CH4 emissions increased atmospheric CH4 concentrations by 782, 868, and 1207 ppb under the three pathways, respectively. The corresponding global warming increments were 0.190, 0.170, and 0.166 °C, showing that larger atmospheric CH4 contributions do not translate linearly into larger temperature responses. Wetland-attributable annual global damages reached 2.79, 5.91, and 6.49 trillion USD per year−1 by 2100, while discounted cumulative damages over 2020–2100 reached 79.96, 127.24, and 127.33 trillion USD under SSP1-2.6, SSP2-4.5, and SSP5-8.5. Regionally, Africa, the Middle East, and India accounted for the largest absolute damages, whereas Eastern Europe and the former Soviet Union had the highest losses relative to GDP and population. A sensitivity analysis identified transient climate response, damage-function curvature, and the pure time preference rate as the main controls on valuation uncertainty. These results indicate that projected wetland CH4 emissions can make a measurable marginal contribution to future climate damage and should be incorporated into sustainability assessments, methane-related climate-risk evaluations, and long-term adaptation planning.