Projected amplification of global warming by warming-induced greenhouse gas emissions

Warming-induced emissions (WIE) of greenhouse gases from natural sources are a large amplifying feedback that most climate models do not yet represent. This absence risks systematic underestimation of projected future warming and overestimation of remaining carbon budgets. To assess the potential magnitude of these feedbacks, we derived relationships between global temperature and WIE rates from process-based model estimates across three Shared Socioeconomic Pathways, SSP1-2.6, SSP2-4.5, and SSP4-6.0. The warming-induced methane emission rate from permafrost, wetlands, freshwaters, and wildfire combined increases with temperature at an estimated 97 ± 6 Tg CH4 yr−1 °C−1 across all three scenarios, while the warming-induced carbon dioxide emission rate from permafrost and wildfire combined increases at 7 ± 1 Pg CO2 yr−1 °C−1 in SSP2-4.5 and SSP4-6.0. Using the MAGICC climate model, we projected that WIE could add 0.2 °C–0.4 °C of warming by 2100 across scenarios, split roughly equally between carbon dioxide and methane, amplifying post-2020 anthropogenic warming by 20%–30%. Combined emission sensitivity and climate response 1σ uncertainties are ±0.2 °C on the added warming and ±10%–30% on the warming amplification.