Fig. 6: Methane-climate feedback sensitivities and projected annual mean climate-feedback-contributions.

Sensitivities are expressed in ppb °C⁻¹ (a, b) or ppb yr⁻¹ °C⁻¹ (c, d) vs time (a–c), latitudes (a), or just °C (d). For (e), the projected annual mean ΔC_CH4, _climate/Δt curves are fitted based on values with both positive contributions and positive ΔGMST. The projected thick lines are based on extrapolation of global level sensitivities (d), and the thin lines are extrapolated similarly but based on a 10% higher calibration factor α. Solid and dashed lines are based on sensitivity trends since 01/2012 and 07/1985, respectively. The two open red circles represent preliminary estimates of ΔC_CH4/Δt between 2020 and 2019, and between 2020 and 2018, based on a 75% of imbalance (referring to the σ in Supplementary Table 1). The respective error margins are based on two standard deviations across 12 months of the year. The filled red circle is based on 100% of imbalance between 2020 Dec and 2019 Dec. The 100% assumption is based on the reduced fossil fuel emissions which suggest the observed increase in C_CH4 could be all driven by climate factors.