Minimal impact of methane on satellite-era climate change

The attribution of global and regional climate change to anthropogenic greenhouse gases (GHGs) is well appreciated. Existing estimates based on radiative forcing studies suggest CO₂ dominates global warming since 1850 with CH₄ the second largest contribution (33-66% of CO₂). However, radiative forcing studies involve several assumptions and GHG attribution beyond global-mean warming is unknown. Here we quantify the impact of individual GHGs on global warming indicators and regional climate change using single-forcing historical experiments of CO₂, CH₄, and other GHGs. CO₂ is shown to dominate global warming in the satellite era with CH₄ only 20% of the CO₂ contribution, smaller than the amplitude of internal variability. Methane is also a small contribution for other global warming indicators, including Arctic Sea ice loss, extreme temperatures and continental scale warming. The results demonstrate that, on multi-decadal or longer time scales, CO₂ is the dominant control knob and the contribution of CH₄ to regional climate change is very small, undistinguishable from noise. Thus, CH₄ mitigation may not be as effective as previously thought, particularly for regional scale impacts.