Fig. 2.

Estimated radiative forcing expressed as a probability density function. The uncertainty stems from 1) assumed $\pm$20% uncertainties in lightning NOx and tropospheric O₃, 2) uncertainty in the parameters used to estimate OH lifetime of CH₄ (38), and 3) uncertainty in the total radiative forcing due to CH₄ (38, 39). The $\pm$1 $\sigma$ uncertainty is shown above each curve. Dashed lines represent the first two factors, and solid bars underneath include all three sources of uncertainty.