Simulated temperature profiles with different methane abundances on Neptune. Left: CH₄ vmr profile on Neptune with the nominal CH₄ vmr profile (solid blue line, see Sect. 3), or with that abundance multiplied by two (short dashed orange curve), four (dotted green curve), six (dotted-dashed red curve), eight (long dashed violet curve), and ten (double dotted-dashed maroon curve) above the methane condensation level. Right: the corresponding simulated temperature profiles. The black symbols correspond to the observed temperatures described in Fig. 1.