Panel (a): T-dependence of absorption cross sections (cm²/molecule) of methane in the upper part of the icosad at five temperatures, 295, 400, 500, 600, and 1000 K: low-resolution (R = 2 cm⁻¹) simulations of observations (up) and theory (down). Panel (b): log-scale comparison of observed (up) and theoretical (down) methane absorption cross sections at the upper edge of the icosad for two temperatures T = 600 K (green) and 1000 K (red): medium-resolution (R = 0.2 cm⁻¹) simulations. Panel (c): high-resolution (R = 0.02 cm⁻¹) comparison between observations (up) and the theory (down) for the methane cross sections for the strongest absorption features of the icosad at three temperatures T = 400 K (blue), T = 600 K (green), and T = 1000 K (red).