Left-hand panels: radial abundances (with respect to n_H) of the cooling molecules (indicated in the figure) in models A (top), B (middle) and C (bottom). Solid lines correspond to t = 10⁵ years, dashed lines to t = 10⁶ years. Right-hand panels: the temperature profiles in models A to C. Solid lines correspond to t = 10⁵ years, dashed lines to t = 10⁶ years. Also plotted in each panel is the dust temperature (dotted lines).