Fig. 5. The resonant lod as a function of mean Earth temperature.

The green triangles correspond to PlaSim runs with a fixed ${\overline{F}}_{\odot }=0.88{\overline{F}}_{\odot ,0}$ (corresponding to an epoch of 1.5 Ga) and a surface pressure P_s = 2 bar. The points depict Pco₂ =[1,10,100,200,300] mbar, with higher Pco₂ yielding higher $\overline{T}$. Red pentagons correspond to LMD-G runs at the same epoch, with P_s = 2 bar. Pink triangles show Plasim results for ${\overline{F}}_{\odot }=0.82{\overline{F}}_{\odot ,0}$ (2.5 Ga), light blue hexagons show ${\overline{F}}_{\odot }=0.77{\overline{F}}_{\odot ,0}$ (3.5 Ga), and brown hexagons correspond to ${\overline{F}}_{\odot }=0.72{\overline{F}}_{\odot ,0}$ (4.5 Ga); for all these the lowest Pco₂ =10 mbar. For a given Pco₂, LMD-G returns $\overline{T}$ values lower by ∼5 to 10°C or about 2 to 8%, than those found by PlaSim. The black circles depict PlaSim runs with the present epoch atmosphere but with different ${\overline{F}}_{\odot }$. The orange dotted line is taken from the one-dimensional atmospheric model labeled “c” in figure 3 of (2), where the temperature is varied directly. Note that, while PlaSim and LMD-G find different relations between $\overline{T}$ and Pco₂, the two codes find very nearly the same relationship between $\overline{T}$ and P_res. Furthermore, both codes predict a relation between P_res and $\overline{T}$ that mimics the one found by PlaSim when holding Pco₂ fixed and varying $\overline{F}$.