If I understood correctly, for that model they varied the "surface temperature" of a 1-dimensional object under constant illumination by hard-coding it, rather

If I understood correctly, for that model they varied the "surface temperature" of a 1-dimensional object under constant illumination by hard-coding it, rather than simulating an increase in insolation or pressure to cause warming: "When surface temperature is below the critical point temperature (647K), the surface pressure is set as the saturation vapour pressure for that surface temperature, and the tropospheric temperature– pressure structure is taken directly from the saturation vapour pressure curve. Where the surface temperature exceeds the critical point temperature, we prescribe surface pressure as 2.6×107 Pa, corresponding to Earth’s surface water reservoir." http://www.nature.com/ngeo/journal/v6/n8/full/ngeo1892.html http://www.nature.com/ngeo/journal/v6/n8/full/ngeo1892.html So first, they do increase the thickness of the atmosphere, and the increased surface temperature would come from a possible future sun (not adding CO2) I guess. Second, I wouldn't put much stock in such simplified models.