Probably the most sensible solution is that the atmosphere was significantly thicker. 30% less heat input would drop the earth's temperature by about 20°C, but 20% more mass of air would increase the temperature by about 20°C at ground level. We know that during the age of the dinosaurs that there was a lot more oxygen in the atmosphere, it was up to about 30% O2 vs 20% now. Assuming the quantity of nitrogen is about the same (pretty safe as it doesn't react significantly or leak away) then you are looking at another 10°C just in the extra thickness of atmosphere caused by that extra oxygen.
Before about 800 million years ago the atmosphere had very little O2 and a whole lot of CO2, which would have made the atmosphere even thicker and further increased the temperature at the surface. Also the earth was spinning a lot faster and the thicker atmosphere transported heat better from the tropics to the poles, producing a wider latitudinal band of temperature climates (this is known from geological studies) On 14 August 2012 23:27, Harry Veeder <hveeder...@gmail.com> wrote: > Models of the Sun's evolution predict the Sun was 70% percent as > bright 2 billion years ago, and the Earth should have been an ice ball > at that time. Yet the geological record indicates the oceans were > liquid. > > A number of explanations have been proposed which haven't faired well > upon closer study. The lastest explanation says that the Earth at one > time orbited closer to the Sun: > > http://www.sciencedaily.com/releases/2012/05/120530152034.htm > > > Here is another: If LENR occurs inside the Earth then perhaps there > was sufficient LENR activity in the Earth billions of years ago to > keep the oceans liquid. > > > harry > >
