<< No one disputes that volcanoes weren't still hot 3.8 billion years ago, but
this isn't at issue here.  You should look at work by David Catling and Jim
Kasting (and associated references), and also google the "faint young sun
paradox"; it seems that even based on liberal interpretations of CO2
constraints during the early Archean, this greenhouse by itself would not
have been enough to keep the Earth's surface temperatures above 0 degrees C.
Hence the search for alternative greenhouse gases, such as methane,
necessary to tip the scales.

Yet there is strong evidence that methane was higher than thought. There seems
to not be enough CO2, not enough siderite in ancient soils (Astonomy July 2003)


It also seems that there is a lack of consensus emerging about this
"meteorite era" (prior to the late heavy bombardment) coming notably from
those who have looked most closely at what the lunar impact record is
telling us.  Aside from a spurt of activity around the Moon-forming impact
3.8 billion years ago, it is quite possible that the extent of the earlier
era of Hadean bombardment may have been greatly exaggerated.  Some recent
work by Graham Ryder ("Bombardment of the Hadean Earth...") that you might
look into if you're interested.

This is all debatable, but I think many are coming
around to the hot earth again. I'm sticking with it
for all those reasons I mentioned. You need to address
each one of those too, to convince me.

The less hot sun, isn't enough, nor is the lesser
bombardment scenario.

Tom


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