Q. 77: How was the pre-Flood atmosphere different from today’s, and if so, why?
CPT Q. #77 – 101 Q&A on Catastrophic Plate Tectonics
Question: 77. I am pursuing the idea that prior to the Flood there could have been a somewhat higher density atmosphere, subsequently partially removed by the events of the Flood. If such were the case, could we then surmise that original proportions of atmospheric gases (nitrogen, oxygen, CO2, argon, etc.) were approximately the same as today, but that this might not be true for water vapor, as outlined below? With respect to water vapor, please consider and comment on its possible lower pre-flood density and partial pressure and any significant impact on pre-Flood greenhouse effect. Genesis 2:6 identifies the “mist” that “used to rise from the earth and water the whole surface of the ground”. Would you concur that this implies only fog or low clouds condensing as dew in reasonably close proximity to the ground? What would the effect on dew point be with say, twice today’s atmospheric pressure? With vastly reduced water surface areas of pre-flood lakes, streams and oceans (if any) and hence vastly reduced atmospheric water vapor ‘recharging’ due to evaporation, what meteorological effects would you then anticipate regarding total pre-Flood atmospheric water vapor content, and in particular, what greenhouse effects? Could it then follow that water vapor’s pre-Flood greenhouse effect would be proportionately less than today’s?
Response: That the earth’s atmospheric regime was different before the Flood compared with that of today seems clear from the plant and animal assemblages we find preserved in the fossil record. Such evidence seem to indicate strongly that the pre-Flood climate supported much more abundant vegetation over a larger fraction of the land surface (and possibly also over part of the sea surface in the form of floating mats of plants) compared with today. Moreover, from the large size of pterosaurs and some insects, there is a hint that the atmospheric pressure may well also have been higher than it is today. So what can we surmise from these clues from the fossil record about the pre-Flood atmospheric regime? I myself try to be cautious in my discussions of such matters. However, it seems almost certain to me that the greenhouse effect was stronger than it is today to allow the climate even at high latitudes to be relatively mild. This increased greenhouse effect relative to today would plausibly result from higher atmospheric levels of CO2 or water vapor, or more likely both.
On the issue of how the earth was watered before the Flood, to me the simplest way is the way it is today, that is, by rainfall. I believe caution is in order in how one interprets Genesis 2:6. The context of that verse is during Creation Week, when “there was no man to till the ground,” that is, before God created Adam and Eve. Once God creates Adam, however, the constraints surrounding Genesis 2:6 seem to go away. As far as I can determine, there does not seem to be a compelling case either way from Scripture as to whether or not there was rain during the interval between Adam and Noah. Hence, to me the possibility that the earth was watered primarily by rain before the Flood is a real one.
Moreover, given that a large fraction of the earth’s surface was almost certainly covered by ocean water before the Flood, as it is today, plus the fact that the average surface temperature was almost certainly higher, to me implies that the amount of water vapor in the atmosphere prior to the Flood was at least as high as it is currently. If so, this implies that water vapor’s absolute contribution to the greenhouse effect was at least as large as it is today. However, if before the Flood the total amount of CO2 in the atmosphere was higher than today, as I suspect it was, then indeed the fractional contribution of water vapor to the overall greenhouse effect could conceivably have been smaller.