a

. Gregory S. Jenkins et al., “Precambrian Climate: The Effects of Land Area and Earth’s Rotation Rate,” Journal of Geophysical Research, Vol. 98, 20 May 1993, pp. 8785–8791.

This paper acknowledges that if the Earth rotated almost twice as fast as it does today, this problem would be lessened—but not solved. Still required are a flooded Earth and an atmosphere with 30–300 times more carbon dioxide than today.

b

. Let’s assume an old Earth and at least a fifth of the atmospheric carbon dioxide needed to prevent a runaway ice age had been present throughout the Earth’s first 2,750,000,000 years. That carbon dioxide would have combined with weathered rocks to produce large amounts of the mineral siderite (FeCO₃). Siderite is missing from ancient soils, showing that the concentrations of carbon dioxide needed to prevent a frozen Earth were never present. [See Rob Rye et al., “Atmospheric Carbon Dioxide Concentrations before 2.2 Billion Years Ago,” Nature, Vol. 378, 7 December 1995, pp. 603–605.]

“There is no direct evidence to show that carbon dioxide levels were ever a thousand times higher.” Gregory Jenkins, as quoted by Tim Folger, “The Fast Young Earth,” Discover, November 1993, p. 32.

c

. William R. Kuhn, “Avoiding a Permanent Ice Age,” Nature, Vol. 359, 17 September 1992, p. 196.

d

. In 1972, Carl Sagan and George H. Mullen first proposed that the early Earth had lots of heat-trapping methane and ammonia. They had no evidence for early methane and ammonia; they simply were looking for something that might have warmed the Earth, so there would have been no runaway deep freeze and life could have evolved. At the time of Sagan’s death (1996), he was still looking.

e

. For a frank admission of these and other “special pleadings,” see Carl Sagan and Christopher Chyba, “The Early Faint Sun Paradox: Organic Shielding of Ultraviolet-Labile Greenhouse Gases,” Science, Vol. 276, 23 May 1997, pp. 1217–1221.