The video below popped on YouTube. Watch carefully from 3 mins 20 seconds or so, this is where he launched (or re-launched) the Big Climate Lie.
Note how Sagan constantly refers to "Earth's surface", not mentioning clouds. By implication, he is including clouds when considering solar radiation absorbed (or else his calculation wouldn't give the answer of about 30 degrees), so the obvious next question would be "Do clouds and cloud free ocean/land surface, in total, radiate upwards the same amount as they absorb in solar radiation?", as a reality check if nothing else, to which the answer is a resounding "Yes."
If the answer were "No", then this would raise a lot of questions - maybe there is a positive (or a negative) Greenhouse Effect? if so, what causes it?
Sagan neatly sidesteps this obvious question, and at 4 mins 20, launches into an alternative reality where clouds don't exist, and the solar radiation absorbed by clouds and oceans/land is all directly absorbed by the land/oceans. If it were, it would be a lot cooler - he is mathematically correct in saying that land/oceans would be about 30 degrees cooler than they are (the accepted figure nowadays is 33 degrees). James Hansen explained the calculation in more detail in 1988, three years later.
[Enjoy the cutaway shots of Al Gore with dollar signs rolling in front of his eyes.]
At 4 mins 30 Sagan concludes, "And why is it too low... it's too low because something was left out of the calculation. What was left out of the calculation..?"
An attentive listener would have screamed, "The clouds, you moron!", but nope.
Sagan of course trots out his preferred answer: The Greenhouse Effect" and then waffles on about CO2 trapping heat and all that nonsense.
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