A walk down memory lane in honor of the Paris Climate Conference, (well and also for my pal AL with his hate-on for Dr. Mann and rejection of climate proxy work in general as described in the comments thread at Prof Ivar Giaever's pathetic YouTube PseudoScience talk), I'm going to reprint a few posts I'd originally written for my Citizenschallenge Blog a couple years back since the information they hold is a valid and relevant today as it was then.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
"... Many ingenious hypotheses have been proposed to account for the warmer climate of earlier times, but are at best unsatisfactory; and it appears to me that the true solution of the problem may be found in the constitution of the early atmosphere, when considered in the light of Dr. Tyndall's beautiful researches on radiant heat.
He has found that the presence of a few hundredths of carbonic acid gas in the atmosphere, while offering almost no obstacle to the passage of the solar rays, would suffice to prevent almost entirely the loss by radiation of obscure heat, so that the surface of the land beneath such an atmosphere would become like a vast orchid house, in which the conditions of climate necessary to a luxuriant vegetation would be extended even to the polar regions."