for scene 33 of the video " Ice Age Climate Change Precursors versus Global Warming Carbon Politics - Part 1 - Ice Age Climate, Normal Climate" by Rolf Witzsche - Ice Age Ahead not Global
here for a larger image
Double the CO2 concentration
The atmospheric CO2 concentration is presently close to the level where biological starvation begins. When commercial greenhouse operators double the CO2 concentration in their facilities they can achieve a 50% increase in plant growth. They also discovered that if they let the CO2 concentration diminish to half, plant growth stops altogether. During historic glaciation periods the CO2 concentration is known to have diminished to such low levels. The resulting food scarcity may be the reason why humanity came out of the last glaciation period with only a minuscule world population of 1 to 10 million people, after 2.5 million years of development.
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Published by Cygni Communications Ltd.
North Vancouver, BC, Canada - (C) in public domain - producer Rolf A. F.