WUWT: Dr. Vincent Gray on historical carbon dioxide levels

There are two gases in the earth’s atmosphere without which living organisms could not exist. ✧ Oxygen is the most abundant, 21% by volume, but without carbon dioxide, which is currently only about 0.04 percent (400ppm) by volume, both the oxygen itself, and most living organisms on earth could not exist at all. ✧ This happened when the more complex of the two living cells (called “eukaryote”) evolved a process called a “chloroplast” some 3 billion years ago, which utilized a chemical called chlorophyll to capture energy from the sun and convert carbon dioxide and nitrogen into a range of chemical compounds and structural polymers by photosynthesis. These substances provide all the food required by the organisms not endowed with a chloroplast organelle in their cells. ✧ This process also produced all of the oxygen in the atmosphere. ✧ The relative proportions of carbon dioxide and oxygen have varied very widely over the geological ages.

Read More (with charts): Watts Up With That?

I'm guessing they don't teach this stuff in school. Shameful, if not. --bc