There is no big secret that I am very skeptical of any claim that carbon dioxide, CO2, is a major factor in the Earth’s climate.
For starters, a “greenhouse gas” absorbs infra-red radiation, and hangs on to it. We have two primary greenhouse gases, H²0, and CO². Water vapor and carbon dioxide. A greenhouse gas will absorb certain parts of the infra-red spectrum, and essentially hold on to that energy. A gas that is present in high concentrations and that holds heat.
Energy balance calculations make it clear that if there were no greenhouse gases, the temperature at sea level would average about -18 C, or a chilly zero Fahrenheit. Greenhouse gases raise the Earth’s mean temperature to a comfortable mean of about 56.5 degrees, more or less – so greenhouse gases are good!
Now, here is an “absorption spectrum” of the earth’s atmosphere, cheerfully stolen from Wikipedia:
The wider and deeper the absorption “valleys” are, the greater the greenhouse effect.
Notice the relative width and depth of carbon dioxide’s absorption spectrum, compared to water vapor. There is a quite narrow CO² absorption band at 3 nanometers, and a very wide water vapor band between 5.25 and 7.75 nm. Along with other, minor, absorption bands.
For every erg of energy a carbon dioxide molecule absorbs, each water vapor molecule absorbs seven ergs. So water vapor is a much more effective greenhouse gas than carbon dioxide. And there is a lot more of it in the atmosphere.
At comfortable temperatures, there are between 10,000 and 20,000 water vapor molecules for every million molecules in the air we breathe. That can go as high as 32,000 per million on a really hot and muggy day, or as low as 7,000 per million during a chilly day in the Gobi.
There are only 380 carbon dioxide molecules per million in most of this planet’s atmosphere. So all that vaunted CO2 is only equivalent to just 54 more water vapor molecules. During that chilly day in the Gobi, carbon dioxide contributes one part in 130 to “warming.” But on a steamy day on the Amazon, carbon dioxide contributes a whopping one part in 600 to the overall warmth.
So carbon dioxide is actually a very minor greenhouse gas. Nitrogen is an extremely weak GHG – but there are many times as much nitrogen as carbon dioxide in air. So nitrogen contributes many times the amount of heat rise than carbon dioxide.
What will happen if atmospheric carbon dioxide levels continues to rise? Not much. If we know what we think we know, there is a theoretical limit to the amount of atmospheric carbon dioxide of close to 1,500 parts per million; or about four times the current levels. However, it is not likely we could burn all of the oil; plus all of the coal; plus all the trees, methane clathrates, and everything else.
If we really tried, we could probably raise atmospheric carbon dioxide level to the 750 part per million level. Which would do what? Not much, actually. Almost all of the “excess” would turn to vegetation very quickly, crops would grow faster and yields would improve, and mean temperatures would go up by about 1 degree. Fahrenheit.
And no, the seas would not turn to salty soda pop. Some corals would probably be forced to adapt to a slightly more acid environment, but the Earth has been through that before. Many times, in fact.
So yes, I am a “global warming skeptic.” And I have a lot of very good science to back my opinion.