Three subjects dominate global warming and climate change discussions. They are global temperature, radiation absorption by carbon dioxide, and pre-industrial temperatures. It is useful to understanding some basics about these subjects. It can help in taking informed positions in the discussions.
Global temperature is usually taken as the average of temperatures from around the globe. However, temperature is an “intensive” quantity. Adding two or more together does not give a meaningful result. Mix two 1-liter bottles of water at 40 ºF. Combining them makes two liters of water. But, the temperature of the combined water is still 40 ºF, not 80 ºF. Adding temperatures makes no physical sense. Averaging temperatures requires adding them together. So, averaging temperatures cannot be physically meaningful, either. Consider your kitchen while baking a cake. The room may be a comfortable 70 ºF. But, the temperature inside the oven may be 350 ºF, the refrigerator, 40 ºF; and the freezer, 20 ºF. Does this make the average kitchen temperature 120 ºF?
Radiation Absorption by CO2
Carbon dioxide (CO2) molecules absorb certain radiation given off by the Earth. There are only about 400 CO2 molecules per every million gas molecules in the atmosphere. Each one creates a target of only about a billionth of a trillionth square-meter to catch the radiation. But, they are spread evenly throughout the atmosphere. And, the atmosphere is several miles thick. So, there are more than one trillion-trillion CO2 molecules in the atmosphere above each square meter of Earth’s surface. Even at their miniscule size, this amount of CO2 molecules blankets the Earth thousands of times over. This is true for the current atmospheric CO2 concentration of 400 ppm, as well as the 280 ppm pre-industrial concentration. So, how does thickening the already solid CO2 blanket by adding more CO2 trap more radiation?
Actual temperature measurements only go back to the 1800s. The temperatures used in climate change analyses occurring before the 1800s are guesses based on analyses of tree rings. Each ring in the cross-sectional cut of a tree trunk represents a year of its life. The thickness along with other characteristics supposedly indicates how warm the year of the ring was. There are uncertainties in this type of analysis. Many variables other than temperature affect how well a tree grows. Global warming involves temperature differences of only a few degrees. Does a tree grow differently during a 75 ºF summer than during an 80 ºF one? And, if so, can the temperature difference be detected accurately in a ring less that an inch thick?