Climate Part 3
We all learned the composition of the atmosphere in grade school but with recent news I thought carbon dioxide and methane had increased so dramatically the earth was going to burn up. So perhaps a refresher is in order:
“The atmosphere is composed of a mix of several different gases in differing amounts. The permanent gases whose percentages do not change from day to day are nitrogen, oxygen and argon. Nitrogen accounts for 78% of the atmosphere, oxygen 21% and argon 0.9%. Gases like carbon dioxide, nitrous oxides, methane, and ozone are trace gases that account for about a tenth of one percent (0.1%) of the atmosphere. Water vapor is unique in that its concentration varies from 0-4% of the atmosphere depending on where you are and what time of the day it is. In the cold, dry artic regions water vapor usually accounts for less than 1% of the atmosphere, while in humid, tropical regions water vapor can account for almost 4% of the atmosphere. Water vapor content is very important in predicting weather.”[1]
What is a greenhouse gas? When energy leaves earth on the way to outer space, it is in the form of infrared radiation (IR radiation). Some atmospheric gases can absorb IR radiation and some cannot. The ones that do are called greenhouse gases. When a greenhouse gas molecule absorbs IR radiation, the molecules vibrate faster and become “hotter”. They cool off when they reemit the IR radiation. There is a process of absorption and reemission until the gas reaches the upper atmosphere and escapes into space. Repeated absorption and reemission of IR radiation slows down the passage of IR radiation through the atmosphere and it is warmer than it would be otherwise.[2]This is commonly called the greenhouse effect. Global warming theory suggests that increased concentrations of greenhouse gases increase the greenhouse effect and therefore warming.
Keep in mind the greenhouse effect is what makes our planet habitable. Without greenhouse gases temporarily trapping warmth, earth would be one big ball of ice.
The primary greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide and ozone. The most plentiful greenhouse gas in the atmosphere is water vapor at 27,000 ppmv (parts per million by volume), followed by carbon dioxide which is approximately 415 ppmv and methane at 2ppmv. The figure below graphically displays the composition of the atmosphere. Note there is debate on how much carbon dioxide in the atmosphere is man-made. We will dig into that in a future blog.
What I either did not know or forgot is:
- Carbon dioxide and methane are a miniscule part of the total atmosphere at .04% and .0002% respectively.
- Water vapor is the primary greenhouse gas by a long shot and has an average concentration over the earth of 2.7%.
- There are 70 times more water molecules in near-surface air than carbon dioxide molecules and 14,000 more than methane.[3]
Learning that carbon dioxide and methane concentrations are miniscule compared to water vapor was rather eye opening. Then I discovered that everyone seems to agree that fluctuations in carbon dioxide do have an impact. The climate wars rage over the nature and magnitude of the impact. We are now at the end of consensus. It’s a free for all after this…
[1]https://climate.ncsu.edu/edu/Composition
[2]“The Mythology of Global Warming” by Dr. Bruce Bunker
[3]“The Mythology of Global Warming” by Dr. Bruce Bunker