Some people are of the opinion that the percentage of greenhouse gases in the atmosphere is so small that their contribution to the greenhouse effect would be minuscule. I see their reasoning; however, the even smaller amount of carbon dioxide of the past has been sufficient to keep the planet from being a giant ball of ice. And with no carbon dioxide at all, the temperature on Earth would be below zero degrees Fahrenheit.
https://samslair.blogspot.com/search?q=Snowball+Earth&m=1
For perspective, if you could bring all the clouds and water vapor in the atmosphere to the surface, it would form a ‘liquid’ layer less than an inch deep, and clouds alone would create a layer no deeper than a coat of paint. If just this past year’s carbon dioxide emissions alone could be confined to an undiluted layer of pure CO2 at the surface of the Earth, the layer would be about 1.5 inches thick.
“Nitrogen, oxygen and argon together comprise more than 99 percent of the atmosphere. None of these three gases absorb either visible or infrared light. It is as though, when it comes to the absorption and emission of light, the atmosphere’s three main players don’t exist.”
So, the only thing left to consider is the actual total amount of the greenhouse ‘trace gases’.
Water Vapor:
https://en.m.wikipedia.org/wiki/Water_vapor
Carbon Dioxide and Water Vapor As Greenhouse Gases:
https://www.scientificamerican.com/article/if-carbon-dioxide-makes-u/mm
Past CO2 Levels:
https://www.climate.gov/sites/default/files/paleo_CO2_2018_1500.gif
Note: Carbon dioxide is the most important of Earth’s long-lived greenhouse gases. It absorbs less heat per molecule than the greenhouse gases methane or nitrous oxide, but it’s more abundant and it stays in the atmosphere much longer. And while carbon dioxide is less abundant and less powerful than water vapor on a molecule per molecule basis, it absorbs wavelengths of thermal energy that water vapor does not, which means it adds to the greenhouse effect in a unique way. Increases in atmospheric carbon dioxide are responsible for about two-thirds of the total energy imbalance that is causing Earth's temperature to rise.
https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide
https://www.climate.gov/news-features/understanding-climate/climate-change-annual-greenhouse-gas-index
