Posted on 24 April 2017 by Evan
A Ferrari without gasoline goes nowhere.
Greenhouse gases without infrared radiation cause no warming.
- The concentration of greenhouse gases is like the size of a car engine: higher greenhouse gas concentration is like a bigger engine.
- Infrared radiation is like the gasoline in the tank of a car.
- Just as gasoline is the fuel that drives an engine, infrared radiation is the fuel that drives the greenhouse effect.
Global warming occurs because infrared radiation emitted from the surface of the Earth is captured by greenhouse gases in the atmosphere, increasing the temperature of the atmosphere. Increased greenhouse-gas concentrations in an atmosphere with constant background infrared radiation will absorb an increasing fraction of the emitted infrared radiation, causing warming. Increased greenhouse-gas concentrations in the atmosphere combined with increased infrared radiation (e.g., due to reflective snow and ice melting exposing dark oceans that absorb solar radiation and reemit it as infrared radiation) causes even faster heating, such as is happening in the arctic.
Some skeptics point to Snowball Earth to “prove” that CO2 does not cause warming, by noting that 650 million years ago CO2 concentrations exceeded 1000 ppm yet the world was frozen solid, even down to the equator. Part of what allowed Snowball Earth to occur was because solar radiation was 4% lower than today, but a major reason that Snowball Earth persisted for so long is that snow and ice reflect 90% of incoming solar radiation, reducing infrared radiation to the point that the greenhouse effect was severely reduced.
The claim of some skeptics is that because Snowball Earth saw CO2 levels exceed 1000 ppm in the presence of a global ice age, that we could exceed 1000 ppm CO2 today without any adverse effects. What such arguments fail to note, however, is that global warming requires two actors: infrared radiation to provide the heat and greenhouse gases to catch and trap the heat. Without one or the other there is no warming, kind of like a Ferrari that goes nowhere without gas in the tank. During Snowball Earth there was very little infrared radiation to fuel global warming.
Skeptics also conveniently fail to note that once the ice began to melt after Snowball Earth, exposing land that absorbed energy from sun light and re-emitted it as infrared radiation, that with all of the greenhouse gases accumulated in the atmosphere during Snowball Earth, the earth warmed rapidly to one of its warmest periods ever, even with 4% lower solar radiation: high greenhouse-gas concentrations + infrared radiation caused rapid warming.
Today we have 4% higher solar radiation than during Snowball Earth. If in this century we burned all known fossil-fuel resources, we could exceed 1000 ppm CO2 once again and, because we now have higher solar radiation than during Snowball Earth, the climate we would experience would be more like the hothouse climate of the Eocene. (for additional reading see a study published in Nature Communications and summarized in this SkS posting).
The good news is that under these conditions alligators and crocodiles would once again be at home in the Arctic.