Greenhouse gas effect of CO2 now better understood

In the 1800s, Swedish physicist Knut Ångström (the guy the Ångström length unit was named after - 1 Ångström = 3.94 billionths of an inch) said that adding more carbon dioxide (CO₂) to the atmosphere would not lead to global warming. His reasoning was sound and accurate based on the physics of the day. In a nutshell:

1. Atoms and molecules that absorb photons of light warm up by increasing their movements/vibrations in an amount equal to the amount of energy in the absorbed light - the light energy is converted to kinetic energy in the molecule. 

2. Most atoms and molecules that absorb light at a specific, precise wavelength (or narrow spectrum of wavelengths), with wavelengths much longer or shorter not absorbed because the atom or molecule cannot assume a kinetic energy state equal to the amount of energy in a photon at that wavelength. 

3. CO₂ warms the atmosphere by absorbing infrared light at a 15 micron wavelength (15 microns = 0.00059 inch). 

4. The amount of CO₂ in the atmosphere in the 1800s was sufficient to absorb all 15 micron light in the atmosphere, which is true.

5. Therefore adding more CO₂ to the atmosphere cannot increase the temperature of the atmosphere, that turned out to be false.

That little bit of science basically stopped the development of climate science for a long time. That came to an end when the data undeniably showed that adding more CO₂ to the atmosphere in fact was increasing the temperature of the atmosphere. That argument has been an argument in the climate science denial arsenal for decades.

Why the discrepancy? Physicists have just discovered a subtle quirk in the light absorption spectrum of CO₂. Carbon dioxide absorbs most efficiently at 15 microns, but it also absorbs significantly at a wavelength slightly above and below 15 microns. The new mode of light absorption explains why adding more CO₂ to the atmosphere is causing warming. 

How is that possible? The two oxygen atoms can vibrate in different ways, not just the one way that 15 micron light causes. In physical terms, 15 micron light causes the oxygen atoms to spin around the central carbon atom. But light slightly above and below 15 microns causes the two oxygen atoms to bounce back and forth on either side of a line with the carbon at the center, and those two kind of movement can fuse together.

Quanta magazine discusses this: 

Physicists Pinpoint the Quantum Origin of the Greenhouse Effect

A photon of 15-micron light contains the exact energy required to set the carbon atom swirling about the center point in a sort of hula-hoop motion. Climate scientists have long blamed this hula-hoop state for the greenhouse effect, but — as Ångström anticipated — the effect requires too precise an amount of energy, Wordsworth and his team found. The hula-hoop state can’t explain the relatively slow decline in the absorption rate for photons further from 15 microns, so it can’t explain climate change by itself.

15-micron light excited 

hoola-hoop state

The key, they found, is another type of motion, where the two oxygen atoms repeatedly bob toward and away from the carbon center, as if stretching and compressing a spring connecting them. This motion takes too much energy to be induced by Earth’s infrared photons on their own.

The bouncing springs motion

But the authors found that the energy of the stretching [bouncing springs] motion is so close to double that of the hula-hoop motion that the two states of motion mix with one another. Special combinations of the two motions exist, requiring slightly more or less than the exact energy of the hula-hoop motion.

This unique phenomenon is called Fermi resonance after the famous physicist Enrico Fermi, who derived it in a 1931 paper. But its connection to Earth’s climate was only made for the first time in a paper last year by Shine and his student, and the paper this spring is the first to fully lay it bare.

“The moment when we wrote down the terms of this equation and saw that it all clicked together, it felt pretty incredible,” Wordsworth said. “It’s a result that finally shows us how directly the quantum mechanics links to the bigger picture.”

In some ways, he said, the calculation helps us understand climate change better than any computer model. “It just seems to be a fundamentally important thing to be able to say in a field that we can show from basic principles where everything comes from.”

Joanna Haigh, an atmospheric physicist and emeritus professor at Imperial College London, agreed, saying the paper adds rhetorical power to the case for climate change by showing that it is “based on fundamental quantum mechanical concepts and established physics.”

So there you have it, science fans. The CO₂ component of global warming is explained by Fermi resonance between hoola-hoop motion and springy thingy motion. Who would have thunk it? 

Climate science deniers now have to come up with a reason or two to reject this data, which they no doubt will do (or already have done). The life of a climate science denier just keeps getting harder and harder, or does it?

Q: See why it is so hard to debunk false climate science theories that the data denies but science cannot fully explain? 

By Germane: Snarling watchdog for the environment