A key question relates to the origin of the logarithmic scale of the greenhouse effect – the 2 to 5 degree temperature rise that models predict if CO2 concentrations were to double.2One theory is that this scaling depends on how quickly the temperature decreases with height. But in 2022, the research team used a simple model to prove that the logarithmic scale comes from the shape of the carbon dioxide absorption “spectrum” – its ability to absorb light scales at different light waves.
This goes back to wavelengths slightly longer or shorter than 15 microns. One important detail is that carbon dioxide absorbs less light at these wavelengths – but not much worse. Absorption falls at the right level on either side of the peak resulting in a logarithmic scale.
“The size of the spectrum is important,” he said. David was playing aroundA climate physicist at the University of California, Berkeley, who co-authored the 2022 paper “If you change that, you don’t get logarithmic scaling. “
The spectral shape of carbon is unusual – most gases absorb a very narrow range of wavelengths. “The question in my mind is: Why is it so big? ” Romps said. “But I don’t know why.”
the resulting friction
Wordsworth and his co-authors Jacob Seely and Keith Shine turned to quantum mechanics to find the answer.
Light is made up of packets of energy called photons. molecules like CO2 They can only be introduced if the packets contain the right amount of energy to bring the molecules into a different quantum mechanical state.
Carbon dioxide usually remains in its “ground state,” where its three atoms line up with the carbon atom equidistant from the other atoms. Molecules also have a “realistic” state, where their atoms are moving or moving.
A 15 micron photon of light has the energy needed to spin a carbon atom in a sort of hula-hoop motion around a central point. Climate scientists have long blamed this hula-hoop state for the greenhouse effect, but – as Angstrom predicted – Wordsworth and his team discovered that it is necessary at this effect on a lot of energy. The hula-hoop phase cannot explain the very slow decline in photon absorption rates beyond 15 microns, and therefore cannot explain climate change.
They discovered that the key was another type of motion, in which two oxygen atoms move back and forth from the carbon center, as if stretching and compressing the spring connecting them. This motion requires a lot of energy to be stimulated by the Earth’s own infrared photons.
However, the authors found that the energy of the stretch transition was about twice that of the hula-hoop transition, allowing the two transition states to combine. There is a special combination of the two movements, which require a little more or less energy than the actual energy of the hula-hoop movement.
This particular phenomenon is called Fermi resonance, after the famous physicist Enrico Fermi who proposed it in a research paper in 1931. However, its connection with the Earth’s climate was only discovered for the first time in 1931. paper This topic was studied by Shine and his students last year, and the paper published this spring is the first to explain this topic completely.
2024-08-25 11:34:24
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