I finally understand methane lifetimes

I'm curious where you're getting the figure that the relevant frequencies are 100% absorbed, I didn't think it was that high, but I'm far from an expert on this. I don't think you can ever get to 100%, just arbitrarily close -- there's always the chance that a given photon will get lucky and escape without hitting any CO2 molecule.

But I think that if every IR molecule that was radiated from earth hit a CO2 molecule, what would happen after that first absorption would matter. The photon would get re-radiated with an equal chance to go in any direction. If it goes up, great, it escapes into space -- but the more CO2, the more of a chance that it gets absorbed again and re-radiated back down.

So it's not a concrete wall, it's like a field of gopher holes with gophers that will take any golf ball that falls into their hole and chuck it out randomly. Even if the field is dense enough that you can't roll a golf ball directly across it without going into at least one hole, if you increase the density of gopher holes more, it still lowers the chance that the ball will make it to the other side.

*edit - This article[1] I just found goes more into the math, it helped clarify it a bit for me.

[1] https://www.geoexpro.com/articles/2022/04/recent-advances-in...

Do you have any sources for that?

Last time I researched this I saw various estimates that IR in the CO2 absorptions bands only makes it 10-25 meters before it 99% of it is absorbed by CO2. Your link gives and average distance of 2.6m for IR in the CO2 absorption band.

>Assume that [C]=400 ppm. The mean free path becomes 2.646m so that N=3024. The probability of returning to the Earth becomes p(1)=0.9997. A photon with frequency or wavenumber near the centre of the absorption band is virtually certain to make the return to Earth. If the CO2 concentration is doubled, the probability doesn’t change much; it becomes p(1)=0.9998. Any CO2 increase has minor effect on the photons in the center of the absorption band. This part of the band is ‘saturated’.

The website and other papers I have read seem to argue that it is not the majority of photons in the center of the emission and absorption band, but a much smaller number of off band photons in the "wings" that matter for the greenhouse effect. When I have tried to read about how this works, I get bogged down by the complexity of the science, and a lot of different arguments from the climate skeptic community which I don't have the foundational understanding to reject. They say that the shoulder theory is bunk because it ignores interactions between CO2 and other molecules. Instead of photons bouncing from CO2 to CO2, they say that the CO2 passes the energy off to nitrogen and oxygen.

I don't really give too much weight to the climate skeptic criticism, but I do have to acknowledge that greenhouse effect is a lot more complicated than taught in grade school and there is still a lot of active research using extremely simplified models trying to model how it works from first principles with a lot of exclusions and assumptions. like the paper cited in the link you shared from 2012.

Thank you for sharing the link, I will take some time to try to read and digest it.

> "Plass pursued a thorough set of one-dimensional computations, taking into account the structure of the absorption bands at all layers of the atmosphere. In 1956 he explained clearly, for the first time, that the water vapor absorption lines did not block the quite different CO2 absorption spectrum, adding that there was scarcely any water in the upper atmosphere anyway. He further explained that although some of the CO2 band itself was truly saturated, there were many lines to the side where adding more of the gas would increase the absorption of radiation. His arguments and calculations showed convincingly that adding or subtracting CO2 could seriously affect the radiation balance, layer by layer through the atmosphere, altering the temperature by a degree or more down to ground level."

https://history.aip.org/climate/Radmath.htm

Here's an additional bit of data that explains this rather oft-repeated old trope about CO2 saturation:

> "The early experiments that sent radiation through gases in a tube, measuring bands of the spectrum at sea-level pressure and temperature, had been misleading. The bands seen at sea level were actually made up of overlapping spectral lines, which in the primitive early instruments had been smeared out into broad bands. Improved physics theory and precise laboratory measurements in the 1940s and after encouraged a new way of looking at the absorption. Scientists were especially struck to find that at low pressure and temperature, each band resolved into a cluster of sharply defined lines, like a picket fence, with gaps between the lines where radiation would get through."

I guess you mean "we all know that almost no current government has the political courage to do what is necessary so that we decarbonize in time".

Or " we all know that we don't have the fortitude to do to do what is necessary so that we decarbonize in time". => that version is better if governments do what their public opinion is willing to do.

To fight in the WWI and WII, the most advanced economies of those times turned in less than two years into war economies, where more than 50% of the GDP was directed to the war effort.

True for Germany, France, the UK plus, for WWII, the USA, the USSR, Japan.

The Apollo program amounted during the 60s to 4% of the US GDP, just for the political sake of keeping up with the USSR.

If we considered - as we should - the dereliction of climate and the on-going massive reduction of biodiversity as an existential threat, we would act accordingly.

We can decarbonize in time. But we don't want to "look up", e.g. to listen to the Science.

Australia is having huge fires and large floods every year now - but still elect a government in denial of the causes.

In the USA, the natural disasters are rising sharply in frequency and magnitude (current drought in the West, hurricanes etc).

Etc etc.

When it will become unbearable, we will at last act accordingly. The solutions are there already.

There are many breakthroughs (batteries for example, to store surplus of renewables energies so that it can be used at will when necessary). Far many more would occur if we invested money in research and R&D.

We ought not to bet on a hypothetical magic bullet. Not that we shouldn't fund those research. Startups with small odds to succeeded easily raise VC money since a success would offer a huge ROI.

But the trap is to bet the future of the world on a hypothetical magic bullet when the solutions already exist. We just don't want to do what necessary to implement them.

The USA, Canada, Australia for example emit 3 times more CO2 than France per inhabitant. However, the loss of biodiversity is as fast (and maybe higher) in France (which governments do very little to tackle gashouse emissions).