How Do Methane and Hydrogen Sulfide Contribute to Global Warming?

[moriah]

TL;DR

Atmospheric scientists are reporting that methane is the second most prevalent gas trapped in the ozone layer.

Methane and hydrogen sulfide are supposed to be heavier then air, thus why they remain in low lying areas. I am to believe that only when they begin to disintegrate, they rise into the atmosphere. So my question is, if these gases are already disintegrated, how can they be so formidable?

 

[Astronuc]

Summary:: Atmospheric scientists are reporting that methane is the second most prevalent gas trapped in the ozone layer.

Methane

Methane (CH₄) has a molecular mass of 12+4*1 = 16 amu. N₂ has a molecular mass of 2*14 = 28 amu, and O₂ has molecular mass of 2*16 = 32 amu. 16 < 28, 32, so methane is a lighter molecule than the two main constituents of air, and methane would be lighter barring any hydrogen bonding with other molecules. Also, density of methane = 0.657 kg/m³, while density of air is 1.225 kg/m³, consistent with the lighter CH₄ molecule.

H₂S, molecular mass 2*1 + 32 = 34 is slightly heavier than O₂.

So my question is, if these gases are already disintegrated, how can they be so formidable?

If methane and hydrogen sulfide absorb more energy from sunlight than the air, then those molecules would diffuse into the air. If they exchange heat with the air, the warmer air rises while colder air somewhere sinks. Methane could be carried aloft with warm air, and if enough methane is present, light methane molecules displace air molecules, which makes that volume of air 'lighter', even without additional heating.

 

[Ken Fabos]

Summary:: Atmospheric scientists are reporting that methane is the second most prevalent gas trapped in the ozone layer.

Methane and hydrogen sulfide are supposed to be heavier then air, thus why they remain in low lying areas. I am to believe that only when they begin to disintegrate, they rise into the atmosphere.

This sounds like a basic misunderstanding.

Convection driven bulk air movements and accompanying turbulence mixes these gases at large scales, irrespective of their relative densities. Volcanic H2S from large eruptions for example is carried high into the atmosphere because of convection.

Diffusion mixes them at small scales even in still air. They don't stratify in the atmosphere although higher concentrations are near sources. "Disintegration"?

 

[moriah]

This sounds like a basic misunderstanding.

Convection driven bulk air movements and accompanying turbulence mixes these gases at large scales, irrespective of their relative densities. Volcanic H2S from large eruptions for example is carried high into the atmosphere because of convection.

Diffusion mixes them at small scales even in still air. They don't stratify in the atmosphere although higher concentrations are near sources. "Disintegration"?

That answered my question very thoroughly. I was mistaken about the density of methane: it’s lighter than air. However in light of your response, density is rather irrelevant. Understanding this issue at your level of expertise is critical at this point in history.