How does methane contribute to global warming via positive feedback?

https://www.quora.com/How-does-methane-contribute-to-global-warming-via-positive-feedback

My reply:
Positive feedback? Sorry, but the so-called greenhouse warming theory is wrong because it assumes that just because CO2 and methane in the atmosphere block and trap infrared energy, they don’t really do that for long, they reemit it like a radio transmitter somehow, and send it all back to the surface in just as useful a form as they received it. This is bad physics, because the absorbed energy turns into kinetic energy, causing the way-outnumbered CO2 and methane molecules to bump into the surrounding O2 and N2 molecules and lose their heat, and those just heat up a little, losing their heat via the Wien Displacement Law, emitting very weak infrared radiation at even longer wavelengths.
Not only that, but the inverse square law reduces any radiation reaching the surface.
CO2 is only 0.04% of the atmosphere now, and even if doubled it would be less than 0.1%, which might heat the atmosphere some but can’t heat the surface any, sorry. Methane (CH4) is an even smaller fraction, .00017%. The atmosphere goes up for miles, and the truth is it’s function is to cool the surface heat deposited by the Sun by mainly replacing radiation (like on the Moon) with convection, and eventually dissipate it into the infinite heat sink of space, with its sheer mass keeping it from convecting the heat away instantly like radiation would, moderating the surface min/max temperatures within liveable limits, but never heating the surface more than the Sun did in the first place. On top of that, any heating of a gas in the atmosphere causes it to expand and cool adiabatically, which has already happened as it rose from the surface carrying heat away by convection. And even if a large mass of the atmosphere warmed from the Sun itself, CO2 and CH4 would absorb and block it from reaching the surface, heating the atmosphere not the surface, and the warmed trace gases would more likely cool the surface more by causing wind gradients that bring winds, rain, hail, and snow. Sorry, neither can cause a global runaway warming, although stormy weather is a possibility.
Here’s my take in full:
TLW's Two Cents Worth on Climate Change