This is an illustration from a post entitled A Deep Dive into Polar Ice Cores:
I had a minor confusion corrected by this post. I thought the diffusion process primarily upward when the air in snow is squeezed by the weight of more snow. Though this happens, it's not as pronounced as the diffusion between air and snow that occurs. This post was part of a new idea of answering questions posed the site from readers.
Skeptical Science also started a new project of science analogies that provide experiments or observations one can make to understand the climate system. These diagrams are from two analogies:
SkS Analogy 3: Greenhouse Effect Is Like Clouds at Night
I'm having a private Ferrari vs VW thing going.
UPDATE: Some recent links to publications that mention Skeptical Science: