The concentration of CO2 in the atmosphere is rising, as we all know. When I learned it in high school it was said to be 320 parts per million. Now it is higher. But this NASA animation, based on seven years of data from the Atmospheric Infrared Sounder satellite instruments, shows the dynamic changes over time and space. (I don't think the colors used to represent higher concentrations are deliberately chosen to be frightening--it's just convention. But they do pack an emotional punch that a more neutral color scheme would avoid.)
The superimposed graph is the CO2 concentration measured at the Mauna Loa Observatory in Hawaii. (If you can't see the video watch it here on YouTube.)
The popular understanding of the "greenhouse effect" is that greenhouse gases act like a blanket to keep heat from escaping from the Earth. This is incorrect. Greenhouse gases absorb radiation and heat up. They radiate some of that heat away, as any hot body would. Some of it goes out into space, and some is radiated down toward the surface, where some of it can be absorbed to make the surface warmer. It is more like an electric blanket than an insulating blanket. The more greenhouse gases there are, the more radiation they absorb and the hotter they get, and this changes Earth's temperature and climate.
There are more interesting NASA videos and graphics here.
[Originally written by Doc for, and crossposted from the HaraBara blog]