On average it’s in a random direction, so some goes out into space eventually. But some goes straight toward the Earth’s surface, which also absorbs and then re-emits it.

The result is that some IR energy is trapped bouncing back and forth between the surface and atmospheric greenhouse gases (there are a few, not just CO2). This is the so-called “greenhouse effect” that keeps the surface habitable.

As you increase the amount of greenhouse gases, there are more molecules available to absorb and re-emit IR energy. So the total amount of energy that can be trapped bouncing back and forth goes up. More heat is trapped.

CO2 is particularly worrisome because the carbon cycle is slow. Water vapor has a larger effect, but it varies on the order of weeks (when it rains, for example). CO2 can take hundreds of years to get fixed again once it is in the atmosphere.

The next time I teach correlation/causation I’m using this as my goto example.

Wednesday, May 6th, 2009

at

http://books.google.com/books?id=DgqLplWtGPgC&pg=PA76&lpg=PA...

(but not now, no longer)

from page 76 of

Susan Milbrath, Star Gods of the Maya: Astronomy in Art, Folklore, and Calendars (The Linda Schele Series in Maya and Pre-Columbian Studies), ISBN-13 978-0292752269, University of Texas Press, 2000.

with

"Indeed, blood sacrifice is required for the sun to move, according to Aztec cosmology (Durian 1971:179; Sahaguin 1950 - 1982, 7:8)."