Russell Bender (Readers' Forum, Dec. 8) should realize the greenhouse effect of additional CO2 started 8,000 years ago when we began cutting down forests to grow grain. We are now 5,000 years into the next ice age, which means that northeastern Canada should be under a sheet of ice but instead is getting a second cut of hay on the west coast of Greenland.
Bender is, of course, correct that the sun has a lot to do with temperature on the Earth. Currently, the greenhouse effect is apparently being partially offset by low output from the sun (there are still no sunspots).
Bender's kind of thinking would place the Earth at the center of the universe.