R Colmore is half correct with his letter "Sun controls our climate" (The Weekend Sun, August 3).

The sun supplies the energy, the other half of the equation is the atmosphere itself.

As long as I can remember, I've known that carbon dioxide is a greenhouse gas; that is, an atmosphere
with carbon dioxide in it is warmer than one without.

The astronomy books I devoured as a teen in secondary school gave Venus as the prime example of an atmosphere where the greenhouse had run riot.

Or course, carbon dioxide is not the only
greenhouse gas; it's just that it's the one human civilization seems most adept at producing.

It might be worth noting that the sunspot cycle is not the only cycle that affects the Earth; there's the Milankovitch cycle, the periodic variations in the Earth's orbit and rotation axis.

It also might be worth noting that if we are in a current solar hibernation, it doesn't seem to be
working as expected - permafrost has been reported as starting to thaw and emit methane, in Siberia
and Canada.

W Parish, Bellevue.