Dear Umbra, I know CO2 is a gas as other greenhouse gases are, and gases are sometimes lighter than air. So I'm wondering: how can gases be weighed in tons? That's a hell of a lot of gas to weigh even one ton, let alone the millions of tons that are reported to be causing climate change. (No, I'm not Oklahoma Sen. James Inhofe in disguise.) James N.,
Oklahoma City, Okla.