A question of causation: Does more CO2 lead to global warming or is the reverse true?

This might be something to keep in mind when the Obama administration declares CO2 a public danger this week.

Leighton Steward is a leading geologist.

But Steward, who once believed CO2 caused global warming, is trying to fight that with a mountain of studies and scientific evidence that suggest CO2 is not the cause for warming. What's more, he says CO2 levels are so low that more, not less, is needed to sustain and expand plant growth.

Trying to debunk theories that higher CO2 levels cause warming, he cites studies that show CO2 levels following temperature spikes, prompting him to back other scientists who say that global warming is caused by solar activity.

In taking on lawmakers pushing for a cap-and-trade plan to deal with emissions, Steward tells Whispers that he's worried that the legislation will result in huge and unneeded taxes. Worse, if CO2 levels are cut, he warns, food production will slow because plants grown at higher CO2 levels make larger fruit and vegetables and also use less water. He also said that higher CO2 levels are not harmful to humans. As an example, he said that Earth's atmosphere currently has about 338 parts per million of CO2 and that in Navy subs, the danger level for carbon dioxide isn't reached until the air has 8,000 parts per million of CO2. . . .