Gas-fired stations emit much less carbon dioxide, per unit of electricity, than coal, which also gives off all sorts of other nasties when burned, from sulphur dioxide to mercury.
Older volcanic rocks tend to emit less infrared, say the researchers, because carbon dioxide and sulphur dioxide in the planet's atmosphere weather the rocks and change their composition.
For years, its power stations had been emitting large amounts of sulphur dioxide, which was falling back to Earth as acid rain, causing harm to plants, aquatic animals and infrastructure.