I still don't think I could count that as a gaffe. Is a cloud gas, or water in a near-vapour state? Regardless, it's definitely very low on the scale of dumb things politicians have done in recent times.
e.g. Jaymes Diaz, Craig Thomson, the entire One Nation party.
Those three are infinitely more stupid than Tony Abbott. Fair enough, it isn't the most definite example of a lack of scientific credentials, but he's consistently shown that he's woefully unaware about certain areas.
Rather than rattling off more cloud examples, and digging myself a hole, enjoy some comedic relief:
http://www.youtube.com/user/phonytonyabbottI get that gaffes don't define a leader, nor a person. We're all pretty smart people, yet we all say incredibly stupid things from time to time. It's just when the policy and the rhetoric reflects that lack of understanding.