Professor Ian Plimer

On average.

Yes.

And then it warmed up quickly in the interglacials and then it cooled down again.

That's not driven by carbon dioxide.

That's driven by something else, like that great ball of heat in the sky we call the sun.

It's driven by the Earth's orbit.

It's driven by many, many other factors.

It's driven by where the continents might be.

So we've had very high carbon dioxide in the atmosphere before.

And what has happened is we've sequestered that into carbonate rocks.

And this has been happening for a long period of time.

Now, with those old negotiations, the carbonate rock was dolomite, which has got 48% of the gas carbon dioxide in it.

That's by weight.

And so we pulled that carbon dioxide out of the atmosphere.

And in younger times, in the last 20% of time, we've...

pulled carbon dioxide out of the limestone.

We pulled it into carbon-rich sediments, black shales, into coals, into the shells, which are now fossils, into carbon-rich rocks.

So that's been sequestered out of the atmosphere.

And that process has been going on for at least a billion years.

But we certainly have got very good evidence that