EMILY BOURKE: David Karoly from Melbourne University's School of Earth Sciences is outraged.

DAVID KAROLY: This is misinterpretation or misrepresentation and miscommunication of the factors that influence global temperature. It appears to be an opinion of Phil Chapman and he's welcome to his opinion, but in terms of climate variations and an approaching ice age, he is sadly misinformed.

EMILY BOURKE: He argues the figures have been misinterpreted and he dismisses the theory.

DAVID KAROLY: Yes, the climate system did cool from January 2007 to January 2008 quite dramatically. That cooling was associated with changes in the ocean temperatures in the Pacific, a well known phenomenon, the El Nino to La Nina switch. It isn't unprecedented.

EMILY BOURKE: But you're not attributing that in any way to sunspot activity.

DAVID KAROLY: We know it is not due to sunspot activity. Sunspot variations do not lead to the sorts of temperature variations seen from January 2007 to 2008. They don't lead to those large temperature variations, even on an 11-year sunspot cycle.

And so in terms of increasing greenhouse gases, we can also see that effect because the most recent La Nina, the current La Nina, is warmer than earlier La Nina episodes of the same strength. We're actually seeing a warming even in these cool periods associated with La Nina.