Professor Flannery addressed more than 800 people at Launceston's Albert Hall last night at The Examiner-John West Memorial Lecture - an annual event hosted by the Launceston Historical Society in honour of The Examiner's first editorial writer, John West.

Professor Flannery said Tasmania's temperate forests were a greater store of carbon than previously thought.

"Inevitably the carbon flux in Tasmanian forestry is going to have to be taken into account," he said.

"In a well-managed forest, you'll probably get a credit, but if you are clearing old growth, you'll probably get a cost."

During the lecture, Professor Flannery praised the Rudd Government's Carbon Pollution Reduction Scheme as the right way forward for Australia, and described the Copenhagen summit as a "messy process" but an important step that reined in the world's biggest polluters.

The 2007 Australian of the Year spoke about the attempted discrediting by sceptics of climate change science, which he referred to as a politically motivated campaign and a "deliberate attempt to mislead the public".

"Virtually every academy of science around the world supports the basic science - it's 150 years old and nobody had ever doubted it before it became a political issue," he said.

He said climate science had become more concrete, delivered firmer findings and was better understood by the public, even though it was not directly observable to them.