Opposition Leader Tony Abbott has defended comments he made two years ago apparently advocating a carbon tax, saying "everything was different" then.

In the 2009 Sky News interview, Mr Abbott said there were some benefits to a carbon tax and said it was preferable to other ways of pricing carbon.

"If you want to put a price on carbon, why not just do it with a simple tax?" he asked.

"Why not ask electricity consumers to pay more, then at the end of the year you can take your invoices to the tax office and get a rebate?

"It would be burdensome, all taxes are burdensome, but it would certainly change the price of carbon, raise the price of carbon, without increasing in any way the overall tax burden."

The footage was uploaded to YouTube on Friday and shared on online social networks over the weekend, before being played on the ABC's Q&A program last night.

"It was a discussion on Sky Agenda at the time my book had come out in July 2009 and we were discussing the whole concept of a carbon price," Mr Abbott told Fairfax radio today.

"Don't forget that it was in 2009, Malcolm Turnbull was our leader and everything was different - it was before Copenhagen."

Health Minister Nicola Roxon told Q&A she had not seen the video before, but "enjoyed it".

The Federal Government is still struggling to sell the carbon tax plan, with another poll on Monday confirming its unpopularity with voters.

The Government says it has seen Treasury modelling showing the carbon price will help encourage more gas-fired electricity generation.

The ABC has also been told the modelling shows a 17-fold increase in non-hydro renewable electricity generation by 2050.

But Climate Change Minister Greg Combet will not publicly release the modelling yet, or talk about what it is predicting about the coal industry.

"It is a very comprehensive piece of work and we'll release it when it's released," he said.

Mr Combet seized on another report from Australian National University, saying job losses from the carbon tax could be absorbed by other parts of the economy.

He says that is a repudiation of the Minerals Council of Australia's warnings that 23,000 miners will be out of a job because of the tax.

"I wouldn't rely too much on the Mineral Council's assertion here," he said.

"Let's not forget in the resources sector there's a massive pipeline of investment in coal and LNG at the moment and a carbon price is not going to materially affect that in our judgement."