The debate over pricing carbon has been reignited after the Government's Environment spokesman confirmed – and then backtracked on comments - that introducing a carbon price for power companies would be considered as part of a climate change review.

It's a politically touchy topic — the ousting of Malcolm Turnbull as opposition leader in 2009 and Kevin Rudd as prime minister in 2010 can both be attributed in part to positions on emissions trading schemes (ETS).

It's also a topic with a long history. Former prime minister John Howard first floated the idea of an ETS in 2007.

Here are the five things you need to know if you want to join the conversation.

The Environment Minister had backtracked on his comments.

On Monday, Environment and Energy Minister Josh Frydenberg announced the terms of reference for a review of climate changes policies, to be undertaken and completed next year.

Mr Frydenberg said there was potential for an "emissions intensity scheme", where power generators could pay for emissions above a set level.

"We know that there's been a large number of bodies that have recommended an emissions intensity scheme, which is effectively a baseline and credit scheme, we'll look at that," he said.

But on Wednesday, both he and Mr Turnbull ruled out the notion.

"I didn't mention an emissions intensity scheme, it’s not in any document that the Coalition has put out, in relation to this review," Mr Frydenberg told Melbourne’s 3AW Radio.

But the now dismissed scheme did sound very familiar.

The carbon tax introduced by the former Gillard government — and scrapped by Tony Abbott — was a scheme that covered the entire economy.

The new proposal the Government has backtracked on would have applied to individual sectors.

It all hinges on what penalties would be faced by power generators when their emissions go above that set level.

In that way, it sounds similar to a standard ETS, where the government caps total emissions and issues permits to emit up to that amount.

The Coalition was responsible for axing the carbon tax.

The former Abbott government was responsible for the repeal of the tax in 2014 after the legislation was initially blocked by the Upper House.

It followed an election campaign on the issue with Mr Abbott vowing to have the repeal legislation before Parliament within 100 days of his victory.

You may remember him talking out against the tax in 2011, when he made headlines for addressing a rally in front of a "ditch the witch" placard.

But that was under Abbott, who rolled Turnbull over climate change in 2009.

Mr Turnbull was ousted as Liberal leader in 2009 after a lengthy brawl over climate change policy.

His support for then prime minister Kevin Rudd's amended ETS led to weeks of division within the Coalition.

Mr Abbott, who won the leadership spill by one vote, withdrew the party's support for the scheme and said a Coalition policy would not involve any new taxes.

Abbott instead introduced Direct Action.

And that's what we have in place now.

Instead of a tax, Direct Action provides financial incentives for polluters to reduce emissions though the Emissions Reduction Fund.

Since losing the Liberal leadership in 2009, Mr Turnbull has repeatedly expressed his support for an emissions trading scheme.

But he told reporters on Wednesday, "We will not be imposing a carbon tax and we will not be imposing an emissions trading scheme, however it is called".