State emission targets can be dumped - if a national carbon tax is in place.

Dumping Victoria's target to cut greenhouse gas emissions by 20 per cent compared with 2000 levels by 2020 makes sense. As the state government's review of Victoria's Climate Change Act points out, a national target to cut emissions by 5 per cent over the same period has rendered the state target redundant. Leaving it in place would merely require other states to do less, at considerable expense to Victoria.

Releasing the review of climate change laws, Environment Minister Ryan Smith was keen to emphasise the point. He was less keen to discuss what would happen if Tony Abbott won the next federal election and delivered on his ''pledge in blood'' to repeal the carbon tax.

Abbott supports the 5 per cent national target, but says it could be achieved through his relatively inexpensive ''direct action'' plan, which would involve tendering for emissions reductions.

Yet the Baillieu government's review, headed by former senior state Treasury bureaucrat Lynne Williams, appears implicitly sceptical that the 5 per cent target could be met under Abbott's scheme, arguing a unilateral state target should be reconsidered if the federal carbon tax (due to become an emissions trading scheme in 2015) is rescinded or changed.

''In the absence of a national [emissions trading scheme], unilateral action on the part of Victoria through a target may be justified,'' the review says. ''In its simplest sense, this is because there is a greater chance that a state-based policy will result in reduced national emissions. Consequently, if the national [emissions trading scheme] is rescinded, or substantially amended, the Victorian government may wish to reconsider the merits of a state-based target.''

This is a crucial, yet overlooked, caveat.

Just hours after Smith binned the 20 per cent target, Energy Minister Michael O'Brien rushed out an announcement reversing an election commitment to impose limits on greenhouse gas emissions from new coal-fired power stations.

Why? Because the federal government shelved similar requirements late last year on the grounds that the carbon tax provided necessary incentives for emissions cuts without the need for explicit regulations.

As Smith revealed on Tuesday, he will talk to federal Climate Change Minister Greg Combet about other areas of state environmental policy that may be similarly reversed because of the carbon tax. The Victorian Energy Efficiency Target, designed to encourage large energy retailers to sell energy-efficient products, will almost certainly be among them.

There is much irony here. The Baillieu government is using the carbon tax as an argument to abandon state-based measures to cut emissions while campaigning vigorously to quash the tax, even as science continues to suggest climate change will have a potentially devastating impact on Victoria. (The government's own report this week warned of more heat-waves, rising seas, less snow, more bushfires and less rain.)

With polling showing concern about global warming is less likely to influence voting than previously, other states are also unwinding their environmental policies.

The incoming Liberal National government in Queensland, for example, is promising to slash $661 million worth of state-based environmental initiatives over the next three years, and, as one of his first acts, Premier Campbell Newman withdrew $75 million earmarked for the Solar Dawn project near Chinchilla, part of the federal government's Solar Flagship Program.

There are sound arguments to abandon some state-based targets and policies to achieve them - provided the federal carbon tax remains the key mechanism to meet the national target.

In the current political environment there are no guarantees. And with no national emissions trading scheme and no state-based measures, brown coal would virtually be given carte blanche to expand while paying little heed to the concerns of the planet. The more cynical among us might see this as the real agenda.

Josh Gordon is Age state political editor.

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