The government recently announced it would slash emissions by 25 per cent by 2020 if the world agreed to stabilise atmospheric levels of greenhouse gas emissions at 450 parts per million "by 2050".

Concentrations of greenhouse gases are already higher than that.

Experts predict the concentration will go significantly higher before it could come back down in the long term, well after 2050.

Climate Change minister Penny Wong, who was grilled on the promise during a Senate estimates hearing on Friday, said the government had got it wrong.

The "by 2050" should not have been said.

"I acknowledge and take responsibility for the error in the press release," Senator Wong told the hearing, adding it should be been corrected.

The media release in question was issued earlier this month by Prime Minister Kevin Rudd and other ministers.

Australian Greens leader Bob Brown said it was a "monumental mistake" and the government should have publicly corrected it earlier.

The hearing also heard that Australia's emissions "continue to grow strongly" and are on track to hit 120 per cent of 1990 levels by 2020.

The government says it will cut emissions by between five and 25 per cent by 2020, depending on what other countries do.