"the science is certain" was unnecessary -- the effect of the precautionary principle is that the science supporting the theory does not have to be certain, but the case against the theory does.
Julia Gillard's climate change committee to explore carbon price options reflects the precautionary principle in the climate change debate
This principle has revolutionised international and Australian environmental science and environmental law. The precautionary principle has driven the international movement to reduce greenhouse gas emissions, but it has been ignored in the public debate. It is also the reason that climate sceptics could never win.
The principle appears in Article 3 of the UN Framework Convention on Climate Change 1992. It is one of the four principles of ecologically sustainable development.
Those principles have been absorbed into Australian environmental law at commonwealth and state levels since 1991.
In a speech given in December 2009 at a symposium in honour of retired judge Paul Stein, chief judge Brian Preston of the NSW Land and Environment Court described the effect of the precautionary principle which appears in NSW legislation in similar terms to Article 3 of the 1992 Climate Convention:
Updated below with comments from Stephen Wilde & Piers Corbyn (inc. Climate Fools Day News)
"In essence, the principle operates to shift the evidentiary burden of proof as to whether there is a threat of serious or irreversible environmental damage," he said.
"Where there is a reasonably certain threat of serious or irreversible damage, the precautionary principle is not needed and is not evoked . . .
"But where the threat is uncertain, past practice had been to defer taking preventative measures because of that uncertainty.
"The precautionary principle operates, when activated, to create an assumption that the threat is not uncertain but rather certain.
"Hence, if there is a threat of serious or irreversible environmental damage and there is the requisite degree of scientific uncertainty, the precautionary principle will be activated.
"A decision-maker must assume that the threat of serious or environmental damage is no longer uncertain but a reality. The burden of showing that this threat does not, in fact, exist or is negligible effectively reverts to the proponent of the project.
"If the burden is not discharged, the decision-maker proceeds on the basis that there is a threat of serious of irreversible environmental damage and determines what preventative measures ought be taken."
That the precautionary principle underlies the climate change debate demonstrates that the scientific evidence on which the case for man contributing to or causing climate change had "the requisite degree of uncertainty".
The precautionary principle having been activated, the decision-maker (the government in this debate) must assume that the threat of serious or irreversible environmental damage is certain, and the burden shifted to climate sceptics to prove as a fact that the threat does not exist.
In Australia, the climate sceptics have failed. No political party is arguing that the threat does not exist or is negligible. The only argument now, in accordance with the precautionary principle, is determining what preventative measures have to be taken to reduce emissions.
The government supports a carbon price, the opposition supports direct action.
Climate sceptics have lost the battle, which they could never really win, because the precautionary principle reversed the onus of proof. The only real chance the climate sceptics had of winning the debate was to challenge the fundamental principle on which the theory was based, the precautionary principle.
Senator Penny Wong's mantra "the science is certain" was unnecessary -- the effect of the precautionary principle is that the science supporting the theory does not have to be certain, but the case against the theory does.
Josephine Kelly is a Sydney barrister.