Quite a few comments on climate blogs recently have drawn attention to the precautionary principle and the validity of its application. Noticeably, the are often posted by individuals with a degree of ‘cynicism’ about AGW, (I wouldn’t want to suggest, necessarily, that this represents a ‘guided’ shift in ‘sceptic’ strategy, but…).
To be clear what we are talking about here, this is what Wikipedia gives as a definition. Simply put, the principle is that, if there is a belief that present action might cause future harm, but there is no scientific consensus on this, then prudence recommends that action is taken, any; the ‘just in case’ approach. The entry also points to the conclusion that, in the absence of consensus, the burden of proof lies with the agent of change.
But the precautionary principle is no longer an issue. It has become an irrelevant argument, thanks to the progress made in climate science and the observed changes in climate recently. This is because there is no longer a need to apply it. The application is only required in the absence of scientific consensus.
Therefore, someone who refers to this is leading readers to the underlying assumption that the case for AGW is still somehow undecided; that there is no scientific consensus on climate change.
If you choose to define consensus as the total agreement of all scientists, then any who challenge the scientific findings of the IPCC, or of the many papers published in the past few years, thereby nullify it. But consensus surely means something less extreme than this; it means a general agreement by a majority. There can be no question that the majority of climate scientists agree that global warming is happening, that it is not purely natural, and that CO2 plays a role in this. They may be wrong, but they do agree.
Therefore, there is no longer an ‘absence of scientific consensus’. Therefore, the precautionary principle no longer applies. The argument for action is no longer based on uncertainty about the causes of recent changes, but on the consequences of action or inaction, given the ‘agreed’ facts.
There is a complication, though. Some applications of the precautionary principle deal with issues arising from actions whose consequences are uncertain, or unknowable in advance. This means that certain geoengineering ideas still fall within the remit of the application of the principle, as how they might change the system is unclear; Paul Crutzen’s ‘sulphur-seeding’ suggestion is one such.
It is no longer necessary, though, to say ‘we should act because we think that not to act might be dangerous’; now, the argument should shift to questions of what to do, not whether: ‘we know that not to act will be dangerous, so we will act; what should we do?’
So, when someone suggests that your call for action on climate change is founded on the precautionary principle, put them right; it isn’t, not any longer.