It is clear from your comments that you know bugger all about nonlinear physics. “…pushing the system, possibly to the point of non-linearity” -it’s not a bloody guitar amplifier we are talking about here. The climate is chaotic - this means it is nonlinear by definition. This also means BY DEFINITION that there does not exist any simple linear relationships between CO2 and temperature or anything else. If you don’t understand, I suggest you go off and study it for 15 years and come back to me. And yet you feel happy to call people deniers and worse who try to bring these things to people’s attention…there was me thinking you were some sort of expert based on the general snippiness of your replies on this blog.

In any risk assessment it is necessary to weigh up severity of consequence against probability of occurrence. The average denialist, by refusing to accept that climate change is happening in the first place effectively insists that probability of occurrence is low. Others, of Lomborg’s ilk, believe the severity of consequence is low, even if the probability of occurrence is higher than the denialists choose to believe.

Both positions allow conservative ideologues to advocate do little-or-nothing policies, either for honest or dishonest reasons (presumed massive cost being an example of the former; a right wing ideological libertarian dislike of government being an example of the latter). The conclusion remains, therefore, that the economists who advocate minimal proactive intervention are either anti-science denialists, or believe the consequences of climate change to be limited, or some combination of both.

Nonetheless we do know, despite the nonsense and the cherry picking and the ‘scandals’, that the earth is warming and that the climate will change. It is, however, true that the future of such a complex system — climate change combined with impact on human civilisation — is inherently unpredictable. But it does not then follow that that unpredictability allows us to assume that pushing the system, possibly to the point of non-linearity, will have little consequence. That is simply short-sighted.

Still, as the probability of occurrence increases, the justification for not acting on the basis of not knowing the severity of consequence becomes more tenuous anyway. This is why the conservative economists attempt to pick holes in the predictive models of the real scientists to imply that the complex system is not being pushed into non-linearity in the first place - no big change, no major issue to resolve.

We know how climate and human civilisation coexist today so do we invest in trying to minimise the change in the system we have or do we take a chance that the effects of the change we know is happening won’t be as bad as some predict? Getting it wrong at the other end of this great experiment is surely vastly more expensive.

Even for an economist.

Bringing it all back home, Ireland will not meet its 20% emissions targets by 2020 anyway, at least according to the EPA report co-authored by your good self:

“Between 2013 and 2020, an average growth rate for all emissions of 1 per cent is projected. Ireland is not likely to meet its target under the EU agreements for 2020. Almost €600 million may need to be spent on permit imports in 2020.”

So given our fiscal problems, it’s good news for Ireland that the EU has temporarily abandoned a 30% target, as this would increase our own savings target beyond the 20% we can’t reach anyway?

A sort of locking in emissions reductions by locking in all the lovely unemployment and idle capital we have unexpectedly securred?

When dealing with humans, there is a lot more than just the pure science & economics to consider.

There was a difference between the unilateral target (20%) and the multilateral target (30%) so that the EU had something to put on the table in Copenhagen. If we now go for 30% anyway, the EU will go to Cancun with no room to negotiate on targets. We could only offer more money to match a counteroffer by the Americans and Chinese. Is that a wise position to be in?

Hedegaard argues that the 20% target was never an emissions target, but rather a spending target. The recession has cut emissions. If we spend the same amount of money as we would have had without the recession, we would reach 30% — according to Hedegaard who wisely did not back up this claim with any analysis. That’s not a justification in terms of the public good. It’s a politician defending her budget and power.

I would have thought reducing greenhouse emission by 20-30% would be hugely related to the Irish economy. Wrong again, I guess.