Entirely the wrong decision on climate change in Paris

What is so maddening about this climate change kerfluffle is that everyone, but everyone, seems to be determined to make the wrong decisions, entirely ignoring everything they are being told by the scientific consensus on the subject. There've been a number of reports chewing over what should be done, assuming that the case for doing anything has been made, and they all say much the same thing. That this decision just announced is wrong:

A new UN climate change deal is expected to commit the world to trying to limit global warming to 1.5C - despite warnings the target cannot be achieved because people will never vote for the costly policies it would require.

The highly ambitious goal would require such a radical shift to expensive green energy that it would be impossible in a democratic society, a leading academic warned last night. It would also require as-yet-untested technologies to extract carbon dioxide from the atmosphere, others said.

The point is explicitly made in the Stern Review.Our target, if target there is going to be, should not be any particular temperature nor even level of emissions. It should be the cost of whatever changes we make. This is simply very basic economic reasoning.

If there are to be damages in the future then sure, we should pay some amount now to avert those damages. But obviously, we should not spend more now than what those damages will be: to do so would just be making everyone, present and future, poorer for no very good reason. Thus the most important number we need to know is what is the cost of averting the damage.

To insist that some particular temperature goal, or even emissions number, should be met regardless of the cost of doing so is to invert this reasoning. And given that the original reasoning in Stern (the economic reasoning, whatever one thinks of the climate science underlying the issue) is correct in its logic, this makes setting a temperature or emissions target is just the wrong thing to be doing.

We'd be much more amenable to discussing the climate change issue if everyone wasn't so insistent on applying what we know, absolutely, is the wrong answer to it.