From the blog of the excellent Daniel Hannan:

“What difference would it make if the European Union were to cut its carbon emissions by 30 rather than 20 per cent? To a single approximation, none. According to the International Energy Agency: “We estimate extending Europe’s plan to cut emissions from 20 to 30 percent would roughly equal China’s two-week gas output.”

Even the most passionate advocates of the new target didn’t try to claim that it would have had any meaningful environmental impact. Their argument, rather, was that the EU ought to “send a message”, to “show courage”, to “take a lead”. In other words, they saw the legislation as being essentially declamatory: a way to advertise the purity of your motives rather than a proportionate response to an identified problem.” Reference

This perfectly illustrates the irrationality and religiosity of the Left. Left-wing ideas are not concerned with solving problems in a rational and mature way. Rather they are puritanical, intended to show that one is a moral person whose heart is in the right place, and who is willing to sacrifice oneself for the glorious cause. It is the politics of the Grand Romantic Gesture, rather than a practical solution.

The actual outcome of the EU cutting its carbon emissions will be an acceleration of the transfer of EU manufacturing jobs to China. But the Left is economically illiterate, and doesn't consider things like that. Even if it did, it wouldn't care. The only thing that counts is moral and ideological purity.