The rich can relax. We just need the poor world to cut emissions. By 125%

Well, at least that clears up the mystery. Over the past year I’ve been fretting over an intractable contradiction. The government has promised spectacular cuts in greenhouse gas emissions. It is also pushing through new roads and runways, approving coal-burning power stations, bailing out car manufacturers and ditching regulations for low-carbon homes. How can these policies be reconciled?

We will find out tomorrow, when it publishes a series of papers on carbon reduction. According to one person who has read the drafts, the new policies will include buying up to 50% of the reduction from abroad. If this is true, it means that the UK will not cut its greenhouse gases by 80% by 2050, as the government promised. It means it will cut them by 40%. Offsetting half our emissions (which means paying other countries to cut them on our behalf) makes a mockery of the government’s climate change programme.

The figure might have changed between the draft and final documents, but let’s take it at face value for the moment, to see what happens when rich nations offload their obligations. What I am about to explain is the simple mathematical reason why any large-scale programme of offsets is unjust, contradictory and ultimately impossible.

Guardian