Essentially, emissions under the Business As Usual scenario that so many global warming policies are hell-bent on preventing goes something like this:
Emissions nearly quadruple by 2095 with nearly all the growth in developing countries. Bear in mind that business as usual expects that the kind of efficiency gains we've been making so far continue - that's why the developed world is already forecast to stall emissions growth despite continuing economic growth.
That sets up a massive challenge for global warming policy that wants to cut emissions to 50 per cent of their levels now. In order to reach that 50 per cent target we would need to make a 15 gigatons of carbon per year cut to get the 2050 levels back down to the level we're at now. We would then need to make another 11 gigaton cut to reach the 50 per cent target. If you're after 60 per cent, as the British Government is, 80 per cent, as the Quality of Life policy group is, or the even stronger target the Lib Dems are aiming at things only get worse.
Cutting a gigaton of waste off what will already be vastly more efficient economies takes some doing. To get an idea of just what cutting a gigaton of carbon means see this table:
Once again, that's on top of expected "business as usual" efficiency gains. Doing any of these 26 times is utterly impractical without incomes taking a serious hit.
Perhaps you think that the developed world should be shouldering most of the work. You're prepared to see our income taking a kicking but don't want to deny the opportunity to develop to poor countries.
Even if you were to miraculously cut developed world emissions to zero, complete de-carbonisation, the developing countries would still need to cut their emissions by 9.5 gigatones, 46 per cent. Growth in poor countries will mean that the rich world just can't do all the work in cutting emissions. If your cut in developed world emissions is more realistic, two-thirds for example, then the developed countries would need to make a 74 per cent cut.
Without some kind of miracle technology you can only reduce emissions sufficiently by radically slashing incomes. There is just no way that the Chinese, or any other other big emitters, will possibly accept this. Cutting their long-term expected income in half, or more, is just not an option at all.
What does this mean for Britain? We already knew that our emissions weren't particularly important to global emissions growth. The UK just doesn't emit that much. Instead of actually changing anything by our actions we were supposed to be "leading". Showing others how it is done. That's pretty irrelevant now. Even if you were to, as some would like to, have the EU put massive trade sanctions on any country that doesn't sign up to our green agenda they're still not going to pay half of their long-term income for the right to trade with us. They certainly won't be shamed into it by Britain's selfless willingness to decimate its manufacturing sector.
Our response to the threat of climate change has to be based on the three sets of measures those of us on the free-market right have been advocating for some time now:
1) Technology - cutting emissions to the level Al Gore, Zac Goldsmith or even Chris Huhne would like isn't impossible. It just requires a miracle. Fortunately science has a history of providing what, to previous generations, would have seemed miracles. There are economical steps we can take that don't screw over our economy and might make such a miracle, or just an incremental technology that reduces our emissions a bit, more likely. Prizes for technological discovery, an alternative to patents that was very successful in encouraging important developments during the Industrial Revolution, are a good candidate that Jim Manzi proposed in a recent National Review article.
2) Adaptation - we can make sure our flood defences are in order, our crops will respond well to the new seasons and take other steps to prepare for the challenges of a warmer world. We can help poor countries do the same. This needn't be particularly expensive and we should avoid doing too much while we don't know precisely what we'll be adapting to but adaptation is clearly a central response to climate change under any sensible programme.
3) Resilience - Manzi put it well: "Wealth and technology are raw materials for options". The most important thing to do in order to be able to withstand an ecological crisis is make sure you're rich to start off with. Rich countries are so much better able to withstand the harms of global warming. If we screw up our economy in a vain attempt to avert climate change future generations will not thanks us.