Those are the economic models upon which the whole IPCC report is based. They’re the starting point, to give us the number of people, the technology they’ll be using, the size of the economy, to give us the emissions numbers that can then be plugged into the computer models of the climate scientists. Remember, this is the starting point. Also remember that all of these models depend upon there being no mitigation at all: no higher energy taxes, no tax or subsidy switches to low carbon, nothing.
OK, now look at the outcomes of those models for 2100. The A1 family, for example, essentially says that we let globalisation rip. The result is that population peaks and then declines to 7 billion. We eradicate poverty. Pretty good outcome in my book.
A2 is what Stern used. We retreat from the global economy to a series of regional ones. 15 billion people and no we don’t eradicate poverty.
B1 is again globalised but more concerned with equity than growth. Population as in A1, but at a lower and more equal standard of living.
B2 is like A2 (ie, regional) with the social concerns of B1 added. Population of 10 billion and lower standards of living than A1 and B1.
Now remember again, these are the models upon which the IPCC report is built. They’re not mine, they are the economics which underlies all of the climate change models.
It’s pretty clear that the best outcomes (depending upon whether you prefer growth in living standards or value equity more) are A1 and B1: both of which assume globalisation.
A1 is a pretty good outcome in my book too; this is why the UK Libertarian Party's "green" policies are based on that A1 scenario. Is this just business as usual? No: it needs active support for free trade, global cooperation and technology exchange.