I was just pointed to an article by Jane Galt from 1998 which puts some numbers into the discussion on CO2 reduction. This analysis should be required reading for anyone who is interested in CO2 growth since the industrial revolution.
I have linked before that it appears unlikely to achieve less than twice our current CO2 level in 2100, even if we aggressively try to curb emissions. Galt does the calculation the other way around: suppose the U.S. tried to go to 1950's levels of emissions (which, by the way, is still substantial). How much would GDP have to go down, assuming current efficiency levels?
The answer is in the following table:
That's right: it requires a reduction to 47% of the 1998 level of GDP per person, which is equivalent to the 1963 GDP per person. To go further and get to 1900's emission levels -- which she says is still a net positive -- you have to go down to 12%, which is 1913's standard of living.
Go read the whole article from the archives. The linked page has multiple articles; skip to the second one, the one that starts with "Demosthenes".