Looking at the RCP8.5 scenario, I realised there is no climate feedback in the economic GDP model: a rising temperature does not seem to have an effect or limitation on the CO2 emissions.
This is the reported negative effect on GDP, according to Richard Tol (Richard S. J. Tol, The Economic Effects of Climate Change, Journal of Economic Perspectives — Volume 23, Number 2 — Spring 2009 — Pages 29–51, figure 1):
The funny thing is that even for Africa there still remains a net positive economic growth relative to 2005, comparable with the unabated world average!
So why limit CO2 emissions?
Update 11 June 2017:
link to excel document RCP85_GDP.xls