You misunderstood - the user wrote that the improvement probably won't continue due to climate change (which is expected to negatively impact developing countries more than developed).
The parents contention is that climate change will prevent these countries becoming first world/that it will interrupt their growth. I'm saying even without climate change they won't become first world. Certainly not on the timescale suggested. Now I agree, climate change won't help. But the reason CAR isn't (now or in 50 years) a first world country is not down to climate change, its because they don't have any of the myriad things needed to support that type of economy.
economists think in curves - starting from a low base it's very easy to improve fast, but the rate of improvement drops off as it nears the global average.
ecologists think in straight lines - the rate of improvement is x/year, so in 50 years the improvement will be 50x and they'll be richer than Sweden, who are only improving at (x/10)/year.