The countries with rapidly expanding populations are not the ones with significant per-capita carbon emissions.
High emissions come from a monetary economy with a requirement of profit. Soon each remaining part of the world outside that economy will be a part of it, because this is how the monetary economy expands: putting regions "outside" under it's control. I just don't understand how people are sanguine that "now" it's "fine" because the rapidly expanding populations are outside of regions with intensive economic development, because very soon they will be inside such regions, either because a capital-intensive region enveloped them (no more free sheep grazing on the meadow, etc) or because the need for money in some area of their lives drove them into a capital-intensive region (favelas, etc.).