I believe the driving factor of climate change isn't total world population though; it's fossil fuel exhaust generated for energy. There's correlation with total population but not necessarily direct linkage; if there are fewer people, but each person is consuming 2.5x as much electricity as the generation before, we wouldn't expect to see the fossil fuel burn rate lower.
Climate change is not all about electricity or fossil fuels though. Agriculture also has a massive impact, because of deforestation to create more arable land or, overuse of fertilizers and other chemicals. And the need for more/better agriculture is definitely driven by the growing world population.
