Global warming is not a population problem. Many scientists say that we need to reduce greenhouse gas emissions by 80% by 2050. Even if people completely stopped having babies, not enough people would die of old age to reduce emissions by 80% by 2050. If we produce energy using zero emission technology, we would stop man made global warming regardless of population.
Overpopulation contributes to global warming by increasing the demand for electricity and consumer goods. There are now 7 billion people in the world. In the year 1800 the world population was 1 billion! Predictions suggest that we will be 8 billion before 2025, only a few years away!