Human population growth

Last month, the growth of the world's population was widely debated in my class; so, we were asked to create a graph to predict future growth and to identify factors that affect that.

I guess that if population has increased hugely in the last years it's because of all the advances they've been made. Over the years, a shorter amount of time was required to double the population and it currently remains the same way: every time the period of time gets shorter. If we continue this way, things will turn the wrong way and we'll be in serious trouble...

(Horizontal access: time / vertical access: number of people in billions)

But what shall we do to prevent this from happening?